Desempenho, qualidade da carne e emissões de gases de efeito estufa de bovinos zebuínos e cruzados alimentados com diferentes proporções de concentrado em confinamento

Abstract

Bos taurus indicus and Bos taurus taurus crossbreed has become a valuable alternative on the search to improve performance, meat, and carcass quality. It’s added that the production system adopted, and the diets provided can improve not only animal performance, but also to contribute with a product with healthier characteristics for human healthy. The intensive system of beef cattle production in feedlot has been expanding more and more throughout the tropics, but the impact that this type of system can cause to the environment in tropical regions is uncertain and still requires a lot of investigation. In this sense, we aimed evaluate the intake, performance and meat quality of Nellore and crossbred animals fed diets with two levels of concentrate (85 and 65 %), in addition to evaluating the nitrous oxide (N2O) and methane (CH4) fluxes emitted from these cattle excreta deposited in feedlot soil used in Brazil. To evaluate the impact of genotype and diet on feed intake, performance, and meat quality 23 Nellore with IBW of 377.17 kg ± 4.37 kg and 25 crossbreed with 415.33 kg ± 4.20 kg of IBW were used. The animals were finished in feedlot for 84 days fed with two levels of concentrate in dry matter basis (85 and 65 %). To evaluate the dry matter intake (DMI) using titanium dioxide (TiO2) as an external marker 16 Nellore (eight consuming the 85 % diet and eight consuming the 65 %) and 16 crossbreed animals (eight consuming the 85 % diet and eight consuming the 65 %) were randomly selected. The performance variables body weight (BW), gain weight (GW), average daily gain (ADG), hot carcass weight (HCW), average daily carcass gain (ADGc), feed efficiency and conversion (FE, FC), meat quality variables (color, tenderness, centesimal composition, and fatty acid profile) and N2O and CH4 emission from cattle excreta deposited in soil were evaluated. To evaluating the meat quality variables the same animals selected for the DMI evaluation were used. For the evaluation of N2O and CH4 emissions, fresh excreta (feces and urine) from Nellore and crossbreed cattle were used. Fresh urine and feces were mixed and applied together on the feedlot soil in static chambers installed on the ground of a previously reserved open-air feedlot pen. N2O and CH4 fluxes were monitored for 84 days. The crossbred animals showed greater BW, ADG, HCW and ADGc. There was no difference between breed or diet (P>0.05) in DMI. Both breeds presented lighter color meat compared to the literature. No interaction was observed (P>0.05) between breed or diet in the concentration of saturated, monounsaturated and polyunsaturated fatty acids. Significant interaction was observed (P<0.05) between breed and diet in the sum of unsaturated fatty acids, where crossbred animals fed 85% diet showed greater amount of unsaturated fatty acids. Related to greenhouse gas emissions (GHGs), CH4 emissions were 2.4 times higher in crossbred than in Nellore animals (P<0.039). N2O emissions from excreta were 50.1% lower in animals consuming diet with low compared to high nutritional level. The emission per DMI (E/DMI) and emission per ADG (E/ADG) of CH4 were higher in crossbred compared to Nellore animals, and the E/ADG and E/DMI of N2O of animals fed high nutritional level were 18.2% and 36.1% higher in crossbred compared to Nellore, respectively. The results showed that crossbred animals had a better performance compared to Nellore and both breeds presented a lighter color meat in comparison to the literature. Both breeds and diets showed the ability to change the meat fatty acid profile. Crossbred animals showed higher concentration of unsaturated fatty acid on LT muscle compared to Nellore animals. The diet with 85% concentrate provided a greater amount of unsaturated fatty acid, n-6/n-3 ratio and thrombogenicity index. Despite the concern involving the consumption of beef because of the potential health problems, the fatty acids profile in the LT muscle showed greater amounts of fatty acids that are beneficial to human health. Related to the GHGs emission, crossbred animals consuming diets with more concentrate feed emit more CH4 and N2O in their excreta. These data indicate that the Nellore herd, which id predominant in Brazil, emits lower GHGs than other breeds, and that diets with high concentrate feed inclusion have greater potential to emit GHGs.