SUMMARY

The use of alfalfa in diets for monogastric animals is limited by its high fiber content. However, it is well established that alfalfa is a natural source of xanthophylls, giving the poultry carcasses a desirable yellow color. We have investigated the potential use of cellulases and xylanases for enhancing the nutritive value of alfalfa for broiler chicks. In the first experiment, a commercial enzyme mixture and 2 recombinant cellulases and xylanases did not improve daily weight gains and feed efficiency of broilers between 35 and 56 d old, although animal performance was significantly depressed in animals supplemented with a recombinant xylanase. In a second experiment, alfalfa consumption was stimulated by restricting the consumption of the high energy feed to 50 and 75% from d 7 to 56. Alfalfa was offered separately and ad libitum and was supplemented or not with a commercial enzyme cocktail of polysaccharidases. While restriction of high energy feed had a drastic impact on the performance of broiler chicks, no improvements in weight gain and feed efficiency were observed due to enzyme supplementation. However, alfalfa consumption was lower in enzyme-supplemented animals, leading to smaller, but not significant, feed conversion ratios (FCR). Accumulated consumption of alfalfa meal ranged, in average, from 965 to 2,664 g/bird in experiments 1 and 2, respectively. The carcasses from birds with higher alfalfa intakes were more deeply pigmented with an increase in yellowness (b*) of the broiler skin