We all know that egg yolk is rich in fats (energy) and pigments (antioxidants) that help form a new life, the chick. But few may recall that part of the egg yolk sac is engulfed in the gut cavity just before hatching. Why this happens is an open question. Some believe this is to support the newly hatched chick in the first days of life in case nourishment is not available, but chicks in the wild are always born in a season when food is abundant. And we must keep in mind that unlike other newly hatched birds, chicks are fully mobile from day one.
Thus, relying on the high availability of nutrients from the absorbed egg yolk sac, nutritionists have traditionally designed pre-starter diets (the first diet post-hatch) based on simple ingredients like corn and soybean meal, something that would be suitable for an otherwise fully mature gut digestive system. Have they been right in their approach?
When broilers were marketed at 8 weeks of age (or later), any lag in performance, especially during the first couple of days post-hatch, went unnoticed as there was enough time for birds to catch up. Now that market age has dropped down to five weeks, every single day counts. In 2018, the first week corresponds up to 30 percent of the life of a modern broiler, whereas it was only 11 percent in 1978 and 21 percent in 2012. The proper commitment to a good start is very important for the broiler’s entire life.
A readily available source of nutrients
We have taken another look at what happens during the first few days post-hatch, re-evaluating our position that the chick is born with a fully mature digestive system. Many nutritionists have now come to the conclusion that the remaining egg yolk sac is not meant just to prevent starvation, but also to provide a readily available source of nutrients during the time when the digestive system of the chick adapts to natural ingredients — not unlike the weaning time process we encounter in mammals like pigs and calves. In these mammalian species, it is true that the digestive enzymes for any change in nutrition require at least four days to fully adapt (such is the case for the change from lactose to starch in mammals). It is likely something similar is happening in the newly hatched chick that is using the readily available energy from egg yolk fat until its digestive system is fully capable to handle natural energy sources (and the same can be said for other nutrients, and, of course, proteins).
So, with this in mind, we must question the concept of providing modern newly hatched chicks with just a simple corn and soybean meal based diet. Perhaps such a diet appears inexpensive — and traditional — but is it still the best possible for the overall performance of the chick? Does it hamper it by not allowing its digestive system to develop as quickly as possible? And what if a more appropriate diet was designed to not only unlock the process, but even support it? Would the chick then experience enhanced life-long digestive and overall performance? Commercial evidence with super pre-starters indicate that this can be the case, but what nutrients, ingredients and additives to use remains a matter of discussion. The matter remains that modern post-hatch broilers should utilize the energy available from feed and egg yolk reserves to grow more instead of wasting it to make up for aggressive (read: inexpensive) feed ingredients used in feed formulation.
Soybeans in super pre-starter diets
That soybeans and most legumes contain a plethora of anti-nutritional factors (ANF) is a well-known fact. Common storage protein such as glycinin and beta-conglycinin are also known to cause adverse alergenic reactions in certain species. At any rate, all these issues cause multiple forms of damage to the overall process of digestion. They may reduce digestibility of proteins, cause over-secretion of enzymes and mucin, and even damage the architecture of the digestive epithelium, not to mention the triggering of the immune system. Luckily, most of these compounds are heat liable, and this is why we feed thermally processed soybeans and not just plain raw soybeans to all monogastric animals, such as the broiler. Nevertheless, not all ANF are heat liable, and not all are destroyed by the usual heat treatment of normal soybean meal and even extruded full-fat soybeans (because excessive heating reduces protein digestibility by the formation of Maillard reaction compounds). Some small, but apparently significant quantities, remain intact, and this fact has caused nutritionists to restrict or even avoid the use of soybean protein sources in diets for weaned mammals; could the same be true for post-hatch chicks?
Of course, it is possible to obtain soybean protein virtually free of ANF, such as in soy protein isolate — the form of soy protein used in human nutrition supplements. However, such products remain cost-prohibitive and even unavailable for commercial animal feeds. Soy protein concentrate is another alternative that contains minimal ANF, but again cost remains high, and we must keep in mind that broiler production is a low-cost/input enterprise. Thus, these largely purified forms of soybean protein remain rather inaccessible for our purposes.
The same can be said for most highly-digestible proteins, be it from animal or vegetable origin. Not many years ago, most if not all broiler diets contained 5 to 10 percent high quality fish meal. When fish meal became so expensive as to exclude itself from feed formulations, poultry nutritionists resisted its removal until the last possible moment. Even today, some quality fish meal products are used in broiler diets — especially in the first diet post-hatch — perhaps because we need to reduce the ANF contributed by soybean meal through reducing its inclusion rate. Nevertheless, fish meal has its own problems, in addition to being prohibitively expensive at the required high quality.
Enzymes and soybean meal
I have long advocated among the enzyme and probiotic manufacturers the possibility of treating raw soybeans with an enzyme or a cocktail of enzymes to neutralize the ANF of soybeans, most of which are proteins. Perhaps this remains unrealistic for current technology levels, as not all ANF are proteins, and of course a cocktail of enzymes for all ANF could be cost-prohibitive for commercial purposes.
Another approach could be that these enzymes are produced by probiotics (microbes or yeasts) designed specifically for this purpose, but inside the animal gut. According to some experts in this field, such an approach is possible from a technical point of view, but it would require some significant genetic engineering that would create a GMO-type of probiotic — something frowned upon by several regions in the world. And, of course, we have the issue of cost of developing such super-bug that would target all ANF.
Commercial proteases are available to be included in the broiler feed, and evidence indicates a minimal increase in digestibility (2 to 5 percent). Is this because these proteases increase protein digestibility, or because they reduce the negative effect of ANF on innate protein digestibility? Whatever the real mode of action — most likely a combination of the two — the fact remains that enzymes have a role to play in feeding broilers a more suitable form of soybean protein.
Perhaps treating the short-term problem is less costly, but when one considers the lifetime performance of a modern broiler, it is doubtful if we can still afford to lose days of growth potential.
And, finally, we should not forget the readily prepared soybean meal, already treated with enzymes, that is outside the animal. Such products appear to be at least as good as soy protein concentrate and/or fish meal, but the technology and subsequent quality is highly brand-specific and, as such, results remain dependent on the source of the treated soybean meal.
Money better spent
In the end, one has to consider whether money is better spent on quality ingredients that not only prevent but even promote or allow normal gut health and development instead of being spent on additives that may (or may not) contribute to reducing or alleviating the negative effects of less expensive ingredients. Perhaps treating the short-term problem is less costly, but when one considers the lifetime performance of a modern broiler, it is doubtful if we can still afford to lose days of growth potential.
The fact that we need to continue developing the concept of a clean diet — one without ANF — for broiler super pre-starters remain as relevant as ever. Due to cost restrictions, soybean protein must remain the main source of amino acids, but we need to find the right form to minimize the negative effects of endogenous soy ANF. The use of enzymes to treat soybean meal, the least expensive available source of soybean protein, appears to be the most promising one, but the technology remains largely brand-specific.