THE EFFECT OF DIFFERENT RATIOS OF GRASS SILAGE TO CONCENTRATE ON MILK YIELD, MILK COMPOSITION AND BODY WEIGHT

Four rations were fed in two experiments to 28 Holstein and Ayrshire cows past peak production, using change-over and continuous feeding designs.The control ration consisted of silage fed at 3 pounds, and hay in excess of 1 pound per 100 pounds body weight with grain concentrate (14 per cent protein) fed at 1 pound for each 4 pounds milk yield daily. The other three rations contained grass silage to provide one-third, one-half or two-thirds of daily energy requirement, and a grain concentrate (10 per cent protein) to meet the remaining energy required by each cow. Feed energy was evaluated in terms of total digestible nutrients (TDN) and as estimated net energy (ENE).Influence of rations on milk yield or body weight was not significant (P = 0.05). With the change-over design, body weight and yields of FCM appeared to increase as more concentrate was fed and, in the continuous feeding design, milk yield of higher producing cows appeared to be depressed when larger amounts of roughage were fed. The relationship of energy intake to milk yield did not differ significantly whether evaluated as TDN or ENE. Percentages of protein, fat and solids-not-fat as indicators of milk composition were not significantly affected by the types of rations used in these experiments.