Ponte P I P, Alves S P, Bessa R J B, Ferreira L M A, Gama L T, Brás J L A, Fontes C M G A, Prates J A M
CIIS - Faculdade de Medicina Veterinária, Pólo Universitário do Alto da Ajuda, Avenida da Universidade Técnica, 1300-477, Lisbon, Portugal.
Poult Sci. 2008 Jan;87(1):80-8. doi: 10.3382/ps.2007-00148.
Over the last centuries, Western diets acquired a dramatic imbalance in the ratio of polyunsaturated fatty acids (PUFA) to saturated fatty acids (SFA) with a concomitant reduction in the dietary proportion of n-3 PUFA. Pastures are a good source of n-3 fatty acids, although the effect of forage intake in the fatty acid profile of meat from free-range chicken remains to be evaluated. In addition, it is unknown if consumer interest in specialty poultry products derived from free-range or organic production systems is accompanied by a greater nutritional quality of these products. In this study, broilers of the RedBro Cou Nu x RedBro M genotype were fed on a cereal-based diet in portable floorless pens located either on subterranean clover (Trifolium subterraneum) or white clover (Trifolium repens) pastures. Control birds were maintained at the same site in identical pens but had no access to pasture. The capacity of ingested forage to modulate broiler meat fatty acid profiles and the meat content of total cholesterol, tocopherols, and tocotrienols was investigated in broiler chicks slaughtered at d 56. The results suggested that pasture intake (<5% DM) had a low impact on the fatty acid and vitamin E homologue profiles of meat from free-range broilers. However, breast meat from birds with free access to pasture presented lower levels of the n-6 and n-3 fatty acid precursors linoleic acid (18:2n-6) and alpha-linolenic acid (18:3n-3), respectively. In spring the levels of eicosapentaenoic acid (20:5n-3) in breast meat were significantly greater in birds consuming pastures, which suggests greater conversion of alpha-linolenic acid into eicosapentaenoic acid in these birds. Finally, when compared with meat from slower-growing genotypes obtained under the conventional European free-range production systems with slaughtering at d 81, meat from birds of the Ross genotype raised intensively and slaughtered at d 35 seemed to have greater nutritional quality.
在过去几个世纪里，西方饮食中多不饱和脂肪酸（PUFA）与饱和脂肪酸（SFA）的比例出现了极大失衡，同时膳食中n-3多不饱和脂肪酸的比例也有所下降。牧场是n-3脂肪酸的良好来源，不过自由放养鸡肉中脂肪酸组成受牧草摄入量的影响仍有待评估。此外，消费者对源自自由放养或有机生产系统的特色禽肉产品的兴趣，是否伴随着这些产品更高的营养品质，目前尚不清楚。在本研究中，将RedBro Cou Nu x RedBro M基因型的肉鸡饲养在位于地下三叶草（Trifolium subterraneum）或白三叶草（Trifolium repens）牧场上的便携式无地板围栏中，以谷物为基础日粮进行饲喂。对照鸡饲养在同一地点相同的围栏中，但无法接触牧场。在第56天屠宰的肉鸡雏鸡中，研究了摄入的牧草对鸡肉脂肪酸组成以及总胆固醇、生育酚和生育三烯酚含量的影响。结果表明，牧草摄入量（<5%干物质）对自由放养肉鸡的脂肪酸和维生素E同系物组成影响较小。然而，能够自由接触牧场的鸡所产鸡胸肉中，n-6和n-3脂肪酸前体亚油酸（18:2n-6）和α-亚麻酸（18:3n-3）的含量分别较低。在春季，食用牧场牧草的鸡所产鸡胸肉中二十碳五烯酸（20:5n-3）的含量显著更高，这表明这些鸡将α-亚麻酸转化为二十碳五烯酸的能力更强。最后，与按照欧洲传统自由放养生产系统饲养、在第81天屠宰的生长较慢基因型肉鸡的肉相比，集约化饲养、在第35天屠宰的罗斯基因型肉鸡的肉似乎具有更高的营养价值。
