ABSTRACT
Twelve West African Dwarf (WAD) sheep, four in each of parities one, two and three were used to determine effect of parity and birth type on udder characteristics during pregnancy and lactation, milk yield and composition and their phenotypic relationships with milk yield . Udder length (UL), udder width (UW), udder circumference (UC), udder volume (UV), teat length (TL), teat width (TW), teat circumference (TC), distance between the teat (DBT) and teat height from the ground (THG) of sheep were measured monthly for the five months of pregnancy and weekly for the twelve weeks of lactation commencing from four days post partum. Result showed that, parity effect on all udder characteristics during pregnancy and lactation was highly significant (P < 0.01). During pregnancy ewes in parity three had highest values (cm) of 8.26, 8.08, 23.95, 1.12, 1.08, 2.49, 287.34, 6.25 and 27.20 for UL, UW, UC, TL, TW, TC, UV, DBT and THG, respectively, followed by ewes in parity two with values (cm) of 6.30, 7.32, 23.29, 1.05, 0.72, 2.18, 229.3, 5.73 and 23.69 for UL, UW, UC, TL, TW, TC, UV, DBT and THG, respectively. Those in parity one had least values (cm) of 5.88, 6.33, 22.19, 1.02, 0.69, 2.14, 119.91, 5.35 and 22.02 for UL, UW, UC, TL, TW, TC, UV, DBT and THG, respectively. During lactation, ewes in the third parity had significantly highest values (cm) of 9.08, 9.00, 39.10, 1.89, 1.24, 3.31, 400.36, 7.11 and 25.98 for UL, UW, UC, TL, TW, TC, UV, DBT and THG, respectively, followed by those in the second parity with 7.88, 8.66, 35.79, 1.57, 1.03, 2.53, 310.03, 6.56 and 24.95 for UL, UW, UC, TL, TW, TC, UV, DBT and THG, respectively. Ewes in the first parity had significantly lowest values (cm) of 7.33, 8.35, 32.56, 1.28, 0.93, 2.41, 271.90, 6.28 and 25.98 for UL, UW, UC, TL, TW, TC, UV, DBT and THG, respectively. Birth type effect on udder characteristics during pregnancy and lactation was highly significant (P < 0.01). Twin bearing ewes had significantly higher values (cm) of 6.88, 7.31, 23.71, 1.09, 0.85, 2.35, 227.68, 5.86 and 24.68 for UL, UW, UC, TL, TW, TC, UV, DBT and THG, respectively than those of single bearing ewes (6.74, 7.18, 22.58, 1.03, 0.80, 2.18, 196.64, 5.68 and 23.92 for UL, UW, UC, TL, TW, TC, UV, DBT and THG, respectively) during pregnancy. During lactation, twin bearing ewes had significantly higher values (cm) of 8.35, 8.98, 37.25, 1.67, 1.13, 2.82, 364.25, 6.75 and 25.10 for UL, UW, UC, TL, TW, TC, UV, DBT and THG, respectively than single bearing ewes with values of 7.84, 8.36, 34.38, 1.49, 1.01, 2.69, 290.61, 6.55 and 24.65 for UL, UW, UC, TL, TW, TC, UV, DBT and THG, respectively. Ewes in the third parity had highest mean milk yield of 228.95 ml followed by ewes in second parity (157.18 ml), while ewes in the first parity had least milk yield of 126.42 ml. Twin bearing ewes in the third parity had highest mean milk yield of 249.09±14.85 ml during lactation. Single bearing ewes in the first parity had the smallest mean value of 124.54 ml. Parity effect on milk composition was highly significant (P < 0.01) for moisture, total solid, solid not fat, protein, fat and ash but not significant (P > 0.05) for lactose. Ewes in the third parity had highest mean values (%) of 79.24, 20.73, 12.98, 6.58, 7.84, 0.77 and 5.53 for moisture, total solid, solid not fat, protein, fat, ash and lactose, respectively, followed by ewes in the second parity with 80.95, 18.84, 11.79, 6.04, 6.27, 0.76 and 4.98 for same constituents while ewes in the first parity had the corresponding values of 82.75, 17.25, 10.63, 5.48, 6.61, 2.75 and 3.37. Birth type effect on milk composition was highly significant (P < 0.01) for all milk constituents except total solid and lactose. Twin bearing ewes had significantly higher mean values (%) of 80.86, 18.94, 11.85, 6.06, 7.29, 0.768 and 4.97 for moisture, total solid, solid not fat, protein, fat, ash and lactose respectively, than those of single bearing ewes with 81.08 %, 18.92 %, 11.75 %, 6.00 %, 7.18 %, 0.760 % and 4.96 % for corresponding constituents. The correlation coefficients between udder dimensions and milk yield were; 0.92, 0.79, 0.91, 0.92, 0.86, 0.88, 0.60, 0.08 and -0.24 for UL, UW, UC, TL, TW, TC, UV, DBT, and THG respectively.
CHAPTER ONE
1.0 INTRODUCTION
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.....
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