Abstract

The aim of this experiment was to determine the effects of insulin on milk protein production in lactating, pasturefed dairy cows. Five lactating rumen-fistulated Jersey cows were subjected to a hyperinsulinaemic euglycaemic clamp (HEC) with and without an abomasal infusion of casein (310g/d) in a two period cross-over design experiment. The HEC significantly reduced milk yield in the control cows compared to casein-infused cows (9.9 ± 0.5 vs 13.2 ± 0.5 kg/d, P<0.001). Milk protein yield was significantly higher in the casein-infused cows compared to the control cows (482 ± 16 vs 421 ± 16 g/d, P<0.05). The HEC significantly reduced milk protein yield in the control cows compared to casein-infused cows (311 ± 16 vs 459 ± 16 g/d, P<0.001). The use of the HEC technique in pasture-fed cows did not result in the milk protein response reported in concentrate-fed cows.

PJ, Back, DDS MacKenzie, SR Davis, PM Harris, and J Lee

Proceedings of the New Zealand Society of Animal Production, Volume 63, Queenstown, 35-39, 2003