A study was conducted to evaluate the effect of abomasal infusion of casein on post-ruminal digestibility of starch
and on milk yield and composition. Six multiparous Israeli Holstein cows in mid lactation, fitted with ruminal and
abomasal cannulas, were used in a 3 ✕ 3 Latin-square experiment. Each cow received 1600 g maize starch infused
into the abomasum. Treatments were : abomasal infusion of
... [Show full abstract] sodium caseinate at 0, 350, or 700 g casein daily.
Chromium mordant neutral-detergent fibre (NDF) was used as a digesta marker. Casein infusion was associated
with increases in post-ruminal and total-tract digestibility of non-structural carbohydrates and protein.
Concentrations of rumen ammonia and of plasma insulin, glucose and urea were higher in casein-infused cows.
Concentrations of milk protein and lactose and milk protein yield increased with casein infusion. Results indicate
that increased protein flow to the abomasum can improve the yield of milk constituents in dairy cows. Digestibility
and yield responses to infusion of 350 g casein per day were similar to those at 700 g/day. There was a tendency
toward reduced milk protein efficiency in casein-infused cows. It is suggested that part of the production response
can be related to a direct effect of protein supply and the rest can be explained by the indirect effect of improved
carbohydrate availability in the small intestine.