Calf growth in captive Iberian red deer (Cervus elaphus hispanicus): effects of birth date and hind milk production and composition

This study examines effects of birth date, hind milk production and its composition, and weight of hind and calf at birth (HBW and CBW, respectively) on calf growth responses born to Iberian hinds (Cervus elaphus hispanicus) and lactating over 34 wk. Males showed daily gains greater than those of females (P = 0.04). Calf birth weight was strongly related to calf gain over a standard (15-wk) lactation (P < 0.01), but HBW did not influence growth or CBW (P > 0.10). After correcting for nutrient supply, birth date did not affect growth, but birth date x total protein yield (TPY), birth date x total fat yield (TFY), and birth date x total lactose yield (TLY) interactions influenced growth (P < 0.001), and early-born calves showed greater growth than those born late for wk 2 to 34 (P < 0.05). Calf birth weight showed the highest correlation with protein-to-fat ratio in milk (P < 0.001), a high correlation with milk protein content (P < 0.05), and a low negative correlation with fat (P < 0.10). Calf gains also showed the highest correlation with protein-to-fat ratio in milk (P < 0.05). Similarly, total milk yield (TMY), TPY, and TFY during lactation affected growth as single factors (P < 0.001). Calves showed not only an overall difference in daily gain between calves born early or late (P = 0.02), but also a greater speed of growth independently of CBW (percentage of weight gained per week, P < 0.001). Early-born calves were heavier at 12 and 18 mo (P < 0.05). Results suggest that selecting hinds of high milk production and nutrient supply and advancing calving date may increase growth of calves and their performance at adulthood.     

Milk yield of primiparous beef cows from three calving systems and varied weaning ages

Primiparous beef cows produced in 3 calving systems were used in a 2-yr study with a completely random design to measure milk yield throughout a 190-d lactation (2002, n = 20; 2003, n = 24 per calving system). Calving occurred in late winter (average calving date = February 4 +/- 2 d), early spring (average calving date = March 30 +/- 2 d), and late spring (average calving date = May 26 +/- 1 d). Additionally, cows used in this study had been weaned at varied ages as calves, creating 6 dam treatments. Dam age at weaning was 140 (late spring), 190 (late winter, early spring, late spring), or 240 (late winter, early spring) d of age. Milk production was measured by using the weigh-suckle-weigh technique at an average of 20, 38, 55, 88, 125, 163, and 190 d in milk. Milk yield for the 190-d lactation period was calculated as area under the curve by trapezoidal summation. Data were analyzed with a model containing treatment, year, and their interaction. Orthogonal contrasts were used to separate effects when treatment was significant (P < 0.10). Total milk yield did not differ (P = 0.42) between cows in the late winter and early spring systems, but cows in the late spring system tended to differ (P = 0.09) from the average of the other 2 systems. Cows in the late spring calving system had increased milk yield in 2002 and lesser milk yield in 2003 compared with the other calving systems (treatment x year interaction, P < 0.001). Cows born in late spring that had been weaned at 140 d of age produced more (P = 0.05) total milk than those weaned at 190 d of age. Peak milk yield was affected (P < 0.001) by treatment and showed a treatment x year interaction (P = 0.006). Day of peak lactation differed among treatments (P = 0.002), with cows in the late winter system peaking later (P = 0.007) than early spring cows, and late spring cows peaking earlier (P = 0.004) than the average of late winter and early spring cows. The average date of peak lactation was May 4 for the late winter system, May 31 for the early spring system, and July 19 for the late spring system. Calf ADG differed (P < 0.001) for the late spring system compared with the average of the late winter and early spring systems, but the relationship interacted with year (P < 0.001). Cow BW and BW change differed among treatments (P < 0.004), with much of the difference associated with the amount of milk produced or the timing of peak lactation. Season of calving affects milk yield of primiparous cows grazing Northern Great Plains rangelands and ADG of their calves.     

