THE RELATIONSHIP BETWEEN VOLUNTARY INTAKE AND THE PHYSICAL PROPERTIES OF FORAGES

Abstract

Twenty male sheep (38.4 ± 0.2 kg body weight) were used to study physical and chemical properties of hays affecting voluntary intake. Of the eight forages studied, four were pure cultivars and four were mixed hays obtained from local farmers. Packed volume, water retention and dry matter (DM) solubility were determined in samples either chopped (as fed) or ground (20 mesh). Packed volume and DM solubility of the ground samples were highly correlated with voluntary intake values for each hay (r = −0.97 and r = 0.94 for packed volume and DM solubility, respectively, n = 8, P < 0.01). The intake of each sheep could also be predicted, although less accurately, from DM solubility values (r = 0.87, n = 40, P < 0.01). The soluble fraction contained mainly nitrogen, simple sugars and minerals. The significance of bulk volume and solubility of hays in the physiological mechanism controlling voluntary intake is discussed. Key words: Forage evaluation, forage intake, sheep