The regulation of cellular hydration state, and therefore cell volume, is important for maintenance of cell function and several metabolic pathways (i.e.: protein turnover, amino acid carbohydrate, etc). Cells try to adapt to external osmotic stress by accumulating inorganic ions (Na+ , K+ , Cl- ) and organic osmolytes (methylated amines and certain amino acids). However, the increase in intracellular concentrations of inorganic ions is limited due their destabilising effect on protein structure and enzyme function; on the other hand organic osmolytes can reach high intracellular concentrations without disturbing cellular functions. Betaine is considered the most effective organic osmolyte. It accumulates in GIT cells regulating water flux across the intestinal epithelium. Betaine also had shown to inhibit cellular apoptosis and to reduce energy expenditure for GIT cells. A 5% reduction in energy requirements for maintenance (ENm) of the GIT cells in pigs fed betaine was found.
Several scientific publications showed the proof of principle that betaine anhydrate can be used to overcome heat stress. Attia et al., (2009) showed that the impact of severe heat stress could partially be overcome by adding betaine to the diet in slow growing broilers. Adding 1 kg/t betaine to the diet improved weight gain and feed conversion compared to negative control treatment. More importantly, rectal temperature decreased (43.2°C versus 41.9°C) compared to negative control. Panting, a mechanism of heavily breathing to lose heat via evaporation, was also reduced (78.3 versus 63.9 breaths/minute). Hassan et al., (2011) showed a clear dose-response effect when betaine was added in 250, 500, 750 or 1000 g/t feed to the diet in rabbits kept under severe heat stress conditions. Haldar et al., (Bangkok, 2011) presented a study under more practical conditions showing that under (milder) heat stress conditions (31°C, ±85% relative humidity) in conventional broilers, the same effects can be expected. More importantly, he showed that these results could be obtained using betaine hydrochloride and thereby gave practical proof that betaine hydrochloride has similar osmoregulatory properties as an anhydrous source.
Betaine has been used in broiler nutrition for many years. Scientific proof has been provided to show that betaine improves production performance, to replace other methylgroup donors; to assist birds during heat stress and to improve slaughter characteristics. Many of these published articles were not clear on the source of betaine used (natural or synthetic), and concern was raised if the synthetic form would be as effective in osmoregulation as the natural equivalent from sugar beet extraction. The presented data clearly shows that if a proper crystalline betaine hydrochloride is used, its molecular structure is similar after gastric passage as betaine anhydrous. Care should be taken that the product has good free fl owing properties and is non-hygroscopic. Practical application trials with birds fed betaine during heat stress clearly showed the expected improvement and therewith the mode of action of betaine hydrochloride as an osmoprotectant. Different strategies to replace choline and methionine were evaluated and may give tools to nutritionists to define the optimal strategy to include betaine in the diet. In the past many nutritionists evaluated betaine as a feed additive. With a new form of betaine (betaine hydrochloride), the year around availability has increased, since its production is independent to sugar beet production. Secondly, as the cost price is generally lower than that of betaine anhydrous, the applications of betaine in broiler nutrition may be reconsidered.
References are available upon request from the AllAboutFeed desk
AllAboutFeed.net – Vol 20 – Nr 2 – 2012