| Reproductive performance is a key trait for goat breeding. Improving the goat litter size plays an important role on increasing the productive yields of farmers and the economic benefit of goat husbandry. Becanse of the restrictions of low heritability and negative maternal effects, there is no obvious genetic improvement on phenotypic traits, such as litter size ovulation number. Placental efficiency (PE) was defined as the ratio of total birth weight to placental weight, the concept was given by Wilson in his research on swine in 1999. Many studies on swine, sheep have shown that there was a signifficant positive correlation between the litter number and PE. So it was possible to increase litter size by selecting PE. In molecular level, osteopontin (OPN) is expressed on the maternal-fetal interface continuously and participate in reproductive progress such as pertilization, blastocyst implantation, placentation and embryo maturity. Because of its important role in the regulation of uterine-placenta micro-environment, the function of OPN gene has been paid more and more attention to blastocyst implantion and embryonic development. In additon, previous researches on swine and cattle have shown that OPN gene was the one of the candidate genes that influencing reproduction performance. The aim of our study is to investagate the genetic diversity of OPN gene and its correlation with PE and the reproductive performance in goat.This study was divided into two parts. Fistly, to investigate the correlation of PE, placental traits with reproductive performance in goat.The main methods were as follows:(1) Under similar raising condition, a total of 30 individuals of Lezhi Black goat were selected, the data such as does parities, litter weight and litter size were recorded. (2) Placentas were collected immediately after delivery (approximately 2h after the birth of the last lamb), the placental traits such as placental weight, cotyledons number and cotyledons weight were measured. (3) The relationships between placental traits and reproduction traits were analyzed. Secondly, to study the relation of OPN gene polymorphism with PE and the reproductive performance in goat.The main methods were as follows:(1) The SNP sites of 5'promoter (P1 Locus), exon6 (P2 Locus) and exon7 (P3 Locus) of OPN gene of 70 individuals were detected by PCR-SSCP methods, respectively. (2) The correlation of the 3 loci of OPN gene and the placental traits, reproduction traits were analyzed by SPSS 18.0 for windows. The results showed that:1. The average litter weight of Lezhi Black goat was 4682.40±3022.91 g (n=30), the average PE was 10.45±3.51 (n=30), PE was very significantly difference among three groups (P<0.01). Compared with low PE group, high PE group was higher in the litter size (2.56±0.44 vs 1.30±0.15, P < 0.05). First parity does gained few number of litters (1.33±0.48 vs 2.53±0.30) and less weight in lamb birth weigh (2261.60±106.85 g vs 2636.27±119.57 g), placenta weight (288.87±32.35 g vs 622.33±57.64 g), cotyledon weight (140.53±18.11 g vs 262.80±30.38 g)) and average cotyledon weight (1.14±0.09 g vs2.35±0.21 g) than those of multiparous does (P< 0.05 orP< 0.01). Litter size clearly affects the placental traits. Placental weight, cotyledon weight and average cotyledon weight became increasingly efficient as litter size increased (P< 0.05), but cotyledon density declined(P< 0.05). Litter size was positively correlated with PE, placental weight, cotyledon weight and average cotyledon weight (r=0.439; r=0.845; r=0.831; r=0.603, P< 0.05 orP< 0.01), but was negatively correlated with cotyledon density(r=-0.539, P< 0.05). PE was also positively correlated with cotyledon weight, average cotyledon, was negatively correlated with cotyledon density. There was a negative correlation between average cotyledon weight and cotyledon density.2. Three different loci of OPN gene were demonstrated polymorphism in the tested population.The genotypes were nominated AA and AB, and the PIC were 0.365.0.064.0.360 respectively. The frequencies of the 3 loci were analyzed usedχ2-test. The results revealed that at the P2 locus the does were with Hardy-Weinbery equilibrium, but at the Pl and P3 locus, the does were hightly significantly biased from equilibrium law (P< 0.01).The association of variations of OPN gene with plancental traits reproduction traits were analyzed. The results were showed as follows:The genotype of PI locus was associated with litter size, with a trend of AA>AB (P< 0.05), but was no relationship with placental traits. There were no significant difference on placental traits and reproduction traits (P> 0.05) on P2 locus, indicating that the variation of this locus has little effect on reproductive process. The genotype of P3 locus was significant difference on placental weight, cotyledon weight and average cotyledon weight, with a trend of AA> AB. The does with homozygotic type A A had 1.97 kids (P< 0.01) more than those with heterozygous type AB in goat.The following conclusions are drawn:1.There is significant correlation between pacental efficiency and litter number in goat.2.The exon7 of OPWgene may be a candidate gene that controls high fecundity of goat. |
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