(i) Use of Indigenous Breed
As earlier suggested, tropical livestock breeders must depend on the use of indigenous breeds for utmost advantages since the indigenous breeds are readily available, well adapted or acclimatise to the immediate environment and possess matching genetic traits with such environment.
However, a major limitation, to this option, is that selection for increase productivity is likely to be for a lengthy period due to, previous natural selection for survival, which was at the expense of productive traits. Thus, priorities of breeding efforts in the tropical region under the option of using indigenous breeds are:
(1) Genotype-environment interaction improvement
(2) Liveweight gain as the most important economic trait and other adaptive traits such as tolerance to diseases and pests (e.g. trypanotolerance of N’dama cattle).
(ii) Upgrading
Another option earlier mentioned is the importation and use of exotic breeds for purpose of upgrading indigenous breeds.
Consideration for importation of exotic breed should be restricted to exotic stock from temperate climate. There could be genuine rationale to import exotic stock from one region of the tropics to another.
The use of exotic breed for upgrading has the unique advantage to hasten improvement of productivity where suitable exotic breeds are used and the local environmental conditions are improved.
Major limitations have to do with high cost of upgrading and loss of genetic resources of the local breeds where upgrading is done indiscriminately.
Acclimatization of exotic breed to the local environment may be time consuming and expensive. The option of upgrading with exotic breeds should focus on:
(1) Areas with moderate climatic, disease and nutritional stress, or montane regions in the tropics.
(2) In case of dairy animals, lowland humid areas have sufficient forage year-round.
(3) Areas where no indigenous breed exists to exploit the specific peculiarity of the ecological environment. For example it may be reasonable to import water buffaloes or pigs for the creeks of the Niger Delta region of Nigeria.
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(4) Importation is strongly suggested for livestock species whose production system can be restricted from the influence of external environment e.g. intensive poultry or swine production in tropical countries.
(iii) Crossbreeding
Crossbreeding as option has its own advantage of combining desirable traits in two or more breeds in one which is usually higher in hybrid vigour.
Expressed hybrid vigour is notably in traits not largely moderated by genetic or inherited factors but more by the environment such as vigour and fertility.
Heterosis decline with age and its influence is greater in females than males and in stressful condition than in moderately good condition.
Limitations of crossbreeding option concern obtaining suitable breeds to combine, expensive and complicated management system to be evolved to obtain good results.
This possibly explains reasons where crossbreeding practices are limited to poultry, pigs and ranches in government farms or research centres in the tropics. Also, planning a crossbreeding scheme for livestock improvement may be a very difficult exercise. Planned crossbreeding should concern:
(a) Areas or breeds, which research has sufficiently approved to show tangible value, advantage or merit.
(b) In areas infested with tsetse fly that debar livestock production, crossbreeding with trypanotolerant breeds.
(iv) Developing New Synthetic Breeds
Developing a new synthetic breed is an option that seems to streamline limitations of upgrading and crossbreeding options for genetic improvement of livestock in the tropics.
It explores crossbreeding or upgrading of indigenous stock using a superior stock and then systematically selecting the offspring to form a breeding much. It may be extremely long and expensive as it is also require competent personnel.
It is often undertaken by very large private organization, government or international agencies.
However, it has an enduring result and may revolutionise livestock in the entire tropical regions. The option is highly versatile as it can be applied on dairy cattle, goat, sheep, poultry and pigs for different enterprises and for diverse production conditions.
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