The Sunday News
Fortune Jomane
THE very high productivity we see in commercial livestock such as broilers, layers, dairy, and beef cattle among others is a result of deliberate selective breeding strategies.
To highlight the power of genetic improvements some decades ago broiler chickens were weighing around 600 grams at eight weeks and looked like chicks that people will be ashamed to slaughter. However, due to selective breeding, broilers can now attain more than 4 kgs at the same age (eight weeks) and they look very ready for the pot though age-wise they are chicks.
On the other hand, if you give indigenous chickens (ecotypes) the same feed given the broilers and manage them similarly they will still be too small at around 500 grams at eight weeks.
The difference arises because broilers have been genetically improved for growth and high feed conversion efficiency over the years and indigenous chickens have not.
An equally impressive improvement in the productivity of animals has been realised in pigs, layers, goats, dairy, and beef commercial herds.
This improvement in production has been driven initially by individual farmers and subsequently by clusters of farmers that had a common interest and in improving traits of economic importance in their livestock. Most of the farmers ended up forming formalised livestock improvement associations that govern the standards and direction of livestock improvement for specific breeds. Some breeding societies are national while some are international. Other sectors like broiler chickens are driven by private companies.
In Zimbabwe, formal livestock genetic improvement is regulated by the Zimbabwe Herd Book (ZHB) which was enacted by an act of parliament.
The ZHB registers and regulates Livestock Breeding Associations. Breeding associations prescribe breed standards to their clientele according to pedigree, quantitative (e.g. weight), and qualitative traits (e.g. colour).
These standards ensure that animals that are registered meet a certain standard in traits deemed important by the society, secondly, the standards can be used to transform the population in the desired direction.
To date, the ZHB and accredited Breeding Associations/Societies have played a pivotal role in livestock genetic improvement in Zimbabwe.
It is noteworthy however that the bulk of the breeding livestock in the country are nondescript livestock that is not registered and may not conform to any Breeding Society Standards. The bulk of this livestock is in the smallholder sector (communal, old resettlement, and A1 resettlement models).
Several stakeholders which include farmers themselves, government departments, research stations, non-governmental organizations (NGOs), and academic institutions are well aware of the need to enhance livestock productivity in the smallholder sector through genetic improvement.
Some of the efforts made include the introduction of exotic breeds to crossbreeding with indigenous livestock through natural reproduction or the aid of artificial insemination.
Crossbreeding is a rapid way of genetic improvement. It introduces genes and traits from a different breed and may result in increased performance due to hybrid vigour expressed in the crossbred offspring.
The advantage of the approach is that traits of indigenous livestock and exotic livestock are blended and exhibited in the offspring. For crossbreeding to work effectively animals with good combining ability should be crossed. One of the commendable success stories is the development of the Bonsmara breed in South Africa.
The Bonsmara is a result of systematically crossbreeding the indigenous Afrikaners and the exotic Hereford or Shorthorn cattle.
The Afrikaner had good heat resilience but exhibited poor reproduction traits, on the other hand, the exotic breeds had better reproduction traits.
The Bonsmara has since become one of the most dominant breeds in South Africa and is sought after internationally. Perhaps the lesson we can learn in Zimbabwe is that the development and introduction of the Bonsmara was a result of crossbreeding research experiments and systematic introduction of the breed which sustained the Bonsmara SA Cattle Breeders’ Society.
The Breeding society plays a pivotal role not only in maintaining breeding standards but also in further improving the breeding standards in the farming community that subscribe to it.
Another approach being used by stakeholders in Zimbabwe involves the introduction and use of pure exotic breeds.
For example, there has been an increase in the number of farmers importing and keeping Boer goats among other exotic livestock. A lot of genetic improvement has been done in South Africa to make the breed what it is today.
The improvement was started by individual farmers in South Africa decades ago. Today Boer goat improvement is governed by a vibrant SA Boer Goat Breeders’ Association.
When these exotic animals are imported into Zimbabwe farmers have to maintain similar standards in selective breeding so that the expected performance is maintained in Zimbabwe otherwise there is a possibility of regressing in standards and performance every generation.
Once there is no regulator of standards like a breeding society or similar structure and a farmer does not monitor standards like growth rate and size etc. and use them for selective breeding, genetic improvement ceases. Breeding standards are a tool to maintain or improve a population.
They are meant to decide which animals can be used as breeding stock and which ones can be culled. What will be happening at the DNA level is that the frequency of animals with favourable genes (e.g. those related to fast growth) will increase while those with undesirable genes are reduced in a population. The result is that the population will have a lot of fast-growing animals or whatever trait of importance.
Finally, there is a slower approach that is being used by some stakeholders which involves pure breeding indigenous breeds which do not involve crossbreeding. It is relatively unpopular because it takes a long time for significant changes to be realized.
There are a few organizations and farmers that focus on the pure breeding of indigenous livestock. One of the international success stories of promoting indigenous livestock is from Japan.
Japan had initially made the mistake of trying to improve their cattle through crossbreeding with large European cattle.
Fortunately, they realised that the benefits there were getting from bigger crossbred animals were less than the benefits of improving their indigenous livestock through straight breeding. They observed that crossbred animals had inferior meat quality (less marbling/intramuscular fat) compared to their well-marbled indigenous livestock.
Further, they realised that the crossbred animals were very difficult to use for ploughing their fields because of the large frame. It is noteworthy that the country was not well mechanised then. Having realised that crossbreeding was having more negative than positive effects.
They ceased crossbreeding and focused on the improvement of their indigenous livestock through pure breeding.
The results have received global attention. Japanese beef has been rated as one of the best globally. The results could have been disappointing if they had continued with their crossbreeding programme.
(To read the full article visit www.sundaynews.co.zw)
Fortune N Jomane (PhD Animal Science, Animal Breeding, and Genetics).
He writes in a personal capacity. Feedback to [email protected]
