Effects Of Different Dietary Standards Ileal Digestible Lysine To Net Energy Ratio On Growing-finishing Pigs

The metabolism of energy and amino acid in pig body is a complex process crisscrossing.Excess or insufficiency of energy or amino acids will affect the metabolic process of energy and amino acids in the body,resulting in low utilization of nutrients.Digestible Energy available directly to animals is called available Energy.According to digestible Energy availability in feed,digestible energy can be expressed as DE,Metabolizable Energy,ME and Net Energy,NE)system.NE system is the closest to reflect the real energy value used to maintain the growth of finishing pigs,and more accurate evaluation of feed energy value,which is of great significance for commercial breeding and saving feed cost.Lysine(Lys)is considered to be the first digestible amino acid of corn-soybean meal diet,which is not available effectively in the posterior intestine of the body.Therefore,Standard Ileal Digestibility Lys(SID)is commonly used to express the value of digestiys in feed and the actual requirements of animals.However,the fattening rate of pigs in the fattening stage mainly depends on the ratio of dietary amino acids(mainly Lys)to energy,so it is of great significance to explore the optimal SID Lys to NE ratio.Therefore,according to NRC(2012),the most appropriate SID Lys content was determined to be 0.73,and the fiber content was adjusted by adjusting the fine bran content,so as to adjust the energy level,so as to explore the effects of different SID Lys to NE ratios on growth performance,slaughter performance,intestinal morphology and microorganisms of finishing pigs.Experiment 1: Effects of different proportions of SID Lys and NE on growth performance of finishing pigs.The aim of this experiment was to investigate the effects of different proportions of SID Lys and NE on growth performance of finishing pigs.Forty finishing pigs(99.39±6.60 kg)with good health,similar physiological age and similar body weight were selected in the experiment using a single factor completely randomized design.The pigs used in the experiment were Duroc x long x large three hybrid pigs.They were randomly divided into 5treatment groups with 8 replicates per treatment(5 sows,3 boars)and 1 pig per replicate.Single column feeding method was used.The feed NE values of the five treatment groups were 2250 kcal/kg,2300 kcal/kg,2350 kcal/kg,2400 kcal/kg and 2450 kcal/kg,respectively,and the content of SID Lys was 0.73.That is,the SID Lys to NE ratios of the 5 treatment groups were 3.25 g/Mcal(SLLNE group),3.18 g/Mcal,3.11 g/Mcal(SLMNE group),3.04g/Mcal and 2.97 g/Mcal(SLHNE group),respectively.The experimental period lasted for 35days(pre-feeding period lasted for 7 days,formal experiment period lasted for 28 days).The formal experiment period was divided into two stages,and fasting weighing was carried out at the end of each stage.The test results show that: Under the condition that SID Lys content was kept constant,the average daily feed intake(ADFI)of finishing pigs in the second stage was linearly decreased with the decrease of the ratio of SID Lys to NE,that is,the increase of NE level(P < 0.01),and the ADFI in the whole period was linearly decreased.In the second stage,the average daily gain(ADG)showed a quadratic curve of first decreasing and then increasing(P < 0.05),but there were no significant differences in other growth performance indexes.Experiment 2: Effects of different proportions of SID Lys and NE on Slaughter performance of finishing pigs.The aim of this experiment was to investigate the effects of different SID Lys to NE ratio on slaughter performance of finishing pigs.The design of the experiment is the same as that of experiment 1.The results showed that,under the condition that the SID Lys content was kept constant,the ratio of SID Lys to NE had no significant effect on the slaughter performance of finishing pigs,including carcass performance,organ index and meat quality,and there was no significant difference in the slaughter performance indexes.Experiment 3: Effects of different proportions of SID Lys to NE on Intestinal morphology and microbiota of finishing pigs.The aim of this experiment was to investigate the effects of different proportions of SID Lys to NE on intestinal morphology and intestinal microbiota of finishing pigs.The design of the experiment is the same as that of experiment 1.According to the above growth performance data analysis results,the SID Lys to NE ratios of 3.25 g/Mcal(SLLNE group),3.11 g/Mcal(SLMNE group)and 2.97 g/Mcal(SLHNE group)were selected and divided into three groups.The experimental results showed that:(1)Under the condition of maintaining a certain SID Lys content,the intestinal morphology of SLHNE group was better with the decrease of SID Lys to NE ratio(the increase of NE level).Compared with SLLNE group and SLMNE group,the ileum villi height of SLHNE group was significantly increased(P < 0.05).There was a linear increase(P < 0.05),and no significant difference between the crypt depth and villus crypt ratio.There was no significant difference in each index between SLLNE group and SLMNE group.There were no significant differences in jejunum indexes among all groups.(2)Under the condition of maintaining a certain SID Lys content,intestinal microorganisms in SLHNE group were more abundant with the decrease of the ratio of SIDLys to NE,that is,the increase of NE level.The results of α diversity showed that the richness and diversity of microflora in SLHNE group were significantly higher than those in SLLNE group(P < 0.05).β diversity results showed that there were significant differences in posterior intestinal segment(cecum,colon and rectum)between the three groups(P = 0.001),significant differences in posterior intestinal segment(cecum,colon and rectum)between SLLNE group and SLHNE group(P < 0.01),significant differences in rectum between SLMNE group and SLHNE group(P < 0.01),compared with SLLNE group,The community distribution of SLHNE group was more concentrated,and the similarity between SLHNE group and SLLNE group was low.At the phylum level,Firmicutes and Proteobacteria dominated jejunum and ileum.Firmicutes and Bacteroidetes were dominant flora in cecum,colon and rectum,and Firmicutes accounted for more than50%.In the cecum and colon,the abundance of Firmicutes in the colon of SLHNE group was significantly higher than that of SLLNE group(P < 0.05).In front of the genus level,bowel advantage bacterium group as the Lactobacillus 、 Escherichia-Shigella and Clostridialessensustricto1,after bowel flora primarily for Lactobacillus、Trichospirillus and Prevotellas.The SLHNE formation enriched Christensenellale and Akkermansia,while the SLLNE and SLMNE formations enriched Lachnospira、 Prevotella-9 and Fournierella.With the decrease of SID Lys to NE ratio,that is,the increase of NE level,the average daily feed intake(ADFI)of finishing pigs in the second stage was significantly decreased(P< 0.01),and the ADFI in the whole stage was linearly decreased(P < 0.10).The average daily gain(ADG)in the second stage showed a quadratic trend of first decreasing and then increasing(P < 0.05),and there were no significant differences in other growth performance indexes,indicating that the ratio of SID Lys to NE had a time effect on the effect of finishing pigs.Low SID Lys to NE ratio improved the foregut morphology of finishing pigs to a certain extent.It was found that low SID Lys to NE ratio improved the microflora structure of post gut of finishing pigs,and the increase of ADG may be related to the enrichment of probiotics.In conclusion,SID Lys / NE = 2.97 is more suitable for late finishing pigs within a certain range.