Efeito do genótipo e da inclusão de óleo de fritura residual sobre o desempenho, qualidade da carne e seu impacto sobre a emissão óxido nitroso no solo de novilhas confinadas

Abstract

This study aimed to evaluate the effect of genotype and the inclusion of residual frying oil on performance, meat quality, and its impact on nitrous oxide emissions from the soil of confined heifers. A total of 20 purebred Nelore heifers with an initial average weight of 321,0 ± 42,2 kg and 20 crossbred heifers (Nelore × Angus) with an initial average weight of 389,6 ± 80,6 kg, all originating from the same production system and with an average age of 15 months, were used. The animals were confined for 105 days and fed diets formulated for an average daily gain of 1,3 kg/day. A completely randomized design in a 2×2 factorial arrangement (genetic group × diet) with ten replicates per treatment was used. Animal performance was evaluated throughout the experiment through regular weighing, and hot carcass weight (HCW) was recorded after slaughter. Individual dry matter intake (DMI) was estimated using titanium dioxide (TiO₂) as an external marker and indigestible neutral detergent fiber (iNDF) as an internal marker. Samples of the Longissimus dorsi (LD) muscle were collected for meat quality analyses (cooking loss, shear force, color, chemical composition, and fatty acid profile). Monitoring of N₂O emissions from fecal decomposition was carried out in an unoccupied confinement pen over a 90-day period using static chambers. Two trials were conducted: one under natural precipitation conditions and another with simulated rainfall (30 mm per day). Data were analyzed using R statistical software. Means of isolated factors were compared by the F-test (P<0,05) when no significant interaction was observed. In cases of significant interaction, comparisons were performed using Tukey’s test (P<0,05). No interaction between genetic group and diet was observed for performance or carcass traits (P>0,05). Crossbred heifers showed higher dry matter intake (DMI) and average daily gain (ADG) compared to Nelore heifers. Regarding meat quality, neither genotype nor diet significantly altered the fatty acid profile of the Longissimus dorsi muscle. Crossbred heifers fed with residual frying oil (RFO) had lower moisture content (69,58%) and higher ether extract content (9,09%) compared to other treatments. The highest N₂O fluxes occurred after the application of excreta to the soil, with peaks associated with moisture resulting from rainfall. However, neither animal genotype nor the inclusion of residual frying oil significantly influenced N₂O emissions. It is concluded that the addition of residual frying oil to the diet does not compromise animal performance and can be used as an alternative energy source, without negatively affecting meat quality or N₂O emissions resulting from fecal decomposition in confinement systems.