The change of dry matter intake, milk yield and bone turnover in primiparous cows compared to multiparous cows during early lactation

Data from six primiparous and nine multiparous Holstein cows were used to clarify the difference of Ca and P mobilization between primiparous and multiparous cows during early lactation. The dry matter intake (DMI) of primiparous cows was lower (P < 0.01) than those of multiparous cows. Milk yield was lower in primiparous cows at 7, 14, 21 (P < 0.01), and 28 days (P < 0.05) after parturition. There was no significant difference in milk Ca and P concentrations between primiparous and multiparous cows. There were no significant differences in plasma Ca and P concentrations between primiparous and multiparous cows. The plasma P level at 7 days postpartum in primiparous cows was lower (P < 0.05) than 28 days postpartum. The concentration of plasma osteocalcin (OC) measured as bone formation marker of primiparous cows was significantly higher than multiparous cows (P < 0.01) at 21 and 28 days postpartum. The urinary deoxypyridinoline (DPD) as bone resorption marker of primiparous cows tended to be higher (P < 0.10) than multiparous cows at 21 days after parturition and decreased to the same level as that of multiparae toward the peak lactation. These results show that Ca and P mobilization of primiparous cows are more active than multiparous cows.     

Estimation of nutritive value and dry matter intake of forage

Since the 1900s, proximate analysis has been the mainstream method of feed analysis. In addition to this method, the detergent method, which was developed in the 1960s, has become a popular methodology for feed composition and nutritive value evaluation. One fundamental characteristic of this method is that fractionated carbohydrates are classified as either the fiber of feed in terms of neutral detergent fiber (NDF) or non‐fiber carbohydrates (NFC), which include sugar and starch. Meanwhile, in Japan another method, the enzymatic method, has been developed. The characteristic of this method is that fractionated carbohydrates are classified as either the fiber contained in feed in terms of organic cell wall (OCW) or nitrogen‐cell wall free extracts (NCWFE, non‐structural carbohydrates). One important fraction of feed nutrition is digestible carbohydrates, which are the sum of digestible non‐structural carbohydrates and the digestible fiber. The content of digestible non‐structural carbohydrates is obtained based on the nutritional uniformity of NFC and NCWFE in the detergent and enzymatic method, individually. The digestible fiber is obtained in the detergent method from the potential digestibility of NDF and lignifications, and obtained in the enzymatic method from the highly digestible organic a fraction and the poorly digestible organic b (Ob) fraction. The amount of digestible carbohydrates obtained by these two methods of analysis is sometimes significantly different. The Ob fraction obtained by the enzymatic method shows a significant negative correlation, and a 1% increase in the Ob content of hay dry matter suppresses the dry matter intake of dairy cattle by 0.17 kg.     

Effect of lactation and rebreeding phase energy intake on primiparous and multiparous sow performance

Fifty-three primiparous sows were used to study the effects of a high-energy, fat-supplemented diet on sow lactation and rebreeding performance. Sows received either a low [Lo, 12.5 Mcal metabolizable energy (ME)/d] or high (Hi, 16.0 Mcal ME/d) energy sorghum-soybean diet during a 28-d lactation. At weaning, sows were randomly allotted, within lactation treatment, to a low (lo, 5.54 Mcal ME/d) or high (hi, 9.61 Mcal ME/d) energy sorghum-soybean diet until the day of first postweaning estrus. Primiparous sows fed Lo weaned larger (P less than .05) litters than sows fed Hi; however, average pig weight was not affected by lactation treatments. Primiparous sows fed Hi had more backfat at weaning (P less than .01) than Lo sows. In contrast, sow weight was not affected by dietary treatments. Neither lactation nor rebreeding treatments influenced days to rebreeding; however, an interaction (P less than .01) was observed. Mean days from weaning to rebreeding for Lolo, Lohi, Hilo and Hihi sows were 10.0, 7.6, 6.9 and 17.1, respectively. Forty sows were maintained on the same dietary treatments during their second parity. Sows receiving Lo during their second parity farrowed and weaned more (P less than .05) pigs than Hi sows. Multiparous sows fed Hi nursed heavier (P less than .05) pigs on d 21 of lactation and at weaning compared with Lo sows. Sows fed Hi were heavier (P less than .05) and had more (P less than .01) backfat at weaning of their second litter compared to Lo sows. Days to postweaning estrus were not affected by lactation or rebreeding diets. Mean length of the second parity rebreeding interval for Lolo, Lohi, Hilo and Hihi sows was 6.2, 10.2, 7.0 and 10.5 d, respectively. These results suggest that feeding levels during lactation of 12.5 Mcal ME/d or higher supported adequate rebreeding performance. Postweaning feeding levels did not influence days to first estrus. Feeding a high energy diet continuously throughout the lactation and rebreeding phases in primiparous sows may lengthen the postweaning interval to estrus.     

