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.
Serum biochemical tests have been widely used for the diagnosis of various animal diseases. The information gained from serum enzymes activity would substantiate the physical examination coupled with medical history to provide excellent basis for judgment with respect to the nature of the disease, the extent of tissue and organ damage and to select appropriate treatment (Schalm et al., 1975).
Although clinical biochemistry is potentially a valuable diagnostic aid in the veterinary care of animals, the interpretation of results in sick animals is often difficult.
Any physiologic and pathological changes can be evaluated only if the normal values are available for comparison. Considerable information is available on the normal serum enzyme levels of domestic animals of exotic breeds kept under different environment and management conditions. The use of serum enzyme values that are derived from exotic breeds for monitoring the health status of indigenous breeds could be misleading. Factors such as age, breed, geographical location, accidental haemolysis while sampling, diet, sex, diurnal variation, physical activity, pregnancy and environment are known to influence serum enzyme concentration in domestic ruminants (Sastry 1985; Coles 1986; Sigma Diagnostics 1990; 1997; Otesile and Kasali 1992; Alonso et al., 1997).
Transaminases (alanine aminotransferase [ALT]/glutamic pyruvic transaminase [GPT] and aspartate aminotransferase [AST]/glutamic oxalacetic transaminases [GOT]) and phosphatases
(alkaline phosphatase [ALP] and acid phosphatase [AcP]) are important for diagnosing diseases. Transaminases catalyse the transfer of a-amino groups from specific amino acids to aketoglutaric acid to yield glutamic acid and oxaloacetic acid or pyruvic acid. An increase of ALT/GPT in the serum reflects cellular abnormalities, cellular degeneration or destruction of hepatocytes providing information on liver status. Serum AST/GOT test is of value in confirming a diagnosis of muscular degeneration (both cardiac and skeletal muscles) in all species as it appears in extremely higher concentrations in muscle than other tissues (Coles, 1986). Phosphatases are agents that hydrolyse phosphoric esters with the liberation of inorganic phosphate.
ALP and AcP are found in blood. ALP is widely distributed in the body and found in high concentrations in bone (osteoblasts), renal tubule cells, liver, placenta and intestinal mucosa. Its determinations are frequently included as part of routine biochemical profiles (Coles 1986). Exception for a report by Otesile and Kasali (1992) on transaminases of nondescribed Ethiopian highland sheep breeds, there has not been any study to date on the serum enzyme levels of sheep breeds from Nigeria.
The aim of this study was to give reference values of ALT/GPT, AST/GOT, ALP and AcP enzymes for four indigenous Nigerian sheep breeds and to determine the influences of age, sex, and season on the level of the enzymes.
To enhance the health status of animals thereby improving on its management, production and physiological state, there is the need to study discrete serum biochemical parameters of indigenous sheep in Nigeria in relation to its genetic (breed) and non genetic factor (sex and age)
1.2.1 Broad Objectives
The broad objective of this research is to determine the genetic (breed) and non-genetic factors (sex and age) affecting serum biochemical parameters in Nigerian sheep.
1.2.2 Specific Objectives
- To determine the effects of breed on serum biochemical parameters in Nigerian sheep.
- To determine the effects of sex on serum biochemical parameters in Nigerian sheep.
- To determine the effects of age on serum biochemical parameters in Nigerian sheep.
- To make recommendation based on the discoveries.