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State Key Laboratory of Animal Nutrition, Institute of Animal Science, Chinese Academy of Agricultural Sciences, Beijing 100193, P.R. ChinaChinese Academy of Agricultural Sciences-World Agroforestry Centre (CAAS-ICRAF) Joint Laboratory on Agroforestry and Sustainable Animal Husbandry, World Agroforestry Centre, East and Central Asia, Beijing 100193, China
State Key Laboratory of Animal Nutrition, Institute of Animal Science, Chinese Academy of Agricultural Sciences, Beijing 100193, P.R. ChinaChinese Academy of Agricultural Sciences-World Agroforestry Centre (CAAS-ICRAF) Joint Laboratory on Agroforestry and Sustainable Animal Husbandry, World Agroforestry Centre, East and Central Asia, Beijing 100193, ChinaHunan Co-Innovation Center of Safety Animal Production, Changsha, Hunan 410128, China
The objective of this study was to investigate the effects of dietary energy levels and rumen-protected lysine supplementation on serum free fatty acid levels, β-hydroxybutyrate levels, dry matter (DM) intake, and milk production and composition. Treatments were arranged in a 2 × 2 factorial design with 2 dietary energy levels [high net energy for lactation (NEL) = 1.53 Mcal/kg of DM vs. low NEL = 1.37 Mcal/kg of DM; HE vs. LE) fed either with rumen-protected lysine (bypass lysine; 40 g/cow per day) or without rumen-protected lysine (control). Sixty-eight third-lactation Holstein dairy cows entering their fourth lactation were randomly allocated to 4 treatments groups: HE with bypass lysine, HE without bypass lysine, LE with bypass lysine, and LE without bypass lysine. Groups were balanced based upon their expected calving date, previous milk yields, and body condition score. All cows were fed the same diet (NEL = 1.34 Mcal/kg of DM) during the dry period prior to the trial. Rumen-protected lysine was top-dressed on a total mixed ration to deliver 9.68 g/d of metabolizable lysine to pre- and postpartum cows. After calving, all cows received the same TMR (1.69 Mcal/kg of DM). Blood samples were collected at −21, −14, −7, 0, 3, 7, 14, and 21 d relative to calving, and free fatty acids and β-hydroxybutyrate concentrations were measured. Amount of feed offered and orts were collected and measured for individual cows 4 d/wk. Milk samples were collected once per week following calving, and milk composition was analyzed. Feeding high NEL to close-up cows decreased the concentrations of free fatty acid and β-hydroxybutyrate in prepartum cows but not in postpartum cows. Addition of rumen-protected lysine increased postpartum DM intake, and decreased serum free fatty acid and β-hydroxybutyrate concentrations. Neither energy nor rumen-protected lysine supplementation nor their interaction affected milk yield or fat or lactose yields. However, cows in the group receiving HE with bypass lysine tended to produce more milk compared with other groups and had a lower blood β-hydroxybutyrate concentration postpartum. These results indicate that feeding a high-energy diet together with rumen-protected lysine improved DM intake and lowered serum free fatty acid and β-hydroxybutyrate concentrations in transition cows.
As cows transition from the gestation period to lactation (3 wk before to 3 wk after calving), they undergo significant physiological and immunological changes, and the incidence of many metabolic disorders is at its highest during early lactation (
). During the transition period, it is difficult or impossible to meet the increased nutrient demands of cattle because of restricted feed intake, which results in cows mobilizing their fat stores as well as muscle tissue to compensate for the dietary nutrient deficit.
reported that the daily DMI of transition cows was reduced by up to 30% and was accompanied by an increased energy demand due to the onset of lactation, leading to a negative energy balance. Most high-producing dairy cows usually face some degree of negative energy balance, which is accompanied by immune suppression around parturition (
The transition period is a key phase in the lactation cycle and requires intensive dietary management. Feeding higher energy diets to cows during the dry and close-up periods could improve body condition, but it does not reduce the degree of adipose tissue mobilization during the transition period; it only exacerbates the negative energy balance during early lactation (
Far-off and close-up dry matter intake modulate indicators of immunometabolic adaptations to lactation in subcutaneous adipose tissue of pasture-based transition dairy cows.
). Studies have demonstrated that overfeeding even a moderate-energy diet resulted in greater metabolic stress and incidence of disorders (such as ketosis and fatty liver) in postpartum cows, which can have a profound negative impact on milk yield even before an official diagnosis can be made (
). Although high-energy diets predispose postpartum cows to experience a more negative energy balance, cows fed a precalving high-energy diet (1.7 Mcal/kg of DM) had a more positive energy balance, higher plasma concentrations of glucose and insulin, a 19.8% increase in DMI, and lower concentrations of plasma nonesterified fatty acids (NEFA) on d −7 relative to calving compared with cows fed a low-energy (1.58 Mcal/kg of DM) ration (
To reduce the risk of metabolic disorders, it is important to increase energy intake, but this practice carries some associated risks. Carnitine is a methylated form of lysine (
). Carnitine is important for oxidation of long-chain fatty acids, regulation of ketosis, support of the immune system, and enhancement of the antioxidant system (
Because lysine is largely degraded by ruminal microbes, supplementation of free lysine is an inefficient strategy to increase the supply of lysine that serves as the carbon backbone for carnitine synthesis and performs other functions (
Ardaillon, P., and C. Franzoni. 1992. Enzymatically degradable coating compositions for feed additives intended for ruminants. Rhone-Poulenc Santé, assignee. U.S. Pat. No. 5,098,718.
