ABSTRACT
The study was carried out to determine the x-chromatin
status of different breeds of rabbit and their crosses. The genotypes were
Newzealand (NZW) x Newzealand (NZW), Dutch Black (DTB) x Dutch Black (DTB),
(NZW) x DTB, and DTB x NZW. One hundred and sixty-nine offsprings from the
mating were screened. Blood samples were collected with heparin sample bottles
fortified with EDTA anti-coagulant via the ear veins and blood smears were made
on clean glass slides. They were stained with Geimsa, rinsed in distilled water
and air dried. With the aid of microscope, 200 polymorphonuclear neutrophils
were examined for the presence of drumstick appendages. The result revealed
that the females had the average x-chromatin status of 2.09%, 2.00%, 2.28% and
2.07% for NZW x NZW, DTB x DTB, NZW x DTB and DTB x NZW genotypes respectively
while the males had the average x-chromatin status of 0.00%, 0.05% 0.00% and
0.00% for NZW x NZW, DTB x DTB, NZW x DTB and DTB x NZW genotypes respectively.
These values were within the normal range of 2.00 – 12.00% for females and
0.00% - 2.00% for males. It was concluded that these animals were free from
x-chromatin related physiogenetic problems. The body weight measurement of the
rabbits at 4, 8, 12 and 16 weeks of age showed significant differences at
(p<0.05) across the genotypes. The linear body measurements of males and
female rabbits at 4, 8, 12, and 16 weeks of age showed significant differences
at (p<0.05) across the genotypes. From this experiment it could be concluded
that the Main crosses ((NZW) x DTB) and the Reciprocal crosses (DTB x NZW) came
out better since they explored the advantages of cross breeding and it is
advised that farmers should practice cross breeding of rabbits rather than
breeding pure lines.
CHAPTER
ONE
1.0 GENERAL
INTRODUCTION
1.1 INTRODUCTION
The total world production of
rabbit was estimated to range from 1,311,000 to 1,516,000 tonnes for the top 22
producer countries. From this figure, Italy had 300,000 tonnes, Russia 250,000
tonnes, France 150,000 tonnes, China 120,000 tonnes, Spain 100,000 tonnes,
Indonesia 50,000 tonnes, Nigeria 50,000, tonnes, United States 35,000 tonnes
and Germany 30,000 tonnes (WRP, 1990).
Rabbits are basically reared
for meat, fur and cool production (TNAU, 2008). Rabbit production is very
essential in improving animal protein intake in developing countries. This is
because rabbit is very prolific as determined by the number of kits born alive
at kindling and birth to weaning viability (Orunmuyi et al., 2006).
Alleviation of poverty,
attainment of food security and provision of adequate nutrition are some of the
millennium development goals that Nigeria has to meet. Rabbit farming can be
one effective objective that can be used not only in Nigeria but also in other
Africa countries (Cliford, 2009).
Advantages of rabbit farming
are enormous considering the fact that they can be fed with high forage, low
grain diet that is largely non-competitive with human food and they have high
feed conversion efficiency. Rabbits have the potential to being in constant
state of reproduction and can be mated within 24 hours of kindling. They have
high growth rate attaining market weight of about 2kg at 12 weeks of age.
Rabbit meat is a highly nutritious, tasty and excellent in quality. It is rich
is protein, low in fat, cholesterol and sodium and thus can be recommended for
cardiac patients (TNAU, 2008).
Cliford (2009) also summarized
in Africa Rural Connect that Rabbits are prolific in reproduction, have high
growth rate and therefore high turnover, required minimal space to keep and
meager resources to maintain since they can flourish on forages that are
disdained by humans.
The feeding habit of rabbit
offers no appreciable competition with man. This is because it can subsist on
green as basal diets. The combination of these characteristics is unique. In
addition to these, rabbits have a number of other characteristics that might be
advantages on subsistence farming system such as their small body size, short
generation interval with relatively short gestation period average of 30-31
days. The daily weight gain is high in proportion to the body weight which
gives them a rapid growth rate and sexual maturity is early. These factors
result in rabbit reaching the weight of a sexually mature animal 30% faster
than other animals (Ajayi et al., 2005) and also make rabbits suitable
as meat producing small livestock in developing countries (Arijeniwa et al.,
2000).
Ensminger (1991) identified
problems facing reproduction of some farm animals to include repeat breeding,
still birth, abortion, poor libido and poor semen quality. It had been
documented that in the study of ruminant and human infertility that chromosomal
abnormalities were the major causes of infertility and pre-natal losses of
foetus. As observed by Berepubo et al. (1993); Omeje et al.
(1994); and Wekhe (1998), chromosomal abnormalities lead to sub-fertility or
total infertility, neo-natal deaths, repeat breeding, anoestrus, congenital
defects, poor libido, poor semen quality as well as stunted growth and general
poor performance in young animals.
Chromosomal abnormalities have
been implicated for all these reproductive problems as observed by direct
karyotyping of embryos from infertile or sub-fertile dams or sire (Long and
Williams, 1980; Hares et al., 1980; Berepubo and Long, 1983; King and
Linares, 1983; Berepubo, 1985; Murray et al., 1985). X-chromatin
screening for the presence of drumstick appendages has proved to be one of the
very many techniques for diagnosing chromosomal defects. Similar studies have
revealed the presence of chromosomal abnormalities in affected farm animals
(Otuma et al., 2005; Parkaryi et al., 2008; Nyeche et al.,
2010).
In modern genetic term,
X-chromatin evaluation refers to the analysis of X-chromosome only without
reference to the Y-chromosome. The X-chromosome has been successfully used in
domestic animals to predict the cytogenetic or genetic merit of various
economically important species. These include early detection of potential sex
chromosomal and developmental anomalies which considerably impair fertility and
also the prediction of the growth potential of.....
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