Role of Betaine in Poultry Production

Pratik Rajaram Jadhav, Amitav Bhattacharyya and Pankaj Kumar Shukla Department of Poultry Science, College of Veterinary Science and Animal Husbandry, DUVASU, Mathura (U.P.), India

Modern intensive poultry production has attained phenomenal progress in the efficient and economical production of quality safe meat and eggs. High ambient temperature is one of the most important problems for poultry production in many regions of India. Prolonged heat stress reduces visceral blood supply to the intestine and causes damages to epithelial cells in the gut there by affecting feed digestion and nutrient absorption (Cronje, 2007). It may also disrupt intestinal barrier increasing the likelihood of pathogenic bacteria and endotoxin entry, which can then result in excessive inflammation, decreasing production performance and possibly death (Quinteiro-Filho et al., 2012). Heat stress has negative impact on poultry production. Using feed additives having positive effects for resisting thermal stress may be a viable solution. Betaine has many important functions in the health and performance of broiler chickens, especially under conditions of heat stress. Betaine in reaction with the homocysteine has methionine saving effect, where it donates methyl group instead of methionine (Paniz et al., 2005). Betaine is an osmolyte and assists in cellular water homeostasis (Klasing et al., 2002). Betaine supplementation in feed improves growth performance and feed intake under heat stressed condition (Hassan et al., 2005). The positive effect of betaine is due to the fact that it reduces the body temperature in chickens (Klasing et al., 2002). Betaine as a natural plant extract has long been a known functional nutrient in poultry nutrition. Chemically, N,N,N- Trimethylglycine (TMG) is a neutral, zwitterionic, quaternary ammonium compound. This naturally occurring phytogenic feed additive compound is exceptionally high in sugar beet, also present in other plants viz. wheat, oat, barley etc. and in animals and seafood. Betaine was in the past mainly used as betaine anhydrous extracted from sugar beets; but, now it is available as betaine h y d r o c h l o r i d e o r b e t a i n e monophosphate, which is synthetically produced. Use of betaine as a feed additive in the poultry diet is one of the nutritional strategies for reducing stress in the broiler. It acts as a methyl donor through methionine recycling and as an osmolyte that helps in maintaining the cellular water balance which support animals to cope with water-related stress conditions (dehydration, diarrhoea, etc.) as well as helps reducing litter moisture that aids to overcome coccidiosis and stress. Besides, betaine has multiple functions: preserves gut integrity, improves carcass quality, spares choline and reduces the inclusion of methionine and increases nutrient digestibility. It can also be a lipotropic agent, causing reduction of back-fat to otherwise fatty animals (such as castrates), and can improve performance, notably feed efficiency.

Absorption and metabolism

Betaine is rapidly absorbed in the duodenum. Absorption of betaine is more rapid than choline or methionine. Choline and methionine are associated with plasma lipoprotein, whereas betaine remains in a free state in the plasma. It has 25% bioavailability, while 75% of it could remain at GIT intracellular level. Intracellular accumulation takes place via active (Na+ or Cl-) and passive (Na+) transport systems. Betaine is eliminated by metabolism, not by excretion, and catabolized via a series of enzymatic reactions that occur in the mitochondria ofliverand kidney cells.

Methyl group metabolism

Methyl groups are of vital importance in the metabolism of all animals, besides, animals cannot synthesize methyl groups and thus need to receive them in their diets. The methyl groups are used in methylation reactions to remethylate methionine and to formulate useful compounds such as carnitine, creatine and phosphatidylcholine through the Sadenosylmethioninepathway.Carnitineis required for transport of long-chain fatty acidsacrossthemitochondrialmembrane for oxidation. To generate methyl groups, choline can be oxidised to betaine within the mitochondria. Dietary requests of choline can be covered from choline present in (vegetable) raw materials and by the syntheses of phosphatidylcholine and choline once there is availability of Sadenosyl methionine. Regeneration of methionine occurs by betaine donating one of its three methyl groups to homocysteine,viatheenzymebetainehomocysteine methyltransferase. After donation of the methyl group, one molecule of dimethylglycine (DMG) remains, which is oxidised to glycine. Betainesupplementationhasbeenshown to reduce homocysteine levels while resulting in modest increases of plasma serineandcysteinelevels.Thisstimulation of betaine-dependent homocysteine remethylation and the subsequent decrease in plasma homocysteine can be maintained as long as supplemental betaineistaken.Ingeneral,animalstudies show that betaine can replace choline chloride with higher efficacy and can replace part of total dietary methionine, resulting in a cheaper diet for maintaining performance. Florou-Paneri et al. (1997) showed that between 30% and 80% of the supplemental methionine can be substituted by betaine without negative

effects on performance. Nofal et al. (2015) observed that interaction betweendietarymethionineconcentration and betaine supplementation influenced significantlybody weight gain (p<0.01) at 21 d of age and feed conversion efficiency (p<0.05) at 42 d of age.

