Egg immunoglobulins (or antibodies) are not a novel ingredient and their use is not a new concept. Pig producers have been adding them to piglet diets since whey was found to be an indispensable ingredient in high-quality piglet feeds. What is new is the current understanding on how immunoglobulins when added in piglet feed can enhance gastrointestinal health and consequently improve feed intake and piglet growth.
By Dr Ioannis Mavromichalis, Ariston Nutrition, Spain
Research conducted with animal plasma, another source of immunoglobulins, has demonstrated
repeatedly that it is indeed the immunoglobulin fraction of this ingredient that is largely responsible for the beneficial effects observed (Figure 1). Recent research with egg-derived immunoglobulins (yet another excellent source of immunoglobulins) has demonstrated (Table 1) that these two ingredients offer similar advantages and they are interchangeable (in their roles, not composition).
In fact, in many parts of the world, egg-derived immunoglobulins are considered superior to animal plasma, not only because they don’t carry the risk of transmitting diseases, but also because they are less expensive and most importantly they have been designed to counteract pathogens specifically troubling young pigs around the period of weaning.
What is still missing, however, is a clear understanding on how egg-derived immunoglobulins should be used as an ingredient within a typical piglet formula. To this end, it is important to understand that egg-derived immunoglobulins enhance the overall health status of the animal at the gastrointestinal level. Research has clearly demonstrated that healthier animals require less complex feed during the first few weeks post-weaning compared with less healthy animals. Also, it is significant to realise that although healthier pigs may thrive on less complex (and consequently less expensive) diets, they require diets of higher density as their feed intake can never match their genetic potential for growth. Putting these two factors together while basing a piglet feed programme on egg-derived immunoglobulins is a new challenge for many nutritionists around the world.Although the underlying scientific basis for the correct application of in-feed immunoglobulins has already been proven, there is still much room for investigation, especially when it comes to practical aspects of feed formulation and field application under commercial conditions. In the mean time, the following critical points, derived from personal experiences of almost ten years working with piglets using egg immunoglobulins in the USA and Europe, are offered for consideration.
Research has demonstrated and practice has proven that the inclusion of immunoglobulins in piglet diets reduces the required lactose concentration for similar animal performance. The exact relationship is currently unknown. Nevertheless, in high lactose diets (above 20%), reduction of up to 10% lactose may be permitted under certain cases, but a more conservative 5% reduction would certainly be worth attempting as a first step. The reduction should be comparatively less in diets already marginal in lactose.
Lactose has a dual role in the life of a recently weaned pig. Not only does it provide the best source of energy for which the piglet is already prepared to digest, but it also provides substrate for the proliferation of the beneficial bacteria in the gut, namely Lactobaccili. As such, a portion of the lactose requirement can never be replaced by other feed-intake enhancing ingredients, such as egg immunoglobulins. Nevertheless, this fraction is relatively small, perhaps less than 2-3% lactose in the final feed.
The well-known adverse effects of soybean meal in piglet diets are closely related with feed intake. As such, the lower the feed intake post-weaning, the lower the level of soybean meal that can be tolerated by piglets. As egg immunoglobulins result in enhanced feed intake, this implies that higher levels of soybean meal can be used in piglet feeds; even in creep diets. As a rule of thumb, the use of egg immunoglobulins can support the increase of soybean meal by 5% in most diets without adverse effects, and even up to 10% in the final diet when the pigs are raised in extremely clean facilities.
In addition to raising the concentration of soybean meal in the diet, other soybean protein sources can be adjusted to reduce cost without sacrificing performance. For example, purified sources of soy protein (such as soy protein concentrate and isolate) can easily be replaced by extruded full-fat soybeans. The latter in turn, can be switched to plain soybean meal. However, not all changes should happen in the same diet during the same formula revision. Better to incorporate changes gradually.
Needless to say, egg immunoglobulins have made animal plasma obsolete, but for marketing reasons a small percentage of animal plasma might be required. First-time users of egg immunoglobulins have found it educational to half the amount of animal plasma in their first formula revisions as a safe-guard against the ‘unknown’.
A word of caution is required here. Animal plasma definitely imparts a positive taste to piglet feed, as all animal ingredients do to a certain degree. This is important when this positive taste masks the taste of other (often bitter) ingredients. Removing animal plasma might unmask those bitter ingredients causing pigs to go off feed quickly. Thus, when replacing animal plasma with egg immunoglobulins, other ingredients should be adjusted accordingly to avoid feed refusal. To this end, a flavour is a very cheap solution.
Feed intake enhancers
Flavours and aromas both aim at enhancing feed intake, and as seen above they might also have a ‘technical’ role in helping mask offensive flavours (and aromas) in the feed. But, in the presence of ingredients that already support an elevated feed intake, their inclusion is questionable.
Such ingredients include lactose (and all dairy products), fish meal, animal plasma, and of course, for the purposes of this discussion, egg immunoglobulins. Again, a certain aroma (more likely to be used than a flavour) might be required for marketing reasons to create or continue brand identity in the market.
In line with the above, certain additives such as those that aim to enhance gastrointestinal health, feed intake, or reduce diarrhoeas, might be excluded or reduced from formulas based on egg immunoglobulins. The specific additives to be adjusted should be studied carefully and their effects or lack thereof should be weighed against their cost.
This is the most difficult proposition to make as most additives are used based on personal experience. Nevertheless, following the general direction that with diets based on egg immunoglobulins feed intake is expected to increase (or not decrease if plasma is replaced), one can identify those additives least useful in a parallel role with these ingredients.
Cost effectiveness and risk
Every change made in a formula should aim for one or both targets, namely reduced ingredient cost or enhanced animal performance. In diet already devoid of animal plasma, the use of egg immunoglobulins will increase feed intake and piglet growth (in most cases; like everything else there are many disparate factors to be taken into account for this discussion to be more than a brief introduction.)
In contrast, when animal plasma is replaced, then reduction of formula cost is the desired outcome and under this understanding other ingredients can and should be adjusted accordingly. Practical information comes with the risk that it might not be applicable under all circumstances. In some cases, it might even be advisable to follow a different route to achieve a similar result. Thus, consulting with an experienced nutritionist is the best advice one can part with, especially when it comes to working with virtually unknown ingredients. Under this understanding, the above recommendations are offered only as examples to stimulate discussion on the topic of egg immunoglobulins.
Source: Pig progress magazine Volume 26. No 10