市场上酵母产品很多，但关于使用酵母产品的风险和收益的有效信息却很少。
我最近的一篇博客“尼斯营养家对酵母的了解地这么少”发表后，我收到了酵母供应商的许多反馈，他们都尝试解释它们产品的不同和独特之处。尽管从营养专业供应商那里得到更多的信息，但我还是要帮助购买者列出一系列询问供应商的问题，但是还没有完成。我希望酵母供应商们能够站出来解释这些让营养家们困扰的问题。由于清单所示问题来自世界各地，有些问题可能在一些国家比较普遍，但其它国家可能不常出现。当然，这并不是一个调查报告，仅利用博客的影响，将我个人及他人经验结合。
1、为什么不使用啤酒酵母？
很早以前酵母相关派生物产品就非常流行，啤酒酵母被认为是提高适口性和消化率最优质的原料。但为什么今天它不再流行？
2、为什么啤酒酵母消失了？
换句话讲，为什么啤酒酵母不再昂贵？部分供应商解释现在的产品为酵母派生物，但这过于简单。真正发生了什么？乳制品行业是罪魁祸首吗？因为我们都知道，世界范围内奶牛消耗了相当多的这种酵母产品。
3、死或活？
如果我们已经对各种死亡或活性酵母产品作相应比较的话，我们就应该可以挑选出一种相对便宜的酵母品种？活酵母能够提供更多的好处？换句话讲，活酵母在肠道内生长、繁殖是否能够延长其效果？有没有并发风险？毕竟酵母是肠道中有生命地外星人。
4、酵母能够刺激免疫系统？
在大多数情况下确实如此，但何种情况下这种刺激会成为一种风险呢？错误时间（疾病暴发期、热应激等）过度刺激是否会对动物起反作用？如部分人所认为的，可能酵母最适于成年动物日粮。但是，我们能够利用这种免疫刺激吗？如果可以，那又是何时、如何利用？
5、哪种产品最好？
当可选择的产品众多时，找出最好的那个便成为难题。选择酵母产品的标准是什么？蛋白质？下一个能够评估这些产品质量的指标又是什么？
6、为什么添加比例差异这么大？
如果酵母用作蛋白来源，终产品中的添加量为5-10%；但如果作为一种功能性物质使用时，其添加量将低于这个水平的10倍。那么过量添加时也能获得这种功能性吗？酵母不是酵母？
7、酵母可来自中国、巴西或者世界任何一个地方？
如果酵母还是酵母，那么它的来源地没有关系吗？目前，并没有区别不同酵母的现实质量控制标准。粗蛋白远远不够。酵母的来源是不是很重要？动物饲用酵母与其它工业产生的酵母副产品是否存在不同？
总结
简单来讲，酵母生产方法、来源、营养组成、质量标准对营养家仍然未知。使用者们都是按照产品标签说明来使用这些产品。这是远远不够的。在花钱之前我们需要更多地理解这种产品。有些竞争对手已经在这些方面领先了！
附原文：
7 questions to ask your animal feed yeast supplier
With so many yeast products available, it is surprising how little information is available about yeast risks and benefits.
Following one of my recent blogs,?Ioannis the nutritionist knows so little about yeast , I received many responses from yeast suppliers trying to explain the differences and unique points of their products. Even more messages were received by nutrition professionals, and this led me to create a list of questions that interested parties would like to ask yeast suppliers, but have not done yet.
I hope that yeast suppliers will decide to address these points of disconcert among nutrition professionals. As the list encompasses questions from an international background, some might be more relevant to certain parts of the world than others. Of course, this is not a poll report, but merely blending my own experiences with those around the world, taking advantage of the great reaction affected by the blog.
1. Why not use brewer's yeast?
Long before yeast “derivative” products became fashionable, brewer's yeast was considered a premium ingredient used to increase palatability and digestibility. Why is brewer's yeast no longer considered a prime ingredient any longer?
2. Why has brewer's yeast disappeared?
Or, in other words, why is it so expensive any more? Some have suggested it is being repackaged as yeast derivative products, but this is simply an oversimplification. What really happened? Is the dairy industry the culprit here? We all know dairy cows do consume considerable quantities of such yeast worldwide.
3. Dead or alive?
If we have, and research says we do, comparable results with either dead or live yeast, then should we pick the one that is least expensive? Does live yeast offer further benefits down the road? In other words, does live yeast grow and multiply in the gut offering prolonged benefits? Are there any risks associated with that? After all, it is one more alien and alive microorganism in the gut!
4. Does yeast stimulate the immune system?
In most cases it does, but when is this stimulation a risky proposition? Can overstimulation at the wrong time （disease outbreak, stress due to heat, etc.） cause animals to react negatively? As some mention, perhaps yeast is best left for adult animal diets. On the other hand, can we take advantage of this immune system stimulation, and if yes, when and how?
5. Which product is best?
With the plethora of?yeast products available , one is at a disadvantage trying to find what works best. What are the criteria in selecting a yeast product? Could protein be such criterion, and if not, what is the next readily recognizable and easy to assess index measurement?
6. Why do inclusion rates differ so much?
If “nutritional” yeast used for protein is used at 5 to 10 percent in the final feed, and “functional” yeast at ten times less this concentration, then do we also get the functional benefits from the oversupply of nutritional yeast? Isn't yeast just yeast?
7. Yeast from China, Brazil, or anywhere in the world?
If yeast is yeast, then does it matter where it is coming from? At the moment, users have no real quality control criteria to distinguish one yeast source from the other. Crude protein is simply not enough. Does the process from which yeast is derived play a role? Is yeast produced for animals any different from yeast produced as a by-product from another industry?
Summing up
In brief, yeast production methods, sources, nutrient profiles and quality criteria remain largely a “black box” for nutrition professionals. Such users are called to use a specific product based on its brand name and a number of trials presented to them. This is simply not enough. We need to understand yeast much better before we can place our euros/dollars/yen, etc., on one more expensive ingredient with nutritional and functional properties. Competitors are already ahead!
