In the past decade, medium-sized producers in the United States accounted for most of the domestic antibiotic-free (ABF) pork production. Today, larger producers in the US and elsewhere are making the switch to ABF production due to growing consumer demand and the appeal of premium prices. Yet, several challenges can easily compromise profitability, such as higher mortality (especially in the post weaning phase), variability of market weight, increased days to market, and higher costs of treatment when intervention is required.
In many markets, there are no official guidelines for the rearing of ABF pigs. Each producer has to develop their own program to achieve ABF production, from birth to harvest or during the period of growth being referred to in the claim. Therefore, producers can make their own decisions on adopting and discarding practices and tools to achieve profitability.
The main challenge of ABF pork production is to prevent respiratory and gastrointestinal diseases. In this article, we will discuss strategies to prevent gastrointestinal problems by going through an overview of each component of gut health.
What is gut health?
The gut is commonly understood as the gastrointestinal tract (GIT), the place where digestion and absorption of nutrients occurs. A healthy gut maximizes the extraction and utilization of nutrients for animal growth. The definition of gut health is not well established due to the complexity and overlapping functionality. However, most researchers talk about four main areas: microbiota, intestinal integrity, mucosal immune system, and intestinal morphology (Figure 1).
Figure 1. The four overlapping components of gut health
Early establishment of microbiota
The microbiota consists of commensal and pathogenic microorganisms that reside in the lumen of the GIT (Figure 2). The diversity and abundance of the microbiota has a direct effect on the health and well-being of the animals. The establishment of microbiota starts immediately after birth. A newborn piglet is naturally inoculated with microbiota from its environment. The microbiota of the sow and the sanitation of the crate play a crucial role in the establishment of microbiota in the piglet. Sanitation and biosecurity play a pivotal role in preventing disease outbreaks.
Incorporating probiotics and prebiotics into the diet of lactating sows can facilitate the early colonization of the piglet’s GIT with beneficial bacteria. In addition, to sustain this balance between commensal and pathogenic bacteria, supplementation of probiotics, prebiotics, organic acids, and phytogenics is also beneficial. An excess of indigestible protein can negatively affect the microbiota because, when it reaches the hindgut, it alters the pH and creates an environment more suitable for the growth of pathogenic bacteria. Hence, it is recommended to use a highly digestible protein source, reduce the level of crude protein in the diet, or incorporate feed additives that can enhance protein digestibility such as phytogenics or proteolytic enzymes (Table 1). The most common enteric problems caused by pathogenic organisms in swine are shown in Table 2.
E. coli is one of the most common causes of neonatal and post-weaning diarrhea. It binds to the enterocytes through fimbrial adhesions (such as F18, K88 and K99) and later the E. coli proliferates and produces enterotoxins (such as STa, STb and LT). The enterotoxins cause excessive secretion of fluids into the lumen, resulting in diarrhea. Some of the probiotic bacterial strains can attach to the intestinal wall, impeding the adherence of pathogenic bacteria to the wall, preventing them from colonizing the gut. This mechanism is referred to as competitive exclusion.
Preserving intestinal integrity
Intestinal integrity is the capability of the epithelial layer to serve as a physical barrier, preventing the translocation of toxins and pathogens while allowing the passage of nutrients (Figure 2). The epithelial layer consists of enterocytes joined together by a complex network of proteins known as tight junctions. The enterocytes have the capability to transport molecules (e.g. ions, amino acids, sugars, and water) in a selective manner. However, the enterocytes can be physically damaged during starvation, water deprivation, heat stress, or by consuming toxins and rancid fats. Damage to the enterocytes impairs the efficient transport of nutrients. In addition, the tight junctions can also be damaged by mycotoxins, bacterial toxins, cytokines, and stress hormones (Figure 2).
Figure 2. Brief description of the components of the intestinal epithelium layer and its surroundings
Disruption of the tight junctions allows many pathogens and toxins to pass through the epithelial layer, possibly causing a systemic inflammatory response. Preventing any sources of environmental stress, reducing the risk of mycotoxins and bacterial infection, and avoiding the inclusion of rancid fats in the diet can help to preserve intestinal integrity (Table 1).
