Thesis 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.

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