The use of polyethylene glycol to reduce the anti-nutritional effects of tannins in Cistus ladanifer L.

Aim of study: To evaluate the impact of Cistus ladanifer L. (rockrose) tannins on ruminal degradability and fermentation characteristics and the use of polyethylene glycol (PEG), as feed additive, to mitigate the anti-nutritional effects of rockrose tannins. Material and methods: Aerial parts of rockrose plants were harvested in March, freeze dried and divided in 4 subsamples which were treated with 0, 25, 50 and 75 g of PEG/kg of dry matter (DM). The mixtures were analysed for chemical composition including total phenolics, total tannins and condensed tannins. In situ rumen organic matter (OM) and N rumen degradability was evaluated using three rumen-cannulated rams and ruminal fermentation pattern (volatile fatty acids (VFA), gas production) was evaluated in vitro using a Rumen Simulation Technique (RUSITEC) apparatus. Main results: In situ experiment indicated that the effective degradability of the OM and N increased linearly (p<0.05) with PEG inclusion due to an increase of the degradation rate (p<0.05). RUSITEC data indicated that substrate disappearance and gas and VFA production increased linearly (p<0.05) with PEG inclusion. Research highlights: Inclusion of PEG to C. ladanifer feed was effective to prevent the anti-nutritive effects of tannins. Thus, the use of PEG as feed additive can promote a better utilization of this shrub by ruminants.