Comparative Study Of Lipid And Protein Metabolism Under Natural Grazing And Stall-Fattening Conditions In Albas White Cashmere Goats

This experiment was conducted to study the changes of fatty acids (FA) and amino acids (AA) in Albas white cashmere kid goat and adult goats under natural grazing and stall fattening conditions. The aim was to find the key factors that influence the composition of FA as well as AA in goat meat by means of studying blood and tissue biochemical indexes, gene and protein expression related to lipid and protein metabolism, and dietary composition. The results provided theoretical basis for the improvement of the quality and flavor of mutton by the dietary modification. The experiment designed in 2x2 factorial arrangement. The total of sixty healthy weaned 4-month old Albas white cashmere kid goat (KG,20.36±0.32kg) and sixty 5-year old adult goat (AG,40.38±0.84kg) were selected and then divided into 4 groups of thirty animals each. And the main effects were fattening ways (natural pasture fattening (PF) vs. stall fattening (SF, ingested Total Mixed Ration) and age (AG and KG). The experiment period of AG lasted for 60 days divided into the early stage of the fattening (1-30d) and late stage of fattening (31-60d). The fattening period of KG lasted for 90 days which was divided into early fattening period (1-30d), mid fattening period (31-60d) and late fattening period (61-90d). At the end of the each fattening trial,6 goats were selected from each feeding groups to collect blood samples under the empty stomach and slaughtered for collecting longissimus dorsi, triceps, biceps femoris, gluteus, subcutaneous fat, pararenal fat, tail fat, intestinal fat and omental fat.This trial was further divided into 6 experiments:Experiment one was comparative study of the composition of FA and AA in diets of chashmere kid goats and adult goats under the natural grazing and stall fattening conditions. Experiment two and three were conducted to study the differences of FA and AA in mutton of chashmere kid goats and adult goats respectively, investigated the effects of fattening ways and animal age on quality of mutton. Experiment four was conducted to study the changes rule in blood biochemical indicators and enzyme activities related to lipid and protein metabolism of cashmere goats AG and KG under the natural grazing and stall fattening conditions, investigated the effects of fattening ways and animal age on lipid and protein metabolism. Experiment five and six was conducted to study the changes rule of mRNA and protein expression of lipid and protein metabolism genes in cashmere goats AG and KG under the natural grazing and stall fattening conditions, The main objects were to determine differences in meat quality by ways of fattening and how gene transcription and protein expression levels affected this.The following results are obtained under the experimental conditions:(1) Compared with PF group, SF group had a higher content and intake of SFA, mainly C16:0 and C18:0, and including C17:0, C15:0, C20:0, C13:0; MUFA, mainly C18:ln-9c, including C15:1, C18:ln-9t, C22:ln-9 and C17:1; co-6PUFA, mainly C18:2n-6c, including C22:2n-6, C18:2n-6t and C20:4n-6; had a lower content and intake of ω-3PUFA, mainly C18:3n-3, including EPA.(2) Compared with PF group, SF group had a higher content and intake of EAA, mainly Leu and Arg, and then Thr, His and Val; had a higher content and intake of NEAA, mainly Glu, then Tyr, Cys, Ala and Ser; had a higher content and intake of LAA, mainly Met; had a higher content and intake of BCAA, mainly Leu, then Val; had a higher content and intake of FAA, mainly Glu, and then Leu and Arg; had a higher content and intake of DAA, mainly Glu, then Arg, Cys, Ala and Met.(3) Compared with PF group, the contents of SFA in the most muscle and fat tissues of SF group were higher, especially C18:0, including C16:0, C14:0, C20:0, C17:0, C22:0, C10:0, C8:0; the contents of MUFA, mainly C18:ln-9c; the contents ofco-6PUFA were higher, mainly C18:2n-6c, including C18:3n-6 and C20:3n-6; the contents of ω-3PUFA and PUFA were lower in SF group, mainly C18:3n-3, then EPA and DHA. Compared with KG group, the contents of SFA in the most muscle and fat tissues of AG group were higher, especially C18:0 and C16:0, including C4:0, C10:0, C12:0, C14:0, C15:0, C21:0, C22:0 and C24:0; the contents of MUFA of AG group were lower, mainly C18:ln-9c, including C18:ln-9t; the contents of PUFA and co-3PUFA were lower in AG group, mainly C18:3n-3, including EPA and DHA.