Effect of postpartum body condition score change on the pregnancy outcomes of lactating Jersey cows inseminated at first service with sexed Jersey or conventional beef semen after a synchronized estrus versus a synchronized ovulation.

Our objective was to compare insemination rate and pregnancies per artificial insemination (P/AI) of lactating Jersey cows inseminated at first service with sexed Jersey or conventional beef semen after submission to a Double-Ovsynch protocol for timed artificial insemination (TAI) versus a protocol to synchronize estrus at similar days in milk (DIM) . Secondary objectives were to determine the effect of protocol synchrony and postpartum body condition score (BCS) change on P/AI. Lactating Jersey cows (n = 1,272) were allocated by odd vs. even ear tag number, which was randomly allocated within the herd, within parity and semen type for submission to a Double-Ovsynch protocol ( DO ; n = 707) or a protocol to synchronize estrus ( ED ; n = 565). All ED cows detected in estrus were inseminated ( EDAI ; n = 424) with undetected cows receiving TAI after an Ovsynch protocol ( EDTAI ; n = 141). There was a treatment by parity interaction on insemination rate with 100% of DO cows receiving TAI, but a tendency for fewer primiparous ED cows to be detected in estrus and AI than multiparous cows (69.5 ± 0.04 vs. 77.1 ± 0.02%, respectively). For cows inseminated with sexed Jersey or conventional beef semen, DO cows tended to have and had more P/AI than EDAI cows (sexed, 49.2 ± 0.03 vs. 43.6 ± 0.03%; beef, 64.2 ± 0.04 vs. 56.3 ± 0.05%, respectively) and had more P/AI than EDAI+EDTAI cows (sexed, 49.1 ± 0.03 vs. 40.6 ± 0.03%; beef, 65.5 ± 0.04 vs. 56.2 ± 0.04%, respectively). Overall, 29.1% of DO cows expressed estrus with 5.0 and 24.2% of cows detected in estrus ≥24 h before and at TAI, respectively, and there was no difference in P/AI 61 ± 4 d after AI based on expression of estrus at TAI. The synchronization rate was greater for DO than EDAI cows (92.1 ± 0.01 vs. 79.2 ± 0.02%, respectively); however, synchronized DO cows had more P/AI than synchronized EDAI cows (55.0 ± 0.02 vs. 49.2 ± 0.03%, respectively). There was an interaction between BCS change from 7 to 39 ± 2 DIM and treatment on P/AI 61 ± 4 d after AI with no difference between DO and EDAI cows that lost = 0.25 (49.8 ± 0.04 vs. 51.0 ± 0.05%, respectively) or maintained/gained (55.6 ± 0.04 vs. 50.8 ± 0.05%, respectively) BCS, but within cows that lost ≥0.5 BCS, DO cows had more P/AI than EDAI cows (54.1 ± 0.04 vs. 36.1 ± 0.04%, respectively). In conclusion, submission of lactating Jersey cows to a Double-Ovsynch protocol for first insemination increased insemination rate and fertility to first insemination compared with AI after a detected estrus regardless of semen type and expression of estrus, particularly for cows with excessive postpartum BCS loss.


INTRODUCTION
The rate at which lactating dairy cows become pregnant (21-d pregnancy rate) is determined by an interaction between the AI service rate and pregnancies per AI (P/AI).Current protocols for synchronization of ovulation in lactating dairy cows originated from the Ovsynch protocol (Pursley et al., 1995) which increased the AI service rate but yielded similar P/AI of cows inseminated after a detected estrus (Pursley et al., 1997).Modifications to the Ovsynch protocol since its inception (Pursley et al., 1995) have included optimizing the timing of insemination relative to induction of ovulation with GnRH treatment (Pursley et al., 1998, Brusveen et al., 2008) and inclusion of a second PGF 2α treatment 24 h after the first to ensure complete luteolysis (Carvalho et al., 2015;Wiltbank et al., 2015).In addition, incorporation of presynchronization strategies such as 2 PGF 2α treatments 14 d apart (i.e., Presynch-Ovysnch; Moreira et al., 2001;Navanukraw et al., 2004), PGF 2α treatment with GnRH treatment 2 d later (i.e., G6G; Bello et al., 2006), or presynchronization with an Ovsynch protocol (i.e., Double-Ovsynch; Souza et al., 2008) manipulate ovarian physiology to begin the Ovsynch protocol at an optimal stage of the estrous cycle (i.e., d 6 or 7; Vasconcelos et al., 1999) to increase P/AI and thereby the 21-d pregnancy rate.The Ovsynch protocol in conjunction with these modifications and presynchronization strategies are termed fertility programs because the AI service rate and P/AI are increased compared with insemination after a detected estrus (Fricke and Wiltbank, 2022).Adoption of fertility programs and improvements in periparturient management of lactating dairy cows (Middleton et al., 2019;Fricke et al., 2023) have been critical components in increasing reproductive performance over the past 2 decades (Fricke and Wiltbank, 2022) and have allowed for increased use of sexed and beef semen to inseminate lactating cows (Lauber et al., 2023).
Sexed and beef semen insemination strategies allow herds to precisely manage herd inventory by generating essential, genetically elite replacements with sexed semen and increased market value for non-replacements as beef x dairy crossbred calves.For herds with average or excellent reproductive performance (20 to 30% 21-d pregnancy rates), sexed and beef semen insemination strategies are profitable because sufficient replacements are produced while capitalizing on increased market values of beef x dairy crossbred calves (Cabrera, 2022).From 2019 to 2021, inseminations of US Holstein and Jersey females with sexed semen increased from 11.0 and 24.5% to 17.7 and 32.1%, respectively (Lauber et al., 2023).Concurrently, inseminations with beef semen of US Holstein and Jersey females increased from 18.2 and 11.4% to 26.1 and 21.2%, respectively (Lauber et al., 2023).Sexed dairy semen accounted for 49% of domestic US dairy semen sold in 2022 (NAAB, 2023).Further, domestic US beef semen sales overall increased by 332,000 straws in 2022, but this increase was driven by 457,000 more straws sold to dairy herds and fewer straws sold to beef herds (NAAB, 2023).
Dairy farmers preferentially select which populations of cows within their herds are inseminated with sexed, conventional, or beef semen based on parity and service number with differences among herds based on size (Lauber et al., 2023).In the US dairy industry, genomic testing continues to increase with a greater emphasis on the selection of health and fertility traits (Ma et al., 2019;VanRaden, 2020).Genomic predictions allow dairy farmers to selectively determine which populations within the herd should be culled or inseminated with sexed, conventional, or beef semen (VanRaden, 2020).Currently, there is interest in identifying subpopulations of cows based on inputs such as genomics, sensor data, and health incidences to predict subsequent reproductive performance to implement targeted reproductive management strategies (Giordano et al., 2022).In addition to prioritizing specific subpopulations to different semen types (Giordano et al., 2022;Lauber et al., 2023), research has been focused on targeted reproductive management strategies for first insemination prioritizing detection of estrus compared with submission to a synchronized ovulation protocol (Fricke et al., 2014;Rial et al., 2022).Dairy farmers pay a premium of 15 to $22 per straw for sexed semen (McCullock et al., 2013;Seidel, 2013) which only yields 80 to 84% relative fertility compared with conventional dairy semen in lactating dairy cows (Drake et al., 2020) despite the increased adoption and selective use of sexed semen within a herd.Further, comparisons made between AI after a detected estrus compared with timed AI (TAI) after a synchronized ovulation protocol has only been made with varying DIM (Chebel and Santos, 2010;Fricke et al., 2014;Rial et al., 2022) or similar DIM with all cows inseminated with conventional dairy semen (Santos et al., 2017).
Thus, our primary objective was to determine the insemination rate and P/AI of lactating Jersey cows inseminated for first insemination with sexed Jersey or conventional beef semen after submission to a Double-Ovsynch protocol for TAI compared with submission to a protocol to synchronize estrus prioritizing AI after a detected estrus at similar DIM.Secondary objectives were to determine the effect of expression of estrus for cows submitted to a Double-Ovsynch protocol and synchrony on P/AI and the effect of early postpartum BCS change on P/AI.We hypothesized that cows submitted to a Double-Ovsynch protocol for TAI at first insemination would have more P/AI than cows inseminated after synchronization of estrus regardless of semen type.Further, we hypothesized that cows submitted to a Double-Ovsynch protocol for first insemination would have more P/AI as postpartum BCS loss decreased than cows inseminated after a detected estrus regardless of expression of estrus and synchronization rate.
daily in a double 30-parallel parlor.Once daily, cows were fed a TMR consisting of corn and alfalfa silage, corn and soybean meal-based concentrates, and mineral and vitamin supplements to meet or exceed the minimum nutritional requirements for high-producing dairy cows (NRC, 2001).Cows had ad libitum access to feed and water.Primiparous and multiparous cows were housed in natural ventilated and natural and tunnel ventilated barns, respectively, in separate pens with sand-bedded free stalls.Heat abatement provided to cows included fans and sprinklers located within the pens and holding area of the parlor and soakers in the return lanes that automatically activated when the temperature within the barn exceeded 21°C.During the study, the overall herd mean daily milk yield was 26.4 kg/d with 5.4 and 4.0% fat and protein, respectively, for a mean daily ECM yield of 34.5 kg/d.

