PSXI-20 Proteic dry supplements enriched with a blend of tannin-based extract enhance the performance of grass-fed cattle during the rainy season in tropical regions

Abstract During the rainy season, utilizing grass-fed cattle is a common and cost-effective approach for fattening in tropical regions. Despite having access to high-quality forage, cattle often require protein-rich supplementation to optimize their performance. This study aimed to evaluate the effectiveness of a commercially available feed additive, SilvaFeed BX (Indunour, Buenos Aires, Argentina), derived from quebracho and chestnut tannin extracts along with saponins, on the performance of grazing beef cattle supplemented during the rainy season (January-May 2023) in tropical region. A total of 465 Nelore or crossbred Nelore-Angus (F1) bullocks were distributed across 14 paddocks of Urocloa brizantha using a completely randomized block design, stratified by initial body weight (BW), at a commercial grass-fed ranch in the northern part of Goias State, Brazil. Each paddock served as an experimental unit, with the number of animals dependent on paddock size, initially stocked at a rate of 2 animal units (AU)/ha based on initial BW. The animals were provided with a supplement (25% CP, DM basis) containing flavomicin (25 ppm/kg supplement) offered daily at 0.5% of BW (Control), or supplemented with a blend of tannins (BX, 3,5 g/kg supplement). Individual BW were recorded at processing and shipment, while carcass weight was measured individually at the packing plant. Carcass gain was calculated as the difference between carcass weight and the estimated initial carcass weight, set at 50% of the initial BW, in accordance with customary practices for negotiating feeder cattle in Brazil. Statistical analysis was conducted using Proc Mixed of SAS, with treatment, breed, and treatment*breed considered as fixed effects, and treatment (paddock) as random. Residuals were evaluated for normality, and mean comparisons were conducted using LSMEANS. The results revealed that BX-treated cattle exhibited significant improvements in most performance traits: average daily gain (ADG; 1.181 vs. 0.842 kg/d, P = 0.0027), total BW gain (127.46 vs. 79.13 kg, P = 0.0205), final BW (FBW; 548.74 vs. 517.94 kg, P = 0.0011), hot carcass weight (HCW; 297.21 vs. 277.84 kg, P = 0.0002), and carcass daily gain (0.785 vs. 0.626 kg/d, P = 0.0035; Table). Although no interaction was observed between treatment and breed, Nelore cattle exhibited heavie initial BW (466.29 vs. 392.92 kg, P = 0.0026) compared with F1 cattle. F1 cattle demonstrated superior performance in ADG (1.216 vs. 0.807, P = 0.0008), total gain (141.26 vs. 65.31, P = 0.0015), and carcass daily gain (0.790 vs. 0.621 kg/d, P = 0.0022). In conclusion, supplements containing a blend of tannins and saponins were found to enhance overall performance traits of finished grass-fed cattle, independent of the breed evaluated.