Colostrum production by primiparous and multiparous Holstein dairy cows and its usefulness as an estimator of full lactation milk yield

This study determined colostrum production of lactating primiparous and multiparous Holstein dairy cows, as well as the predictability of full lactation milk yield based upon this colostrum production. Holstein cows that calved between December 18, 2006 and December 24, 2007 (n = 134) had their first two post-partum milkings weighed and assayed for density. Cows then entered normal production groups and were assessed for milk yield and milk components every 4 or 5 weeks for the duration of their lactation. Primiparous cows produced less colostrum (10.6 versus 13.6 kg; P = 0.02) and density adjusted (DA) colostrum (5.2 versus 8.5 kg; P < 0.01), but there were no differences in estimated 305 day mature equivalent (305ME) milk production (mean = 13,654 kg) or lactation lengths (mean = 301 days) between parities. Colostrum and DA colostrum were poor estimators of subsequent 305ME milk production within primiparous cows (r² = 0.20 and 0.01 respectively) and multiparous cows (r² = 0.18 and 0.12 respectively). Colostrum production of these high producing cows was somewhat lower than expected, highly variable among cows within parity, higher for multiparous versus primiparous cows, and was not a good estimator of subsequent 305ME milk production.     

Sorghum silage supplemented with crambe meal improves dry matter intake and milk production in crossbred Holstein cows

We studied the feed intake and milk production of Holstein × Zebu crossbred cows fed sorghum silage diets and concentrates, with and without the addition of crambe meal. Using a change-over design for a total of 120 days, eight cows were fed two diets (concentrates + silages with and without crambe meal) in four 30-day periods, with four replications (animals). The crambe meal diet increased (P < 0.05) the dry matter intake (DMI), crude protein intake (CPI), and non-fibrous carbohydrates intake (NFCI) as well as milk production (4.3%). No difference was noted (P > 0.05) for the milk composition between the treatments. Crambe meal as an additive in sorghum silage (100 g/kg in natural matter) showed a great potential for introduction in dairy farming as it substantially increases CP intake, does not reduce food intake, raises animal productivity, and does not affect milk composition.     

Relationship between water intake, dry matter intake and daily milk yield on a German research farm

The aim of the present study was to investigate the relationship between milk yield, water and dry matter intake and to clarify whether these relationships remained constant over the stages of lactation. Data recording was performed on the dairy research farm Futterkamp of the Chamber of Agriculture Schleswig-Holstein. A dataset of about 39,000 observations from 225 Holstein cows was used. Average milk yield, water and dry matter intakes were 34.9, 84.3 and 20.3 kg, respectively. Estimations of variance components were accomplished by applying linear mixed Fixed Regression (FR) and Random Regression (RR) models. Repeatabilities with the FR Model were assessed at 0.76 for milk yield, 0.41 and 0.34 for water and dry matter intakes and after applying the RR Model they changed during the lactation to 0.79–0.92, 0.46–0.52 and 0.43–0.50, respectively. Correlations with the FR Model between milk yield and water and dry matter intakes and between water and dry matter intakes were 0.73, 0.59 and 0.73, respectively, and after applying the RR Model they ranged in the course of lactation between 0.13 and 0.84, 0.48 and 0.93, and 0.76 and 0.82, respectively. Hence, variance components of these traits differed during lactation. Thus the use of RR models must be emphasised to analyse these traits.     

