EFFECT OF PARITY AND BIRTH TYPE ON UDDER CHARACTERISTICS MILK YIELD AND COMPOSITION OF WEST AFRICAN DWARF SHEEP

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

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;

(i)   To determine the milk yield of WAD Sheep in the humid tropical zone of Nsukka. (ii)  To evaluate the composition of the milk.

(iii) To evaluate changes in udder characteristics  of WAD Sheep during gestation  and lactation.

(iv)  To  establish  relationships  between  udder  characteristics  and  milk  yield  during lactation.

1.2 JUSTIFICATION

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.

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