Evaluation of a model that estimates insulin sensitivity in dairy cows

Glucose challenge data was used to model parameters describing the dynamics of the glucose-insulin system such as glucose effectiveness (SG), acute insulin response to glucose (AIRg) and insulin sensitivity (SI) in dairy cows. The relationship of these parameters with post-partum anovulatory interval (PPAI) was also determined. Twenty-five HF cows of New Zealand (NZ; n=13) and Overseas (OS; n=12) origin, were fed either pasture (n=12) or a total mixed ration (TMR; n=13) in a 2x2 factorial design. At two weeks postpartum, they were challenged intravenously with 300 mg of glucose/kg live weight. There was no effect of diet on SG (P=0.302), SI (P=0.17) or AIRg (P=0.093) despite TMR cows of both genotypes having higher values. There was no effect of genotype on SG (P=0.234), SI (P=0.742) or AIRg (P=0.385). Correlations of these parameters with PPAI were not statistically significant: SI (r 2 =0.087, P=0.310), SG (r 2 = 0.001, P=0.962) and AIRg (r 2 =0.036, P=0.320). Use of this model demonstrated that insulin response parameters