Abstract
This study investigated the effectiveness of the urine sample collection method in predicting the volume urinary and synthesis of microbial nitrogen. Eight fistulated steers were used with accessible rumens and kept in individual stalls. Their diets consisted of corn silage; corn silage + concentrate; corn silage + concentrate with addition of lipids in the form of soybean oil; and corn silage + concentrate with addition of lipids in the form of soybean grains. Estimates of microbial protein synthesis were obtained based on the urinary excretion of purine derivatives. There was no effect of diets on daily creatinine excretion (P>0.05). There were differences (P<0.05) between the urinary volume and microbial synthesis values determined by the total urine collection and those estimated from the urine spot samples and equations proposed by different authors. The estimation of microbial synthesis based on the urine excretion of purine derivatives should be performed from the total collection of the urine for a period of 24 hours.
Highlights
Crude microbial protein (CPmic) synthesis plays an important role in ruminant nutrition as it provides most of the metabolizable protein requirements, representing 50% to 80% of the amino acids that flow into the animal's small intestine (FIRKINS; YU; MORRISON, 2007; NGUYEN et al, 2017)
Considering the importance of CPmic in the protein nutrition of ruminants, as well as the interest in adding lipids to the diet and the need to obtain simple methods that allow the quantification of the microbial synthesis in a precise way, this study aimed to evaluate the effectiveness of the predicting the volume urinary from urine spot samples, taking the values obtained by total urine collection as a reference and determining a synthesis of microbial protein in confined cattle supplemented or not supplemented with different lipid sources were assessed
The estimated volume of the urine based on the spot sample starting from the actual excretion of creatinine (Estimated-ExR) differed (P
Summary
Crude microbial protein (CPmic) synthesis plays an important role in ruminant nutrition as it provides most of the metabolizable protein requirements, representing 50% to 80% of the amino acids that flow into the animal's small intestine (FIRKINS; YU; MORRISON, 2007; NGUYEN et al, 2017). In this sense, maximizing microbial production efficiency would improve animal productivity (HACKMANN; FIRKINS, 2015). The indication of the spot sample to estimate the excretion of DP may not be applicable when only the urine spot sample is collected
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