This work was carried out to evaluate the effect of soya and linseed on the chemical composition and fatty acid profi le of the Longissimus muscle of crossbred bulls fi nished in feedlot. Twenty-one crossbred bulls (1/2 Nelore vs 1/2 Simmenthal), at an average age of 18 months were used in a completely randomized design, with three treatments and seven repetitions. The dietary treatments were: control (CON), linseed and soyabean (SOYA), and soyabean and linseed added after the 60 th day of the experiment (LIN). No difference (P>0.05) was observed among the treatments on the chemical composition of the Longissimus muscle. The values of conjugated linoleic acid (18:2-c-9, t-11) were higher (P<0.05) in the LIN (0.39%) and SOYA (0.46%) treatment, as compared with the CON treatment (0.26%). n-3 PUFA values were higher (P<0.05) in the LIN treatment (1.58%) as compared with the CON treatment (0.83%).

A maioria dos animais de produção é alimentada à vontade, ou seja, tem livre acesso ao alimento na maior parte do tempo. Para que a produção seja eficiente é necessário elevar o nível de consumo voluntário, pois em geral, quanto mais o animal come, mais ele produz e se torna mais eficiente. A amplitude da ingestão é direcionada pela exigência nutricional e uma estimativa aproximada de quantidade de alimento que um animal vai ingerir pode ser calculada pela exigência de proteína, energia e outros nutrientes para a mantença e produção. No entanto, há vários fatores que podem interferir com a concordância entre exigência e ingestão, como o volume do alimento, que pode ser um fator determinante no nível de ingestão alcançada, especialmente nos ruminantes.

This experiment was carried out to evaluate the carcass characteristics, chemical composition and fatty acid profile of the longissimus muscle of 32 young bulls from four genetic groups: Caracu; Canchin; Aberdeen Angus × Canchin; and Charolais × Caracu, finished in feedlot and slaughtered at 22 months old. Each group was composed of eight animals. There was no difference for moisture, ash, crude protein or total cholesterol between bulls from different genetic groups. However, total lipids percentage was higher for bulls from Caracu and Aberdeen Angus × Canchin and lower for Canchin and Charolais genetic groups. Polyunsaturated fattty acids and n-6 percentage was higher for Canchin and lower for Caracu, Aberdeen Angus × Canchin and Charolais genetic groups. Canchin and Charolais × Caracu genetic groups presented higher n-3 percentage than Caracu and Aberdeen Angus × Canchin. There was no difference for the n-6/n-3 ratio among the bulls from the four genetic groups

This study was carried out to evaluate carcass characteristics, chemical and fatty acid composition of the Longissimus muscle of 78 Purunã bulls (39 bulls/treatment) slaughtered at 18 or 24 months old. The experimental design was completely randomized. The bulls were distributed into two systems: 1) Finished in feedlot 13 to 18 months old (T18), or 2) Finished in feedlot from 21 to 24 months old (T24). The diet, roughage:concentrate ratio of 52:48 (dry matter basis), contained 12% crude protein and 72% total digestible nutrients. The T18 system showed lower (p < 0.05) conformation (12.46 vs. 13.41 points), higher (p < 0.05) subcutaneous fat thickness (3.82 vs. 3.11 mm), lower (p < 0.05) Longissimus area (66.17 vs. 70.87 cm 2), lower (p < 0.05) muscle percentage (60.64 vs. 64.26%) and higher (p < 0.05) fat percentage (23.56 vs. 20.00%). Moisture (73.27%), ash (1.05%), crude protein percentages (22.56%) and total cholesterol content (36.47 mg/100 g of muscle) were similar (p < 0.05) between both slaughter ages. The total lipid percentage was higher (p < 0.05) for the T18 system (1.61 vs. 1.33%). Longissimus muscle fatty acid composition was not influenced (p < 0.05), with exception of C18:1 n-9 and C18:3 n-3, which were lower (p < 0.05) for the T18 system. Saturated fatty acids, monounsaturated fatty acids, polyunsaturated fatty acids, n-6, n-3 percentage and PUFA/SFA and n-6/n-3 ratio did not change (p < 0.05) according to slaughter age.

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