Replacing whey protein concentrate in a piglet formula is not as easy as it appears to be. Not only the protein contribution of WPC must be matched by other equally digestible ingredients, but secondary aspects such as palatability, pellet quality, and immunoglobulin support must be addressed with equal importance.
By Ioannis Mavromichalis, Ariston Nutrition SL, Madrid, Spain *
Whey protein concentrate (WPC) is a very important ingredient featured in many piglet formulas, sometimes as the only source of milk protein. The crude protein concentration in WPC varies greatly from 30-80%, depending on the level of lactose and ash extraction. The high protein variety, or WPC80, is the most common and will be discussed here. Fierce competition from the human food industry drives worldwide prices for WPC up constantly because this dairy ingredient is used in candy bars (due to its high palatability) and in sports (body-building) supplements (due to its high amino acid digestibility). Thus, alternatives are frequently attempted, but often fail, because the replacement is made on a protein (or amino acids) basis without taking into account the multi-faced attributes of WPC. I will examine these issues in order below.
Highly digestible protein
The protein content of WPC is of extremely high digestibility, which can reach or exceed 90%. It is rich in lysine, threonine, valine, and isoleucine, but relatively low in threonine, methionine and cysteine (Table 1). It is apparent, compared to the requirements of a piglet, that WPC is a near ideal protein with slight deficiencies that can be covered easily by synthetic methionine (which can also cover the cysteine requirement). Thus, when removing WPC from a piglet formula, it is methionine first and tryptophan second in terms of importance.
Alternative proteins that can cover the supply of amino acids offered by WPC include wheat gluten, pea protein, potato protein, soy protein concentrate, and rice protein. Some of these ingredients come with their own problems and as such a blend is often recommended when they are to constitute more than 5% of the total diet. All require careful balancing for amino acids. Varieties exist offering a low concentration in anti-nutritional factors, such as glucoalkaloids in potato protein, and these must always be preferred when inclusion level exceeds 5% of the final diet.
Where still permitted, meat meal, fish meal, and poultry meal can contribute towards meeting the amino acids needed in replacing WPC, but these ingredients can be only of the highest possible quality in order to match the digestibility of WPC protein.
A matter of taste
This is a factor often overlooked when replacing WPC. Vegetable proteins have a very blunt taste, whereas WPC is extremely tasty and palatable. This effect will be more pronounced in formulas where the favourable taste of WPC was masking an unpleasant (perhaps bitter or stale or oxidised) taste derived from other ingredients, including some medicines and other additives. If WPC is the only dairy ingredient used, then another palatable ingredient, such as sucrose, may be used. Failing that, a flavour can be used, but as these products have a tremendous variability in effectiveness, this requires a very careful selection. It should be noted that in most cases, piglets will not taste the difference when diets are based on cooked cereals and extruded soybeans as these ingredients easily mask the taste of other raw materials due to their usual high inclusion rate. Diets rich in oils and fats also do not benefit from changes in perceived ‘taste’ from the addition of palatability enhancers because lipids enhance the taste effect of other palatable ingredients.
This is a hardly known fact, at least outside the feed manufacturing world, but WPC does cause pellets to become harder. A 10% inclusion level of WPC might actually produce pellets so hard that feed intake in weaned piglets can be severely reduced. Of course, this is not a factor in meal diets. Thus, when WPC is removed from a formula, and WPC was the only ingredient enhancing the durability aspects of pellets produced from this formula, care must be taken to replace this attribute from other sources. The easiest way, if the formula contains such ingredient, is to increase the level of wheat against that of other cereals. Perhaps, a small increase in crude fibre should also be considered, in very-low fibre diets, to provide extra strength to the pellets, or at least a pellet binder can be included as a last resort. Failing to account for the drop in pellet quality, when a high concentration of WPC is removed from a piglet formula, can lead to pellet quality deterioration.
Whey protein concentrate contains a residual amount of lactose, which is about 5% in WPC80. If WPC80 is the only source of lactose in a formula, and WPC80 makes more than 5% of the final feed (contributing at least 0.25% lactose), this amount should be replaced with lactose or sucrose. This is unlikely, but it happens. Of course, when a WPC product with lower protein and more lactose is replaced, then the naturally higher lactose contribution should always be compensated. Nevertheless, in most formulas, WPC80 is used for its protein and not its lactose content. As such, and assuming the diet contains a minimal level of lactose from other sources, the lactose contribution of WPC80 is not deemed significant enough to merit replacement.
Enhancing immune system
Few realise that whey, in general, is a source of immunoglobulins. Ingested immunoglobulins offer protection against pathogens in the lumen and as such enhance animal performance. They are found in colostrum and blood for example. Whey powder (11% protein) contains a very low level of immunoglobulins (about 3%), and these bovine immunoglobulins are of a rather weak nature (as they are not specific against piglet pathogens).
Nevertheless, in a concentrated product like WPC, where the protein is as much as seven to eight times higher than in whey powder, the immunoglobulin concentration can easily exceed 20%, and this is not insignificant. When WPC is the only source of immunoglobulins in a diet and it is subsequently replaced by a vegetable protein, then it is logical to expect some drop in performance. The alternative sources of immunoglobulins are animal plasma and hyper-immunised egg protein, both rich but quite different. Plasma is more expensive and of quite variable composition, with a rather generic make up of immunoglobulins. The more sophisticated egg-derived immunoglobulins are less expensive and at the same time more effective as they target pathogens of specific interest during the period around weaning.
Replacing is not easy
Replacing whey protein concentrate in a piglet formula is not as easy as it appears to be in the first place. Not only the protein contribution of this ingredient must be matched by other equally digestible ingredients, but secondary aspects must also be considered.
The issues of palatability, pellet quality, and immunoglobulin support must be addressed with equal importance. For this, the whole diet must be considered and other ingredients and nutrients rebalanced to assure piglet performance and health without sacrificing product quality and sales.
* Ioannis Mavromichalis runs his own nutrition consultancy company. More info:www.ariston-nutrition.com
Feed Tech, Vol. 13 No. 5, 2009
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