Effects Of Valine On The Reproductive Performance Of Sows And Its Related Mechanism During Gestation And Lactation In A Hot,Humid Environment

Heat stress impacts the reproductive performance of sows and the growth performance of piglets during summer months.During gestation and lactation,heat-stressed sows reduce their feed intake,lose body weight,have a reduced litter size,which can negatively affect piglet growth.Dietary formula modification is often used on farms due to its convenience and cost.Valine is one of the essential amino acid for animals,which involve in increasing the average daily feed intake,participating protein synthesis and alleviating a protein imbalance causing by heat stress.Valine deliver energy for the synthesis of lactose and fatty acid in milk in the mammary gland.The research on valine is mainly focused on its suitable requirement,and the effect on the reproductive performance of sow in the hot,humid environment is unknown.Therefore,the aim of the present study was to investigate the effect of valine-to-lysine ratio on reproductive performance of sows in a hot,humid environment,and analysed related parameters for research on its mechanism,which provides theoretical basis for the development and application of valine in sows’ feed.The study mainly consists of 2 parts.1.Effects of valine on the reproductive performance of sows in a hot,humid environmentTwenty-seven PIC sows(average parity=5.08)were randomly divided into five experimental groups with five ratios of total Val to Lys of 0.75:1,0.87:1,0.99:1,1.11:1,1.23:1 from day 85 of gestation to 21 day of lactation.5 or 6 sows per group(temperature:24 to 28℃,relative humidity:60 to 85%).The placentas were collected immediately after farrowing for mRNA analysis.The results showed that dietary valine improved the average daily feed intake(P<0.05)of the sows in the lactation and increased daily litter gain(P<0.05)form day 7-14 after farrowing and decreased the number of still born(P<0.05).Furthermore,the back fat thickness and weaning-to-estrus interval of sows did not differ among the groups.The concentrations of colostrum.compositions were similar among the five treatment groups.Dietary valine increased the placental area and the fetal-to-placental weight ratio in sows.Additionally,the placental gene expression of LAT1,4F2hc,LAT2,LAT3,SNAT1,SNAT2 and SNAT4 increased(P<0.05)in the groups which diets containing higher Val:Lys ratios.The increase in the ratio of dietary Val:Lys increased the expression of GLUT3,GLUT4 and GLUT5 genes(P<0.05)in the placenta tissue.In addition,compared with group 1,with the Val:Lys ratio increased,the mRNA expression levels of 4EBP1,S6K1,eIF4E,RPS6,mTOR,eEF2 and eIF2α significantly increased(P<0.05).In conclusion,in a hot-humid environment,increasing the Val:Lys ratio improve the growth performance in piglets,improve the placental performance of the sows,and regulate of the nutrients transporters factors in placentas.2.Mechanism of effects of dietary valine supplementation on reproductive performance in sowsBased on the results of the previous experiment,three ratios were selected for this experiment.Eleven Large White × Landrace sows(average parity=2.27)were selected and randomly assigned to 3 groups.The diets contained total dietary Val:Lys ratios of 0.72,0.87,or 1.01:1.Sows were fed from d 29 prepartum to d 21 postpartum in a hot,humid environment(temperature:22 to 31℃,relative humidity:69 to 96%).The results showed that dietary valine improved the average daily feed intake(P<0.05)of the sows in wk3 of the lactation and the average daily gain(P<0.05))of the piglets from day 7-14 after farrowing.Dietary valine increased the concentrations of lactose in colostrum and immunoglobulin M(P<0.05)in piglet serum.Additionally,dietary valine affected metabolite and metabolic hormone concentrations.The increase in the ratio of dietary Val:Lys decreased the blood urea nitrogen(P<0.05)and increased serum glucose(P<0.05)in the sows and increased serum albumin(P<0.05)in the piglets.With the increase of Val:Lys level in the diet,the level of GSH-PX,T-AOC,GSH-PX and CAT in the serum of sows significantly increased(P<0.05),and the GSH-PX levels in piglets serum significantly increased(P<0.05).The E.coli significantly decreased(P<0.05)in sows’feces.In addition,increasing dietary Val:Lys increased the serum concentration of estradiol-17β in the sows.In conclusion,in a hot,humid environment,dietary valine could increase the average feed intake and the serum glucose in sows,improve the lactose in lactose in colostrum,which have a positive effect on milk yield.On the other hand,the increasing of estradiol-17β increased milk yield and then improve the piglets growth performance.Meanwhile,the immunity of piglets may improve by increasing the IgM in piglets serum.Additionally,dietary Valine regulated the oxidative parameters in sows serum and E.coli in sows feces,which may alleviate the heat stress.These findings suggest that in hot,humid environments,it may be useful to supplement the appropriate amount of valine to alleviate heat stressinduced seasonal infertility in sows.