Effect Of Dietary Net Energy Level On Growth Performance,Intestinal Health And Liver Metabolism In Fattening Pigs

Energy is one of the essential nutrients for animal development.In the swine industry,feed cost is one of the important factors to determine the production cost,accounting for about 70% of the total cost,while energy cost accounts for a considerable proportion of the feed cost.Therefore the fluctuation of energy price in feed will have an important impact on the breeding efficiency.The common feed energy systems for pigs include Digestible Energy(DE),Metabolizable Energy(ME)and Net Energy(NE),which have limitations such as overestimating the effective energy value of high protein and high fibre feeds and underestimating the effective energy value of high starch or high fat feeds.or high-fat feeds,leading to increased inaccuracies and increased feed processing and farming costs.In contrast,the NE system takes into account all energy losses during metabolism,and the use of NE as a feed formulation can increase production efficiency.The effect of NE system on average daily gain(ADG)of fattening pigs is a controversial topic.In order to further investigate the relationship between NE and ADG of fattening pigs,this experiment was designed with three different NE levels based on NRC(2012),Danish Nutrient Requirement Standard(29th edition)and the latest Chinese nutritional standard,aiming to investigate the effect of dietary NE level on The aim was to investigate the effects of dietary NE levels on growth performance,intestinal health and liver metabolism in fattening pigs.The experimental design was as follows:Exp.1: Effect of dietary NE level on growth performance,carcass quality and nutrient digestibility of fattening pigs.The aim was to investigate the effect of diet NE level on growth performance,carcass quality and nutrient digestibility of fattening pigs.The experiment was conducted in a one-way completely randomized group design with 84 healthy fattening pigs of similar body weight(53.69±5.99 kg)and similar physiological age.The pigs were randomly divided into 3 treatment groups(9.44 MJ/kg,9.90 MJ/kg and 10.36 MJ/kg,LNE,MNE and HNE groups),with 3 replications per treatment and 7 pigs(4 males and 3 females)in one replication.The experiment was divided into three phases,each phase for 21 d.Fasting weighing was performed at the end of each phase,and manure was collected on the last three days of the experiment to determine nutrient digestibility.The results showed that: the energy conversion ratio(ECR)of the LNE group was significantly lower in the first stage(P < 0.05),and the daily net energy intake(DNEI)increased linearly with the increase of dietary NE level,and the ADG increased linearly in the whole period(P < 0.05);compared with the LNE and MNE groups compared with the LNE and MNE groups,there was an increasing trend of eye muscle area in the HNE group(P < 0.10);the rest of carcass characteristics were not significantly different;dietary NE level had no significant effect on nutrient digestibility of fattening pigs.Exp.2: Effect of dietary NE level on diarrhea,intestinal morphology and gut microbiology in fattening pigs.In this experiment,the level of NE was mainly regulated by regulating the content of crude fiber,LNE means high fiber and HNE means low fiber.In order to investigate whether the level of NE affects the growth performance of fattening pigs by affecting their intestinal health,this experiment examined the diarrhea,small intestinal morphology and large intestinal microbiology of fattening pigs during the whole period.The results showed that: dietary NE level did not have significant effect on diarrhea of fattening pigs;the height of jejunal villi increased linearly with the increase of dietary NE level;the dominant cecum microbial at the phylum level were Firmicutes,Bacteroidetes and Proteobacteria,and the dominant colon microbial at the phylum level were Firmicutes,Bacteroidetes and Spirochaetae,the composition of the top 10 microorganisms at the phylum level of cecum and colon was basically the same;the dominant cecum and colon microbial at the genus level were unclassified-Lachnospirceae,Prevotella-9,Streptococcus and Lactobacillus;no significant differences in alpha diversity and beta diversity in both cecum and colon;at the genus level,fiber-degrading bacteria such as Prevotella＿7,Lachnospira and Coprococcus were significantly enriched in the LNE group,and Probiotic bacteria such as Romboutsia and unclassified＿Clostridia＿UCG＿014 were significantly enriched in the HNE group.Exp.3: Effect of dietary NE level on liver metabolism in fattening pigs.The results of experiment 1 showed a linear increase in DNEI at all stages with increasing dietary NE levels,as well as a linear increase in ADG over the whole period.This result is not consistent with the results of most scholars on the effects of NE and fattening pigs.To further investigate the mechanism of the effect of dietary NE level on ADG in fattening pigs,this experiment analyzed three groups of liver metabolomics and combined the results with microbiomics results,aiming to investigate the effect of dietary NE level diets on liver metabolism in fattening pigs and the reasons for the differences in ADG.The experimental design was the same as experiment 1,and the results showed that:5977 metabolites were detected in the three groups in the default mode,among which 1733 differential metabolites were detected;PCA plots showed that metabolites in the three groups were not significantly separated,and those in the LNE and HNE groups were significantly separated;among the KEGG enrichment pathways,metabolites related to pantothenic acid and Co A synthesis and protein digestion and absorption pathways were enriched in the LNE group(P < 0.05),the metabolites related to propionate metabolism and vitamin digestion and absorption pathway were enriched in the HNE group(P < 0.05),and most of the microorganisms enriched in the HNE group were positively correlated with metabolites related to vitamin digestion and absorption and propionate metabolism,while the microorganisms enriched in the LNE group were positively correlated with metabolites related to protein digestion and absorption,pantothenic acid and Co A synthesis pathways;In the joint analysis of the data from both LNE and HNE groups,the results showed that Faecalibacterium was highly significantly and positively correlated with2,4,4-Trimethylcyclopentanone and 2-(3,4-dimethoxyphenyl)ethanamine,and highly and negatively correlated with Nitrous oxide,Carbidopa,Evogliptin and so on.In summary,the ADG of fattening pigs increased linearly with the increase of dietary NE level,and fattening pigs may need lower NE in the growth period and higher NE in the fattening period.high NE level improved the morphology of small intestine and structure of colonic microflora in fattening pigs,and the increase of ADG in fattening pigs may be related to the enrichment of beneficial bacteria;under the condition of insufficient energy intake,fattening pigs mainly supply energy to the body through pantothenic acid and Under the condition of insufficient energy intake,fattening pigs mainly supply energy to the body through pantothenic acid and Co A metabolism and protein catabolism,while the reason for lower ADG in the LNE group may be related to the deficiency of propionic acid and vitamin.