Abstract
This study was designed to investigate the effects of dietary starch structure on muscle protein synthesis and gastrointestinal amino acid (AA) transport and metabolism of goats. Twenty-seven Xiangdong black female goats (average body weight = 9·00 ± 1·12 kg) were randomly assigned to three treatments, i.e., fed a T1 (normal maize 100 %, high amylose maize 0 %), T2 (normal maize 50 %, high amylose maize 50 %) and T3 (normal maize 0 %, high amylose maize 100 %) diet for 35 d. All AA in the ileal mucosa were decreased linearly as amylose:amylopectin increased in diets (P < 0·05). The plasma valine (linear, P = 0·03), leucine (linear, P = 0·04) and total AA content (linear, P = 0·03) increased linearly with the increase in the ratio of amylose in the diet. The relative mRNA levels of solute carrier family 38 member 1 (linear, P = 0·01), solute carrier family 3 member 2 (linear, P = 0·02) and solute carrier family 38 member 9 (linear, P = 0·02) in the ileum increased linearly with the increase in the ratio of amylose in the diet. With the increase in the ratio of amylose:amylopectin in the diet, the mRNA levels of acetyl-CoA dehydrogenase B (linear, P = 0·04), branched-chain amino acid transferase 1 (linear, P = 0·02) and branched-chain α-keto acid dehydrogenase complex B (linear, P = 0·01) in the ileum decreased linearly. Our results revealed that the protein abundances of phosphorylated mammalian target of rapamycin (p-mTOR) (P < 0·001), phosphorylated 4E-binding protein 1 (P < 0·001) and phosphorylated ribosomal protein S6 kinases 1 (P < 0·001) of T2 and T3 were significantly higher than that of T1. In general, a diet with a high amylose ratio could reduce the consumption of AA in the intestine, allowing more AA to enter the blood to maintain higher muscle protein synthesis through the mTOR pathway.
Highlights
As a widely grown crop, maize provides sufficient carbohydrates for humans and animals and is a primary source of energy[1]
We hypothesised that feeding diets with different amylose:amylopectin ratios would affect the expression of the amino acid (AA) transporters, regulate the absorption of AA in the gastrointestinal tract
Goats were thereby used as experimental animals to explore the effects of diets with different amylose:amylopectin ratios on intestinal AA transporters’ expression, the activities of enzymes involved in AA metabolism, and mammalian target of rapamycin signalling pathway involved AA accumulation in muscles, intending to reveal how starch types affect animal protein and AA metabolism
Summary
As a widely grown crop, maize provides sufficient carbohydrates for humans and animals and is a primary source of energy[1]. Goats were thereby used as experimental animals to explore the effects of diets with different amylose:amylopectin ratios on intestinal AA transporters’ expression, the activities of enzymes involved in AA metabolism, and mammalian target of rapamycin (mTOR) signalling pathway involved AA accumulation in muscles, intending to reveal how starch types affect animal protein and AA metabolism.
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