Influence of milk production potential on forage dry matter intake by multiparous and primiparous Brangus females

Brangus cows (n = 29) were used in three experiments to evaluate the effects of parity (multiparous vs. primiparous) and potential genetic merit for milk production (high vs. low) on forage intake during late gestation, early lactation, and late lactation. Cows were selected for milk production based on their sire's EPD for milk production (MEPD). Cows had ad libitum access to (130% of previous 2-d average intake) low-quality hay (5.3% CP and 76% NDF), and cottonseed meal was supplemented to ensure adequate degradable intake protein. All females were adapted to diets for at least 7 d, and individual intake data were collected for 9 d. During the lactation trials, actual milk production was determined using a portable milking machine following a 12-h separation from calves. During late gestation, multiparous cows consumed 24% more (P = 0.01) forage DM (kg/d) than primiparous cows; however, parity class did not influence forage intake when intake was expressed relative to BW. Furthermore, MEPD did not influence forage intake during late gestation. During early lactation, multiparous cows produced 66% more (P < 0.001) milk than primiparous cows, and high MEPD tended (P = 0.10) to produce more milk than low MEPD. Multiparous cows consumed 19% more (P < 0.0001) forage DM than did primiparous cows when expressed on an absolute basis, but not when expressed on a BW basis. High-MEPD cows consumed 8% more (P < 0.05) forage DM than did low-MEPD cows. During late lactation, multiparous cows produced 84% more milk than primiparous cows, although MEPD did not influence (P = 0.40) milk yield. In addition, multiparous cows consumed 17% more (P < 0.01) forage DM per day than primiparous cows, but when intake was expressed relative to BW, neither parity nor MEPD influenced forage DMI during late lactation. Milk yield and BW explained significant proportions of the variation in forage DMI during early and late lactation. Each kilogram increase in milk yield was associated with a 0.33- and 0.37-kg increase in forage DMI for early and late lactation, respectively. Results suggest that multiand primiparous cows consume similar amounts of low-quality forage DM, expressed per unit of BW, during late gestation and lactation. Selecting beef cows for increased genetic merit for milk production increases forage DMI during early lactation.     

Lactation curves in captive Iberian red deer (Cervus elaphus hispanicus)

This study examines milk production and the effect of milk production and sex of calf on body weights and gains of red deer calves and hinds of the Iberian subspecies (Cervus elaphus hispanicus). Milk production was assessed in 14 hinds by weighing calves before and after suckling and by adjusting these values to the Gamma function. Gamma estimates of total milk production up to d 105 were similar to the amounts computed directly from double weighing. Hinds showed two types of lactation curve: 1) the standard mammal lactation curve, with an asymmetrical peak at wk 2 to 4 (Type I) and 2) decreasing curves with no peak (Type II). Although there was great interindividual variability, hinds with Type I curves showed a trend to produce more milk than those with Type II. The type of curve did not seem to affect weight variables of the calf or those of the dam. Calves that gained more weight consumed greater amounts of milk (P<.05). Males were heavier than females at birth (P<.05), but males did not differ from females in their weight at 105 d, milk consumption, and gain. Gender did not affect hind weight, but dams of male calves showed a trend to be lighter (P = .063) at d 105 than dams of female calves. Our results suggest that suckling differences found in other studies between male and female calves may not involve differences in milk production, although other rearing costs seem to affect hind weight losses. They also suggest that the curve type may not depend only, as reported, on the nutrition plane.     

Effect of fat supplementation during transition period on plasma leptin and non‐esterified fatty acid concentrations in Holstein cows

The objective of this experiment was to investigate the effect of fat supplementation during the transition period on pre and postpartum body weight (BW), body condition score (BCS), non‐esterified fatty acids (NEFA), glucose and leptin concentrations in Holstein cows. Holstein cows (n = 15) received a low fat diet (LF; 1.61 Mcal net energy for lactation (NEL)/kg of dry matter [DM]), moderate fat diet (MF; 1.68 Mcal NEL/kg DM) or a high fat diet (HF; 1.74 Mcal NEL/kg DM) for 4 weeks prior to calving. All cows were fed similar lactation diets ad libitum (1.74 Mcal NEL/kg DM) for 30 days after calving. Increasing diet energy density during transition period had no effect on prepartum DMI, BCS, BW, glucose and NEFA concentrations (P > 0.05); but leptin concentrations and energy balance (EB) were affected by treatments (P < 0.05). Animals fed HF had less plasma leptin prepartum. After parturition, BW, milk production, milk fat, protein, urea nitrogen and plasma glucose concentrations were affected by prepartum diets (P < 0.05). Fat supplementation prepartum did not affect postpartum NEFA. In conclusion, prepartum fat supplementation decreased leptin concentration prepartum.     

