Physiological Changes during Thermal Stress in Buffalo

1 2Assistant Professor, Associate Professor, Department of Veterinary Physiology and Biochemistry College of veterinary Science, Rampura Phul Guru Angad Dev Veterinary and Animal Sciences University, Ludhiana

One of the greatest challenges facing producers and livestock around the world is heat stress. Heat stress strongly affects animal bioenergetics, with adverse effects on the performance and well-being of livestock. Heat stress is one of the most important stressors in hot regions of the world and adaptation to heat stress requires the physiological integration of many organs and systems viz. endocrine, cardio respiratory and immune system. Buffalo are more vulnerable to suffer heat stress when exposed to radiation and access to a wallow or cooling shower. They are less tolerant of heat and cold extremes than cattle of different breeds. Despite the buffalo's body temperature being lower than that of the cows, its black skin absorbs too much heat and the density of sweat glands in its skin is only one-sixth that of the cow's skin. Buffalo are at greater risk of heat stress due to sweat glands, dark color and sparse hair on the surface of the body. Moreover the sweat glands of buffalo skin have a low blood supply. The number of sweat glands per unit area of skin is about one third of that of cattle and the thickness of corneal layer and epidermis is about double that of cattle. This suggests that buffalo like to wallow in the water when temperatures and humidity are high. There is general agreement throughout the literature that buffalo are insufficiently heat tolerant and reports indicate that milk yield, growth and fertility are all reduced during periods of high ambient temperature. Heat stress represents one of the most factors for impairment of infertility in tropical and subtropical countries and need effective applicable strategy to beat the harmful effects of heat stress. Regulation of blood heat during this way affect feed intake, reproduction, and milk production. When animals are exposed to stress for long duration (chronic stress), they try to acclimatize in the adverse condition. Acceleration involves phenotypic responses to environmental changes, which are reflected in hormonal signals, and also changes in target tissue response to hormonal stimuli. The time requiredforaccretionvariesaccordingto the type of tissue, and changes in metabolism in response to heat stress over a few days to several weeks, for example. Alterations in physiological responsestothermalstresswasfoundto be within 24-48 h within the Egyptian buffaloestopermitacclimatizationofthe animal against severe condition under artificialconditionat40°Cand25°C. I n A s i a h i g h e n v i ro n m e n t a l temperature, hot humid summer and dry seasons, has led to low and inconsistent availability of feed and nutrients throughout the year; therefore, producing adverse effect on rumen metabolism as well as production performance of buffalo. However, many technologies are required to improve milk production of dairy cattle in the tropics. Many studies are wiped out attempting to enhance dairy productivity by management strategies in high environmental temperatures. Environmental modification is that the commonest to scale back the impacts of heat for increase milk production, for instance water spray with fans or evaporative cooling system. Experimental evidence has indicated that for maintaining proper homeothermy, the buffalo should be provided with a wall or shower during the summer months and drafts from the cold should be avoided during the winter months. Buffalo is well suited to hot and humid climates and muddy terrain, but they exhibit signs of major distress when exposed to direct solar radiation or working in the sun during hot weather. This is often because buffalo bodies absorb radiation to their dark skin and sparse coat or hair, and additionally thereto they possess a less efficient evaporative cooling system thanks to their rather poor sweating ability. Exposure to buffalo at high ambient temperatures leads to drastic changes in biological functions, including depression in feed intake, efficiency, and utilization, disturbances in the metabolism of water, protein, energy, and minerals, changes in enzymatic responses, hormonal secretions, and blood contains metabolites. Studies conducted to improve management using the c o o l i n g s y s t e m a n d f e e d management have helped reduce some of the negative effects of heat stress on buffalo production, however, productivity during the summer continues to decline.

The water ox has just one / 10th the amount of sweat glands per unit area of skin compared to zebu cattle and must believe wallowing or wetting of the skin during hot conditions to scale back the warmth load. Air temperature (13-18 °C), RH (55-65%) and wind velocity (5-8 km/h) are the optimum conditions for buffaloes as suggested. In terms of THI, the values of THI > 72 is considered as stressful and THI > 78 is considered very severe heat stress to the buffaloes.

