Effects Of Different NFC/NDF Pelleted Total Mixed Ration On Growth Performance,Rumen Microbiota And Its Metabolites Of Holstein Growing Cattle

As a new dietary supply method for ruminant breeding,pelleted total mixed ration(PTMR)plays a positive role in improving animal growth performance,reducing picky eating,reducing feed cost,decrasing labor force and-improving the quality of livestock products compared with conventional loose total mixed ration(Total mixed ration,TMR).TMR has become a common practice since it was introduced into ruminant production more than half a century ago.Although the advantages of TMR are many,there are certain limitations of this feeding method.For example,it is easy to cause selecting concentrate feed.This has led to a recent trend to provide PTMR to sheep and goats in some parts of the world and has gradually become a research hotspot.However,there are few reports on the effects of different NFC/NDF PTMR on growth performance,rumen inflammatory response,fermentation characteristics,rumen microbiota and metabolites of Holstein growing cattle.The purpose of this study was to explore the effects of feeding different NFC/NDF PTMR on growth performance,rumen microbiota and metabolic mechanism of Holstein growing cattle.The specific contents are as follows:Experiment 1.Under the same NFC/NDF condition,the effects of conventional loose TMR and PTMR on growth performance,nutrient digestion and rumen fermentation indexes of Holstein growing cattle were tested to explore whether PTMR diet was suitable for Holstein growing cattle.Sixteen Holstein growing cattles with similar body weight(301 ± 10.3 kg)at 8 months of age were randomly divided into 2 groups with 8 Holstein growing cattles in each group.The control group was fed with conventional loose total mixed ration(COT),and the experimental group was fed with PTMR(Low NFC/NDF pelleted total mixed ration,LPT).In addition,three healthy Holstein cows(average body weight 500 ± 30 kg)with permanent rumen cannulas were selected.The experiment was divided into two phases,the first phase fed COT for 2 weeks and the second phase fed LPT for 2 weeks.The results demonstrated as following:1)Compared with COT group,PTMR in LPT group had no effect on rumen pH value,while DMI,ADG,WHC and BLC in LPT group were significantly increased by 6.53%,9.77%,50.0%and 40.0%,respectively(P<0.05);LPT significantly reduced F/G(P<0.01),FC and HGC(P<0.05),decreased 9.74%,6.93%and 25.0%,respectively.2)Compared with COT group,apparent digestibility of DM and NDF were significantly increased in LPT group(P<0.05),increased by 11.04%and 12.80%,respectively;Apparent digestibility of ADF in LPT group were significantly increased by 9.37%(P<0.01).3)The daily feeding time,rumination time,and chewing time in COT group were significantly longer than those in LPT group(P<0.05),increased by 9.55%,14.15%,and 12.19%,respectively.The COT group had significantly longer feeding time and chewing time per-kilogram of DM than the LPT group(P<0.05).At the same time,the COT group had significantly longer feeding time,rumination time and chewing time per kilogram of NDF than that in LPT group(P<0.05).4)Compared with COT group,no significant difference was observed in blood biochemical indexes,serum biochemical indexes and ruminal fermentation parameters of Holstein growing cattle in LPT group(P>0.05).Experiment 2.By increasing the ratio of NFC/NDF in the dietary formula,the effects of different NFC/NDF PTMR on growth performance,nutrient digestion and blood biochemical indexes of Holstein growing cattle were investigated.The LP T group in experiment 1 was used as the control group.E ight Holstein growing cattles with similar age(8 months)and body weight(301 ±11.5 kg)were selected as the experimental group.The experimental group was fed PTMR(High NFC/NDF pelleted total mixed ration,HPT).In addition,In addition,fistulas cows in experiment 1 were used to determine the changes of dietary effects on.rumen pH in the two groups for continuous 12 hours.The experiment was divided into-two phases.The first phase was fed low LPT for 2 weeks,and the second phase was fed HPT for 2 weeks.The results demonstrated that:1)The HPT group significantly reduced rumen pH and would put cows in SARA state compared with the LPT group.2)The LPT group significantly increased FBW,DMI,ADG,WHC