Total mixed rations containing 31 or 25% NDF were supplemented with 0 or .5 kg/cow per d Ca salts of fatty acids to study the effect of adding Ca salts of fatty acids to diets that differed in NDF content. Rations were fed for ad libitum intake to 12 early to midlactation Holstein cows in a replicated 4 x 4 Latin square design with a 2 x 2 factorial arrangement of treatments. No significant interactions were detected between Ca salts of fatty acids and ration NDF content. The Ca salts of fatty acids lowered milk protein percentage. Cows increased yield of milk, fat, and 4% FCM when they were fed Ca salts of fatty acids. Intake of DM and NE1 increased when NDF was 25% rather than 31% of the total mixed ration. Milk from cows fed 25% NDF contained less fat and more protein. Yields of milk, fat, protein, and 4% FCM increased when diets contained 25% NDF. Conversion of DM intake to 4% FCM, however, decreased. Apparent digestibility of DM increased when diets contained 25% compared with 31% NDF. In this study, Ca salts of fatty acids increased yields of milk and 4% FCM, regardless of ration NDF content. Production increased but efficiency decreased when diets contained 25% vs. 31% NDF.

nutritive value of corn, barley, wheat, and forage oats as silage for lactating dairy cows. Can. J. Whole crops of corn, barley, wheat, and forage oats were ensiled and fed as the sole forage to 48

Rations with target DM proportions of 35, 45,and 65%, attained by soaking the grain mix in water for 24 h, were fed to 46 mid to late lactation, multiparturient dairy cows in two experiments (Experiment 1, 35 and 45% DM; Experiment 2, 45 and 60% DM) to examine the effect of DM percentage of the totally mixed ration on intake and production of cows. Water-soaked concentrate and alfalfa silage were mixed daily and fed ad libitum. Dry matter intake and milk yield and composition were not influenced by the moisture content of the mixed ration in either experiment. Ruminal pH, ammonia N concentration, total VFA, and molar proportions of individual VFA also were not influenced by ration DM in either experiment. Results suggest that rumen water efflux, as influenced by addition of water to the concentrate portion of the mixed ration, is not a factor limiting intake in dairy cows fed high moisture mixed rations.

Twenty-seven dairy cows in midlactation were utilized in two experiments using 15 and 12 cows to determine effects of varying the delivery of ruminally undegraded protein on feed intake, milk production, and some rumen and plasma characteristics. In Experiment 1, cows consumed alfalfa silage ad libitum and one of three barley-based concentrates with either soybean meal (a rapidly rumen degraded protein source), corn gluten meal (a slowly degraded protein source), or an equal mixture of the two, fed at the rate of .36 kg/kg of milk produced. In Experiment 2, cows were fed total mixed diets based upon alfalfa silage, barley, and either soybean meal, corn gluten meal, or a mixture of soybean meal and whey powder (a protein source very rapidly degraded in the rumen). In sacco incubation procedures were used to estimate degradability of protein in all diets. All diets exceeded Agricultural Research Council recommendations for rumen degraded and undegraded protein as well as NRC recommendations for degraded protein. However, one to three of the six total diets, depending upon assumed ruminal turnover rates, did not meet NRC recommendations for undegraded protein. Production parameters, include DMI as well as milk yield and composition, were not influenced by diet in either experiment. Results do not support NRC recommendations for ruminally undegraded protein for midlactation dairy cows producing about 30 kg/d of milk and broadly support the lower recommendations of the Agricultural Research Council. Results also appear to question use of dietary energy intake to predict net rumen microbial protein yield.

ABSTRACT