CIISA-Faculdade de Medicina Veterinária, Universidade de Lisboa, Pólo Universitário do Alto da Ajuda, Avenida da Universidade Técnica, 1300-477 Lisboa, Portugal.
NZYTech - genes & enzymes - Estrada do Paço do Lumiar, Campus do Lumiar, Edif. E, R/C, 1649-038 Lisboa, Portugal.
Poult Sci. 2018 Dec 1;97(12):4330-4341. doi: 10.3382/ps/pey336.
It is now well established that exogenous β-1,4-xylanases improve the nutritive value of wheat-based diets for poultry. Among other factors, the mechanism of action of exogenous enzymes may involve a microbial route resulting from the generation of prebiotic xylo-oligosaccharides (XOS) in the birds' gastro-intestinal (GI) tract. In a series of three experiments, the effect of XOS on the performance of broilers fed wheat or corn-based diets was investigated. In experiment 1, birds receiving diets supplemented with XOS displayed an increased weight gain (P = 0.08). The capacity of XOS to improve the performance of animals during a longer trial (42 d) was investigated (Experiment 2). The data revealed that diet supplementation with XOS, tested at two incorporation rates (0.1 and 1 g/kg), or with an exogenous β-1,4-xylanase resulted in an increased nutritive value of the wheat-based diet. An improvement in animal performance was accompanied by a shift in the microbial populations colonizing the upper portions of the GI tract. XOS were also able to improve the performance of broilers fed a corn-based diet, although the effects were not apparent at incorporation rates of 10 g/kg. Together these studies suggest that in some cases the capacity of β-1,4-xylanases to improve the nutritive value of wheat-based diets is more related to their ability to produce prebiotic XOS than to their ability to degrade arabinoxylans. The extremely low quantities of XOS used in this study also challenge the depiction of a prebiotic being a quantitatively fermented substrate. These data also bring into question the validity of the "cell wall" mechanism, as XOS elicited an effect with clearly no action on endosperm cell wall integrity and yet the performance effects noted were equivalent or superior to the added enzymes.
现在已经证实，外源β-1,4-木聚糖酶可以提高家禽小麦日粮的营养价值。在其他因素中，外源酶的作用机制可能涉及微生物途径，这是由于在鸟类的胃肠道中产生了益生元木二糖（XOS）。在一系列的三项实验中，研究了 XOS 对饲喂小麦或玉米日粮的肉鸡性能的影响。在实验 1 中，饲喂添加 XOS 的日粮的鸟类表现出体重增加（P=0.08）。研究了 XOS 在更长时间试验（42 天）中提高动物性能的能力（实验 2）。数据表明，以两种添加率（0.1 和 1 g/kg）或添加外源β-1,4-木聚糖酶添加 XOS 的日粮，提高了小麦日粮的营养价值。动物性能的提高伴随着胃肠道上部定植微生物种群的变化。XOS 还能够改善饲喂玉米日粮的肉鸡的性能，尽管在添加率为 10 g/kg 时效果不明显。这些研究表明，在某些情况下，β-1,4-木聚糖酶提高小麦日粮营养价值的能力与其产生益生元 XOS 的能力比其降解阿拉伯木聚糖的能力更为相关。本研究中使用的 XOS 数量极低，也对描述一种益生元是一种定量发酵底物提出了挑战。这些数据还对“细胞壁”机制的有效性提出了质疑，因为 XOS 产生了一种明显不会影响胚乳细胞壁完整性的作用，但所注意到的性能影响与添加的酶相当或优于添加的酶。
