Effects of Diets with Different NFC/NDF Levels on the Rumen Fermentation Parameters and Bacterial Community in Male Calves

LI Lan-jie;CHENG Shu-ru;DIAO Qi-yu;FU Tong;BI Yan-liang;WANG An-si;LI Ming;TU Yan;Key Laboratory of Feed Biotechnology of Ministry of Agriculture,Feed Research Institute,Chinese Academy of Agricultural Sciences;College of Animal Science and Technology,Gansu Agricultural University;College of Animal Husbandry and Veterinary Science,Henan Agricultural University;

weaned beef calves;;non-fiber carbohydrate/neutral detergent fiber ratio;;rumen fer mentation parameters;;rumen microbial community

This study assessed the effects of diets with different non-fiber carbohydrate(NFC)/neutral detergent fiber(NDF)levels on rumen fermentation parameters and bacterial community of male calves.Thirty 2-3 month-old healthy weaned male calves with(94.38±0.25)kg wererandomly divided into 2 groups with 15 calves each,and were fed 2 types of total mixed ratio diet with the same crude protein level and different NFC/NDF ratios(1.35(A)and 0.80(D)),respectively.The experiment lasted for 105 d,with 15 dof adaptation period and 90 dof formal period.Six calves in each group were selected to collect rumen fluid through oral for 2 hours after morning feeding on the 120,150 and 180 d.The pH,volatile fatty acids(VFA)and NH3-N concentration and rumen microbial diversity of the rumen fluid samples were determined.The results showed that:1)The dietary NFC/NDF levels had no significant effect on rumen fluid pH and total VFA concentration(P>0.05);2)Acetate,NH3-N concentration and acetate/propionate ratio in group A were significantly lower than that in group D(P<0.05),propionate content in group A were significantly higher than that in group D(P<0.05);3)The microbial diversity parameters of rumen fluid of calves in group A were significantly lower than that in group D(P<0.05);4)At the phylum level,bacteriodetes proportion accounting for the total number of sequences of calves in group A was significantly higher than that in group D(P<0.05),Christensenellaceae_R-7 and Prevotellaceae_UCG-003 proportions accounting for the total number of sequences of calves in group D was significantly higher at the genus level than that in group A(P<0.05);5)With the age increasing,the diversity indices except for Shannonindex,were significantly different between the 2 groups(P<0.05),but there was no significant difference in rumen microbial composition between the 2 groups(P>0.05).In summary,the dietary NFC/NDF levels significantly affect the species and abundance of the rumen microorganisms,and the level of genus of microorganisms,finally affect the yield of acetate and propionate.