The impact of beef sire breed on dystocia, stillbirth, gestation length, health, and lactation performance of cows that carry beef × dairy calves

In the United States, it is becoming common for dairy herds to mate a portion of cows to beef semen to create a value-added calf. The objectives of this study were to determine if dystocia risk, stillbirth (SB) risk, gestation length (GL), probability of early-lactation clinical disease events, early-lactation culling risk, or subsequent milk production differ between cows that carried calves sired by different beef breeds and those that carried Holstein-sired calves. Records from 10 herds contained 75,256 lactations from 39,249 cows that had calves with known Holstein or beef breed sires from the years 2010 to 2023. Calf sire breeds with ≥150 records included in analyses were Holstein, Angus, Simmental, Limousin, crossbred beef, and Charolais. Additional beef sire breeds that existed in lower frequency (n < 150 records) were condensed together and classified as “other.” Because GL is a continuous variable, sire breed inclusion criteria were reduced to n ≥ 100 records; thus, Wagyu sires were included as their own breed group. Some records did not contain all variables of interest, thus models included fewer lactations depending on variable. Binomial generalized mixed models evaluated dystocia risk (defined as calving ease score ≥4 or calving ease score ≥3), SB risk, clinical health event risk (defined as lameness, mastitis, metabolic, reproductive, other, or any health events occurring within 60 d in milk [DIM]), and early culling risk (defined as death or culling within 60 DIM). Gestation length and test-date milk, fat, and protein yields were evaluated with mixed models. Calves sired by crossbred beef bulls had a greater probability of being stillborn (5%; 95% confidence interval lower = 2.9% upper = 9.0%) than those sired by Holstein bulls (2%; 95% confidence interval lower = 1.5%, upper = 2.7%). All beef-sired calves increased GL from that of Holstein-sired calves (277 ± 0.15 d) with Limousin (282 ± 0.81 d) and Wagyu-sired calves (285 d ± 0.79) resulting in the longest GL. The risk of dystocia, clinical health events, and early-lactation culling did not differ by calf sire breed nor did subsequent milk and component yield. Generally, carrying a calf sired by the beef breeds included in this study did not negatively affect the dairy cow.


INTRODUCTION
The practice of mating a portion of the dairy herd to beef semen to increase the value of surplus calves has been growing in North American dairy herds in recent years (Basiel and Felix, 2022).It has been demonstrated that herds with average or better reproductive performance can maximize profitability by producing replacement females with sexed semen and mating the remainder of the dairy herd to beef semen because beef × dairy calves have greater value than purebred dairy bull calves (De Vries, 2020;Wilson et al., 2020;Cabrera, 2022;McCabe et al., 2022).However, the additional value of beef × dairy calves could be nullified for dairy producers if such calves negatively affected the health and production of the cows carrying beef × dairy calves.
Both historical and international data suggest that rates of dystocia increase in dairy cows mated to certain breeds of beef sires (Bech Andersen et al., 1977;Everitt et al., 1978;Fouz et al., 2013;Eriksson et al., 2020).In the United States, dairy producers report dystocia using the National Association of Animal Breeds (NAAB) calving ease (CE) scoring system (Berger, 1994).A CE score of 1 indicates no problem, a score of 2 indicates slight problem, a score of 3 indicates assistance needed, a score of 4 indicates considerable force needed, and a score of 5 indicates extreme difficulty (Berger, 1994).Dairy cattle genetic evaluations in the US define dystocia as a CE score of ≥4 (CDCB, 2022).Dystocia is associated with increased rates of stillbirth (SB), which is defined as a calf born dead or a calf born alive that died within 48 h (Meyer et al., 2000).Additionally, gestation length (GL) can influence dystocia and stillbirth incidence; when GL deviates from average, either longer or shorter, SB and dystocia incidences increase (Meyer et al., 2000;Norman et al., 2011).Dystocia can be costly because it increases the risk of postpartum disease and subsequently results in reduced milk, fat, and protein yields over the lactation (Dematawewa and Berger, 1997).Clinical cases of common diseases in dairy cows are estimated to cost from $145 to $400 per case because of treatment costs and production losses (Van Saun and Sniffen, 2014).Further, cows that experience clinical disease have reduced first service pregnancy rates and greater early-pregnancy losses than their healthy counterparts (Santos et al., 2010).
Calving ease is being emphasized in selection criteria developed by genetic companies and breed associations promoting sires to use in beef × dairy matings in the United States (Miller et al., 2021).However, modern data are needed to determine if North American beef sires increase dystocia incidence or negatively affect the health and performance of the dairy cow.Both beef and dairy breeds have made substantial genetic progress since the historic data on CE was collected, and international beef cattle genetics can vary immensely from those in the United States because of differing consumer preferences.
Current data on the influence of beef breed sires chosen for the North American dairy cow are limited; existing studies have quantified risk factors related to dystocia, such as GL, SB, and incidence of certain clinical health events (Scanavez and Mendonça, 2018;Foraker et al., 2022).Existing data are limited to single herds and may be associated with specific management practices rather than the beef sire used (Scanavez and Mendonça, 2018;Foraker et al., 2022).
Therefore, this study is focused on harnessing farm records from multiple US dairy herds to determine if GL, SB risk, and dystocia risk differed in cows that carried calves sired by different beef breeds or Holstein sires.Additional objectives were to determine if having a calf sired by certain beef breeds influences clinical health event risk, early-lactation culling rate, or subsequent milk and component production.

