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Glucose-Dependent Insulin Response and Milk Production in Heifers Within a Segregating Resource Family Population

Research Institute for the Biology of Farm Animals (FBN), Dummerstorf, Germany

¹ Corresponding author: hammon{at}fbn-dummerstorf.de

An experiment was initiated to evaluate the glucose-dependent insulin response in relation to milk production in F₂ crossbred cattle with respect to secretion type (Holstein) and accretion type (Charolais). For this purpose, F₂ offspring were generated by mating Charolais bulls with German Holstein cows and a following intercross of the F₁ individuals. In 52 dairy heifers of 5 F₂ half-sib families, glucose-dependent insulin responses were investigated during first lactation to test the hypothesis that the different genetic disposition for milk production within the F₂ population would affect the insulin response to glucose. Heifers received intravenous glucose infusions (1 g/kg of BW^0.75) 10 d before, and 30 and 100 d after parturition. Blood samples were taken before and at 7, 14, 21, and 28 min after glucose challenge. Glucose and insulin concentrations were measured in blood, and glucose half-life as well as areas under the curve for glucose (AUC_gluc) and insulin (AUC_ins) were calculated. Milk yield was low but differed among F₂ families. Before parturition, insulin concentrations after glucose challenge showed no between-family differences for AUC_ins. In contrast, on d 30 and 100 of lactation, glucose half-life and AUC_ins differed among families. Calculated correlations revealed a significant negative relationship between AUC_ins and milk yield as well as glucose half-life on d 30 and 100 of lactation. In conclusion, milk production as well as the glucose-dependent insulin response of F₂ Charolais x German Holstein crossbred dairy heifers differed between half-sib families, with both parameters displaying an inverse relation to each other.

Key Words: heifer • lactation • glucose metabolism • crossbreeding