). However, the interaction of precalving energy and rumen-protected lysine (RPL) during the transition period in dairy cows has not been well explored.
Therefore, the inclusion of lysine is a critical factor in the manipulation of the dietary energy content of TMR fed to close-up cows to control their negative energy balance. In the present study, we hypothesized that providing transition cows with an increased level of energy and providing RPL would improve DMI, reduce serum free fatty acid (FFA) and BHB concentrations, and increase milk production during the transition period. The objective of the current study was to investigate the effects of close-up supplementation of dietary NEL levels (1.53 or 1.37 Mcal/kg of DM) and supplementation of RPL (0 or 40 g/cow per day) on FFA levels, BHB levels, DMI, and milk production and composition during the transition period in dairy cows.
MATERIALS AND METHODS
Experimental Design and Experimental Cows
All procedures were approved by the Animal Care and Use Committee of the Institute of Animal Science, Chinese Academy of Agricultural Sciences, Beijing. Cows in the same parity (third lactation) entering their fourth lactation were chosen based on BCS ≥ 3.25 and ≤3 .5 (1–5 scale) from a large herd. The expected calving date of each cow was considered in selecting cows with similar expected calving dates and previous milk yield. All selected cows were balanced for their BCS, expected calving date, and previous milk yield (13,679.65 ± 2,370.4 kg 305 d milk yield, P = 0.80) before being randomly assigned to dietary treatment groups. A statistical power analysis was performed with an α = 0.05 and power = 0.90, and the sample size needed with 0.4 effect size, projected using G power 3.1 software (
), was approximately 68 cows. The 68 selected cows were each randomly allocated to 1 of 4 dietary treatment groups (n = 17 in each group) arranged in a 2 × 2 factorial design using 2 dietary NEL levels (high energy, NEL = 1.53 Mcal/kg of DM vs. low energy, NEL = 1.37 Mcal/kg of DM; HE vs. LE) and RPL added at the level of 0 (control) or 40 g/cow per day (bypass lysine), respectively. Dietary treatments were arranged as HE with bypass lysine, HE without bypass lysine, LE with bypass lysine, and LE without bypass lysine.
Dietary Treatment Rations and Cow Housing
Before being fed the close-up HE or LE rations, all cows received the same diet (NEL = 1.34 Mcal/kg of DM) during the dry period until d −21 when cows were switched to either HE or LE rations until d 0 (calving date). After calving, all cows received the same lactation ration up to d 21 (NEL = 1.69 Mcal/kg of DM). The diets were formulated based on
to meet the nutrient requirements of a prepartum cow weighing 650 kg and consuming 12.01 kg of DM/d and a postpartum cow weighing 580 kg, consuming 16.7 kg of DM/d, yielding 33 kg/d of milk, 3.85% milk fat, 3.07% of milk true protein, and 3.5 BCS. Dietary lysine and methionine were formulated based on
recommendations (6.9% MP-Lys and 2.3% MP-Met) to meet the lysine-to-methionine ratio of 3:1 both for pre- and postpartum cows.
For the bypass lysine diets, RPL was top-dressed on the TMR once per day at a rate of 40 g of lysine/cow, using 50 g of ground corn as a carrier. Fifty grams of ground corn was also top-dressed to control diets. The RPL supplement (Ascor Chimici Srl, Beijing, China) contained 55% lysine with 44% bioavailability, and the pre- and postpartum lysine-fed cows therefore received 9.68 g/d of metabolizable lysine. The values for RUP, RDP, Lys, and Met were evaluated using AMTS software (AMTS LLC, Groton, NY) based on the actual mean DMI and are presented in Table 1.
Table 1Chemical composition (% of DM unless otherwise noted) and evaluation of prepartal and postpartal diets fed to multiparous Holstein cows with or without rumen-protected lysine (RPL) during the transition period
Close-up cow diets were high energy (NEL = 1.53 Mcal/kg of DM) with (HE-Lys) or without (HE) RPL (40 g/cow per day) or low energy (NEL = 1.37 Mcal/kg of DM) with (LE-Lys) or without (LE) RPL; lactation diet (all cows): NEL = 1.69 Mcal/kg of DM.
