Resumo

PEREZ, Aníbal; E, Nestor; PALMA, José  e  F, Claudio. Effect of ractopamine and lysine on lean yield of leaning pigs in the finishing phase. Zootecnia Trop. [online]. 2006, vol.24, n.4, pp.435-455. ISSN 0798-7269.

From a population of one hundred-eighty commercial hybrids pigs, fed diets containing two levels of ractopamine (RAC:0 and 10ppm) and three levels of lisina (Lys:0.95, 1.05 and 1.15%) a sample of  60 animals (10 per treatment, five males and five females) were pulled out at random to evaluate their carcass lean. It was  estimated the lean percentage (EL), and the following variables: backfat depth (cm) at the tenth and last rib (DF10 and DF13), the area of longisimus dorsi muscle, protein (CP) and intramuscular fat (IMF) contents (%), and a calculation of the protein:fat ratio. It was observed an effect between of the level of Lys and RAC (P<0.001) on DF, with lower values for Lys1.15 and RAC10 (1.4 cm) as comparing to Lys0.95 and Lys1.05 with RAC10 (1.73 and 1.68 cm). Also, this treatment showed lower values of DF than the same levels of Lys-RAC0 (2.23, 1.74, and 1.72cm, in the same order of Lys). It was observed an interaction between Lys and RAC (P<0.05) on the CP content, with higher values for Lys1.15-RAC10, going above by 1.36 percentage units (PU) the Lys1.15-RAC0 treatment. The same effect (P<0.001) was observed for the IMF, with the smaller values for Lys1.15-RAC10 (0.98%) as compared to Lys1.15-RAC0 (1.79%) and to 0.95Lys and 1.05Lys with and without RAC (2.35 2.47 2.25 and 3.22%, respectively). Also, an effect (P<0.001) between Lys and RAC was observed on the EL, Lys1.15 (55.75%) was better than Lys1.15-RAC0 (52.32%). It was observed an effect (P<0.001) between Lys and Sex on the EL, with better values in the females as compared to the castrated males (0.41 2.23 and 5 PU for Lys0.95, 1.05 and 1.15%, respectively). An improvement on lean and on decreasing fat in the carcasses was related to both Lys and RAC levels (separately or combined). The agreement of EL values and P:G ratios indicate that P:G ratio could be used as good indicator of lean.

Palavras-chave : Pig; ractopamine; lysine; dressing percentage; average daily gain.