Supplementation of dried distillers grains with solubles to beef cows consuming low-quality forage during late gestation and early lactation

Three experiments were conducted to evaluate supplementation of dried distillers grains with solubles (DGS) to spring-calving beef cows (n = 120; 541 kg of initial BW; 5.1 initial BCS) consuming low-quality forage during late gestation and early lactation. Supplemental treatments included (DM basis) 1) 0.77 kg/d DGS (DGSL); 2) 1.54 kg/d DGS (DGSI); 3) 2.31 kg/d DGS (DGSH); 4) 1.54 kg/d of a blend of 49% wheat middlings and 51% cottonseed meal (POS); and 5) 0.23 kg/d of a cottonseed hull-based pellet (NEG). Feeding rate and CP intake were similar for DGSI and POS. In Exp. 1, cows were individually fed 3 d/wk until calving and 4 d/wk during lactation; total supplementation period was 119 d, encompassing 106 d of gestation and 13 d of lactation. Tall-grass prairie hay (5.6% CP, 50% TDN, 73% NDF; DM basis) was fed for ad libitum intake throughout the supplementation period. Change in cow BW and BCS during gestation was similar for DGSI and POS (-5.0 kg, P = 0.61 and -0.13, P = 0.25, respectively) and linearly increased with increasing DGS level (P < 0.01). Likewise, during the 119-d supplementation period, BW and BCS change were similar for DGSI and POS (-72 kg, P = 0.22 and -0.60, P = 0.10) and increased linearly with respect to increasing DGS (P < 0.01). The percentage of cows exhibiting luteal activity at the beginning of breeding season (56%, P = 0.31), AI conception rate (57%, P = 0.62), or pregnancy rate at weaning (88%, P = 0.74) were not influenced by supplementation. In Exp. 2, 30 cows from a separate herd were used to evaluate the effect of DGS on hay intake and digestion. Supplementation improved all digestibility measures compared with NEG. Hay intake was not influenced by DGS (P > 0.10); digestibility of NDF, ADF, CP, and fat linearly increased with increasing DGS. In Exp. 3, milk production and composition were determined for cows (n = 16/treatment) of similar days postpartum from Exp. 1. Daily milk production was not influenced by supplementation (6.3 kg/d, P = 0.25). Milk fat (2.1%) and lactose (5.0%) were not different (P > 0.10). Milk protein linearly increased as DGS increased (P < 0.05) and was greater for DGSI compared with POS. Similar cow performance was achieved when cows were fed DGS at the same rate and level of CP as a traditional cottonseed meal-based supplement. Increasing amounts of DGS did not negatively influence forage intake or diet digestibility.     

Influence of calf genotype on dam lactation and calf growth in farmed red deer (Cervus elaphus)

Multiparous red deer (Cervus elaphus scoticus) hinds (n=17) were either mated to a red deer stag or artificially inseminated with semen from a wapiti bull (C.e. nelsoni) to produce red deer or F₁ crossbred (C.e. scoticus × C.e. nelsoni) calves to test the hypotheses that (1) red deer hinds rearing crossbred calves will produce significantly more milk to support calf growth than hinds rearing red deer calves, and (2) hind live weight and body condition may suffer as a result. Hinds and calves were grazed on ryegrass and white clover pastures and supplemented with pasture silage and barley grain when pasture supply was inadequate. Calves were left with their mothers until 9–10 months of age when lactation had terminated naturally. Mean body condition score (BCS) loss was greater in hinds rearing F₁ calves than in hinds rearing red calves in the period from late gestation to mid-lactation (September–March, P<0.05). F₁ calves grew significantly faster than red deer calves and were heavier at all ages. From February onwards there was a consistent decline in milk intake, and by the latest measurement (22 July) milk production was negligible, and most hinds had ceased lactating. Milk intake by the F₁ calves was significantly greater until day 114, after which the measured milk intake was not significantly different. Pasture intake of the F₁ calves was significantly greater at day 114 but not at other times (P<0.05). The average hind pasture intake was also not significantly affected by calf genotype when adjusted for post calving hind live weight. The results support the hypothesis that a red deer hind rearing an F₁ calf produces significantly more milk than a hind rearing a red deer calf, suggesting that the growth of a red deer calf is limited by its milk demand rather than milk supply by the hind. The study also supported the second hypothesis. Hinds rearing F₁ calves exhibited greater losses of body condition score relative to the hinds rearing red deer calves, indicating that the hinds rearing F₁ calves were in a greater negative energy balance that hinds rearing red deer calves. This highlights the additional energetic demands on a hind from feeding an F₁ calf and in a farmed context the need to ensure that adequate nutrition is provided.     

