This experiment was conducted to investigate the protein metabolism rule and requirement of 500 to 550 kg Simmental hybrid beef cattle.Thirty healthy Simmental hybrid bulls with similar weight of(497.73±43.84)kg were randomly divided into 5 groups with 6 replicates per group and 1 cow per replicate.The pre-feeding period was 10 days,and the formal experiment period was 45 days.The comprehensive net energy of all diets was 6.12 MJ/kg.The crude protein(CP)levels of the diets were 9.53％,10.53％,11.53％,12.53％and 13.53％,respectively.The effects of different dietary CP levels on growth performance and pro-tein metabolism of Simmental hybrid cattle were studied through feeding experiment and digestion and metabo-lism experiment.A prediction model of protein requirement of 500 to 550 kg Simmental hybrid cattle was es-tablished.The results showed as follows:1)with the increase of dietary CP level,the average daily gain(ADG)of beef cattle in all groups was firstly increased and then decreased,and the ADG in 12.53％group was the highest,which was significantly higher than that in 9.53％and 13.53％groups(P＜0.05),and the feed/gain(F/G)in 12.53％group was the lowest,which was significantly lower than that in 13.53％group(P＜0.05).2)Different dietary CP levels had no significant effects on CP digestibility of 500 to 550 kg Sim-mental hybrid cattle(P＞0.05).Fecal nitrogen excretion of beef cattle in 10.53％group were the highest,which was significantly higher than that in 9.53％and 12.53％groups(P＜0.05),and CP deposition rate of beef cattle in 12.53％group was the highest,which was significantly higher than that in other groups(P＜0.05).3)The CP requirement equation of 500 to 550 kg Simmental cross cattle was CP=7.89W0.75+68.60ADG,the maintenance CP(CPm)requirement was 7.89 g/(kg W0.75·d),and the CP per kilogram of weight gain(CPg)requirement was 68.60 g.The digestible CP(DCP)requirement equation is DCP=6.68W0.75+61.19ADG,the maintain digestible CP(DCPm)requirement is 6.68 g/(kgW0.75·d),and the di-gestible CP per kilogram of weight gain(DCPg)requirement is 61.19 g.Under the conditions of this experi-ment,the optimal dietary CP level for 500 to 550 kg Simmental hybrid bulls is 12.53％,and the results of this study can provide data reference for protein requirements of 500 to 550 kg Simmental hybrid bulls.[Chinese Journal of Animal Nutrition,2024,36(8):5085-5093]
维普
万方数据