Effects Of Age And Sex On Fattening And Meat Quality Of House-feeding Yaks

In order to find out the best fattening age of house-feeding yak and form a set of high quality yak meat production technology,the objectives of the present study were to investigate the effects of age and sex on fattening and meat quality of house-feeding yaks.It provided the data basis for the production of high quality yak meat and the evaluation of yak meat grades and standards,so as to provide a theoretical basis for promoting the industrialization of yaks in China.Experiment 1: Effects of age on fattening and meat quality of house-feeding yaksThe healthy Maiwa male yaks(n=18)were allocated to three groups(1.5-year-old =‘AGE1.5',2.5-year-old=‘AGE2.5' and 4.5-year-old =‘AGE4.5')by ages.In the AGE1.5 group(average body weight 140.30±5.88 kg),AGE2.5 group(average body weight 150.20±7.79 kg)and AGE4.5 group(average body weight 233.3±28.73 kg),each group with 6 replicates and 1 yak in each replicate.All yaks were reared and finished under identical management conditions for 180 days by house-feeding,and 6 yaks in each group were selected for slaughter.(1)The results of age on the growth performance,nutrient apparent digestibility and slaughter performance of house-feeding yaks were as follows.The dry matter intake(DMI)and feed to gain ration(F/G)of the AGE4.5 group was significantly higher than that of the AGE1.5 and AGE2.5 groups(P<0.05),and there was no significant differences in average daily gain(ADG)between different ages(P>0.10).The apparent digestibility of gross energy(GE),crude protein(CP),neutral detergent fiber(NDF),acid detergent fiber(ADL)and organic matter(OM)nutrients in the AGE4.5 group was significantly lower than that of the AGE1.5 and AGE2.5 groups(P<0.05).The pre-slaughter weight,net meat weight and eye muscle area of the AGE4.5 group was significantly higher than that of the AGE1.5 and AGE2.5 groups(P<0.05),and there was no significant difference in other slaughter performance(P>0.10).The above indicators,there was no significant difference between the AGE1.5 and AGE2.5 groups(P>0.10).(2)The results of age on the nutritional quality of yak meat were as follows.The fattening age had a significant effect on the CP,EE and crude ash(Ash)of yak meat(P<0.05),and had no significant effect on moisture(P>0.10).The content of CP in yak meat of AGE4.5 group was the highest,the content of EE in yak meat of AGE1.5 group was the highest,and the content of Ash in yak meat of AGE2.5 group was the highest.The fattening age had a strong influence on the amino acid composition in house-feeding yak meat.The proportion of essential amino acids in total amino acids(EAA/TAA)and essential amino acids in non-essential amino acids(EAA/NEAA)in the following order: AGE2.5> AGE4.5> AGE1.5.The ratio of flavor amino acids to total amino acids(FAA/TAA)in the AGE2.5 group was significantly lower than that in the AGE1.5 and AGE4.5 groups(P<0.05).The effect of age on the fatty acid of yak meat was relatively small.The content of C21:0 in the AGE2.5 group was significantly higher than that of the AGE1.5 and AGE4.5 groups(P<0.05),while the other fatty acid contents and proportions were not significantly different(P>0.10).The C22:0 and C20:2 were only detected in the AGE1.5 group,and the AGE2.5 and AGE4.5 groups were not detected.(3)The results of age on the eating quality of yak meat were as follows.There were significant differences among ages in color and myoglobin status of yak meat(P<0.05).The luminance(L*),redness(a*),oxygenated myoglobin content of yak meat in the AGE1.5 and AGE2.5 groups were significantly higher than the AGE4.5 group(P<0.05).Their hue angle(h)and myofibrobbrin content were significantly lower than the AGE4.5 group(P<0.05),and their chroma(c)had a tendency to be higher than the AGE4.5 group(P<0.10).The influence of age on drip loss was not significant(P>0.10),which had a significant effect on cooking loss(P<0.05),among which the AGE4.5 group had the highest cooking loss.As the age of yaks increased,the shear force,muscle fiber diameter,muscle fiber area and total collage of yak meat significantly increased(P<0.05),but the muscle fiber density and collagen solubility significantly decreased(P<0.05).In the antioxidant index of yak meat,malondialdehyde(MDA)content increased significantly with age(P<0.05).However,the