Effects And Mechanism Of Three Feeding Modes On Fattening And Slaughter Performance,Meat Quality And Fat Deposition In Body Tissues Of Cashemere Goats

This paper mainly compared the difference of fattening performance,slaughter performance,meat quality,fatty acid composition and cholesterol content of body tissues of cashmere goats under the three feeding modes including stall fattening with total roughage ration and total mixed ration and grazing supplementary feeding,and explored the reasons on these differences from the perspective of rumen fermentation,nutrient digestion,biochemical indiex and fatty acid of blood.Based on this,the mechanism on fat deposition of different feeding modes in cashmere goats was investigated by the activity and gene expression of the enzyme related to fat metabolism.The results provides theoretical basis and reference for the improvement of the quality and nutritional value of mutton by the diet regulation,and provides data support for the rational use of roughage resources and the scientific formulation of fattening programs for cashmere goats.This paper mainly includes five experiments.This experiment adopted a single factor randomized block design.The total of sixty healthy weaned male kids with similar weight(19.26±2.57 kg)and age(120±10 d)were selectd,and randomly divided into CON groups(CON),the total mixed ration stall fattening(TMS)and the total roughage ration stall fattening(TRS),each group had 20 animals with 4 replicates and 5 goats per replicate.The CON group is a grazing supplementary feeding group.The goats in this group are grazed on the natural pasture in the daytime,and each goat is supplemented with 300 g of corn(air dried basis)after returning to grazing at night.The goats of TMS group were fed total mixd ration and TRS groups were fed total roughage diet separately.The preliminary trial period was 14 d,and the formal trial period was 90 d.The experientment period is divided into early period(1-30 d),the middle period(31-60 d),and the late period(61-90 d-).During the test period,the growth performance of 3 groups of cashmere goats was determined.At the end of the test,six goats were randomly selected and slaughtered from each treatment group to compare slaughter performance and meat quality.The first experiment mainly compared the effects of three feeding modes on fattening performance,slaughter performance and meat quality of cashmere goats.The results showed as follows:compared with TRS and CON,the ADG and feed efficiency of cashmere goats in TMS group were significantly increased,ADG anf DMI of cashmere goats in TRS group were significantly higher than those in CON group(P<0.05),but the feed efficiency is contrary to the above indicators.Compared with the TRS and CON groups,the carcass weight and slaughter rate of cashmere goats in TMS group were increased significantly(P<0.05).The slaughter rate and carcass weight of cashmere goats in TRS group were significantly lower than that in CON group(P<0.05),and the weight of perirenal fat,omentum fat,mesenteric fat and tail fat,total fat weight,GR value and eye muscle area were lower than in TMS and CON groups.The mesentery fat weight of cashmere goats in TMS group was significantly lower than in CON group(P<0.05).The CP content of the longest dorsal dorsi,triceps and gluteus of cashmere goats in the TRS group were significantly higher than those in the TMS and CON groups(P<0.05),but EE content showed the contrary results to the above indicators.The mutton water loss rate and the cooking loss of cashmere goats in the TRS group was significantly higher than that in the TMS and CON groups(P<0.05),which in turn caused the decreased tenderness of the goat meat.The second experiment mainly compared the effects of three feeding modes on apparent digestibility of nutrients and rumen fermentation of cashmere goats.The results showed as follows:compared with the TMS and CON groups,the digestibility of DM,CP,EE and P of goats in the TRS group was reduced in different degree,while the digestibility of NDF and ADF was increased during the entire fattening period.Compared with the CON group,the digestibility of CP,EE and P(middle fattening period)of cashmere goats in TMS group were significantly increased,but the digestibility of NDF and ADF(except for early fattening period)were significantly reduced(P<0.05).The pH value,content of acetic acid and propionic acid in the rumen liquid of goats in TRS group were significantly higher than those in TMS and CON group(P<0.05).The changes of TVFA,propionic acid and butyric acid concentration were contrary to the above indicators.The propionate concentration in rumen of goats in TMS group was significantly higher than that in CON group(P<0.05),but acetic acid/propionic acid was significantly lower than that in CON group(P<0.05).There was no significant difference in pH between TMS and CON groups(P>0.10).Compared with the TMS group,the protozoa and NH3-N contents in rumen fluid of goats in the TRS and CON group were significantly increased(P=0.028,P=0.002),and the concentrations of isobutyric