Betaine is a naturally occurring compound widely distributed in plants and animals.As a feed additive, it is provided in anhydrous or hydrochloride form. It can be added to animal feed for various purposes.
First of all, these purposes may be related to the very effective methyl donor ability of betaine, which mainly occurs in the liver.Due to the transfer of unstable methyl groups, the synthesis of various compounds such as methionine, carnitine and creatine is promoted.In this way, betaine affects protein, lipid and energy metabolism, thereby beneficially changing the carcass composition.
Secondly, the purpose of adding betaine in feed may be related to its function as a protective organic penetrant.In this function, betaine helps cells throughout the body maintain water balance and cell activity, especially during periods of stress.A well-known example is the positive effect of betaine on animals under heat stress.
In pigs, different beneficial effects of betaine supplementation have been described.This article will focus on the role of betaine as a feed additive in the intestinal health of weaned piglets.
Several betaine studies have reported the effect on the digestibility of nutrients in the ileum or total digestive tract of pigs.Repeated observations of increased ileal digestibility of fiber (crude fiber or neutral and acid detergent fiber) indicate that betaine stimulates the fermentation of bacteria already present in the small intestine, because intestinal cells do not produce fiber-degrading enzymes.The fiber part of the plant contains nutrients, which can be released during the degradation of this microbial fiber.
Therefore, improved dry matter and crude ash digestibility was also observed.At the total digestive tract level, it has been reported that piglets supplemented with 800 mg betaine/kg diet have improved crude protein (+6.4%) and dry matter (+4.2%) digestibility.In addition, a different study showed that by supplementing with 1,250 mg/kg betaine, the apparent total digestibility of crude protein (+3.7%) and ether extract (+6.7%) was improved.
One possible reason for the observed increase in nutrient digestibility is the effect of betaine on enzyme production.In a recent in vivo study on the addition of betaine to weaned piglets, the activity of digestive enzymes (amylase, maltase, lipase, trypsin and chymotrypsin) in chyme was evaluated (Figure 1).All enzymes except maltase showed increased activity, and the effect of betaine was more pronounced at 2,500 mg betaine/kg feed than at 1,250 mg/kg.The increase in activity may be the result of an increase in enzyme production, or it may be the result of an increase in the catalytic efficiency of the enzyme.
Figure 1-Intestinal digestive enzyme activity of piglets supplemented with 0 mg/kg, 1,250 mg/kg or 2,500 mg/kg betaine.
In in vitro experiments, it was proved that by adding NaCl to produce high osmotic pressure, trypsin and amylase activities were inhibited.Adding different levels of betaine to this test restored the inhibitory effect of NaCl and increased enzyme activity.However, when NaCl is not added to the buffer solution, betaine does not affect the enzyme activity at a lower concentration, but does show an inhibitory effect at a higher concentration.
Not only the increased digestibility can explain the reported increase in growth performance and feed conversion rate of pigs supplemented with dietary betaine.Adding betaine to pig diets also reduces the animal’s maintenance energy requirements.The hypothesis for this observed effect is that when betaine can be used to maintain intracellular osmotic pressure, the demand for ion pumps is reduced, which is a process that requires energy.In the case of limited energy intake, the effect of supplementing betaine is expected to be more pronounced by increasing the energy supply for growth rather than maintenance.
The epithelial cells lining the intestinal wall need to cope with highly variable osmotic conditions generated by the luminal contents during nutrient digestion.At the same time, these intestinal cells need to control the exchange of water and different nutrients between the intestinal lumen and plasma.In order to protect cells from these challenging conditions, betaine is an important organic penetrant.When observing the concentration of betaine in different tissues, the content of betaine in the intestinal tissues is quite high.In addition, it has been observed that these levels are affected by dietary betaine concentration.Well-balanced cells will have better proliferation and better recovery capabilities.Therefore, the researchers found that increasing the betaine level of piglets increases the height of duodenal villi and the depth of ileal crypts, and the villi are more uniform.
