Impact of Heat Stress on Buffaloes Health and Production: Management Strategies and Tips for Farmers to optimize milk production
Vasantha SKI1 and Nikhil kumar Tej. J1
1Assistant Professor, Department of Veterinary Physiology, NTR College of Veterinary Science, Gannavaram, A.P
What is heat stress
Heat stress is a major concern for all livestock production systems owing to its negative impact on health and production. It has been documented that India loses 3.2 million tonnes of milk production at present due to climatic stresses and global warming was further hypothesized to reduce milk production by 15 million tonnes by 2050. The major factors that contribute to heat stress are the ambient temperature (AT) and relative humidity (RH). Heat stress is the inability of the animal to lose heat to the surroundings resulting in accumulated heat load. As the ambient temperature rise above the body temperature the animal gains heat via conduction/convention/radiation resulting in accumulated heat load, while a high RH compromise animal’s ability to lose heat to the surroundings. However, animals being homeotherms operate numerous behavioural (shade seeking, orientation of body posture away from sunlight, wallowing, reduced motor activity) and physiological alterations including increased respiratory rate to promote evaporative heat loss and increased heart rate to deviate blood flow from the centre to the periphery to allow heat loss via skin. Despite of numerous efforts a continuous existence of stressor fails thermoregulatory mechanisms resulting in heat stress. Temperature humidity index (THI) is an equation that takes in to the effect of AT and RH and is used to determine the severity of heat stress. A THI value of 72 was considered to be comfort for animals while a rise in THI is indicative of heat stress.
Why Heat stress is of significance in buffaloes
Buffalo population in India comprises of 109 million which contributes to 50% of India’s milk production. Buffalo population contributes to livelihood of small, medium and large scale farmers all over the country. Despite of their high milk production, buffalo population in India is being constantly challenged by heat stress owing to hot and humid equatorial tropical climate and are insufficiently thermo tolerant compared to cattle due to differences in their heat regulating mechanisms such as black skin and less density of sweat glands. Heat stress results in depressed feed intake which is a thermoregulatory mechanism to reduce further heat accumulation, altered hemato-biochemical profile and deviation of energy for thermoregulation i.e less blood and nutrient flow to udder while deviate energy for heat loss mechanisms. These disturbances finally impairs production and reproduction parameters in buffaloes
Effect of heat stress on buffalo milk production
Milk production has been negatively correlated with AT, RH and THI. A unit rise in THI was found to decrease milk production by 0.2 to 0.9 kg while a temperature rise from 20 to 30◦ C decreased milk production by 9 % in Egyptian buffaloes. Similarly, the daily milk yield of Murrah buffaloes decreased from 4.46 to 3.65 kg by 18.2% as the THI increased from 74 to 83 in summer. Moreover, heat stress has profound effect on milk composition, exclusively in high yielding breeds. The metabolic heat produced during lactation results in reduced milk protein, lactose, milk fat, solids–not-fat (SNF), short-chain fatty acids while increasing long chain fatty acids in the milk. Recent reports evidenced a significant decline in milk fat and protein when THI rises above 60.
Effect of heat stress on buffalo reproduction
Heat stress had adverse effects on important economic traits in female buffaloes. THI is positively correlated with important economic traits of buffaloes such as age at first calving, dry period, service period, calving interval, incidence of silent heat, repeat breeding and anestrum while it is negatively correlated with pregnancy rate, conception rate, lactation length, milk yield, protein and fat percentage in milk etc.
Amelioration strategies to mitigate heat stress
Shelter Modification
- As buffaloes are dark and has less density of sweat glands they have more sensitive to heat stress. The preliminary strategy to combat heat stress must be shelter management.
- The animals must be provided with shade from direct sunlight under the trees or well ventilated permanent housing structures or temporary shade using portable shade cloth which can block radiation up to 50%.
- Painting of upper part of shade with white color and proper construction will help to decrease the heat stress
- Care should also be taken to provide enough space for all the animals to lie down and rest at the same time.
- Supplemental shade should also be provided for young calves.
- Shading reduces the radiant heat load by 30% or more and reduces deaths due to heat stroke.
- Shading of the feed and water also offers production advantage.
Managemental Modifications
- Fans may be provided inside the shed to lose heat via convection.
- Usage of sprinklers during the hotter part of the day or placing water dipped gunny bags on the back of the animal helps heat loss by convection and conduction.
- The animals should be provided with ample amount of clean drinking water in shade near loafing areas.
- When temperature, humidity and radiant solar heat are extremely high, it is advisable to increase the number of watering stations as the animals cannot travel more distance.
- The animals should not be handled and transported during hotter parts of the day, if necessary early hours are preferable to avoid the stress due to handling and transportation.
- It is advisable to feed concentrates during cooler part of the day and feed green roughages during hotter part of the day.
- High quality green forage should be provided in feed bunks in shaded areas to avoid moisture and vitamin loss due to heat.
- Providing wallowing tanks and allowing animals to wallow during the hotter part of the day helps to lose excess heat from the body.
- Maintaining the livestock in good health and condition resists heat stress to some extent compared to ailing animals.
- Managemental practices like, castration, dipping, shearing etc should be preferably done in early summer or during the early hours of a day.
- To lower body temperature cold water submersion, cold water enemas, ice applications, alcohol rubs can also be done.
- https://www.pashudhanpraharee.com/management-of-heat-stress-in-livestock/
Dietary manipulations
- Under heat stress animal usually reduce dry matter intake in order to reduce additional metabolic heat production. Thus dietary manipulations must be made in combination with management practices since feeding of high energy diet during hotter part of the day yields no improvement in dietary intake.
- It is important to provide balanced ration (1/4 concentrates and ¾ roughage) to the animals to get optimum milk production.
- Increase the nutrient density, feeding of high-quality forage low degradable protein and use of supplemental fats in the diet of animals.
- As heat stress induces oxidative stress, supplementation of vitamins A, C, E, and mineral mixture containing essential minerals such as zinc, selenium and chromium reduce the negative effect of heat stress on buffaloes.
As heat stress imposes significant threat to the survival of buffaloes, amelioration strategies must be widely adopted to combat heat stress. These practices stated above, alone or in combination must be adopted to reduce the adverse affects of thermal stress. Thereby the production, reproduction and health status of the animals are maintained and the optimum productivity achieved.
