ABSTRACT
Twenty-five
intensively managed mature West African Dwarf goats were used for the
experiment comprising 20 Does (dams) and 5 bucks (sires). The goats were
classified into 5 mating pens of 4 Does (dams) and one buck (sire) randomly
assigned per pen. Fresh water and forage were provided ad libitum in
addition to 1kg concentrates Cajanus cajan to each animal per day. Data
were collected on weights at birth and weaning; litter size and linear
body measurements. Body weight gain was calculated. The data were subjected to
analysis of variance in completely randomized design using the statistical
package of social science (SPSS) computer package. The Paternal Half-sib
Analysis model was used to estimate sire component of variance from which the
additive genetic variance and heritability were calculated. The descriptive
statistics (mean ±S.E) and Coefficient of Variation for birth weight, litter
size, body weight gain and body weight showed that birth weight of the
offspring were significantly different (P<0.05) between sires. The weaning
weight of offspring of different sire groups indicated non-significant
differences (P>0.05). Body weight gain of sires group recorded significant
differences (P<0.05). The effect of sex of the animal body weight, body
weight gain, body length, arm length and height at wither showed that male
progenies were higher than females; while the effect of season of birth
indicated that kids born in dry season had higher daily weight gain
(44.16±3.11g) than those born in wet season (42.32±3.74g). The heritability
estimates for birth weight, litter size and weaning weight were low, moderate
and high (0.15, 0.22 and 0.88), respectively. The estimates of heritability for
body length at birth were moderate, while at 6 months of age the heritability
was high (0.95) and this indicates high potence for genetic improvement.
Linear body measurement traits
(body length, arm length, and height at wither) recorded high heritability
values. Phenotypic, genotypic and environmental correlations between pairs of
parameters in West African Dwarf goat traits ranged from -0.01 to 0.99.
CHAPTER 1
INTRODUCTION
The
2006 national census gave the population of Nigeria as 144 million people
(National Population Commission, 2006). With the rate of population growth and
rapid loss of indigenous livestock species coupled with rising costs of production,
the present gap in the supply of animal protein is bound to widen. To bridge
the animal protein demand and supply gap, the Nigeria government since 1970s to
date, has attempted to improve indigenous breed of livestock by importing
exotic breeds. These efforts have failed principally because the exotic breeds
could not adapt to the tropical Nigerian environment as the challenges of
tropical pests and diseases were unbearable to them. Locally adapted breeds
(indigenous breeds) are better able to survive and produce valuable products in
low input and variable environments (AGRI, 2002).
Maijala
(1983) reported that genetic improvement is currently being conferred on
indigenous breeds of goats because they have long been adapted to extreme harsh
environmental conditions of nutrition, climate and disease. They might be more
productive in their own environment than exotic breeds. They can also be
valuable experimental animals in fundamental research and a potential store of
unique genes, which may be useful especially when environment concerns
necessitate changes in production system (Salako and Ngere, 2002). The
indigenous small ruminant populations in Nigeria comprising sheep and goats are
important genetic sources because of their adaptation characteristic such as
hardiness to the stressful tropical environment and trypano-tolerance (Salako,
2004). Of the several breeds of goats in the world, the predominant breed in
the humid tropics is the West African Dwarf goats. The majority of these are
bred under the traditional management and their contribution to the total
supply of meat in the region is enormous.
The
ability of farmers and buyers to relate the live animal measurements to growth
characteristics is essential for optimum production and value-based trading
system. This ability will also adequately reward livestock farmers rather than
the middlemen that tend to gain more profit in livestock production business
especially in developing countries (Afolayan et al., 2006). A study of
linear body measurements on most farms in the tropics is important because most
farmers lack weighing scales and the education to understand their
manipulations (Gerald, 1994). Linear body measurements can be used as a way of
estimating weight and market value in terms of cost of the animals (Gerald,
1994).
1.1 Objectives of the Study
The general objective of this study was to determine the genetic
parameters of growth and reproductive traits of West African Dwarf (WAD) goats
reared in the humid tropics.
The Specific Objectives are:
· To evaluate the West African Dwarf (WAD) goats for
growth performance.
· To determine the effect of sex and season on
performance traits of West African Dwarf goat.
· To determine the heritability of litter size, growth
and body measurements in West African Dwarf (WAD) goat.
· To determine the genetic, phenotypic and
environmental correlations between body weight and body measurements at various
ages.
1.2 Problem Statement
Animal
agriculture provides the animal protein needs of Nigeria (Ogbu, 2010). This is
an enormous responsibility. The British Medical Association recommends a
minimum animal protein intake of 34g per caput per day (Okunenye, 2002).
According to Ogbu (2010), the average animal protein intake per caput per day in
Nigeria was 7.6g .The Central Bank of Nigeria (2000) while analyzing the
economic sub-sectors noted that the Gross domestic product (GDP) has been on a
downward trend. The nature of GDP reflects the standard of living of the
citizens; it means that the standard of living of Nigerians has been on the
decline. This implies that the animal protein intake of the average Nigerian
has to fall far below the recommended levels. To make up for this decline,
Nigeria must import animal milk and meat products from other countries.
Ironically, in spite of the enormous number of indigenous livestock resources,
Nigeria remains a net importer of livestock products since the 1980s (Okunenye,
2002).
There
has been a total neglect of indigenous species of livestock, as a result they
have remained undeveloped. It is, therefore, imperative that efforts be
channeled towards the improvement of West African Dwarf goat which is
indigenous to the tropics. Improvement in the growth traits and reproductive
performances of the West African Dwarf goat will increase its carcass yield and
enhance its acceptance as a meat animal and as well increase farmer’s income.....
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