The effects on digestibility, performance and chemical body composition of inclusion of palm oil (PO, VETALGRAS®) or calcium soaps of palm oil fatty acids (CaF, MAGNAPAC®), at two levels, in diets of growing lambs were determined. Experimental diets consisted of barley straw and one of five concentrate supplements: control (C, no fat added), low level of PO (LPO, 25 g PO/kg), low level of CaF (LCaF, 31 g CaF/kg), high level of PO (HPO, 41 g PO/kg) and high level of CaF (HCaF, 50 g CaF/kg). Concentrations of supplemental fatty acids in the diets were 25 and 41 g/kg for the two supplementation levels. Concentrates with added fat were formulated to be isonitrogenous and isoenergetic and the five supplements had the same energy:protein ratio. The experiment was completed with 30 male Ojalada lambs (6 lambs per treatment) from weaning (initial live weight 14.1 ± 0.5 kg) until 25 kg live weight. Inclusion of fat decreased digestibility of acid detergent fibre (0.525 versus 0.438, P 0.05). At the low level of fat inclusion, OM digestibility was greater when fat was in the form of PO than when it was as CaF (0.844 in LPO versus 0.823 in LCaF, P < 0.05). At the high level of fat inclusion, NDF digestibility was greater when fat was included in the form of CaF rather than PO (0.435 in LPO versus 0.500 in HCaF, P < 0.05). Average daily gain (ADG) and days to 25 kg were not affected by the treatments. The feed conversion ratio (FCR, g DMI/g daily gain) was lower (C versus LPO, LCaF, HPO and HCaF, P < 0.05) when fat was added to the diets than control animals (3.21 versus 2.86). The treatments studied produced no differences in carcass yield. Statistically significant differences in chemical composition and energy content of carcass and non-carcass components were not observed. Inclusion of up to 41 g of fat from palm oil or calcium soaps of palm oil fatty acids per kilogram of the concentrate of growing lambs improves EE digestibility and the feed conversion ratio without affecting carcass yield and body chemical composition. Inclusion of palm oil fatty acids as calcium soaps avoided the negative effects on fibre digestibility observed when 41 g PO/kg were added to the diet.

This research was funded by the European Union and the Spanish Science and Technology Commission (Project 1FD97-2007).

12 pages, 6 tables.-- Available online Oct 5, 2005.

Peer reviewed