(4) Compared with PF group, the contents of EAA in most muscle tissue, mainly Leu, followed by Lys, Val, His, Phe, Met were significantly higher in SF group; the content of NEAA, mainly Tyr, including Pro were significantly higher in SF group; the BCAA of SF were higher, mainly Leu, and then val. Compared with AG group, the contents of EAA in most muscle tissue, mainly Val, followed by Arg, Leu, Lys, Thr, Phe were higher in KG group; the content of NEAA, mainly Glu, including Asp, Ala, Gly, Ser were higher in KG group; the content of BCAA in KG were higher, mainly Leu, and then val; the content of FAA in KG were higher, mainly Glu, and then Leu and Arg; the content of DAA were higher in KG, mainly Glu, followed by Asp, Ala, Arg.(5) Compared with PF group, the contents of TP, TG, BUN, CHO, LDL-C, GLU, T3, INS, IGF-1 in plasma and the enzyme activity of ACC, FAS, MDH, LPL, SCD, pGSK3β in serum, liver tissue, subcutaneous fat tissue and longissimus dorsi were significantly higher in SF group, but the contents of NEFA, HDL-C, COR, Leptin and the enzyme activity of HSL, BCAT2, BCKD and GSK3β were on the contrary. Compared with KG, there was a significant increase in TG, LDL-C, INS and PG in serum and the enzyme activity of ACC and pGSK3β in serum and tissues in AG, but the contents of NEFA, TP, BUN, HDL-C, LDL-C, GLU, HGH, Leptin, IGF-1 and the enzyme activity of LPL, HSL and SCD were on the contrary.(6) Compared with PF group, the mRNA expression of ACC, FAS, DGAT1, SCD, LPL, SREBP-1c and C/EBPa were higher in muscle, fat and liver tissue in SF group, but the mRNA expression of HSL, PPARy, Pref-1 and β-catenin were lower. Compared with KG, the mRNA expression of ACC, DGAT1, SREBP1c, C/EBPα were significantly higher in muscle, fat and liver tissue of AG, but the mRNA expression of SCD, Pref-1, HSL, LPL and β-catenin were lower in AG. The rule of protein expression basic consistent with the law of gene transcription in Wnt signaling pathway.(7) Compared with PF group, the mRNA expression of mTOR, S6K1 and eIF4G were significantly higher in SF group, but 4EBP1 was significantly lower in SF group. Compared with KG, AG down regulated the mRNA expression of mTOR and S6K1, and up regulated the mRNA expression of 4EBP1. The rule of protein expression basic consistent with the law of gene transcription in mTOR signaling pathway.Integrated the above, from the perspective of the fatty acids nutrition, the results concluded that nutritional value of meat in natural grazing cashmere goats was better than that in stall fattening goats. Kid goats’meat nutritional value was better than adult goats. Under the condition of two kinds of fattening ways, the differences between FA content and composition were the main reason for the differences of meat nutrition value. Compared with natural grazing, the dietary PUFA was lower in stall-fattening, which lead to increasing SFA and MUFA concents in tissue caused by increasing the genes expression level of enzyme related to the de novo synthesis of fatty acids ACC, FAS and SREBP-1c, which in turn to increasing activities of enzyme related to the de novo synthesis of fatty acids ACC, FAS, SCD and MDH in tissue and INS and IGF-1 content in blood. Dietary C18:2n-6c, C18:3n-3 and EPA are the main factors resulting in the differences profiles of corresponding fatty acids in the body tissue.From the perspective of the protein nutrition, muscle amino acid profile in stall fattening goats was better than that in the natural grazing goats. Muscle amino acid profile in kid goats was better than that in adult goats. Its mechanism might be related to diets with different AA content and composition under the two different fattening ways. Compared with natural grazing, the dietary Leu content was higher and increased the concentrations of blood INS and IGF-1 in stall-fattening goats, which acitivated mTOR signaling pathway, which in turn promotes protein synthesis through increasing the mRNA and phosphorylation protein expression level of mTOR, S6K1 and 4EBP1. Stall-fattening goats increase in BCAA is result of a decrease in BCAT2 and BCKD activities in muscle tissue.