Radcliff R P, Vandehaar M J, Chapin L T, Pilbeam T E, Beede D K, Stanisiewski E P, Tucker H A
Department of Animal Science, Michigan State University, East Lansing 48824, USA.
J Dairy Sci. 2000 Jan;83(1):23-9. doi: 10.3168/jds.S0022-0302(00)74850-8.
To determine effects of rapid prepubertal growth on first-lactation milk production, Holstein heifers were randomly assigned to one of three treatments. Thirty-five heifers were fed a standard diet to meet NRC recommendations and produce 0.8 kg of body weight (BW) gain/d (standard). Thirty-five heifers were fed a diet with higher energy (2.8 Mcal of metabolizable energy/kg) and protein (19.7% crude protein; high diet) to produce 1.2 kg of BW gain/d (high). Thirty-five heifers were fed the high diet and injected daily with bovine somatotropin (bST) (25 microg/kg of BW; high-bST). Diets were fed and bST was injected from 135 kg of BW until pregnancy was confirmed. Heifers were inseminated after BW exceeded 363 kg. Pregnant heifers were commingled and fed similar diets through gestation, parturition, and lactation. High and high-bST heifers had greater prebreeding average BW gains than standard heifers. Conversely, standard heifers had a greater average BW gain during gestation than high and high-bST heifers. High and high-bST heifers were approximately 90 d younger than standard heifers at first insemination and first parturition. Postpartum BW, body condition scores, and withers heights at parturition, and calving ease scores were not different among treatments. Standard heifers produced 14% more milk than high heifers but not more than high-bST heifers. The high-protein, high-energy diet decreased age at first parturition and first-lactation milk production, but did not affect reproduction. Injection of bST during the prepubertal growth period combined with the high diet decreased age at first parturition without reducing milk production.
为了确定青春期前快速生长对首次产奶量的影响，将荷斯坦小母牛随机分为三种处理方式之一。35头小母牛饲喂标准日粮以满足美国国家研究委员会（NRC）的建议，日增重0.8千克体重（BW）（标准组）。35头小母牛饲喂能量更高（每千克2.8兆卡代谢能）和蛋白质含量更高（19.7%粗蛋白；高日粮组）的日粮，日增重1.2千克体重（高增重组）。35头小母牛饲喂高日粮并每天注射牛生长激素（bST）（每千克体重25微克；高bST组）。日粮从体重135千克开始饲喂，bST从该体重开始注射，直至确认怀孕。小母牛体重超过363千克后进行授精。怀孕的小母牛在整个妊娠期、分娩期和哺乳期混合饲养并饲喂相似的日粮。高增重组和高bST组小母牛在配种前的平均体重增加量高于标准组小母牛。相反，标准组小母牛在妊娠期的平均体重增加量高于高增重组和高bST组小母牛。高增重组和高bST组小母牛在首次授精和首次分娩时比标准组小母牛大约年轻90天。各处理组之间产后体重、体况评分、分娩时的鬐甲高度和产犊难易度评分没有差异。标准组小母牛的产奶量比高增重组小母牛多14%，但不比高bST组小母牛多。高蛋白、高能量日粮降低了首次分娩年龄和首次泌乳期产奶量，但不影响繁殖性能。青春期前生长期间注射bST并结合高日粮可降低首次分娩年龄且不降低产奶量。
