South African Journal of Animal Science
On-line version ISSN 2221-4062
Print version ISSN 0375-1589
The objective of this trial was to quantify the differences in average daily gain (ADG), backfat thickness (BFT), eye muscle area (EMA), fat thickness (FT) on different body parts, the feed conversion ratio (FCR), body measurements and the weight of internal organs of Dorper lambs exposed to supplemented light. For this study 120 Dorper lambs (115 ± 10 days old), weighing 29.8 ± 5.01 kg, were used. The lambs were randomly divided into three homogeneous groups (20 castrated and 20 intact males/group). Two groups were then exposed to either 16 h or 24 h of supplemented light at 145 lux, and a control the normal photoperiod. The animals were fed ad libitum with pellets containing 9.5 MJ ME/kg DM and 120 g CP/kg in open pens. The animals were weighed every seven days while ultrasound scanning of the EMA and BFT was done at the beginning and the end of the 35 d trial. The ADG, FCR and feed intake (FI) were calculated at the end of the trial. Linear body measurements including shoulder height, body length and heart girth were taken at days 1 and 35. All the animals were slaughtered at the end of the trial. The carcasses were weighed, graded and the FT was measured with a caliper. It was concluded that there are no differences between treatments in terms of body measurements, ultrasound scanning, ADG and FCR.
Keywords : Light supplementation; photoperiod; Dorper lambs; intensive feeding.