荟萃分析法评估酵母培养物对奶产量和干物质采食量的影响

<正>通常,为了帮助生产者对他们的动物养殖生产活动做出最佳的决定,动物营养学家、兽医师和其他的乳业专业人员需要通过一些精心设计并且在统计上具有显著性的试验研究来佐证他们所提供的咨询意见或建议。事实上,对某一特定产品仅进行一个或者两个研究试验所得出的结论,未必能够给这些咨询专家或顾问们足够的信心去向他们的客户提供一份有关该产品的推荐书。     

Sward characteristics, grass dry matter intake and milk production performance is affected by timing of spring grazing and subsequent stocking rate

The objective of this study is to investigate the effect of contrasting spring grazing dates (GD) and stocking rate (SR) on sward characteristics, grass dry matter intake and milk production performance of autumn calving dairy cows during the spring period. Two swards were created by grazing in March (early grazing; E) or by delaying first grazing until mid-April (late grazing; L). Two stocking rates, high (H; 5.5) and medium (M; 4.5) were applied across each sward. Forty eight autumn calving Holstein cows (160 ± 35 days in milk) were assigned to one of four (n = 12) different grazing treatments. The experiment began on April 17th and finished after 2 grazing rotations on June 20th. Later spring grazing significantly increased herbage mass (kg DM/ha) above ground level (+ 933, P < 0.05) and > 50 mm (+ 738, P < 0.05). Compressed sward height (+ 22.1 mm, P < 0.05), extended tiller height (+ 73 mm, P < 0.001) and pseudostem height (+ 35 mm, P < 0.001) were also significantly higher for later grazed swards. In the grazing horizon (> 80 mm— extended tiller height), later grazed swards had significantly lower leaf proportion (− 0.09, P < 0.05) and higher dead material (+ 0.05, P < 0.001). Daily herbage allowance (> 50 mm) was on average 12.7, 15.9, 18.2 and 21.9 kg DM/cow for EH, EM, LH and LM, respectively. Daily leaf allowance (> 80 mm) was 10.1, 12.3, 13.3 and 14.5 kg DM/cow for EH, EM, LH and LM, respectively. The EM (16.2 kg DM/cow), LH (+ 0.1 kg) and LM (0.8 kg) treatments all had similar grass DM intake, however there was evidence of an interaction (P < 0.10) between GD and SR, this was due to the low grass DM intake of the EH (13.9 kg DM/cow) treatment. When expressed as UFL (Fill unit) intake the EM treatment recorded the highest value. There was a significant interaction between GD and SR (P < 0.01) for milk, protein yield, 4% fat corrected milk yield (P < 0.05) and protein concentration (P < 0.001). Cows grazing the EM treatment produced 23.9 kg of milk, 876 and 685 g of fat and protein yield. The difference in milk production (cow/day) between EM and EH treatments was + 3.6 kg milk, + 98 g fat and + 107 g protein. The production yield difference between LM and LH treatments was + 1.1 kg milk, + 27 g fat and + 29 g protein in favour of the LM treatment (23.9 kg of milk, 877 and 687 g fat and protein yield). Herbage quality and morphological characteristics are clearly improved with early spring grazing as herbage mass is reduced on subsequent rotations. Swards grazed in early spring allow higher grass utilisation and high milk production performance when grazed at a medium stocking rate. Improved milk production from herbage can be achieved provided herbage mass and allowance are maintained at levels where herbage quality decreases are minimised.     

