GENETIC ANALYSIS OF GROWTH AND SOME REPRODUCTIVE TRAITS OF SHEEP OF NORTHERN NIGERIA AND THEIR CROSSES
GENETIC ANALYSIS OF GROWTH AND SOME REPRODUCTIVE TRAITS OF SHEEP OF NORTHERN NIGERIA AND THEIR CROSSES
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Date
2012-09
Authors
IYIOLA-TUNJI, ADETUNJI OROYE
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Abstract
A total of 65 Yankasa, 23 Uda and 16 Balami ewes were mated to 4 Yankasa, 3 Uda
and 3 Balami rams in a diallel breeding pattern to produce 192 lambs that were used to
genetically analyse growth and some reproductive traits. Weight records and linear
body measurements were obtained from lambs at birth, 90-Day (weaning weight), 180-
Day and 360-Day (yearling weight). Blood samples (5 ml) were collected from all the
ewes and rams used for the study. The blood samples were subjected to cellulose acetate
electrophoresis to obtain distinct bands of haemoglobin genotypes (AA, BB and AB).
Daily growth of the lambs was calculated using average daily gain (ADG) and relative
growth rate (RGR). The haemoglobin type HbAB was the most predominant in the
studied population and allele A of the haemoglobin type was the most numerous. Breed
and haemoglobin types had significant (P<0.05) effect on lamb weight. Crossbred lambs
of Yankasa rams and Uda ewes (YK X UD) were the heaviest at birth. Pure Balami
lambs were superior to all other lamb genotypes in body weight at 90 and 180-Day. The
heaviest 360-Day weight (18.73±1.53 kg) was recorded for lambs of HbBB. The ADG
and RGR of lambs were affected (P<0.05) by dam’s haemoglobin type, lamb genotype,
type of birth and sex of lambs. Yankasa rams and ewes produced lambs with the
shortest gestation lengths (151.84±0.23 days and 151.85±0.20 days, respectively). The
highest litter size was recorded in UD X YK or BL X UD crosses. All the lamb
genotypes had very high mortality from 180 to 360 days. However, there was no
mortality recorded for BL X BL lambs from birth to 180 days. The HbBB genotype
however had the highest percent mortality from 90 to 180-Day. The coefficients of
phenotypic correlations between body weight and linear body measurements increased
in proportion as Yankasa lambs grew from birth to 360-Day.Heritability estimates for
body weight and some linear body measurements for Yankasa lambs were high at 180-
Day (0.765±0.514) and 360-Day(0.805±0.961) indicating low effect of the environment
on the traits in the studied population. Linear body measurements that considered
volume of animal in terms of circumference (chest girth and loin girth) and body length
(back length, neck length and height at wither) tended to give better accuracy of
prediction of liveweight of lambs. Balami sheep (used as either sire or dam) expressed
its superior genetic potential in terms of faster growth rate than Uda and Yankasa in the
Northern Guinea Savannah agro-ecological zone. Selection for improved growth traits
in the population of Yankasa sheep should be based on individual records of the lambs
at 180-Day because of high heritability for 180-Day body weight of Yankasa lambs.
Weighing chart and bands should be produced for all the sheep breeds considered on the
basis of prediction equations.
Description
A THESIS SUBMITTED TO POSTGRADUATE SCHOOL, AHMADU BELLO UNIVERSITY, ZARIA. IN PARTIAL FULFILMENT FOR THE AWARD OF MASTERS OF SCIENCE IN THE DEPARTMENT OF ANIMAL SCIENCE
AHMADU BELLO UNIVERSITY, ZARIA
NIGERIA
SEPTEMBER 2012
Keywords
GENETIC,, ANALYSIS,, REPRODUCTIVE,, NORTHERN,, CROSSES