| Postpartum fetal intrauterine developmental limitation is an important reason for the high incidence and mortality of newborn piglets.Enhanced fetal protein deposition is a key factor in determining fetal intrauterine development.How to promote the deposition of nutrients in fetal pigs in late pregnancy and improve their birth weight are still the key scientific officials to improve sow breeding efficiency.Studies have shown that leucine plays an important role in regulating protein synthesis and promoting animal growth.The aim of this study was to investigate the effects of dietary leucine on fetal intrauterine development and its underlying mechanism.Two hundred healthy sows were randomly divided into 4 groups according to the principles of genetic background,parity,body condition and reproductive performance.At late pregnancy,sows were fed with the following four test diets:(1)control group(CON): fed corn-soybean meal base sow diets;(2)0.40% LEU group: fed basal sow diets + 0.40% leucine;(3)0.80% LEU group: fed basal sow diets + 0.80% leucine;(4)1.20% LEU group: fed basal sow diets + 1.20% leucine.The same diet was fed in each group at lactation.Before farrowing,sow blood were collected;at farrowing,sow placenta and umbilical cord blood were collected;after farrowing,reproductive performance was calculated;collection of colostrum and milk were for the determination of milk composition;during the newborn piglet slaughter test,piglets blood,intestine and longissimus dorsi muscle were collected.The expression of LAT1,SNAT1,SNAT2,4F2 hc and rBAT protein were detected by piglet jejunum,ileum,ileum,longissimus dorsi muscle and sow placenta.The expression of mTOR signaling pathway proteins were measured in piglet longissimus dorsi muscle.The results showed below:(1)Reproductive performance: Supplemented with 0.80% leucine in the late gestation sow diets significantly increased mean piglet birth weight(P < 0.05);the addition of 0.40% leucine in the late gestation sow diets had an increased trend for survival rate of weaning piglets and litter weight at weaning(P < 0.10);supplementing with 0.40%,0.80% and 1.20% leucine in the late gestation sow diets had no effect on litter size,number born alive,still birth and mummified piglets,number born healthy,number born weak,number of weaning piglets and litter birth weight(P > 0.10).In addition,the addition of 0.40% and 0.80% leucine significantly reduced the weaning-estrus interval(P < 0.01).(2)Milk composition: Sows supplemented with 0.40% leucine in the late gestation diet significantly increased the content of milk fat on the 7th day(P < 0.05),and the milk fat content on the 14 th day of the sow had an increase trend(P < 0.10).(3)Organ index: Compared with the CON group,the addition of 0.40% leucine in the late gestation diet significantly increased the relative weight of small intestine(P < 0.05).(4)Amino acid composition: Supplementation of 0.40%,0.80% and 1.20% leucine resulted in higher plasma leucine concentration in farrowing sows(P < 0.05).Compared with the CON and 0.40% LEU group,supplementation of 0.80% and 1.20% leucine into sow diet resulted in lower valine and isoleucine in farrowing sows plasma(P < 0.05).Compared with the 0.80% LEU group,supplementation of 1.20% leucine into sow diet resulted in lower valine and isoleucine in farrowing sows plasma(P < 0.05).Supplementation of 0.40%,0.80% and 1.20% leucine into sow diet resulted in higher plasma concentration of leucine but lower valine and isoleucine compared to CON in the newborn piglets plasma(P < 0.05).Compared with the 0.40% LEU group,supplementation of 0.80% and 1.20% leucine into sow diet resulted in lower valine in the newborn piglets plasma(P < 0.05).Compared with the 0.40% and 0.80% LEU groups,supplementation of 1.20% leucine into sow diet resulted in lower isoleucine in the newborn piglets plasma(P < 0.05).Compared with the 0.80% LEU group,supplementation of 1.20% leucine into sow diet resulted in lower leucine in the newborn piglets plasma(P < 0.05).(5)Hormone: The addition of 0.40%,0.80% and 1.20% leucine in the late gestation diet had no effect on insulin,leptin,growth hormone,glucagon and IGF-I in plasma of sows before farrowing,newborn piglets and umbilical cord blood(P > 0.10).(6)Amino acid transporters: Compared with the CON group,supplementing with 0.40% leucine in the late gestation sow diets increased the expressions of LAT1,SNAT1,SNAT2,4F2 hc and rBAT proteins in placenta,piglet duodenum,jejunum,ileum and longissimus dorsi muscle(P < 0.05).The addition of 0.80% leucine significantly increased the expressions of SNAT1 and SNAT2 in placenta,LAT1,SNAT1,SNAT2,4F2 hc and rBAT in piglet longissimus dorsi muscle,duodenum and jejunum,4F2 hc and rBAT proteins in piglet ileum(P < 0.05).The addition of 1.20% leucine significantly increased the expressions of rBAT and SNAT1 in placenta,rBAT in piglet ileum,4F2 hc in piglet duodenum,jejunum and ileum,4F2 hc,LAT1,SNAT1,rBAT and SNAT2 protein in piglet longissimus dorsi muscle(P < 0.05),significantly reduced the expressions of LAT1 in duodenum,LAT1,SNAT1 and SNAT2 proteins in jejunum and ileum(P < 0.05).(7)mTOR signaling pathway: Compared with the CON group,supplementing with 0.40%,0.80% and 1.20% leucine in the late gestation sow diets significantly increased the expressions of p-mTOR,p-4E-BP1,and p-S6K1 in longissimus dorsi muscle of piglets(P < 0.05).The addition of 0.40% and 0.80% leucine significantly increased the expressions of p-S6 in piglet longissimus dorsi muscle(P < 0.05).In conclusion,supplementing with 0.40~0.80% leucine in the late gestation sow diets improved the mean piglet birth weight,growth performance of weaned piglets,and sows milk composition,enhanced the expressions of newborn piglets intestinal amino acid transporter proteins and maternal placenta,and promoted the maternal-fetal nutrient transport efficiency,increased the expression levels of mTOR signal pathway-related protein in the longissimus dorsi muscle of newborn piglets,thus promoted fetal intrauterine development and enhanced the protein deposition in fetal pigs. |
