Effects of herbage allowance on the intake of churra ewes

Abstract

The effects of two different levels of daily herbage allowance of groups of Churra ewes grazing on plots of a Lolium perenne-Trifolium repens pasture from March to September of 1989 were studied. Estimates of herbage intake were made in four periods (May, early and late July and September) using total faecal collections and “in vitro” organic matter digestibility of samples obtained from oesophageally fistulated ewes. Herbage mass and sward height varied in the range 653-1720 kg OM/ha and 3.4-12,5 cm, respectively. Asymptotic curves describe the relationship between total herbage intake (kg OM/ha) and herbage allowance (g OM/kg LW/day or sward height (cm). Both relations were examined by regression analysis using an equation of the form Y=aXb. Values of coefficient b obtained in each case were -0,20±0.048 (P<0.05) and - 0.40±0.098 (P<0.O5). Furthermore, herbage intake (g OM/kg LW/day) and sward height (cm) were positively correlated (r=0.55, P<0,05) and the value of coefficient b was 0.61±0.213 (P<0.05). The implications of these relations to techniques of grazing management are discussed in relation to better utilisation of lowland areas for extensive sheep production systems.