Composition and nutrient utilization by sheep of ensiled tall fescue with different levels of endophyte infection

Abstract

Low and high endophyte infected stockpiled tall fescue was harvested, chopped and ensiled in 210 liter metal drums, double lined with polyethylene bags. Endophyte infection averaged 4 and 70%, respectively, for the low- and high-endophyte fescue. A metabolism trial was conducted with 24 wethers fed diets consisting of 100% low-endophyte fescue silage, 50% low-endophyte and 50% high-endophyte fescue silage, and 100% high-endophyte fescue silage. Chopped alfalfa hay was used as a control forage. Single samples were analyzed, so statistical treatment of chemical composition was not possible. However, certain numerical differences were recorded. Lignin was higher for the high-endophyte than the low-endophyte fescue. Dry matter, CP, and ash were similar for the fescue silages. The high-endophyte fescue silage was lower in P, Mg, S, K, Fe, Cu, Mn, Zn, and Al than the low-endophyte silage. Digestibilities of DM, NDF, and cellulose were higher (P<.01) for fescue silages than alfalfa hay. Level of endophyte infection did not affect digestibility of DM, NDF or cellulose. Among silage treatments, apparent absorption of N, expressed as g/d, showed a linear effect (P<.05), with the lowest value obtained for sheep fed 100% high-endophyte fescue silage. Apparent absorption and retention of Ca were higher for silages than alfalfa. Among the silage diets, apparent absorption of P decreased linearly (P<.01) with increased endophyte level. Apparent absorption of K decreased linearly (P<.01) with increased endophyte level, but the effect was related to intake. Serum prolactin concentrations of the wethers fed fescue silage showed a linear decrease (P<.05) with increased proportion of endophyte-infected fescue. Endophyte infection of fescue appears to affect N and mineral metabolism.