Chemical component
Close-up cow diet
Fresh cow diet
LE
LE-Lys
HE
HE-Lys
LE
LE-Lys
HE
HE-Lys
NEL (Mcal/kg of DM)
1.37
1.37
1.53
1.53
1.69
1.69
1.69
1.69
CP
15.1
15.1
15.1
15.1
18.0
18.0
18.0
18.0
DM
54.04
54.12
53.43
53.58
55.28
55.33
55.28
55.33
NDF
42.94
42.8
38.57
38.44
27.92
27.85
27.92
27.85
ADF
24.25
24.17
21.58
21.51
16.63
16.59
16.63
16.59
Ash
5.6
5.6
5.6
5.6
5.5
5.5
5.5
5.5
Sugar
4.99
4.99
4.96
4.96
5.91
5.91
5.91
5.91
RDP
9.94
9.97
10.23
9.97
11.47
11.37
11.10
11.07
RUP
5.19
5.21
5.28
5.58
6.68
6.81
7.04
7.10
RDP supplied (g/d)
1,262.4
1,256.2
1,235.4
1,371.7
2,040.7
2,103.5
1,111.2
1,107.3
RUP supplied (g/d)
659.1
656.5
640.1
770.4
1,188.2
1,259.1
704.8
709.7
MP supplied (g/d)
1,101.51
1,094.76
1,111.43
1,296.1
2,208.1
2,295.9
2,538.9
2,566.98
MP from bacteria (g/d)
599
593
623
699
934
962
1,051
1,057
MP from RUP (g/d)
473
472
459
568
944
1,004
1,159
1,181
Lys:Met
2.85:1
3.09:1
2.84:1
3.07:1
2.97:1
3.15:1
2.97:1
3.15:1
Lys (% of MP)
6.54
7.07
6.59
7.02
6.47
6.81
6.4
6.76
MP-Lys (g)
72.05
77.45
73.23
91
142.86
156.38
162.53
173.56
Met (% of MP)
2.3
2.29
2.32
2.29
2.18
2.16
2.16
2.15
MP-Met (g)
25.32
25.04
25.77
29.67
48.1
49.68
54.76
55.11
NEL allowable milk (kg/d)
—
—
—
—
29.7
31.5
35.1
35.7
MP allowable milk (kg/d)
—
—
—
—
27
28.4
32.1
32.5
NFC
27.5
27.41
31.8
31.7
40.76
40.66
40.76
40.66
Ether extract
3.23
3.40
3.47
3.57
4.56
4.67
4.56
4.44
Ca
1.61
1.61
1.56
1.57
0.91
0.92
0.91
0.92
P
0.45
0.45
0.46
0.46
0.4
0.4
0.4
0.4
Mg
0.55
0.55
0.54
0.54
0.43
0.43
0.43
0.43
Cl
0.91
0.93
0.86
0.88
0.57
0.59
0.57
0.59
K
1.04
1.04
0.98
0.97
1.32
1.32
1.32
1.32
Na
0.3
0.3
0.28
0.28
0.55
0.55
0.55
0.55
S
0.42
0.42
0.41
0.41
0.20
0.20
0.20
0.20
1 Close-up cow diets were high energy (NEL = 1.53 Mcal/kg of DM) with (HE-Lys) or without (HE) RPL (40 g/cow per day) or low energy (NEL = 1.37 Mcal/kg of DM) with (LE-Lys) or without (LE) RPL; lactation diet (all cows): NEL = 1.69 Mcal/kg of DM.
All experimental cows were housed in a ventilated enclosed barn during the experimental period and were individually fed their respective diets. Cows had access to stand and bedding areas until 3 d before expected parturition, when they were moved to individual maternity pens bedded with straw until parturition. After parturition, cows were individually fed a common lactation diet, with or without lysine supplementation. Total mixed rations were mixed daily and provided twice per day at 0600 and 1400 h (Table 1, Table 2). All cows were fed ad libitum with their respective dietary rations.
Table 2Ingredient composition of diets fed during close-up (−21 d to calving) and early lactation (calving to 21 d) periods
Close-up cow diets were high energy (NEL = 1.53 Mcal/kg of DM) with (HE-Lys) or without (HE) rumen-protected lysine (RPL; 40 g/cow per day) or low energy (NEL = 1.37 Mcal/kg of DM) with (LE-Lys) or without (LE) RPL; lactation diet (all cows): NEL = 1.69 Mcal/kg of DM. After parturition, the same 40 g/cow per day of RPL was supplemented for cows that had been fed RPL before calving.
1 Close-up cow diets were high energy (NEL = 1.53 Mcal/kg of DM) with (HE-Lys) or without (HE) rumen-protected lysine (RPL; 40 g/cow per day) or low energy (NEL = 1.37 Mcal/kg of DM) with (LE-Lys) or without (LE) RPL; lactation diet (all cows): NEL = 1.69 Mcal/kg of DM. After parturition, the same 40 g/cow per day of RPL was supplemented for cows that had been fed RPL before calving.
2 A 4.75-mm sieve was used, and the kernel processing score was 50 to 70%.
3 Alfalfa hay was used to formulate the TMR.
4 Soybean meal contained 89.1% DM and 42.6% CP.
5 DDGS = distillers dried grains with solubles; nutrient-rich by-product of dry-milled ethanol production.
6 Extracted soybean contained 92.6% DM and 36.4% CP.
7 Close-up and fresh cow mineral premix: Ca, P, Mg, K, Na, Cl, and S.
8 BCP Ingredients Inc., Verona, MO.
9 BergaFat100 (Berg and Schmidt Nutrition Sdn. Bhd., Malaysia): bypass fats for ruminants providing extra energy without a carrier.
