GENETIC AND NON GENETIC FACTORS AFFECTING SERUM BIOCHEMICAL PARAMETERS IN NIGERIAN SHEEP. A RESEARCH PROJECT MATERIAL ON BIOCHEMISTRY
African sheep are usually described as thin-tailed, fat-tailed or fat-rumped and thin-tailed are sometimes further segregated into hairy or woolled types. Thin-tailed sheep are commonest in the northern dry tropics where they are usually of large size or in the western humid areas where they are smaller and often referred to as dwarf or forest sheep. Fat-tailed types predominate in eastern Africa as far as south Mozambique. Fat-rumped types are commonest in traditional systems in north-east Africa, but have spread in commercial systems to Zimbabwe and other countries of the southern region. (Mason and Maule, 1960)
Sheep are kept everywhere in Nigeria, with a broad distinction between their importance and ubiquity in the north, and the more dispersed populations of the humid zone.
There are four main breeds of sheep native to Nigeria: the Balami, Uda, Yankasa and West African
Dwarf. Balami and Uda are kept in the semi-arid regions, West African Dwarf sheep in the south and Yankassa throughout the country. Sheep are the second most numerous pastoral species, and small flocks accompany many cattle herds in the North and in the Middle Belt.
Comparison of pastoral and village stock shows that pastoral animals are generally more productive. The productivity of West African Dwarf sheep was substantially lower than that of other breeds. All Nigerian sheep are used for wool, but are rarely milked. In the north they are regularly eaten and form part of every-day protein supply, but there is also a marked variation in demand coinciding with religious festivals. As a result there are dramatic seasonal price fluctuations, and in some areas household fattening of sheep for sale is a major economic activity. (Bourn et al., 1994)
Local breeds have developed more through genetic isolation and natural selection. Sheep contribute an estimated 11% of domestic meat production (Otchere and Kallah, 1990).
The productivity of small ruminants in Africa is constrained by various factors among which high prevalence of diseases, inadequate utilization of indigenous genetic resources, low plane of nutrition, poor management and extensive production systems constitute the most important constraints. Of these factors, diseases are rampant with significant impact on the productivity of animals (Mukasa-Mugerwa et al., 2000; Woldemeskel et al., 2002; Tibbo et al., 2003). Proper disease diagnosis is a precondition to envisage an effective treatment, disease control or prevention strategies.