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Rumen Microbial Protein Synthesis in Multigrain and Barley Fed lactating Dairy Cows
The objective of this research was to estimate rumen microbial protein synthesis in response to feeding diets based on either solely barley grain or a choice of multiple grains. Eight multiparous (642 ± 57 kg body weight; 72 ± 58 days in milk; mean ± SD) lactating Holstein cows were studied in a cross-over design experiment with two 21-d periods. Cows were housed and managed in free individual boxes and fed alfalfa hay-corn silage based total mixed rations with either barley as the only grain (BR) or a mixture of barley, corn, wheat and sorghum (MG). Proportion of cereals in the multigrain treatment was equal, each being 25%. Grains were included as 30% of total dietary dry matter. Diets were prepared as total mixed rations and offered for 5-10% daily orts. Cows were milked at 0500, 1300 and 2100 h and fed at 0530, 1330 and 2130 h. Two ml of urine sample was taken daily from the whole collection during the third week of both experimental periods, diluted 5 times in distilled water, and stored at -20°C for analysis of purine derivatives including allantoin and uric acid to estimate duodenal flow of microbial proteins. Statistical data analysis was conducted using Mixed Models Procedures of SAS program. Feeding MG vs. BR numerically increased (P<0.12) daily urinary excretion of allantoin (445 vs. 428 mmol/d), uric acid (49 vs. 39 mmol/d), and total purine derivatives (494 vs. 467 mmol/d), respectively. Findings suggest that feeding a multigrain choice of barley, wheat, corn and sorghum instead of solely barley grain secures healthy rumen fermentation and adequate microbial protein synthesis. Increased rumen pH and improved feed intake by feeding MG vs. BR supports the rumen microbial protein response and provides metabolic implications on improved viability of MG diets.
Keywords: Multigrain, Rumen, Microbial protein