Feed offered and refusals were recorded each morning for 4 consecutive days per week. The TMR samples were frozen at −20°C and composited monthly for analysis of DM, CP, NDF, ADF, and ash. Dry matter intake was determined by measuring feed provided and subtracting the orts remaining. Samples of TMR and orts from each treatment were analyzed for DM content by oven-drying at 60°C until they maintained a constant weight. The dried samples were ground through a 1-mm screen using a Cyclotec 1093 Mill (Tecator 1093, Tecator AB, Höganäs, Sweden) before analysis. Samples were further dried at 105°C for 2 h to determine the absolute DM, and chemical analyses were based on the final absolute DM. The CP (N × 6.25) content of feed samples was determined using the macro-Kjeldahl nitrogen test (
; method 976.05) with a Kjeltec digester 20 and a Kjeltec System 1026 distilling unit (Tecator AB). The contents of NDF and ADF were determined using procedure A by
using heat-stable amylase (type XI-A of Bacillus subtilis; Sigma-Aldrich Corp., St. Louis, MO). The ash content was determined by incineration at 550°C overnight, and the OM content calculated (
Duplicate blood samples of approximately 15-mL were collected via a coccygeal vein from individual cows at 0700 h daily on d −21, −14, −7, 0, 3, 7, 14, and 21 relative to calving. All the blood samples were collected in serum separator tubes (Serum Clot Activator, Greiner Bio-one GmbH, Kremsmunster, Austria), and the samples were allowed to clot for a minimum of 25 min at 20°C and stored in the refrigerator overnight. The samples were then centrifuged at 3,000 × g for 15 min at 4°C before separation of the serum. Blood serum was analyzed for BHB and FFA concentrations using commercial assay kits (Nanjing Jiancheng Bioengineering Institute, Nanjing Jiancheng Technology Co. Ltd., Nanjing, China) according to the manufacturer's instructions.
Milk Samples
Duplicate milk samples from individual cows were collected at 3 consecutive milkings and mixed based on the average milk production at each milking (morning, afternoon, and night; volume ratio of 4:3:3) on d 7, 14, and 21. One aliquot of milk was preserved with bronopol-B2 preservative (D & F Control Systems Inc., Dublin, ON, Canada) at 4°C and subsequently analyzed for fat, protein, lactose, SCC, and MUN using a mid-infrared machine (Foss MilkoScan, Foss Food Technology Corp., Eden Prairie, MN).
Body Condition Scoring
Body condition scoring of experimental cows in all 4 dietary treatment groups was scored weekly from d −21 through 21 relative to parturition day using a standard 5-point scale (1 = emaciated, 5 = obese). Body condition scores were always assessed by the same trained operative by palpating and visualizing individual body parts of the spinal column, the cranial coccygeal vertebrae, the tuber ischia, the tuber sacral, and the thigh region as described by
The data for DMI, milk yield, milk composition, and blood parameters (FFA and BHB) were analyzed as a completely randomized design with repeated measures using PROC MIXED of SAS (version 9.2, SAS Institute Inc., Cary, NC). The MIXED statistical model used for analysis was as follows:
where yijkl was the dependent, continuous variable; µ was the overall mean; Li was the fixed effect of lysine (i = with or without supplementary lysine); Ej was the fixed effect of energy (j = 1.37 or 1.53 Mcal/kg of DM); Aijk was the random effect of the kth cow in the ijth combination of lysine and energy; Tl was the fixed effect of time (day) of the experiment; the 2- and 3-way interactions of the time, lysine, and energy, all considered fixed; and εijkl was the residual error. Serum FFA, BHB, DMI, milk yield, and composition were analyzed at various time point that were not equally spaced; hence, the covariance structure for the repeated measurements was modeled using the spatial power option. The Kenward-Roger option was used for computing the denominator degrees of freedom for testing hypotheses. All experimental cows grouped according to dietary treatment rations were carefully selected and balanced in BCS, previous milk yield, and expected calving date and had the same parity (third lactation) at the start of the trial. We did not see any significant difference in these variables at the beginning of the study, so we did not include these variables as covariates in statistical analysis. Least squares means were compared using LSD, and statistical differences were declared significant at P ≤ 0.05. Tendencies were determined at P ≤ 0.10.
RESULTS AND DISCUSSION
Pre- and Postpartum DMI
Main effects of precalving energy density, RPL, time, and their interactions on DMI, FFA, BHB, BCS, milk yield, and milk composition are summarized in Table 3, Table 4. The dietary energy levels in this trial were formulated based on the
recommendations of 1.54 to 1.62 Mcal/kg of DM for the close-up period.
Table 3Main effect of close-up dietary energy density and rumen-protected lysine supplementation on DMI, free fatty acids (FFA), BHB, BCS, and milk yield and composition during the transition period in dairy cows
RPL = rumen-protected lysine (Ascor Chimici Srl, Beijing, China) top dressed on TMR at a total rate of 40 g/cow per day to deliver 9.68 g of metabolizable lysine to pre- and postpartum cows during the transition period.
Means from main effect in the same row with different superscripts are significantly different (P < 0.05) using the least significant difference method.
Means from main effect in the same row with different superscripts are significantly different (P < 0.05) using the least significant difference method.
Means from main effect in the same row with different superscripts are significantly different (P < 0.05) using the least significant difference method.
Means from main effect in the same row with different superscripts are significantly different (P < 0.05) using the least significant difference method.
Means from main effect in the same row with different superscripts are significantly different (P < 0.05) using the least significant difference method.
Means from main effect in the same row with different superscripts are significantly different (P < 0.05) using the least significant difference method.
Means from main effect in the same row with different superscripts are significantly different (P < 0.05) using the least significant difference method.
Means from main effect in the same row with different superscripts are significantly different (P < 0.05) using the least significant difference method.
Means from main effect in the same row with different superscripts are significantly different (P < 0.05) using the least significant difference method.
Means from main effect in the same row with different superscripts are significantly different (P < 0.05) using the least significant difference method.
