The effect of the source of nitrogen supplementation on nitrogen balance, rates of plasma leucine turnover, protein synthesis and degradation in sheep

Abstract

Combined experiments of the isotope dilution method of [1-(13)C]leucine, open-circuit calorimetry and nitrogen (N) balance test were used to determine the effect of the source of N supplementation on N balance, whole body protein synthesis (WBPS) and degradation (WBPD) in sheep. The experiment was performed in a replicated 3 × 3 Latin square design. The control diet consisted of timothy hay, ground maize and soybean meal. The urea diet was the control diet supplemented with 1.5% urea. The SBM diet contained the same N and metabolisable energy as the urea diet, which was reached by changing ground maize and soybean meal weights of the control diet. Nitrogen retention was greater (p < 0.05) for the urea diet than the control and SBM diets. Plasma urea concentrations were highest for the SBM diet, followed by the urea diet, and the control diet was lowest. The WBPS and WBPD did not differ between diets, but were numerically lower for the urea and SBM diets. These results suggest that in sheep, urea supplementation influenced N retention without clear changes in WBPS and WBPD.

Effect of grinding process of steam-rolled barley grain on plasma glucose and leucine kinetics and protein synthesis in sheep

“…Plasma α-KIC enrichments were used for calculation of LeuTR as described previously (Sano et al 2009). Whole-body protein synthesis (WBPS) was calculated from the equation as described by Schroeder et al (2006).…”

“…Concentrations of plasma NEFA were enzymatically determined using the diagnostic kit (NEFA C test, Wako, Japan). Concentrations of VFA in the rumen fluid were determined with gas chromatography (HP-5890, Hewlett Packard, USA) after steam distillation, as described previously (Sano et al 2009). Ammonia concentrations in rumen fluid were determined by a colorimetric method (Weatherburn 1967).…”

Effects of urea and soybean meal supplementation on rates of plasma leucine turnover and protein synthesis in sheep fed concentrate-based diets

“…Plasma LeuTR, LeuOX and WBPS were calculated as described previously (Sano et al 2009 where E CO 2 is the isotope enrichment of exhaled 13 CO 2 and V CO 2 is the CO 2 production rate. Recovery fraction of the exhaled CO 2 production in the animal body was estimated to be 0.81 as described by Allsop et al (1978).…”

“…However, little information is available focusing on the effect of N supplementation on whole body kinetics of amino acid and protein metabolism using an isotope dilution method. Sano et al (2009) reported that in sheep fed roughage-based diets, whole body protein synthesis (WBPS) and degradation, using the [1- 13 C]leucine (Leu) technique, remained unchanged with supplementation of urea and SBM. On the contrary, availability of soluble carbohydrates influenced microbial protein synthesis in the rumen of cattle (Rooke and Armstrong 1989).…”

“…Concentrations of ammonia in rumen fluid and plasma and of plasma insulin were determined using diagnostic kits (Ammonia-test wako, Wako and IRI 'Eiken', Eiken Chemical, Japan). Concentrations of VFA in rumen fluid were determined by steam distillation and gas chromatography (HP-5890, Hewlett Packard, USA) as described previously (Sano et al 2009). Nitrogen contents in diets were determined by the Kjeldahl method (Tecator Digestor System and Kjeltec 2300, Foss Tecator, Sweden).…”