Effects of milk intake on forage intake and performance of suckling range calves

A study to examine the relationships between milk intake, forage intake, and performance of Hereford-Angus suckling range calves was conducted during July, August, and September of 1984 and 1985. Twenty calves were used each year. The study was conducted at the Red Bluff Research Ranch located 56 km west of Bozeman, Montana. Average daily gain, milk intake (MI), forage digestibility, and fecal output (FO) were measured at 28-d intervals, beginning when the average calf age was 66 +/- 4 d. Milk intake was estimated using weigh-suckle-weigh techniques. Total fecal collections were used to measure FO. Forage digestibility and rates of passage were determined using nylon bag in situ techniques and external markers in ruminally cannulated calves of the same age. Fecal output by calves increased as body weight and age increased. Milk intake was higher (P less than .05) in 1985 than in 1984, but FO was higher (P less than .01) in 1984 than in 1985. Fecal output by calves was negatively correlated to MI in July (r = -.62; P less than .05) and August (r = -.56; P less than .05). No significant correlations were detected between MI and ADG (P greater than .10). Forage intake estimates were derived from FO, rate of passage, and in situ digestibility values. During July, calves consumed .3 kg more forage for each kilogram of reduction in fluid MI (P less than .05). In both August and September, calves consumed .6 kg more forage for each kilogram of reduction in fluid MI (P less than .10). Calves maintained similar digestible energy (DE) intake both years, although the source of DE varied.     

The effect of milk intake on forage intake and growth of nursing calves

Thirty-nine Holstein steer calves were assigned to one of five treatments at birth and individually fed for 200 d with milk replacer reconstituted to equal the fat and protein concentration of beef cow milk. Treatment levels were the quantities of reconstituted milk fed per day based on lactation curves, which were based on peak milk levels (PML) of 2.72, 5.44, 8.16, 10.88, and 13.6 kg/d, respectively. In addition to reconstituted milk, chopped alfalfa hay was offered ad libitum to allow for maximal voluntary forage consumption. All calves were fed a high-energy diet postweaning until they reached a similar degree of fatness in the 12th rib (4 to 5% chemical fat) as determined by ultrasound. There were differences (P < 0.05) among groups in weaning weight, preweaning ADG, age, and weight at slaughter. During the preweaning phase, there was a linear relationship (P < 0.01) for daily milk and forage DE intake; however, DE intake per unit of BW did not differ across treatments (P = 0.06). Increasing PML resulted in a linear (P < 0.01) decrease in alfalfa hay intake in the preweaning phase, and G:F increased quadratically (P < 0.01). During the postweaning phase, preweaning milk intake had no meaningful effect on postweaning ADG, but overall ADG had a linear relationship (P < 0.01) with preweaning milk level. There was no effect of PML on the 12th-rib lipid percent, marbling score, or quality grade, but protein and fat concentration in the carcass and empty BW increased linearly (P < 0.01) with PML. The group fed at 2.72 kg/d PML was 58 kg lighter (P = 0.03) and required 34 d more (P < 0.01) to reach the predetermined degree of fatness at slaughter than the group fed at 13.6 kg/d PML, suggesting that increased milk production by the dam can decrease the number of days to the slaughter weight at which a similar rib lipid concentration is reached.     

Effect of herbage allowance and concentrate supplementation on dry matter intake, milk production and energy balance of early lactating dairy cows

