Effect of casein infusion in the rumen, duodenum or both sites on factors affecting forage intake and performance of dairy cows fed red clover-grass silage.

Four lactating dairy cows were used in a balanced 4 x 4 Latin square design to examine the effects of casein infusion in the rumen, duodenum, or both on the intake of red clover-grass silage, chewing behavior, diet digestion, microbial protein synthesis, rumen fermentation, digestion, and passage kinetics, milk production, and milk composition. Duodenal infusion increased eating time, silage intake, rumen neutral detergent fiber pool, yields of milk, protein, and lactose, and concentration of milk protein, and tended to decrease that of milk fat. Ruminal infusion tended to decrease eating time, and increased significantly microbial protein synthesis, rumen ammonia-N concentration, molar proportions of isovalerate and valerate, digestion rate of digestible neutral detergent fiber, passage rate of indigestible neutral detergent fiber, and milk urea content, and decreased rumen neutral detergent fiber pool. Silage intake, and yields of milk, protein, and lactose were highest when casein was simultaneously infused in both sites.