INFLUENCE OF THE INCORPORATION OF MEDIUM-CHAIN FATTY-ACIDS IN POST-WEANING DIET UPON GROWTH SCORES AND CARCASS CHARACTERISTICS OF EARLY-WEANED LAMBS INTENSIVELY FATTENED IN THE PEN DURING SUMMER

The influence of the incorporation of medium-chain fatty acids (coconut oil) in the transition diet upon growth scores and carcass characteristics of market lambs, when given after weaning, was examined in dairy Lacaune male lambs, which had been weaned early at 5 wk and intensively fattened in a pen during the summer. Two standardized samples of lambs (n = 144 and n = 122) were used, taking into account the initial weight at the beginning of the fattening period. The first sample consisted of standardized lambs weighing 9.5-14 kg, and the second light and heavy lambs (9-11 kg and 12-15 kg, respectively). The animals were fed with 4 different diets over a 3-wk period. Two diets with an energy concentration of 1.0 UFV/kg DM (ME) and 2 with a higher energy concentration (HE: 1.05 UFV and 1.12 UFV/kg DM) were used to test the influence of energetic status. The influence of medium-chain fatty acids was analyzed with the introduction of 5% coconut oil in one diet of every level of energy. All the diets had the same level of crude protein (190 g/kg DM). The late fattening period included the same commercial diet (NE = 1 UFV/kg DM and CP = 165 g/kg DM) to a slaughtering weight of 39 kg. Comparison with a sample studied at the end of the previous winter showed a reduction in growth scores (DGR: 280 vs 298 g; fattening duration: 102 vs 91 d) and improved firmness and color of the carcasses. Regarding overall fattening, the apparent similarity between growth rate and fattening duration hides differences in the growth sequences. The second sample shows the influence of diets and weaning weight upon growth curves. The daily growth rate of the light lambs fed with diet ME supplemented with coconut oil is higher than the 3 others during the transition period (193 g/d vs 96 g/d), and the growth curve is significantly smoother. The chilled carcasses obtained with the HE diets and the ME + coconut oil diet are firmer than those obtained with the ME reference diet (NTEN > 4 vs NTEN = 3.5). It is clear that the higher the growth rate of the lambs through the late fattening period (60 d to slaughtering) the better the fat qualities are, even if they exhibit a compensatory growth. The highest energetic concentration diets do not reduce the energetic deficiency at the beginning of the fattening period (post-weaning period) but bring about a higher internal fat increase in the lightest lambs at the onset of the post-weaning period.