Effect of milking frequency in early lactation on energy metabolism, milk production and reproductive performance of dairy cows

The objective of this study was to evaluate the effect of imposing different milking frequencies for the first 4 weeks of lactation on energy balance, blood metabolic profiles and reproductive performance. The milking frequencies imposed were once daily for the first 4 weeks of lactation and twice daily subsequently (X1), twice daily for the entire lactation (X2) and three times daily for the first 4 weeks of lactation and twice daily subsequently (X3). Two weeks prior to the first expected calving date, sixty-three multiparous, Holstein-Friesian cows, were allocated to treatments based on expected calving date, parity (lactation number = 2 and lactation number > 2), BCS and BW. Mean DMI was lower (P < 0.05) on X1 than X2 (15.7 and 17.1 kg/day) over the first 4 weeks of lactation, but DMI on X3 was not different to either. Milk yield was lower (P < 0.05) on X1 than on X2 and X3 (24.1, 31.9 and 31.4 kg/day) from weeks 1 to 4 and at week 10 of lactation (30.9, 33.9 and 33.7 kg/day) but was not different at week 20. Yield of milk constituents followed the same pattern as milk yield. Milking frequency had no significant effect on milk fat or protein concentration but milk lactose concentration was higher (P < 0.05) on X1 than on X2. Cows on X1 experienced less (P < 0.05) negative energy balance than those on X2 and X3 from weeks 1 to 4, with no difference between X2 and X3. Cows on X1 lost less BW (P < 0.05) from weeks 1 to 4 and lost less BCS up to day 73 of lactation than cows on X2 and X3. Plasma NEFA and BHB concentrations tended to be lower and plasma glucose tended to be higher on X1 than on X2 and X3 from weeks 1 to 4, while plasma insulin was higher on X1 than on X2 and X3 for the first 2 weeks of lactation. There was no difference between treatments in any reproductive performance variable measured. These results indicate that reduced milking frequency decreases milk yield and improves energy balance and metabolic status in early lactation.     

Lactoferrin concentration and expression in New Zealand cows milked once or twice a day

This study evaluated the concentration and expression of lactoferrin (LF) in cows selected for once a day (OAD) milking compared to twice a day (TAD) milking. Milk samples were collected from the Massey University TAD and OAD herds. Milk traits and expression of LF and insulin‐like growth factor 1 (IGF‐1) were analyzed with a general linear model that included the fixed effects of milking frequency, lactation number, interaction between milking frequency and lactation number, and as covariates proportion of F, heterosis F × J and deviation from the herd median calving date. Cows milked OAD produced milk with higher (p < .01) concentrations of protein and lactose than TAD milked cows. Compared to TAD cows, cows milked OAD had higher expression of the LF gene (1.40 vs. 1.29 folds, p = .03) and the IGF‐1 gene (1.69 vs. 1.48 folds, p = .007). The correlation between the expression of LF gene and the concentration of LF in milk was strong (r = .66 p < .001), but the correlation between the expression of the IGF‐1 gene and LF concentration was stronger (r = .94, p < .001). These results suggest that milking frequency affects the milk composition and expression of milk composition genes at early lactation.     

Predicting milk yield and composition in lactating sows: a Bayesian approach

The objective of this study was to develop a framework describing the milk production curve in sows as affected by parity, method of milk yield (MY) determination, litter size (LS), and litter gain (LG). A database containing data on LS, LG, dietary protein and fat content, MY, and composition measured on more than 1 d during lactation and method for determining MY from peer reviewed publications and individual sow data from 3 studies was constructed. A Bayesian hierarchical model was developed to analyze milk production data. The classical Wood curve was used to model time trends in MY during lactation, and it was re-parameterized expressing the natural logarithm of MY values at d 5, 20, and 30 as functional parameters. The model incorporated random effects of experiment, sow nested within experiment, and fixed effects of LS, LG, parity, and method through the functional parameters of the Wood curve. A second set of models were constructed to analyze milk composition data, including day in milk, LS, dietary protein, and fat contents. Four scenarios with different LG and LS were constructed using the framework to estimate the energy output in milk at different days during lactation. The estimated energy output was compared with energy output values calculated using the 1998 NRC method. Milk yield was underestimated by approximately 20% with the weigh-suckle-weigh technique compared with the deuterium oxide dilution technique (P < 0.001). The mean LG and LS for the dataset were 2.05 kg/d (1.0; 3.3) and 9.5 piglets (5; 14), respectively. The MY was affected by LS on d 5 and 20 (P < 0.001) and by LG on d 20 (P < 0.001) and d 30 (P = 0.004). The mean time to peak lactation was 18.7 d (SD = 1.06) postpartum and mean MY at peak lactation was 9.23 kg (SD = 0.14). The average protein, lactose, and fat content of milk was 5.22 (SD = 0.06), 5.41 (SD = 0.08), and 7.32% (SD = 0.17%), respectively. The NE requirement for lactation increased from d 5 to 20 because of increased MY. Requirements also increased with increasing LG and LS. The framework could be used to predict energy and protein requirements for lactation under different production expectations and can be incorporated into a whole animal model for determination of energy and nutrient requirements for lactating sows, which can optimize sow performance and longevity.     

