Intestinal development is crucial for the future health and performance of all young animals. It is especially relevant for piglets during the weaning period. Low feed intake immediately after weaning is responsible for villous atrophy, lower nutrient absorption and reduced available energy. Unfortunately, this phenomenon occurs during a period when growth is crucial, especially since post-weaning body weight is highly correlated to final body weight.
By Clément Soulet, Pancosma, Switzerland (clément.firstname.lastname@example.org)
Among the major nutrients absorbed by the gut, glucose is extremely important as it is a source of energy used by the body for growth. For instance, glucose enables the gut mucosa to develop and therefore to increase nutrient uptake, which in return increases the overall growth of the animal.
Research on the gut
For a long time, the gut has been described as a simple organ with digestive functions such as motricity, enzyme secretion, digestion, absorption, and immunity. Research and technology have provided us with a better understanding of its functions, and today it is widely accepted that the gut has its own nervous system made up of 500 million nerve cells. Furthermore, Furness and others (1999) proposed that the intestine is in fact a sensory organ. The gut is able to perceive its internal environment and adapt to it autonomously without any interaction with the central nervous system. The scientific community has spoken of the ‘second brain’ and ‘gut-to-gut communication’. The gut has its own brain and autonomy. In this context, the R&D department, led by Dr Bravo, of Swiss feed additives company Pancosma, in co-operation with major universities, has conducted research in animal nutrition about gut-to-gut communication. Among them, the company’s researchers demonstrated that their high intensity sweetener Sucram had an impact on swine guts, with proven functional effects known as ‘gut effects’. The researchers demonstrated that the sweetener increases glucose, water and sodium absorption and acts on the epithelial structure by stimulating intestinal development. Six main elements are involved in these gut effect mechanisms:
These cells constitute the vast majority (98%) of those lining the villus. They are involved in nutrient absorption.
Short for sodium/glucose co-transporter 1. This is a specific protein located on the cell membrane of enterocytes. It absorbs dietary glucose in the intestine.
3. Enteroendocrine cells
These cells represent 1% of the cells lining the intestinal epithelium. They respond to changes in gut contents by releasing peptides. At least 20 different endocrine cell subpopulations have been defined. We are interested in the enteroendocrine cell, which releases the glucagon-like peptide-2 (GLP-2) hormone.
Also known as glucagon-like peptide-2. This gut hormone produced by the enteroendocrine cell plays an essential role in vital processes including the control of intestinal growth, enhancement of intestinal nutrient absorption, gut motility and blood flow.
5. Sweet taste receptors
The tongue recognises sweet tastes using a particular receptor that is expressed in lingual epithelium cells. This receptor is made of two subunits and is called T1R2+T1R3. Pancosma organised studies in cooperation with professor Dr Soraya Shirazi-Beechey at the University of Liverpool. These were the first to show that T1R2 and T1R3 are also expressed in the enteroendocrine cells of weaning piglet guts.
6. Enteric neurons
The enteric nervous system is a subdivision of the peripheral nervous system that directly controls the gastrointestinal system. It is made up of some hundred million neurons. It can operate independently of the central nervous system.
These six elements interact as follows, see also Figure 1. Enteroendocrine cells express sweet taste receptors made of two T1R1/T1R3 subunits. The constituents of the sweetener are recognised with very high affinity by the sweet taste receptors of the enteroendocrine cells (Step 1). This triggers in the enteroendocrine cell an intracellular signalling pathway that releases the gut hormone GLP-2 in the lamina propria (Step 2). These peptides then diffuse across the lamina propria to activate nearby enteric neurons, which propagate and amplify a message sent to enterocytes via neurotransmitters (Step 3). Neurotransmitters link to enterocyte receptors in the basolateral membrane (Step 4). This evokes an intracellular signalling pathway and leads to a doubling of SGLT1 in the apical membrane of the enterocytes (Step 5). Activated enterocytes increase the absorption of glucose as well as water and sodium (Step 6). Figure 1shows how the sweetener increases the number of glucose transporters on gut epithelial cells. A higher number of transporters lead to better glucose absorption and availability.
Results for weaned piglets
Until now, high intensity sweeteners have usually been used to provide a pleasant, sweet and long-lasting taste. They help ensure a good palatability of feed and achieve optimum feed intake. A great deal of published studies and trials refer to sweeteners and demonstrated their positive effect on feed intake. Sucram, the sweetener discussed in this article, has now been shown to go beyond providing sweetness and feed palatability. The sweetener increases glucose absorption and acts on the epithelial structure by stimulating intestinal development. The Swiss feed additive producer has given the name ‘gut effects’ to this demonstration of how the gut is able to perceive its environment and adapt to it. Gut effects induce responses at different levels: cellular, systemic, physiologic, zootechnic, and economic.
For the last several years, the company organised several scientific meetings related to the theme of gut effects. The events include three complementary symposia held in 2009 (Montreal, Canada), 2010 (Denver, CO, USA), and 2011 (New Orleans, LA, USA) during the Joint Annual Meeting of the American Society of Animal Science and the American Dairy Science Association.
Three major peer-reviewed papers support this research. Two were published in the British Journal of Nutrition in 2010. The third one was published in the Journal of Animal Science in 2011.
In weaning piglets, Moran and others (2010; British Journal of Nutrition) reported that the sensing of luminal intense sweeteners by T1R2 and T1R3 enteroendocrine cell receptors leads to the up-regulation of intestinal glucose transporter (SGLT1) mRNA expression as well as the increased translation of protein and glucose absorption capacity in piglets.
As shown in Figure 2, the sweetener induces a twofold increase of the gene associated with glucose transporters in the intestine. Glucose transporters and glucose uptake are increased twofold.
Higher glucose absorption leads to an improved nutrition of the villi and the gut mucosa. The sweetener increases villi height and crypt depth. That means that the sweetener increases the intestinal absorption surface and cell renewal (see Table 1).
Water and sodium are absorbed along with glucose. Thanks to the higher level of water absorption, using the sweetener tends to reduce diarrhoea and prevent enteric disorders.
In a trial conducted on weaning piglets, Sterk and others (2008; Journal of Animal Science) reported that the addition of the sweetener to the diet prevented post-weaning enteric disorders, and they observed an improvement in faecal consistency, see Figure 3.
For more than 20 years, trials and on-farm results have proven the sweetener’s performance. The company has carried out several trials demonstrating the positive effect of the sweetener on feed intake, body weight gain and feed efficiency for piglets. In a trial performed on 384 weaned piglets, the results summarised below show that the sweetener increases feed intake (+6%), body weight gain (+4.7%) and improves feed conversion ratio (-2.6%), see Figure 4.