Thyroid hormone dynamics of Tharparkar and Sahiwal cattle during induced heat stress.

Thyroid hormones and Cortisol level are the essential biomarkers in the assessment of stress condition. This study was done to estimate the metabolic hormonal profile of Tharparkar and Sahiwal during heat stress condition. The experiment was conducted on two groups consisting of Tharparkar and Sahiwal animals (5 in each group) and the experimental period comprised a 7-day acclimatization period, a heat exposure period of 21 days at control (25 °C), moderate (35 °C) and severe (42 °C) heat stress within a 9-10-day recovery period between each exposure. The hormonal concentrations of T3, T4 and cortisol were determined in serum. The serum concentration of Thyroxine (T4) and tri-iodothyronine (T3) decreases whereas cortisol level increases in both the breeds when subjected to heat stress. However, the serum level of T4 was significantly (p < 0.05) more declined in Sahiwal as compared to Tharparkar but there was no significant difference found between the two breeds in serum T3 levels. The cortisol levels were elevated in both breeds during heat stress but significantly (p < 0.05) more elevated in the Sahiwal. Hence, observations of these hormonal profiles suggest a better thermo-adaptability in Tharparkar as compared to Sahiwal.

Astaxanthin supplementation ameliorates simulated heat stress by regulating physio-biochemical responses in Sirohi goats.

The present study was undertaken to assess the ameliorative effect of dietary supplementation of astaxanthin in Sirohi goats under simulated heat stress conditions. Eighteen healthy female Sirohi goats were divided equally into three groups (n = 6): Heat-Stressed Control (HSC), Treatment 1 (T1), and Treatment 2 (T2). During the experiment, goats in the T1 group were supplemented with astaxanthin at the rate of 25 mg/animal/day, while those in the T2 group received supplementation of 50 mg/animal/day. The experiment was conducted for 42 days: 14 days of acclimatization period, next 21 days animals were exposed to 42ºC for 6 h from 09:00 h to 15:00 h and 7 days of recovery period. On a daily basis, we recorded the physiological responses of goats and collected environmental data at the experimental site. Blood samples were collected 0 and 14th days of acclimatization, on 1st, 6th, 11th, 16th and 21st day of heat exposure and on the 7th day of the recovery period. The rectal temperature and respiration rates of the treatment groups were lower than those of the HSC group during the exposure period. Heat stress in the supplemented groups was associated with reduced levels of hepatic enzymes such as AST and ALT. Serum urea, creatinine and albumin levels were significantly (P < 0.05) different between control and treatment groups. It was thus concluded that dietary inclusion of antioxidant astaxanthin can ameliorate induced thermal load as evident from changes in physio-biochemical parameters in the Sirohi goats, that was more prominent at 50 mg/ animal/day than 25 mg/ animal/day.