Effects of peripartum biotin supplementation of dairy cows on milk production and milk composition with emphasis on fatty acids profile

Forty Holstein dairy cows receiving a 38% concentrate diet based on maize silage were assigned to either a control group, either a biotin group, receiving 20 mg of biotin per day from 15 days before expected calving date and for 120 days after calving. Milk production was measured daily, milk fat content, protein content, urea and somatic cell counts were determined weekly from week 2 to week 17 of lactation. The profile of milk fatty acids was determined at weeks 3 and 10. Plasma glucose and blood beta-hydroxybutyrate were determined before calving and at weeks 1, 2, 3, 5, 7 and 10 of lactation.

Biotin supplementation resulted in an increased milk production in multiparous cows during weeks 2 to 6, but the effect was no more significant between 7 and 17 weeks of lactation. Milk protein percent was decreased by 0.1% in multiparous cows. Milk fat content was not affected by biotin, and milk fat daily production tended to increase during early lactation. In milk fat, biotin supplementation tended to decrease the proportion of fatty acids with less than 16 carbons at week 3, but the daily amount was not affected. Biotin tended to decrease biohydrogenation intermediates, increased C16:1 at week 3, and tended to increase cis-9 C18:1 at weeks 3 and 10. After 7 weeks of lactation, biotin tended to increase blood beta-hydroxybutyrate in multiparous cows with values remaining in a normal range, and decreased plasma glucose in primiparous cows. These modifications of plasma parameters, milk protein content and profile of milk fatty acids could be due to a higher lipid mobilisation from adipose tissue driven by the increased milk production.     

Effect of reduced energy density of close-up diets on dry matter intake,lactation performance and energy balance in multiparous Holstein cows

Energy intake prepartum is critically important to health,milk performance,and profitability of dairy cows.The objective of this study was to determine the effect of reduced energy density of close-up diets on dry matter intake(DMI),lactation performance and energy balance(EB) in multiparous Holstein cows which were housed in a free-stall bam and fed for ad libitum intake.Thirty-nine dry cows were blocked and assigned randomly to three groups fed a high energy density diet[HD,n = 13;6.8 MJ of net energy for lactation(NE_L)/kg;14.0%crude protein(CP)],or a middle energy density diet(MD,n = 13;6.2 MJ NE_L/kg;14.0%CP),or a low energy density diet(LD,n = 13;5.4 MJ NE_L/kg;14.0%CP) from d 21 before expected day of calving.After parturition,all cows were fed the same lactation diet to d 70 in milk(DIM).The DMI and NE_L intake prepartum were decreased by the reduced energy density diets(P 0.05).The LD group consumed 1.3 kg/d(DM) more diet compared with HD group in the last 24 h before calving.The milk yield and the postpartum DMI were increased by the reduced energy density diet prepartum(P 0.05).The changes in BCS and BW prepartum and postpartum were not affected by prepartum diets.HD group had higher milk fat content and lower lactose content compared with LD group during the first 3 wk of lactation(P 0.05).The energy consumption for HD,MD and LD groups were 149.8%,126.2%and 101.1%of their calculated energy requirements prepartum(P 0.05),and 72.7%,73.1%and 75.2%during the first 4 wk postpartum,respectively.In conclusion,the low energy density prepartum diet was effective in controlling NE_L intake prepartum,and was beneficial in increasing DMI and milk yield,and alleviating negative EB postpartum.     

