| The Meishan pig is famous for its high prolificacy,the factors responsible for the high prolificacy has been studied for a long time.The Meishan pig originates in China's Yangtze River basin,in the long process of feeding,green forage seems to display a specific action within the Meishan pig to modulate reproductive performance.This study was conducted to evaluate the effects of green forage on the onset of puberty and ovarian follicle development in Meishan gilts.Twenty prepubertal Meishan gilts,with an initial body weight 25.14±0.18 kg,were used in this study.Gilts were randomly allocated to one of two groups with 10 repeats for each group:control(CON)and green forage group(GF).The rearing periods were divided into three phases:based on the body weight.The CON group gilts fed 1.08kg,1.30kg,1.64kg of basal diets(corn-soybean meal diets)per day at stage 1(20-30kg),stage 2(30-40kg)and stage 3(40kg to slaughter),respectively.The GF group gilts were fed 1.2kg(Chinese cabbage),1.8kg(Chinese cabbage),2.0kg(sweet potato vine)of green forage,and 1.02kg,1.21kg,1.46kg of basal diets at stage 1(20-30kg),stage 2(30-40kg)and stage 3(40kg to slaughter),respectively.Nutrient digestibility trial was applied when the body weight of gilts at 40 kg.After weighing,gilts were slaughtered at Day 19 in the third estrus.The digesta,serum,follicular fluid and tissue samples were collected to investigate the effects of green forage supplementation on short-chain fatty acids(SCFA),hormone concentration and antioxidant capacity.The relative expression levels of antioxidant genes and hormone receptor genes in granulosa cells were determined by RT-PCR.The microbial composition of colonic digesta were determined using the 16S rDNA method.These results showed:1)The age at puberty of gilts fed green forage tended to be delayed than those in thecontrol group(P=0.08;P=0.09),while the body weight of puberty tended to be increased in the GF,but there was no significant difference in the two estrus cycles(P>0.05);The results of nutrient digestibility trial were shown that none of the dry matter(DM),energy,crude protein(CP),ether extract(EE),crude fiber(CF)digestibility showed significant difference between the two groups(P>0.05).2)The slaughter weight of gilts in the GF group tended to be increased than those in the CON group(P=0.07).The stomach index(P<0.01),jejunum wall thickness(P<0.05)and ileum wall thickness(P<0.01)were increased in the GF group,while the relative weight of small intestine and large intestine had no significant difference between the two groups(P>0.05);Results in body composition showed that loin area(P<0.05)and bone ratio(P<0.05)were increased,but backfat thickness(P=0.06),carcass yield(P<0.05)and subcutaneous adipose tissue(SCAT,P<0.05)were decreased in the GF group,compared with those in the CON group.The carcass weight,carcass length and lean meat had no significant difference between the two groups(P>0.05).3)Butyric acid concentration in colonic content(P<0.05),acetate concentration in caecal content(P<0.05)and colonic content(P<0.05)were both significantly increased,meanwhile,butyric acid concentration in caecal content tended(P=0.07)to be increased in the GF group than those in the CON group,while the propionic acid in caecal content and colonic content had no significant difference between the two groups(P>0.05).4)The development of the ovary that was characterized by an increase in the ovarian relative weight(P=0.05),the number of the large follicles(>5mm,P<0.05)and corpora lutea(P=0.06)in the GF group,but the number of medium follicles(?3mm,<5mm)and small follicles(<3mm)had no significant difference between the two groups(P>0.05).5)The concentration of insulin-like growth factor-1(IGF-1)in follicular fluid tended to be increased in gilts fed green forage(P=0.05),while there's no difference of estradiol(E2)between the two groups in plasma and follicular fluid(P>0.05).The result of RT-PCR showed the relative expression of luteinizing hormone receptor(LHR)mRNA in the granulosa cells from large follicle(>5mm)of gilts fed green forage were increased(P<0.05),while the follicle-stimulating hormone receptor(FSHR)and estrogen receptor-a(ERa)mRNA expression had no significant difference between the two groups(P>0.05).6)Gilts in the GF group had significantly higher serum concentrations of T-SOD(P<0.05)and lower serum concentrations of MDA(P<0.05)than those in the CON group,but there was no difference of total antioxidative capability(T-AOC),glutathione peroxidase(GPx)and vitamin E(VE).The result of RT-PCR showed the expression of superoxide dismutase-1(SOD1)mRNA in the granulosa cells from large follicle(>5mm)of gilts fed green forage were increased(P<0.05),but the GPx and superoxide dismutase-2(SOD2)mRNA expression had no significant difference between the two groups(P>0.05).7)Microbes in digesta:according to the Observed species index,the sample sequencing basically covers all species of the samples.Though the principal component analysis,the samples in the GF were separated from the CON by a distance,and a small degree of discretization was in the GF,indicating the green forage played a regulatory role in the gut microbiota.Differences in gut microbiota between the two groups:compared with the CON group,the abundance of family Eubacteriaceae(P<0.05),family Lactobacillaceae(P=0.066),genus Lachnospira(P<0.05),genus Anaerovibrio(P<0.05),genus Cellvibrio(P<0.05),species Lactobacillus reuteri(P=0.066)and species Lactobacillus mucosae(P<0.05)were higher,while family Peptococcaceae was reduced(P<0.05)in the GF group.The above results show that feeding green forage led to an increase in the intestinal weight,SCFA in the digesta and regulation of gut microbiota,so as to change in the body composition and delay the onset of puberty.Also,feeding green forage could improve the development of ovary(especially to increase the ovarian weight,the number of large follicles and IGF-1 concentration)and antioxidant capacity to promote the reproductive performance of Meishan gilts. |
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