Agriculture Reference
In-Depth Information
common, with triplets being common. The percentage of
singletons, twins, triplets, and quadruplets in goats are
quoted as being 24.5, 59.2, 15.3, and 1%, respectively
(Gall, 1981; Greyling, 1988; Hafez and Hafez, 2000).
much semen quality) is affected by seasonal changes. This,
however, is not always the case. It was found that semen
motility tended to be lower from June to October (onset
winter to midspring) for the Boer goat and Angora goat in
South Africa. Spermatogenesis or the formation of sperm
is generally a lengthy process, taking approximately 50 to
60 days (from spermatogonia to sperm formation) and
involving different stages (spermatocytogenesis and sper-
miogenesis) in the seminiferous tubules. When spermato-
genesis is completed, the sperm move to the epididymis
where they mature for 2-3 weeks. Thus, for mature, viable
sperm to be produced, it takes from 60-80 days. In the
event of temporary sterility (for example, due to fever fol-
lowing blue tongue vaccination), the time required for
complete spermatogenesis must be kept in mind if optimal
fertilization is to be obtained (Greyling and Grobbelaar,
1983, 1988; Jainudeen et al., 2000; Salamon and Maxwell,
2000 ).
The technique of semen collection is also an aspect to
be noted when determining semen quality (Table 7.3 and
Table 7.4). It is accepted that sperm motility and the per-
centage of live sperm determine the quality of the semen.
The density or concentration of an ejaculate and the per-
centage of live sperm were found to be higher in semen
collected by means of the artifi cial vagina. However, the
fi nal and most important criterion in the evaluation of
semen quality lies in the fertilizing capacity of the sperm
(Greyling and Grobbelaar, 1983; Karagiannidis et al.,
1999 ; Barkawi et al., 2006 ).
Postpartum Anestrous Period
An important aspect in the reproduction chain is the post-
partum anestrus period. This interval between parturition
and the fi rst postpartum estrus determines how soon after
parturition conception can possibly occur. The mean post
partum anestrous period is quoted as being 56.0
±
5.1 days
and 45.2
5.8 days in primiparous and biparous
Barbari does, compared to duration of 55.5
±
24.9 days in
the Boer goat. This interval varies between breeds, nutri-
tional regimes, and lactational status of the female.
Reducing the suckling intensity may result in an earlier
return to estrus and a greater percentage of does rebreeding
within 60 days postpartum. A signifi cant lower conception
rate (19.1%) at an early postpartum estrus (15-30 days)
was observed in goats, compared to does exhibiting estrus
later (66.7-87.5% conception). No signifi cant differences
in the postpartum anestrous period between does bearing
singletons, twin, triplets, or quadruplets have been
recorded, although suckling as such exerts an inhibitory
effect upon the synthesis and/or release of LH during the
postpartum period. Season of kidding could also affect the
postpartum interval to fi rst estrus. The postpartum anes-
trous periods for does kidding in autumn (breeding season)
is quoted as being signifi cantly shorter (37.3
±
±
12.5 versus
59.9
18.0 days, respectively), when compared to does
kidding in spring (nonbreeding season). The stimulatory
effect of the presence of the male (pheromones) in the
postpartum doe is a factor not to be ignored when deter-
mining or manipulating the interval from parturition to fi rst
estrus
±
CARE AND MANAGEMENT OF THE BUCK
The importance of the buck in the whole breeding program
is not to be underestimated. Although only actively used
for approximately 6 weeks in a fl ock mating system or
intensively for a week or two when used in an artifi cial
insemination program, the buck has to be well managed.
From weaning at 3 months of age, following the neces-
sary dosing for tapeworm and vaccinations as recom-
mended by the veterinarian, males should be maintained
on an above-maintenance energy diet. The average body
weight of Boer goat bucks at 100 days of age (weaning)
is 27 kg and the body weight at 12, 18, 24, and 36 months
of age is 55 kg, 75 kg, 88 kg, and 115 kg, respectively.
Acceptable body conformation, size, and appearance are
prerequisites when used for breeding. Because goats are
predominantly browsers (70%), they can effi ciently use
bushes and shrubs and in time of shortages or droughts be
nutritionally supplemented to maintain an acceptable body
condition (even if not used for breeding).
(Riera,
1982 ;
Chemineau,
1983 ;
Torres - Acosta
et al., 1996; Hafez and Hafez, 2000).
PHYSIOLOGY OF THE
MALE REPRODUCTION
The neuro-endocrine control of testicular function is
similar to that observed in the female. Briefl y it can be said
that FSH (spermatogenesis stimulating hormone [SSH])
and LH (interstitial cell stimulating hormone [ICSH]) in
the male are the two gonadotrophic hormones mainly
responsible for spermatogenesis in the seminiferous
tubules and testosterone production in the cells of Leydig,
respectively. Generally the photoperiodic control of sexual
activity in the buck is less pronounced than in the doe.
Some researchers allege that semen production (and not so
