Lactose plays a crucial role in the growth performance of pigs at weaning because it is a palatable and easily digestible energy source that eases the transition from milk to solid feed. However, the digestibility of lactose declines after weaning due to a reduction in endogenous lactase activity in piglets. As a result, some lactose may be fermented in the gastrointestinal tract of pigs. Fermentation of lactose by intestinal microbiota yields lactic acid and volatile fatty acids, which may positively regulate the intestinal environment and microbiome, resulting in improved gastrointestinal health of weanling pigs. We hypothesize that the prebiotic effect of lactose may play a larger role in weanling pig nutrition as the global feed industry strives to reduce antibiotic usage and pharmacological levels of zinc oxide and supra-nutritional levels of copper. Evidence presented in this review indicates that high dietary lactose improves growth performance of piglets, as well as the growth of beneficial bacteria, particularly Lactobacillus, with the positive effects being more pronounced in the first 2 weeks after weaning. However, the risk of post-weaning diarrhea may increase as pigs get older due to reduced lactase activity, high dietary lactose concentrations, and larger feed intakes, all of which may lead to excessive lactose fermentation in the intestine of the pig. Therefore, dietary lactose levels exert different effects on growth performance and gastrointestinal physiological functions in different feeding phases of weanling pigs. However, no formal recommendation of lactose for weanling pigs has been reported. A meta-analysis approach was used to determine that diets fed to swine should include 20%, 15%, and 0 lactose from d 0–7, d 7–14, and d 14–35 post-weaning, respectively. However, sustainable swine production demands that economics must also be taken into account as lactose and lactose containing ingredients are expensive. Therefore, alternatives to lactose, so called “lactose equivalents” have also been studied in an effort to decrease feed cost while maintaining piglet performance with lower dietary lactose inclusions. In summary, the present review investigated dose-response effects of dietary lactose supplementation to exert positive responses and begin to elucidate its mechanisms of action in post-weaning pig diets. The results may help to replace some or all lactose in the diet of weanling pigs, while improving production economics given the high cost of lactose and availability in some swine production markets.

中文翻译：

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乳糖在断奶仔猪营养中的作用：文献和荟萃分析

乳糖在断奶仔猪的生长性能中起着至关重要的作用，因为它是一种可口且易于消化的能源，可简化从牛奶到固体饲料的过渡。然而，由于仔猪内源性乳糖酶活性的降低，断奶后乳糖的消化率下降。结果，一些乳糖可能会在猪的胃肠道中发酵。肠道菌群对乳糖的发酵会产生乳酸和挥发性脂肪酸，它们可以积极地调节肠道环境和微生物组，从而改善断奶仔猪的肠胃健康。我们假设乳糖的益生元效应可能在断奶仔猪的营养中起更大的作用，因为全球饲料工业努力减少抗生素的使用和氧化锌的药理水平以及超营养铜的水平。该评价提供的证据表明，高日粮乳糖改善了仔猪的生长性能以及有益细菌（尤其是乳酸杆菌）的生长，在断奶后的头两周内其积极作用更为明显。但是，由于乳糖酶活性降低，日粮乳糖浓度高和采食量增加，随着年龄的增长，断奶后腹泻的风险可能会增加，所有这些都可能导致猪肠道中乳糖的过度发酵。因此，日粮乳糖水平对断奶仔猪不同生长阶段的生长性能和胃肠道生理功能有不同的影响。但是，尚未有正式建议对断奶仔猪使用乳糖。荟萃分析法用于确定断奶后第0-7天，第7-14天和第14-35天分别喂猪的日粮应包括20％，15％和0乳糖。然而，由于乳糖和含乳糖成分的价格昂贵，可持续的养猪生产也必须考虑经济因素。因此，还研究了乳糖的替代品，即所谓的“乳糖当量”，以降低饲料成本，同时以较低的日粮乳糖含量保持仔猪的生长性能。综上所述，本综述研究了日粮添加乳糖的剂量反应效应，以发挥积极的反应，并开始阐明其在断奶后猪日粮中的作用机理。该结果可能有助于替代断奶仔猪日粮中的部分或全部乳糖，同时由于某些猪生产市场上乳糖的高成本和可利用性而提高了生产经济性。