Effect of energy source, cereals vs sugar beet pulp, on growth performanceand carcass quality of intensively reared lambs.

Soft and off-coloured subcutaneous adipose tissue can be observed in a vari able proportion of intensively reared lamb carcasses. This can result in fi nancial losses for farmers. Introducing sugar beet pulp in the finishing di et has sometimes been recommended since it is thought to improve adipose ti ssue quality. Compared with cereals, the sugar beet pulp might modify rumin al fermentation and decrease the proportion of propionate produced. Propion ate may be used as a primer unit for the synthesis of fatty acids with low melting points which are characteristic of soft adipose tissue. The aim of this study was to verify the effects of sugar beet pulp on performance and carcass quality. Forty-eight male "Lacaune" (milk breed) lambs, weaned at 2 7 (+/- 4) days were used. They were given hay and a pelleted concentrate co mposed of either wheat and barley (80 %, group C) or sugar beet pulp (70 %, group P) ad libitum. The firmness and the colour of the adipose tissue wer e scored 18 hours after slaughter both visually and manually. Growth rate w as higher in group P than in group C (377 vs 328 g.d(-1) (P < 0.01), respec tively) even though there was no significant difference in the amount of th eoretical metabolisable energy ingested between groups (3.34 vs 3.22 Mcal.d (-1)). Plasma concentrations of glucose and beta-hydroxybutyrate were highe r in group P than in group C (0.88 vs 0.84 g.L-1 (P < 0.05) and 49 vs 37 mu eq.L-1 (P < 0.01), respectively). P lambs tended to deposit less internal fat than C lambs. However, the firmness and the whiteness of subcutaneous f at was not improved by diet P compared to diet C. More carcasses with soft adipose tissue were observed in P compared to C (P = 0.20); 0 vs 5 carcasse s were judged to be firm, 9 vs 8 were judged to be slightly soft, 11 vs 7 w ere judged to be soft and 4 vs 4 were judged to be very soft and oily, in t reatments P and C respectively. ((C) Elsevier / Inra).