Data Acquisition and Management
This research was approved by the Pennsylvania State University Institution Animal Care and Use Committee (protocol #202102091).Data backups of farm management records recorded in commercial software (BoviSync [Fond du Lac, WI], Dairy Comp 305 [Visalia, CA], or PCDart [Raleigh, NC]) were obtained from 10 dairy herds located in the Northeast or Midwest regions of the United States.Herd sizes ranged from about 100 to 13,000 milking cows.All herds milked primarily Holstein cows and were mating a portion of their cows to beef semen for at least a year.
Sire breed of calf carried was identified by NAAB uniform breed code (NAAB, 2023a).Because the herds included in analyses were composed of primarily Holstein cows, calves sired by dairy breeds other than Holstein represented a nominal proportion of total records; lactation records of these calvings from other dairy sire breeds were excluded from analyses.Additionally, any records of cows that were culled or died before 2018 were removed because the initial increase in beef × dairy matings began that year; therefore, the likelihood they would be mated to beef semen was low (NAAB, 2023b).Lactations before 2018 from cows that were culled or died following 2018 were included so that older cows could be compared with their previous lactations.Following data cleaning, a total of 75,256 lactations from 39,249 cows that had calves with known sires from the years 2010 to 2023 were available.Table 1 displays the number of lactations initiated by calf sire breed and the number of sires in each breed group.In analyses, beef sire breeds that had less than 150 records were classified as "other" and included Wagyu, Hereford, Red Angus, Brahman, Red Brahman, and Shorthorn.It should be noted that sires classified as Simmental also included SimAngus sires, a composite breed of Simmental and Angus, and sires classified as Limousin included Lim-Flex sires, a composite breed of Limousin and Angus, because the breeds are classified under the same NAAB uniform breed code.Further, some of the individual sires counted in the crossbred beef breed may have produced progeny from multiple different sires due to a specific bull stud that markets pooled semen from multiple crossbred beef bulls.

