Abstract
Four ruminally fistulated Finnish Ayrshire cows were used to study the effects of different protein supplements on concentration and flow of soluble non-ammonia N (SNAN)into the omasum.The treatments in a 4 × 4 Latin square design were a basal diet of grass silage and barley and the basal diet supplemented with fishmeal, soybean meal and maize gluten meal. Protein supplements significantly increased concentrations of peptide N (P=0.009)and total SNAN (P =0.03)fractions in omasal digesta.Peptide constituted the largest proportion of SNAN flow into the omasum indicating that hydrolysis of peptides to amino acids is the most limiting step in rumen proteolysis.The microbial contribution to SNAN was on an average 0.64 indicating that a large proportion of SNAN flow leaving the rumen was of microbial origin.The estimated SNAN flow per kg dry matter intake from the basal diet and protein supplemented diets indicated that approximately 49,22 and 37 g kg-1 of fishmeal,soybean meal and maize gluten meal protein, respectively, escaped from ruminal degradation as SNAN.;
Highlights
Robinson and McQueen 1994) or omasal digesta (Choi et al 2002a, b) suggest that a proportion of protein can escape rumen degradation in the liquid phase. Broderick (1987) reported using in vitro system that the degradation rate of casein N was 0.40 – 0.60 h-1, suggesting that a considerable portion of casein N can escape ruminal degradation
Intake and digesta flow into the omasal canal where SNANcont, DMIbasal and DMIcont are the flow of soluble non-ammonia N (SNAN) in the liquid phase of omasal digesta for control diet, dry matter (DM) intake as grass silage and barley concentrate in the protein supplemented diet and DM intake in control diet excluding mixture of vitamin and mineral, respectively
The present concentration of peptide N and/or total SNAN was rather similar between protein supplemented-diets, even though the soluble N composition differed in protein feeds
Summary
Four ruminally fistulated Finnish Ayrshire cows were used to study the effects of different protein supplements on concentration and flow of soluble non-ammonia N (SNAN) into the omasum. The treatments in a 4 × 4 Latin square design were a basal diet of grass silage and barley and the basal diet supplemented with fishmeal, soybean meal and maize gluten meal. The microbial contribution to SNAN was on an average 0.64 indicating that a large proportion of SNAN flow leaving the rumen was of microbial origin. The estimated SNAN flow per kg dry matter intake from the basal diet and protein supplemented diets indicated that approximately 49, 22 and 37 g kg-1 of fishmeal, soybean meal and maize gluten meal protein, respectively, escaped from ruminal degradation as SNAN
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