| In recent years,as consumers become more aware of public health and food safety,the market share of live broiler chickens in China is rapidly declining,and slaughtered and processed broiler products are gradually taking over the market.However,the overall slaughter rate and carcass aesthetics of yellow-feathered broilers are not high,which may reduce the production efficiency of enterprises and affect consumers’ choice in the context of "live to fresh".Therefore,selection and breeding of yellow-feathered broilers suitable for slaughter and processing is the focus of breeders at the moment.In this experiment,we analyzed and compared the growth performance,slaughter performance,carcass appearance and meat quality of different strains,sexes and days of age,with the aim of screening the strains,sexes and days of age of Xueshan chickens suitable for slaughter and processing,and providing breeding information for the selection of yellow-feathered broilers for slaughter and processing.The main results are as follows:1.Growth performance and serum biochemical indexes were measured.To investigate the growth performance,feather development and serum biochemical indexes of slow and medium speed Xueshan chickens.In this experiment,2700 healthy 1-day-old Xueshan chickens,including 900 slow type A,slow type B and medium type C(male and female halves),were housed in six separate coops according to strain and sex,with male chickens kept until 110 days of age and female chickens kept until 115 days of age under the same conditions,and growth performance was measured until 84 days of age.During the experiment,30 Xueshan chickens were randomly selected from each coop to determine growth performance and feather length(fortnightly from 28 days of age),and their serum biochemical parameters were measured at 28 days of age.The results showed that in terms of feather development,the length of the main wing feathers of the medium-speed Xueshan chickens was significantly greater than that of the slow-speed Xueshan chickens(P<0.05),and the time to change the main wing feathers of the medium-speed type was 56 and 84 days of age,and the tail feathers were 42 days of age,which were consistent with the slow-speed Xueshan chickens.In terms of growth performance,there were significant differences in strain and age(P<0.05),and the weight and body size indexes of the medium-speed type were significantly better than those of the slow-type chickens.For crown development,the crown length,height and thickness of medium-speed Xueshan cockerels were significantly higher than those of slow-speed type(P<0.05).For serum biochemical parameters,serum immunoglobulin A(Ig-A)concentration,total antioxidant capacity(T-AOC)and catalase(CAT)activity were significantly higher in medium-speed feamale Xueshan chicken than in slow chickens(P<0.05);serum superoxide dismutase(SOD)and CAT activity were higher in medium-speed female Xueshan chickens than in slow chickens(P<0.05).Serum corticosterone(CORT)levels were significantly lower in the medium-speed Xueshan hens than in the slow-speed A Xueshan hens(P<0.05).The growth performance,antioxidant capacity and stress resistance of medium-speed Xueshan chickens were better than those of slow-speed chickens,and the differences between slow-speed type A and slow-speed type B were not significant.2.Determination of slaughter performance,carcass appearance and meat quality related indexes.(1)Effect of strain and age on slaughter performance,carcass appearance and meat quality of Xueshan chickens:slaughter trials were conducted on medium and slow types at 90 d,100 d and 110 d for male chickens,respectively,with 30 birds of each strain and sex(the number of spotted skin ratio is 60 pieces).The results showed a significant effect of strain and age on slaughter index with an interaction effect(P<0.05)in terms of male slaughter performance.The weight indexes,including pre-slaughter weight,carcass weight,half-clean bore weight,full-clean bore weight,breast muscle weight and leg muscle weight,were significantly greater in the medium-speed type than in the slow type,but the slaughter rate and abdominal fat rate were significantly lower than in the slow type(P<0.05);the leg muscle rate and lean meat rate were significantly higher in the 110-day-old Xueshan chickens than in the 90-day-old and 100-day-old ones(P<0.05),but the half-clean bore rate and full-clean bore rate were not significantly(P>0.05).In terms of the appearance of male chicken carcass,the skin yellowness(b*)of the medium speed type Xueshan chicken is slightly lower than that of the slow speed type but not significantly(P>0.05).The skin brightness(L*)and redness(a*)of Xueshan chickens at 110 days old were significantly higher than those at 100 days old(P<0.05).The proportion of genuine carcass grade of Xueshan chickens aged 110 days is the highest,and the proportion of third grade carcass is the lowest.In terms of male chicken breast muscle quality,shear force,pH1(pH measured within 1 h)and flesh color L*were significantly higher in the medium-speed type of Xueshan chickens than in the slow type(P<0.05),and the highest shear force and protein content were found in Xueshan chickens at 110 days of age(P<0.05),and flesh color b*was not significantly different from 90 and 100 days of age(P>0.05).In terms of leg muscle quality of males,shear force was not significantly(P>0.05)different from slow type in medium speed Xueshan chickens,and flesh color L*and b*were significantly(P<0.05)lower than slow type,and shear force,protein content and flesh color b*were the highest(P<0.05)in Xueshan chickens at 110 days of age.