GENETIC AND ENVIRONMENTAL EFFECTS ON THE GROWTH RATE OF YANKASA LAMBS
GENETIC AND ENVIRONMENTAL EFFECTS ON THE GROWTH RATE OF YANKASA LAMBS
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Date
1986-11
Authors
WAHEED, AKINOLA HASSAN
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Abstract
Lambs of Yankasa sheep were evaluated for effects of
genetic and environmental factors on their body weights at
birth, 3,6,9 and 12 months of age. The lambs were born between
1981 and 1985 in an on-going accelerated lambing programme at
National Animal Production Research Institute (NAPRl),
Nigeria,
Type of birth significantly affected weights from birth to
12 months of age. Lambs born as singles were consistently
heavier at all stages with the difference being most pronounced
at weaning. Ram lambs were 0.22kg and 4.88kg heavier than ewe
lambs at birth and 12 months of age, respectively. The effect
of parity of ewe on lamb growth was significant at birth, 3 and
6 months of age. Lambs born during the rainy season had higher
mean weights at birth and weaning. The order was however reversed
at 6 months with lambs born during the dry season being heavier,
though the difference was not significant. Effect of season was
therefore significant at birth, 3 and 12 months of age only.
Lambs born in 1981 had the heaviest mean weights from birth to
6 months of age. The superiority of the lambs sired by the fourth
sire-group was maintained from weaning to one year.
Additive adjustment of lamb weights for the identified
environmental factors was prefered to multiplicative adjustments
because of larger reduction of error variances associated with
these factors.
Estimates of repeatability for weights were 0.14,
0.06, 0.19, 0.28 and 0.17 at birth, 3, 6, 9 and 12 months
respectively. Corresponding estimates for heritability
were 0,22, 1.14, 1.06, 0.94 and C.51. Genetic and phenotypic
correlations between birth weight and weaning weight, weaning
weight and 6-month weight, and weaning weight and 9-month
weight were found to be 0.10 and 0.17, 0.27 and 0.43, and
0.17 and 0.39, respectively.
It was concluded that under this environment, it would
be necessary to adjust body weights of growing lambs for the
effects of type of birth, sex of lambs, parity of ewe,
season and year of lambing
Description
A Thesis
Submitted to the Postgraduate School, Ahmadu Bello
University, in partial fulfillment of the requirements
for the degree of Master of Science in Animal Breeding,
Department of Animal Science
Faculty of Agriculture
Ahmadu Bello University
Zaria.
November, 1987
Keywords
GENETIC,, ENVIRONMENTAL,, GROWTH RATE,, YANKASA LAMBS