In another study, an increase in the height of villi in the duodenum, jejunum, and ileum could be observed, but there was no effect on the depth of the crypts.As observed in broiler chickens infected with coccidia, the protective effect of betaine on intestinal structure may be even more important under certain (osmotic) challenges.
The intestinal barrier is mainly composed of epithelial cells, which are connected to each other by tight junction proteins.The integrity of this barrier is essential to prevent the entry of harmful substances and pathogenic bacteria, which would otherwise cause inflammation.For pigs, the negative impact of the intestinal barrier is considered to be the result of mycotoxin contamination in the feed, or one of the negative effects of heat stress.
In order to measure the impact on the barrier effect, in vitro tests of cell lines are often used to measure transepithelial electrical resistance (TEER).With the application of betaine, improved TEER can be observed in multiple in vitro experiments.When the battery is exposed to high temperature (42°C), TEER will decrease (Figure 2).The addition of betaine to the growth medium of these heat-exposed cells counteracted the decreased TEER, indicating increased heat resistance.
Figure 2-In vitro effects of high temperature and betaine on cell transepithelial resistance (TEER).
In addition, in an in vivo study in piglets, the increased expression of tight junction proteins (occludin, claudin1, and zonula occludens-1) in the jejunum tissue of animals that received 1,250 mg/kg betaine was measured compared with the control group.In addition, as a marker of intestinal mucosal damage, the diamine oxidase activity in the plasma of these pigs was significantly reduced, indicating a stronger intestinal barrier.When betaine was added to the diet of growing-finishing pigs, the increase in intestinal tensile strength was measured at the time of slaughter.
Recently, several studies have linked betaine to the antioxidant system and described reduced free radicals, reduced levels of malondialdehyde (MDA), and improved glutathione peroxidase (GSH-Px) activity.
Betaine not only acts as an osmoprotectant in animals.In addition, many bacteria can accumulate betaine through de novo synthesis or transportation from the environment.There are signs that betaine can have a positive effect on the number of bacteria in the gastrointestinal tract of weaned piglets.The total number of ileal bacteria, especially bifidobacteria and lactobacilli, has increased.In addition, lower amounts of Enterobacter were found in feces.
Finally, it is observed that the effect of betaine on the intestinal health of weaned piglets is the reduction of diarrhea rate.This effect may be dose-dependent: the dietary supplement 2,500 mg/kg betaine is more effective than 1,250 mg/kg betaine in reducing the rate of diarrhea.However, the performance of weaned piglets at the two supplement levels was similar.Other researchers have shown that when 800 mg/kg of betaine is added, the rate and incidence of diarrhea in weaned piglets is lower.
Betaine has a low pKa value of about 1.8, which leads to dissociation of betaine HCl after ingestion, leading to gastric acidification.
The interesting food is the potential acidification of betaine hydrochloride as a source of betaine.In human medicine, betaine HCl supplements are often used in combination with pepsin to support people with stomach problems and digestive problems.In this case, betaine hydrochloride can be used as a safe source of hydrochloric acid.Although there is no information on this property when betaine hydrochloride is contained in piglet feed, it may be very important.
It is well known that the pH of the gastric juice of weaned piglets may be relatively high (pH>4), which will affect the activation of pepsin precursor to its precursor pepsinogen.Optimal protein digestion is not only important for animals to obtain good availability of this nutrient.In addition, indigestion protein can cause harmful proliferation of opportunistic pathogens and increase the problem of post-weaning diarrhea.Betaine has a low pKa value of about 1.8, which leads to the dissociation of betaine HCl after ingestion, leading to gastric acidification.
This short-term reacidification has been observed in a preliminary study in humans and studies in dogs.After a single dose of 750 mg or 1,500 mg of betaine hydrochloride, the pH of the stomach of dogs previously treated with gastric acid reducing agents dropped severely from about 7 to pH 2.However, in untreated control dogs, the pH of the stomach was about 2, which was not related to betaine HCl supplementation.
Betaine has a positive effect on the intestinal health of weaned piglets.This literature review highlights different opportunities for betaine to support nutrient digestion and absorption, improve physical protective barriers, influence the microbiota, and enhance the defense capabilities of piglets.