(2)Effect of strain and age on slaughter performance,carcass appearance and meat quality of Xueshan chickens:slaughter trials were conducted on medium and slow types at 110 d and 115 d for female chickens,respectively,with 30 birds of each strain and sex(the number of spotted skin ratio is 60 pieces).As for the slaughter performance of the females,the results were similar to those of the males,with the weight indexes of the medium-speed type of Xueshan chickens being significantly greater than those of the slow-speed type,and the slaughter rate,half-clean bore rate and full-clean bore rate being significantly higher at 110 days of age than at 115 days of age(P<0.05).In terms of the appearance of the female chicken carcass,the skin a*of the medium speed Xueshan chicken is the lowest(P<0.05),and b*is higher than that of the slow speed type B but not significantly(P>0.05).There was no significant difference in skin b*between the 115 day old and 110 day old Xueshan chickens(P>0.05).The 115 day old medium speed Xueshan chicken has the highest grade of genuine carcass and the lowest proportion of third grade carcass.In terms of female breast muscle quality,the medium-speed type Xueshan chickens had the highest protein content,and the shear force,water loss,pH1,meat color L*and protein content of Xueshan chickens at 115 days of age were significantly higher than those at 110 days of age(P<0.05).In terms of female chicken leg muscle quality,fat content was significantly higher in the medium-speed type Xueshan chickens than in the slow type(P<0.05),while the differences in other indices were not significant.water loss rate,pH1,pH24(pH measured at 24 h),meat color a*and protein content were significantly lower at 110 days of age than at 115 days of age,but meat color L*,b*and fat content were significantly higher than at 115 days of age(P<0.05).The slaughter results of different strains and ages of Xueshan chickens showed that both males and females at 110 days of age were suitable for slaughter and processing,but due to gender differences in the consumption of quality chickens,the experiment further analyzed the gender dimorphism of the processing traits of Xueshan chickens at a common slaughter age of males and females(110 days of age)in order to further optimize production efficiency,with the following results:(3)Effect of different strains and sexes of 110-day-old Xueshan chickens on slaughter performance,carcass appearance and meat quality:Analysis of the effects of strain and sex on slaughter performance,carcass appearance and meat quality of 110-day-old Xueshan chickens as an example.There were significant differences between strains and sexes in slaughter performance(P<0.05),with slaughter weight indexes such as pre-slaughter weight,carcass weight,and full clean bore weight significantly higher in medium speed type C than in slow speed type,and slaughter rate,half clean bore rate,and leg muscle rate lower than in slow speed type(P<0.05).All slaughter weight indexes,full net gutting rate,leg muscle rate and lean meat rate were significantly higher in males than in females(P<0.05).In terms of carcass appearance,strain and sex had a significant effect on skin color brightness(L*),redness(a*)and yellowness(b*)with an interaction(P<0.05).Skin L*was higher in the medium-speed type,and males had higher skin L*,a*and b*than females(P<0.05).The carcass positive grade of the medium-speed type of Xueshan chickens was closer to that of the slow-speed type,and the proportion of positive carcasses was more in the males than in the females.In terms of breast muscle quality,there was no significant difference between medium and slow speed type Xueshan chickens(P>0.05),and the shear force,pH1,pH24 and moisture content were significantly higher in males than in females(P<0.05).In terms of leg muscle quality,pH1 was significantly higher in the medium-speed type Xueshan chickens than in the slow type,and the shear force,meat color a*,moisture and collagen content were significantly higher in the males than in the females,while meat color L*,b*and fat content were significantly lower than in the females(P<0.05).In addition,the slaughter performance,carcass appearance and meat quality results were similar for slow type A and slow type B.In summary,medium-speed type has better slaughter performance and carcass appearance than slow-speed type Xueshan chickens;males have better slaughter performance and carcass appearance than females and higher muscle protein content;110-day-old males have better slaughter performance,carcass appearance and muscle protein content than 90-day-old and 100-day-old ones;110-day-old females have similar muscle nutrients compared with 115-day-old ones.Therefore,medium-speed Xueshan chickens are more suitable for slaughter and processing yellow-feathered broiler products,it is also recommended to increase the proportion of male chickens,and it is recommended to extend the slaughter days to 110 days for slow type Xueshan chickens.This paper argues that screening medium-speed broilers and appropriately adjusting the slaughter age and sex ratio will help improve the market competitiveness of slaughter and processing yellow-feathered broilers. |
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