Effects of Feed Particle Size and Feed Form on Growth Performance, Nutrient Metabolizability and Intestinal Morphology in Broiler Chickens (Report‪)‬

INTRODUCTION Many feed ingredients, especially cereal grains, are ground before they are incorporated into poultry diets. Reduction of feed particle size increases both the number of particles and the surface area per unit volume allowing greater access to digestive enzymes (Goodband et al., 2002). However, studies which relate particle size to digestibility of nutrients are limited, and with somewhat conflicting results. Therefore, this topic is necessary to be further investigated in broilers. Amerah et al. (2007) found that coarse grinding tended to improve the apparent metabolizable energy (AME) in wheat-based diet, but not in maize-based diet. However, earlier research showed that no effect of wheat particle size on the AME (Svihus et al., 2004). Compared with coarse diet, Parsons et al. (2006) reported that fine grinding of maize decreased the efficiency of nitrogen and lysine retention in broilers. The conflicting results showed that fine grinding wheat improved starch digestibility and AME (Peron et al., 2005). Lott et al. (1992) found that coarser grain size reduced performance. However, earlier work showed that bird fed the coarse diets performed better than birds given the fine particle diets (Reece et al., 1985). Feed physical form is one of most important factors, which confound the effect of particle sizes on digestibility of nutrients and growth performance. Pelleting is the most preferred form of diet for broiler chickens, during the starter and grower periods, showing an increased feed intake and weight gain and improved feed to gain ratio (Calet, 1965). Also, pelleting feed for broilers can improve AME and apparent metabolizability of organic matter (Kilburn and Edwards, 2001; Zelenka, 2003; Svihus et al., 2004).