Abstract #M298

# M298
The effects of feeding a high- or low-plane of milk pre-weaning on IGF-1 and IGFBP in dairy heifers.
J. Haisan*1, M. Oba1, D. J. Ambrose2, M. A. Steele1, 1University of Alberta, Edmonton, AB, Canada, 2Livestock Research Section, Agriculture and Forestry, Edmonton, AB, Canada.

The objective of this experiment was to determine the effects of a high-plane of milk before weaning on plasma insulin-like growth factor 1(IGF-)1 and insulin-like growth factor binding proteins (IGFBP) concentrations and their relationship in group-housed calves. Twenty-six female Holstein calves were fed 4 2-L feedings of colostrum for the first 2 d after birth and randomly assigned to either a HIGH (10 L/d; n = 13) or LOW (5 L/d; n = 13) plane of milk. All calves were allowed 2.5L of pasteurized whole milk per meal until 7 weeks of life before a 10-d weaning transition began, where milk was reduced by 10% per day, resulting in all calves being weaned at 9 weeks. Calf starter and water were provided ad libitum throughout. Pre-weaning average daily gain was 0.90 kg/d for HIGH and 0.65 kg/d for LOW treatments, however, no difference was seen post-weaning. Blood samples were taken starting at 0830 h at 1, 3, 5, 7 and 9 weeks of life and analyzed for IGF-1 and IGFBP-2, −3, −4 and −5. Pre-weaning, IGF-1 concentrations were greater for HIGH than LOW (198.96 vs. 120.39 ng/mL, P < 0.01), but did not differ post-weaning. Plasma levels of IGFBP-2 were lower in HIGH calves pre-weaning than in LOW (483.64 vs. 714.86 ng/mL, P < 0.05), with no difference post-weaning. There was no effect of treatment on concentrations of IGFBP-3, −4 or −5 pre- or post-weaning. However, a treatment by week interaction existed during the pre-weaning period for IGFBP-3. Overall, from wk 1 to 9, a treatment by week interaction existed for IGFBP-2 and IGFBP-3, and the ratio of IGFBP-3 to IGFBP-2. These results suggest that a high plane of nutrition pre-weaning increased IGF-1 concentration before the weaning transition, and exerts effects on plasma concentrations of IGFBP.

Key Words: IGF, IGFBP, dairy calf