Ponte P I P, Rosado C M C, Crespo J P, Crespo D G, Mourão J L, Chaveiro-Soares M A, Brás J L A, Mendes I, Gama L T, Prates J A M, Ferreira L M A, Fontes C M G A
CIISA - Faculdade de Medicina Veterinária, Pólo Universitário do Alto da Ajuda, Avenida da Universidade Técnica, 1300-477, Lisbon, Portugal.
Poult Sci. 2008 Jan;87(1):71-9. doi: 10.3382/ps.2007-00147.
Free-range chickens are assumed to consume low to moderate levels of pasture, although the effects of forage intake in broiler performance and poultry meat quality remain to be established. In addition, despite cellulases and hemicellulases being widely used as feed supplements to improve the nutritive value of cereal-based diets for fast-growing broilers, the potential interest of these biocatalysts in the production of free-range chicken is yet to be established. In this study, broilers of the RedBro Cou Nu x RedBro M genotype were fed a cereal-based diet in portable floorless pens located either on a rainfed subterranean clover (Trifolium subterraneum) pasture or on an irrigated white clover (Trifolium repens) pasture. Control birds were maintained at the same site in identical pens but with no access to pastures. The importance of pasture intake and enzyme supplementation in the performance and meat sensory properties of the free-range chicken from d 28 to 56 was investigated. The results revealed that although cellulase and hemicellulase supplementation had no impact on broiler performance (P > 0.05), birds foraging on legume-based pastures reached significantly greater final BW. The data suggest that the improvement in broiler performance results from increased intake of the cereal-based feed rather than from an improvement in the efficiency of nutrient utilization per se. Interestingly, although the intake of the subterranean clover pasture had no impact on the tenderness, juiciness, and flavor of broiler meat, members of a 30-person consumer panel classified the meat from grazing broilers with greater scores for overall appreciation. Together, the results suggest that pasture intake promotes bird performance while contributing to the production of broiler meat with preferred sensory attributes.
一般认为，散养鸡消耗的牧草量较低至中等，不过牧草摄入量对肉鸡生长性能和禽肉品质的影响仍有待确定。此外，尽管纤维素酶和半纤维素酶作为饲料添加剂被广泛用于提高快速生长肉鸡的谷物型日粮营养价值，但这些生物催化剂在散养鸡生产中的潜在价值尚未明确。在本研究中，将RedBro Cou Nu x RedBro M基因型的肉鸡饲养在位于雨养地下三叶草（Trifolium subterraneum）牧场或灌溉白三叶草（Trifolium repens）牧场上的便携式无地面围栏中，饲喂谷物型日粮。对照鸡饲养在同一地点的相同围栏中，但无法进入牧场。研究了从第28天到第56天，牧草摄入量和酶添加对散养鸡生长性能和肉品感官特性的重要性。结果显示，虽然添加纤维素酶和半纤维素酶对肉鸡生长性能没有影响（P>0.05），但在豆科牧草上觅食的鸡最终体重显著更高。数据表明，肉鸡生长性能的改善源于谷物型饲料摄入量的增加，而非营养物质利用效率本身的提高。有趣的是，尽管地下三叶草牧场的摄入量对肉鸡的嫩度、多汁性和风味没有影响，但一个30人的消费者小组对放牧肉鸡的肉品总体评价得分更高。综合来看，结果表明牧草摄入可促进鸡的生长性能，同时有助于生产出具有理想感官特性的肉鸡。
