Effects of diaryliodonium chemicals on rumen fermentation in vitro and in vivo

In vitro fermentation studies demonstrated that diaryliodonium chemicals were inhibitors of amino acid utilization. Only small differences were found in comparative effectiveness of different analogs and salt forms of chemicals tested. Protection against degradation and(or) uptake was greatest for valine, methionine, isoleucine, leucine and phenylalanine. Although changes were not as large, animals fed 4,4'-dimethyldiphenyliodonium chloride for 112 d had higher ruminal concentrations of amino acids and lower concentrations of ammonia. Decreased production of acetate in conjunction with increased production of propionate and butyrate resulted in improved fermentation efficiencies. Fermentative shifts in vivo were not as large as those observed in vitro and additional investigations are needed to determine whether feeding diaryliodonium chemicals increases the transfer of energy in digested carbohydrates to volatile fatty acids.