A quick look at animal nutrition quickly reveals that most common practices were established when animals were raised using antibiotics as growth promoters in their feeds. For example, we were able to feed high levels of crude protein knowing that excess amino acids, due to unavoidable imbalances, would not cause excessive proliferation of harmful bacteria. When antibiotics are not used in the feed, we have learned that crude protein levels should be minimized, and instead, feed-grade amino acids should be used to balance the protein profile so no large excesses reach the hind gut where those pathogens thrive. Lamentably, this is as far as nutrition has been adjusted in the post-antibiotic era.
There are other areas of nutrition — additives are excluded — that require similar attention. For example, the exact level of amino acids, the ratio between energy and protein (amino acids), also require reevaluation. With a greater bug population, animals are known to require higher levels of nutrients to sustain them. And this involves only the beneficial microflora that also needs some form of fiber, something we are still struggling to understand.
But even ingredients require similar attention to nutrients. For example, without antibiotics to control gut inflammation, are we still comfortable feeding high levels of soybean meal and similar vegetable proteins to very young animals? Or what about sources of lactose and immunoglobulins? Do they require a similar adjustment now that antibiotics are either banned or being frowned upon by governments and consumer/producer groups alike, worldwide?
The post-antibiotic era is not just about adding new additives. It requires new research, if not from scratch, at least from the point of knowing that gut health is no longer enjoying the support of antibiotics. Especially now that zinc and copper, in their mineral forms that control diarrheas, are also under similar persecution with the foreseeable ban of high concentrations in diets for young animals.
It is an interesting time to be a nutritionist.