The Study On Energy And Protein Requirement Of Qinchuan Cattle

This article researched digestive energy, metabolism energy, crude protein and intestinal digestible crude protein requirement of Qinchuan cattle through two experiments. Firstly, different energy gradient and small intestine digestible protein gradient diets were designed and then these requirement models were determined between digestive energy, energy metabolism, crude proteinand and intestinal digestible crude protein requirement and average daily gain with factorial method through the digestion and metabolism trials.In experiment 1, Feeding test and digestion and metabolism test were carried out to measure the digestive energy requirement and energy metabolism requirement of growing Qinchuan cattle. Thirty healthy growing Qinchuan cattle with asimilarbody weight of 336.33±18.28 kg wereselected and randomly divided into 5 groups with 6 replicates in each group. Beef cattle were fed 5 diets with different levels of energy diets which were formulated according to the expected weight gain 0.8kg/d of energy [China Feeding Stantard of Beef Cattle (NY/T815-2004)] required for 85%(group I),92.5%(group II),100%(group III),107.5%(group IV),115%(group V), respectively. Measure the growth performance and energy metabolism indexes of growing Qinchuan cattle, and to build the models for predicting the digestive energy requirement and energy metabolism requirement. Pre-test period was 10 d and test period was 42 d.The results showed as follows:1.The average daily gain of group III (880.95 g/d) was similar to the expected result; the average daily gain (1160 g/d),and gross energy digestibility, gross metabolic rate and gross energy digestible energy were (76.44±3.23)%, (66.75±3.16)% and (87.31±0.54)%, respectively.2.The digestive energy requirement (DER, MJ/d)and metabolizable energy requirement(MER, MJ/d) of growing Qinchuan cattle could be estimated by the equations:DER= 0.778W075+37.05*ADG (R2=0.928,P<0.05); MER(MJ/d)=0.668W0.75+33.49*ADG(R2=0.925,P<0.05), the digestive energy requirement (DEm) and metabolizable energy requirement (MEm) for maintenance of growing Qinchuan cattle are 0.778 and 0.668 MJ/(kg W0.75-d), respectively. Digestible enengy (DEg) and metabolizable energy (MEg) needed per kilogram body weight gain are 37.05 and 33.49MJ, respectively.In experiment 2, the protein deposition efficiency and intestinal digestible crude protein (IDCP) requirement of growing Qinchuan cattle were investigated by feeding experiment and digestive and metabolic experiments. The results showed that there was a positive linear correlation between average daily gain and crude protein intake and IDCP intake (R2=0.928, P<0.05; R2=0.912, P<0.05).Feed conversion rate in groups Ⅳand Ⅴ were significantly greater than that in groups Ⅰ,Ⅱ and Ⅲ(P<0.05). There was a significant difference in aspects of nitrogen intake and nitrogen retention among five groups (P<0.05).Fecal nitrogen, urine nitrogen and protein deposition efficiency were gradully increased as the increase of IDCP level. There was no significant difference between Ⅳ and Ⅴ groups in aspect of apparent nitrogen digestibility (P>0.05), but significantly higher than other groups (P<0.05). he crude protein and IDCP requirements for growing Qinchuan cattle coule be estimated by the equations:CP (g/d)= 5.94w0.75 (kg)+470.84*ADG (kg/d) (R2=0.937, P<0.05); IDCP (g/d)=3.71w0.75 (kg)+285.22*ADG (kg/d) (R2=0.942, P<0.05).The crude protein and IDCP requirements for maintenance of growing Qinchuan cattle were 5.94 and 3.71 g/(kgW0.75·d), respecitively. The crude protein and IDCP requirements for per kilogram body weight gain of growing Qinchuan cattle were 470.84 and 285.22 g, respectively.In summary, the DEm and MEm of growing Qinchuan cattle are 0.778 and 0.668 MJ/(kg W0.75·d), respectively. The DEg and Meg per kilogram body weight gain are 37.05 and 33.49MJ, respectively. The crude protein and IDCP requirements for maintenance of Qinchuan cattle were 5.94 and 3.71 g/(kg W0.75·d), respecitively. And the crude protein and IDCP requirements for per kilogram body weight gain of Qinchuan cattle were 470.84 and 285.22 g, respectively.