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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