Experimental Treatments
Lactating Jersey cows (n = 1,373) at 42 ± 3 DIM (d 0) were allocated weekly by odd vs. even ear tag number, which was randomly allocated within the herd, within parity (primiparous vs. multiparous) and semen type (conventional beef vs. sexed Jersey) to 1 of 2 treatments for first insemination as described by Santos et al. (2017): 1) a Double-Ovsynch protocol (n = 707) or 2) a protocol to synchronize estrus (n = 565; Figure 1).The number of cows per treatment was unequal because of the number cows calving weekly with odd vs. even ear tag numbers.Cows were removed (n = 101, Double Ovsynch, n = 43; synchronized estrus, n = 58) from the data set if there was a lack of treatment compliance (n = 14, Double Ovsynch n = 4; synchronized estrus n = 10), if cows were sick during the AI eligibility period (n = 23, Double Ovsynch n = 8; synchronized estrus n = 15), they were sold (n = 24, Double Ovsynch n = 7; synchronized estrus n = 17), if they died (n = 10, Double Ovsynch n = 5; synchronized estrus n = 5), or if they were identified as do not breed (n = 8, Double Ovsynch n = 7; synchronized estrus n = 1), or if cows had a short estrous cycle after first insemination (n = 22, Double Ovsynch n = 12; synchronized estrus n = 10).Thus, a total of 1,272 cows were included in the final data set.
Briefly Cows submitted to a protocol to synchronize estrus (ED; n = 565) for first insemination with either sexed Jersey (n = 340) or conventional beef (n = 225) semen received GnRH treatment on d 3 with a PGF 2α treatment 7 d later (d 10).The GnRH treatment on d 3 was given to induce ovulation in anovular cows and increase cyclicity.Two weeks later, ED cows received 2 PGF 2α treatments given 24 h apart (d 24 and 25) exactly like the DO cows.All cows in the herd were painted with tail paint by an experienced AI technician employed by the commercial dairy farm for the first time upon leaving the post-fresh pen at approximately 21 to 30 DIM and repainted daily each morning.Pens were walked twice daily by the AI technician to detect cows in estrus based on rubbed tail paint.If detected in estrus, cows were inseminated approximately 12 h later.Synchronized estrus cows were inseminated based on detection of estrus 3 d before until 8 d after the PGF 2α treatment on d 24 deemed the AI eligibility period (EDAI; n = 424).If ED cows were not detected in estrus during the AI eligibility period, cows were evaluated for the absence or presence of a corpus luteum (CL) > 15 mm by transrectal palpation by the herd veterinarian.Based on the absence or presence of a CL, cows either receive GnRH treatment and begin an Ovsynch protocol 7 d later or to begin an Ovsynch protocol, respectively, for scheduled TAI (EDTAI; n = 141; Figure 1).
All hormonal treatments and inseminations were conducted by an experienced AI technician employed by the collaborating commercial dairy farm who was aware of treatment assignments to ensure the correct application of treatments.The selection of sires and semen types for first insemination of cows was determined by a genetic consultant using either a dairy wellness profit (DWP$, Zoetis) or herd health profit dollars (HHP$, Select Sires) index before cows were enrolled to treatments.Thus, cows were not randomized to semen type because cows were assigned to semen type based on genetic indices by a genetic consultant but were as-Lauber and Fricke: REPRODUCTIVE MANAGEMENT WITH SEXED OR BEEF SEMEN signed to treatments by odd vs. even ear tag number within a semen type using the herd management software.Sexed semen was produced from Jersey sires and was packaged at approximately 2.0 × 10 6 sperm per straw with ~90% accuracy of X-bearing sperm (Sexcel Sexed Genetics, ABS Global; gender SELECTED Ultraplus, Select Sires).Sexed semen was commercially processed using either commercialized microfluidics and selective laser-based cell destruction (Faust et al., 2016a,b;Sexcel Sexed Genetics, ABS Global) or flow cytometry and separation upon exposure to charged plates (Vishwanath and Moreno, 2018; gender SE-LECTED Ultraplus, Select Sires).Conventional beef semen was produced from crossbred beef sires and was packaged at approximately 20.0 × 10 6 sperm per straw (Beef InFocus, ABS Global).The allocation of conventional beef and sexed Jersey semen sires was equally distributed between treatments with 8 and 12 sires used for each semen type, respectively.

Serial Blood Sampling and Progesterone Assays
Serial blood samples were collected from all cows on d 24, 27, and 34 to determine plasma concentrations of progesterone (P4) and overall synchrony to the synchronization protocols (Figure 1).Blood samples (8 to 9 mL) were collected via puncture of the medial caudal blood vessels using evacuated K2-EDTA collection tubes (Vacutainer; Becton Dickinson and Co.).Samples were immediately placed on ice, and blood samples were centrifuged at 2,000 x g for 20 min at 4°C within 2 to 8 h after collection.Plasma was harvested and stored at −20°C.Plasma P4 concentrations were assayed using a commercial solid-phase RIA kit with antibody-coated tubes and 125 I-labeled P4 (ImmuChem Coated Tube Progesterone 125 I RIA kit; MP Biomedicals) that was validated for use with bovine plasma (Garbarino et al., 2004;Skenandore et al., 2017).To assess the precision of the assay, quality control samples were made from a pool of charcoal-stripped bovine serum spiked with P4 to a concentration of 2.0 ng/mL and stored at −20°C in aliquots.Quality control samples were repeated in triplicate at the beginning, middle, and end of the assay.All plasma samples were run as singlets across 17 assays.The average sensitivity for the assay was 0.09 ng/mL.The average intra-and interassay CV were 7.03 and 17.3%, respectively, based on quality control samples repeated within each assay.