Encouraging cell repair is also beneficial. This can be achieved by providing sufficient antioxidants (vitamins E, C, D and A) in the diet and supporting the activity of the antioxidant systems (glutathione peroxidase, thioredoxin reductase, superoxide dismutase, and catalase). The antioxidant systems are mineral-dependent, thus it is recommended to provide sufficient amounts of the minerals involved in these enzymatic reactions (Se, Zn, Cu, Mn and Fe) to ensure their proper functioning.
A common problem in swine production is the contamination of the diets with deoxynivalenol (vomitoxin).
Deoxynivalenol is the most harmful mycotoxin known for swine as it damages the enterocyte and allows the invasion of pathogenic bacteria.
For instance, Salmonella invasion increased ten times when diets were contaminated with 750 ppb of deoxynivalenol (Vandenbroucke et al., 2011). Therefore, having a mycotoxin risk management program in place is essential to support intestinal integrity.
Properly developed mucosal immune system
The mucosal immune system is composed of the immune cells (e.g. lymphocytes, macrophages, dendritic cells) that surround the intestinal epithelium, and the sites for recruitment of those immune cells (e.g. Peyer’s patch, mesenteric lymph node; Figure 2). In mammals, the mucosal immune system is well-organized and sophisticated, working in two ways. The first is a quick but non-specific response (innate) and the second is a long-term, more specific response (adaptive).
Increasing the weaning age allows the mucosal immune system to develop properly. The immune system should be sufficiently able to fight a pathogen without over-stimulation, which causes unnecessary inflammation and is energetically costly. Therefore, adding phytogenic compounds with anti-inflammatory properties, and using omega-3 fats in the diets is recommended to reduce inflammation.
Table 1. Strategies to improve gut health in an ABF pork production system
Table 2. Most common gastrointestinal pathogens observed in swine
The use of vaccines helps the immune system to respond faster and more specifically to a pathogen. The vaccines induce the immune system to produce B and T lymphocytes (white blood cells) that are specific for a pathogen. B lymphocytes produce antibodies that can be released into the surroundings, whereas T lymphocytes possess receptors that identify the pathogen and once activated, they proliferate very quickly to attack the pathogen (Figure 2).
Today, there are vaccines for most of the common gastrointestinal pathogens found in swine (Table 2). The vaccines for pathogens that are a risk for the nursing pig (E. coli and C. perfringens) are given to the sow during gestation. In the post-weaning period, common vaccines applied to the pigs are Porcine circovirus 2, E. coli (K88, K99, 987P, F41), and Ileitis. It is important to consider that the efficacy of vaccines can decrease due to immune suppression caused by stressors. Mycotoxins decrease the activity of B and T lymphocytes. For instance, fumonisin has been found to reduce antibody production of Mycoplasma agalactiae (Taranu et al., 2005). Therefore, a vaccine program must be supported by a mycotoxin risk management program.
Healthy gut, more nutrient absorption
An intuitive way to determine gut health is by looking at the intestinal morphology, which is determined by the length of villi and the depth of crypt (Figure 3). In the absence of stressors, the cells lining the intestine can preserve their structure and functionality. The longer length of the villi is interpreted as a larger surface area for nutrient absorption. Intestinal morphology reveals that the first three components are in harmony and that the pig possesses a healthier gut for nutrient absorption and utilization.
Phytogenic compounds have numerous beneficial properties that support gut health, such as antimicrobial, anti-inflammatory and antioxidant effects. A deliberate combination of phytogenic compounds can provide a comprehensive approach to supporting gut health. The phytogenic blend offered by BIOMIN, Digestarom® DC Xcel has shown to increase villus height by 15% (Figure 3). The improvements in intestinal morphology had a direct effect on nitrogen retention (nitrogen intake – nitrogen excretions). These results validate that more nutrients were utilized for pig growth, as the pigs supplemented with Digestarom® DC Xcel weighed 1.18kg more in terms of body weight at d 35 postweaning (Figure 4).
Figure 4. Body weight of pigs at day 35 post-weaning
The profitability of ABF pork production can be easily affected during a health challenge. Implementation of a comprehensive gut health program is essential in ABF pork production to prevent enteric challenges. Table 1 summarizes useful strategies that directly impact each of the components of gut health. Producers must evaluate and determine suitability of the recommended strategies and their combination in their own production system. BIOMIN offers a combination of innovative products and on-site support to help customers reach their long-term goals.