Effects of patulin on rumen microbial fermentation in continuous culture fermenters

Eight single-flow continuous culture fermenters were used to study the effects of different concentrations of patulin on rumen microbial fermentation. Two 11 fermenters were spiked with 0, 30, 60 or 90 mg of patulin every 12 h for 3 consecutive days. True digestion of organic matter (TOM), acid detergent fiber (ADF) and crude protein (CP) decreased (P < 0.05, P < 0.01 and P < 0.01, respectively) with patulin addition ranging from 30 to 90 mg. Bacterial nitrogen flow was lower (P < 0.01) with patulin addition (30-90 mg) compared with the control treatment, whereas, the efficiency of bacterial growth (g of N/kg OMTD) was lowest (P < 0.05) when 90 mg of patulin were added to fermenter flasks. Total volatile fatty acid (VFA) concentration (mM) in fermenter effluents decreased (P < 0.05) from 180.1 to 119.5 with the addition of 90 mg of patulin but did not differ (P > 0.05) between the control treatment and 30-60 mg of patulin. Acetate (mol/100 mol) was depressed (P < 0.01) with patulin addition. Conversely, there was an increase (P < 0.05) in the molar proportion of butyrate and valerate in the fermenters treated with the toxin. At the highest level of patulin addition (60 and 90 mg), branched-chain VFA were lower (P < 0.01) probably due to a reduction in protein (branched-chain amino acid) degradation. It is concluded that patulin can alter metabolism of nutrients by ruminal microbes. These changes could potentially have a negative impact on animal health and performance.