acid,valeric acid and isovaleric acid were significantly reduced(P<0.0001),but there were no differences in the above paremeters between TRS and CON group(P>0.10).These results suggest that total mixed ration feeding can promote rumen fermentation,thereby improving the digestibility of nutrients(excluding fiber substances),but total roughage ration feeding can improve the digestibility of fiber substances.The third experiment mainly compared the effects of three feeding modes on biochemical indexes and fatty acid composition in blood of cashmere goats.The results showed as follows:the lipid metabolism-related indicators(except CHO)in the serum of goats in the TRS group were lower than in the CON and TMS groups to varying degrees.The TG and LDL contents in cashmere goat serum in the TMS group were significantly higher than those in the CON group,but NEFA showed the opposite result.Compared with the CON and TMS groups,the plasma levels of C18:1n9t,C18:3n3,C20:5n3,C22:6n3,and n-3 PUFA of goats in the TRS group were significantly increased in varying degrees,while the contents of C18:0,C18:2n6c,MUFA and n-6 LCPUFA were all reduced.The levels of C10:0,C11:0,C12:0,C14:0,C24:1,C20:3n3 and n-3 LCPUFA in TMS goat's plasma were significantly higher than those in CON group(P<0.05).These results indicate that total roughage ration and grazing supplementation can improve the blood lipid metabolism and the content of n-3 PUFA of cashmere goat body tissues,moreover,the stall feeding with total roughage ration showed better effect than grazing supplementary feeding.The fourth experiment mainly compared the effects of three feeding modes on the cholesterol and fatty acid composition in body tissues of cashmere goats.The results showed as follows:the content of CHO in gluteal muscles,triceps brachii,mesenteric lipids,subcutaneous fat and omental lipids of goats in the TRS group were significantly lower than those of the CON and TMS groups(P<0.05).The content of CHO in the omentum of the gluteal muscle was significantly lower than that in the TMS group(P<0.05).Compared with the CON and TMS groups,the C18:ln9t,C18:3n3,C20:5n3,C22:6n3 content and P/S value in most body tissues of goats in the TRS group were increased significantly(P<0.05),C12:0,C14:0 and C16:0,C18:ln9t content decreased significantly(P<0.05).Compared with the CON group,the content of C10:0,C14:0 and C16:0 in most body tissues and the content of C22:6n3 in triceps of cashmere goats in the TMS group increased significantly(P<0.05);but C18:n3,C22:5n3 in gluteal muscles and most adipose tissuest decreased significantly(P<0.05).These results indicate that the roughage mixed rationof stall fattening and grazing supplementation feeding can increase the content of n-3 PUFA deposited in the cashmere goat meat and reduce the cholesterol content in the meat,moreover the total roughage ration showed better effect than grazing supplementation feed.The fifth experiment mainly compared the effects of three feeding modes on enzyme activities and gene expression related to fat deposition of cashmere goats.The results showed as follows:compared with the TMS and CON groups,the mRNA expression of PPARy,ACC,HSL,FAS,DGAT1,LPL and the enzyme activity of FAS,ACC,LPL,HSL in most body tissues of cashmere goats in the TRS group were lowered and the activity of ACC and SCD1 in serum was decreased;but the mRNA expression of HSL,LXR,PPARy,FADS2,FADS1,ACOX1,L-BPE,SCP2,PRkAA2,CPT1?ELOVL5,ELOVL2,SLC27A4 and Thiolase and the activity of HSL,ELOVL5,ELOVL2,SLC27A4 and Thiolase in most body tissues were higher(P<0.05)and the HSL activity in serum of cashmere goats in the TRS group is increased.Compared with the CON group,the mRNA expression of FAS,ACC,LPL,DGAT1,SCD1,PPARy,L-BPE,SCP2,ELOVL2 and SLC27A4 and the activity of SCD1,FAS,ACC and LPL in most body tissues of cashmere goats in TMS group were improved(P<0.05),but the mRNA expression of HSL,FADS1,FADS2,PRkAA2,ACOX1,CPT1?,LXR,PPARy,ELOVL5,SLC27A4,Thiolase and the activity of HSL,ELOVL2,ELOVL5 and SLC27A4 were decreased(P<0.05).These results indicate that the stall feeding with total roughage ration and grazing supplementary feeding can increase the n-3 PUFA content of body tissues in cashmere goat by up-regulating the enzyme activity and gene expression related to n-3 PUFA synthesis,but the promotion effect of the stall feeding with the total roughage ration is better than grazing Supplementary feeding.In conclution,total mixed ration can improve the fattening performance,slaughter performance and meat quality of the cashmere goats in stall fattening,which will increase the deposition of body fat of goats.However,it also increased SFA deposition in goat's tissue by high expression of genes related to SFA synthesis which is harmful to human's health.Although total roughage ration reduces the fattening performance,slaughteg performance and the fat deposition of the body tissues of the cashmere goats in stall fattening,it can improve the lean meat rate and the content of n-3 PUFA in body tissues of cashmere goats,which is beneficial to human health.