Effects Of Full-Price Granule With Different Protein Levels On Growth Performance,Serum Biochemical Indexes And Rumen Fermentation Of Male Calves

The effects of different protein levels on growth performance,serum biochemical parameters and rumen fermentation of male calves were studied.15 holstein calves of similar age and physiological status were randomly divided into 3 groups with 5 calves in each group.The crude protein levels were 15.05%,18.09%and 21.02%,respectively.The pre-test period was 7 days,and the trial period was 56 days.Calf weight,body height,body length and chest circumference were measured at the beginning and end of the trial period,and calf average daily weight gain was calculated.Blood was collected through the jugular vein 3 hours after morning feeding on day 1,28 and 56 of the trial period.Calf digestion test was conducted on the last 3 days of the trial period.At the 56th day of the trial period,tumor gastric juice was collected 2?3 h after morning feeding to determine rumen fermentation indexes.The results show that:1.Effects of different protein levels on growth performance and apparent digestibility of various nutrients in male calves.The results showed that:(1)the diets with different protein levels had no significant effect on calf intake,net weight gain and average daily weight gain(P>0.05),among which the intake of calves in the high-protein group was the highest,and the net weight gain and average daily weight gain increased with the increase of protein levels.In addition,different protein levels had no significant effect on body height,body oblique length,chest circumference and tube circumference of each treatment group(P>0.05).(2)neutral washing fiber,acid washing fiber,crude protein and crude fat were not affected by dietary protein levels,and there was no significant difference between the groups(P>0.05).The high protein group had the highest apparent digestibility.2.Effects of different protein levels on serum biochemical indexes of male calf.The results showed that:(1)adding diet with different protein levels had no significant effect on AST,GGT and LDH(P>0.05).The ALT concentration in the diet with high protein levels(21.02%)was significantly higher than that in the low-protein group(15.05%)and the medium-protein group(18.09%),and the ALP concentration in the high-protein group(21.02%)was significantly higher than that in the medium-protein group(18.09%)(P<0.05).(2)diets with different protein levels had no significant effect on serum TP,ALB,GLO,A/G,UA,and GLU in calves(P>0.05).CREA was significantly higher in the low-protein group(15.08%)than in the high-protein group(21.02%)(P<0.05).BUN in the high-protein group(21.02%)was significantly higher than that in the low-protein group(15.08%)(P<0.05).(3)diets with different protein levels had no significant effect on growth hormone and insulin-like growth factor-I in calf serum(P>0.05)3.Effects of full-price granule with different protein levels on rumen fermentation in male calves.The results showed that:(1)dietary supplementation with different protein levels had no significant effect on the pH value,isobutyric acid and iso-valeric acid of tumor gastric juice at the 56th day(P>0.05).The total volatile fatty acid,acetic acid,propionic acid,butyric acid and valeric acid in the high-protein group were significantly higher than those in the low-protein group and the medium-protein group(P<0.05).(2)dietary protein level had no significant effect on species diversity index Simpson,Shannon,species richness index Chao 1 and ACE(P>0.05).(3)at the phylum level,the dominant bacteria in the rumen of the low-protein group and the high-protein group were Firmicutes,Bacteroidetes and Tenericutes.Bacteroidetes in the low-protein group were significantly higher than those in the high-protein group(P<0.05).The high-protein group Tenericutes,Oxyphotobacteria and Chloroflexi were significantly higher than the low-protein group(P<0.05).There was no significant difference between the two groups of other bacteria(P>0.05).At the genus level,Ruminococcaceae,Lachnospiraceae and Prevotellaceae were the dominant bacteria in the rumen of the low-protein and high-protein groups.Syntrophococcus in the high protein group was significantly higher than that in the low protein group(P<0.05).Clostridiales in the high-protein group had a higher trend than that in the low-protein group,but the difference was not significant(P=0.070).The low-protein group had a significantly higher trend than the high-protein group(P=0.056;P=0.076);There was no significant difference between the remaining groups(P>0.05).To sum up,this study conducted a systematic study on the appropriate crude protein level of 5-month-old male calf diet through animal growth test and digestion and metabolism test,and determined that the crude protein level of 5-month-old male calf diet was 21.02%,which was beneficial to the growth and development of the calf.