title: Relationships between the plasma concentrations of insulin-like growth factor-I in dairy cows and their fertility and milk yield.
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-I 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.
authors.affiliation: Reproduction and Development Group, Department of Veterinary Basic Sciences, Royal Veterinary College, Hawkshead Lane, North Mymms, Hatfield AL9 7TA.
authors.forename: V J
authors.initials: VJ
authors.lastname: Taylor
authors.forename: Z
authors.initials: Z
authors.lastname: Cheng
authors.forename: P G A
authors.initials: PG
authors.lastname: Pushpakumara
authors.forename: D E
authors.initials: DE
authors.lastname: Beever
authors.forename: D C
authors.initials: DC
authors.lastname: Wathes
mesh_terms: D000818:Animals; D002417:Cattle / Q000502:physiology*; D005260:Female; D005298:Fertility / Q000502:physiology*; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D007774:Lactation / Q000502:physiology; D008597:Menstrual Cycle / Q000502:physiology; D008892:Milk / Q000737:chemistry / Q000378:metabolism*; D010298:Parity / Q000502:physiology; D036801:Parturition / Q000502:physiology; D011374:Progesterone / Q000097:blood; D011863:Radioimmunoassay / Q000662:veterinary
chemical_list: D011374:Progesterone; D007334:Insulin-Like Growth Factor I