KEY NOTE ON SUMMER STRESS MANAGEMENT IN LIVESTOCK

July 4, 2021

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SUMMER STRESS MANAGEMENT IN LIVESTOCK

Dr. Sudhanya Nath

PhD Scholar, Dept. of Animal Nutrition, West Bengal University of Animal and Fishery Sciences, Kolkata – 700037

Corresponding author – sudhanyanath@yahoo.com

Abstract:

Stress is a reflex reaction of animals in harsh environments and causes unfavourable consequences ranging from discomfort to death. Climate change is one of the major threats for survival of various species, ecosystems and the sustainability of livestock production systems across the world, especially in tropical and temperate countries. Stress due to rise in temperature lowers the feed intake, production and reproductive efficiency of dairy animals. Therefore, proper stress management is essential to lower economic losses to farmers. Adequate housing management, water availability, alterations in feeding time and feed formulation can aid in lowering the effects of thermal stress.

Key words: Stress, Livestock, Management, Feed, Effects

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Introduction:

Heat stress is a form of hyperthermia (elevated body temperature) in which, the physiological systems of the body fail to regulate the body temperature within a normal range. Heat stress in animals is considered to be violation of animal welfare and rights. Elevated environmental temperature and relative humidity are responsible for heat stress. The aftermath of heat stroke may lead to severe damages in terms of general health, immunity and productivity of farm and draught animals.

Signs associated with heat stress in animals:

increased effort breathing or difficulty breathing;
excessive panting;
drooling;
bright red gums;
anxious behaviour, which includes
agitation and excess barking;
excessive water consumption;
vomiting or diarrhoea;
weakness, dazed expression or incoherent behaviour; and
collapse or seizure.

Causes of Heat Stress:

Animals may be prone to heat stress due to higher environmental Temperature-Humidity Index (THI), solar radiation and lower wind speed in summer season. Heat exhaustion may be attributed to several etiologies.

Environmental factors:

(i) Recent rainfall and subsequent rise in humidity leading to decreased sweating and breathing for heat dissipation.

(ii) A high on-going minimum and maximum circulating temperature and/or high environmental humidity.

(iii) A high solar radiation level due to absence of natural cloud cover may predispose animals to heat stroke.

(iv) Extended period (> 5 days) having minimal air circulation leading to consistently harsh environment.

(v) Warm cloudy nights might also increase the risk of heat stroke as the animals dissipate the heat energy during night.

(vi) A sudden shift to adverse climatic conditions might also predispose animals to heat stress

(vii) Husbandry practices and farm layout may sometimes facilitate the onset of heat stress in animals.

Characteristics of Animals:

Some characteristics of animals might be responsible for higher incidence of heat stroke along with environmental factors:

(i) Breed: Indigenous breeds (Bos indicus e.g. Sahiwal) are more heat tolerant than exotic breeds (Bos Taurus e.g. Ayrshire). Similarly, Brachycephalic anatomy (flat-faced breeds) such as Pugs, English & French bulldogs, Persian and Himalayan cats are among other breeds which are not heat tolerant.

(ii) Genetic variation: Variations attributable to the phenotypes of individual animal breeds.

(iii) Coat colour and type: Animals with lighter coat colour (e.g. cattle vs. buffalo) tend to be more tolerant of heat. Animals having coarse hair type as coat may be more prone to heat stress (e.g. sheep vs. goat).

(iv) Body condition: Obese and emaciated animals tend to be more susceptible to heat stroke.

(v) Age: Animals that are recently weaned or aged animals are more prone to heat stress.

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(vi) Adaptation: Indigenous animals might adapt to local climatic conditions, provided the temperature change is gradual.

(vii) Disease: Animals having ailment of any etiology might not be able to adapt to changes in the weather.

(viii) Physiological State: Lactating animals or peri-parturient animals might be at higher risks of getting affected by temperature or humidity rise due to their hormonal profiles.

(ix) Vector Density: Some flies and mosquitoes might cause nuisance to animals, leading to overcrowding/ huddling towards vector free areas.

