Effects Of Protein Level On Production Performance And Digestion And Metabolism In Feed-lot Liaoning Cashmere Goat

In order to investigate the feeding standardization of protein,by the means of one-factor experiment,healthy 2-year-old female cashmere goats with close body weight,which was provided by Breeding Goats Field of Liaodong College,were arranged under feed-lot to study the effect of different protein level diets on performance and digestion and metabolism.In test one,30 2-year-old female Liaoning cashmere goats were arranged into 5 groups(groupâ… ,groupâ…¡,groupâ…¢,groupâ…£,groupâ…¤).There were 6 animals in each group. With the reference of American goat feeding standard,effects of different dietary protein levels (9.26%,10.06%,11.02%,12.12%,13.19%) on production performance and nutrient digestibility were studied.The results showed that different dietary protein levels had no significant effect on live body weight gain,cashmere yield,cashmere growth rate,cashmere length,cashmere diameter and cashmere thickness(P＞0.05) respectively.There were no significant difference among testing groups on DM intake,crude fiber intake,energy intake,apparent digestibility of crude fiber(P＞0.05).Crude protein intake of groupâ…¤was 89.69 g/d,and significantly higher than groupâ… (62.97 g/d),groupâ…¡(68.41 g/d),groupâ…¢(74.94 g/d) and groupâ…£(82.42 g/d)(P＜0.05).Crude protein apparent digestibility of groupâ…¤was significantly higher than those of the other four groups(P＜0.05).There was no significant difference of energy digestibility among groupâ… ,groupâ…¡and groupâ…¢(P＞0.05).But,they were significantly higher than those of groupâ…£and groupâ…¤(P＜0.05).A significant positive correlation(P＜0.01) was found between dietary protein level and crude protein apparent digestibility,and the correlation coefficient was 0.818,and the recursive formula was y=-1.379x+79.022-0.677. There was a significant(P＜0.01) negative correlation between dietary protein level and energy apparent digestibility,and the correlation coefficient was-0.677,and the recursive formula was y=5.316x+41.265.There was no significant correlation(P＞0.05) between dietary protein level and crude fiber apparent digestibility.Energy apparent digestibility obviously declined when the dietary protein level was above 11.02%.In test two,15 Liaoning cashmere goats were randomly divided into 3 groups in averagely to study the effects of different protein level(9.26%,10.06%,11.02%) on nitrogen balance,CF digestion,energy digestion and metabolism.The results showed that N intake,Urinary N, digestible N,retained N and apparent digestibility were significantly(p＜0.01) correlated to dietary protein level.There was significantly negative correlation between protein level and fecal N(P＜0.05);N intake and retained N were 11.24g/d and 4.94g/d respectively in groupâ…¢, which were significantly higher than those of the other two groups(P＜0.05);There was no difference on CF digestibility among three groups(P＞0.05).There was no significant difference (p＞0.05) of GE intake,FE output,UE output,CHaE output,DE and ME among three tested groups.DE and ME were significantly correlated(P＜0.01) positively,and its linear regression formula was y=0.775+0.985x(r²=0.986,n=15,P＜0.01).CH₄E and FE were significantly correlation(P＜0.05) positively,and its linear regression formula was y=-0.80+0.864x (r²=0.522,n=15,P＜0.01).It was suggested that the dietary protein level was 11.02%for growing Liaoning cashmere goat.