Research On The Nutritional Regulation Effects Of Amino Acid And Minerals In Feedlot Yaks

Yak,as a unique cattle species,is the livelihood of Tibetan people in Qinghai-Tibet Plateau.Scientific feeding management is an important means to solve the problem of low production performance in yak traditional production.Moreover,with the optimization of grassland management in the plateau area,the feeding and management of yaks are different,and new management methods need new nutritional theories and methods.However,due to the unique habitat of yak,the research on its nutritional regulation is obviously lagging behind compared with similar species in low altitude areas.Therefore,in this study,the effects of amino acid and mineral nutrition regulation on fattening performance of feedlot yaks were systematically studied by feeding test and slaughter trials using the principle of systematic nutrition in order to explore the strategies of amino acid and mineral nutrition regulation.Thirty-two healthy male yaks with similar physical conditions during growth period w ere selected and divided into4 groups and 8 yak in each group,named control group(CON,not supplemented with RPLys and RPMet),low-level group(group L,supplemented with RPLys 30 g/yak/d +RPMet 7.5 g/yak/d);middle-level group(group M,supplemented with RPLys50g/yak/d + RPMet 12.5g/yak/d);high-level group(group H,supplemented with RPLys 70 g/yak/d + RPMet 17.5 g/yak/d)in nutritional regulation of amino acids;Sixteen healthy male yaks with similar physical conditions during the growth period were selected and divided into two groups,named control group(group C)and treatment group(group T),each group contained eight yaks.Two group were fed the same basal diet,and group T was fed the sustained-release mineral bolus at the beginning of the trial,while group C was not fed in nutritional regulation of minerals;According to the actual production mode of Naqu yak in Tibet,the based feeding was used to yak house feeding and fattening,i.e.,all yaks were fed the same basic diet,and the period consisted of a 7 days pre-test and 90 days fattening and sampling.The main research results showed as follows:1.There was no significant difference in the initial and final body weight of yak at different rumen amino acids levels(P > 0.05).Supplemented rumen amino acids had no effect on dry matter intake(DMI)(P > 0.05).In the M group,the average daily gain(ADG)was significantly increased and the feed-weight ratio(F/G)was decreased(P <0.05).With the increase of rumen amino acid level,the concentrations of butyric acid and isobutyric acid in rumen fluid showed a quadratic or linear trend(P < 0.10).The isovaleric acid concentration was significantly increased and the acetic acid / propionic acid ratio was decreased in group H(P < 0.05).Other rumen fermentation indexes had no significant effect(P > 0.05).2.There was no significant difference in slaughter performance of yaks at different rumen amino acids levels(P > 0.05).There was no significant difference in p H between longissimus dorsi and biceps femoris(P > 0.05).The longissimus dorsi muscle color L*,a * and b * values were significantly affected(P < 0.05);There was no significant effect on biceps femoris muscle color(P > 0.05).The drip loss and shear force of the longissimus dorsi muscle were significantly different(P < 0.05),and the shear force of the biceps femoris muscle was significantly different(P < 0.05).There was no significant difference in psoas muscle cooked rate among groups(P > 0.05).The density of longissimus dorsi muscle fiber was significantly different(P < 0.05),and the diameter and density of biceps femoris muscle fiber were significantly different(P <0.05).Under different rumen-crossing amino acid levels,the CP content in the longissimus dorsi muscle was significantly increased in the M group(P < 0.05),and there was no significant difference in other conventional nutritional indexes of yak meat(P > 0.05).The contents of total amino acids(TAA),essential amino acids(EAA)and non-essential amino acids(NEAA)in longissimus dorsi and biceps femoris had no difference(P > 0.05).Gly content in longissimus dorsi muscle was significantly affected(P < 0.05).The contents of serine(Ser)and proline(Pro)in longissimus dorsi muscle showed linear and quadratic trends with the increase of amino acid addition levels(P < 0.10).3.ADG and DMI in group T were significantly higher than those in group C(P <0.05),and F/G was significantly lower than that in group C(P < 0.05).The concentration of valerate in group T was lower than that in group C(P = 0.077),and there was no significant difference in other rumen fermentation indexes(P > 0.05).4.The pre-mortem live weight,carcass weight and slaughter rate of group T were7.50 %,12.93 % and 5.14 % higher than those of group C,respectively(P > 0.05),and the eye muscle area showed an increasing trend(P = 0.056).The muscle p H in group T had no significant effect compared with that in group C(P > 0.05).The L * and b *values of muscle in group T were significantly lower than those in group C(P < 0.05).The a * value of longissimus dorsi in group T was significantly higher than that in group C(P < 0.05),and the a * value of biceps femoris showed an increasing trend(P = 0.091).The drip loss of longissimus dorsi in group T was significantly lower than that in group C(P < 0.05),and the drip loss of biceps femoris was 4.52 % lower than that in group C(P > 0.05).The shear force of longissimus dorsi in group T was 6.90 % lower than that in group C(P > 0.05),and that of biceps femoris was 30.99 % lower than that in group C(P > 0.05).There was no significant difference in fiber density and area of longissimus dorsi and biceps femoris between group T and group C(P > 0.05).There was no significant difference in fiber diameter of longissimus dorsi between-group T and group C(P > 0.05).There was a decreasing trend in fiber diameter of biceps femoris between-group T and group C(P = 0.077).There was no significant difference in the conventional nutritional indexes in the longissimus dorsi and biceps femoris between the T group and the C group(P > 0.05).The contents of Ca,Mg,Cu,Mn,Zn and P in the longissimus dorsi and biceps femoris of T group and C group were not significantly different(P > 0.05).The Fe content in the longissimus dorsi of the T group was higher than that of the C group(P = 0.077).There was no significant difference in total amino acid content between-group T and group C(P > 0.05).Longissimus dorsi serine(Ser)in group T was higher than that in group C(P = 0.059),and biceps femoris threonine(Thr)in group T was higher than that in group C(P = 0.058).In conclusion,under the effect of amino acid nutrition regulation,supplemental rumen amino acids improved the growth performance of yak,and had no significant effect on its slaughter performance.At the same time,meat quality indexes such as meat color,drip loss and shear force of yak meat were improved.Under the conditions of this experiment,the optimal supplemental recommended amount was 50 g/yak /d of RPLys+ 12.5 g/yak/d of RPMet.Under the regulation of mineral nutrition,the supplement of mineral sustained-release pellets improves the growth performance of yaks,and improves the slaughter performance of yaks to a certain extent.It has the potential to improve the meat quality of yaks and improve the breeding efficiency.