Piglet gut health – insights and measurement
What is gut health?
In recent years, there has been an increase of the number of studies that define what “intestinal health” or “gut health” is. This is a consequence of the need to improve the productive performance of farm animals (growth, milk, meat and egg production), minimizing the cost of production and providing the highest possible level of animal welfare so that is accepted by the society.
The definition will depend on who we ask and what circumstance or factor we are referring to
We could think that the best gut health is found in nature, in wild animals. It this case, it will depend on the moment we choose to determine it. This is because we can evaluate it at a time of abundance of food, such as autumn in the Extremadura pasture for Iberian pigs or the frozen winter with snow and few resources in the Arctic tundra for the few wild boars that live there.
If we asked veterinarians, they would probably refer to the “absence of digestive pathologies that hinder the development of the animal”, in this case, the piglet.
If we ask nutritionists, they will answer us that intestinal health will be that state of the animal in which digestive functions are working normally. But we have to define what is “normality”.
Scientists will respond that it is still on doubt due to more research and trials are needed.
But, as experts in animal production, we could use the definition of Pietro Celi : “Gut health is a steady state where the microbiome and the intestinal tract exist in symbiotic balance, and where the welfare and performance of the animal are not limited by intestinal dysfunction. . ”
Criteria for measuring Gut Health in piglets
Bischoff proposes 5 criteria to measure intestinal health:
1 Effective digestion and absorption of nutrients, water and minerals.
→ Regular bowel movements, normal transit time, and no abdominal pain.
→ Normal consistency of stool (feces) and absence of nausea, vomiting, diarrhea, constipation and abdominal distention.
2 Absence of diseases in the (GI) gastrointestinal tract, without stomach diseases. Some examples could be ulcerations, carbohydrate intolerances, or enzyme deficiencies.
3 Normal and stable microbial flora, without abnormal growth of some bacterial species on others and without diarrhea associated with infections or parasites.
4 An effective immune state, with an effective function of the (GI) gastrointestinal barrier.
→ An effective and normal production of mucus and without bacterial translocations.
→ Normal levels of IgA, immunological tolerance and normal activity of the immune cells with absence of hypersensitivity of the mucosa.
5 A state of well-being. Although difficult to identify in production animals, it can be measured with normal serotonin levels and in the absence of stress markers.
The intestine also has an impact on the health of the individual:
Figure 1: The impact of the intestine on health: The gastrointestinal tract contributes to health by ensuring digestion and absorption of nutrients, minerals and fluids through various mechanisms. Among them, the induction of mucous membranes and systemic tolerance, the presence of defense systems against infections and other pathogens, and signaling from the periphery to the brain.
The function of the intestine is not limited to food processing and subsequent absorption of nutrients and fluids
Animal experiments and some human data have shown that the intestine communicates with bacteria that support digestion through their enzymatic capacity;
regulates epithelial and immune functions, which has a huge importance for intestinal health and general health;
the intestine also informs the brain (through the vagus nerve and certain hormones) about energy absorption and other conditions that could affect mood and general well-being of the animals; and
the intestine induces a tolerance in the immune system and establises defense against external aggressions from organisms carried with food.
Celi  states that there are 6 components that must be taken into account and studied to define intestinal health. They are all similar to what Bischoff takes into account with the sole exception that Celi incorporates diet that can be more easily manipulated and directed than in human gut health.
1 Diet where you have to consider the macro and micronutrients, the production-enhancing additives, the anti-nutritional factors of the different ingredients and the indigestible fractions.
2 An effective immune system.
3 Effective digestion and absorption.
4 A stable and effective microflora without overgrowth.
5 An intact intestinal mucosa with its mucous layer, epithelium, and associated lymphoid tissue.
6 Neuroendocrine and motor function of the intestine.
How can we measure intestinal health?
Varley, 2017 (comment in Pig Progress), defines that an animal that has good intestinal health must have a high correlation between general health and intestinal health, and therefore if:
Their weight gain from 30 kg to the slaughterhouse is optimal;
the number of days with antibiotic treatment is low or zero;
the slaughterhouse lung injury score is zero; and
the acute phase protein level that measures stress or inflammation at different times in your productive life is at a normal level …
that animal has or has had good intestinal health.
However, this way of evaluating must be associated with other series of values that measure the different components of intestinal health.
Measure gut health with in vivo techniques
Measuring intestinal health with in vivo techniques requires sophisticated methods, specific facilities, and specialized surgical technicians. It is also important to remarkt that it is not functionally viable. To measure intestinal health, it is proposed the use of biomarkers.
Biomarkers or biological markers are substances that can be used as a biological indicator. They must be able to be measured objectively and be indicators of a normal biological process, of a pathological state or as a response to a pharmacological treatment.
The development of biomarkers of the gastrointestinal functionality is crucial to advance to the understanding of events that affect the intestinal barrier, its functionality, and the ecology of the gastrointestinal microbiota. It might well be true that we currently have a deep knowledge of the digestive system and the absorption mechanisms of the main macro and micronutrients, but there is a large gap in research in relation to biomarkers of gastrointestinal permeability of gastrointestinal barrier function, of biomarkers for the intestinal endocrine system and of biomarkers that are indicative of the functional presence of beneficial microbiota or its metabolites.
Part II: Does the piglet gut health depend on the type and level of dietary fiber?
Article published in porciNews
Author: Morillo Alujas, Alberto
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 Bischoff, S.C. 2011. «“Gut health”: A new objective in medicine?» BMC Medicine 9-24.
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 Celi, Pietro, et al. 2018. «Biomarkers of gastrointestinal functionality in animal nutrition and health». Animal Feed Science and Technology, julio.
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