Saccharomyces cerevisiae fermentation product in dairy cow diets containing dried distillers grains plus solubles.

Sixteen multiparous Holstein cows (127+/-52 d in milk) were used in 4 replicated 4 x 4 Latin squares with 4-wk periods to evaluate interactions of dietary inclusion of a fermentation product of Saccharomyces cerevisiae (SC; XPC, Diamond V Mills, Cedar Rapids, IA) and dried distillers grains plus solubles (DDGS) on production of milk and milk components when fed diets containing approximately 30% dietary neutral detergent fiber with calculated forage neutral detergent fiber of 19.3% of diet dry matter (DM). Treatments were a 2 x 2 factorial arrangement with SC included at 0 or 14 g/d and DDGS at 0 or 20% of diet DM. Diets consisted of 27% corn silage, 18% alfalfa hay, and 55% concentrate mix on a DM basis. Diets not containing DDGS included additional corn, soybean meal, expeller soybean meal, soyhulls, and rumen inert fat to remain isocaloric and isonitrogenous with DDGS diets. Dry matter intake (26.0 kg/d) was similar for all diets. Milk production increased with the addition of SC to diets (43.6 vs. 42.0 kg/d for diets without SC) and decreased for cows fed diets containing DDGS (42.0 kg/d vs. 43.6 kg/d for diets not containing DDGS). Milk fat percentage (3.05 vs. 3.22% for DDGS and non-DDGS diets, respectively) and yield (1.27 vs. 1.41 kg/d) were decreased by the addition of DDGS but were not affected by the addition of SC. Concentrations of long-chain, polyunsaturated, trans-, and conjugated fatty acids in milk of cows fed DDGS were increased, but milk fatty acid profiles were not affected by SC. Milk true protein concentrations were similar for all diets; however, the addition of SC increased yield of true protein (1.32 vs. 1.27 kg/d). Concentrations of milk urea nitrogen increased when SC was included in the diet with DDGS. The DDGS decreased yields of energy-corrected milk (39.4 vs. 42.1 kg/d) and tended to decrease feed efficiency (1.53 vs. 1.61 kg of energy-corrected milk/kg of dry matter intake). Body weights and condition scores were not affected by treatments. Results suggest that diets containing minimal amounts of forage fiber and DDGS at 20% of diet DM will contribute to decreased milk production and milk fat depression. The addition of SC did improve milk and milk protein yields but did not prevent milk fat depression caused by DDGS. Production responses to SC were similar when cows were fed DDGS or non-DDGS diets.

Feed efficiency of mid-lactation dairy cows fed yeast culture during summer.

Thirty-eight Holstein cows (26 multiparous and 12 primiparous), that averaged 105 d postpartum at the start of the experiment, were used to evaluate the feeding of yeast culture (60 g/cow daily of Diamond V XP) on production efficiency during hot summer weather. From early June until early September and after a 2-wk covariate period, cows were fed a control diet without or with 60 g of yeast culture/cow daily for 12 wk. Weekly daytime high temperatures in the free-stall barn during the 12-wk period averaged 33 degrees C (28 to 39 degrees C). Total mixed diets on a dry matter (DM) basis consisted of corn silage (28%), alfalfa hay (21%), and a concentrate mix (51%) without or with the yeast culture added to the total mixed ration at the time of feeding. Milk production (34.9 and 35.4 kg/d, for control and yeast culture treatment, respectively), 4% fat-corrected milk (31.2 and 32.0 kg/d), energy-corrected milk (ECM; 33.4 and 34.2 kg/d), and DM intake (23.1 and 22.1 kg/d) were similar for cows fed control and yeast culture diets. Percentages of milk fat (3.34 and 3.41) and true protein (2.85 and 2.87) were similar for both diets. Feed efficiency defined as kilogram of ECM/kilogram of DM intake was improved by 7% for cows fed the yeast culture. Body weights and body condition scores were similar for both groups. The results suggest that the yeast culture can improve feed efficiency of heat stressed dairy cows in midlactation.