Synchronization Rate
The effect of treatment and synchrony to the synchronization protocols on P/AI was assessed only for cows inseminated during the AI eligibility period with a complete set of blood samples.Synchrony to the treatments was defined as cows with high P4 (≥0.5 ng/mL) on d 24 and 34 and low P4 (<0.5 ng/mL) on d 27.Non-synchronized cows were removed in a stepwise manner to compare the P/AI of synchronized and non-synchronized cows at d 24, 27, and 34 between treatments using a similar methodology as previously described by Giordano et al. (2012) and Santos et al. (2017).

Pregnancy Diagnosis
Pregnancy was diagnosed at 34 ± 2 d after AI based on transrectal palpation by the herd veterinarian.Cows reinseminated based on detection of estrus before pregnancy diagnosis were considered nonpregnant.Pregnancy reconfirmation occurred at 61 ± 4 d after AI via transrectal palpation by the same veterinarian.Cows diagnosed pregnant at 34 ± 2 d after AI and diagnosed nonpregnant at 61 ± 4 d after AI were considered to have undergone pregnancy loss.

Body Condition Score Assessment and Milk Yield
Body condition score assessments were available on a subset of cows (n = 973) at 7 ± 2, 39 ± 2, and 69 ± 3 DIM using a 5-point scale with 0.25 increments where 1 = emaciated and 5 = obese (Ferguson et al., 1994).All BCS assessments were conducted by a trained member of the research team throughout the experiment.The change in BCS for each cow was determined from 7 to 39 ± 2 DIM, 39 ± 2 to 69 ± 3 DIM, and 7 ± 2 to 69 ± 3 DIM.Tertiles based on the BCS change from 7 to 39 ± 2 DIM were created for cows inseminated during the AI eligibility period (n = 865) in ascending order as follows: lost ≥0.5 (n = 319), lost = 0.25 (n = 291), and maintained/gained (n = 255) using the PROC RANK procedure of SAS.Mean daily milk yields (kg/d) for the 7 d before the PGF 2α treatment on d 24 for both treatments were used to calculate a mean daily milk yield (kg/d) for the week.Cows with no daily milk yield recorded for the entire week were excluded from the analyses (n = 5).If cows had daily milk yield, but not for the entire week, the mean daily milk yield for the week was calculated with the available daily milk yield (n = 8).Treatments, insemination records, P/AI, and milk yields were recorded in a cloud-based dairy herd management software (BoviSync) and data were collected and archived for subsequent analyses.

Statistical Analyses
All statistical analyses were performed using SAS computational software version 9.4 for Microsoft Windows (SAS Institute Inc., Cary, NC).A significant difference in the fixed effects was considered when P ≤ 0.05 and a statistical tendency when 0.10 ≥ P > 0.05.The experimental design was a completely randomized block design stratified by parity (primiparous vs. multiparous) and semen type (conventional beef vs. sexed Jersey).Based on an a priori power calculation using the POWER procedure of SAS, the inclusion of a minimum of 376 cows per treatment per semen type allowed for the detection of a 9-percentage point difference in P/AI (40 to 49%; 95% CI; 80% power; 1-sided test).An effect size of 9-percentage points was chosen based on a study with a similar experimental design that reported 10-percentage points more P/AI for synchronized Holstein cows inseminated with conventional dairy semen after submission to a Double Ovsynch protocol than a protocol to synchronize estrus (Santos et al., 2017).Further, Lauber et al. (2020) reported primiparous Holstein cows submitted to a Double-Ovsynch protocol inseminated with sexed semen had 48% P/AI 80 d after TAI.
Binary response data (i.e., insemination rate, P/AI, pregnancy loss, synchronization rate) were analyzed by logistic regression using the GLIMMIX procedure of SAS with separate logistic regression models for sexed Jersey and conventional beef semen for the binary outcomes of P/AI and pregnancy loss.Fixed effects included were treatment, parity, and the treatment x parity interaction with the effects of treatment and parity forced to remain the final model.The selection of the models that best fit the data for each variable of interest were performed by finding the models with the lowest value for the Akaike information criterion, using a backward elimination procedure that removed Lauber and Fricke: REPRODUCTIVE MANAGEMENT WITH SEXED OR BEEF SEMEN all variables with P > 0.10 from the model.The final models included the fixed effects of treatment and parity, except for the insemination rate which included the fixed effects of treatment, parity and their interaction in the final model.Further, the effect of BCS change tertile, treatment, and parity on P/AI was analyzed using logistic regression using the GLIMMIX procedure of SAS.Model selection occurred as previously described with the final models for P/AI including the fixed effects of treatment, parity, BCS change tertile, and the interaction of treatment and BCS change tertile.Further, the model for P/AI at 34 ± 2 d after AI also included the interaction of parity x BCS change tertile.All proportions within the text are reported as the LSM ± SEM using the LSMEANS statement of the GLIMMIX procedure of SAS.In the tables, proportions are presented as the arithmetic and LSM ± SEM proportions.
The distribution of DIM at AI and days to AI relative to PGF 2α treatment (d 24) were analyzed using the LO-GISTIC procedure of SAS with a model containing the fixed effects of treatment, parity, and their interaction.Final models were selected as previously described and included the fixed effects of treatment and parity.Continuous outcomes (i.e., DIM at AI, AI relative PGF 2α treatment, mean daily milk yield (kg/d) the week before PGF 2α treatment, BCS and BCS change for cows AI during the AI eligibility period) were determined by ANOVA using the MIXED procedures of SAS.Model selection occurred as previously described with the final models (DIM at AI, days to AI relative PGF 2α treatment (d 24), mean milk yield (kg/d) the week before PGF 2α treatment) including the fixed effects of treatment and parity.The final models for BCS and BCS change included the fixed effects of treatment, parity, and BCS change tertile except for BCS change from 7 to 39 ± 2 DIM which also included the interaction of parity x BCS change tertile.All means are presented as LSM ± SEM using the LSMEANS statement in SAS.