Artificial long-day photoperiod in the subtropics increases milk production in goats giving birth in late autumn

Two experiments were conducted to determine whether exposure to a photoperiod of artificial long days in autumn increased milk yield in subtropical goats milked once (Exp. I) or twice daily (Exp. II). In Exp. I, starting at d 10 of lactation, 1 group of does was kept under naturally decreasing photoperiod (DD1X; n = 8), whereas the other group was submitted to an artificial photoperiod of long days (LD1X; n = 8; 16 h light:8 h darkness). The kids were weaned 28 d after parturition, and dams were manually milked once daily. Milk yield and milk components (fat, protein, and lactose) were assessed up to 140 d of lactation. From d 0 to 28 of lactation (suckling phase), mean daily milk yield did not differ between DD1X and LD1X goats (2.3 ± 0.2 kg vs. 2.4 ± 0.2 kg; P = 0.717). However, between d 29 and 84 (early milking phase), mean daily milk yield was greater in LD1X does than in DD1X does (2.6 ± 0.1 kg vs. 2.1 ± 0.1 kg; P = 0.001). Finally, between d 85 and 140 (late milking phase), mean daily milk yield was greater in LD1X goats than in DD1X goats (P ≤ 0.05) only during the first 2 wk. In Exp. II, one group of goats was exposed to a photoperiod of naturally decreasing days (DD2X; n = 8) and another group was submitted to an artificial photoperiod of long days (LD2X; n = 7). In both groups, kids were weaned on d 28 of lactation and the dams were manually milked twice daily. During the nursing phase, mean daily milk yield did not differ between the DD2X and LD2X groups (2.5 ± 0.3 kg vs. 2.6 ± 0.2 kg; P = 0.767). In the early milking phase, mean daily milk yield was greater in LD2X than in DD2X goats (3.3 ± 0.2 kg vs. 2.8 ± 0.2 kg; P = 0.022), whereas during the late milking phase, milk yield did not differ between the 2 groups (P = 0.946). In both experiments, milk composition was not significantly influenced by exposure to long-day photoperiod. We conclude that, in subtropical female goats that start lactation in late autumn, exposure to an artificial long-day photoperiod stimulates milk yield, even if goats are milked once daily. In addition, combining exposure to long days with twice-daily milking will increase further milk yield in such goats without affecting milk components.     

Evaluation of maternal performance of daughters from high and low milk EPD sires

Angus bulls (n = 24) were selected for either high or low milk EPD, but with similar growth EPD and mated within location (n = 6) at random to Angus cows. Daughters from these matings were bred to calve first at 2 yr of age to common reference sires across locations. Lactation records for 192 daughters were used to evaluate 12-h milk yield, percentage of milk fat and protein, and weaning weight of offspring. Milk production was measured four times during the lactation at regular intervals within location. Dams were separated from their calves the night before milking and milked with a portable milking machine the next morning to estimate 12-h milk yield. A sample of the milk was collected from each cow and analyzed for percentages of milk fat and protein. Data were analyzed as repeated records of the dam. Fixed effects were location, genetic line of sire, gender of calf within location, and milking period, with postpartum interval used as a covariate. Fixed effects and the random effects of sire of dam nested within line, sire of calf, and year were estimated by REML. Genetic line was an important source of variation for milk yield (P < 0.01) and percentage of milk fat (P = 0.03) but not for percentage of milk protein (P = 0.49). Location was significant for all three milk variables (P < 0.01), but the interactions between line and location were not significant. Gender of calf was significant for milk yield (P = 0.04) but not for percentage of milk fat or protein. Line (P = 0.02), location (P = 0.01), calf gender (P = 0.01), and age at weaning (P = 0.01) were significant sources of variation for weaning weight but the interaction of line and location was not (P = 0.69). The correlation coefficient between the sire's milk EPD and 12-h milk yield was significantly different from zero (r = 0.56). The difference between the least squares means for high and low lines for milk yield was 0.66 kg/12 h and the difference was 15.3 kg for weaning weight. The results indicate that there was not evidence for a genotype by environment interaction in milk production for daughters from divergent sires selected for high or low milk EPD.     