Physiological parameters like respiration rate, pulse, rectal temperature and skin temperature gives an instantaneous response to the climatic stress of discomfort/comfort to the animal. Increasing air temperature above the critical threshold results in reduced feed intake, decreased activity, milk yield and a deleterious effect on the physiologic status of farm animals. Rectal temperature fluctuates far more in buffaloes than in tropical cattle with changes in ambient temperature. The greater sensitivity of the buffalo especially when exposed to direct radiation might be thanks to the dark body, lesser density of sweat glands and the thick epidermis which reduce evaporation. Furthermore it's been established that water excretion rate through urine in buffaloes is above in cattle which buffaloes have a greater dependence on external water because of the evolutionary adaptation of buffaloes to wet environments. Rectal temperature fluctuates far more in buffaloes than in tropical cattle with changes in ambient temperature. The greater sensitivity of the buffalo especially when exposed to direct radiation might be thanks to the dark body, lesser density of sweat glands and the thick epidermis which reduce evaporation. Furthermore it's been established that water excretion rate through urine in buffaloes is above in cattle which buffaloes have a greater dependence on external water because of the evolutionary adaptation of buffaloes to wet environments. The rectal temperature and respiratory rates were significantly higher during radiation within the noon time than the values obtained when the animals were kept under shade in the barn. Therefore, when kept within the barn RT within the thermo neutral zone at the expense of upper rate of respiration. Change in rectal temperature has been considered an indicator of warmth storage in animal's body and should be wont to assess the adversity of hot environment which may affect growth, lactation and fertility of dairy animals. RT increase from 37.9 to 41.2˚C when buffalo calves were exposed from THI 65 to 80. The RT of buffaloes significant increase when exposed to higher temperature (37.54°C vs. 38.77°C) of 40°C as against 25°C.The rectal temperature and respiration rates of lactating buffaloes were significantly higher during direct sun exposure (THI 77.83) than the values obtained when the animals were kept under shade in the barn. The rectal temperature of b u f f a l o h e i f e r s va r i e d f ro m 38.16+0.20ºC to 40+0.24ºC in pre exposure to 4 h after exposure at 45ºC, respectively. An evaporative heat loss from the tract is considered one among the first mechanisms for maintenance of warmth balance.This respiratory response arises from direct heat stimulation of peripheral receptors which transmit nervous impulses to the thermal centre in the hypothalamus. The cardio-respiratory centre is then stimulated to send impulses to the diaphragm and intercostal muscles for further respiratory activity. A high RR in most cases did not necessarily indicate that the animal is successful in keeping its body temperature constant, but rather indicated that it is already overheated and trying to restore normal heat balance. Respirationratewastheindicatorofheat stress in the hot environment and has significant correlations with circulating corticosteroid concentration. Normal respiration rate of buffaloes is approximately 10-30 breaths/minute. The respiration rate appears to be the mostaccessibleandeasiestapproachfor evaluating the degree of heat stress in farm animals (low: 40 – 60 breaths per min, medium high: 60–80, high: 80–120, and severe stress: above 150 breaths per minute in cattle. The respiration rate increasefrom14to70breaths/minutein the month of June in Murrah buffalo calves after 6 hours exposure to direct sunlight. Pulse rate did not exhibit consistent and a definite trend with changing environmental conditions. The pulse rate increased moderately during exposure to hot environment in buffaloes with a higher pulse rate during summermonthsandlowerduringwinter months in Indian buffalo bulls. The pulse rate increase with an increase in ambient temperature and relative humidity. The pulse rate increase when the crossbred malecalvesweregiventreadmillexercise duringhotdryseasonoftheyear. The outermost surface of the skin, fur, or feathers, the shell of an animal, is the transducing surface across which the environment interacts with the internal physiology of the animal. The skin temperature of buffaloes with increased environmental temperature. increase in ST at the end of four hours exposure in climatic chamber in Murrah buffaloes. Lactating animals exhibit increased respiration rate and pulse rate and decrease in milk yield and feed intake during summer season. There were increases in rectal temperature from 38.5 to 39.7°C when swamp buffalo and cows (340–375 kg, 4–7 years old) were subjected to acute heat exposure (41°C; without wallow) for5h. r