| Starch is an important energy source for ruminants,and the regulation of starch digestion sites can affect the efficiency of ruminant utilization of starch.Starch is degraded in the rumen of ruminants to produce volatile fatty acids(VFA),and is degraded by glucose in the small intestine.The energy efficiency of the former is about 70% of the latter.Moderately reducing the content of rumen degradable starch(RDS)and increasing the level of intestinal starch digestion can help improve energy efficiency and promote growth and development,but the mechanism is still unclear.Studies have shown that glucose levels can regulate protein translation at multiple levels through the AMPK pathway to maintain energy balance.This experiment assumes that proper reduction of dietary RDS levels can enable more starch to enter the small intestine and be degraded into glucose,which can affect the glucose and lipid metabolism and protein metabolism of ruminants by regulating the AMPK pathway.In this trial,32 Saneng goats in good health(weight 13.6 ± 0.23 kg,3 months old)were randomly assigned to the LRDS and HRDS groups(n = 16),and fed with low-RDS(LRDS)or high-RDS(HRDS)total mixed diet.The level of RDS is controlled by crushing and whole-grain corn..The pre-feeding period was 1 week,and the trial period was 28 weeks.In this experiment,blood plasma was collected from dairy goats before morning feeding at the 11 th and 27 th week of the trial period.Sheep were slaughtered at the 12 th and 28 th week of the experimental period.Eight sheep were slaughtered in each group.Carcass,liver,muscle and adipose tissue were weighed and sampled.The results and conclusions are as follows:1.Compared with HRDS,LRDS significantly improved the carcass net meat rate of 6-month-old and 10-month-old dairy goats and the net meat rate of 6-month-old dairy goats(P < 0.05),tending to increase the net meat rate of 10-month-old dairy goats(P = 0.073);LRDS significantly inhibited the expression of GYS1 in the liver of 6-month-old dairy goats(P <0.05).RDS had no significant effect on the expression of other key enzymes in the metabolism of carbohydrates and lipids in livers of 6-month-old and 10-month-old dairy goats(P > 0.05),nor on the phosphorylation level of AMPK in liver.2.RDS had no significant effect on the level of AMPK phosphorylation of adipose tissue of 6-month-old dairy goats and gene expression of key enzymes in lipid metabolism(P> 0.05);LRDS significantly inhibited AMPK phosphorylation of adipose tissue of 10-month-old dairy goats Levels(P < 0.05),and increased the expression of genes that promote fatty acid synthesis(P < 0.05).RDS can regulate fat synthesis through the AMPK pathway in 10-month-old dairy goats.3.RDS has no significant effect on the concentration of skeletal muscle crude protein,phosphorylation levels of AMPK and S6 K in 6-month-old dairy goats(P > 0.05),but LRDS tends to reduce the expression of GLDH,an amino acid breakdown gene of skeletal muscle(P = 0.056);LRDS increased the concentration of skeletal muscle crude protein(P <0.05),decreased the concentration of total amino acids in blood before morning feeding(P <0.05),and inhibited the phosphorylation of AMPK and GCN2 downstream target protein e IF2α in skeletal muscle of 10-month-old dairy goats(P < 0.05),and promoted the phosphorylation of skeletal muscle m TORC1 downstream target protein S6K(P < 0.05),In addition,LRDS also promoted the gene expression of glucose transporter 4 and branched-chain amino acid transporter LAT1 ligand 4F2 hc in skeletal muscle of 10-month-old dairy goats(P < 0.05),and had no significant effect on the expression of GLDH(P > 0.05).RDS can regulate skeletal muscle protein synthesis through the AMPK-m TOR-S6 K pathway and the GCN2-e IF2α pathway in 10-month-old dairy goats;LRDS may regulate the net meat rate and carcass rate of 6-month-old dairy goats by inhibiting the degradation of skeletal muscle.In summary,proper reduction of RDS can promote fat synthesis and protein synthesis of skeletal muscle in dairy goats,which is beneficial to growth and development. |
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