Live performance, carcass characteristic and blood metabolite responses of broilers to two distinct corn types with different extent of grinding
Preparing corn by grinding before incorporating it into a compound diet improves broiler performance (Reece et al., 1986; Lott et al., 1992). Smaller corn particle size has a greater surface area to volume ratio, increasing exposure to digestive enzymes and presumably decreasing energy needed for mechanical digestion (Jurgens, 1993). Feeding large‐particle corn may produce beneficial effects similar to reports of whole grain feeding. Whole grain feeding has been associated with increased gut development and health, that is a heavier muscular gizzard and less occurrence of proventricular dilatation (Jones and Taylor, 2001). Greater development of the broiler gastrointestinal tract suggests that feed may be retained in the upper digestive tract for a longer period allowing for increased enzymatic digestion (Jones and Taylor, 2001; Hetland et al., 2002). Many studies have been published on the broiler responses to varying corn particle size, but with conflicting results. Reece et al. (1986) and Lott et al. (1992) reported improved broiler performance when corn particle size decreased from 1289 to 987 μm and from 1173 to 710 μm respectively. Further decreases (900–300 μm) have also resulted in improved performance (Healy, 1992). In contrast, Nir et al. (1994a) has shown that increasing corn particle size from 525 to 897 μm increased broiler performance. The type of corn used in different studies likely explains the different findings, namely that the feeding value of a particular type of corn is probably related to specific particle size. From the foregoing, it was hypothesized that the optimal extent of grinding of corn may well change with different types.
In the present study, two popular corn hybrids in traditional Chinese farming, a dent type (Ludan No. 50, LD50) containing more floury endosperm and a flint variety (Nongda No. 108, ND108) having more horny endosperm, were assessed for feeding value to broiler chickens when ground into large or small particles, in terms of growth and carcass composition. To expose the underlying causal mechanisms, some relevant metabolites were also measured in plasma.