Dystocia, SB, and GL
For models of dystocia, SB, and GL, lactations where the dam had multiple calves were removed as twinning can be a confounding factor for these parameters.In GL and dystocia models, SB incidences were removed to avoid confounding.Descriptive statistics of dystocia, SB, and GL data are presented in Table 2.
Dystocia was quantified by the NAAB CE score system defined in the "Introduction" section (Berger, 1994).Three herds were excluded from CE models because they did not have variation in CE score (i.e., only recorded scores of 1).A total of 24,398 records of CE were included from 7 herds.Dystocia was defined as a CE score of ≥4 to reflect the way US national genetic evaluations of dairy cattle define dystocia.However, using this definition <1% of calvings were dystocic (Table 2), thus a secondary model of dystocia was evaluated where dystocia was considered at a CE score of ≥3 in attempt to capture more variation between sire breeds.Some herds that were mating with conventional beef semen recorded all calves destined to leave the herd as male, regardless of phenotypic sex.In that scenario, calf sex was categorized as "undefined."Additionally, some records did not include calf sex, thus those calvings were also labeled "undefined."An additional dataset excluding herds that defined all beef × dairy calves resulting from conventional beef semen matings as male was also modeled.That dataset included 17,008 records of CE score available from 4 herds.Excluding herds from the data resulted in a greatly reduced frequency of Charolais and Limousin-sired calvings, therefore those records were condensed into the other sire breed category.
A calf was considered SB if the producer recorded it dead at birth or dead within 48 h of birth (Meyer et al., 2000).A total of 31,393 calving records were available that included all information required to model SB.Gestation length was calculated as the difference of calving date and last breeding date of the previous lactation.Records where GL was less than 254 d or greater than 300 d were excluded from analyses as they likely reflected an incorrectly recorded breeding date or abortion.This resulted in a total of 30,782 records of GL.Because GL is a continuous variable, inclusion of beef sire breeds condensed in the other category was relaxed to >100 calvings.Thus, Wagyu was included as a separate calf sire breed in GL analyses.
In the dataset that excluded herds that did not appropriately define sex of beef × dairy calves there were 20,661 records of SB and 20,304 records of GL from 6 herds.Records that appropriately defined sex resulted in fewer than 100 of Charolais and Limousin-sired, and, in the case of GL, Wagyu-sired calvings, thus they were condensed into the other sire breed category.

Clinical Health Events and DHIA Test-Date Production
Lifetime health event records from 52,116 lactations were available from 9 herds.Producer-recorded clinical health events were categorized as reproductive, metabolic, mastitis, lameness, other, and any (Table 3).Health events categorized as "other" encompassed any other health event that did not fit in the previous categories, whereas events categorized as "any" encompassed the occurrence of any clinical health event as a way to compare diseased and healthy cows.Health events were assessed for the first 60 DIM.Any records of lactations that were current to the time of data extraction where a living cow had yet to reach 60 DIM were excluded from the clinical health event assessment, even if a clinical health event already occurred, because she did not have the full opportunity to experience possible health events during early lactation.However, cows that died or were culled before reaching 60 DIM were included to account for any health events that may have contributed to their leaving the herd.
Early culling rate was defined as an animal dying or leaving the herd before 60 DIM.A total of 12,123 records were evaluated of animals that died or were culled during a lactation.By evaluating the incidence of animals that died or were culled in early lactation (within 60 DIM) among all animals that died or were culled in a lactation, we can quantify the proportion of animals that left the herd before they had the chance to reach peak production.Prevalence of clinical health events, by category, and early culling are presented in Table 3.
Only multiparous cows were included in health data so that occurrence of health events within the same category within 60 DIM of the previous lactation could be included as a covariate when modeling.Very few primiparous cows (<3%) had beef-sired calves, because most beef × dairy mating strategies recommend mating heifers to sexed dairy semen, so little data were lost by excluding primiparous cows.Similarly, only multipa-rous cows were included in the early culling data so that the previous lactation's 305-d mature equivalent milk production could be included as a model covariate to account for the potential that low-producing cows were more likely to be culled.
Because data were producer recorded, definitions of health events may have varied by herd.Categorization of health events is intended to broadly capture the type of event that occurs regardless of definition variation.Previously, Parker Gaddis et al. (2012) demonstrated that US dairy producer-recorded health events could plausibly be combined across herds and reflect similar frequencies to that reported in controlled studies.
Descriptive statistics of test-date production data are presented in Table 4.A total of 263,189 test-date milk production records were available from 30,991 lactations of 16,594 individual cows.There were 219,209 records of fat yield and 219,213 records of protein yield.One of the herds included in the study did not conduct DHIA testing, therefore test-date production was available from 9 herds.

