A STUDY ON MORPHOLOGICAL AND GENETIC VARIATION IN NELLORE PALLA SHEEP
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Date
2017-01
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SRI VENKATESWARA VETERINARY UNIVERSITY TIRUPATI - 517 502. (A.P.) INDIA
Abstract
ABSTRACT:
The southern peninsular region of India is home to fourteen descriptive mutton
breeds, of which Nellore is the country's tallest sheep, predominantly distributed in
areas of Nellore and Prakasam districts of Andhra Pradesh. Based on coat colour
three varieties were seen: Jodipi, Brown (Dora) and Palla. Nellore Jodipi is
predominant in its population followed by Brown and Palla. Nellore palla sheep are
confined to only certain areas of Nellore district and very scanty information is
available on the performance of the breed. The population of Nellore Palla is under
threat (<1500). Hence, genetic and phenotypic evaluation of the breed is important not
only from conservation point of view, but also to assess the level of inbreeding in the
population.
The present study was carried out to figure out productive and reproductive
performance in Nellore Palla sheep under field conditions and also to assess the
genetic structure of Nellore Palla sheep at molecular level using twenty four
microsatellite markers recommended by ISAG/FAO for genetic diversity studies in
sheep. A total of 347 sheep of different age groups were used to study the
morphometric measurements of Nellore palla sheep and 50 blood samples from
unrelated sheep flocks were used for molecular studies.
The overall least squares means of body weights (kg), height at withers, chest
girth, paunch girth and body length were 35.18 ± 0.27, 78.47 ± 1.55, 80.82 ± 0.66,
80.93 ± 1.37 and 69.90 ± 0.83 at 2- teeth age, 39.65 ± 0.33, 82.45 ± 0.98, 84.57 ±
0.72, 84.11 ± 1.34 and 72.23 ± 1.02 at 4- teeth age, 41.18 ± 0.56, 83.63 ± 0.64, 86.32
± 0.74, 85.88 ± 1.23 and 74.55 ± 0.81 at 6- teeth age, 45.00 ± 0.46, 85.22 ± 1.97,
87.17 ± 0.58, 86.14 ± 0.52 and 76.17 ± 0.33 at 8- teeth of age respectively. Villages
and sex showed a significant (p<0.01) effect at all ages and the parameters studied.
The overall least squares means of age at first mating in males, age at first
mating in females, age at first lambing, tupping and lambing percentages were 598.03
± 3.02 days, 361.54 ± 1.09 days, 509.32 ± 1.00 days, 81.06 ± 1.61 and 73.37 ± 1.53
percent, respectively.
The coefficient of correlations between body weights with the height at
withers, chest girth, paunch girth and body length varied from 0.58(PG) to 1.00(CG)
in males and 0.16(PG) to 0.69(HW) in females. A perfect phonotypic correlation
(1.00) was observed for body weights and height at withers at in 8- teeth age males
and for body weights and chest girth for males at 6- teeth age. All the correlations
were positive and highly significant (p<0.01) in majority of the age groups studied.
The standard Phenol-Chloroform method was used for isolation of DNA from
50 blood samples. The quality and quantity of DNA was checked by agarose gel
electrophoresis and Nanodrop spectrophotometer, respectively. The allele frequencies,
observed number of alleles (Na), effective number of alleles (Ne), observed (Ho) and
expected (He) heterozygosity, within population inbreeding estimates (FIS) were
computed using POPGENE32 software.
A total of 189 alleles were found across the 24 microsatellite loci
studied. The number of alleles at each locus ranged from five (BM6506, CSSM31
and HUJ616) to a maximum of thirteen (BM827 and OARHH64) with a mean of 7.8
alleles across all loci. The allele sizes ranged from a minimum of 81 bp (OarJMP8) to
a maximum of 258 bp in MAF214, while, the allele frequencies ranged from a
minimum of 0.010 (BM827, INRA63, OarFCB48 and OarHH64) to a maximum of
0.40 (OarFCB128). The mean effective number of alleles was 6.6452 ± 0.3933 which
was less than the observed number of alleles and ranged from 3.4916 (CSSM31) to
11.574 (BM827).
The observed heterozygosity (Ho) and expected heterozygosity (He) ranged
from 0.00 (BM1314, BM6506, BM8125, HUJ616, OARCP20, OARFCB128,
OARJMP8) to 0.16 (OARHH64) and from 0.7208 (CSSM31) to 0.9228 (BM827)
with an overall value of 0.0626 ± 0.010 and 0.8361 ± 0.009, respectively.
All the twenty four microsatellite loci were found to be highly polymorphic
and the PIC values ranged from 0.6616 (CSSM31) to 0.9136 (BM827) with a mean of
0.8171. The FIS values were found positive and ranged from 0.8201 (OARHH64) to
1.000 (BM1314, BM6506, BM8125, HUJ616, OARCP20, OARFCB128,
OARJMP8). The mean FIS value across the twenty four loci observed was 0.9257.
The χ2 test revealed that all the twenty four loci deviated significantly from Hardy-
Weinberg Equilibrium.
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