Effects Of Diets With NDF Source On The Growth Performance And Rumen Development In Post Weaning Calves

The objective of this study was to investigate the effects of tatal mixed ration（TMR）with different NDF sources on growth performance,nutrient’s digestion and metabolism,rumen fermentation and rumen development of post-weaned calves.Firstly,the experiment was to conducted to evaluate the effect of the diet with alfalfa hay or soybean hull as the main NDF source were used to study the growth performence,nutrients’s digestibility and metabolism,rumen development,rumen microorganisms,metabolites of rumen metabolomics,and metabolic pathways of post-weaning calves.Which were studied to reveal whether forage should be added as the main source of NDF in weaning calves.Secondly,the experiment was conduced to evaluate the application of bamboo leaves and tea-leaves residue as some raw materials in post-weaned calves feed through trial and digestion and metabolism tests.Part 1Effects of diets with alfalfa hay or soybean hull as the main NDF source on the growth performance and rumen development in post-weaned calvesThis study was to evaluate the effects of inclusion of alfalfa hay（AH）or soybean hull（SH）as te main NDF source in TMR determine whether pasture needs to be added in the diet of post-weaned calves.Thirty clinically healthy Chinese Holstein bull calves（d:105;BW=92.77±5.61kg）were selected and randomly assigned to two treatments with 15 calves per group.Calves were fed total mixed ration（TMR）in the experiments,with different NDF sources of alfalfa hay（AH）or soybean hull（SH）as the experimental factors at the same neutral detergent fiber（NDF）level.The experiment was conducted over 75d,with the first15d for adaptation.Over the entire of the experiment period（d 120-180）,feed to gain ratio was lower in post-meaning calves fed SH diet compared to AH diet（P<0.05）.The calves fed SH diet showed higher（P<0.05）ADG than AH diet at 120-135 d.The fecal output,total energy intake,fecal energy,urine energy,methane energy and fecal nitrogen in SH diet was significantly lower than that in AH diet（P<0.05）.However,the apparent digestibility of dry matter,organic matter,NDF and ADF in SH diet were significantly higher than those in AH diet（P<0.05）.The DE/GE,ME/GE,ME/DE,sedimentary nitrogen,nitrogen retention rate,and nitrogen digestibility were higher（P<0.05）,whereas the serumβ-hydroxybutyric acid concentration was lower（P<0.05）in SH group than those in AH group.During in study（d 120-180）,SH diet can be degrade rapidly in rumen.The post-weaning calves fed SH diet showed higher（P<0.05）total VFA concentration,and propionate and butyrate concentration,but lower（P<0.05）acetate concentration than those fed AH diet.The emphty weights of rumen,and percentage of body weight slaughter,empty weight stomach complex compared was greater（P<0.05）in SH diet than those in AH diet.The proportions of omasum and abomasum per stomach complex weight in the stomach were lower in SH than those in AH diet（P<0.05）.SH diet increased（P<0.05）rumen muscle layer thickness,rumen wall thickness,papillae length,epithelium thickness,and stratum spinosum compared with AH diet.The xylanase activity of the rumenβ-glucosidase was higher（P<0.05）for SH diet than in AH diet.The diversity of rumen microorganism was analyzed by 16S r DNA technique.The OUTs,Chao1,ACE,observed＿species,and shannon index was lower in post-meanning calves fed SH diet compared to those fed AH diet（P<0.05）.The relative abundance of Spirochaetae（P<0.05）was lower in SH diet than in AH diet.In the Bacteroidetes,the percentage of Rikenellaceae＿RC9＿gut＿group、Prevotella＿1、Prevotellaceae＿Ga6A1＿group,and Prevotellaceae＿UCG-001 were lower（P<0.05）in SH than those in AH diet.In the firmicutes,the percentage of Succiniclasticum,Lachnospiraceae＿NK3A20＿group,gauvreauii＿group,and Erysipelotrichaceae＿UCG-002 was greater in SH than those in AH diet（P<0.05）.On the contrary,the percentages of Christensenellaceae＿R-7＿group,Ruminococcaceae＿NK4A214＿group,Coprococcus＿2 