Effect of metabolizable protein intake on rates of plasma leucine turnover and protein synthesis in heifers

Abstract

SUMMARYAn isotope dilution method using [1-13C]leucine (Leu) infusion together with open-circuit calorimetry was applied to determine the effect of metabolizable protein (MP) intake on rates of plasma Leu turnover and whole body protein synthesis (WBPS) in six heifers. WBPS rate was estimated from rate of plasma Leu turnover and Leu oxidation to carbon dioxide. The experiment consisted of three levels of MP intake and was conducted in a two 3×3 Latin square designs of three 21-day periods. The experimental diet consisted of mixed hay, maize and soybean meal. Dietary MP intake of each dietary treatment was 4·3, 4·5 and 4·9 g/kg BW0·75/day by changing maize and soybean meal weights. Metabolizable energy (ME) intake was similar for all dietary treatments. When plasma α-[1-13C]keto-isocaproic acid enrichments were used as markers indicating intracellular Leu enrichments, plasma Leu turnover rate (LeuTR) increased (P=0·012) and WBPS tended to increase (P=0·091) as MP intake increased. In contrast, plasma LeuTR and WBPS were not influenced if plasma [1-13C]Leu was taken to indicate intracellular Leu enrichments. Total and plasma Leu oxidation rates did not change but intracellular Leu oxidation increased (P=0·044) with increasing MP intake. In heifers, it is suggested that rates of plasma Leu turnover and WBPS are influenced by dietary MP intake, independent of ME intake, although the change in MP intake was relatively small.

Effect of feeding garlic leaf on microbial nitrogen supply, kinetics of plasma phenylalanine, tyrosine and protein synthesis in sheep

“…This might be due to the fact that frozen garlic leaf retained more bioactive components than garlic leaf silage. Turnover of plasma amino acids and WBPS increased with increasing dietary energy and protein intake in ruminants (Fujita et al 2006;Sano et al 2008). Thus, Sano et al (2008) used different levels of CP intake in heifers and found that LeuTR and WBPS were significantly greater for the high CP intake group than for the low and medium CP intake groups.…”

“…Turnover of plasma amino acids and WBPS increased with increasing dietary energy and protein intake in ruminants (Fujita et al 2006;Sano et al 2008). Thus, Sano et al (2008) used different levels of CP intake in heifers and found that LeuTR and WBPS were significantly greater for the high CP intake group than for the low and medium CP intake groups. Fujita et al (2006) determined WBPS using the [ 2 H5]Phe model and reported that WBPS increased in response to increasing energy intake in adult goats.…”

“…Thus, Sano et al . () used different levels of CP intake in heifers and found that LeuTR and WBPS were significantly greater for the high CP intake group than for the low and medium CP intake groups. Fujita et al .…”

Effects of diet and cold exposure on rates of plasma leucine turnover and protein synthesis in sheep

“…75 per h through the same catheter for 6 h. A blood sample (5 ml) was taken immediately before and four blood samples (5 ml) were taken at 30-min intervals during the last 90 min of [1-13 C]Leu infusion. Samples were transferred into centrifuge tubes containing heparin sodium and were chilled in ice until centrifugation (Sano et al 2004(Sano et al , 2008.…”

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

“…Therefore, quantity and quality of diets and production rate or molar ratio of VFA in the rumen are closely related to intermediary metabolism in ruminants (Sutton et al 2003). To clarify the relationship, researches were conducted by changing sources of diets, roughage: concentrate ratio, and by providing VFA salt supplementation to diets and VFA infusion into the rumen (Harmon et al 1983;Gross et al 1990;Fujita et al 2006;Sano et al 2008). However, these methodologies involve in factors of different dietary sources, supplements or infusates.…”