Effect of Treatment on Insemination Rate, Days to Insemination Relative to PGF 2α treatment (d 24), and DIM at Insemination
In the present study, detection of estrus occurred twice daily via visual observation of rubbed tail paint with 75.0% of ED cows detected in estrus and inseminated.There was a treatment x parity interaction (P < 0.0001) for insemination rate (Figure 2).By design, 100.0% of DO cows were inseminated regardless of parity.Fewer primiparous ED cows tended (P = 0.06) to be detected in estrus and inseminated than multipa-rous ED cows (Figure 2).Santos et al. (2017) reported no parity effect, but that more cows submitted to a Double-Ovsynch protocol were inseminated within 7 d after the voluntary waiting period than cows submitted to a protocol to synchronize estrus and inseminate after a detected estrus (100.0 vs. 77.5%,respectively).Sitko et al. (2019) reported that 72.0 to 75.8% of primiparous lactating Holstein cows were detected in estrus after PGF 2α treatment regardless of genetic merit for fertility.For reproductive management programs that prioritized detection of estrus, more primiparous than multiparous cows were inseminated based on detection of spontaneous estrus (75.3 vs. 64.7%,respectively) despite a greater proportion of multiparous than primiparous cows detected in estrus 21 to 49 DIM (Rial et al., 2022).This parity effect may be due to a greater prevalence of anovulation in primiparous cows (Gumen et al., 2003;Bamber et al., 2009;Monteiro et al., 2021).Regardless of detection of estrus method, insemination rates based on detection of estrus approach only about 70 to 80% (Valenza et al., 2012;Fricke et al., 2014;Rial et al., 2022) due to failure of cows to express estrus, failure to detect cows in estrus, and the presence of anovular cows.Thus, insemination rates based on detection of estrus are unable to achieve a 100% insemination and require submission of cows failing to be detected in estrus to a hormonal synchronization protocol for TAI.
The distribution of days to first insemination relative to PGF 2α treatment on d 24 differed by treatment (P < 0.0001; Figure 3, panel A), but not by parity (P = 0.23).Relative to PGF 2α treatment on d 24, EDAI cows were inseminated 0.95 ± 0.07 d later (P < 0.0001) than DO cows (3.86 ± 0.04 vs. 2.91 ± 0.05 d).Mean days to AI relative to PGF 2α treatment on d 24 did not differ between parities.The distribution of DIM at first insemination differed between treatments (P < 0.0001; Figure 3, panel B), and tended (P = 0.06) to differ between parities.The mean DIM at first insemination of DO cows was 1.0 ± 0.17 DIM later than EDAI cows (69.9 ± 0.12 vs. 68.9± 0.14 DIM, respectively) with a tendency (P = 0.06) for mean DIM to be greater for multiparous than for primiparous cows (69.6 ± 0.17 vs. 69.2± 0.10 DIM, respectively).Using a similar experimental design, Santos et al. (2017) found no difference in the mean or the distribution of DIM at first insemination between cows receiving TAI after a Double-Ovsynch protocol or AI after a detected estrus.The physiological effect of a 1 d difference at first insemination between treatments is likely minimal compared with studies reporting ≥11 d difference between detection of estrus and AI than TAI at first insemination (Pursley et al., 1997;Dolecheck et al., Lauber and Fricke: REPRODUCTIVE MANAGEMENT WITH SEXED OR BEEF SEMEN 2016) or TAI than detection of estrus and AI (Chebel and Santos, 2010;Fricke et al., 2014;Rial et al., 2022).

Effect of Treatment on Pregnancies per AI and Pregnancy Loss
For cows inseminated with sexed Jersey semen, there was a tendency for DO cows to have more P/AI at 34 ± 2 (P = 0.09) and 61 ± 4 (P = 0.08) d after AI than EDAI cows, respectively (Table 1).Interestingly, there was no parity effect on P/AI at 34 ± 2 (P = 0.24) or 61 ± 4 (P = 0.40) d after AI for cows inseminated with sexed semen.For cows inseminated with conventional beef semen, DO cows had more P/AI at 34 ± 2 and 61 ± 4 d after AI than EDAI cows, respectively (P = 0.04; Table 1).Further, primiparous cows inseminated with conventional beef semen had more P/AI at 34 ± 2 (75.3 ± 0.06 vs. 53.8± 0.03%; P = 0.001) and 61 ± 4 (68.4 ± 0.06 vs. 51.6 ± 0.03%; P = 0.009) d after AI than multiparous cows, respectively.Pregnancy loss did not differ between treatments for sexed Jersey or conventional beef semen (Table 1).In lactating Holstein cows inseminated with conventional dairy semen for first insemination, cows submitted to TAI after a Double Ovsynch protocol had 27% and 23% more P/AI 33 and 63 d after AI, respectively, than cows inseminated based on detection of estrus at a similar DIM (Santos et al., 2017).Thus, at a similar DIM and regardless of semen type, cows submitted to TAI after a Double-Ovsynch protocol not only had a greater insemination rate but had more P/AI than cows inseminated to a detected estrus.
Among all cows enrolled for first insemination, Santos et al. (2017) reported 64 and 58% more pregnant cows at 33 and 63 d after AI, respectively, for cows submitted to TAI after a Double-Ovsynch protocol than cows submitted to a protocol to synchronize estrus.Sitko et al. (2019) reported that primiparous lactating Holstein cows submitted to TAI after a Double-Ovsynch protocol had approximately 10 percentage points more P/AI than cows submitted to a protocol that prioritized detection of estrus and AI regardless of genetic merit for fertility.Lactating Holstein cows submitted to a Presynch-Ovsynch protocol without detection of estrus and 100% TAI had more P/AI than reproductive management programs that prioritized detection of estrus (Fricke et al., 2014).In a large meta-analysis, cows detected in estrus and inseminated after the second PGF 2α treatment in a Presynch-Ovsynch protocol before scheduled TAI had 35% decreased odds of pregnancy and as a reproductive management program had 10.8 percentage points fewer P/AI at 32 d than cows submitted to a Presynch-Ovsynch protocol with 100% TAI (Borchardt et al., 2016).Rial et al. (2022) reported approximately 7 percentage points more P/AI at first insemination with either sexed or beef semen when cows were submitted to TAI after a Double-Ovsynch protocol than cows submitted to reproductive management programs that prioritized detection of estrus.The proportion of cows pregnant at 150 (Rial et al., 2022) Lauber and Fricke: REPRODUCTIVE MANAGEMENT WITH SEXED OR BEEF SEMEN and 300 DIM (Fricke et al., 2014), however, did not differ between cows submitted to TAI after a fertility program or reproductive management programs that prioritized detection of estrus.
The relative fertility of sexed semen reported in a randomized controlled field trial was approximately 80 to 84% of that of conventional semen in lactating Irish Friesian cows (Drake et al., 2020).Primiparous Holstein cows submitted to TAI after a Double-Ovsynch protocol for first insemination using sexed semen had 48.0%P/AI 80 ± 17 d after TAI (Lauber et al., 2020).Drake et al. (2020) submitted lactating Irish Friesian cows to a modified Ovsynch protocol that included a P4 insert and randomized cows to semen type within split ejaculates.Cows inseminated with conventional semen had 12.1 percentage points more P/AI than cows inseminated with sexed semen (61.1 vs. 49.0%,respectively; Drake et al., 2020).At 74 ± 3 d after first insemination, Rial et al. (2022) reported an interaction between first insemination strategy and semen type with the most P/ AI for cows submitted to TAI after a Double-Ovsynch protocol with sexed (45.4%) or beef (43.9%) semen and cows inseminated with beef semen in a targeted reproductive management program that prioritized AI to a detected estrus (44.5%).Cows inseminated with beef (42.4%) rather than sexed (36.1%) semen for first insemination had more P/AI 74 ± 3 d after AI (Rial et al., 2022).It is important to recognize that under field conditions farmers allocate sexed and beef semen differentially based on parity, service number, and herd size (Lauber et al., 2023).Thus, comparisons of fertility between sexed and conventional semen are only valid within randomized-controlled studies such as those reported by Drake et al. (2020) and Chebel and Cunha (2020).Thus, the pregnancy outcomes presented in our study as well as others (Lauber et al., 2020;Rial et al., 2022) serve as references for those specific populations of cows selected for insemination with sexed or conventional semen under field conditions.