Osmoregulation by Betaine

Birds maintain the intracellular concentration of water that is crucial for homeostasis by osmoregulation. Betaine is thought to be an important organic osmolyte for the control of the osmotic pressure inside the intestinal epithelial cells (Hochachka and Somero, 1984). These beneficial osmoprotective properties may be due to the dipolar zwitterion characteristics of betaine and its high solubility in water. This compatible osmolyte increases the cytoplasmic volume and free water content of the cells at high osmolarity, and thus permit cell proliferation that increase gut surface area (Csonka, 1989). It minimises water loss from cells against a prevailing osmotic gradient between cell and its surrounding environment. Additionally, betaine serves as a stabilizer of protein and cell components against the denaturing effects of high ionic strength. Betaine is highly companionable with cellular enzyme function and structural proteins and membranes. Betaine can raise cytoplasmic osmotic pressure in stressed cells by increasing the temperature and ionic tolerance of critical enzymes and cellular membranes (Hanson et al., 1994). The Na+ dependent active transport system of betaine is present in the duodenum and jejunum of broiler chickens. The concentration of electrolytes increases within the cell under dehydration. To regulate the desired concentration of water within the cell, K+ is pushed in to the cell against concentration gradient. To pump any ion against concentration gradient, one molecule of ATP is required. Higher concentrations of electrolytes in the cell are known to inactivate enzymes and proteins. The higher concentrations of the electrolytes bind with active sites of enzymes and thereby deactivate them. Movement of betaine across the cell membrane does not require energy and will not interfere with cell ecosystem or cell metabolism. Betaine in feed or drinking water can control osmoregulatory conditions including diarrhoea, catharsis, diuresis and ascites. The dietary betaine supplementation is necessary to improve the productive performance and reduce the negative impact of heat stress on viability and immune response by improving cell osmoregulation (Graham, 2002; Wang et al., 2004; Attia et al., 2005).

Heat stress

Heat stress impairs overall poultry production by decreasing feed intake and negatively affecting intestinal development, leading to reduced nutrient digestibility. Heat stress increases the production of oxidants, causing oxidative stress and lipid peroxidation of cell membranes. Disturbance in cell structure impairs nutrient absorption, cell membrane transport and certain intracellular metabolic processes. Due to its zwitterionic structure, betaine has osmoprotective properties that aid in protecting intestinal cell proteins and enzymes from environmental stress, including high ambient temperature, thereby counteracting performance losses. Betaine also exerts an osmoregulatory role in cells, regulating water balance, protect macromolecule from denaturation and this results in more stable tissue metabolism. Supplementation of betaine reduces heterophil-lymphocyte. In layers, heat stress can lead to respiratory alkalosis. As birds increase their respiration rate, blood CO2 level decreases and blood pH increases. Further, the activity of the enzyme carbonic anhydrase responsible for the transfer of carbonate ions from blood to the shell gland is reduced. Ultimately less carbonate ion will be available for shell formation and shell quality will be reduced. Therefore, nutritional adjustments during heat stress in layers are of outmost importance. Betaine can help to ease the negative effects of heat stress on the cells’ metabolic functions. However additional nutritional and management measures are also required to maintain shell quality. The effect of anhydrous betaine was tested with layers kept under chronic heat stress for 3 days a week (38 °C ± 1) at 32-48 week of age (Attia et al., 2016). Results indicated that addition of anhydrous betaine had the potential to restore performance of hens compared to the negative control treatment undergoing heat stress without any betaine in the diet. Higher laying percent and egg mass, slightly better FCR were observed in the betaine treated group. In addition mortality was reduced.

Nutrient Digestibility

During heat stress, there is an osmotic disturbance in broiler chickens while betaine improves the structural and functional characteristics of intestinal epithelia. Improved surface area and strength of gut epithelia increases secretion of digestive enzymes and absorptive area in the intestine resulting in better absorption of nutrients. Furthermore, betaine is involved in the metabolism of protein and energy. It stabilizes the mucosal structure of chickens by decreasing the crypt: villus ratio (Kettunen et al., 2001). Supplementation of 0.05%–0.15% betaine enhanced crude protein digestibility by up to 11.4% in broilers (Ratriyanto et al., 2014). Ezzet et al. (2011) reported that the digestion coefficient of crude protein significantly increased by supplementing layer diet with betaine (1g/kg diet).

