Effect Of Dietary Methionine On Growth,Breast Muscle Development And Meat Quaility Of Greenleg Partridge Chicken

There are extensive studies on the effect of methionine in fast-growing-broilers diets,but litter attention has been paid to the slow-growing broilers.Therefore,the objective of this study was conducted to evaluate the effect of methionine on growth,breast muscledevelopment and meat quality of greenleg partridge chicken(GPC)and AA broiler as reference to provide a theoretical reference for the application of methionine in greenleg partridge chicken.The study included 3 parts as follows:Trial 1 was conducted to evaluate the effect of dietary methionine on growth performance,organ development and serum physiological and biochemical parameters of greenleg partridge chicken.A total of 180 1-day-old greenleg partridge chicken(GPC)and 180 1-day-old Arbor Acres(AA)chickens were allocated to a 2×3 factorial arrangement of 6 groups with 6 replicates of 10 chickens.The diets were formulated to referenced NRC(1994),NY/T 33-2004 and the recommendation of greenleg partridge chicken in Guangdong Wens Poultry Jiangsu Branch,contained low(LM,0.35 and 0.31%Met during starter and finisher period),adequate(AM,0.50 and 0.44%Met)and high(HM,0.65 and 0.57%Met)Met,respectively.The LM diets contained no supplemental DL-Met,and the AM and HM diets were formulated by supplementing DL-Met in the LM diets.The results showed that:(1)The GPC broilers had lower growth performance than the AA broilers(P<0.05);The AA broilers fed the LM diets had lower(P<0.05)ADG and finisher BW than those fed the HM diets and higher(P<0.05)finisher F/G in the GPC broilers than those fed the HM diets.(2)The GPC broilers had higher thymus index,bursa index both at 21 d and 42 d,and higher intestine index at 42 d than the AA broilers(P<0.05);The AA broilers fed the HM diets had increased bursa index,liver index at 21 d compared with the AM diets,and compared with the AA broilers fed the LM diets,those fed the HM diets had improved thymus index at 42d(P<0.05).(3)The GPC broilers had higher UN,GLU,TC at 21 d but lower UN,TC,TG at 42 d in serum than the AA broilers(P<0.05);The AA broilers fed the HM diets had higher TP,ALB,GLU in serum at 21 d compared with those fed the LM diets(P<0.05).Trial 2 was conducted to study the effects of dietary methionie on slaughter performance,meat quality and antioxidant capacity of breast muscle of greenleg partridge chicken,experiment design was similar to trial 1.The results indicated that:(1)The GPC broilers had lower carcass yield,eviscerated yield,and breast muscle yield than the AA broilers(P<0.05);The AA broilers fed the LM diets had lower eviscerated yield and breast muscle yield than those fed the AM and HM diets(P<0.05),but no differences were observed in the GPC broilers.(2)The GPC broilers had higher drip loss but lower cooking loss,pH45m;n of breast muscle than the AA broilers(P<0.05).The AA broilers fed the LM diets had lower pH than those fed AM and HM diets(P<0.05),and the opposite change was observed for L*in both AA and GPC broilers.(3)There were no significant differences in moisture,crude ash or crude protein content of breast muscle between GPC and AAbroilers(P>0.05).The AA broilers fed the LM diets had higher(P<0.05)ether extract content in breast muscle than those fed the AM and HM diets,whereas no differences were observed in the GPC broilers.(4)The GPC broilers had higher MDA,GSH content but lower GPx activity in breast muscle than the AA broilers(P<0.05);The GPC broilers fed the LM diets had higher(P<0.05)MDA content but lower GPX activity in breast muscle those fed the HM diets(P<0.05);The LM diets resulted in lower T-SOD activity in breast muscle than the HM diets in both GPC broilers and AA broilers(P<0.05).The T-AOC of breast muscle was linearly increased with Met levels in the AA broilers(P<0.05).Trial 3 was conducted to study the effects of dietary methionine on IGF-? content in breast muscle and the expression of the key genes associated with the development of breast muscle of greenleg partridge chicken,experiment design was similar to trial 1.The results demonstrated that:(?)The IGF-? content of breast muscle was linearly increased with Met levels in the AA broilers of 42 d(P<0.05),and the GPC broilers fed the LM diets had lower IGF-? content of breast muscle than those fed the HM diets(P<0.05).(2)The GPC broilers had lower 4EBP1,MRF4,Myf5 mRNA expression in breast muscle than the AA broilers(P<0.05);The GPC broilers fed the HM diets had higher IGF-?,TOR but lower MSTN mRNA expression in breast muscle than those fed the LM diets(P<0.05),and the AA broilers had higher IGF-?,TOR MRF4,Myf5 mRNA expression in breast muscle(P<0.05).These results implied that:the GPC broilers had poorer growth performance and slaughter performance to the AA broilers.The growth performance,slaughter performance and meat quality of GPC broilers wrer less responsive to dietary Met status than those of AA broilers.Compared with LM diets,HM diets decreased finisher F/G.improved antioxidant capacity of breast muscle,promoted the secretion of IGF-? in breast muscle,and regulated the expression of several genes associated with muscle development in the GPC broilers.