Short communication: The effects of offering a high or low plane of milk preweaning on insulin-like growth factor and insulin-like growth factor binding proteins in dairy heifer calves

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.