Tithonia diversifolia: uso na nutrição e potencial para redução de emissões de gases de efeito estufa em ovinos

The production of food of animal origin contributes with about 14.5% of the total antropogenic greenhouse gas emissions; with enteric emissions and the production of concentrated feed for animals representing 85% of the contribution within the sector. The use of animal feed alternatives that do not compete for resources with human food are necessary for the sustainability of the livestock sector. The objective was to evaluate the influence of Tithonia diversifolia (TD), a shrub forage (Asteracea), with potential for feeding ruminants and mitigating enteric emissions, on CH4 CO2, N2O, NH3 emissions and fermentative parameters of sheep fed of soybean meal, corn grain and tifton 85 hay. First, the in vitro influence of the inclusion of increasing levels of TD (0, 9, 27 and 45% DM basis) in 60:40 diets (roughage: concentrate) was evaluated on the in vitro gas production (IVGP), CH4 production, degradability of organic matter (OMD), microbial biomass synthesis (MB) and fermentative parameters at five incubation times (2, 6, 10, 24 and 96 hours). There was no significant effect (P>0.05) between TD inclusion and IVGP at most incubation times; only at 6h of incubation, the IVGP increased linearly with the inclusion of TD (P<0.05). There were no effects of TD inclusion on CH4 production (mL/gDOM). OMD increased linearly with the inclusion of TD at 6 and 10 h. The TD45% was more degradable than the control diet at 6 h alone. There was a positive regression (p<0.05) between the TD inclusion and the partition factor. The TD45% showed significantly higher PF values than the control. MB also increased linearly (P<0.05) with the TD inclusion. The influence of the diets on in vivo CH4 CO2, N2O, NH3 emissions, apparent digestibility, nitrogen balance and ruminal fermentation parameters of adult male sheep was also evaluated. The inclusion of TD did not influenceed the gas emissions by the sheep, nor the intake of DM, MO, CP or NDF, nonetheless, the ADF intake increased (P<0.05) with the TD inclusion. The digestibility of DM, OM, NDF and ADF was significantly lower (P<0.05) in diets with 27 and 45% TD. There was no significant effect of TD on protein digestibility, nitrogen balance, or on the production of short chain fatty acids. The concentration of ammonia nitrogen decreased with the inclusion of TD and the concentrations of isovalerate and isobutyrate increased in animals fed with the highest content of TD. The results of this in vivo study corroborated some of the results obtained in vitro, however, the predictive power from the in vitro experiment was low. Similar to what was found in the in vitro experiment, the inclusion of TD had no influence on CH4, CO2, N2O and NH3 emissions. However, inclusion of the plant in the diet of sheep had positive effects on the dynamics of protein degradation in the rumen without relevant effects on nitrogen excretion and emission.

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