Response of broiler chickens to diets containing artificially dried high-moisture maize supplemented with microbial enzymes

Abstract

The effect of feeding high-moisture maize grains dried in the sun or artificially in a forced draught oven at 80, 90 or 100°C for 24 hours and supplemented with microbial enzymes (Avizyme 1502 and Phyzyme XP) on growth performance, visceral organs, tissue protein, enzyme activity and gut development was investigated in a broiler growth trial. Feed intake (FI) up to 21 days decreased as a results of oven drying of grains whereas supplementation with microbial enzymes increased FI compared to the non-enzyme diets (881.1 vs. 817.2 g/bird). The highest FI (900 g/bird) was found only in sun-dried grain diets. There was no effect of grain drying temperature or enzyme supplementation on FI when assessed at 7 days of age. Up to day 21 there was a reduction in live weight (LW) with increase in grain drying temperature while supplementation with enzymes significantly improved LW only on the diets containing sun-dried grains (731 g/bird) and grains dried at 90°C (634 g/bird). Live weight was significantly higher in chickens on the enzyme supplemented diets than on diets without enzymes (638 vs. 547 g/bird). The feed conversion ratio (FCR) at this age was poorer with an increase in grain drying temperature but improved when the diets were supplemented with enzymes (1.48 vs. 1.62 g/g). There was an increase in the relative weight of the small intestine and liver with an increase in grain drying temperature at day 21 but there was no difference in the relative weight of these organs when the diets were supplemented with enzymes. Only the activities of the alkaline phosphatase at day 7 and maltase and sucrase at days 7 and 21 increased as a result of grain drying treatment but not by microbial enzyme supplementation. The ileal digestibility of gross energy, protein and starch was not significantly changed with an increase in grain drying temperature or by enzyme supplementation. The concentrations of ileal formic and acetic acids and caecal propionic and valeric acids were significantly increased by an increase in grain drying temperature but not affected by the microbial enzyme supplementation. The populations of lactic acid and lactobacilli bacteria in the ileal content were reduced on diets containing enzymes but were not affected by an increase in grain drying temperature. In the caecal content, the total anaerobic bacterial count was higher in birds on diets supplemented with microbial enzymes (8.1 vs. 7.8 log10 cfu x/g digesta). The resident lactic acid bacteria population also increased as a result of an increase in grain drying temperature. From results of the current study, diets based on sun-dried maize or maize dried at 90°C provided comparatively better gross response. It may be inferred that there was a positive response to addition of microbial enzymes. Overall, it may be assumed that, for broiler chickens, there is little or no difference in the nutritive value of sun-dried grain and grains artificially dried at 90°C.