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20122
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Subject: Animal Genetics and Breeding × End date: 2012 × Start date: 2012 × Thesis Type: M.V.Sc. ×
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    ThesisItemOpen Access
    MOLECULAR CHARACTERIZATION OF NELLORE SHEEP USING MICROSATELLITES
    (SRI VENKATESWARA VETERINARY UNIVERSITY , TIRUPATI – 517502. (A.P.) INDIA, 2012-12) VANI, S; Punya Kumari, B (Major); Gnana Prakash; Rao, V H
    ABSTRACT: Nellore, tallest breed of indigenous sheep is the predominant breed present in Andhra Pradesh. The animals true to the breed are mainly found in Nellore and Prakasam districts of Andhra Pradesh. Nellore is a meat type breed known for heat tolerance, disease resistance and thrives well in harsh conditions. To form the basis for evolving further strategies to improve animal production, the assessment of the genetic and production potential of our livestock is very much necessary. The present study was carried out to characterise Nellore sheep at molecular level to understand the genetic constitution of population which will be helpful to breeders to formulate breeding strategy for the improvement of the breed. The characterisation was done by ten microsatellite markers recommended by FAO for population diversity studies in sheep. DNA was isolated from blood samples by phenol-chloroform method and microsatellites were amplified by PCR reaction. The PCR products were resolved using agarose gel electrophorosis. The genotypes were scored and the number, size, frequency of alleles were calculated using POPGENE software. In the sampled population for the ten marker loci under investigation a total of 75 alleles were observed. The number of alleles at each locus varied from a minimum of four to a maximum of ten with a mean of 7.5 alleles across all loci. Of the 75 alleles observed, four alleles at loci OarVH72, seven alleles at BM1314, BM6526, OarFCB48 and OarHH41were found, whereas, eight alleles were detected at loci BM8125, CSSM47. The number of alleles at loci BM757 were nine and ten at OarFCB128. The most frequent allele number was seven. Of the ten loci studied, the effective number of alleles ranged from 3.2125 (OarVH72) to 5.7645 (OarCP34) with the mean number of 4.7202 across all loci. PIC values for Nellore sheep ranged from 0.637 (CSSM47) to 0.8157 (OarCP34) with mean PIC value of 0.7528. Based on the PIC values, it could be inferred that all the markers used in the present study showed values more than 0.5 indicating their importance in molecular characterization and genetic diversity studies. All the loci under investigation showed significant Chi-Square values, suggesting departure from Hardy-Weinberg Equilibrium proportions. The observed heterozygosity values varied from 0.2368 (OarVH72) to 0.833 (BM8125) with a mean value of 0.497 and the expected heterozygosity values varied from 0.6887 (OarVH72) to 0.8265 (OarCP34) with a mean value of 0.7865. Two out of ten loci revealed negative FIS indicating an absence of inbreeding in those loci while the remaining loci revealed positive FIS values ranging from 0.0831 (OarFCB128) to 0.4224 (OarCP34). The mean FIS value observed over all the loci was 0.1889 indicating the deficiency of heterozygotes.
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    ThesisItemOpen Access
    GENETIC STUDIES ON THE PERFORMANCE OF NELLORE SHEEP
    (Sri Venkateswara Veterinary University, TIRUPATI – 517 502,A.P, 2012-12) RANI, MANNE; EKAMBARAM, B (Major); PUNYA KUMARI, B; RAVINDRA REDDY, Y
    ABSTRACT : Data on 1350 Nellore Jodipi sheep of 2, 4, 6 and 8-teeth age, reared under field conditions in 12 mandals of Chittoor district of Andhra Pradesh was utilized for the present study. Data recorded on body weights at different ages on the sheep maintained at the Network Project on Nellore Sheep Improvement, Livestock Research Station Palamaner, Chittoor district was also utilized for the present study. Analysis of data under field conditions revealed that division and sex had significant (P≤0.01) effect on body weights and biometrical measurements at majority of ages studied and the non-genetic factors like Period, Season and Sex shown significant (P≤0.01) effect on body weights at all ages studied on farm data. The overall least squares means for body weight at 2, 4, 6 and 8-teeth age were 35.26 ± 0.23, 38.45 ± 0.13, 39.53 ± 0.32 and 40.06 ± 0.33 kg, respectively. While, the overall least-squares means for body weights at birth, 3, 6, 9 and 12 months of ages were 2.87 ± 0.01, 12.96 ± 0.08, 17.15 ± 0.13, 20.99 ± 019 and 25.38 ± 0.26 kg, respectively. The lambs born during off season shown superiority in body weights over main season lambs at all ages except at 9-months. The overall least-squares means for average daily gains during 0 to 3, 3 to 6, 6 to 9 and 9 to 12 months of ages were 112, 48, 42 and 49 gm, respectively. Phenotypic correlations among body weights and biometrical measurements were also studied. The coefficients of correlations between body weight with the height at withers, chest girth, paunch girth hip width and body length were positive and high in magnitude in both males and females in majority of the age groups studied. Step-down regression equations were fitted to predict the body weight based on biometrical measurements at different ages and the results revealed that the height at withers, chest girth, paunch girth, hip width and body length have contributed significantly to the expression of body weights at the majority of the ages studied. High Coefficient of determination (R2 values) were observed in males at 6 and 8-teeth age (88.00) males and in females at 2-teeth (50.00) age. The data adjusted for non-genetic factors was utilized to study the genetic parameters. The heritability estimates were ranged from low to moderate. Body weights at six months of age was medium heritable (0.29 ± 0.08), while, 12 months of age was low heritable (0.062 ± 0.10). Heritability estimates for body weights at different ages tended to increase with increasing age from birth to 6-months body weight and then declined in the present study. The 6-months body weights can be used to select the animals for genetic improvement programmes. The average daily gains during 3 to 6 months was medium heritable (0.340 ± 0.08). The heritability estimates for average daily gains at different ages tended to increase with increasing age from birth to 6-months average daily gains and then decreased. The average daily gains between 3 to 6 months age can be used as a selection criterion for the improvement of body weights. The genetic correlation coefficients of weaning weight (3m) with 6, 9 and 12 months body weights and average daily gains during 0 to 3, 6 to 9 and 9 to 12 months of age were positive. The genetic correlations between 6-months body weight with later ages were strongly correlated. The phenotypic correlation coefficients of 6 months body weight with 9 and 12 months body weights and average daily gains at all ages were positive and significant. The body weight at 6 months was highly correlated with 9 and 12 months body weights at genetic and phenotypic level also. A greater portion of variation in body weights due to environmental factors was also observed, however, the genetic correlation suggested that selection can be practiced effectively at subsequent ages on the basis of body weights at 6 months of age to improve the body weights.