通过酵母菌及其副产品预防家禽饲料中的霉菌毒素

通过酵母菌及其副产品预防家禽饲料中的霉菌毒素

Samaneh Azarpajouh兽医师摘编于《World’s Poultry Science Journal》

家禽对各种霉菌毒素都很敏感。酵母菌及其衍生物可用于净化家禽饲料中的霉菌毒素。

禽肉是不断增长的全球人口的最佳蛋白质来源之一。然而，霉菌毒素——一种低分子量的真菌的次级代谢物，是一个与家禽健康和生产性能问题相关的重要的全球性挑战。此外，霉菌毒素是肉品、蛋品及其衍生产品的质量与安全主要威胁因子，控制不当会威胁到公众健康，因此已经成为广告消费者与生产者密切关注的对象。霉菌毒素污染造成的经济损失包括畜禽死亡率上升、生产力下降和额外的管理成本，包括在预防、控制、采样、缓解和额外劳动力等方面投入的成本。

照片来自：Canva

预防霉菌毒素的产生

霉菌毒素的产生可以通过减少霉菌毒素合成基因的表达和抑制真菌的生长来预防。例如，异常毕赤酵母(Pichia anomala)——一种子囊菌和远缘真菌，可以产生2-苯基乙醇，抑制黄曲霉毒素B₁的形成。2-苯基乙醇的作用是降低霉菌毒素生物合成基因的表达。此外，酵母衍生的化合物如耐热克鲁维酵母(Lachancea thermotolerans)通过使用它作为碳源，以生物方式减少和抑制包括赭曲霉毒素A在内的霉菌毒素的合成。此外，赭曲霉毒素A和黄曲霉毒素会被酵母菌产生的挥发性有机化合物灭活。此外，酵母菌能够使用多种抗真菌防御策略，如竞争资源和空间、创造挥发性代谢物、抑制孢子萌发、形成苷酸、生产胞外催化酶，来抑制霉菌毒素的生长。

酵母菌对生长性能的影响

甘露寡糖是由复杂的碳水化合物分子组成，来源于酿酒酵母的细胞外壁。从甘露寡糖中提取的天然碳水化合物部分，可以提高育雏期和生长期肉鸡的生产性能。面包酵母和酿酒酵母是所有酵母中最常见的在其细胞壁中含有β-葡聚糖的酵母。

在日粮中添加酵母和酵母细胞壁提取物，可以改善受到镰刀菌毒挑战的鸡的增重、采食量和饲料转化率。

日粮中添加酵母衍生的碳水化合物可以提高肉鸡的：

☆ 生长性能、

☆ 健康水平、

☆ 免疫系统的功能，以及

☆ 抗炎作用。

日粮酵母培养物，同时添加50 mg/kg、100 mg/kg、150 mg/kg的酶水解酵母细胞壁，可以提高育雏期和生长期肉鸡的平均日增重和饲料转化率，并减少碳足迹，这可能有助于提高养殖场的生产力和盈利能力，有利于环境的可持续发展。

酵母菌对肉鸡免疫系统功能的影响

日粮中的酵母菌培养物：可改变肉鸡免疫系统的功能，如自然和获得性免疫反应。添加酵母可提高鸡新城疫病毒的抗体滴度，提高血清中IgM浓度和十二指肠中分泌性IgA浓度。

此外，日粮酵母能提高血清中溶菌酶的活性，从而激活肉鸡的吞噬现象，以对抗流行的病原体。从甘露寡糖中提取的天然碳水化合物部分增加了空肠中的腺泡细胞面积，增强了粘液蛋白的产生，并增强了对病原体挑战的防御。

补充酵母细胞培养：具有免疫刺激作用，增加上皮内淋巴细胞数和盲肠扁桃体分泌性IgA，以及感染球虫病的鸟类血液和脾脏中CD3⁺、CD4⁺和CD8⁺的活性。添加酵母细胞壁可以降低外周血中的淋巴细胞增殖反应，增加免疫器官的重量，包括法氏囊、脾脏和胸腺，并可上调促炎性细胞因子，如白细胞介素1β和白细胞介素6。

在肉鸡的育雏日粮中加入含甘露寡糖和酵母提取物的混合物：可以增强对传染性法氏囊病和传染性支气管炎病毒的抗体滴度。在日粮中添加来自酵母的碳水化合物，通过辅助T-细胞支持促炎症反应，可改变感染梭状芽孢杆菌的肉鸡的先天免疫力。

