Impact of Particle Length of Alfalfa Hay in the Diet of Growing Lambs on Performance, Digestion and Carcass Characteristics (Report‪)‬

INTRODUCTION Pelleted total-mixed rations are increasing in popularity on many sheep enterprises, including those with relatively small flocks. The advantages for sheep production efficiency of a pelleted TMR over feed ingredients provided separately are thought to exist because concentrates and forages are mixed and offered together and are therefore fermented in the rumen simultaneously. Physical characteristics of the forage component of a pelleted TMR are important criteria in the animal's ability to utilize feedstuffs. Altering the physical properties of forages given separately in long or chopped form and in combination with other feeds or ground in a pelleted TMR have been shown to govern the rate of digesta outflow from the rumen, thereby influencing the control of voluntary feed intake, energy utilization and digestibility (Waghorn et al., 1986; Shain et al., 1999; Hadjigeorgiou et al., 2003). The extents of these changes are influenced by fineness of grinding of the forage and the plane of nutrition at which the diet is fed. Several workers (Hunt et al., 1984; Kerley et al., 1985; Mooney and Allen, 1997) indicated that reduction of forage particle length by grinding and pelleting resulted in an increase in voluntary feed intake with variable effects on digestibility. Reduction in particle length of forages did not result in any effect on the pattern of digestion within the alimentary tract of sheep (Hogan and Weston, 1967; Thomson et al., 1972), whereas Woodford and Murphy (1988), Fischer et al. (1994) and Hadjigeorgiou et al. (2003) reported that reduction of particle length decreased DM and fiber digestibility. On the other hand, Moore (1964) found that reduction in particle length increased rate of DM and fiber digestion.