Performances de reproduction chez les ovins Ouled Djellal

Abstract

The objective of this study was to evaluate the performance of body and testicular growth in Ouled Djellal lambs from birth until the age of one year and to adjust the growth curves according to linear and nonlinear models in order to establish the best appropriate model. Also, this research makes a contribution to the study of the onset of puberty and the evolution of semen characteristics after puberty in Ouled Djellal ram lambs. A weekly measurements of body weight, chest perimeter, scrotal circumference, as well as the both gonadal testicular length, testicular diameter and cauda epididymis diameter, were conducted in seventeen Ouled Djellal lambs from birth to puberty. In same manner, a weekly semen collection by using an electro-ejaculation was carried from ten lambs from the fourth month of age, to determine the onset of puberty (first motile spermatozoa in the ejaculate). After, the observations were made every fortnight, on the condition and body weight, chest perimeter, testicular biometry (scrotal circumference, testicular length, testicular diameter and the cauda epididymis diameter), as well as the evolution of semen characteristics collected after puberty by electro-ejaculation (appearance and volume of ejaculate, massal and individual motility, concentration, total sperm produced, percentage of motile, live and abnormal sperm). The average weight at birth was 4.49 ± 0.67 kg (mean ± SD). The effect of litter size on weight and weight gain seems significant only in the preceding puberty stage, despite that, the single born lambs are heavier at birth, tend to grow faster and reach puberty earlier than twins. Puberty settled at an average age of 227.9 ± 6.95 days in Ouled Djellal ram lambs, with an average weight of 40.4 ± 1.21 kg. Highly significant correlations were observed between testicular measurements and those of the body (weight and chest perimeter) from birth until the age of one year. Similar significant correlations were also observed between testicular measurements (especially scrotal circumference) and semen characteristics after puberty. The establishment of early selection based on gonadal measurements in addition to those of body is essential for the optimization of reproduction management in Ouled Djellal breed.