Digestibility of energy and gross energy intake in fresh pastures

Abstract

Several experiments were performed in springstimmer over the period 1982-85 to study the relationships between digestibility of energy (DE), gross energy intake (GEl), acid detergent fibre (ADF) and dry matter (DM) content in pasture.Wether sheep in metabolism pens and fed ad libitum with daily-cut fresh pasture were used. Two plots with different botanical cotTiposiiion were used to provide herbage; one dominated by Lolium perenne and the other by Holcus lanatus.A high correlation (r= -0-91) was observed between DE and ADF. The prediction used a second-order degree polynomial.Gross energy intake and digestibility of energy were scarcely correlated (r = 0-50) when all cases as a whole were considered. Higher correlations between GEI and DE (r = 0-69) were obtained when only data from pastures where Holcus lanatus prevailed were considered, and still higher (/• = 0 91) in those pastures dominated by sown species with DE values lower than 70%.Herbage DM content had a large effect on GEI (r = 0 83) in the pastures dominated by perennial ryegrass with DE higher than 70%, the correlation between DE and GEI being low and negative (r=-036). It is possible, tberefore, to predict apparent digestibility of pasture energy from ADF. However, DE is closely related to GEI only in those pastures in which DE is lower than 70%, DM content being an important factor limiting t Presenl address and correspondence: Dr K. Osoro. Cenlro de Experimentacion Agraria, Apdo 13, 33300 Villaviciosa, Asturias, Spain. the intake of those fresh pastures dominated by jjerennial ryegrass when DE is above 70%. M A M J J A 1982 I I Dead matter AMJ J A S 1983 Clover M J J A 1984 Sown grosses J J A 1985 Figure I. Botanical composition of ofTered herbage in each experimental period.

Utilization ofLolium multiflorumby sheep 1. Influence of dry matter content and correlated factors on voluntary intake

“…Associations of DM content with intake control Sonneveld (1965) and Osoro & Cebrian (1989) maintained that DM intake is strongly correlated with herbage DM content only at low crude fibre and high soluble carbohydrate levels. Normally, high moisture levels will be encountered only in the young actively-growing plant, which should correspond with the conditions discussed above.…”

“…Low dry matter content in young actively-growing pastures may limit intake (Butris & Phillips 1987;Osoro & Cebrian 1989). Verite & Journet (1970) found that, over the range of 12-22% dry matter (DM), intake of dairy cows was related to DM content, with depressions especially noticeable below 18% DM.…”