The objective of this study was to investigate the effect of daily herbage allowance and concentrate supplementation level offered at approximately 40 and 80 days in milk (DIM) and the carryover effects at 120 DIM on the production performance of spring calving dairy cows. Sixty-six (30 primiparous and 36 multiparous) Holstein–Friesian dairy cows (mean calving date — 7 Feb ± 9.9 days) were randomly assigned to a 6 treatment (n = 11) grazing study. The experiment was a randomised block design with a 3 × 2 factorial arrangement of treatments (3 daily herbage allowances (DHA's; approximately 13, 16 and 19 kg DM/cow/day; > 4 cm) and 2 concentrate allowances (0 and 4 kg DM/day). Treatments were imposed from 21 February to 8 May. Following this period (subsequent 4-weeks) animals were offered a daily herbage allowance of 20 kg DM/cow/day and no concentrate. Milk production, total dry matter intake (TDMI), energy balance (EB) and blood metabolites were measured on three occasions — at approximately 40, 80 and 120 days in milk, R1, R2 and the carryover period, respectively. Cows offered a low DHA had a lower post-grazing sward height but increased sward utilisation (> 4 cm) during R1 and R2, there was no difference during the carryover period. Concentrate supplementation increased post-grazing sward height by 11% during R2 but had no effect during R1 and the carryover period. Daily herbage allowance had no effect on milk yield or composition during R1 however a low DHA tended to reduce milk yield in R2. Concentrate supplementation increased milk and solids corrected milk (SCM) yield by 4.1 and 2.8 kg/cow/day, respectively during R1 and also increased R2 milk production performance, this effect extended into the carryover period. Offering a low DHA restricted grass dry matter intake (DMI) during R1 and R2 yet concentrate supplementation significantly increased total DMI (2.3 (R1) and 3.0 (R2) kg DM/cow). Animals offered a low DHA had a significantly lower bodyweight (BW) than those offered a medium or high DHA during P1 and P2. Concentrate supplementation increased BW during P1 and P2 (+ 9 and + 14 kg/cow, respectively). There was no effect of treatment on BW during P3. There was no effect of DHA on EB in R1; during R2 animals offered a low DHA had the lowest EB. Concentrate significantly increased EB in R1 and R2 and increased plasma glucose concentration while it decreased plasma NEFA and BHB concentrations. The results of this study indicate that animals should be offered a low DHA up to 80 DIM after which DHA should be increased however animals should also be supplemented with concentrate during the early post-partum period.     

Forage intake by lactating beef cows differing in potential for milk production

Two feeding trials (early and late lactation) were conducted to measure ad libitum forage intake by beef cows from three breed groups of similar mature weight, but with different milk production potential. Twenty-four cow-calf units, eight from each milk production level (low, medium and high) were grouped (two/pen) based on similarity of cow weight and previous weigh-suckle-weigh and calf weaning weight data. Each pair of cow-calf units was confined to separate pens and allowed ad libitum access to chopped native Sandhills meadow hay. Dry matter intake, cow and calf BW and calf milk consumption were determined. Daily DMI (kg/hd) and milk consumption showed a positive linear response (P less than .05) among low, medium and high milk-producing cows. When cow DMI was expressed as g/unit mean cow BW during the trial, both a positive linear (P less than .05) and a quadratic response (P less than .01) expressed the relationship among production levels during early and late lactation. Calf forage intake, birth weight and adjusted 181- and 205-d weaning weight had no linear or quadratic relationship (P greater than .10) to milk production levels. However, June 1 calf weight, actual calf weaning weight and calf rate of gain (birth to weaning) had a positive linear (P less than .07) relationship. Best fit regression models with DMI as the dependent variable were developed for each trial based on R2 and CV values of the potential models. The best fit model (R2 = .94, SE = .33) for early lactation included production level as a class variable with cow BW.75 and calf birth weight as independent variables. The best fit model (R2 = .92, SE = .53) for late lactation included actual weaning weight in addition to the variables used during early lactation.     

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.     

酵母培养物对奶牛干物质采食量、产奶量及血清指标的影响

试验旨在研究纽润康酿酒酵母培养物对奶牛的干物质采食量、产奶量及血清指标的影响。试验组和对照组各300头奶牛,对照组奶牛饲喂基础日粮,试验组奶牛在基础日粮基础上添加120 g/(头·d)酿酒酵母培养物。结果显示,试验组奶牛产奶量显著提高1.66 g/(头·d),平均干物质采食量显著提高0.72 g/(头·d)。试验组奶牛血清中谷丙转氨酶活性极显著低于对照组(P<0.01),血清免疫球蛋白G (IgG)含量极显著高于对照组(P<0.01)。日粮中添加酵母培养物能够极显著提高超氧化物歧化酶(SOD)活性(P<0.01),显著提高奶牛机体的总抗氧化能力(T-AOC)(P<0.05)。研究表明,日粮中添加酿酒酵母培养物可提高奶牛机体的免疫力和抗氧化能力。     

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 barn 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.     

