Effect of sorghum grain processing and protein source on performance and nutrient utilization by lactating dairy cows

Abstract

Three experiments were conducted to determine the effects of grain processing, grain sources, lactational performance and nutrient digestion in dairy cows. In trial 1 (56 d), 40 cows were divided into five groups and fed diets containing 40% grain as dry-rolled sorghum (DRS, 643 g/L), steam-flaked sorghum (SF) processed to result in three different flake densities: SF34 (34 lb/bu or 437 g/L), SF28 (28 lb/bu or 360 g/L), and SF22 (22 lb/bu or 283 g/L); and dry-rolled barley (DRB). Feeding steam-flaked sorghum grain or dry-rolled barley did not increase milk yield and milk protein content and yield. However, due to a lower intake of dry matter, feed efficiency was 10 to 19% higher for flaked sorghum and barley diets compared with DRS. Steam-flaking also decreased milk urea-N and tended to increase milk casein. In trial 2 (58 d), 32 lactating cows were divided into four groups and fed diets containing 39% sorghum grain as dry- rolled sorghum (DRS), or steam-flaked sorghum (SF) processed to result in similar flake densities as trial 1: SF34 (34 lb/bu or 437 g/L; SF28 (28 lb/bu or 360 g/L); and SF22 (22 lb/bu or 283 g/L). When sorghum grain was moderately flaked (SF34 and SF28) milk and 3.5% FCM yields were not increased compared to DRS, however, efficiency of feed utilization again was higher for SF34 and SF28 due to lower intake of dry matter. The very thin flake (SF22) had a negative effect on milk and 3.5% FCM compared with DRS, SF34, and S F2 8. Digestibilities of nutrients were increased by steam-flaking compared with dry-rolling. In trial 3 (58 d) twenty four cows were assigned to three treatments in which diets contained.8% urea (Urea), 6% soybean meal (SBM), or 5% fish meal (FM) as the protein sources. Intake of DM was highest for Urea, intermediate for SBM, and lowest for FM. Higher producing cows (46 Kg/d of milk) responded more positively in milk and FCM yields and feed efficiency to SBM and FM compared with those fed Urea. Cows producing about 35 Kg/d of milk tended to perform better when fed Urea than when fed SBM or FM. Digestibilities of nutrients were not affected greatly by protein source.