EFFECT OF FAT SUPPLY TO FATTENING DIET ON GROWTH AND CARCASS QUALITIES OF EARLY WEANED MALE LAMBS FED INDOORS DURING WINTER

The effect of dietary fat supplies was investigated for growth and car cass characteristics on 270 Lacaune male-lambs randomized and fattened in 3 pens indoors during winter. Two treatments were compared with cl assical starter and fattening diets: i) 21 kg commercial starter then a commercial 'growing-fattening' diet; ii) 21 kg starter supplemented with coconut oil then the 'growing-fattening' diet supplemented with l ard; iii) 17 kg starter supplemented with coconut oil then the referen ce commercial 'growing-fattening' diet. The 2 starling diets were isoc aloric and isonitrogenous (ME = 10.9 MJ/kg DM; CP = 189 g/kg DM). One was supplemented with 5% coconut oil (fat (F) = 74 g/kg DM) and fed at 2 levels (21 kg/lamb during 29 d vs 17 kg/lamb for 21 d). The second was a reference commercial starter diet (F = 31.6 g/kg DM) issued at 2 1 kq/lamb level. The 2 succeeding growing-finishing diets were also bo th isocaloric and isonitrogenous (ME = 10.7 MJ/kg DM; CP = 176 g/kg DM ). One was supplemented with 3% lard (F = 50.4 g/kg DM) and the other was a reference commercial diet (F = 37.5 g/kg DM). All diets were giv en ad libitum and straw was freely accessible. The lambs were weaned e arly (3-5 weeks old) and were slaughtered at a fixed body weight (BW = 39 kg) in one slaughterhouse. Carcasses were scored by the same skill ed operator. From these, and for statistical purposes owing the discre pancy in the frequency distribution of initial parameters of lambs, 2 sub-samples were made and standardized according to a normal distribut ion and in respect to the weight at weaning (12 kg; 3 x [n = 58]), the relative growth between 0-20 d (16.2 g/d/g BW; 3 x [n = 64]). Concern ing growth, feeding with starter diet over an extended time produced a higher growth rate on final fattening stage (+5%, P < 0.04). Coconut oil did not promote growth during the starting stage. However, through a remaining effect, it improved the conversion food ratio in the last fattening stage when lard diet was associated (CFR = 3.6 for treatmen t a vs 3.0 kg DM/kg gain; P < 0.05). Supplementing with lard in the 'g rowing-finishing' diet did not modify the lamb growth. in the 3 lots, the conversion food ratio increased until the lambs reached about 32% of their mature weight. The relative growth came close to a maximum wh en lambs weighed about 22% of BW at maturity (17.5 g/kg BW), then it r egularly decreased to 10 g/kg BW at the end. Concerning the characteri stics of carcasses, only coconut oil supplementation during the starti ng stage induced a greater proportion of carcasses with very firm subc utaneous fat (27 vs 13%, P < 0.03) and reduced the proportion of soft and oily class of disqualitative carcasses (17 vs 33% P < 0.02). Howev er the colours of the layer ro, fat were not affected.