Influence of calving difficulty on dry matter intake immediately after calving of dairy cows

We investigated the influence of calving difficulty on dry matter intake (DMI) in Holstein cows immediately after calving using 15 pregnant heifers and 15 multiparous cows. DMI was measured for 6 days after calving. Calving difficulty was evaluated with a calving score, and urinary cortisol was measured. The calving score was higher in the first lactation heifers than in the multiparous cows. The average DMI 6 days after calving was lower in the first lactation heifers than in the multiparous cows. The urinary cortisol concentration at 4 days after calving was higher in the first lactation heifers than in the multiparous cows and was positively associated with the calving score. The DMI was negatively associated with the calving score and the urinary cortisol concentration at 4 days after calving and was positively associated with the average milk yield 6 days after calving and the serum calcium concentration at 3 days after calving. We conclude that DMI immediately after calving is influenced not only by nutrient requirements of cows but also stress derived from calving, and the low DMI in the first lactation heifers is due to the lower energy requirement and high susceptibility to the stress compared with multiparous cows.     

不同粗饲料对奶牛乳产量和乳成分的影响

选择18头荷斯坦奶牛,设置3个处理,每个处理6个重复,每个重复1头奶牛,研究不同粗饲料对奶牛泌乳性能和乳成分的影响,3个处理的粗饲料分别为玉米秸(Ⅰ组)、玉米秸+青贮玉米秸(Ⅱ组)、羊草(Ⅲ组)。试验结果表明:①试验Ⅱ组与试验Ⅲ组平均产奶量差异不显著(P>0.05),试验全期分别比Ⅰ组提高了8.82%(P<0.05)和9.57%(P<0.05);②不同处理间的乳糖、乳脂含量差异不显著(P>0.05);对于乳蛋白,在试验40d时3个试验组差异不显著(P>0.05),在第15d时Ⅱ组、Ⅲ组分别比Ⅰ组降低了7.43%(P<0.05)和8.57%(P<0.05)。对于乳干物质,Ⅱ组与Ⅲ组差异不显著(P>0.05)。根据上述生产性能指标综合评定,玉米秸+青贮玉米秸可有效替代羊草饲喂奶牛,而不降低泌乳性能。     

Milk production responses to pre- and postcalving dry matter intake in grazing dairy cows

Sixty-eight multiparous grazing dairy cows were randomly allocated to two precalving pasture allowances to achieve differential dry matter intakes (DMI) for 29 ± 7.7 d precalving (Low or High DMI; 4.8 or 11.9 kg DM). At calving, cows within each precalving treatment were randomly allocated to one of two levels of feeding (Low or High DMI; 8.6 or 13.5 kg DM) for 35 d postcalving in a completely randomized design and a 2 × 2 factorial arrangement of treatments. Following treatments all cows grazed together and were fed pasture and pasture silage. Daily milk yields were recorded, and fat, protein and lactose concentrations determined weekly for 15 weeks. Blood was sampled weekly pre- and postcalving and analysed for indicators of energy status, growth hormone (GH) and insulin-like growth factor-1 (IGF-1). Body condition score (BCS) at calving was reduced by precalving restriction (P < 0.001; 2.8 and 3.0 for precalving Low and High treatment groups, respectively). Precalving restriction reduced milk fat production by 8.4% during the first 5 weeks postcalving, but differences were not significant subsequently. Postcalving feed restriction reduced yield of fat corrected milk (FCM), fat and protein by 23, 21 and 28%, respectively, during the first 5 weeks postcalving. Decreased (P < 0.05) yields of FCM, fat and protein (11, 10 and 9%, respectively) were also evident for 10 weeks after the feed restriction finished. There was a tendency (P < 0.1) for a precalving × postcalving DMI interaction in milk protein yield during the first 5 weeks of lactation with no effect of precalving level of feeding in cows that were restricted postcalving. The plasma concentrations of non-esterified fatty acids (NEFA), β-hydroxybutyrate (BOH) and GH were elevated in restricted cows precalving, and IGF-1 concentration was reduced. Plasma NEFA and BOH concentrations were elevated postcalving in restricted cows, but no effect of postcalving DMI on GH or IGF-1 concentration was evident. Results suggest that under grazing systems milk production responses to precalving DMI are small, but energy restrictions in early lactations result in significant carryover effects in milk production.