产犊季节、胎次及牛场对荷斯坦牛泌乳性能的影响

本研究收集了3个千头以上奶牛场共8872条相关信息,采用多因素方差分析法分析了不同产犊季节、胎次和牛场对泌乳天数、305d校正奶量、305d脂肪产量、305d蛋白产量和全泌乳期产奶量5个泌乳性能指标的影响。结果表明,不同产犊季节、胎次和牛场都极显著影响奶牛的该5项泌乳性能（P〈0．01）。夏季和秋季产犊奶牛的泌乳性能较为理想。夏季产犊奶牛的泌乳天数和全泌乳期产奶量最高,其他三个泌乳性能指标都位居第二;秋季产犊奶牛的305d校正奶量、脂肪产量和蛋白产量都显著高于其他三个季节（P〈0．05）,泌乳天数和全泌乳期产奶量也仅次于夏季。头胎牛的各项泌乳性能都显著高于其他胎次的奶牛（P〈0．05）,其次为2胎产犊奶牛。随着胎次的增加,泌乳性能的各项指标都有不同程度的降低。不同的牛场极显著地影响奶牛的泌乳性能（P〈0．01）。     

Effects of different starch sources on metabolic profile, production and fertility parameters in dairy cows

The objective of the study was to determine the effect of replacing triticale (high rumen degradable starch) with maize grain (low rumen degradable starch) during the transition period and the first 120 days of lactation on metabolic and hormonal profile indices, milk production and fertility performance in cows. Forty-eight Holstein-Friesian dairy cows were divided into 4 groups: TT (2.5 kg triticale grain/cow per day supplemented from 14 days prepartum to day 120 postpartum), TM (2.5 kg triticale grain/cow per day supplemented from day 14 before parturition to calving, and then 2.5 kg maize grain to 120 days of lactation), MT (2.5 kg maize grain/cow per day supplemented from day 14 before parturition to calving, and then 2.5 kg triticale grain to 120 days of lactation), MM (2.5 kg maize grain/cow per day supplemented from 14 days prepartum to day 120 postpartum). Blood samples were collected 3 weeks and 1 week before calving and on days 14, 56 and 70 of lactation, and they were analyzed in terms of concentrations of glucose, insulin, leptin, insulin-like growth factor I, nonesterified fatty acids, triglycerides, cholesterol, blood urea nitrogen and activities of aspartate aminotransferase and gamma glutamyl transpeptidase. Milk samples were collected twice a day at weekly intervals and analyzed for fat, protein and lactose. Milk yield and individual dry mater intake were recorded at weekly intervals. Body condition was estimated 3 weeks before calving, on parturition day and on days 14, 56 and 120 of lactation. Replacing triticale grain with maize grain in the transition period and during lactation positively affected fertility of lactating cows. An increased first service conception rate and shortening of the days open period was observed in MM and TM groups in comparison to those found in group MT (P < or = 0.05). The lowest number of services per conception was recorded in groups MM and TM (P < or = 0.05). Although the impact of milk production and the most of the blood indices were not significantly affected by this treatment, the results of the study suggest that maize grain in the transition period and lactation might be a more effective energy source for dairy cows than triticale grain.     

甜菜碱对奶牛采食量、泌乳性能和血液指标的影响

选用20头体重(597±11.8)kg、泌乳天数(88±4.5)d、日产奶(26.3±0.5)kg的经产奶牛,随机分为4组,采用4×4拉丁方设计,研究甜菜碱(0、50、100和150g/d)对泌乳早期奶牛采食量、泌乳性能和血液指标的影响。结果表明:日粮添加甜菜碱对奶牛的采食量、乳蛋白率、乳糖率和血糖浓度无显著影响,100g/d组和150g/d组鲜奶产量显著高于对照组和50g/d组(P<0.05);100g/d组和150g/d组4%乳脂校正乳、能量校正乳和乳脂产量显著高于对照组(P<0.05);100g/d组乳脂率显著高于对照组(P<0.05);100g/d组和150g/d组血浆游离脂肪酸和β-羟丁酸浓度显著低于对照组(P<0.05)。根据以上结果推断,甜菜碱的适宜添加水平为100g/d。     

Estimation of genetic parameters for milk and fertility traits within and between low,medium and high dairy production systems in Kenya to account for genotype-by-environment interaction

