Betaine, a trimethyl derivative found in living organisms in deserts and low rainfall areas, increases breast meat yield in broilers. Its osmolytic properties help maintain the gut mucus membrane during heat stress and digestive disorders. As a methyl donor, it is involved in the synthesis of methionine.
Additional water retention, due to the osmolytic property of betaine, increases the volume of the cell, thereby increasing the anabolic activity and integrity of the cell membrane. This permits cellular adaptation in adverse osmotic environments and increases the overall performance of the bird.
In practical poultry nutrition, betaine can improve performance and carcass composition, reduce litter moisture and help overcome coccidiosis and stress.
The influence of betaine supplementation primarily depends on the concentrations of other labile methyl groups in the diet and the magnitude of stress to the bird. Betaine supplementation was ineffective in influencing the bird's performance in diets with either adequate or severe deficiency of methionine. However, improvement in bodyweight, breast meat yield, feed conversion and decreased abdominal fat pad weights with betaine supplementation have been reported. Study results indicate significant improvement in feed efficiency in broilers fed betaine (800mg/kg) either sub-optimal concentrations of methionine compared to those fed no betaine, irrespective of the concentration of the amino acid.
Reducing litter moisture
During intestinal stress conditions (including diarrhoea), absorption of sodium (Na+) and chloride (Cl-) ions decreased through the intestinal villus membrane, resulting in hyperosmolar solution in the intestinal lumen. Betaine supplementation increases intestinal mucosal cell integrity and allows the cells to function normally. This helps optimise nutrient digestibility and reduces excretion. Litter moisture content reduced at 6 days from 46 to 27% after feeding betaine in water (2.5g/l). The dose of betaine to control diarrhoea in poults was 0.15-1.5g/kg bodyweight.
Better carcass characteristics
Betaine has methionine-sparing activity and is involved in synthesis of carnitine. Thus, it has a role in protein and fat metabolism and can alter carcass composition. It reduces protein turnover, which results in higher nitrogen retention, which has a positive effect on accretion of protein in muscle (carcass leanness). Betaine enhances lipid catabolism via its role in carnitine synthesis and leads to low carcass fat deposition.
The effect of betaine on abdominal fat deposition and carcass yields is inconsistent, depending on many other dietary factors.
Breast meat yield significantly improved with betaine supplementation (800mg/kg) to diets containing different concentrations of methionine. At higher concentrations of methionine (2.4% of crude protein), betaine had no effect on yield.
Effects of betaine as an osmolyte are clear when exposed to gut osmotic disorders. Coccidiosis decreases villus height and jejunal crypt:villus ratio, and increases the osmolarity in duodenum. The beneficial effects on birds infected with coccidiosis may be due to its osmolytic activity and increased phagocytic activity in the gut mucous membrane. Betaine (0.1%) decreased the osmolarity of duodenum and increased the number of leukocytes in the epithelium and lamina propria of chicks with coccidia infection. Betaine increased phagocytosis of coccidia by macrophages and nitric oxide release from heterophils and macrophages.
The efficacy of certain anticoccidial compounds can be modulated by betaine supplementation. Growth of Eimeria acervulina was reduced in chicks fed diets containing betaine (0.075%) plus salinomycin (66mg/kg) compared to those fed salinomycin only. Other anticoccidials interfere with conversion of choline to betaine.
Stress releases more reactive oxygen species (ROS) in the system. These impair the cell structure, membrane integrity and ion pump in the gut lumen. Cell dehydration leads to disturbances in cell metabolism and its enzyme activities. Feed intake leads to movement of intracellular water to the gut lumen causing shrinkage of the gut mucosal epithelium. Disturbance in cell structure impairs nutrient absorption, cell membrane transport and certain intracellular metabolic processes.
Betaine increases cytoplasmic osmotic pressure in stressed cells and tolerance to temperature and ionic disturbance. Accumulation of conventional osmolytes like potassium ions (K+) in the cell may lead to disturbance in activity of cell enzymes. Accumulation of betaine protects the cells from osmotic stress and allows continued normal metabolic activities under stress that would otherwise inactivate the cell. Betaine supplementation during heat stress reduces the heterophil:lymphocyte ratio, an indicator of stress in poultry.
The amount of betaine supplementation required largely depends on the concentration of other labile methyl groups (methionine, choline, folic acid), environmental temperature, intestinal integrity, coccidial challenge and the anticoccidial used. The response of betaine was greater than methionine when added to diets containing low levels of methionine (75% of NRC requirement, 1994). Typically, betaine can be added at 0.05-0.08% in broiler diet. Benefits on coccidiosis lesion scores have been noted at 0.05% but osmolyte activity increases as betaine increases. During diarrhoea, when the osmotic balance is disturbed, the effective dose to control diarrhoea ranged from 0.15-1.5g/kg bodyweight.
Generally, the recommended concentration of betaine in the feed is 500-750g/tonne. Utilisation of betaine may be reduced at higher concentration (>800g/tonne).