Effect of Expression of Estrus on Pregnancies per AI for Double-Ovsynch Cows
Overall, 29.1% of DO cows were detected in estrus from 3 d before PGF 2α treatment on d 24 (d 21) to scheduled TAI (d 27).Only 5.0% of DO cows were detected in estrus and inseminated ≥24 h before scheduled TAI yielding 37.1% P/AI at 61 ± 4 d after AI.Fricke et al. (2016) reported that 0.0 and 37.0% of Irish Frisian cows induced to either have high or low P4 during the Breeding-Ovsynch portion of a Double-Ovsynch protocol expressed estrus 24 h before TAI.Cows induced to have low P4 that were detected in estrus 24 h before TAI had larger follicles at the last GnRH treatment of the Double-Ovsynch protocol than cows with high P4 or with low P4 and not detected in estrus (Fricke et al., 2016).A likely mechanism for the decreased fertility Least squares means within a row and semen type (Sexed Jersey or Conventional beef) with different lowercase superscript letters differ (P ≤ 0.05).

A-B
Least squares means within a row and semen type (Sexed Jersey or Conventional beef) with different uppercase superscript letters tended to differ (0.05 < P < 0.10).(Laplacette et al., 2022).At d 34 ± 2 d after TAI, DO cows that expressed estrus at scheduled TAI had more (P = 0.03) P/AI than cows that did not express estrus (64.0 ± 0.04 vs. 54.6 ± 0.03%, respectively), but by 61 ± 4 d after TAI there was no difference (P = 0.13) in P/AI between DO cows based on expression of estrus (59.1 ± 0.04 vs. 52.4± 0.03%, respectively).Pregnancy loss did not differ (P = 0.15) for DO cows based on expression of estrus at scheduled TAI.Pereira et al. (2016) reported that cows submitted to an estradiol and P4-based synchronization protocol that expressed estrus at TAI had more P/AI and fewer pregnancy losses than cows that did not express estrus.Lactating Holstein cows fitted with automated activity monitor collars and submitted to an Ovsynch protocol had fewer P/AI when associated with low physical activity at TAI than for cows with medium or high physical activity at TAI (Borchardt et al., 2022).Interestingly, Guner et al. (2023) reported an interaction between parity and expression of estrus with no differences within expression of estrus between parities, whereas primiparous and multiparous cows that expressed estrus had more P/AI than cows that did not express estrus.Laplacette et al. (2022) reported an interaction between timing of induction of ovulation and AI in a Double-Ovsynch protocol with expression of estrus on P/AI.For cows with later induction of ovulation (72 h) and TAI (96 h), cows that expressed estrus had more P/AI than cows that did not express estrus (57.9 vs. 39.4%, respectively; Laplacette et al., 2022).With standard timing of induction of ovulation (56 h) and TAI (72 h), there was no difference in P/ AI for cows that did or did not express estrus (50.8 vs. 48.1%,respectively; Laplacette et al., 2022).
In several studies (Perieria et al., 2016;Borchardt et al., 2022;Guner et al., 2023), the effect of expression of estrus on P/AI was determined after submission of cows to an Ovsynch protocol that increases the AI service rate, but has similar fertility compared with detection of estrus (Pursley et al., 1997).The current study and Laplacette et al. (2022) determined the effect of expression of estrus on P/AI in a Double-Ovsynch protocol which increases both P/AI the AI service rate, but also compared with detection of estrus as demonstrated in our study and by Santos et al. (2017).Cerri et al. (2009) reported no difference in fertilization rate and the number of grade 1 and 2 embryos for cows submitted to a Double-Ovsynch protocol with or without treatment of estradiol cypionate 36 h before AI.Expression of estrus at scheduled TAI in a fertility program is likely not as critical because the preovulatory follicle is exposed to a high P4 environment after ovulation to the first GnRH treatment of the Breeding-Ovsynch portion of the Double-Ovsynch protocol (Giordano et al., 2013;Carvalho et al., 2015;Melo et al., 2018).The inclusion of a second PGF 2α treatment increases the proportion of cows with complete luteolysis (Carvalho et al., 2015;Wiltbank et al., 2015) thereby allowing for adequate uterine and oviductal exposure of estradiol for sperm transport (Hawk, 1983).Further, induction of ovulation with exogenous GnRH mitigates overexposure of an oocyte to LH pulses (Kinder et al., 1996;Revah and Butler, 1996).Further, timing of insemination relative to ovulation is more precisely controlled compared with AI after the onset of estrus (Valenza et al., 2012).Thus, expression of estrus at TAI in fertility programs is likely less important for fertility than other reproductive management protocols that do not regulate follicular development and hormonal milieu as precisely.

