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Use of Cellulases and Xylanases to Supplement Diets Containing Alfalfa for Broiler Chicks: Effects on Bird Performance and Skin Color

P. I. P. Ponte^*, L. M. A. Ferreira^*, M. A. C. Soares, M. A. N. M. Aguiar^*, J. P. C. Lemos^*, I. Mendes and C. M. G. A. Fontes^*

^* CIISA - Faculdade de Medicina Veterinária, Pólo Universitário do Alto da Ajuda, Rua Prof. Cid dos Santos, 1300-477 Lisboa, Portugal
Instituto Superior de Agronomia, Tapada da Ajuda, 1349-017 Lisboa, Portugal
Estação Zootécnica Nacional, Fonte Boa, 2005-048 Vale de Santarém, Portugal

Correspondence: C. M. G. A. Fontes, E-mail: cafontes{at}fmv.utl.pt

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.

Key Words: alfalfa • cellulase and xylanase • skin color • broiler

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