were lower（P<0.05）in SH than those in AH diet.This study aimed to compare the composition of whole-ruminal metabolites in post-meaning calves fed between AH diet or SH diet using modern metabolome analysis.It was found that SH diet increased（P<0.05,VIP>1,FC>2 or FC<0.50）the concentration of degradation products including carboxylic acids,carbohydrates,lipids and lipid-like molecules,nucleosides,nucleotides,and alogues,and vitamin,and some fatty acyls and carboxylic acids.The enrichment analysis of differentially expressed metabolites indicated that fourteen pathways,including amino sugar and nucleotide sugar metabolism;thiamine metabolism;linoleic acid metabolism;cysteine and methionine metabolism;sphingolipid metabolism;alanine,aspartate and glutamate metabolism;starch and sucrose metabolism;phenylalanine metabolism;alpha-Linolenic acid metabolism;Phenylalanine,tyrosine and tryptophan biosynthesis;tyrosine metabolism;taurine and hypotaurine metabolism;inositol phosphate metabolism;valine,leucine and isoleucine biosynthesis were significantly enriched（P<0.01,Impact value>0.10）after the diet treatments.Correlation network analysis revealed that SH diets altered the ruminal metabolic pattern,which led to the transfer to the metabolic pathway of volatile fatty acids.Therefore,the results suggested that soybean hull as NDF source was a better choice as the main NDF source for post-weaning calves.Part 2 Application of bamboo leaves and tea-leaves residue to diet of post-weaning calvesThis study was conducted to evaluate the effects of bamboo leaves（BL）or tea-leaves residue（TR）replacing alfalfa hay（AH）on growth,nutrients’s digestion and metabolism,rumen fermentation and rumen bacterial of post-weaning calves fed with total mixed ration（TMR）at the same neutral detergent fiber（NDF）level.Forty-five Holstein male calves were arranged to three groups based on the randomized block design,and they were fed three different TMR with with alfalfa hay（AH）,bamboo leaf（BL）or tea residue（TR）,respectively,as the main NDF sources.The experiment was conducted for 75 days,with the first 15 days for adaptation.During in study,no significant difference was found on body weight（BW）and body size measurement growth between AH and BL diet（P>0.05）.The fecal score（P=0.0969）and diarrhea rat（P=0.0939）had a tendency to be greater in post-weaning calves fed BL than in AH.Apparent digestibility of acid detergent fiber（ADF）,dry matter（DM）,nitrogen and gross energy was lower（P<0.05）in BL than in AH diet.The post-meaning calves fed BL diet showed much lower urine energy,digestible energy（DE）per gross energy（GE）,metabolizable energy（ME）per GE,ME per DE,and were lower（P<0.05）in BL diet than those in AH diet.Body weight and body size were lower（P<0.05）in TR diet than those in AH diet.Apparent digestibility of NDF and fecal nitrogen were higher（P<0.05）in TR diet,but nitrogen retention rate was lower（P<0.05）compared to AH diet.The post-meaning calves fed BL and TR diet showed lower（P<0.05）serum Antioxidant index than the AH diet.Over the entire of the experiment period,the relative abundance of Ruminococcus＿1 and Treponema＿2（P<0.05）for BL diet were lower than those in AH diet,but no significant difference were found（P>0.05）on rumen fermention index,community diversity and relative abundance of rumen bacterial between two diet.The post-weaning calves fed TR diet showed lower rumen propionate proportion,acetate/propionate ratio,and rumen NH₃-N concentration than AH diet（P<0.05）.TR diet improved rumen microbial diversity.At the phylum level,the relative abundance of Rikenellaceae＿RC9＿gut＿group in Bacteroidetes was up-regulated（P<0.05）,but the relative abundance of Lachnospiraceae＿NK3A20＿group in Firmicutes was down-regulated（P<0.05）in TR diet.In conclusion,the inclusion of bamboo leaves（BL:24.38%,DM basis）replacing with alfalfa hay for post-meaning calves as the main NDF source in TMR diet was more favorable than tea-leaves residue（24.43%,DM basis）for post-weaned calves.