Lactational performance and nutrient utilization in high producing cows fed sorghum grains of varying starch degradabilities with or without fat supplementation

Abstract

Twenty-four multiparous and twelve primiparous Holstein cows were assigned at calving to four treatments in a 2 x 2 factorial design. Factors were: (1) grain processing: dry rolled sorghum (D) vs. steam flaked sorghum (S); (2) rumen inert fat: supplemented (F) vs. non supplemented (C). The F diets were supplemented at 2.5% of dry matter (DM) as Ca-soaps. The S diets increased (P<.02) milk production 12%, while F diets decreased (P<.28) milk 5%, due to a 16% decrease (P<.01) in feed intake. However, F diets increased (P<.01) efficiency of feed utilization 15%, partially sustained by greater (P<.08) body weight losses. The DF diet decreased milk protein 0.21% compared to the DC diet, but the S diets had similar milk protein content regardless of fat supplementation. Milk protein yields were higher (P<.01) for S diets. The S diets decreased (P<.03) milk fat percentages but yields were not affected. The S diets had higher (P<.01) digestibilities for DM, CP, GE, and starch than D diets. Digestibilities of CP and GE were higher (P<.05) for F than C diets. Steam flaked sorghum grain maintained milk protein percent in lactation diets supplemented with Ca-Soaps of fatty acids.