Effects of feeding mycotoxin-contaminated diets and the use of a yeast cell wall extracts mycotoxin adsorbent on ruminal and fecal microbiota of finishing beef steers

Luis Henrique Cursino Batista^1,2Yury Tatiana Granja-Salcedo³Igor Machado Ferreira^1,2*Mailza Gonçalves de Souza¹Mateus José Inácio de Abreu^1,2Luiz Fernando Costa E Silva⁴Anne Koontz⁵Vaughn Barry Holder⁵James Eugene Pettigrew⁶Gustavo Rezende Siqueira^1,2Flávio Dutra de Resende^1,2

• ¹Universidade Estadual Paulista Julio de Mesquita Filho Faculdade de Ciencias Agrarias e Veterinarias, Jaboticabal, Brazil
• ²Agencia Paulista de Tecnologia dos Agronegocios, São Paulo, Brazil
• ³Corporacion Colombiana de Investigacion Agropecuaria (AGROSAVIA), Centro de Investigacion el Nus, Corregimiento San Jose del Nus, San Roque, Antioquia, Colombia, San Roque, Colombia
• ⁴Alltech do Brasil Agroindustrial Ltda, Maringá, Brazil
• ⁵Alltech Inc, Nicholasville, United States
• ⁶Pettigrew Research Services, Tubac, Arizona, USA, Tubac, United States

This study evaluated the effects of contamination of the beef cattle diet with mycotoxins and the use of yeast cell wall extract based mycotoxin adsorbent (YCWE) on the ruminal and fecal microbial communities. Eight rumen-cannulated Nellore steers [initial body weight (BW) = 417 ± 42 kg; ± 36 month of age] were used in a 4 × 4 replicated Latin square design. A 2 × 2 factorial treatment structure was used to investigate the effects of mycotoxin contamination of the diet, the addition of YCWE and their interactions. The dietary treatments consisted of: (1) diet without mycotoxins (CTRL), and (2) control diet with added mycotoxins (MYCOT). The second factor was: (1) absence (YCWE-) or (2) presence (YCWE+) of YCWE. The addition of YCWE to the diets was 1 g/kg of dry matter (DM). In the rumen, MYCOT increased microbial richness and diversity indices (P < 0.01), whereas YCWE decreased richness but increased diversity (P < 0.01). MYCOT contamination also increased the relative abundance of taxa associated with inefficient nitrogen utilization (P < 0.08). YCWE supplementation affected several microbial groups, reducing the abundance of methanogenic archaea and acetate-producing bacteria (P < 0.02). Predicted metabolic pathways indicated that MYCOT impaired several functions related to microbial growth and protein synthesis, while YCWE supplementation in contaminated diets partially restored pathways such as purine and pyrimidine metabolism (P < 0.05). However, YCWE supplementation in uncontaminated diets reduced pathways linked to protein synthesis (P < 0.05). In feces, MYCOT and YCWE had no effects on richness (P > 0.10), although MYCOT increased diversity (P = 0.01). Treatment effects on predicted metabolic pathways of fecal microbiota were minimal, suggesting a low impact of MYCOT on fecal microorganisms (P > 0.10). In conclusion, contamination of beef cattle diets with multiple mycotoxins altered ruminal and fecal microbial richness, diversity, and metabolic pathways, potentially reducing microbial growth and protein synthesis. YCWE mitigated several of these adverse effects, contributing to partial recovery of disrupted metabolic pathways. This study provides evidence that YCWE counteracts the antimicrobial effects of mycotoxins, offering a practical nutritional strategy to preserve rumen functionality.