Effect of Treatment and Synchrony on Pregnancies per AI
On d 24, more (P = 0.01) EDAI cows had P4 < 0.5 ng/mL than DO cows (Table 3).Further, more (P = 0.03) primiparous cows had P4 < 0.5 ng/mL on d 24 than multiparous cows (7.7 ± 0.02 vs. 4.3 ± 0.01%, respectively).For cows with P4 < 0.5 ng/mL on d 24, DO cows had more (P = 0.04) P/AI at 61 ± 4 d after AI than EDAI cows (Table 3).Non-synchronized primiparous cows on d 24 had more (P = 0.004) P/AI 61 ± 4 d after AI than multiparous cows (64.3 ± 0.11 vs. 18.5 ± 0.07%, respectively).For cows with P4 ≥ 0.5 ng/mL considered to be synchronized, DO cows had more (P = 0.04) P/AI than EDAI cows 61 ± 4 d after AI (Table 3), but there was no difference (P = 0.34) based on parity.Similarly, cows with P4 ≥ 0.5 ng/mL submitted to a Double-Ovsynch protocol for TAI had approximately 10 percentage points more P/AI than cows AI after a detected estrus (Santos et al., 2017).Removing non-synchronized cows with P4 < 0.5 ng/mL on d 24, 2.3% of cows had P4 ≥ 0.5 ng/mL on d 27 with Lauber and Fricke: REPRODUCTIVE MANAGEMENT WITH SEXED OR BEEF SEMEN no difference based on treatment or parity (P = 0.38; Table 3).For cows with P4 ≥ 0.5 ng/mL on d 27, EDAI cows tended to have more (P = 0.07) P/AI 61 ± 4 d after AI than DO cows (Table 3); however, there was no parity effect.For cows with P4 < 0.5 ng/mL deemed to be synchronized, DO cows had more (P = 0.02) P/ AI than EDAI cows (Table 3).Further, there was no difference in P/AI for synchronized cows on d 27 based on parity (P = 0.37).Santos et al. (2017) reported that cows with P4 < 0.4 ng/mL at insemination considered to be synchronized submitted to a Double-Ovsynch protocol still had approximately 10 percentage points more P/AI than cows AI after a detected estrus.
Finally, non-synchronized cows on d 27, P4 ≥ 0.5 ng/mL, were removed to determine synchrony on d 34 and the effect of synchrony, treatment, and parity on P/AI.Blood sample collection on d 34 occurred 7 d after scheduled TAI for DO cows but varied from 3 to 14 d after AI for EDAI cows because blood samples were collected once weekly.The threshold of P4 ≥ 0.5 ng/mL was used rather than 1 ng/mL on d 34 to compensate for the variation in d after AI for EDAI cows.On d 34, more (P = 0.0002) EDAI than DO cows had P4 < 0.5 ng/mL and were therefore characterized as non-synchronized (Table 3).More EDAI cows were likely classified as non-synchronized on d 34 despite being detected in estrus and ovulating than DO cows because of the shorter sampling interval relative to AI for EDAI cows detected in estrus 5 to 7 d after PGF 2α treatment.The proportion of cows with P4 < 0.5 ng/mL on d 34 did not differ (P = 0.75) between primiparous and multiparous cows.Pregnancies per AI for non-synchronized cows on d 34, P4 < 0.5 ng/mL, did not differ between treatments (P = 0.97) or parities (P = 0.41; Table 3).For cows with P4 ≥ 0.5 ng/mL on d 34 that were considered synchronized, there was no difference (P = 0.42) between parities; however, DO cows had more (P = 0.04) P/AI 61 ± 4 d after AI than EDAI cows (Table 3).Santos et al. (2017) reported that for cows with P4 ≥ 1 ng/mL one week after insemination, cows submitted to a Double-Ovsynch protocol for TAI still had approximately 10 percentage points more P/AI than cows AI after a detected estrus.
Previously, differences in P/AI between reproductive management strategies have been largely attributed to differences in synchrony (Giordano et al., 2012; Lauber and Fricke: REPRODUCTIVE MANAGEMENT WITH SEXED OR BEEF SEMEN Least squared means within a row with different lowercase superscript letters differ (P ≤ 0.05). 2 Cows submitted to a protocol for synchronization of estrus (ED) and AI based on detection of estrus within the insemination eligibility period (EDAI).Lopes et al., 2013;Carvalho et al., 2014a).Santos et al. (2017) reported no difference in the synchronization rate (~85.0%) between cows submitted to a Double-Ovsynch protocol versus a protocol to synchronize estrus.Further, the approximately 10 percentage points more P/AI for cows submitted to a Double-Ovsynch protocol compared with AI after a synchronized estrus was not attributed to the synchronization rate but rather the physiological mechanisms produced by the hormonal manipulations during the Double-Ovsynch protocol (Santos et al., 2017).In the present study, 87.8% of cows were considered synchronized with no difference between primiparous and multiparous cows (P = 0.23), and more (P < 0.001) DO cows were classified as synchronized to the protocols than EDAI cows (Table 3).This difference in synchronization to the protocols may have been due to the variation in d after AI for EDAI cows on d 34.Overall, P/AI did not differ between treatments for non-synchronized cows (Table 3), however, primiparous cows tended to have more P/ AI 61 ± 4 d after AI than multiparous cows (39.8 ± 0.08 vs. 23.8 ± 0.04%, respectively).For synchronized cows, P/AI 61 ± 4 d after AI did not differ (P = 0.42) between primiparous and multiparous cows, however, synchronized DO cows had more (P = 0.04) P/AI than synchronized EDAI cows 61 ± 4 d after AI (Table 3).Despite that there were more synchronized DO than EDAI cows, DO cows had approximately 6 percentage points more P/AI than EDAI cows.Cerri et al. (2009) reported that more embryos from lactating dairy cows inseminated after a detected estrus were classified as degenerate compared with embryos from cows submitted to TAI after a Double-Ovsynch protocol.During a Double-Ovsynch protocol, the preovulatory follicle is exposed to a high P4 environment when cows ovulate to the first GnRH treatment of the Breeding-Ovsynch portion of the protocol (Giordano et al., 2013;Carvalho et al., 2015;Melo et al., 2018).Exposure to more P4 during growth of the preovulatory follicle decreases follicle size compared with follicles that develop in a low P4 environment (Martins et al., 2018).Cows that ovulate a medium-sized preovulatory follicle (15 to 19 mm) had more P/AI than cows with smaller or larger follicles (Souza et al., 2007).Treatment with exogenous GnRH to induce ovulation mitigates overexposure of an oocyte to LH pulses preventing premature meiotic resumption (Kinder et al., 1996;Revah and Butler, 1996) and timing of insemination relative to ovulation is more precisely controlled compared with AI after the onset of estrus (Valenza et al., 2012).Thus, while the overall synchronization rate did differ between treatments, the major contributor to differences in P/AI between DO and EDAI cows in the present study is the hormonal manipulations during the Double-Ovsynch protocol that optimize oocyte and embryo quality.
Not all cows lose BCS during the periparturient period; some cows maintain or gain BCS (Britt, 1992;Carvalho et al., 2014b;Barletta et al., 2017).Carvalho et al. (2014b) reported that cows submitted to a Double-Ovsynch protocol for TAI that lost BCS from calving to 21 DIM had 42.3 and 55.5 percentage points fewer P/AI than cows that maintained or gained BCS (22.8 Lauber and Fricke: REPRODUCTIVE MANAGEMENT WITH SEXED OR BEEF SEMEN vs. 36.0vs. 78.3%,respectively).Multiparous lactating dairy cows submitted to a modified Presynch-Ovsynch protocol for TAI that gained BCS during the periparturient period had more P/AI than cows that maintained or lost BCS (53.0 vs. 26.9 vs. 15.7%,respectively).The negative effect of BCS loss during the periparturient period on the fertility of lactating dairy cows has been termed the "Britt Hypothesis" after the initial proposal by Britt (1992).The relationship among reproductive performance, BCS change, and periparturient diseases has been further described as the "High Fertility Cycle" (Middleton et al., 2019;Fricke et al., 2023).Lactating dairy cows that become pregnant by 130 DIM have a shorter calving interval, thereby gaining less BCS during the current lactation and dry period and therefore calve at a lower BCS (2.75 to 3.00) than cows with longer calving intervals (Middleton et al., 2019;Fricke et al., 2023).Cows that calve at a lower BCS undergo minimal BCS loss, have fewer periparturient health incidences, more P/AI at first insemination, and fewer pregnancy losses thereby reinitiating the "High Fertility Cycle" by becoming pregnant by 130 DIM (Middleton et al., 2019;Fricke et al., 2023).