Statistical Analysis
All analyses were performed using EchidnaMMS (version 1.76;Gilmour, 2021).Binomial generalized linear mixed models with a logit link function evaluated liability to dystocia (CE ≥4 and CE ≥3) and SB: where p = the probability of y ijklmn = 1, where y = CE ≥4, CE ≥3, or SB; µ = model intercept; SSB = breed of calf sire at lactation initiation i (Angus, Charolais, Gestation length was evaluated with a linear mixed model including the same model effects as SB and dystocia incidence.However, a greater number of records were available for GL, adding an eighth calf sire breed, Wagyu, to the analysis.The same models of SB incidence, dystocia incidence, and GL were also run excluding herds that did not define sex of calves leaving the herd where sex = heifer or bull. Binomial generalized linear mixed models with a logit link function evaluated liability to early-lactation health events: Model effects were tested by conditional Wald F statistic.Because no interactions were modeled, all model effects were conditional on all other model terms.Least squares means differences between calf sire breeds of continuous models were determined using Tukey critical values.Binomial models output least squares posterior quasi-likelihood estimates which were backtransformed to odds ratio probabilities using inverse logit.To generate 95% confidence intervals for binomial model estimates, standard error estimates were doubled, then added (upper 95%) or subtracted (lower 95%) from the least squares posterior quasi-likelihood estimate, then back-transformed to odds ratio probabilities using inverse logit.Differences were considered significant when P < 0.05.

RESULTS
The results of the SB, dystocia, and GL models that excluded herds that recorded all beef × dairy calves as male, regardless of phenotypic sex, were similar to the models that included those herds.The model solutions of both datasets for the variable calf sex are reported in Table 5. Stillbirth incidence, dystocia incidence, and GL were all reduced when a cow had a female calf, in both the dataset that excluded herds that incorrectly sexed beef × dairy calves and the set that included such herds.By including additional herds, variation around the regression solution of female calves was reduced but the solution estimates for the undefined sex category had substantial variation because both male and female calves were included.Henceforth, the results of the models that included all herds and the third sex categorization of undefined will be presented.
The probabilities of SB and dystocia by sire breed are presented in Table 6.Calf sire breed influenced SB probability (P = 0.01).The probability that Holsteinsired calves were stillborn was 2%, whereas the probability that calves sired by crossbred beef bulls were SB was 5%.There were no differences in the likelihood of SB among calves sired by other beef breeds evaluated (P > 0.05).Calf sire breed did not influence the probability of dystocia incidence when defined as CE ≥4 or CE ≥3 (P > 0.05).
The back-transformed early-lactation health event and culling probabilities by sire breed are presented in Table 7. Calf sire breed did not influence the risk of lameness, mastitis, or other health events in multiparous cows during the first 60 DIM (P > 0.05).The probability of reproductive, metabolic, and any health event occurring tended to be affected by calf sire breed (P < 0.10).However, following Tukey-adjustment the risk of reproductive, metabolic, and any health events did not differ by calf sire breed.The risk of cows leaving the herd within the first 60 DIM as opposed to later in their lactations did not differ by the sire breed of the calf they delivered at the onset of their lactation (P > 0.05).
Test-date milk, fat, and protein yield did not differ by calf sire breed (P > 0.05; Table 8).

