The ensiling of high-protein forages often results in extensive proteolysis and poor fermentation quality, which may impair the voluntary feed intake of ruminants. Therefore, the present study evaluated the effects of different hydrolysable tannin (HT) extract and dry matter (DM) levels on preference and short-term dry matter intake (DMI) of grass and legume silages by goats. Accordingly, pure stands of lucerne ( Medicago sativa L.), Italian ryegrass ( Lolium multiflorum L.) and red clover ( Trifolium pratense L.) were wilted to approximately 200 or 350 g/kg DM and ensiled with three HT levels (0, 20 and 40 g/kg on DM basis), resulting in six treatments per forage species. After opening, silages were analysed for chemical composition and fermentation characteristics. Forage preference and short-term DMI were examined in three independent trials using adult Saanen type wethers in a free-choice design. Each possible two-way combination of the six silage treatments and a lucerne hay was offered for 3 h daily. Increasing DM concentration consistently enhanced DMI and preference across all forage species. Supplementation with 40 g HT/kg DM generally improved DMI of low DM silages, but a comparable effect was not observed in high DM silages. The DMI was negatively correlated with most fermentation products, particularly acetic acid, propionic acid, butyric acid, propanol, butanol and ammonia-nitrogen. In contrast, residual water-soluble carbohydrates and in vitro gas production after two hours of incubation were positively related to DMI.
Hilgers et al. (Mon,) studied this question.