RESPONSES TO A LONG-CHAIN FATTY-ACID SUPPLEMENT FED TO DAIRY-COWS AT 2 STAGES OF LACTATION

A group of 36 Holstein-Friesian cows in a commercial dairy herd were used to test the effects on milk yield and composition of feeding 0.5 kg/day of a rumen-inert fat supplement containing long-chain fatty acids, given in addition to their normal ration. The group was divided into early and mid lactation cows, and the effect of the supplement was evaluated over a 12-week period of grazing predominantly kikuyu (Pennisetum clandestinum) pastures. There was a non-significant (P > 0.05) trend to increased milk yield for cows in mid lactation (9% or 2.8 kg milk/kg fat supplement), no response in early lactation, and an overall response of 0.8 kg milk/kg fat supplement for all cows. There was no effect (P > 0.05) of fat supplement on milk components. The lack of a milk response in the early lactation group is discussed in relation to the protein content of the diet and changes in liveweight. The varied responses with stage of lactation mean that feeding systems that can easily differentiate stages of lactation for cows would be required in dairies.