Indian Journal of Animal Sciences 93 (6): 649–654, June 2023/Short communication https://doi.org/10.56093/ijans.v93i6.132297 Vitamin C supplementation ameliorates summer stress and improves antioxidative status of commercial layer reared in Mizoram RUPAS KUMAR DEBBARMA 1 , M AYUB ALI 1 , M C LALLIANCHHUNGA 1 , H DAS 1 , G KALITA 1 , T C TOLENKHOMBA 1 , R GOSWAMI 1 and P MAYENGBAM 1* Central Agricultural University, Selesih, Aizawl, Mizoram 796 014 India Received: 15 January 2023; Accepted: 2 May 2023 Keywords: Antioxidants, GPX, HSP70, SOD, Summer stress, Vitamin C Present address: 1 College of Veterinary Sciences and Animal Husbandry, Central Agricultural University, Selesih, Aizawl, Mizoram. * Corresponding author email: prava.mayengbam@ gmail.com The growth and productive performance are greatly affected by the high ambient temperature and relative humidity (Khan et al. 2014). The deleterious effects of high ambient temperature are more when combined with humidity (Ajakaiye et al. 2011). Increased mineral excretion, decreased serum vitamin, mineral, and insulin levels as well as increased serum glucose, total cholesterol, and corticosterone levels are further effects of high ambient temperatures in poultry (Gorman and Balnave 1994, Siegel 1995). The heat stress marker, HSP70, has been extensively used to analyse and estimate the impacts of thermal stress in different species of animals including chicken. Commercial layer chicken reared in Mizoram and indigenous chicken of Mizoram have been shown to suffer cold stress in winter and increase their respective concentration of heat shock HSP70 during cold stress (Khukhodziinai et al. 2022, Ralte 2022). Poultry are renal synthesizers of vitamin C (Maurice et al. 2002) and poultry diets are not normally fortified hence, no recommended requirement is established by the NRC (1994). However, during the severe environmental conditions, the endogenous production of vitamin C is usually considered not sufficient for the biological demands in poultry and vitamin C supplementation provides benefit to poultry (Pardue and Thaxton 1986). Mizoram located at 1020 m altitude and 23 o 44’12N latitude enjoys a pleasant climate throughout the year except for a brief period of winter between December and January and presence of high humidity during the months from July to August. Supplementation of vitamin C have been found to alleviate the effects of cold stress of layers reared in Mizoram (Khukhodziinai et al. 2022). The present study aimed to find out the impact of summer stress on commercial layer during grower stage ascertain out the effects of vitamin C supplementation on stress and antioxidative status of layer reared in Mizoram during summer. The study was carried out in commercial layers (BV300) reared in Poultry Unit, Instructional Livestock Farm Complex, College of Veterinary Sciences and Animal Husbandry, Central Agricultural University, Selesih, Aizawl, Mizoram. A total of 60 birds of 26 weeks old commercial layer were reared for two months during the periods from 27 th June to 26 th August 2022. The birds were divided into 2 groups, viz. control group and VC. VC was supplemented with vitamin C @ 250 mg/kg of basal diet. A basal diet @ 120 g/bird/day was provided to the birds during the whole period of the experiment. The basal diet consisted of 64.8% maize, 26.2% soybean meal, 3.5% fish meal, 2.21% rice bran oil, 1.26% dicalcium phosphate, 0.3% sodium chloride, 1.15% limestone powder, 0.27% methionine, 0.12% L-lysine, 0.045% L-threonine, 0.067% toxin binder, 0.067% trace mineral phosphorus, 0.017% vitamin premix and 0.067% choline chloride. Drinking water was provided ad lib. These birds were reared in cage rearing system. The period of study was divided into 2 phases, i.e. from 27 th June to 27 th July, 2022 (P1) and from 28 th July to 26 th August, 2022 (P2). Record of meteorological parameters: The ambient temperature (AT) and relative humidity (RH) were recorded during the 2 periods and the respective values were used for calculation of temperature humidity index. THI was calculated by using the formula developed by Johnson et al. (1962). THI = 0.08AT + RH (AT-14.4) 100 + 46.4 where, AT, Temperature in °C and RH, Relative humidity in %. Collection of blood samples: Blood samples were collected from each bird at three intervals, i.e. 0, 30 th and 60 th day of supplementation. Blood samples were collected by puncturing the wing vein of each bird by using 24 Gauze needle. Heparin coated blood collection vials were used for collection of blood. 109