|De leon, N|
Submitted to: Journal of Dairy Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 6/7/2000
Publication Date: N/A
Citation: Interpretive Summary: Much of the protein required by dairy cows to make milk is provided by the microbes living in the rumen (the first compartment of the cow's stomach); these microbes can form true protein from nonprotein nitrogen. If protein synthesis by the rumen microbes could be increased, then the cow's need for costly feed protein supplements would be reduced. Commercial companies claim that a number of fermentation byproducts will stimulate microbial protein formation in the rumen. We conducted feeding trials to test whether commercial fermentation byproducts would serve as effective nitrogen supplements for dairy cows. Six supplements were tested: four that were fabricated from the materials normally used to produce fermentation byproducts plus two byproducts that are commercially available. These were compared to supplemental nitrogen fed as urea (a low-cost source of nonprotein nitrogen) and soybean meal (a standard true protein source). Diets contained the same amounts of alfalfa silage, corn silage and high moisture corn grain; equal amounts of nitrogen from each supplement were included in the experimental diets. Cows ate the most feed and produced the most milk when they were fed soybean meal. Cows ate similar amounts of feed and produced similar amounts of milk when fed the fabricated byproducts and one commercial byproduct as they did with urea in the diet. Cows actually ate less and gave less milk on the second commercial byproduct than they did on urea. This research indicates that fermentation byproducts are no more effective as protein supplements than urea. Farmers will be able to use this research to decide whether or not to use fermentation byproducts as protein supplements.
Technical Abstract: Two feeding trials were conducted to test the effectiveness of several commercial and experimental fermentation byproducts as N supplements for lactating dairy cows. Trial 1 was a replicated 5x5 Latin square conducted with 25 Holstein cows (five with ruminal cannulae) fed five diets with [dry matter (DM) basis] 28% alfalfa silage, 31% corn silage, 28% high moisture ear corn plus 4 percentage units of CP from: solvent soybean meal, urea, commercial fermentation byproducts 1 and 2, or a blend of fermentation byproducts plus wheat middlings. Diets averaged 15.1% CP and 32% NDF. Intake of DM, BW gain and yield of milk and milk components was greatest on soybean meal; production was similar on urea, byproduct 1 and the byproduct blend. Intake, BW change and milk yield all were lowest when cows were fed supplemental N from byproduct 2. Urine output (estimated using creatinine in spot urine samples) was greater on byproduct 1 and the byproduct blend. There were no differences in microbial synthesis (based on estimated excretion of purine derivatives), in situ DM digestion, and ruminal VFA due to N source. Trial 2 was a replicated 5x5 Latin square conducted with 10 Holstein cows fed five diets containing (DM basis) 37% alfalfa silage, 28% corn silage, 29% high moisture ear corn plus 2 percentage units of CP from: urea, byproduct 1 or one of three blends of fermentation byproducts plus wheat middlings. Except for greater DM intake and slightly lower milk yield/DM intake on the byproduct blends, performance and urinary metabolite excretion were not different due to N supplement. Relative to the other fermentation byproducts and urea, byproduct 1 gave reduced milk urea N in both trials. Fermentation byproducts were no more effective as N supplements than urea under the conditions of these trials.