Furanocoumarins in tedera do not affect ruminal fermentation in continuous culture

Abstract

The objective of this study was to investigate the effects of the forage shrub tedera (Bituminaria bituminosa) on nutrient digestibility, rumen microbial fermentation and furanocoumarins degradation in the rusitec. The variables were measured in fermentation liquid on Days 13 and 17 and were compared with a control (lucerne hay). Overall, tedera had greater (P < 0.05) neutral detergent fibre and acid detergent fibre digestibility than lucerne hay on both days of the experiment, but on Day 17 it had lower (P < 0.01) dry matter and crude protein digestibility than lucerne hay. There were no significant differences in concentration of NH3-N and pH between treatments, but NH3-N concentrations in both treatments were lower (P < 0.05) on Day 17 than on Day 13. The concentration of total volatile fatty acids in vessels were not affected by treatments, but the concentration of acetate was lower and acetate-to-propionate ratio higher (P < 0.05) in tedera than lucerne hay on Day 13 of the experiment. Furanocoumarins were detected in the tedera treatment only. Their concentration in the fermentation liquid increased immediately after the addition of the plant material to the fermenter, reaching highest concentrations after 2 h. These concentrations gradually declined over the next two sampling times, but 6 h after the ‘feeding’, they were still detectable in the fermentation liquid. It was concluded that (i) tedera had in vitro digestibility and fermentability variables comparable to lucerne; (ii) furanocoumarins were degraded in the fermentation fluid, and (iii) furanocoumarins from tedera did not seem to impede microbial fermentation. Tedera may provide an alternative feed source to hay and grain for filling the summer–autumn feed gap without negatively affecting nutrient digestibility and rumen microbial fermentation.