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Relationships between the plasma concentrations of insulin-like growth factor-I in dairy cows and their fertility and milk yield
  1. V. J. Taylor, BSc, PhD,
  2. Z. Cheng, BVetMed, MSc, PhD,
  3. P. G. A. Pushpakumara, BVSc, PhD,
  4. D. C. Wathes, BSc, PhD, DSc1 and
  5. D. E. Beever, BSc, PhD2
  1. 1 Reproduction and Development Group, Department of Veterinary Basic Sciences, Royal Veterinary College, Hawkshead Lane, North Mymms, Hatfield AL9 7TA
  2. 2 Centre for Dairy Research, Department of Agriculture, University of Reading, Reading RG6 6AT

Abstract

The relationships between insulin-like growth factor-I (IGF-I) and the fertility and milk yield of Holstein-Friesian dairy cows were investigated. The concentration of IGF-I in blood was measured weekly from one week before to 12 weeks after calving in 177 multiparous cows and at four times during this period in 142 primiparous cows; the concentration of IGF-I in milk was measured in 50 of the multiparous cows. The plasma concentrations of IGF-I were higher in the primiparous than in the multiparous animals. In the primiparous cows, high concentrations of IGF-I before calving were associated with longer calving to conception intervals. Conversely, in the multiparous cows low concentrations of IGF-1 before and after calving were associated with a failure to conceive, despite repeated services. Multiparous cows with IGF-I concentrations of greater than 25 ng/ml in the week after calving were 11 times more likely to conceive to first service than those with lower concentrations. Concentrations of IGF-I greater than 50 ng/ml at first service increased the likelihood of conception five-fold. Cows with higher peak milk yields had lower plasma concentrations of IGF-I and took longer to return to ovarian cyclicity. The negative relationship between milk yield and return to cyclicity was stronger in the multiparous cows (P<0˙002) than in the primiparous cows (P<0˙04). The concentrations of IGF-I in milk followed a different pattern and were not associated with the changes in plasma IGF-I or fertility.

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