Silage and dairy cow production

Abstract

Cows were offered constant amounts of unwilted pasture silage or pasture In 5 experiments. The milk yield and milk protein, concentration of cows offered silage were increased by abomasal infusions of casein in all experiments. Infusions of 300 g/day casein raised milk and protein by an average of 1.1 kg/day and 0,19% respectively. Methionine (12 g/day) gave a similar response to casein. Isocaloric infusion of glucose did not alter milk yield or milk protein above the controls on the silage ration. Abomasal infusions of casein increased milk yield of cows offered pasture but responses were significantly less than obtained with silage. The studies demonstrate that the amount of protein entering the duodenum of cows fed high moisture pasture silage limited milk production and that methionine was a major amino acid limiting the synthesis of milk and its constituents.