| The free-feeding mode is commonly applied in the feeding of finishing pigs,which will lead to reduced feed efficiency and lower carcass quality.Feed restriction improves the carcass quality of livestock and poultry by controlling feed intake or changing the nutritional level of feed,so that the quality of nutrients obtained is less than the normal amount.It was noteworthy that a decrease in energy intake caused food to be consumed in a short time,followed by more extended daily fasting periods,implying that the health effects of feed restriction may be partly attributed to prolonged fasting periods.Intermittent fasting reduces body weight,fat,and calorie intake,but there is a strong sense of hunger,which causes stress and leads to disorder of biological clock in animals.melatonin affects energy metabolism,blood lipids,and body weight,thereby regulating adipocyte metabolisms,such as lipolysis,lipogenesis,adipocyte differentiation and fatty acid uptake,so it is worth studying the effects of fasting and melatonin and their interaction on animals.The purpose of this study was to explore the effects and mechanism of intermittent fasting(IF)combined with melatonin supplementation on fat deposition,intestinal microbiota,and metabolism in model mice.In addition,the effects of feed restriction on growth,intestinal microbiota and metabolism of finishing pigs were investigated,to provide a theoretical basis for the popularization of feed restriction in animal production.1.Effects of fasting and melatonin supplementation on growth,intestinal microbiota and metabolism in mice.Forty-eight 6-week-old male C57BL/6J mice(23.0 ± 0.9 g)were randomly divided into 4 groups(n = 12/group): control group(C),intermittent fasting group(F),melatonin group(M),intermittent fasting + melatonin group(MF).Mice in group C and M had ad libitum access to food and water,and mice in group F and MF were fed every other day for 15 cycles.Melatonin was added to drinking water in M group and MF group,and the additive amount was adjusted according to the amount of drinking water so that the oral dose is 10 mg/kg body weight.Body weight,food and water intake of mice were measured daily.At the end of the experiment,mice were given intraperitoneal injection of pentobarbital sodium(50 mg/kg body weight).Blood was collected from the heart and the supernatant was achieved for serum biochemical index analysis.Epididymal fat,liver and intestinal tissue were collected for HE staining to observe the morphology;intestinal contents were collected for 16 Sr RNA gene sequencing and metabonomic analysis.The results showed that: 1)IF significantly decreased body weight gain,blood glucose,TC,TG,and insulin(P < 0.05),while exogenous melatonin significantly increased the level of serum melatonin in mice(P < 0.05).2)IF significantly reduced the volume of adipocytes and increased the number of adipocytes per square millimeter(P < 0.05).3)IF changed the structure of intestinal microbiota,profiles of microbiota group F and MF were significantly separated from that in group C and M.Fasting had a significant effect on Firmicutes,Bacteroidetes and Firmicutes/Bacteroidetes at phylum level.At genus level,the abundance of Lactobacillus,Ruminococcus,and Akkermansia in group F was significantly higher than that in group C(P < 0.05),while the abundance of Helicobacter,Prevotella,and Parasutterella in group F was significantly lower than that in group C(P < 0.05).4)Metabonomic analysis showed that there were significant differences in metabolites between group F and group C.The main metabolites in group F were sugars and amino acids,and the pathway of enrichment was mainly the catabolism of sugars and amino acids.Thus,IF can change the intestinal microbiota and metabolism of mice,and prevent obesity by reducing weight gain,blood glucose,TC,TG,and adipocyte size.2.Effects of feed restriction on growth,intestinal microbiota and metabolism of finishing pigs.Sixteen "Landrace × Yorkshire" crossbred castrated boars(86.13 ±3.50 kg)were selected and divided into two groups: control group(Con)and feed restriction group(Res).The Con group had ad libitum access to food and water,and the Res group was fed 70% of the Con for 38 days,during which the feed intake,body weight and backfat were recorded,and blood samples were collected.At the end of the experiment,the pigs were euthanized,and viscera was weighed.After collecting blood and centrifuging,the supernatant was used for the determination of serum biochemical indexes and amino acid levels.The liver and intestinal tissues were stained with HE to observe the morphology,and the colon contents were collected for 16 Sr RNA gene sequencing,metabolomics and short-chain fatty acid analysis.The results showed that: 1)The body weight,average daily feed intake and average daily gain of pigs in Res group were significantly lower than those in Con group(P < 0.01),and after 38 days of feed restriction,the backfat thickness of pigs in Res group was significantly lower than that in Con group(P < 0.05),and the longest muscle thickness was significantly higher than that in Con group(P < 0.05).2)On the20 th day of the experiment,the contents of serum total cholesterol(TC),triglyceride(TG),alanine aminotransferase(ALT)and aspartate aminotransferase(AST)in Res group were significantly lower than those in Con group(P < 0.05),while the content of creatinine(CREA)was significantly higher than that in Con group(P < 0.05).On the38 th day of the experiment,the contents of serum TC,TG,low density lipoprotein cholesterol(LDL-C),high density lipoprotein cholesterol(HDL-C),ALT and AST in Res group were significantly lower than those in Con group(P < 0.05),while the content of CREA in Con group was significantly higher than that in Con group(P <0.05).3)Compared with Con group,the concentrations of isobutyric acid,isovaleric acid and valeric acid in ileal contents of Res group were significantly higher than those of Res group(P < 0.05).4)Compared with Con group,the structure of intestinal microbiota in Res group did not change,but the relative abundance of Proteobacteria and Cyanobacteria decreased significantly(P < 0.05),Elusimicrobiota increased significantly at phylum level(P < 0.05).At genus level,the relative abundance of microbiota Lachnospiraceae＿XPB1014＿group,Candidatus＿Saccharimonas,Escherichia-Shigella and Gastranaerophilales decreased significantly(P < 0.05),while Romboutsia and unclassified＿c＿Bacilli abundance increased significantly in Res group compared with that in Con group(P < 0.05).5)There was a significant difference in intestinal metabolites between Res group and Con group,and the main differences between the two groups were some amino acids.The pathways of significant enrichment of metabolites in Res group were as follows: biosynthesis of pantothenic acid and coenzyme A,biosynthesis of phenylalanine,tyrosine and tryptophan,linoleic acid metabolism,phenylalanine metabolism,biosynthesis of valine,leucine and isoleucine,β-alanine metabolism,aminoacyl t RNA biosynthesis.Taken together,a 30% feed restriction decreased the growth performance of finishing pigs,but increased the thickness of longest muscle and the concentration of serum creatinine.Feed restriction decreased the level of blood lipid,and increased the concentration of isobutyric acid,isovaleric acid and valeric acid in colon content.Feed restriction did not change the structure of intestinal microbiota and affected the relative abundance of specific bacteria.Feed restriction changed intestinal metabolites and mainly affected the synthesis and decomposition of some amino acids.In this study,through intermittent fasting in mice and 30% feed restriction on finishing pigs,it was found that 30% feed restriction could improve feed utilization efficiency of pigs,and both feed restrictions could reduce weight gain,serum glucose and blood lipid levels,and significantly change intestinal metabolism. |
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