Betaine and carcass modification
Both in fat and in protein metabolism, betaine has an influence. As a strong methyl donor, betaine improves synthesis of carnitine and phosphatidylcholine, involved in fatty acid oxidation and fat transport through the body. By converting homocysteine to methionine, betaine increases methionine concentration for the animals (protein) metabolism and also extra glycine comes available after betaine loses its third methyl group. Additionally to this participation in protein and lipid metabolism, betaine could promote growth of pigs by changes in growth hormone levels.
As a result, dietary betaine can decrease back fat and increase carcass leanness. This is called the lipotropic effect of betaine and is not only seen in pigs, but also in broilers and even in humans. Higher dressing percentage is often favoured by customers, but also brings economically an advantage. The alteration of body composition (less subcutaneous fat and lower carcass fat percentage) can depend on genetics and also on synergistic interactions with other nutrients like conjugated linoleic acid. Some authors indicate that the effect of betaine is greater when added to diets containing low concentrations of energy.
Both for sows and boars, beneficial effects of betaine on reproductive performances are described. The temperature in the farrowing stable is often above the comfort zone of sows, in favour of the newborn piglets. Betaine for lactating sows reduces the negative impact of heat, observed by a better feed intake of the lactating sow. This results in less need to mobilize body reserves, accordingly lower body weight loss and a reduced weaning to oestrus interval are described. In some studies an improvement of litter weight at weaning was also found. When supplemented to gestating sows, betaine resulted in an increased number of piglets born, especially in sows of third parity onwards. For boars, a tendency for increased total sperm in ejaculates was seen with intake of betaine during summer.
Heat stress protection
Accumulated in high concentrations in the cytoplasm of cells, betaine prevents osmotic pressure on cell membranes. Osmotic stress may be caused by disease, malnutrition or inadequate environmental conditions such as high temperature. Accumulation of betaine permits metabolic activity under conditions that would normally cause impairment of cell functions. This stabilising influence on tissue metabolism is particularly important within the digestive tract. A more resistant gut epithelia and a persistent production of cellular enzymes, ensure the digestibility of nutrients. Next to the protective working of betaine on animals cells and tissues during heat stress, betaine reduces heat production. Consequently, lower rectal temperatures were seen in betaine supplemented sows.