Stillbirth, Dystocia, and GL
The risk of calves sired by crossbred beef bulls being SB was greater than that of Holstein-sired calves, while SB risk did not differ for calves sired by other beef breeds included in these data.Existing literature regarding SB rates from beef × dairy matings is variable.It was previously reported that, in a single herd, fewer instances of SB occurred in Holstein and Holstein × Jersey cows mated to Holstein and Jersey sires (0.9% and 2.4%, respectively) compared with those mated to Angus sires (7.6%; Scanavez and Mendonça, 2018).In contrast, multiparous Swedish Red cows mated to Angus, Charolais, Hereford, Limousin, and Simmental sires had 1.1% to 1.5% fewer incidences of SB than those mated to Swedish Red bulls (Eriksson et al., 2020).Primiparous Swedish Red cows mated to Angus bulls had 2.2% fewer SB occurrences than primiparous cows mated to other sire breeds (Eriksson et al., 2020).In addition, primiparous Swedish Holsteins had 3.9%, 3.3%, and 2.2% fewer incidences of SB when mated to Angus, Hereford, or Limousin sires, respectively, than those mated to Swedish Holsteins (Eriksson et al., 2020).Multiparous Swedish Holsteins mated to any beef breed but Angus had from 0.4% to 1% fewer stillbirths than those mated to Swedish Holstein bulls (Eriksson et al., 2020).In this study, SB incidence did not differ between Angus, Charolais, Limousin, Simmental, and Holstein-sired calves.A smaller study of records from 2 dairy herds similarly identified no differences in SB incidence between cows that carried Angus and Simmental-sired calves and those that carried Holsteinsired calves (Foraker et al., 2022).
The increased SB frequencies in Angus-sired matings observed by Scanavez and Mendonça (2018) may be related to herd-level selection biases because data were sourced from a single herd.Multiple recessive haplotypes associated with fertility and SB have been identified in the Holstein breed (VanRaden et al., 2011).More recently, a haplotype has been identified in Nordic Red dairy cattle that is related to SB (Wu et al., 2020).As such, the higher SB rates observed for purebred Swedish Red and Swedish Holstein calves may have been related to lethal recessive disorders.The records in the Swedish analyses were from the years 1997 to 2016; information on haplotypes associated  5. Model solutions for the effect of calf sex from the stillbirth, dystocia, and gestation length models that excluded herds which incorrectly identified all beef × dairy calves as male and from the models that included such herds and included a third sex of "undefined" to encompass the incorrectly sexed calves and any records missing calf sex with SB was not widely available until the end of that period, while most of the records included in our data were from after 2018.Therefore, it is possible that the lack of differences in probability of SB detected in our data is due to producers making more informed decisions around harmful haplotypes or genetics companies reducing the marketing and semen distribution from such bulls.The increased risk of SB in calves sired by crossbred beef bulls has, to our knowledge, not previously been reported.Calves sired by crossbred beef bulls were carried for 2 d longer than Holstein-sired calves.It is understood that, in Holsteins, GL that deviate significantly from the average are associated with increased rates of SB (Meyer et al., 2000).Thus, the greater probability of SB calves sired by crossbred beef bulls may, in part, be attributed to the greater GL.However, all beef sire breeds caused increased GL, some to a greater extent than crossbred beef sires.Additionally, no increased probability of dystocia was observed in calves sired by crossbred beef bulls though dystocia is an important factor in explaining SB incidence (Meyer et al., 2000).Despite the large number of records used in this study, a great deal of variation exists in SB probability of beef-sired calves.More work is required to validate this result and determine why increased probability of SB occurred in dairy cows carrying crossbred beef-sired calves compared with those that had Holstein-sired calves.
The lack of differences in dystocia probability in cows that carried beef breed or Holstein-sired calves is somewhat surprising.Previous works generally agree that dystocia rates are increased in dairy cattle mated to beef breeds.Spanish Holsteins mated Limousin sires were 1.19 times more likely to experience dystocia than those mated to Holstein bulls (Fouz et al., 2013).When compared with those bred to Swedish Red or Angus bulls, the incidence of dystocia increased in primiparous and multiparous Swedish Red cows when bred to Hereford (2.3% and 0.5%, respectively), Limousin (2.3% and 0.9%, respectively), Simmental (4.5% and 1.8%, respectively), or Charolais (4.4% and 2.7%, respectively) bulls (Eriksson et al., 2020).When comparing dystocia in primiparous Swedish Holsteins mated to the same beef breeds, Limousin, Simmental, and Charolais-sired calves resulted in greater rates of calving difficulty (4.3-6.7%)than Swedish Holstein-sired calves.Primiparous Swedish Holsteins tended to have fewer instances of dystocia when calves were sired by Angus bulls rather than Swedish Holstein bulls (Eriksson et al., 2020).In multiparous Holsteins, Limousin, Simmental, Charolais, and Hereford sires resulted in 0.4% to 2.9% more instances of dystocia than Swedish Holstein sires (Eriksson et al., 2020).Values within a row with different superscripts are different at P < 0.05. 1 Dystocia defined as calving ease (CE) score ≥4.
