Although positive effects on growth have been shown when calves are placed on high planes of nutrition, little information exists regarding the effect of this feeding strategy on insulin-like growth factor-1 (IGF-1), a hormone whose fundamental action is to stimulate growth, and its binding proteins during the preweaning period. The objective of this study was to characterize IGF-1 and insulin-like growth factor binding protein (IGFBP) concentrations in plasma during the pre- and immediate postweaning period, when calves were offered a high or low plane of whole milk. Twenty-six female Holstein calves were randomly assigned to either a high (HI; 10 L/d; n = 13) or low (LO; 5 L/d; n = 13) plane of milk following colostrum feeding at d 3 of life. Calves were fed their respective diet as whole milk until d 48 when a 10-d weaning transition began. During this transition, milk was reduced by 10% per day such that all calves received no milk on d 59 of life. Blood samples were collected bi-weekly to measure IGF-1 and IGFBP in plasma. Calves fed HI gained more body weight than calves fed LO during the preweaning period (d 1–48 of life; 0.90 vs. 0.65 kg/d); however, no differences in average daily gain or metabolizable energy intake during the weaning transition (d 48–58 of life) or postweaning period (d 59–70 of life) occurred. Concentrations of IGF-1 were higher in HI calves during the preweaning period, which was associated with high levels of IGFBP-3 at wk 5 and lower IGFBP-2 during each measured time point preweaning as compared with LO. Insulin-like growth factor binding protein-4 was lower in HI calves only during wk 1, and IGFBP-5 was not affected by the dietary treatment. Overall, offering a high plane of nutrition was associated with changes in plasma IGF-1 and IGFBP that would indicate greater growth and development preweaning but not necessarily postweaning.

尽管将犊牛放在高营养水平上已显示出对生长的积极影响，但是关于这种喂养策略对胰岛素样生长因子-1（IGF-1）的作用的信息很少，胰岛素样生长因子-1（IGF-1）的基本作用是刺激断奶前的生长及其结合蛋白。这项研究的目的是表征在断奶前和断奶后立即给小牛提供全脂或高脂全脂奶的血浆中IGF-1和胰岛素样生长因子结合蛋白（IGFBP）的浓度。在生命的d 3初乳喂养后，将26只雌性荷斯坦犊牛随机分配到高（HI; 10 L / d; n = 13）或低（LO; 5 L / d; n = 13）牛奶平面。小牛以全脂奶喂养各自的饮食，直到第48天断奶断奶过渡开始至第48天。在此过渡期间，每天减少10％的牛奶，以使所有犊牛在生命的第59天都不喝牛奶。每两周收集一次血样以测量血浆中的IGF-1和IGFBP。在断奶前期，喂饲HI的犊牛的体重比喂喂LO的犊牛的体重多（生命的1-48天； 0.90 vs. 0.65 kg / d）；但是，在断奶过渡期（生命的48至58岁）或断奶后阶段（生命的59至70岁）的平均日增重或代谢能摄入量没有差异。与LO相比，HI断奶前犊牛中IGF-1的浓度较高，这与第5周的IGFBP-3高水平相关，而在每个测得的断奶时间点IGFBP-2较低。胰岛素样生长因子结合蛋白4仅在第1周时在HI犊牛中较低，而IGFBP-5不受饮食治疗的影响。全面的，