Calcium salts of fatty acids in diets that differ in neutral detergent fiber: effect on lactation performance and nutrient digestibility.

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.