Potential Physiologic Mechanisms Related to BCS Change
To our knowledge, this is the first study to compare the effect of BCS change early postpartum in lactating dairy cows randomized for submission to TAI after a Double-Ovsynch protocol or AI after a synchronized estrus.There was a tendency (P = 0.09) for an interaction between parity and BCS change tertile on P/AI at 34 ± 2 after AI.Interestingly, there was an interaction between treatment and BCS change tertile on P/AI at 34 ± 2 (P = 0.04) and 61 ± 4 (P = 0.03) d after AI.Contrary to Carvalho et al. (2014b) and Barletta et al. (2017), there was no difference in P/AI 34 ± 2 or 61 ± 4 d after AI for DO cows regardless of BCS change from 7 to 39 ± 2 DIM (P > 0.05; Figure 4).Further, there was no difference (P > 0.05) in P/AI at 34 ± 2 or 61 ± 4 d after AI between DO and EDAI cows that lost = 0.25 or maintained/gained BCS (Figure 4).By contrast, those cows that lost ≥0.5 BCS, DO cows had more (P < 0.05) P/AI at 34 ± 2 or 61 ± 4 d after AI by approximately 15.0 and 17.0 percentage points, respectively, than EDAI cows (Figure 4).Thus, the overall treatment effect on P/AI in the present study was manifested only for cows in the BCS tertile that lost ≥0.5 BCS.Potential differences that could influence the association of BCS change early postpartum with P/AI after TAI among the present study and those reported by Carvalho et al. (2014b), and Barletta et al. (2017) include dairy cattle breed, farm management, treatment with recombinant bovine somatotropin (rbST), and the magnitude of BCS change.Barletta et al. (2017) worked with one commercial dairy farm, whereas Carvalho et al. (2014b) reported a farm effect on the association of BCS change from calving to 3 wk postpartum and P/AI.More cows on Farm 1 maintained BCS and similarly had no difference in P/ AI 70 d after TAI among cows that lost, maintained, or gained BCS (32.2 vs. 35.8 vs. 41.5%, respectively;Carvalho et al., 2014b).By contrast, Farm 2 had more cows that gained BCS and P/AI at 70 d after TAI differed substantially among cows that lost, maintained, or gained BCS (15.4 vs. 36.3 vs. 84.9%, respectively;Carvalho et al., 2014b).Farm management differences, irrespective of first service reproductive management Least squared means within a row with different lowercase superscript letters differ (P ≤ 0.05). 1 Cows were evaluated for BCS using a 5-point scale with 0.25 increments at 7 and 39 ± 2 DIM to determine the change in BCS and ranked into tertiles.
strategy, likely affect the magnitude of the association of BCS change and P/AI.A management strategy that participating farms in the studies by Carvalho et al. (2014b) and Barletta et al. (2017) implemented that was not used in the present study was treatment with rbST every 14 d from 63 or 83 ± 3 DIM until dry-off.Recombinant bovine somatotropin acts as a galactopoietic factor to partition nutrients more efficiently to the mammary gland through tissue-specific alterations in metabolic pathways and responses (Etherton and Bauman, 1998).Some of these alterations include decreased insulin stimulation of glucose metabolism and lipid synthesis in adipose tissue, decreased adipocyte hypertrophy, increased insulin-like growth factor 1 and insulin-like growth factor binding protein, increased systemic blood flow, and enhanced immune response (Etherton and Bauman, 1998).Lucy (2000) reported that lactating dairy cows treated with rbST potentially ovulate aged follicles because of an earlier emergence of a second-wave dominant follicle but concluded that nutrient partitioning and increased milk production likely have a greater effect on repro- ductive performance rather than an inherent effect of rbST.
Finally, cows enrolled in the studies by Barletta et al. (2017) and Carvalho et al. (2014b) were 100% or 49% multiparous cows, respectively.During the previous lactation, multiparous cows likely received rbST treatment until dry-off which would likely decrease the mean BCS of cows at dry-off, calving, post-calving, as well as change in BCS.Genetically some cows have greater BCS with minimal BCS loss, but management and environmental conditions that increase BCS at calving are associated with greater BCS loss (Dechow et al., 2002).Carvalho et al. (2014b) reported that only 7.3% of cows lost ≥0.5 BCS points early postpartum while 36.9% of cows in our study lost ≥0.5 (range of 0.5 to 1.25 BCS points).Further, the magnitude of BCS loss of cows from 7 to 21 DIM of 0.15 BCS points reported in Barletta et al. (2017) is less than the 0.59 and 0.25 BCS points in our study that lost ≥0.5 or lost = 0.25.The mean BCS at 21 DIM for cows that lost BCS was <2.75 BCS points in Carvalho et al. (2014b) and Barletta et al. (2017).Ribeiro et al. (2016) reported cows with low BCS (<3.0) at AI had fewer P/AI than cows with moderate BCS (≥3.0).The fewer P/AI of cows that lost BCS in these studies may be due to the extremely low BCS of cows near AI due to previous treatment with rbST.

Potential Mechanisms for the Effect of Treatment on Cows with Excessive BCS Loss
The associations of BCS change with reproductive performance (Carvalho et al., 2014b;Barletta et al., 2017;Middleton et al., 2019) and incidence of periparturient health incidences (Ribeiro et al., 2016;Barletta et al., 2017) are well described in observational studies, but are challenging to test in randomized-controlled experiments to discern a potential physiological mechanism.Carvalho et al. (2014b) reported cows with extreme weight loss (7.5%) during the first 3 wk postpartum had elevated serum nonesterified fatty acids (NEFA) concentrations and more poorer quality embryos compared with cows that gained, maintained, or slightly lost weight.Lactating dairy cows that experienced negative energy balance (NEB) early postpartum had differences in granulosa cell gene expression in the preovulatory follicle at the time of insemination related to responses to lipids and ketones, lipid catabolism, oxidative stress, immune function, and reactive oxygen species (Marei et al., 2022).Ruebel et al. (2022) identified 38 differentially expressed genes from metaphase II oocytes for cows that lost BCS early postpartum (4 upregulated and 34 downregulated) related to inflammatory response, mitochondrial membrane depolariza-tion, production of reactive oxygen species, fatty acid metabolism, and cytoplasmic organization in oocytes.It appears that serum lipid concentrations early postpartum, such as elevated NEFA concentrations, could cause lipotoxicity and alter the metabolic function of granulosa cells and the oocyte.Thus, a potential physiological mechanism by which excessive BCS loss is negatively associated with fertility is through compromised oocyte and embryo quality or both.
Lactating dairy cows with greater BCS loss during the first 30 DIM are associated with a longer interval to first ovulation (Beam and Butler, 1999).Resumption of ovulation is driven by increased LH pulses and appears to occur after the energy balance nadir (Beam and Butler, 1999).The frequency of LH pulses is positively correlated with energy balance and plasma leptin concentrations for lactating dairy cows 14 d postpartum (Kadokawa et al., 2006).In our study, differences in P/AI between DO and EDAI cows that lost ≥0.5 BCS may have occurred due to differences in GnRH and thereby LH secretion early postpartum upon enrollment into treatments potentially from indirect and direct action of leptin on kisspeptin neurons.Multiple exogenous GnRH treatments for DO cows enrolled in a Double-Ovsynch protocol may have rectified this physiologic condition.
Secretion of GnRH either in a pulsatile or surge manner requires stimulation from kisspeptin neurons located in the arcuate nucleus and preoptic area of the hypothalamus in ruminants (Goodman et al., 2007;Hassaneen et al., 2016).Adipocytes in white adipose tissue produce leptin which is a metabolic marker for adiposity in ruminants (Delavaud et al., 2000).Leptin does not appear to act directly on GnRH neurons because GnRH neurons have no leptin receptors (Quennell et al., 2009), whereas approximately 40% of murine kisspeptin neurons express leptin receptors (Smith et al., 2006).Indirectly, leptin may act on first-order neurons such as neuropeptide y/agouti-related peptide and proopiomelanocortin/cocaine and amphetamine-regulated transcript neurons which express leptin receptors and interact with kisspeptin neurons (De Bond and Smith, 2014).
Lactating dairy cows in NEB have increased NEFA concentrations which are negatively correlated with leptin concentrations (Block et al., 2001).Leptin concentrations in lactating dairy cows in NEB decrease postpartum and remain low at 8 wk postpartum (Block et al., 2001).By contrast, NEFA concentrations peak at approximately 3 wk postpartum and stabilize by approximately 8 wk postpartum (Block et al., 2001;Carvalho et al., 2014b).Liefers et al. (2003) reported that early postpartum lactating dairy cows in a positive energy balance had greater leptin concentrations Lauber and Fricke: REPRODUCTIVE MANAGEMENT WITH SEXED OR BEEF SEMEN than cows in NEB.In fasted ovariectomized beef cattle treated with estradiol implants, the hypothalamicgonadotropic axis is hypersensitized such that leptin treatment increased the magnitude of GnRH and LH pulses and increased basal secretion of LH (Zieba et al., 2005).Rasby et al. (1991) fed nonlactating Hereford cows to either lose weight and BCS (3.4; 1 to 9-point scale), maintain weight and BCS (5.3), or gain weight and BCS (7.1).Nonlactating Hereford cows that were fed to lose weight and BCS had greater concentrations of LH after exogenous GnRH treatment than cows that maintained or gained weight (Rasby et al., 1991).Further, in Hereford cows fed to a BCS of 3, 5, 6, or 7, maximum LH concentrations after exogenous GnRH treatment were negatively correlated with BCS, and Hereford cows with a BCS of 3 had the greatest GnRH concentration in the infundibular stalk-median eminence (Rasby et al., 1992).These studies (Rasby et al., 1991;Rasby et al., 1992;Zieba et al., 2005) describe this phenomenon in nonlactating, ovariectomized beef cows treated with estradiol implants, but this effect could be more detrimental during the homeorhetic shift to support lactation of a high-producing dairy cow (Bauman and Currie, 1980).Further research is needed to determine and develop a potential physiological model of the effects of BCS change early postpartum, reproductive management, and their interaction on fertility of lactating dairy cows.