Symptoms of Heat Stress:

Increased panting, hypersalivation, gastrointestinal problems (vomiting, diarrhea) might be noticeable.
Behavioral changes like seeking shade, crowding towards shady areas, orientation avoiding contact with solar radiation, standing in or next to water source might be observed in animals having onset of heat stroke.
Productivity parameters like milk production, egg production, weight gain, FCR, milk and meat composition (decline in protein and fat contents) might show abrupt changes in heat stressed animals.
Drop in routine feed consumption and sudden increase in water intake might signal the onset of heat stress.
The later stages of heat stressed animals might exhibit symptoms like dry and hyper congested mucosal surfaces (epistaxis might be seen in cats), listlessness/lethargy, staggered gait, general weakness and electrolyte loss from the body.
Neurological symptoms might include irritability, delusions, hallucinations, seizures and coma.

Heat Stress Proteins:

Heat Shock Proteins (HSPs) have a critical role in the recovery of cells from stress and in cytoprotection as well as guarding cells from subsequent insults. Hsp gene expression under thermal stress changes include:

activation of heat shock transcription factor 1 (HSF1);
increased expression of Hsp genes and decreased expression and synthesis of other proteins;

increased glucose and amino acid oxidation and reduced fatty acid metabolism;

endocrine system activation of the stress response;
immune system activation via extracellular secretion of Hsp.

If the stress persists, these gene expression changes lead to an altered physiological state referred to as “acclimation,” a process largely controlled by the endocrine system .

How to manage summer stress:

Instructions should be given to farmers to lessen heat stress Methods to decrease heat pressure are oversee mental practices and healthful remedy. Under managemental practices, accentuation ought to be given on proper water supply, legitimate creature lodging to diminish or to manage heat pressure. Dairy animals need to increase water intake during season of heat stress to disseminate heat by evaporation or panting.

Proper housing:

Legitimate animal housing in Indian conditions ought to be designed to decrease the warmth load since heat stress cause more harm to creatures contrasted with winter. Animal can endure winter condition up to 15℃ without any trouble. Yet, the temperature above 30℃ has outcome in drop in milk production and rearing efficiency. Therefore our dairy cattle’s extraordinarily crossbreds must be provided with legitimate lodging. Shade of trees gives an optimal assurance from brilliant warmth, but do not fit as a result of other reasons. Principles for establishing an ideal miniature climate inside an around the sheds are directed to decrease heat acquire and advance warmth misfortunes from structure of creatures house by radiation and condition. The following guidelines should be considered:

Orientation:

Shed with its long axis running East – West provides a cooler climate than one with a North-South orientation. In the East-West oriented shelters animals get greater freedom for radiation exchange with cooler north sky. The shed is shaded for a more part of the day resulting into lower floor temperature.

Shelter design:

Open kind of sheds enjoys upper hand over closed type shed. Mean temperature and least temperature in close shed was essentially higher than those of open type shed. The close type of shed essentially contributed to higher encompassing temperature during both hot dry and hot humid months i.e., from April to September.

Size, width and height of shelter:

Marginally more concealed region than the minimum recommended floor space needed for various species of domesticated animals ought to be given in blistering dry environment. Floor space prerequisite for calf is 1.5 to 2 m², adult male 7.0 m² and for adult female is 4.0-5.0 m². Optimum width of the shelter is 5.0-6.0 m. Minimum roof height should be 10.0 feet to reduce heat load. Height of shelter in hot climate should be between 3.0 – 5.0 m. A height less than 3.0 m interferes with proper ventilation resulting into reduced convective heat loss from animals.

Roof of the housing:

The shape of the roof can be either flat, slopped or “A” shaped. “A” shaped roof is definitely better than a flat roof in hot climate. It may be roughage or straw, plywood and a few kinds of plastics can be used as roofing material. On a typical summer day contrasts in radiant heat load under sheds covered with straw or plastics. The surface of the hay, due to its lopsided surface is likewise high. Hay thatch is more reasonable for hot dry environment than hot humid environment (need for regular expulsion of thatch is limiting factor). Wood makes great shed material but in it cracks often develops thus results in frequent treatment. Asbestos sheet are more viable as top layer in double roof cover.