Means from main effect in the same row with different superscripts are significantly different (P < 0.05) using the least significant difference method.
Means from main effect in the same row with different superscripts are significantly different (P < 0.05) using the least significant difference method.
Means from main effect in the same row with different superscripts are significantly different (P < 0.05) using the least significant difference method.
Means from main effect in the same row with different superscripts are significantly different (P < 0.05) using the least significant difference method.
Means from main effect in the same row with different superscripts are significantly different (P < 0.05) using the least significant difference method.
Means from main effect in the same row with different superscripts are significantly different (P < 0.05) using the least significant difference method.
Means from main effect in the same row with different superscripts are significantly different (P < 0.05) using the least significant difference method.
Means from main effect in the same row with different superscripts are significantly different (P < 0.05) using the least significant difference method.
a,b Means from main effect in the same row with different superscripts are significantly different (P < 0.05) using the least significant difference method.
1 RPL = rumen-protected lysine (Ascor Chimici Srl, Beijing, China) top dressed on TMR at a total rate of 40 g/cow per day to deliver 9.68 g of metabolizable lysine to pre- and postpartum cows during the transition period.
2 Close-up low-energy diet (LE) = 1.37 Mcal of NEL/kg of DM; close-up high-energy diet (HE) = 1.53 Mcal of NEL/kg of DM.
3 Time = effect of time: d −21, −14, −7, 0, 3, 7, 14, and 21 relative to calving day.
Table 4Interaction effect of close-up dietary energy density and rumen-protected lysine (RPL; bypass lysine, Ascor Chimici Srl, Beijing, China) supplementation on DMI, free fatty acids (FFA), BHB, BCS, and milk yield and composition in dairy cows during the transition period
Diets were high energy (NEL = 1.53 Mcal/kg of DM) with (HE-Lys) or without (HE) RPL (40 g/cow per day) or low energy (NEL = 1.37 Mcal/kg of DM) with (LE-Lys) or without (LE) RPL.
Means from interactions in the same row with different superscripts are significantly different (P < 0.05) using the least significant difference method.
Means from interactions in the same row with different superscripts are significantly different (P < 0.05) using the least significant difference method.
Means from interactions in the same row with different superscripts are significantly different (P < 0.05) using the least significant difference method.
Means from interactions in the same row with different superscripts are significantly different (P < 0.05) using the least significant difference method.
a,b Means from interactions in the same row with different superscripts are significantly different (P < 0.05) using the least significant difference method.
1 Diets were high energy (NEL = 1.53 Mcal/kg of DM) with (HE-Lys) or without (HE) RPL (40 g/cow per day) or low energy (NEL = 1.37 Mcal/kg of DM) with (LE-Lys) or without (LE) RPL.
2 Time = effect of time (d −21, −14, −7, 0, −3, 7, 14, and 21 relative to calving).
In the present study, the precalving HE diet (1.53 Mcal/kg of DM) significantly increased DMI by 13.2% in postpartum cows (P < 0.01, Figure 1A). Similarly,
reported that cows fed a prepartum high-energy diet (1.70 Mcal/kg of DM) had 19.8% greater DMI (% of BW) than cows fed a low-energy-density diet (1.58 Mcal/kg of DM).
Figure 1Effects of close-up dietary energy level and supplementing rumen-protected lysine (RPL, bypass lysine, Ascor Chimici Srl, Beijing, China) on DMI and MUN levels in dairy cows during the transition period. Diets were high energy (NEL = 1.53 Mcal/kg of DM) with (HE-Lys) or without (HE) RPL (40 g/cow per day) or low energy (NEL = 1.37 Mcal/kg of DM) with (LE-Lys) or without (LE) RPL. Values are means; error bars represent standard error.
The precalving HE diet had a significant carryover effect on the DMI in postpartum cows. We observed a trend for greater (diet, P = 0.08) DMI in kilograms per day from d −21 to the day of parturition in cows fed the HE diet compared with control cows. The HE diet may have had better palatability, stimulating the DMI of the cows. In addition to palatability, hormonal, metabolic, and inflammatory changes may also influence the DMI of the cows during the transition period. The additive effects of several stimuli may affect cows' DMI; as a result, the factors that affect or surround the DMI of cows are very complex and largely not yet understood (
reported that cows fed high NEL of 1.7 Mcal/kg of DM from d −28 to calving had increased DMI and energy intake.
We found that supplementation of TMR with RPL significantly improved DMI in postpartum cows (P = 0.03, Figure 1B), which was similar to the findings of
who reported that the addition of RPL to the diet of mid-lactation cows tended to increase DMI. Feeding a precalving high-energy diet with bypass lysine (40 g/cow per day) increased prepartum DMI of cows (14.9%, P < 0.01) in that trial. The increased DMI in the current study could be due to greater MP and lysine intake, which reduced deficiency. Similarly, we found that RPL supplementation of the close-up diet increased DMI of cows compared with those in unsupplemented groups (P = 0.03). This finding may be explained by lysine contributing more to endogenous synthesis of carnitine, which would subsequently increase DMI. A previous study showed that as carnitine dose increased from 1 to 3 g/d, DMI tended to increase (
). This finding demonstrated that the addition of RPL into TMR had a positive impact on DMI in both pre- and postpartum cows. In the present study, we found a positive effect on DMI by addition of RPL to a prepartum diet containing 15.1% CP (P < 0.01, Figure 1E). Similarly, supplementation of RUP to increase dietary CP percentage to 19% CP improved DMI, milk production, and efficiency of protein metabolism in postpartum cows (
Effects of rumen undegradable protein supplementation on productive performance and indicators of protein and energy metabolism in Holstein fresh cows.
