was reported in piglets supplemented with 800 mg betaine/ kg in their diet. In addition, a different study showed im- proved apparent total tract digestibility of crude protein (+3.7%) and ether extract (+6.7%) by supplementing 1,250 mg/kg betaine.
Enzyme production A possible reason for observing improved digestibility of nu- trients is an influence of betaine on enzyme production. In a recent in vivo study regarding the effect of betaine supple- mentation in weaned piglets, the activities of digestive en- zymes (amylase, maltase, lipase, trypsin and chymotrypsin) in digesta were 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. Increased activity could result from higher enzyme pro- duction, but also from improved catalytic efficiency of the enzymes. In an in vitro trial, it was demonstrated that by adding NaCl to create hyperosmolarity, trypsin and amylase activity are in- hibited. The inclusion of different levels of betaine in this test restored the inhibitory effect of NaCl and increased enzyme activity. However, when no NaCl was added to the buffer solution, betaine inclusion did not influence enzyme activity at lower concentration but did show an inhibitory effect at relatively high concentration.
Reduced maintenance energy Increased digestibility does not solely explain the reported improved growth performance and feed conversion in pigs supplemented with dietary betaine. Incorporation of betaine in pig diets also leads to reduced maintenance energy requirement of the animal. A hypothesis for this observed effect is the reduced need for ion pumping, an
energy-requiring process, when betaine is available for maintaining the intracellular osmolarity. Under conditions where energy intake is limiting, effects of betaine supple- mentation are therefore expected to be more pronounced by increasing the availability of energy for growth instead of maintenance.
Intestinal structure The epithelial cells lining the intestinal wall need to cope with highly variable osmotic conditions generated by the luminal content during nutrient digestion. Meanwhile, these enterocytes need to control the exchange of water and different nutrients between the intestinal lumen and the plasma. To protect the cells against these challenging conditions, betaine is an important organic osmolyte. Exam- ining betaine concentrations in different tissues shows that intestinal tissue contains considerably high betaine levels. Moreover, it has been observed that these levels can be in- fluenced by dietary betaine concentration. Well-balanced cells will have better proliferation and good resilience. Ac- cordingly, researchers found that increasing betaine levels in piglets increased duodenal villus height and ileal crypt depth, and that the villi were more uniform. In another study, increased villus height were observed in the duodenum, jejunum and ileum without influence on the crypt depth. The protective effects of betaine on intesti- nal structure might be even more important under specific (osmotic) challenges, as observed in broilers infected with coccidia.
Gut barrier effect The intestinal barrier mainly consists of epithelial cells, at- tached to each other by tight junction proteins. The integrity of this barrier is fundamental to prevent the entry of harmful
▶ PIG PROGRESS | Volume 37, No. 5/6, 2021 9
Incorporation of betaine in pig diets also leads to a reduction in the main ten- ance energy requirement of the animal.
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