Production performance

The variable response to betaine supplementation is likely due to the protein or methionine level of diets and differences in animals’ stress status. Also, the positive response might appear when chickens were fed a moderately methionine-deficient diet in the presence of coccidial challenge (Neto et al., 2000; Wang et al., 2004). It is a

chemical chaperone and helps to stabilize proteins in their natural conformation. Therefore, it may be helpful for survival of intestinal microorganisms under stress conditions. Furthermore, betaine acts as a modulator of nitric oxide synthesis, thus stimulating host defence and superoxide anion scavenging (Messadek, 2010). Several studies have been conducted to explore the use of betaine on poultry performance. Awad et al. (2014) found using betaine at levels of 0, 0.5, 1.0 and 1.5 g/kg diet, had significant effects on live body weights and body weight gain, feed intake, feed conversion ratio and viability rate. Shaojun et al. (2015) observed that birds fed diet with betaine-supplementation had a higher feed intake, body weight gain and better FCR. Likewise, improvements in feed conversion ratio ranging between 2.8% and 7.9% in laying hens and pigs were noted with supplemental betaine (Eklund et al., 2006 ).

Carcass quality

The improvement in percent lean meat yield may be endorsed by a higher availability of methionine and cysteine for protein deposition (McDevitt et al. 2000). It is well known that betaine has the ability to donate a methyl group donor for the synthesis of lecithin, which facilitates the transport of fat through the body. Due to the decline of the carcass fat content and an increase in the lean carcass, betaine is often considered as a “carcass modifier” . Betaine reduces protein turnover, which results in higher nitrogen retention, which in turn has a positive effect on accretion of protein in muscle (carcass leanness). In addition, betaine may improve the availability of choline, thus providing more choline for the synthesis of very low-density lipoprotein. Thus, another important feature of the addition of betaine in poultry diets is the lipogenic capacity, responsible for reducing abdominal fat and prevention of fat accumulation in the liver. Different studies have shown considerable changes in the carcass composition of poultry due to dietary betaine supplementation under a high ambient temperature by increasing the carcass weight, breast yield and breast–muscle ratio, in association with a reduction in abdominal fat deposition (Al Hassani, 2014; Ratriyanto, 2014). It has been noted that dietary 0.06%–0.20% betaine increases carcass weight up to 34.8% and breast yield up to 31.7% (Nofal et al., 2015).

Immune response

Reduction in the concentration of dietary methionine is known to affect immunity in chickens (Rama Rao et al., 2003), but methionine sparing effect of dietary betaine may influence the immune responses. Betaine increases endogenous methionine synthesis. Relative requirement of methionine may be reduced in broiler diets with betaine supplementation by sparing the methionine from a methyl donor function. Chand et al. (2017) reported improvement in immunity of birds by supplementing dietary betaine. Betaine at 1.5 and 2 g/kg feed resulted in significantly (P<0.05) higher antibody titer against ND as compared to the control group. Awad et al. (2014) reported that adding betaine in diets significantly increased the lymphocyte percentage where as Heterophil and H/L ratio was significantly decreased as compared to the control group.

Synergistic influence during Coccidiosis infections

Coccidiosis in avian species is an enteric disease, and the infection is associated with osmotic and ionic disorders, probably caused by dehydration and diarrhoea. Betaine is well known for its ability to help cells tolerate osmotic stress and allows them to continue regular metabolic activities in conditions that would normally inactivate the cell. Due to the osmoprotective properties ofbetaine, it has a stabilising effect on the intestinal cells in coccidia-infected chickens and reduces the pathogenic effects of the infection. Several studies have concluded the effect of betaine to an ionophorous coccidiostat and the positive effect on broiler production. Betaine, in combination with the ionophore coccidiostat salinomycin, has a positive effect on bird performance during coccidiosis. Betaine along with salinomycin in the diet reduced development of lesions by E. acervulina to a level that was lower than in chicks fed betaine or salinomycin alone. This suggests that betaine may contribute to the improved performance of coccidiainfected chickens directly, by partial inhibition of coccidial invasion and development, and indirectly, by supporting the intestinal structure and function in the presence of coccidial infection. This synergistic effect of betaine and ionophoric coccidiostat might be explained by the inhibitive effect of ionophoric coccidiostat on enzymes involved in transfer of choline to betaine, and therefore a higher requirement for methyl group donors as such.

Conclusion

Betaine has wide applications in poultry nutrition. Betaine does have an osmolyte function which helps the bird to maintain cell water balance. Betaine as a methyl donor spares some dietary methionine and choline that reduces feed cost per tonne, while maintaining the performance. Betaine may become better choice as feed additive especially in the high ambient temperature. It can be used in early chick nutrition to avoid starvation and reduce stress in chicks during transportation from hatchery to farm. Supplementation with betaine may be beneficial during certain challenging conditions including high demand of rapid growth, disease and osmotic stress. It improves the growth performance and acts as a carcass modifier. However, studies are needed to ascertain the effect of betaine in different species of poultry in different seasons. Further, it is also needed to a s s e s s t h e e f f e c t of d i e t a r y supplementation of betaine on heat shock proteins and expression of genes pertaining to production and immunity. r