Effects Of Dietary Supplementation With N-carbamylglutamate On Nitrogen Metabolism And Methane Emission Of Holstein Bulls

This experiment was conducted to investigate the effects of dietary supplementation of NCG in different levels on nitrogen metabolism of Holstein bulls.Forty-five healthy Holstein bulls(initial body weight=478± 13.66 kg,12 to 13 Months)were randomly assigned into three treatments with 15 replicates in each treatments,the bulls were supplemented with 0(control),15 or 25 g/d of NCG,respectively.The experimental period was 120 d including 7 d for adaptation and 90 d for sampling and data collection.The results showed as follows:(1)The feed-weight ratio(F/G)was reduced by 6.91%(P<0.05)and 7.91%(P<0.01)in bulls fed 15,25 g/d NCG,respectively,compared with control;(2)The plasma concentration of Arginine increased by 14.05%(P<0.01)and 8.30%(P<0.01)in bulls supplemented with 15,25 g/d NCG,respectively,than control;(3)The concentration of serum TP,no and GLU in bulls increased(P=0.01)supplemented with 15 g/d and 25 g/d,compared with control group;The concentration of serum urea nitrogen in bulls decreased(P=0.01)supplemented with 15 g/d and 25 g/d,compared with control group;The concentration of T-AOC and GSH-PX significantly(P<0.05)increased in bulls fed 15 g/d NCG;The level of IFN-y and IL-2 significantly(P<0.01)increased in bulls fed 15 g/d NCG;(4)Supplemented of NCG had no significant effect on the amount of allantoin,uric acid and purine derivatives excreted in urine(P>0.05);(5)The bulls supplemented with 15 g/d NCG increased nitrogen retention(P=0.01),nitrogen protein utilization and protein biological value than control(P<0.05).(6)Dietary supplemented with different levels of NCG all decreased the methane emission of Holstein bulls,the methane emission were decreased by 8.44%and 10.51%in bulls fed 15,25 g/d NCG,respectively(P<0.01)compared with control;(7)The microbial protein concentration increased by 22.91%(P<0.05)and 15.17%(P<0.01)in bulls fed 15,25 g/d NCG,respectively;The concentrations of propionic acid in rumen increased linearly(P=0.01)with increasing NCG supplementation,with the highest value for 15 g of NCG/d;The acetic acid/propionic acid showed lowest trends in bulls fed 15 g/d NCG compared with control;(8)According to the analysis of rumen microbial diversity:After adding NCG,the relative abundance of Bacteroidetes decreased linearly(P<0.1);The relative abundance of Firmicutes showed a linear increase trend(P<0.1);The bulls supplemented with 15 g/d NCG increased the relative abundance of the Ruminococcus 1 group than control(P<0.05);The relative abundance of Succinivibrio increased linearly with the increase of NCG,with 15 g/d significantly higher than the control group(P<0.05);(9)According to the analysis of rectum microbial diversity:The bulls supplemented with 15 g/d NCG increased the relative abundance of the Rikenellaceae-RC9-gut-group intestinal group than control(P<0.05);the relative abundance of Bifidobacterium intestinal increased(P<0.05)supplemented with 15 g/d and 25 g/d,compared with control group;The relative abundance of Ruminococcaceae UCG-010 significantly(P<0.05)increased in bulls fed 15 g/d NCG compared to control;(10)From the analysis of the relative abundances of rumen methanogenus at genus level,the relative abundances of Methanobrevibacter in rumen reduced with NCG addition,with the lowest value for 25 g/d NCG,which relative abundances was 80.05%;The relative abundance of Methanosphaera and Methanosaeta in rumen linearly(P=0.01)reduced with NCG addition;(11)Net income of group 15 g/d NCG was the highest,which was10.43 RMB that was 10.84%,14.99%higher than that of groups control,25 g/d NCG.It is concluded that under the conditions of this experiment,when the NCG supplemental level is 15 g/d,significantly improve the efficiency of feed conversion,increase the content of total amino acids in plasma,improve rumen fermentation and gastrointestinal micro-ecosystem,increase the number of intestinal beneficial bacteria,promote intestinal health,and nitrogen and methane emission reduction.