● 在日粮中补充甘露寡糖，可以提高体液免疫反应和对禽流感的抗体滴度，并可改变肠道中对诱导细胞免疫反应很重要的基因的表达，如溶菌酶、基膜聚糖、脂蛋白A-1和β2-微球蛋白。

● 在肉鸡日粮中补充β-葡聚糖，可以提高细胞免疫反应，改善受到肠道沙门菌挑战的肉鸡的巨噬细胞的产生和趋化因子的活性。

● 补充酿酒酵母，能诱导降低血浆皮质酮水平，减轻与肉鸡应激反应相关的生理影响。

酵母菌对肠道形态和微生物群的影响

在肉鸡日粮中加入酵母及其衍生物，可以改善肉鸡的肠道形态和环境。

◆ 给受到镰刀菌毒素挑战的鸡群饲喂0.2%的酵母细胞壁提取物，可以增加十二指肠隐窝深度、吞咽细胞数、肠绒毛高度和隐窝深度比。

◆ 日粮中添加酵母β葡聚糖，可增加肉鸡空肠的绒毛高度和隐窝深度比、杯状细胞的数量和分泌型IgA表达细胞。

◆ 在感染艾美耳球虫的鸡的日粮中添加全细胞灭活的季也蒙毕赤酵母（Pichia guilliermondii），可减少艾美耳球虫的卵囊数量，并增加巨噬细胞一氧化氮的活性，提高盲肠扁桃体中白细胞介素-1的浓度。

◆ 日粮中添加酵母菌，可以降低大肠杆菌和沙门菌在球虫挑战后的盲肠微生物群中的比例。

◆ 此外，添加了酵母的日粮可以减少球虫卵囊的数量。

结语

家禽日粮受到霉菌毒素的污染，是影响饲料质量、家禽健康和生产性能以及人类健康的一个全球性的重大挑战。酵母有利于消除霉菌毒素的污染，可以提高钙、磷、蛋白质和纤维的消化率，提高家禽的生长性能，改善动物机体免疫系统功能和肠道微生物群，减少肠道致病微生物的数量，降低家禽的死亡率。

然而，还需要进一步研究，以确定使用该酵母产生最佳益处的合适条件，并确定具有高拮抗性能的新的成本效益型酵母菌株。此外，还需要为食品安全管理系统提供各种工具，以有效区分不同的霉菌毒素。

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Mycotoxin prevention in poultry feeds through yeasts and their by-products

Samaneh Azarpajouh兽医师

Poultry are susceptible to a wide range of mycotoxins. Yeasts and their derivatives can be used for decontamination of mycotoxins in poultry feed.

Poultry meat is one of the best sources of protein for the ever-growing global population. However, mycotoxin, a secondary fungal metabolite with low molecular weight, is a prominent global challenge associated with health and performance issues in poultry. In addition, mycotoxin is a major threat to meat, eggs, and its derived products, thus a major concern for public health. The financial loss due to mycotoxicosis includes increased mortality rate, reduced productivity, and extra management costs including prevention, control, sampling, mitigation, and additional labour.

Prevention of mycotoxin production

Mycotoxins production can be prevented by decreasing the expression of the genes responsible for mycotoxin synthesis and by constraining the growth of the fungi responsible for its formation. For instance, Pichia anomala, a species of ascomycete and teleomorphic fungi, produces 2-phenyl ethanol which inhibits the formation of Aflatoxin B1. The 2-phenyl ethanol acts by the downregulation in the expression of the genes responsible for mycotoxin biosynthesis. Furthermore, yeast-derived compounds such as Lachancea thermotolerans decrease and inhibit the synthesis of mycotoxins including ochratoxin A in a biological way by using it as a carbon source. In addition, ochratoxin A and aflatoxins are deactivated by volatile organic compounds produced by yeasts. Moreover, yeasts use a variety of anti-fungal defence strategies such as competition for resources and space, creation of volatile metabolites, suppression of spore germination, formation of siderophores, and production of extracellular lytic enzymes to suppress the growth of the mycotoxins.

Impact of yeasts on growth performance

Mannan-oligosaccharides are composed of complex carbohydrate molecules derived from the outer cell wall of Saccharomyces cerevisiae. A natural carbohydrate fraction derived from Mannan-oligosaccharides improves performance in the starter and grower phases in broilers. Baker yeast and Brewer’s yeast are the most common among all to have βglucans in their cell wall.

