Sheep (Ovis aries) are quadrupedal, ruminant mammals typically kept as livestock. Like all ruminants, sheep are members of the order Artiodactyla, the even-toed ungulates (Theodor, 2001; Mooney and Zavaleta, 2016). Although the name "sheep" applies to many species, in everyday usage it almost always refers to Ovis aries. Domestic sheep are more than one billion and are the most abundant species in their genus (The Editors of Encyclopaedia Britannica, 2020). Sheep are most likely descended from the wild mouflon of Europe and Asia. One of the earliest animals to be domesticated for agricultural purposes, sheep were raised for fleece, meat (lamb, hogget, or mutton), and milk. Domestication of wild sheep took place in Mesopotamia in the Middle East in Central Asia, in present-day Turkey, Iraq, Syria, Jordan, Lebanon, and Israel. Findings of bones of sheep date back to the Neolithic or New Stone Age (10,000-8,000 B.C.) (Budiansky, 1999; Hiendleder et al., 2002). Sheep entered the African continent not long after their domestication in western Asia. The first sheep entered North Africa via Sinai and were present in ancient Egyptian society between eight and seven thousand years ago. Sheep have always been part of subsistence farming in Africa, but today, South Africa is the only country that keeps an influential number of commercial sheep (Blench and MacDonald, 1999).
There are four breeds of sheep native to Nigeria namely Yankasa, Uda, Balami, and West African Dwarf (WAD) (Adu and Ngere, 1979; RIM, 1992). These sheep are closely related and are generally considered a variety of a breed designated ‘Fulani’ (Mason, 1988). The Balami is the largest-bodied native sheep in Nigeria. Sheep are kept everywhere in Nigeria. Sheep are kept both in villages and by pastoralists. While Yankasa, Uda, Balami are more common in the north, the WAD is more common in the south.
Sheep is one of the livestock species that serves as the main source of livelihood for livestock farmers in Nigeria. They reproduce and multiply fast and are easily convertible to cash to meet the financial needs of the farmers including agricultural inputs, school fees, and so on. Sheep are assets that need low initial investment with fast profits due to quick reproduction (Amankwah et al., 2012). However, the many contributions of sheep to rural society are being challenged by drought most especially in the arid and semi-arid environments. Sheep is susceptible to abortion, the birth of under-sized weak lambs, and outbreaks of diseases such as coccidiosis, enterotoxaemia, pregnancy toxemia, and so on during drought due to stress and dietary problems (Chedid et al., 2014; Leite-Browning, 2016).
Previous studies on the effect of drought on sheep in the semi-arid agroecological zones of tropical Africa include Devereux et al. (1993), Alary et al. (2014), Catley et al., 2014; Oyekale, 2014; Ahmed et al., 2019), Devereux et al. (1993) examined the socio-economic impact of the 1992/93 drought on households in Namibia. Alary et al. (2014), assessed the livelihood strategies and the role of livestock in the processes of adaptation to drought in the Coastal Zone of Western Desert (Egypt). Catley et al., 2014 examied the livestock mortality in pastoralist herds in Ethiopia and implications for drought response. Oyekale (2014) studied the impacts of climate change on livestock husbandry and adaptation options in the arid Sahel belt of West Africa: evidence from a baseline survey. Ahmed et al. (2019) studied the economic burden of livestock disease and drought in Northern Tanzania.
Despite these studies and the fact that the impacts of drought remain a serious challenge, no study exists on the effect of drought on the changing pattern in sheep breeds in the semi-arid agro-ecological zone of Nigeria. This study fills the gap created by insufficient literature on drought on the changing pattern in sheep breeds in the zone. The objectives of the study include: the characterization of drought in the study area; assessment of sheep breeds and changes in sheep breeds over time in the study area; examination of the nature of the drought impact on sheep in the study area