It is likely that many factors contributed to the lack of differences in dystocia risk by calf sire breed.A survey of Northeast dairy producers indicated that respondents primarily relied on the recommendations of semen sales representatives when selecting bulls to use in beef × dairy matings (Felix et al., 2023).As beef × dairy matings have increased in the United States, breed associations and stud companies marketing beef sires to mate to dairy females have emphasized CE in their selection criteria (Miller et al., 2021).Even if dairy producers are not independently selecting beef sires for CE, the beef sires being marketed for beef × dairy matings are generally favorable for the trait.
Recently, the scale of CE PTA was changed for US Holstein and Brown Swiss populations (Eaglen and Cole, 2020).The change was because both sire (direct) CE and daughter CE improved in the breeds over time due to selection (Eaglen and Cole, 2020).Regardless of calf sire breed, dairy cows today are experiencing less dystocia than cows from previous years.Additionally, recommended economic models of beef × dairy breeding suggest that most beef semen is used on the cows in the herd with lesser genetic merit, which is generally multiparous cows (De Vries, 2020;Cabrera, 2022).Both Fouz et al. (2013) and Eriksson et al. (2020) observed that calving difficulties were reduced with increasing dam regardless of service sire breed.It is likely that sire selection, improved calving ability in US dairy breeds, and biased used of beef semen on multiparous cows all contribute to the lack of differences in dystocia probability between cows carrying beef or Holsteinsired calves.
The GL of Holstein-sired calves in this study was the same as the average GL of US Holsteins born in 2010 (277 d; CDCB, 2017).Previous literature generally agrees GL differs in dairy cows mated to different sire breeds.The average GL of Spanish Holsteins carrying Limousin-sired calves was 6 d greater than those carrying Holstein-sired calves (Fouz et al., 2013).Holstein and Jersey × Holstein cows in a Kansas herd had the longest GL when carrying Jersey-sired calves (278 d), whereas Angus-sired calves were carried for an intermediate length (277 d), and Holstein-sired calves were carried for the shortest period (275 d; Scanavez and Mendonça, 2018).Holsteins and crossbred dairy cows in 2 US dairy herds carried calves sired by Simmental and Angus bulls for 1 to 3 d longer than Holstein-sired calves (Foraker et al., 2022).To our knowledge, no literature exists on the GL of dairy females carrying Wagyu-sired calves.However, Uematsu et al. (2013) previously estimated the GL of Japanese Black cattle to be 290 d, whereas the average GL of Angus cattle is 281 d (Torell, 2009).
As previously mentioned, GL that deviate significantly from the average, either shortened or extended, are associated with increased rates of SB (Meyer et al., 2000).Additionally, productive life was longest and cull rate least in Holsteins with GL closest to average (Norman et al., 2011).In beef cattle, GL is negatively correlated with weaning and yearling weights; indicating that calves that are carried for longer have reduced growth (Bourdon and Brinks, 1982).Further data are needed to validate if the same applies to the growth of beef × dairy calves.The health and milk production  (%) 6.08 4. 54-8.09 7.20 3.99-12.6 8.66 5.80-12.7 6.99 5.47-8.89 5.20 3.37-7.93 5.73 4.02-8.12 9.11 5.55-14.6Included any other health events recorded. 5 Early cull was defined as an animal that left the herd before reaching 60 DIM.results, presented in this paper and discussed later, suggest that the increased GL is not increasing probability of early-lactation health events or reducing milk and component yield.However, understanding that beef sires can increase GL may be important to dairy producers when deciding dry-off dates.Longer than expected GL result in additional days dry, which increases a cow's risk of uterine disease and reduces milk yield and fertility in her following lactation (Grummer and Rastani, 2004;Gumen et al., 2011).Particularly, dairy producers may want to consider drying off cows bred to Limousin and Wagyu sires about a week later than those bred to other sire breeds.Although GL is a highly heritable trait (Wright and VanRaden, 2017), expected progeny differences (EPD) of GL are not typically estimated for beef bulls in the United States.Before selecting for beef sires that will reduce GL, more data are necessary to determine if shorter GL will affect the development of beef × dairy calves.
With the growing number of beef × dairy matings occurring in the United States, it is possible to harness dairy herd records to generate EPD of SB incidence and GL for beef sires commonly used in beef × dairy matings.It may be logical for the organization already performing national dairy genetic evaluations, the Council on Dairy Cattle Breeding, to generate such EPD as they already use the same herd records to generate SB and GL PTA for dairy cattle.