Supplementing yeast and yeast cell wall extracts to the diet enhances the body weight parameters, feed intake, and feed conversion ratio in birds challenged with Fusarium mycotoxicosis.

Supplementation of yeast-derived carbohydrates improves:

• ◆ growth performance,

• ◆ health responses,

• ◆ immune system function, and

• ◆ anti-inflammatory effects in broilers.

Dietary yeast culture plus enzymatically hydrolysed yeast cell wall at levels of 50, 100, 150 mg/kg improve average daily gain and feed efficiency during the starter and grower phases in broilers and reduce carbon footprint, which may contribute to the farm productivity, profitability, and the environmental sustainability.

Impact of yeasts on immune system function

Dietary yeast culture:Modifies the immune system functions such as natural and acquired immune responses. Yeast supplementation increases the antibody titres to Newcastle disease virusand elevated IgM concentration in the serum and secretory IgA concentration in the duodenum.

In addition, dietary yeast enhances the activity of lysozyme content in serum which activates the phagocytosis phenomenon in the broilers to combat the prevailing pathogens. The natural carbohydrate fraction derived from Mannan-oligosaccharides increases the area of goblet cells in the jejunum, enhances mucin production, and augments defence against pathogenic challenges.

Supplementing yeast cell culture: Has immunostimulating effects and increases intraepithelial lymphocytic count, and secretory IgA, and the activity of CD3+, CD4+, and CD8+ in the blood and spleen in coccidiosis-infected birds. Yeast cell wall supplementation decreases the lymphocytic blastogenic response in the peripheral blood, increases the weight of immune organs including the bursa of Fabricius, spleen, and thymus, and upregulates proinflammatory cytokines like interleukin1β and interleukin 6.

Adding a combination of Mannan-oligosaccharides and yeast extract to the broiler’s starter feed:Enhances antibody titres against infectious bursal diseaseand infectious bronchitisvirus. A diet supplemented with yeast-derived carbohydrates transforms the innate immunity in chickens infected with Clostridium perfringens by supporting the pro-inflammatory responses via T-helper cells.

• ◆ Mannan-oligosaccharides supplementation in the diet elevates the humoral immune responses and antibody titres against Avian Influenza and alters the intestinal expression of genes important for inducing cellular immune responses such as lysozyme, lumican, apolipoprotein A-1, and β 2-microglobulin.

• ◆ β-glucans supplementation in diets of broiler increases the cellular immune response and improves the production of macrophages and activity of chemotactic factors in the birds challenged with Salmonella enterica.

• ◆ The Saccharomyces cerevisiae-derived yeast supplementation induces lower plasma corticosterone and mitigates the physiological effects associated with the stress response in broilers.

Impacts of yeasts on gut morphology and microbiota

The inclusion of yeast and its derived products in broiler diets improves gut morphology and environment in broilers.

• ◆ Feeding 0.2% yeast cell wall extract in birds challenged with Fusarium mycotoxin increases duodenal crypt depth, goblet cell counts,villi height, and crypt depth ratio.

• ◆ Dietary supplementation of yeast beta glucans increases the villus height, crypt depth ratio, the number of goblet cells and the secretory IgA-expressing cells in the jejunum.

• ◆ Supplementation of whole cell inactivated Pichia guilliermondii in -challenged birds decreases the Eimeria oocyst count and increases the activity of macrophage nitric oxide and the concentration of interleukin-1 in caecal tonsils.

• ◆ Yeast supplementation decreases the proportion of E. coli and Salmonella in caecal microflora during the post-coccidial challenge.

• ◆ In addition, supplemented diet with yeast reduces the number of coccidial oocysts.

Concluding remarks

Mycotoxin contamination in poultry feed is a major global challenge affecting feed quality, health and performance of poultry, and the public health. Yeast is beneficial to overcoming mycotoxin contamination by increasing digestibility of calcium, phosphorus, protein, and fibre, enhancing the growth performance, improving the immune system function and gut microbiota, reducing the number of pathogenic gut microorganisms, and decreasing poultry mortality.

However, further research is needed to determine the proper conditions that yield the highest benefit from using the yeast and to identify new cost-effective yeast strains with high antagonising performance. In addition, it is required to provide various tools for the food safety management systems to effectively distinguish mycotoxins.

Source:Article – Yeast and derived products: their uses in preventing mycotoxins in poultry feeds Yeast and derived products: their uses in preventing mycotoxins in poultry feeds.Published in the World’s Poultry Science Journal