Endocrine Abstracts

Dairy cows normally calve for the first time when not yet fully grown. Subsequent pregnancies occur during lactation. Therefore in primiparous (PP) cows the fetus competes for nutrients with maternal growth, while in multiparous (MP) cows they compete with milk production. Human epidemiological studies demonstrate that low birth weight can predispose offspring to a variety of metabolic diseases in adult life. This study investigated the hypothesis that such competition limits nutrient availability to the fetus thus compromising calf development.

123 female Holstein-Friesian calves were monitored from birth through their first lactation. All animals were measured at birth, 3, 6, 9 and 15 months and 55 were selected for metabolic profiling. This was performed (i) at 6 months of age, (ii) just before first insemination, performed at approximately 15 months and ( iii) before calving and during early lactation.

PP cows produced smaller calves than MP cows (P<0.05) but these offspring demonstrated catch-up growth by 3 months of age. This was associated with significantly higher concentrations of IGF-I (P<0.009) at both 6 months and service, while insulin tended to be higher in MP offspring at service. However smaller, low birth weight (LBW) offspring of MP cows remained smaller than their high birth weight (HBW) peers with unaltered IGF-I and insulin concentrations. IGF-I levels took longer to recover from the post-partum decline in PP offspring and insulin levels remained lower than those of MP offspring after calving. LBW offspring failed to regain their IGF-I levels to those of HBW offspring, although insulin concentrations were similar in these groups. The evidence supports the hypothesis that nutrient supply during fetal development influences the size of the calf at birth and this in turn affects its subsequent metabolic profile during growth and lactation. (Sponsored by DEFRA and the MDC).