Early-Lactation Health and Subsequent Milk Production
Clinical health event probability in the first 60 d postpartum was not affected by the sire breed of the calf delivered at lactation initiation.The lack of differences in probability of reproductive health events by calf sire breed mirrors the lack of differences in dystocia probability because dystocia is associated with metritis and retained placenta (Dematawewa and Berger, 1997).Scanavez and Mendonça (2018) observed that, in a single herd, the incidence of retained placenta and metritis events was numerically greater in cows that had Angussired (16.8%) calves but was not statistically different from cows that had Holstein (3.7%) or Jersey-sired (4.6%) calves.Additionally, early-lactation incidence of mastitis, displaced abomasum, pneumonia, and lameness events did not differ between cows carrying calves from different sire breeds (Scanavez and Mendonça, 2018).Data from Foraker et al. (2022) aligns with the lameness probabilities presented here; no differences in laminitis incidence were detected throughout the entire lactation between cows that carried beef or dairy-sired calves.The lack of differences in early death or culling rates reported here agree with Scanavez and Mendonça (2018); death or culling incidence during the first 60 d postpartum did not differ between cows that carried Holstein, Angus, or Jersey-sired calves.
In one of the dairy herds analyzed by Foraker et al. (2022), no differences existed in mastitis frequencies between cows that carried beef or dairy-sired calves.However, in the second herd, cows that carried Holstein-sired calves had 6% greater incidence of mastitis than those that had beef-sired calves (Foraker et al., 2022).When Scanavez and Mendonça (2018) summed total early-lactation disease incidence, 28% of cows that had Angus-sired calves experienced an early-lactation health event, which tended to be greater than in those that had Holstein (9.4%) or Jersey-sired (11.5%) calves.It is likely that our results differ from these previous analyses because previous data were limited to observations from single herds.Additionally, previous models did not account for potential biased usage of beef semen on cows that previously experienced disease whereas the statistical models in this paper did.
No differences in milk, fat, or protein yield existed in the subsequent lactation between cows that carried beef or Holstein-sired calves in this study.Including the cow's 305-d mature equivalent milk production in the previous lactation as a covariate in our models accounted for the potential selection bias of dairy farmers breeding their cows with reduced production to beef semen.Our results are generally in agreement with existing literature.No differences existed in the milk, fat, or protein yield of multiparous cows that had Friesian, Charolais, Simmental, or Hereford-sired calves at the initiation of lactation (Badi et al., 1985).Similarly, a study of Friesian cows mated to Friesian, Charolais, or Hereford bulls did not observe any differences in milk yield by service sire breed during gestation or in the subsequent lactation (More O'Ferrall and Ryan, 1990).In contrast, Irish Holstein-Friesian cows mated to beef bulls yielded significantly less milk, fat, and protein in their subsequent lactation when compared with their counterparts bred to Holstein bulls (Berry and Ring, 2020).However, the largest reduction in milk production, observed in cows that were mated to Charolais bulls, was only 101 kg less for the entire lactation than those mated to Holsteins (Berry and Ring, 2020).The differences in production were considered biologically small and overall sire breed only explained about 1% of the phenotypic variation observed (Berry and Ring, 2020).
The lack of differences detected in probability of early-lactation clinical health events and culling, and subsequent milk production by sire breed of calf carried in this study are promising.They suggest that carrying a beef-sired calf will not affect a cow's future health and productivity differently than carrying a Holstein-sired calf.

