The shortage of animal protein is a common problem facing many tropical countries including Nigeria (FAO, 2003). It was reported by Akinfala et al. (2003), that the supply of animal protein for human consumption in Nigeria was below the demand. Despite the numerous advantages associated with the consumption of animal protein, the minimum intake recommended by FAO (1992) has not been met in most developing countries. Harold (1984) reported that meat was assumed to be the only product from cow when it was domesticated, whereas other dietary products from cattle included milk and its products. Harold (1984) further reported that animal milk was first known to have been used as human food around 5000 B.C. and it was first used as human food in the Middle East.
Meanwhile, the Food and Agricultural Organisation (FAO, 2001) reported that the world milk production percentage from cow was 84.6 % while that of sheep was 1.3 %. The composition of different kinds of milk as reported by George (2001) shows that the nutritional value of sheep milk with 19.30 % solids, 7 % fat, 5.98 % protein, 193 mg calcium, and 108 kcal is superior in quality to those of cow and goat with 12.01 % and12.97 % solids, 3.34 % and 4.14 % fat, 3.29 % and 3.56 % protein, 119 mg and 134 mg calcium and 69 kcal, respectively. There is therefore need to increase milk production from the sheep.
Adewumi and Olorunsomo (2009) pointed out that increasing demand for milk and its products in Nigeria has made it imperative to look for other sources of milk apart from cattle. According to the authors, local milk production has consistently fallen short of demand over the years, especially in urban centres leading to massive importation of milk and milk products. Continuous dependence on imported milk has led to increase in cost of milk thereby pushing these products beyond the reach of the average Nigerian. Hence, it is necessary to look for alternative sources of milk for local consumption.
Local sheep breeds in Nigeria have potentials to supply a significant portion of the milk deficit in the country because sheep numbers far exceed cattle numbers in both rural and urban communities (Rim, 1992; Adewumi, 2005). They are also more affordable to resource-poor families and produce more milk in relation to body size than cattle (Nuru, 1985).
Sheep milk has been found to be richer in critical nutrients except lactose, than the milk of humans, cattle and goats (Buffano et al, 1996). The high content of vitamin D and calcium in sheep milk helps in fighting against osteoporosis. It is very useful in the treatment of neurotic indigestion, insomnia, dyspepsia, peptic ulcer, pyloric stenosis and rheumatism. It is also perceived by some consumers in Nigeria to have a better and more natural taste than cow milk (Adewumi et al., 2001). Sheep milk contains a higher proportion of short and medium chains fatty acids and more conjugated linoleic acid (CLA) which is a cancer fighting and fat reducing compound (George, 2010). It produces a higher cheese yield of cheese per litre than that of cow or goat milk (Assenat 1985, Chamberlain 1989, and Adewumi et al., 2001).
The higher casein content makes the rennet coagulation time for sheep milk shorter and the curd firmer (Jandal, 1996). It has also been proposed as a more natural and better tasting alternative with great nutritional and clinical potential (Hardy, 2000). In spite of this potential, sheep have largely been neglected by researchers in the quest for increased production (George, 2001).
Apart from dry season feeding which was reported to be a major constraint confronting ruminant production in Nigeria (Bawala et al., 2007; Ademosun, 1994), Chukuka et al, (2010) reported that low genetic potential is also a prominent constraint to ruminant production. According to the authors most indigenous breeds of small ruminants in the tropics have not been selected for high productivity. The low genetic potential of WAD sheep and goats is often quoted as a major constraint to meat and milk production in Sub-Saharan Africa, hence the need for animal improvement programmes.
It is therefore imperative to research into indigenous sheep breed (WAD) with the aim of discovering its milk yield potentials and quality.
1.1 STUDY OBJECTIVES
The objectives of the study were as follows;
- To determine the milk yield of WAD Sheep in the humid tropical zone of Nsukka.
- To evaluate the composition of the milk.
- To evaluate changes in udder characteristics of WAD Sheep during gestation and lactation.
- To establish relationships between udder characteristics and milk yield during lactation.
Sheep milk is one of the protein sources which has found a niche in human nutrition. Apart from being highly nutritious, sheep milk sells for a significantly higher price/kg, almost four times the price of cow milk. (George 2010). Most of the sheep milk produced in the world is made into cheese. It is also processed into yoghurt and ice cream and the United States of America is a large importer of sheep milk cheese. (George 2010).
Therefore, it is very important to carry out this research in order to discover the milk production potentials of an indigenous breed (West African Dwarf) of sheep.