Association of Growth Differentiation Factor 9 GDF9 Gene With Some Productive and Reproductive Traits of Some Sudanese Desert Sheep Ecotypes

Abstract

The present study was carried out during March and May 2015 at the home-land of the studied desert sheep ecotypes, including Khartoum and Gezira states for (Ashgar and Dubasi sheep), Sinar and Blue Nile states for (Watish and Dubasi sheep) and River Nile state (Ashgar sheep). This study aims to investigate some productive and reproductive traits of some Sudanese desert sheep in different areas in the Sudan, determine the association between live weight and body measurements of Ashgar, Dubasi and Watish sheep using different mathematical models and analyze GDF9 variability and test identified variants for association with litter size among Sudanese desert sheep ecotypes. A total of two hundred and twenty-five head of three sheep ecotypes were randomly selected [80 Ashgar (male=21, female=59), 72 Dubasi (male=22, female=50) and 73 Watish (male=23, female=50)] and according to sex [rams (n=66) and ewes (n=159)] to find out the correlation between live body weight and body measurements using different mathematical models (linear, quadratic, cubic, compound, power and S). The obtained data were tested for significance using analysis of variance ANOVA followed by least significant difference (LSD) test. Also, Independent samples T. test was used and Pearson’s correlation, simple regression analysis was fitted. The live body weight and body measurements were significantly (P<0.05) affected by sheep ecotypes and sex except shank circumference (SC) and thigh circumference (TC) for sheep ecotype and chest depth (CD), rump width (RW), head width (HW) and thigh circumference for sheep sex. The live body weight was significantly (P<0.01) correlated with the majority of body measurements, the highest correlation coefficient in the studied sheep VI ecotype was between the live body weight and heart girth (0.826), followed by live body weight with wither height (0.756) and body length (0.749) respectively. R2 values of the studied ecotypes showed that heart girth was the highest association (P<0.01) with live body weight, followed by wither height and body length. The study concluded that sheep ecotypes and sex significantly affect body weight, Watish had the highest body weight while Dubasi had the lowest. Twenty eight DNA samples were selected (ten from Ashgar and Dubasi and eight from Watish). For each ecotype, 50% of the samples were selected from the single lamb group and the other 50% from the more than a single lamb group these ecotypes with litter size records for at least two litters were sampled. The complete GDF9 exon 2 was sequenced in the 28 samples. An additional variant in exon 1 (c260G>A) was genotyped by restriction-length polymorphism analysis in 97 DNA samples. Differences in genotype and allele frequencies of polymorphic positions between two groups differing in litter size (only a single lamb versus more than a single lamb) were tested for significance using Fisher's exact test. GDF9 exon 2 variants c.477G>A and c.721G>A and exon 1 variant c.260G>A were found to be polymorphic in all three sheep ecotypes. Exon 2 variants c.471C>T and c.978 A>G were polymorphic in at least one ecotype. No significant associations were observed between allele and genotype frequencies of identified variants and litter size. This suggests that GDF9 variants influencing ovulation are absent in these Sudanese sheep ecotypes, and therefore cannot be used to increase litter size within this population of sheep.