Oxidative stress in poultry
Poultry is one of the fastest growing segments of animal industry and has a substantial contribution to food security and nutrition. Birds are exposed to a multitude of stressors of environmental, nutritional, microbiological, and managemental origin throughout their life cycle that negatively impacts their health and production (Altan et al., 2003). These include sexing, transportation, vaccination, heat, cold, light, peak production, intensive production system, overcrowding, feed withdrawal, modern animal breeding practices and many more. High ambient temperature is one of the most challenging environmental stressors associated with poultry production (Lara et al., 2013). Heat stress has been shown to alter feed intake, poor growth performance, immunosupression, hypoxia, and high mortality. Heat stress also deteriorates meat and egg quality (Farag et al., 2018).
Oxidative stress is downstream of all these stressors. It causes redox imbalance between the pro- and anti-oxidants in favor of prooxidants and leads to lipid peroxidation, proteolysis, DNA damage, and apoptosis. Both reactive oxygen species (ROS) and reactive nitrogen species (RNS) at certain levels are signaling molecules involved in homeostasis. However, excessive production of ROS and RNS or their inefficient scavenging leads to oxidative stress. Exposure to concomitant stressors can have an additive effect, impacting immune response, growth, production and performance (Chang et al., 2006). Thus, it is essential to mitigate stress in order to minimize morbidity and improve both production performance and animal welfare. Dietary modifications are among the most preferred and practical ways to alleviate the effect of stressors in poultry including heat stress (Surai et al., 2017).
Antioxidant supplementation for stress mitigation
Antioxidants are widely used to maintain physiological functions and for stress management in intensive poultry production system (Konca et al., 2009). Despite all poultry species having the ability to synthesize vitamin C in the kidney or liver, exogenous vitamin C is reported to improve productive performance, reduce blood cortisol levels and potentiate immune response. Several other antioxidants such as synthetic vitamin E, selenium, prebiotics, natural antioxidants are also given to birds to mitigate stress (Lagana et al., 2007). A number of natural phytobioactives are well known for their antioxidant activity viz. gallotannoids (Surai, 2002). Gallotannoids are low molecular weight hydrolyzable tannoids found in plants [Phyllanthus emblica fruit (Amla)] with a structure similar to that of the vitamin C. Whilst the active pharmacophore of synthetic vitamin C and gallotannoids is identical, the ant-oxidative activity of gallotannoids is higher than synthetic coated vitamin C as reported in scientific literature (Poungpong et al., 2019).
Stress mitigation with ‘Herbal C’
Herbal C* is phytogenic poultry feed supplement (PFS) and a natural, heat stable antioxidant. Herbal C contains natural vitamin C in free state and in conjugation with other phytobioactive molecules of high antioxidant potential that acts synergistically to provide high bioactivity, stability and bioavailability of vitamin C (Goshal et al., 1996). The unique composition Herbal C differentiates it from synthetic vitamin C and has several advantages over synthetic vitamin C and other antioxidants (Poungpong et al., 2019).
Highly bioavailable and sustained activity: The unique array of phytoingredients and composition Herbal C is liable for self-replicating, sustained antioxidant activity and higher bioavailability (Chatterjee et al., 2006).
Highly thermostable at pelleting temperature : Active moiety of synthetic vitamin C is thermo-labile and gets quickly dissipated in aqueous solution. Retention and activity of synthetic vitamin C is reduced by 10% every month during storage at room temperature and by more than 80% during pelletization. In contrast, active pharmacophore of Herbal C is naturally conjugated with other phyto-molecules, it remains stable in aqueous medium, during storage at room temperature and also under pelleting temperature with sustained bio-activity.
Universal antioxidant: Natural vitamin C acts as universal antioxidant that protects both aqueous & lipid phase of cells whereas synthetic vitamin C is active in aqueous phase only, leaving lipid phase unprotected. The activity guided bio-assay for antioxidant activity of Herbal C powder has shown it to be potentially and significantly higher as compared to synthetic vitamin C (Muruganandam et al, 2002).
Pharmacological equivalence studies in laboratory animals have shown comparable vitamin C level in blood and adrenal glands (store house of Vitamin C in the body) in Herbal C group and found to be non-significantly variable from synthetic vitamin C group (Singh, 2006).
Clinical studies in broilers exposed to concomitant stressors including heat stress revealed significant improvement in performance indices (EPEF), zootechnical and antistress parameters besides reduction in mortality (Nagra, 2004). Supplementation of Herbal C significantly improved growth, plasma ascorbic acid level and immune-competence in chicks and growers (Tudu, 2005).
Supplementation of Vitamin C is known to improve calcium absorption and calcium reserves in commercial broilers and laying hens (Giang & Doan, 1998; Sahin et.al., 2002). Supplementation of Herbal C was found to increase bone calcium and phosphorus content, tensile and compressive strength of femur, weight, length and volume of femur, sternum weight, chest girth and shank length in layer chicks and growers (Tudu et al., 2006). Findings of Chatterjee et.al. (2006) are in corroboration and it was reported that Herbal C supplementation improved bone mineralization in commercial broilers.
In a recent investigation undertaken in commercial broilers at Dept. of Animal Science, Faculty of Agriculture, Kesatsart University, Thailand, (Pounpong et al., 2019), it was reported that supplementation of Herbal C in birds exposed to multiple stressors (exposure to temperature of 31°c for day 8th-35th and 33°c for day 36th-42nd), (High stocking density of 12 birds/pen) revealed significantly better results than synthetic coated vitamin C for zootechnical parameters, production efficiency index, reduction in stress hormone and improvement of IBV tires (Table 1).
Herbal C is natural antioxidant that can help meeting nutritional requirement of vitamin C in poultry and livestock, more particularly during summer and other stress conditions and in first two weeks of life in chicks. In face of stress challenges, Herbal C supplementation ensures optimal physiological functions, increased immunocompetence, attainment of homeostasis through its adaptogen activity, improvement in production and performance in broilers and layers, restoration of fertility and hatchability in breeders, control of morbidity and mortality. Several unique advantages of Herbal C over synthetic vitamin C makes it the perfect choice for alleviation and management of oxidative stress in poultry.
(Note : *Herbal C is also sold and distributed as ‘C-Power’)