Abstract

Rumen concentrations of the undesirable phenol flavour compounds 4-methylphenol, 3-methylphenol, and phenol, were measured in pooled samples from six rumen-fistulated Romney wethers. Samples were collected at approximately 1 hr intervals for 8 hr after feeding white clover (WC), perennial ryegrass (PRG), or Lotus corniculatus (LC). For all three phenols, the time-course curves for the rumen concentration differed significantly between the three diets (P<0.001) with wide differences in maximum concentrations. For 4-methylphenol, concentrations normalised to crude protein intake (CPI) were very similar. Concentrations of phenol normalised to CPI were very similar for PRG and WC diets but much lower for the LC diet. No 3-methylphenol was detected in the rumen of WC-fed animals. For animals fed the PRG and LC diets, concentrations of 3-methylphenol normalised to acid detergent fibre intake were similar. Differences were also observed in the time to maximum concentration after the commencement of feeding, which was much shorter for 4-methylphenol and phenol (2-3.5 hr) than for 3-methylphenol (6 hr). This study established that feeding different forages resulted in differences in phenol metabolism in the rumen, and provides evidence that 4-methylphenol and 3-methylphenol derive from different dietary sources.

K, Fraser, GA Lane, NM Schreurs, MH Tavendale, WC McNabb, and DM Marotti

Proceedings of the New Zealand Society of Animal Production, Volume 63, Queenstown, 40-44, 2003