184. Effect of a Pool of Essential Oils, Flavonoids and Tannins on Methane Emissions, Production Performances, Ruminal and Blood Parameters in Beef Cattle During Heat Stress Conditions.

Abstract

Reducing methane (CH4) emissions from cattle while improving production efficiency and resilience is essential for achieving sustainable farming. In this light, natural products have gained interest due to their broad-spectrum biological activity. This study evaluated the effects of a blend of essential oils, flavonoids and tannins (EOFT) on CH4 emissions, production performance, ruminal and metabolic parameters in fattening beef cattle, under heat stress conditions. Thirty bulls were blocked by weight and assigned to two groups (3 pens/group, 15 animals/group): Control (CON), basal diet plus placebo (wheat bran; 0.33 g/100 kg live weight), and Treatment (EOFT), basal diet plus the EOFT blend (Anavrin; 0.33 g/100 kg live weight). The trial consisted of 42-days covariate period followed by a 168-day experimental one, from April to early November. Growth and feed intake were evaluated throughout the covariate (d-42 to d0) and the experimental period (d0 to d168). CH4 emissions were measured using a GreenFeed (C-Lock Inc.) unit, applying a rotational approach with weekly pen and group rotation. Blood samples were collected at the beginning (d0), mid-summer (d1) and end (d2) to evaluate metabolic, hepatic and oxidative status. Environmental parameters were continuously monitored and the Temperature Humidity Index (THI) was calculated. At slaughter, carcass weights and ruminal fluid samples were collected for volatile fatty acid (VFA) analysis. Statistical analyses were performed using SAS software, applying specific models for each parameter. The weights at start of the covariate period and at the start of the treatment administration were similar, as were the final and carcass weights (Table 1). Conversely, EOFT showed a significantly higher average daily gain (ADG) (1.267 vs 1.195 kg/head/d) (P < 0.05) (Table 1). The overall dry matter intake (DMI) was similar (Table 1) but it was significantly higher in the EOFT group during summer weeks when THI frequently exceeded 72, indicating heat stress (Figure 1). CH4 production (174.87 vs 195.79 g/day), yield (17.07 vs 19.95 g/kg DMI) and intensity (135.85 vs 160.93 g/kg ADG) were significantly lower in EOFT animals during the experimental period (P < 0.05), while no differences were recorded during the covariate (Table 2). EOFT animals showed improved hepatic and oxidative status during heat stress (d1) and considering the entire fattening period (d2), with lower aspartate aminotransferase and creatine kinase levels and better oxidative status (P < 0.05) (Table 3). Ruminal fermentation was enhanced in EOFT animals, with higher total VFA concentrations (93.87 vs 82.41 mM), including acetate (63.07 vs 55.04 mM) and propionate (19.43 vs 16.41 mM) (P < 0.05). Supplementation with the tested blend of essential oils, flavonoids and tannins reduced CH4 emissions while improving performance and physiological resilience in fattening cattle, indicating improved ruminal efficiency and contributing to more sustainable beef production from environmental, economic and welfare perspectives.

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