Abstract :
In this study, the influence of two feeding regimes on certain reproductive characteristics of young Dorper rams was
investigated. Thirty-two Dorper ramswere divided into two homogeneous groups. Rams in the first group (n = 16), 472.5±8.0
days old were fed ad libitum intensively on a diet (9.5 MJ ME/kgDM and 12.5% protein) for 7 weeks, while the second group
(n = 16), 460.6 ± 8.5-day-old rams were maintained on natural pastures and received lick supplementation (100 g/animal
per day) with 16% CP, 8 MJ ME/kgDM and 10% fibre for a similar period of time. At the end of the trial period, semen was
collected by electro-ejaculation from each ram and evaluated, prior to the slaughtering of the rams. Following slaughter, the
scrotums were excised and dissected. Seminal, scrotal, testicular and carcass characteristics of rams from both groups were
compared. Nutritional management had an influence on scrotal circumference, scrotal weight, scrotal fat, testes weight and
volume. Significant greater scrotal circumference (SC) were recorded in the intensively managed (IM) rams (34.1 ± 0.4 cm)
compared to the extensively managed (EM) rams (31.8±0.6 cm) and significantly more fat deposits (particularly in the scrotal
neck) were found on the IM rams (109.1 ± 8.7 g) when compared to the EM rams (45.4 ± 6.5 g). Significant differences
between the IM (50.1 ± 3.8% and 2.3 ± 0.3) and EM (80.5 ± 2.3% and 3.3 ± 0.2) rams were observed for overall motility
(P < 0.01) and mass motility (P < 0.05), respectively. There were marked differences between the groups in favour of the
extensively managed (EM) rams for most semen characteristics. The evidence suggests that over-feeding of young rams could
be detrimental to their fertility.
© 2003 Elsevier B.V. All rights reserved.
