PSVII-7 Effects of alkali treatment on nutrient content and ergot alkaloid concentration in tall fescue silage

Abstract

Addition of alkaline compounds at harvest may affect in vitro digestion and ergot alkaloid concentrations in endophyte-infected tall fescue silage. Silage (n = 60; 10 replications/treatment) was produced by filling vacuum-sealing plastic bags (35.5 cm by 27.9 cm) with 150 g of K31 tall fescue (DM basis; forage DM=76.9%; 96% endophyte infection rate) harvested in June. Alkalizing agents (CaO and NaOH) were solubilized in water (20% inclusion; wt/wt basis) and added to the forage at inclusion rates of 0%, 1%, 2%, 3%, 4%, and 5% on a dry matter basis. After ensiling for 42 d, forage samples were lyophilized and subsampled for proximate analysis and analysis of ergot alkaloids. A separate subsample was taken for in vitro total disappearance determination, and each sample was replicated in triplicate. Forage quality and digestibility values were calculated on an organic matter basis because organic matter linearly decreased (P < 0.01) as alkali increased. Alkali increased pH linearly (P < 0.01). Forage NDF decreased linearly (P < 0.01) as greater amounts of alkali treatment were included. Crude protein did not differ (P = 0.41) among treatments. In vitro total disappearance (OM basis) increased linearly (P < 0.01) as inclusion of alkali increased. Total ergot alkaloid concentration did not differ (P = 0.62) across treatments. Ergovaline concentration increased linearly (P < 0.01) with increasing alkali inclusion, but remained below established threshold for toxicity in ruminants. Lactic acid concentration responded quadratically (P < 0.01) with the lowest value corresponding to 3% alkali treatment. Acetic acid concentration increased quadratically (P < 0.01) with the highest value occurring during the 1% alkali inclusion. Propionic acid concentration increased linearly (P = 0.02) as alkali inclusion increased. A quadratic effect (P < 0.01) was observed for butyric acid concentration, with a decrease in butyrate above 1% alkali inclusion. Under conditions of this experiment, addition of alkalizing agents increased digestibility of baled tall fescue silage.