Shelter Surroundings:

Surface around shelter are very important in view of radiation exchange between different surfaces and the shelter. The temperature of different surfaces varies significantly at same air temperature. It is clear that green surface do not heat up as much as other surfaces like gravel or loose loam. It is difficult to maintain green vegetation adjacent to animal shelters. It may be possible to increase animal comfort by selection of proper type of unvegetated ground surface. These vary significantly in view of the difference in reflectivity, thermal conductivity and density etc.

Ventilation:

Proper ventilation must be provided for controlling the effect of heat stress.

Colour of roofing and wall:

It ought to be white outside and hued inside. Reflectivity of white tone is around 75%. The reflectivity of the under surface ought to be less than the amount of accidental energy from the ground which will be reflected down to the animals. Radiant heat load on the under surface of an aluminium rooftop having white paint on top and velvet – black inside was observed to be about 13 BTU/ feet² /hour less than unpainted roof made of the same material.

Feeding:

While taking care of animals during hot climate, focus should to be made on feeding frequency and time of feeding (cooler time of a day, satisfactory feeding space and a lot of cool water). Adjustment in ration can help to limit the drop in milk production, decreasing forage to concentrate ratio, result in more digestible rations. Taking care by providing buffers for e.g., sodium bicarbonate and magnesium oxide permit higher concentrate rations and can help in low fat milk syndrome too. Hot climate builds the need of certain minerals. Try not to overfeed animals with highly degradable protein during warm climate; it ought to be 18% or less. Supplemental fat can be included in ration to increase energy intake. Additionally abstain from taking excess fat, as overfeeding causes issue with rumen function. Supplementing additional vitamins during summer has no added advantage.

Cooling systems for animals:

Ascend in ambient temperature initiates sweat glands to produce sweat. Every gram of sweat evaporated from skin uses 590 calories from skin surface. This process of vanishing causes cooling of skin and increment their respiration rate. Breathing of animals at a quicker rate to combat heat stress prompts panting. To lessen the metabolic heat load, animals reject feed and fodder. Use of water as cooling specialist either straightforwardly on animal body or for cooling the shelter microenvironment is generally practiced. Water can be utilized for showering the floor and top of shelter periodically or persistently during top hot hours which lower their temperature reducing the heat load on animal. During summer, we can lessen heat load on animals artificially by splashing little amount of water on their body at repeated time interval of 15-30 minutes. Fans or blowers fitted in cow can help in expanding rate of evaporation of water. Skin cooling to the degree of 8-15℃ is accomplished relying on relative humidity. Each gram of water evaporated removes 560 calories of heat.

Effect of zero energy cooling:

Cows approaching sheds with evaporated coolers had marked higher reproducing efficiency than cows approaching just regular conventional sheds. The milk production from group maintained under cooled shed was 1.8 kg more per head than in conventionally shed group.

Treatment of Heat Stress:

Heat stress might cause serious damage to muscles/ internal organs of affected animals, indicating the need for emergency medical care.
Animals should be made to move away from direct sunlight to cool area. Continuous application of cool water therapy is highly indicated to manage a heat stressed animal.
Management of hyperthermia is very important along with cardiovascular support. Fluid, electrolyte and Vitamin C therapy could be applied to counteract the ill effects of heat stroke especially in farm animals e.g. poultry.
Intravenous (i/v) corticosteroid therapy may help in reducing myocardial stress. Anti-microbial therapy may be indicated to reduce chances of secondary infection.

Conclusion

Heat stress in dairy animals can challenge their conceptive and production efficiency. Executing legitimate rearing projects, cooling systems at ranch with better management of projects can assist with limiting a portion of the adverse consequences of heat stress. It is not in our hand to control the environmental variations in temperature, humidity and wind circulation to counter heat stroke cases. Hence, appropriate farm layout, close monitoring, adopting appropriate preventive measures, adequate management and planning before the onset of environmental temperature and humidity rise play a major role in reducing the summer heat stress in livestock.

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