and-BLC by 3.79%,5.71%,18.70%,28.57%and 16.67%,respectively,compared with the HPT group(P<0.05).Compared with the HPT group,the LPT group significantly reduced F/G and FC(P<0.01),decreased by 12.24%and 15.35%,respectively.3)The apparent digestibility of DM and NDF in the LPT group was significantly increased by 3.41%and 4.26%,respectively,compared with the HPT group(P<0.05).Apparent digestibility of ADF in LPT group were increased by 8.02%significantly(P<0.01).Experiment 3.Through the study of PTMR with different NFC/NDF on rumen fermentation and epithelial inflammatory response of Holstein growing cattles,the effect of increased NFC/NDF in PTMR on BRECs inflammatory response was evaluated.The test design was the same as experiment 2.The results demonstrated that:1)The pH value,MCP and A/P in the HPT group significantly decreased by 8.57%,12.46%and 23.71%,respectively,compared with the LPT group(P<0.05);The HPT group significantly increased TVFA,acetate,propionate and valerate by 13.49%,19.59%,52.70%and 30.29%,respectively.2)The mRNA expression of pro-inflammatory factors IL-1β,TNF-α and IL-6.(P<0.05)in BRECs was significantly up-regulated in HPT group compared with LPT group.3)The HPT group could significantly promote the mRNA expression of CCL28,CCL20 and CXCL2,CXCL3,CXCL9 and CXCL14(P<0.05)in BRECs compared with the LPT group.4)The HPT group had significantly increased MDA and H2O2 contents in BRECs(P<0.05),and significantly decreased T-AOC,SOD and GSH-Px contents(P<0.05)compared with LPT group,indicating that feeding a high NFC/NDF diet had a damaging effect on the rumen epithelium of Holstein growing cattle.Experiment 4.The experiments were conducted to investigate the effects of different NFC/NDF PTMR on rumen microbiota changes in Holstein growing cattle.The test design was the same as experiment 1 and experiment 2.The results demonstrated that:1)At the phylum level,Bacteroidetes and Firmicutes were the dominant bacteria in the rumen of Holstein growing cattle in COT,LPT and HPT groups.The LPT and HPT groups significantly increased the proportion of Actinobacteriota(P<0.05),and significantly decreased the content of Euryarchaeota(P<0.05).At the genus level,the LPT and HPT groups significantly increased the proportions of Olsenella and Pseudoscardovia(P<0.05).Compared with the LPT group,the HPT group significantly reduced the content of Prevotellaceae and Methanobrevibacter(P<0.05).2)At the phylum level,the abundance of Streptophyta and Apicomlexa in the LPT group was significantly increased(P<0.05);At the genus level,ichia and Entodinium were significantly reduced in the LPT and HPT groups(P<0.05),while Choanozoa-vertebrata and un known-Streptophyta increased significantly(P<0.05).3)The proportions of Mucoromycota and Basidiom ycota were significantly increased in LPT and HPT groups(P<0.05).At the genus level,the-proportions of Aspergillus and Mucor were significantly increased in the LPT and HPT groups(P<0.05).Experiment 5.The effects of different NFC/NDF PTMR on ruminal metabolite changes in Holstein growing cattle were investigated.The test design was the same as experiment 1 and experiment 2.The results demonstrated that:A total of 122 differential metabolites were identified in the LPT and HPT groups.Most of the metabolites were mainly involved in starch and sucrose metabolism and pyruvate metabolism pathways and other pathways related to carbohydrate metabolism.However,among the differentially up-regulated metabolites in the HPT group,It was found that Putrescine,Cholamine,UMP,2-naphthylamine,DihydrouraciL and 3-methylxanthine were adverse to the rumen affected by the abnormal differential metabolites.In conclusion,in this experiment,PTMR in the low NFC/NDF group can significantly improve the growth performance and the abundance and diversity of rumen microbiota and significantly reduce the feed to gain ratio and feed cost,which is recommended for Holstein growing cattle aged 8-10 months fattening in the production.However,PTMR in the high NFC/NDF group could increase the expression of pro-inflammatory factors and chemokines,decrease the abundance of rumen microbiota in the rumen and produce differential metabolites such as Putrescine and Cholamine,which are unfavorable to the rumen and may be the main mechanism of its effect on the growth of Holstein growing cattle.