). Although the mechanisms of hunger and satiety were thoroughly investigated in recent decades, factors surrounding the regulation of DMI are not fully understood yet (
). Our results show that feeding a precalving HE diet (1.53 Mcal/kg of DM) significantly decreased serum FFA concentrations in prepartum cows by 21.7%, (P = 0.03, Figure 2C), but it did not affect FFA concentrations in postpartum cows. A close-up HE diet did not influence FFA concentration after calving, but the lower serum FFA concentrations for HE-fed cows reflected a more favorable energy status and indicated less adipose tissue mobilization during the prepartum period. Cows fed a high-energy-density diet (1.7 NEL Mcal/kg of DM) had higher plasma concentrations of glucose and insulin, and a lower concentration of plasma NEFA on d −7 relative to calving compared with cows fed low energy density (1.57 NEL Mcal/kg of DM) ration (
Figure 2Effects of close-up dietary energy level and supplementing rumen-protected lysine (RPL; bypass lysine, Ascor Chimici Srl, Beijing, China) on BHB and free fatty acids (FFA) concentrations in dairy cows during the transition period. Diets were high energy (NEL = 1.53 Mcal/kg of DM) with (HE-Lys) or without (HE) RPL (40 g/cow per day) or low energy (NEL = 1.37 Mcal/kg of DM) with (LE-Lys) or without (LE) RPL. Values are means; error bars represent standard error.
Cows in the HE groups had numerically higher FFA concentrations in the first 2 wk after calving compared with cows in the LE group. Our data suggest that the precalving HE diet did not improve the negative energy balance and thereby increase body fat mobilization in postpartum cows. Prepartum feeding of high-energy-density diets has been previously shown to have a minor influence on metabolic status of cows postpartum (
Supplementation of RPL decreased serum FFA concentrations by 14.3% in postpartum cows (P < 0.01, Figure 2D). In the present trial, the lowest FFA concentration (0.54 mM) was observed on d 0 (calving) in cows supplemented with RPL, whereas the highest FFA concentration (1.08 mM) was found on d 14 after calving in cows fed precalving HE diet without RPL supplementation. Our data suggest that feeding only close-up HE rations predisposes postpartum cows to have greater NEFA concentrations, as many authors have previously reported. Increased FFA concentrations in non-lysine-supplemented groups probably reflected a lower contribution of metabolizable lysine for carnitine synthesis to export FFA for β-oxidation compared with lysine-supplemented cows, which was probably also related to greater DMI with lysine and possible potentiation of anabolic signaling in tissues in response to lysine.
Effects of prepartal body condition score and peripartal energy supply of dairy cows on postpartal lipolysis, energy balance and ketogenesis: An animal model to investigate subclinical ketosis.
demonstrated that feeding late-gestation cows with a high proportion of concentrate lowered postpartum negative energy balance and increased NEFA concentrations. In the present study, we did not observe any interactions between precalving energy levels and RPL on FFA concentrations in pre- and postpartum cows (P = 0.97, Figure 2F).
Effects on BHB Concentrations
Feeding a high-energy diet to dairy cows in the late prepartum period resulted in a significant increase in energy balance until the day of calving in a previous study (
). In the present study, precalving HE diets decreased plasma BHB concentrations by 32.7% in prepartum cows (P < 0.01, Figure 2A). Similar to our results, plasma concentrations of BHB on d 21 were previously found to be 46% lower for cows fed high-energy diets compared with cows fed low-energy diets (
). This finding may be due to a higher level of starch in a high-energy diet, which favors ruminal propionate (a glucogenic VFA) production and improves hepatic glucose production, which may in turn lead to lower fat mobilization and lower BHB concentrations in prepartum cows. Similarly,
reported that prepartum feeding of higher concentrate diets might provide more glucogenic propionate and reduce the incidence of ketosis around calving. These research results indicate that cows fed a precalving high-energy diet (low forage) were not mobilizing much energy from adipose tissue stores, which resulted in low BHB levels. In contrast,
reported that diets that contained a higher proportion of fiber increased DMI and prevented severe adipose tissue lipolysis. On the other hand, overfeeding a high-energy diet during the close-up period actually increases adipose tissue mobilization, leading to a greater negative energy balance (
reported that concentrations of BHB less than 2.6 mM and greater than 1.4 mM in the first week after calving and BHB levels >1.0 mM from d 7 to 10 postpartum represented cows with subclinical ketosis.
indicated that cows with BHB concentrations greater than 2.6 mM are defined as having clinical ketosis. In our study, cows fed the HE diet with RPL had lower BHB levels than cows with subclinical ketosis (
reported that feeding NEL of 1.37 Mcal/kg of DM from d 28 before calving to 5 wk after calving affected the concentrations of both BHB and NEFA. Our results are consistent with those findings because feeding close-up cows a similar energy diet together with RPL resulted in a lower BHB concentration in postpartum cows.
