Compensatory growth and carcass composition of Barbarine lambs receiving different levels of feeding with partial replacement of the concentrate with feed blocks

Seventy-seven male Barbarine lambs (average live weight 22.5 kg) were used to study the effects of restricted feeding and re-alimentation (compensatory growth) with concentrate or feed blocks on daily gain and carcass composition. Five lambs were slaughtered at the start of the trial; the remainders were randomly allocated to four equal groups. In the first experimental period (restricted period, 105 days), two groups received a high feeding level (FL). The first group received 800 g of oaten hay and 500 g of concentrate (CH). The second group (BH) received the same amount of hay but half of the amount of concentrate (250 g) was replaced by olive cake-based feed block ad libitum. The third group (CM) received half of the amount of feed of the CH group (400 g of hay and 250 g concentrate). The fourth group (BM) also received 400 g of hay, but with 125 g concentrate and feed block. At the end of this experimental period, six lambs per group were slaughtered. In the re-alimentation period the 12 remaining animals in each group were divided into two sub-groups and received one of four diets: six lambs from the CH group and six from CM each received ad libitum concentrates (CHH and CMH); the other six lambs from each of CH and CM received 500 g of concentrates/day (CHM and CMM). Similarly, six lambs from BH and six from BM were offered 500 g/day concentrates and ad libitum access to the feed block (BHH and BMH); the other six lambs from each of BH and BM received 250 g concentrates and feed block ad libitum (BHM and BMM). In the re-alimentation period hay was offered ad libitum to all groups. At the end of the trial, all animals were slaughtered at a live weight of 37.2 +/- 5.4 kg. In the restricted period, the H feeding level increased fat (P<0.001) but decreased lean (P<0.01) content for CH and the opposite for BH. In the re-alimentation period carcasses of lambs receiving the high and medium levels of concentrate contained more lean (P<0.001) than those receiving feed blocks. Animals receiving concentrate gained more (P<0.001) lean per day (30 g/day) than did animals on feed blocks (15 g/day). Fat daily accretion for animals on concentrate was the lowest (P<0.01) at the medium feeding level. Furthermore, lambs on the high feeding level during the first period lost fat when given the medium feeding level in the second period. Overall, sheep on feed block stored more (P<0.05) fat than those on concentrate. It is concluded that manipulation of FL during the fattening period could direct the tissue growth and carcass composition. Better results with feed blocks could probably be obtained if more protein was added to the mix. (C) 2007 Elsevier B.V. All rights reserved.