Dairy records from the Dairy Recording Service of Kenya were classified into low, medium and high production systems based on mean 305-day milk yield using the K-means clustering method. Milk and fertility records were then analysed to develop genetic evaluation systems accounting for genotype-by-environment interaction between the production systems. Data comprised 26,638 lactation yield, 3,505 fat yield, 9,235 age at first calving and 17,870 calving interval records from 12,631 cows which were descendants of 2,554 sires and 8,433 dams. An animal model was used to estimate variance components, genetic correlations and breeding values for the production systems. Variance components increased with production means, apart from genetic group variances, which decreased from the low to the high production system. Moderate heritabilities were estimated for milk traits (0.21–0.27) and fat traits (0.11–0.38). Low heritabilities were estimated for lactation length (0.04–0.10) and calving interval (0.03–0.06). Moderate heritabilities (0.25–0.26) were estimated for age at first calving, except under the high production system (0.05). Within production systems, lactation milk yield, 305-day milk yield and lactation length had high positive genetic correlations (0.52–0.96), while lactation milk yield and lactation length with age at first calving had negative genetic correlations. Milk yield and calving interval were positively correlated except under the low production system. The genetic correlations for lactation milk yield and 305-day milk yield between low and medium (0.48 ± 0.20 and 0.46 ± 0.21) and low and high production systems’ (0.74 ± 0.15 and 0.62 ± 0.17) were significantly lower than one. Milk yield in the low production system is, therefore, a genetically different trait. The low genetic correlations between the three production systems for most milk production and fertility traits suggested that sires should be selected based on progeny performance in the targeted production system.     

产犊季节、胎次及牛场对荷斯坦牛泌乳性能的影响

[目的]研究产犊季节、胎次及不同牛场对奶牛泌乳性能的影响情况,以期为提高奶牛的泌乳性能及牛奶质量提供可靠的理论依据。[方法]收集3个千头以上奶牛场共8 872次相关信息,用多因素方差分析法分析产犊季节、胎次和牛场对泌乳天数、305d校正奶量、305d脂肪产量、305d蛋白产量和全泌乳期产奶量5个泌乳性能的影响进行分析。[结果]不同产犊季节、胎次和牛场都极显著影响奶牛的5项泌乳性能(P<0.01)。夏季和秋季产犊奶牛的泌乳性能较为理想。夏季产犊奶牛的泌乳天数和全泌乳期产奶量最高,其他三个泌乳性能都位居第二;秋季产犊奶牛的305d校正奶量、脂肪产量和蛋白产量都显著高于其他三个季节(P<0.05),泌乳天数和全泌乳期产奶量也仅次于夏季。头胎牛的各项泌乳性能都显著高于其他胎次的奶牛(P<0.05),其次为2胎产犊奶牛。随着胎次的增加,泌乳性能的各项指标都有不同程度的降低。除了泌乳天数之外,A牛场的各项泌乳性能都最佳,且显著高于B、C两个奶牛场(P<0.05)。[结论]在饲养条件良好的情况下,本研究中三个牛场的奶牛适宜在夏、秋两个季节产犊,此时泌乳性能较好;此外,头胎产犊奶牛的泌乳性能在各胎次中最高。     

Quantitative and qualitative assessment of milk production after pharmaceutical induction of lactation in the mare

The induction of lactation is performed in ruminants by steroidogenic impregnation, followed by drugs intended to increase prolactin secretion. The aim of this study was to induce lactation in barren mares and to evaluate milk production. Five treated and 5 control mares were used in June and September in year 1, and 12 mares were used in year 2. Mares were administered a vaginal pessary (500 mg altrenogest and 50 mg estradiol benzoate) for 1 week. The 2nd week, another sponge with 100 mg estradiol benzoate was administered, together with 50 mg/100 kg body weight (BW) sulpiride in oil (IM q12h). All mares were milked by hand. Drug treatment was stopped after I L was obtained. Milk production and composition and plasma prolactin concentration were measured. In year 2, the same steroid treatment was applied, but mares received sulpiride (n = 6) or domperidone (1.1 mg/kg PO q12h) (n = 6). A milking machine and oxytocin injections 1 minute before the start of milking were used. In year 1, all treated mares started milking within 1-5 days after sulpiride treatment. Mean daily milk production was 0.88 +/- 0.52 L/500 kg BW. Milk immunoglobulin G (IgG) contents increased in all mares (IgG concentration range, 14-92 g/L). Plasma prolactin increased during sulpiride treatment (range. 27.7 +/- 2.9 to 43.7 +/- 6.7 ng/mL [before] to 289.0 +/- 7.8 ng/mL during treatment, P < .001). In year 2, results were similar to those in year 1, with peak IgG concentrations ranging from 4.2 to 106.7 g/L and a larger daily milk production (3.13 +/- 0.75 with sulpiride and 3.45 +/- 0.51 L/500 kg BW with domperidone). In conclusion, lactation can be induced in mares within 2 weeks, and some mares produce good-quality colostrum.