Enzyme Supplementation in pig diets

It is now accepted that weaning simultaneously subjects piglets to nutritional (e.g. loss of sow´s milk), psychological (e.g. mixing and moving) and environmental (e.g. change in ambient temperature) stressors and that these and other stressors contribute to growth depression typically observed immediately after weaning.  Reducing this post-weaning growth lag is critical as it not only affects performance in the nursery but right through to marketing. Good barn management is one of the most effective strategies for reducing post-weaning growth lag. However, intestinal disturbances associated with immature gut development or pathogen proliferation can still occur despite our best efforts. Because of this, combining a well designed and implemented nutritional program with good management can be the most effective strategy for maximizing nursery and thus overall performance.

As mentioned above, intestinal disturbances, leading to reduced intake and in some cases scours are known to adversely affect the health status and performance of nursery pigs. The origins of these disturbances are complex and to an extent are unknown. However, some research has indicated that indigestible components within the diet can lead to pathogen growth which in turn results in intestinal disturbances. Historically, the risk of these disturbances has been managed by providing in-feed sub-therapeutic antibiotics. Despite this, looking forward, the use of sub-therapeutic antibiotics may not be an option as many parts of the world have banned their use due to concerns that their over use may be contributing to antibiotic resistance. Finding viable alternatives is thus a major challenge for the global pork industry. One such alternative that has been shown to have the potential to mitigate intestinal disturbance and improve nursery performance are feed enzymes. Although feeding enzymes has been shown to improve digestion and feed efficiency, recent research is showing that enzyme supplementation can also generate prebiotics "a concept coined as pre-probiosis" within the gut which can have positive effects on the health and immune status of the pig.  

This article will examine the benefits of feeding enzymes to nursery pigs and will focus on how enzyme supplementation improves digestion and feed efficiency as well as reviewing recent research that shows the beneficial aspects with respect to prebiotic formation and potential modes of action within the piglet intestine.

Before we can understand why enzymes are included into pig diets we must appreciate what enzymes are. Enzymes are biologically active proteins that speed up chemical and/or biological reactions. What this means is that what would normally take an extended period of time (e.g. breaking down dietary fibre) can occur very rapidly in the presence of the correct enzymes. As an example, phytase, which is arguably the most popular and successful enzyme being formulated into pig diets worldwide, selectively breaks down (hydrolyzes) the bonds that hold phosphorus to phytate, thus, increasing the digestibility of this nutrient and reducing  dietary inclusion levels of inorganic phosphorus sources.

However, the focus of this article is not phytase but rather enzymes such as xylanase, beta-glucanase, cellulase and others (i.e. carbohydrases) which hydrolyze the indigestible fibre components within pig diets. We now know that pigs lack the necessary enzymes to break down these compounds on their own and as a result an inverse relationship exists between a feed ingredients fibre level and its feeding value, as measured by digestible energy and outlined in Table 1. Therefore, if the fiber or more specifically the non-starch polysaccharides (NSP) present in various feed ingredients can be successfully broken down by the correct carbohydrases then the feeding value of that ingredient can be increased and feeding cost reduced.  

From an academic standpoint this sounds reasonably simple. But can a real economic benefit be achieved by supplementing carbohydrase enzymes into nursery pig diets? As an example, if the price of enzyme inclusion is $5 per tonne of feed into a typical nursery ration formulated to 3400 kcal/kg DE and costing $550/tonne then 1% improvement in energy is required to cover the cost of inclusion. When compared to published reports this is a fairly conservative and realistic expectation. In reality, the correct blend of supplemental enzymes will yield digestible energy improvements in excess of 1%, which in the context of our above example can result in economic savings of $5 - 10 per tonne of complete feed.

Recent research is showing that the benefits of enzyme supplementation extend beyond the ability to improve nutrient digestion and reduce feeding costs. Enzyme supplementation also improves the overall health of pigs by improving their intestinal health through the formation of prebiotics. These prebiotics promote the growth of beneficial bacteria within the gut and improve the overall intestinal environment, which in turn can result in reduced incidences of disease and dependence on medications.

To better understand the prebiotic effects of feed enzymes one needs to understand some basics about the carbohydrates or sugars present in pig rations. In simple terms, carbohydrates in pig diets can be broadly divided into two groups, the first being simple sugars and starch, which are readily digested by the pig´sown digestive enzymes. The second group are NSPs, which as mentioned above are large compounds composed of many sugar units and for the most part are indigestible to the pig. When NSPs are broken down into their component sugars by the correct blend of carbohydrase enzymes they acquire the potential to become prebiotics and can in turn exert health benefits by improving the pig´s intestinal environment. 

Once again, from an academic standpoint this seems straight forward, but can prebiotics really be created by supplementing pig diets with enzymes? A published study showed that when feed ingredients common to Western Canada are incubated with a broad spectrum (pectinase, cellulase and mannanase) of carbohydrase enzymes, a wide range of sugars are in fact released (Table 2).

But will these sugars, once released by enzyme supplementation, act as prebiotics and improve the intestinal environment? Researchers assessed this question by using an advanced "in situ" experimental model. In essence, the researchers directly infused enzyme hydrolysis products into living piglet intestinal segments that were experimentally infected with E. coli K88 and then measured fluid passage and absorption (to estimate diarrhea) through the segments. The researchers found that after an E. coli K88 infection, segments that were infused with enzyme hydrolysis products had greater fluid absorption than control segments (Figure 1). This means that the sugars released from enzyme hydrolysis exert a beneficial effect on intestinal tissues during an infection which could lead to reduced scours and improved recovery in a commercial operation.

 

Figure 1. Effect of hydrolysis products on fluid absorption in piglet intestinal segments (Anim. Sci. J. 81:63; J. Nutr. 138:502)

Thus, we can see that under controlled experimental conditions, enzyme hydrolysis products have the potential to reduce the negative effects of an E. coli K88 infection by reducing intestinal fluid loss. However, can the same benefits be achieved in live pigs challenged with E. coli K88? The same authors conducted such trials and found that piglets challenged with E. coli K88 and provided with hydrolysis products from wheat middlings, flax, soybean and canola meal had lower stomach pH and greater levels of intestinal acid compared to control piglets. (Table 3). In addition, piglets fed enzyme hydrolysis products consumed more feed, grew more (Table 3) and had lower incidences of diarrhea than control piglets (Figure 2).

 

 

 

 

 

 

Figure 2. Development of diarrhea (measured as fecal scores) of piglets fed hydrolysis products and challenged with E. coli K88. Higher fecal scores indicate more severe diarrhea (Can J. Anim. Sci. 89:341)

It has been estimated that worldwide, upwards of 50% of the economic losses seen in weaned pig production can be associated with E. coli infection and that in positive herds 2% mortality can be seen. Reducing this mortality by even a small amount while simultaneously improving feed conversion easily covers the cost of enzyme inclusion given that a 1% reduction in nursery mortality and an FCR improvement of 0.1 can generate savings of approximately $5 - 10 per sow per year in a farrow to finish operation, respectively.

It is evident from the research presented in this article that the benefits to be gained from enzyme supplementation are not only from improved nutrient digestion and feed efficiency. Improved gut health as a result of prebiotics formed from the hydrolysis of common feed stuffs can also benefit the nursery pig by controlling enteric infections such as E. coli. Although this research is still in its infancy, the implications in terms of economic savings and as a potential alternative technology to replace antibiotic growth promoting compounds in pig feeding programs are significant.