A previous study showed that high CP levels in the diet of cows decreased the concentration of BHB (
Effects of rumen undegradable protein supplementation on productive performance and indicators of protein and energy metabolism in Holstein fresh cows.
), and our results were consistent with this decrease in postpartum BHB levels (P = 0.01, Figure 2B). Energy and lysine supplementation had a significant interactive effect on BHB concentration in postpartum cows (P = 0.04, Figure 2E), but not in prepartum cows.
We hypothesize that RPL increased the bioavailability of carnitine (a methylated form of lysine), which consequently reduced NEFA concentration via β-oxidation, which may impair normal liver function. Decreasing NEFA concentration in the liver leads to lower mobilization of adipose tissue and a reduction of serum BHB concentrations. The liver appears to synthesize more glucose from propionate at d 21 postpartum compared with d 1 after calving or d 21 prepartum (
reported that the amount of mobilized tissue protein used as a source of amino acids for mammary metabolism and gluconeogenesis was relatively small from calving to peak lactation. The limited production of glucose during this period may have increased BHB levels in cows fed a prepartum LE diet.
Effects on Milk Yield and Composition
Precalving energy, RPL, and their interactions did not affect SCC, ECM, FCM, or milk, fat, or lactose yields in this study (Table 3, Table 4). In line with this, a previous study found that feeding dairy cows RPL to deliver 41 g of lysine/cow per day did not affect milk, true protein, or lactose yields in early lactation (
who did not observe any difference in milk yield or composition when RPL was supplemented into diets containing either distillers dried grains with soluble or wet corn gluten feed, respectively. Milk yield is less responsive to duodenal methionine and lysine supply than milk protein (
reported that milk yield was unaffected when 16 g/d intestinally absorbable lysine was added to the diet of early lactation cows. Feeding of 7 to 10 g/d intestinally absorbable lysine had no effect on milk yield (
). An approximately 2-kg increment in milk yield was observed when RPL was added to the diet of dairy cows to supply from 15 to 21 g of additional intestinally absorbable lysine compared with the control diet (
In the present experiment, we did not observe milk yield differences when 9.68 g/d of metabolizable lysine was delivered to pre- and postpartum cows (P = 0.27, Figure 3F). Conversely,
reported that RPL increased milk yield, fat, true protein, and lactose yields. The discrepancy in milk yield and composition in response to RPL supplementation could be due to differences in the basal diets, methionine and lysine percentage of MP, and level of milk production (
). In our trial, we found a tendency for increased milk production at wk 3 after parturition in response to the HE diet and supplementation with RPL (P = 0.06). This result indicated that high-producing cows positively responded to RPL, which agrees with the report of
who reported that cows producing greater than 36 kg/d past peak lactation responded positively to supplementation of RPL. As DMI increased, the response to RPL appeared to support ECM yields over 45 kg/d (
). Similarly, we found that cows supplemented with RPL had numerically higher ECM than did unsupplemented cows. Conversely, low-producing cows (less than 36 k g/d of milk) did not respond positively to RPL supplementation (
found that supplementation of bypass lysine at 41 g/d in early and mid-lactation cows improved milk yield from 48 to 50 kg/d. In contrast, we did not observe milk yield differences in response to supplementation of RPL during the transition period. However, RPL supplementation had a tendency to improve milk yield at wk 3 after calving, which supports the theory that bypass lysine supplementation improves the efficiency of MP used for milk protein synthesis and increases milk yield (
Effects of rumen undegradable protein supplementation on productive performance and indicators of protein and energy metabolism in Holstein fresh cows.
demonstrated that supplementation of RUP immediately after calving improved milk yield.
Figure 3Effects of close-up dietary energy level and supplementing rumen-protected lysine (RPL; bypass lysine, Ascor Chimici Srl, Beijing) on milk yield, protein yield, and milk SCC during the transition period. Diets were high energy (NEL = 1.53 Mcal/kg of DM) with (HE-Lys) or without (HE) RPL (40 g/cow per day) or low energy (NEL = 1.37 Mcal/kg of DM) with (LE-Lys) or without (LE) RPL. Values are means; error bars represent standard error.
). In the current study, milk SCC were not affected by dietary energy levels or RPL or by their interactions (P = 0.44). However, the precalving LE diet had a tendency to reduce milk SCC compared with the precalving HE diet (P = 0.08, Figure 3C). We observed that time and energy interactions had a significant effect on milk SCC (P = 0.03). The highest SCC was recorded in cows fed the HE diet with RPL in the first week after calving and the lowest SCC was recorded in cows fed the LE diet only at wk 2 after calving (P = 0.44, Figure 3E). Supplementation of RPL did not affect milk SCC in this trial (P = 0.95, Figure 3D). In addition to mammary gland inflammation, cow productivity, health, parity, lactation stage, and breed of animal can also influence milk SCC concentrations (
The increase in milk SCC in cows fed the HE diet without RPL might be due to an influx of neutrophils into milk, as other associated factors, as was found by
Liver lipid content and inflammometabolic indices in peripartal dairy cows are altered in response to prepartal energy intake and postpartal intramammary inflammatory challenge.
in precalving cows being overfed dietary energy during the dry period. High-producing cows are under a form of stress due to milk production and their immunity can become reduced, leading to more SCC in their milk (
). Feeding RPL may contribute more support to high-producing cows, and they may not be under the same stresses as non–lysine-supplemented cows. Previous results demonstrated that immune suppression is often associated with a lack of energy or protein intake (
). Milk urea nitrogen content mainly depends on the nitrogen/energy ratio in the diet, but many other factors may affect ureagenesis. In this experiment, the precalving HE diet significantly decreased MUN by 18.7% (P < 0.01, Figure 1C), compared with cows fed the LE diet. Adequate energy in the diet may reduce MUN via proper rumen function (ammonia assimilation into microbial crude protein), postruminally absorbed energy (fatty acids), and rumen-escaped carbohydrate. On the other hand, a ration low in fermentable carbohydrate can reduce microbial growth due to lower energy available to the microbes, leading to higher MUN values.
