Effect of processed grain sorghum and expeller soybean meal on performance of lactating cows

Forty-four Holstein cows were used to measure milk production responses to dry-rolled versus pelleted grain sorghum and expeller versus solvent soybean meal in a 2 x 2 factorial arrangement of treatments. Pelleted grain sorghum was processed by grinding, increasing moisture to 31%, extruding, and drying to an exist temperature of 93 degrees C. Grain sorghum was included in the diets at 27% of dry matter, and soybean meal was the primary source of supplemental protein. Few interactions were observed between the methods of processing grain sorghum and sources of soybean meal. Pelleting of grain sorghum decreased dry matter intake 5%, but increased milk production 3%, protein yield 4%, and efficiency 7%; fat yield was unaffected. Replacement of solvent soybean meal with expeller soybean meal had little effect on intake, but increased milk production 3%, fat yield 5%, and efficiency 4%; protein yield was unaffected. Plasma concentrations of amino acids (AA) were increased by pelleted grain sorghum and by expeller soybean meal at 5 and 10 wk after initiation of treatment, indicating that both of these treatments increased the supply of AA to the intestine. Pelleting improved the nutritive value of grain sorghum for lactating cows. Although total milk production and fat yield increased in response to expeller soybean 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 supply of AA to the intestine.