Post-weaning diarrhea in piglets: contributing factors related to husbandry practices and nutritional protection strategies

1. Diet composition

The quantity and quality of proteins and fiber included in the diet during the post-weaning phase have an important impact on the gastrointestinal functionality of piglets. Indigestible dietary protein that enters the large intestine is then available for microbial fermentation. The pH of the gut can rise due to the high buffering capacity of protein. These environmental changes within the GIT can favor the proliferation of pathogenic bacteria (ETEC), and the production of potentially toxic compounds such as ammonia and amines, which have been implicated in PWD (Pluske et al., 2022).

Soybean is the most common protein source used in pig diets, but it is often not produced locally to the pig unit, resulting in a high contribution to the carbon footprint of the production system. In the move towards more sustainable pork production, producers are choosing to incorporate more locally sourced protein sources such as rapeseed meal or sunflower seed meal in piglet diets. However, these protein sources might contain higher dietary fiber compared to soybean meal, which may act as an antinutritional factor. The presence of a high proportion of soluble fiber increases digesta viscosity and reduces the rate of nutrient absorption, promoting ETEC proliferation (Molist et al., 2009).

2. Sanitary conditions

In commercial swine production, pigs are exposed to various stressors, broadly classified as non-biological stressors (e.g., noxious gases, such as ammonia, hydrogen sulfide gases, carbon dioxide and dust particles) and biological stressors (e.g., bacteria, viruses). Low sanitary conditions (LSCs) are known to modify the intestinal microbiome composition and functionality of pigs, and it has been consistently reported that intestinal inflammation, oxidative stress, and disturbed intestinal integrity are consequences of poor sanitary housing in pigs (Le Floc’h et al., 2009). Moreover, LSCs alter nutrient and energy metabolism, leading to shifts in amino acid and maintenance energy requirements, and it is generally accepted that LSCs increase protein fermentation (Van der Meer et al., 2020). As a result of all the physiological changes caused by LSCs, the likelihood of PWD is much greater.

3. Temperature and ventilation

During the post-weaning period it is essential to provide the correct environmental temperature (26–28°C) to keep pigs in their thermo-neutral zone. A high ambient temperature reduces intestinal peristaltic activity due to a decrease of blood flow in the GIT and a reduction in the supply of oxygen. This leads to intestinal hypoxia, inflammation, oxidative stress and promotion of bacterial colonization.

Low temperatures in weaner facilities appear to be responsible for a more severe form of PWD (Rouma et al., 2017). On the other hand, ventilation serves to remove water vapor and noxious gases and to some extent controls the temperature of the animal house. Ventilation determines air velocity at pig level and therefore plays an important role in the rate of heat loss, especially in young pigs. Eriksen et al. (2022) described an association between high ventilation index score and low PWD occurrence.

4. Stocking density

In weaned piglets, crowding is a stressor which adversely alters the gut barrier nutrient transport function and increases intestinal pH. In addition, a high stocking density leads to lower resistance to bacterial infection as well as an increase in fecal shedding of pathogens with higher proliferation of ETEC (Khafipour et al., 2014). Moreover, crowding stress also results in abnormal behavior and greater aggression which alters oxidative status and gut bacterial population (Correa et al., 2023), both of which are predisposing factors for gastrointestinal dysfunctions such as diarrhea.

Nutritional strategies to maximize gastrointestinal functionality

Post-weaning diarrhea is considered one of the main disorders contributing to the use of antibiotics and therapeutic levels of zinc oxide (ZnO) in pig production. The use of antibiotics and medical levels of ZnO in pig production has a detrimental impact on both human health and the environment. Moreover, factors other than pathogens (such as husbandry practices as described above) can also lead to diarrhea which indicates that antibiotics are not always the most appropriate solution for treating diarrhea in piglets. Thus, adopting better husbandry practices and administering dedicated nutritional solutions via the piglet feed should be considered to support the healthy functioning of the gut so as to avoid gut disturbances such as piglet diarrhea.

1. Protein/amino acid management

Reducing the protein content as much as possible (without compromising least cost and performance), balancing essential amino acids, and using highly digestible protein sources immediately after weaning have been presented as efficient and sustainable strategies to mitigate PWD (Heo et al., 2013). In addition, the use of feed enzymes such as proteases to improve protein digestibility (Song et al., 2022), and the inclusion of organic acids, such as benzoic acid, to reduce pH in the gut (Diao et al., 2014), exert a favorable effect on reducing PWD in piglets.

2. Carbohydrate management

The selection of specific dietary fiber fractions may prevent (insoluble fiber) or stimulate (soluble fiber) the overgrowth of pathogenic bacteria. Thus, there is a need to identify dietary fiber fractions from raw materials to formulate diets (Canibe et al., 2022). Dietary inclusion of carbohydrases (xylanase, β-glucanase) which increase the in vivo availability of short-chain oligosaccharides has beneficial effects on gut health, and thus preventing PWD.

3. Boosting antioxidant and anti-inflammatory capacity

Most of the husbandry practices mentioned above lead to disrupted redox balance and inflammation. Optimal levels of supplemental vitamins might protect piglets during the post-weaning period by regulating intestinal immune functions (vitamins A and D), neutralizing the extra- and intracellular levels of reactive oxygen species (vitamins C and E) or modulating the composition and function of the gut microbiota (vitamins B group; Lauridsen et al., 2021).

Conclusion

To achieve more sustainable pork production without relying on medications during the post-weaning period, the adoption of better husbandry practices including sanitary, environmental and density conditions, together with dedicated nutritional solutions, should be considered. These strategies support optimum gastrointestinal development and functionality, thus avoiding gut disturbances such as piglet diarrhea.