Pubertal Traits In Male and Female Sudanese Desert Sheep

Abstract

The objective of the present study was to study pre and post pubertal development of reproductive traits, and to prescribe criteria for selection of young ewe and rams for breeding purposes. In the first part of this study, 8 ram lambs in their first month of age and average body weight of 8.5 kg were chosen to be used for determination of age at puberty and selection criteria for breeding soundness. External body measurements including, body weight, Heart girth, Wither height, Crown-rump and scrotal circumference were taken every 2 weeks and up to the age of 32 weeks. At the age of 20 weeks the ram lambs were subjected to semen collection once/week for 9 weeks using artificial vagina. The semen samples were examined for assessment of quantitative and qualitative characteristics using standard laboratory procedures. The results showed that puberty was attained in Desert ram lambs at an average age of 23.3±1.6 weeks ,body weight 25.6 ± 2.9 kg, Heart girth 72.3 ± 5.2 cm, crown-rump 83.2 ± 2.9 cm and scrotal circumference 24.9 ± 2.4 cm. Strong correlations between body weight and all body measurements (P< 0.01) were depicted during the period preceding puberty. The analysis of semen showed that all characteristics were low in quantity and quality in the initial collections, but there was a gradual progress with age until adult levels were reached at 29 weeks of age. In the second part of this study, 8 Desert ewe lambs were selected at their first month of age and with an average body weight of 10 kg to monitor their pubertal reproductive traits. viii All external body measurements were taken every 2 weeks, as in the ram lambs, up to 32 weeks of age. After weaning blood samples were taken for determination of progesterone levels around puberty. Desert ewe lambs showed their first oestrus at an average age of 25 ± 8.2 weeks with an average Heart girth of 69.6 ± 4.7, Crown-rump of 81.8 ± 2.9 cm and body weight of 23.6 ± 3.1 kg. Data of progesterone analysis showed that there was a significant rise in progesterone levels (> 1 ng/ml) immediately before the signs of first oestrus could be seen. The results also showed that there was a high correlation between body weight and body measurements taken during the study period. In conclusion, the present results indicated that age at breeding soundness occurred in Desert ram lambs at an average age of 29 ± 1 weeks and that ewe lambs could attain puberty at on average age of 25 ± 8.2 weeks .