CONCLUSIONS
In conclusion and in support of our primary hypothesis, submission of lactating Jersey cows to a Double-Ovsynch protocol increased the insemination rate and P/AI compared with AI after a synchronized estrus regardless of semen type.In support of our secondary hypothesis, cows submitted to a Double-Ovsynch protocol had more P/AI regardless of expression of estrus than EDAI cows regardless of synchronization rate.Interestingly, there was an interaction between early postpartum BCS change and treatment on pregnancy outcomes with cows submitted to a Double-Ovsynch protocol only having more P/AI compared with AI after a detected estrus for cows that lost ≥0.5 BCS.Further research is necessary to understand and determine a potential physiological mechanism for the effects of early postpartum BCS change, reproductive management, and their interaction on fertility of lactating dairy cows.Thus, submission of lactating dairy cows to a Double-Ovsynch protocol was a more effective strategy to maximize fertility to first insemination regardless of semen type and expression of estrus, particularly for cows with excessive BCS loss, compared with AI after a detected estrus.
Effect of postpartum body condition score change on the pregnancy outcomes of lactating Jersey cows inseminated at first service with sexed Jersey or conventional beef semen after a synchronized estrus versus a synchronized ovulation.M. R. Lauber 1 and P. M. Fricke1* , on d 0 cows submitted to a Double-Ovsynch protocol (DO; n = 707) received the first GnRH (86 µg i.m. gonadorelin; Fertagyl, Merck Animal Health) treatment of the Pre-Ovsynch portion of the Double-Ovsynch protocol with PGF 2α (500 µg i.m. cloprostenol; Estrumate, Merck Animal Health) treatment 7 d later (d 7) and GnRH treatment 3 d after PGF 2α treatment (d 10).One week later, DO cows received the first GnRH treatment (d 17) of the Breeding-Ovsynch portion of the Double-Ovsynch protocol with PGF 2α treatments 7 and 8 d later (d 24 and 25).The final GnRH treatment of the Breeding-Ovsynch portion of the Double-Ovsynch protocol was given 56 h after the first PGF 2α treatment followed by TAI 16 h later (d 27) with either sexed Jersey (n = 393) or conventional beef (n = 314) semen.Double-Ovsynch cows detected in estrus during the Breeding-Ovsynch portion of the Double-Ovsynch protocol ≥24 h before scheduled TAI were inseminated before scheduled TAI.A member of the research team evaluated the expression of estrus via rubbed tail paint (DETECT HER and MARK HER, Select Sires) for the remainder of DO cows at scheduled TAI.

Figure 1 .
Figure 1.Schematic diagram of treatments and serial blood sample collections.Lactating Jersey cows were randomized weekly at 42 ± 3 DIM (d 0) within parity (primiparous and multiparous) and semen type (conventional beef and sexed Jersey) for first insemination after submission to either a Double-Ovsynch (DO) protocol for timed artificial insemination (TAI) or a protocol to synchronize estrus (ED) with twice daily detection of estrus and AI (EDAI).For ED cows not detected in estrus from d 21 to 32, cows on d 32 were evaluated by the herd veterinarian and based on the absence or presence of a corpus luteum (CL) received GnRH treatment and began an Ovsynch protocol 7 d later or began an Ovsynch protocol, respectively, for scheduled TAI (EDTAI).Created with BioRender.com.

Figure 2 .
Figure 2. Effect of the interaction between treatment and parity on the proportion of lactating Jersey cows inseminated (P < 0.0001).Means with different uppercase letters (A-B) tended to differ (0.10 ≥ P > 0.05).DO = first insemination with conventional beef or sexed Jersey semen after submission to a Double-Ovsynch protocol; ED = first insemination with conventional beef or sexed Jersey semen based on detection of estrus after submission to a protocol to synchronized estrus.

Figure 3 .
Figure 3.Effect of treatment on the proportion of lactating Jersey cows inseminated relative to PGF 2α treatment on d 24 (0; Panel A) and DIM at insemination (Panel B).DO = first insemination with conventional beef or sexed Jersey semen after submission to a Double-Ovsynch protocol; EDAI = first insemination with conventional beef or sexed Jersey semen based on detection of estrus after submission to a protocol to synchronize estrus.

1
Semen type mated to cows by the farm and AI for the first insemination of lactating Jersey cows.2Cows submitted to protocol for synchronization of estrus (ED) and AI based on detection of estrus within the insemination eligibility period (EDAI).

Figure 4 .
Figure 4. Effect of the interaction between treatment and BCS change tertile (Lost ≥0.5; Lost = 0.25; Maintained/Gained) from 7 and 39 ± 2 DIM on pregnancies per AI (P/AI) 34 ± 2 and 61 ± 4 d after AI for lactating Jersey cows (P < 0.05).Within each day from AI, means with different lowercase letters (a-b) differed (P ≤ 0.05).DO = first insemination with conventional beef or sexed Jersey semen after submission to a Double-Ovsynch protocol; EDAI = first insemination with conventional beef or sexed Jersey semen based on detection of estrus after submission to a protocol to synchronize estrus.

Table 1 .
Lauber and Fricke: REPRODUCTIVE MANAGEMENT WITH SEXED OR BEEF SEMEN Effect of treatment on pregnancies per AI (P/AI) 34 ± 2 and 61 ± 4 d after insemination and pregnancy loss for lactating Jersey cows inseminated with either sexed Jersey or conventional beef semen within the insemination eligibility period

Table 2 .
Effect of treatment on pregnancies per AI (P/AI) 34 ± 2 and 61 ± 4 d after insemination and pregnancy loss for lactating Jersey cows inseminated with either sexed Jersey or conventional beef semen a-b Least squares means within a row and semen type (Sexed Jersey or Conventional beef) with different lowercase superscript letters differ (P ≤ 0.05).1Sementypemated to cows by the farm and AI for the first insemination of lactating Jersey cows.2Cows submitted to a protocol for synchronization of estrus (ED) detected in estrus and AI (EDAI) and cows not detected in estrus within the insemination eligibility period receiving TAI after an Ovsynch protocol (EDTAI).

Table 3 .
Effect of treatment on the percentage of synchronized cows and the effect of synchrony on pregnancies per AI (P/AI) 61 ± 4 d after AI in lactating Jersey cows

Table 4 .
Lauber and Fricke: REPRODUCTIVE MANAGEMENT WITH SEXED OR BEEF SEMEN Least squared means (LSM ± SEM) BCS, BCS change, and daily milk yield (kg/d) the week before PGF 2α treatment (d 24) of lactating Jersey cows inseminated during the insemination eligibility period based on BCS change from 7 to 39 ± 2 DIM tertiles