content of catalase(CAT),total superoxide dismutase(T-SOD),total antioxidant capacity(T-AOC)and glutathione peroxidase(GSH-PX)in three groups of yak meat were not significant(P>0.10).Experiment 2: Effects of sex on fattening and meat quality of house-feeding yaksTwelve healthy Maiwa yaks(half of male and female)were allocated to male yak group(average body weight 150.20±7.79 kg)and female yak group(average body weight 150.40±11.51 kg)according to their sex,each group with 6 replicates and 1 yak in each replicate.All yaks were reared and finished under identical management conditions for 180 days by house-feeding,and 6 yaks in each group were selected for slaughter.(1)The results of sex on the growth performance,nutrient apparent digestibility and slaughter performance of house-feeding yaks were as follows.The ADG of the male yak group was significantly higher than female yak group(P<0.05),and the F/G had a low tendency than the female yak group(P<0.10).Sex had no significant effect on DMI of house-feeding yaks(P>0.10).The apparent digestibility of OM in the female yak group was significantly higher than that in the male yak group(P<0.05),but the apparent digestibility of other nutrient was not significant(P>0.10).Pre-slaughter live weight,carcass weight,net meat ratio and slaughter rate were influenced by sex,with a lower pre-slaughter live weight and carcass weight and a higher net meat ratio and the slaughter rate in the female yak group.Other indicators were not significantly different(P>0.10).(2)The results of sex on the nutritional quality of yak meat were as follows.Sex had significant influence on CP,EE and Ash in the yak meat(P<0.05),which was not significant difference in moisture(P>0.10).Compare with the male yak group,there were higher CP and EE and lower Ash content in the yak meat of the female yak group.Amino acid composition was different from yak meat of different sex.The cysteine(Cys)content of the female yak group was significantly higher than that of the male yak group(P<0.05);there was a trend of serine(Ser)and glutamic(Glu)content in yak beef of the female yak group was higher than that of the male yak group(P<0.10);the female yak group leucine(Leu),phenylalanine(Phe),histidine(His),EAA/TAA and EAA/NEAA were significantly lower than the male yak group(P<0.05);other amino acid indicators were not significantly different(P>0.10).C22:0,C20:2 and C18:3n6 were only detected in yak meat of the female yak group.C17:1 in the female yak group was significantly higher than that in the male yak group(P<0.05),and there were no significant differences in other fatty acid indexes(P>0.10).(3)The results of sex on the eating quality of yak meat were as follows.The influence of sex on the physiochemical index of yak meat was relatively small.There was a tendency of yak meat L* in male yak group higher than that of female yak group(P<0.10);in the male yak group,the drip loss of yak meat had a tendency to be lower than the female yak group(P<0.10);the cooking loss of yak meat in the male yak group was significant lower than that of female yak group(P<0.05);there were no significant differences in other fatty acid indexes physiochemical index(P>0.10).Sex had a significant effect on yak meat shear force,total collagen content,collagen thermal solubility,soluble collagen(P<0.05),and had no significant effect on muscle fibers(P>0.10).Compared to the female yak group,yak meat had higher shear force,total collagen,collagen thermal solubility and soluble collagen content in the male yak group.In addition,there was no significant difference in the content of antioxidant indexes in yak meat of different sex(P>0.10).In conclusion,the AGE1.5 group had lower production performance but the best meat quality.There were the highest production performance and better meat quality in the AGE2.5 group.The meat quality of the AGE4.5 group was the worst,and the higher F/G resulted in lower economic benefit.Therefore,the 2.5-year-old yak can be used as the main source for house-feeding and the potential for producing high-quality yak meat is in 1.5-year-old house-feeding yak.In addition,the female yak meat has super characteristics in eating quality and better healthy composition of nutrients than male yak,which means that the 2.5-year-old female yak has the potential to be used to produce high quality yak meat.