In my article "Improvement of pig-meat production in developing countries: 1. Exploitation of hybrid vigour (heterosis)", World Animal Review No. 60 (1986), I pointed out that cross-breeding of indigenous pigs from different locations within a country I might bring about worthwhile heterosis. In the same paper I also gave my unpublished findings that the indigenous pigs in Sri Lanka have existed as isolated populations in different locations. These populations are inbred and cross-breeding of pigs between locations exhibited worthwhile heterosis in litter traits.
I thought it might be of interest to the readers of World Animal Review to know some of the research findings regarding isolated indigenous pig populations, published in a report which is not readily available to readers.
Tanaka, Kurosawa and Cyril (1986) studied blood protein polymorphisms and blood groups of indigenous pigs in four different locations in Sri Lanka. The eight blood proteins, controlled by 22 loci, were studied using electrophoresis and blood types were determined using international standard reagents for 17 factors belonging to eight genetic systems. The results showed significant differences in gene frequencies between locations, both in blood proteins and blood types. The proportion of polymorphic loci were in the range of 18.1831.8 percent and the average heterozygosity was in the range of 7.88-12.21 percent in the four local populations.
These results further support my observation on the isolated indigenous pig populations in Sri Lanka and give objective evidence regarding the differences in gene frequencies between locations and also about the inbreeding status of the population.
It appears that this situation is not unique to the indigenous pig population of Sri Lanka. The same authors also reported an even lower percentage of polymorphic loci in the Indonesian indigenous pigs. In addition, my observations in Nigeria, Zambia and Zimbabwe showed that the indigenous pig population in these countries also exist as isolated populations in different locations within the countries, and that the rate of inbreeding within small village populations is quite high. Therefore, it will be interesting to investigate the situation in other countries.
Cross-breeding of pigs between such isolated populations will not only give worthwhile heterosis but also higher genetic variability.
N. Pathiraja, Ph.D.
Department of Animal Science university of Zimbabwe
Tanaka, K., Kurosawa, Y. & Cyril, H.W. 1986.
Morphological and genetic studies on native pigs in Sri Lanka. Report of the Society for Researchers on Native Livestock, Japan, 11: 129-141.