EFFECT OF DUODENAL PROLINE INFUSION ON MILK-PRODUCTION AND COMPOSITION IN DAIRY-COWS

Four Israeli-Friesian cows, two at peak and two at mid lactation, were fitted with duodenal cannulas. They were given proline or water infusions for 8-day periods to evaluate the effect of duodenal infusion of proline on arginine uptake by the mammary gland and on milk yield and composition of dairy cows. Milk fat content and 40 g/kg fat-corrected milk yield increased for all cows due to proline infusion. Milk protein concentration during either early or mid lactation and milk protein yield during early lactation, were not affected by proline infusion. Milk protein yield during mid lactation was increased due to proline infusion. Arginine uptake by the udder dropped by one-half during proline infusion. Results suggest that post-ruminal administration of supplemental proline reduced requirements for arginine by the udder and improved efficiency of dietary energy utilization.