CONCLUSIONS
Dairy cows mated to Angus, Simmental, Limousin, crossbred beef, Charolais, and other beef breed sires did not differ in dystocia probability from cows bred to Holstein sires.The probability of calves sired by crossbred beef bulls being SB was greater than that of Holsteinsired calves, while no differences existed in SB probability in calves sired by the other beef breeds observed.The GL of cows carrying beef-sired calves was greater than in those carrying Holstein-sired calves; Wagyu and Limousin-sired calves were carried for the greatest number of days.Despite the increased GL, carrying a beef-sired calf did not influence the probability of earlylactation health events nor the risk of death or culling within the first 60 d of lactation.Additionally, cows that carried beef-sired calves did not differ in milk, fat, or protein yield when compared with those that carried Holstein-sired calves.Results suggest that current beef × dairy sire selection parameters in the United States are not negatively affecting the dairy cow.

µ
where p = the probability of y ijklmn = 1, where y = reproductive, metabolic, mastitis, lameness, other, or any health event occurring in the first 60 d of lactation; µ = model intercept; SSB i = breed of calf sire at lactation initiation i (Angus, Charolais, Crossbred Beef, Holstein, Limousin, Simmental, or other); LG j = lactation group j (2, 3, 4, or 5+); herd k = herd where k = herd 1 to herd 9; PEvent l = if an event of the same category occurred in the first 60 d of the previous lactation (l = 0 or 1); HY m = the random effect of herd year of calving m; and sire n = the random effect of individual calf sire n at lactation initiation.The same generalized linear mixed model evaluated culling rate in the first 60 d of lactation with PEvent replaced with the previous lactation's 305-d mature equivalent milk production.Test-date production was evaluated with the following linear mixed model: where y = the dependent variable milk, fat, or protein yield (kg); µ = model intercept; SSB i = breed of calf sire at lactation initiation i (Angus, Charolais, Crossbred Beef, Holstein, Limousin, Simmental, or other);LG j = lactation group j (2, 3, 4, or ≥5); DIM k = days in milk grouped in 1-wk intervals k (1 to ≥60); herd l = herd where l = herd 1 to herd 9; P305 m = 305-d mature equivalent milk production in the previous lactation m; HYS n = the random effect of herd year of calving n; sire o = the random effect of individual calf sire o at lactation initiation; cow p = the random effect of individual cow p; and ε ijklmnop = residual error.
Basiel et al.: IMPACT OF CARRYING BEEF-SIRED CALVES ON COWS Table Figure 1.Gestation length, in days, of dairy cows by sire breed of the calf carried.Error bars represent SE.Bars labeled with different letters (a-d) are different at P < 0.05.
Basiel et al.: IMPACT OF CARRYING BEEF-SIRED CALVES ON COWS

Table 1 .
Basiel et al.:IMPACT OF CARRYING BEEF-SIRED CALVES ON COWS Lactation records used following data edits available from 10 participating herds from 2010 to 2023 by sire breed of calf born at lactation initiation

Table 2 .
Descriptive statistics of dystocia incidence, stillbirth incidence, and gestation length records

Table 3 .
Basiel et al.:IMPACT OF CARRYING BEEF-SIRED CALVES ON COWS Categorization of clinical health events occurring within 60 DIM and event incidence from 52,116 lactations of 28,355 multiparous cows Early cull was the incidence of early culling from the 12,123 records of animals that died or were culled during a lactation.

Table 4 .
Descriptive statistics of test-date production records available LG j = lactation group j (2, 3, 4, or 5+); herd k = herd where k = herd 1 to herd 10; sex l = phenotypic calf sex l (heifer, bull, or undefined); HY m = the random effect of herd year of calving m; and sire n = the random effect of individual calf sire n at lactation initiation.

Table 6 .
Basiel et al.:IMPACT OF CARRYING BEEF-SIRED CALVES ON COWS Probability of stillbirth and dystocia incidence by calf sire breed

Table 7 .
Probability of clinical health events within 60 DIM by sire breed of calf born at lactation initiation Item

Table 8 .
Test-date milk, fat, and protein yield by sire breed of calf born at the initiation of lactation Item Basiel et al.: IMPACT OF CARRYING BEEF-SIRED CALVES ON COWS