The strategies
to develop poultry breeds which are suitable for poultry smallholders must
differ from those of intensive production, and should focus on improving indigenous
breeds while also making use of pure exotic and cross-bred chickens where
appropriate. The conservation of local breeds possessing genetic variations
specific to the particular environment is essential for sustainable
development. Though they exist as numerically small populations, local breeds
are not only highly adapted to the natural environment, but are also the
integral part of the lifestyle of the rural population. People, livestock and
environment form a very delicate balanced of the ecosystem, and the potential
impact of any intervention to improve production in the traditional system
should be predetermined.
Listed below are the methods and rule that should be incorporated into the improvement of breeds.
A good instance to this plan is a flock of indigenous local hens laying up to 50 eggs annually and beginning to lay during the 25th weeks of age of the birds, crossed with improved breed cockerels, which have a genetic breed potential of 250 eggs annually, with hens beginning to lay at the 21st week. The results are cross-bred hybrid pullets beginning to lay during the 24th week, with a genetic potential of laying 200 eggs annually. The first generation hybrid cross-breed has a higher theoretical genetic potential than the average of the two parent breeds, due to the effect of hybrid vigour. Unless management is improved, this genetic potential will not be realized by the hybrid cross-breed in actual practice in the environment.
In the replacement of indigenous breeds, it has consistently been found that the entire flock replacement programmes lead to increased egg and meat production, but only where the management supplies good nutrition and veterinary hygiene conditions. However, one great disadvantage is that the use of commercial hybrids to increase egg production necessarily eliminates broodiness of birds, due to the negative genetic correlation between these two factors. For this purpose, complete replacement of local birds should not be considered unless there is a reliable local supply of day-old chicks which is of an appropriate breed that is available.
The genetic development of indigenous breeds and varieties in developing nations first requires proper records of their productive and reproductive performance. Looking at production traits of indigenous breeds, the main production characteristics of the indigenous breeds are;
Methods
of improving breeds
Listed below are the methods and rule that should be incorporated into the improvement of breeds.
- Germplasm in a traditional condition should not be modified not until management and housing have been improved and then selection should be restricted to local breeds.
- In breeding, when technical conditions are optimum and a ready market exists for the products, it then improved breeds, crosses and hybrid strains that have been selected for high performance can also be introduced.
In poultry
production management system, the most common method of improving the local
gene pool is crossing indigenous birds and exotic birds, and then leaving the
hybrid offspring to natural selection. Pure-bred or hybrid cockerels or pullets
selected for greater meat or egg productions are introduced into local flocks,
usually in order to increase and maximize egg production. It is important to
note that improved growth for meat production and high egg production are
genetically incompatible in the same bird. The genetic traits are negatively
correlated, which means that selection for one trait will reduce the other
trait.
Exchange of
Cockerel or pullet
A good instance to this plan is a flock of indigenous local hens laying up to 50 eggs annually and beginning to lay during the 25th weeks of age of the birds, crossed with improved breed cockerels, which have a genetic breed potential of 250 eggs annually, with hens beginning to lay at the 21st week. The results are cross-bred hybrid pullets beginning to lay during the 24th week, with a genetic potential of laying 200 eggs annually. The first generation hybrid cross-breed has a higher theoretical genetic potential than the average of the two parent breeds, due to the effect of hybrid vigour. Unless management is improved, this genetic potential will not be realized by the hybrid cross-breed in actual practice in the environment.
If the
hybrid cross-breeds mate among themselves, potential production falls in the
very next generation to the average potential of the two original genotypes,
even if management could support the higher hybrid level. The use of cockerels
in this manner is the basis for the Cock or Cockerel Exchange Programme which
has been implemented in almost all tropical countries. Households exchange all
their local cockerels for a few improved cockerels, which are then raised to
maturity to allow them to adapt to local conditions. The gradual replacement of
local genes through cross-breeding and artificial selection has been the basis
of initial development in poultry production management system.
Indigenous
breeds replacement
In the replacement of indigenous breeds, it has consistently been found that the entire flock replacement programmes lead to increased egg and meat production, but only where the management supplies good nutrition and veterinary hygiene conditions. However, one great disadvantage is that the use of commercial hybrids to increase egg production necessarily eliminates broodiness of birds, due to the negative genetic correlation between these two factors. For this purpose, complete replacement of local birds should not be considered unless there is a reliable local supply of day-old chicks which is of an appropriate breed that is available.
The production traits of indigenous breeds
The genetic development of indigenous breeds and varieties in developing nations first requires proper records of their productive and reproductive performance. Looking at production traits of indigenous breeds, the main production characteristics of the indigenous breeds are;
- Low performance in egg numbers
- Small clutch sizes
- The noticeable effect of long pauses between laying of clutches and a predominant inclination to broodiness
- Small body size
- Lateness in maturing
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