Effect of different husbandry systems on the reproductive development of post-weaning ram lambs under tropical conditions

Abstract

Two groups of three-to four-month-old weaning ram lambs were studied for 20 months, beginning with weaning at between three and four months. Group 1 was comprised of nine ram lambs which were reared under an intensive husbandry system, and given standard nutrition and mineral supplements throughout the study. Group 2 was comprised of nine rams which were reared under the traditional nomadic/extensive management system, in which the only source of feed was the available pasture. The reproductive traits studied include: age, weight and scrotal circumference at puberty and at all corresponding ages up to 23 months, libido and sexual dexterity and semen characteristics at puberty and all corresponding ages. In the intensively managed rams, the average age at puberty was 6.4±0.5 mos. The averages of the other parameters at puberty were: body weight (BW), 21.7±2.5kg; scrotal circumference (SC), 18.5±1.3cm; libido score, 1.7±0.7 and sexual dexterity, 1.7:0.8. In the extensively managed rams, the average age at puberty was 7.8±0.3 mos. The average values of the various parameters at puberty were: BW, 17.3±1.2kg; SC, 15.2±1.4cm; libido score, 3.2±0.6 and sexual dexterity, 3.2:1.8. The inter- and intra-group variations in all the parameters at puberty and at all corresponding ages were significant. The average morphological sperm cell abnormalities at puberty were: 25.2±3.4% and 31.6±8.3% for rams reached puberty and at all corresponding ages than the extensively reared flock. Certain factors that influence post-weaning reproductive development and performance are discussed.