EFFECT OF PROCESSED GRAIN-SORGHUM AND EXPELLER SOYBEAN-MEAL ON PERFORMANCE OF LACTATING COWS

Forty-four Holstein cows were used to measure milk production response s to dry-rolled versus pelleted grain sorghum and expeller versus solv ent soybean meal in a 2 x 2 factorial arrangement of treatments. Pelle ted grain sorghum was processed by grinding, increasing moisture to 31 %, extruding, and drying to an exit temperature of 93 degrees C. Grain sorghum was included in the diets at 27% of dry matter, and soybean m eal was the primary source of supplemental protein. Few interactions w ere observed between the methods of processing grain sorghum and sourc es of soybean meal. Pelleting of grain sorghum decreased dry matter in take 5%, but increased milk production 3%, protein yield 4%, and effic iency 7%; fat yield was unaffected. Replacement of solvent soybean mea l with expeller soybean meal had little effect on intake, but increase d milk production 3%, fat yield 5%, and efficiency 4%; protein yield w as unaffected. Plasma concentrations of amino acids (AA) were increase d by pelleted grain sorghum and by expeller soybean meal at 5 and 10 w k after initiation of treatment, indicating that both of these treatme nts increased the supply of AA to the intestine. Pelleting improved th e nutritive value of grain sorghum for lactating cows. Although total milk production and fat yield increased in response to expeller soybea n meal, the lack of response in protein yield to this increased supply of RUP indicated that the effect was not solely due to an increased s upply of AA to the intestine.