Feed intake and performance of growing lambs raised on concentrate-based diets under cafeteria feeding systems

Two trials were undertaken to study the effects of cafeteria feeding systems on the feed intake, animal performance and carcass characteristics of growing lambs. Trial 1 was designed to compare conventional and cafeteria feeding systems in terms of the growth of individually reared lambs. For this assay, 26 weaned Merino lambs (15.5 +/- 0.20 kg live weight) were assigned to three dietary treatment groups: (1) a control group fed barley straw and commercial concentrate under a conventional feeding system, (2) group W100S, fed soya-bean meal, whole barley grain and a mineral-vitamin supplement under a cafeteria feeding system, and (3) group W100S-T, fed as in the W100S treatment but allowing the lambs an initial training period so they could learn to identify a number of feeds. The feeding system had no significant effect (P > 0.05) on either average daily live-weight gain, carcass weight, or carcass conformation. The food conversion ratio was lower (P < 0.05) for the cafeteria-reared animals (2.9 +/- 0.16 v. 2.5 +/- 0.08 g dry-matter intake per g average daily gain) than those of the control group. This might be related to the higher crude protein intake seen in the cafeteria groups (150 +/- 5.6 v. 208 +/- 12.5 g per animal per day; P < 0.001). In trial 2, cafeteria and conventional feeding system were compared in terms of the growth of feedlot lambs. Two hundred weaned Merino lambs (13.1 +/- 0.10 kg) were divided into two experimental groups: (1) a control group, offered commercial concentrate and barley straw, and (2) a cafeteria group fed the same diet as W100ST in trial 1. The average daily gain (282 +/- 5.8 and 309 +/- 6.5; P < 0.01) was greater in the cafeteria than in the control group. Whereas neither carcass conformation nor fatness were affected by the feeding system, the dressing percentage was slightly higher (P > 0.001) in the conventional than in the cafeteria system lambs. The use of cafeteria systems for fattening lambs can improve the feed conversion efficiency and body growth rate over those achieved with conventional feeding systems, although the crude protein intake in these systems seems to be in excess of requirements.