Interaction of precalving energy levels and RPL significantly affected the concentration of MUN (P = 0.03, Figure 1F). Day and RPL interaction affected MUN (P = 0.04, Figure 1D). Reduction of MUN when RPL was added to the HE diet could have occurred because of optimum utilization of nitrogen with a highly fermentable energy supply. A reduction in MUN concentration can be indicative of lower amino acid catabolism by the mammary gland and overall improved whole-body N efficiency (
). Our observation of a decreased MUN with RPL addition to precalving HE diets suggested an improved efficiency of amino acid incorporation into protein, resulting in less amino acid deamination and urea synthesis.
Energy, RPL, and their interactions did not affect milk fat or lactose yields but feeding a precalving HE diet significantly increased milk protein yield by 6.5% compared with the control group (P = 0.03). The increase in milk protein yield in this study may be due to high starch levels in the HE diets, which favor glucose production to support milk protein synthesis.
Cows fed the LE diet with RPL had numerically higher milk fat yields compared with control group. The lower milk fat yield observed in cows fed LE without RPL supplementation was likely due to lower fiber digestibility, leading to reduced acetic and butyric acid production. Cows fed the HE diets with RPL also had numerically lower milk fat yields compared with controls. This finding may be due to a higher lysine percentage of MP in lysine-supplemented cows, as previous research has indicated that increasing the lysine percentage of MP also reduced milk fat when the methionine supply was deficient, or when the ratio of lysine to methionine was more than 3.0 (
Lysine supplementation had no effect on milk protein yield (P = 0.71, Figure 3B). Day and prepartum energy interaction tended to improve milk protein yield (P = 0.08), especially at wk 2 after calving; but cows fed LE had lower milk protein levels at wk 3. A precalving HE diet significantly affected protein yield (P = 0.03, Figure 3A). Cows fed the HE diet supplemented with RPL had numerically higher lactose yields than unsupplemented cows.
Energy, bypass lysine, and their interactions did not affect BCS (Table 3, Table 4). In our study, prepartum energy density did not affect BCS during pre- and postpartum periods. Similarly,
reported that prepartum feeding energy density (1.62 vs. 1.29 Mcal/kg of DM) did not impact pre- and postpartum BCS. Supplementation of rumen-protected lysine to the transition diet did not affect BCS (
). Similarly, we did not observe any significant difference in BCS in response to rumen-protected lysine in this study.
CONCLUSIONS
Feeding a precalving HE diet decreased both FFA and BHB concentrations in prepartum but not postpartum cows. An HE diet alone (1.53 Mcal/kg of DM) increased DMI, lowered MUN levels, tended to increase milk SCC, and reduced milk lactose percentage in postpartum cows. Cows supplemented with RPL had a tendency to produce higher milk yields from wk 1 to wk 3 after calving compared with unsupplemented cows. The interaction of precalving HE diet and RPL decreased BHB levels and MUN concentrations and tended to lower milk fat percentage in postpartum cows compared with the control group. We concluded that feeding RPL at a rate of 40 g/cow per day, which delivered 9.68 g/d of intestinally absorbable lysine, had beneficial effects on increasing DMI and reducing FFA and BHB concentrations in postpartum dairy cows during the transition period.
ACKNOWLEDGMENTS
We are very grateful to Gary Crow from the University of Manitoba (Canada) for his great contribution to the statistical analysis. We thank the National Key Research and Development Program of China (2018YFD0501600), the Agriculture Science and Technology Innovation Program (ASTIP-IAS07), the Chinese Academy of Agricultural Science and Technology Innovation project (CAAS-XTCX2016011-01), and the Beijing Dairy Industry Innovation Team (BAIC06-2019) for providing financial and technical support for this study.
REFERENCES
Alhussien M.N.
Dang A.K.
Milk somatic cells, factors influencing their release, future prospects, and practical utility in dairy animals: An overview.
Effects of rumen undegradable protein supplementation on productive performance and indicators of protein and energy metabolism in Holstein fresh cows.
Ardaillon, P., and C. Franzoni. 1992. Enzymatically degradable coating compositions for feed additives intended for ruminants. Rhone-Poulenc Santé, assignee. U.S. Pat. No. 5,098,718.
Liver lipid content and inflammometabolic indices in peripartal dairy cows are altered in response to prepartal energy intake and postpartal intramammary inflammatory challenge.
Effects of prepartal body condition score and peripartal energy supply of dairy cows on postpartal lipolysis, energy balance and ketogenesis: An animal model to investigate subclinical ketosis.
Far-off and close-up dry matter intake modulate indicators of immunometabolic adaptations to lactation in subcutaneous adipose tissue of pasture-based transition dairy cows.
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