Summer Stress Management of Livestock
Ranjan Kumar Mohanta
Subject Matter Specialist (Animal Science)
Krishi Vigyan Kendra, ICAR-National Rice Research Institute, Cuttack-753006, Odisha, India
Key Words: Heat, Humidity, Stress, Summer, Temperature, Thermoregulation.
Abstract
Stress particularly summer stress alters the normal physiology and metabolism of the body, particularly due to the exposure to high temperature, humidity and wind. It reduces the feed intake, production and fertility parameters thereby causing a huge economic loss to the farming community. To alleviate the effects of summer stress there is need to have a proper housing, provision of cooling mechanism and shades, modifying dietary composition and diet management and breeding principles. This not only helps in temporary relief from stress, but also helps to preserve the animals lifetime performance. Thus, there is a need to create awareness about the importance of summer stress management in livestock.
Introduction
Every organism particularly the homeotherms or warm blooded animals maintain a particular range of body temperature in spite of variations in ambient environment from time to time. It helps them to be active even in case of extreme variations in weather. However, the thermoregulation is a very costly and complicated process involving both internal and external factors (Nienaber et al., 1999). The animal remains in the thermal comfort zone at a particular range of temperatures like we feel ourselves at 25°C at our optimal comfort, beyond which it needs to give a sincere effort to generate heat (in cold environment) or loose heat from the body (in warm environment). Though the animals can survive effectively upto about 20-30 degree lowering of temperature, the heat stress or summer rise in temperature along with humidity creates a more problem and even endangers the life of animal. Temperature Humidity Index (THI) when exceeds 72 animal becomes stressed. In India, our tropical climate adds to the woes as in summer the temperature at many places even reaches upto 45°C along with dry or humid weather. The problem is becoming more severe as the high yielding animals particularly the cross bred animal population is on rise, which are more susceptible to the summer stress (Das et al., 1999).
In summer season, the ambient temperate in many places goes up to about 40°C which is more than the higher critical temperature for nearly most of the animals. This causes disruption in body thermoregulatory mechanisms as it needs extensive effort to remove the excess heat of the body to keep the body temperature at its normal range. The summer stress usually results in negative effect on growth, production, fertility and health, both directly through summer stress or indirectly through decreased feed intake and other associated complications. We also lose many livestock due to heat shock in summer. More than the loss, the decline in growth rate, milk yield, health traits and fertility due to summer stress causes heavy loss or economic effect to the farming community (Nardone et al., 2006). The effect may last for the whole life of the affected animal, i.e., a growing heifer if suffers heat shock in its pubertal stage, its productivity and reproductive traits may be affected for its whole life, thereby adding to the woes. Therefore, care of livestock is utmost importance to alleviate the pains and impairments suffered by them.
What is summer stress?
Summer season varies in terms of its severity and mostly commences in April-May and effects remain up to June-July. Summer stress mostly due to the high temperature (hot humid / hot dry) related stress. In extreme hot weather, the heat produced by eating, digestion, movement and normal body metabolism disrupts the capability of livestock to dissipate heat by sweating and panting (thermoregulatory mechanism). This results in heat stress (Fuquay, 1981). Animals remain in the comfort zone where all its metabolism remain normal at a particular range of temperature. If the temperature becomes higher than the higher range, i.e., the upper critical temperature the animal comes under heat stress, but if it goes down, cold stress is observed. This critical temperature varies for animals and breeds (buffaloes, 36°C; Zebu cattle, 33°C; exotic and crossbred cattle, 24°-26°C) as they respond differently due to difference in thermoregulatory mechanisms. In summer, when the temperature rises beyond the upper critical temperature, the animals thermoregulatory metabolism is disturbed and it is unable to maintain its core body temperature through sweating and panting. Increased heat stress further results in elevated body temperature and pulse rate in addition to increased peripheral blood flow and water intake (Nienaber et al., 1999).
General signs and symptoms:
In summer, when the stress level becomes severe and the animal is in heat stress, usually the following symptoms are observed. The animals vital parameters become abnormal, e.g., increased rectal temperature, heart rate and respiration rate etc. It prefers standing to lie down due to heated surface and seeks shade or place near water bodies. Due to increased heat production in the body the animal eats less, drinks more, produces more amount of saliva, pants with open mouth. It takes rapid, but shallow breaths and sometimes convulsions, unconsciousness and even death occurs (Mittal et al., 2019). Certain animals like buffaloes show the signs of reddening of hide on the brisket, under the belly and between the legs and blood shot in eyes. If temperature humidity index becomes and animal suffers from heat shock, the temperature of animal may rise up to 106–108°F.
Effect of summer stress
Summer stress affects the production, reproduction and health in various ways. Animals in summer stress depresses feed intake and subsequently affecting nutrient utilization. It leads to depressed growth rate in young animals or weight loss of adult ones. It decreases milk production both in terms of milk yield and milk composition (%) like milk fat, solids-not-fat and sometimes protein (Nardone et al., 2006). Summer stress elevates the somatic cell counts and prevalence of mastitis. Development of follicles and estrous cycle are affected thereby negative influence on fertility (Rensis and Scaramuzzi, 2003). The effect is more on buffalo, but most of the livestock breeds are affected with decreased semen quality, ovulation and conception rates in farm animals. The length of service and dry period increases in summer stress along with reproductive failures and embryonic mortality, especially in buffaloes (Devi et al., 2019).
Summer stress management strategies
Integrated management of cool/ thermal comfort conditions, proper feeding and nutrient management, breeding, fertility management and other managemental needs minimizes the effects of summer stress. The details of strategies are described afterwards.
Housing and cooling systems: Direct exposure to sun, hot dry/ humid winds and humid ambience should be provided to the livestock through various means. Provision of shed and well ventilated area particularly the tree shade helps the animals to feel comfortable. As temperate, humidity and wind play the major factors in summer stress the farm and animal shed should be well ventilated with enough trees to provide shade in the grazing and sitting areas (Krishnan et al., 2017). Animals usually prefer natural shade to artificial one. The animal sheds should be having cross ventilation with well sized doors and windows or open sidewalls. The roof if made in asbestos or tin, it should be thatched with straw or installed with a water sprinkling facility which has to be run at certain times a day depending upon the severity of summer stress. Fans should be provided along with the provision of straw, bamboo or jute bag mat/ curtain hanging at the open ends for the cooling effects and avoiding direct exposure to solar radiation. Provision of shade through plantation of shady trees around the farm particularly at the southern wall/boundary also helps in providing comfort to the livestock. The animals should be given sufficient space as crowding increases summer stress (Nienaber et al., 1999).
It is seen that painting of roof top and under surface with white and black along with providing a false ceiling insulation, helps in retaining less heat in the shed. Low height of roof makes the livestock life miserable, so minimum of 9 feet height should be provided. If the animals are left loose in the shed or at the barn, they can move freely and feel more comfortable outside than inside the sheds, as sheds or concrete buildings get heated up during the hot hours of the day. Cooling systems are very much needed particularly for the high yielding crossbreds and exotic animals (Mittal et al., 2019). If sprinkler is not available misting/ showering/ water splashing directly on the body of animals for a period of 1 to 5 minutes at an interval of 10-30 minutes or minimum 3-4 times a day and wallowing facility may be made available for the buffaloes. Wallowing is most effective in case of buffalo. It is the cheapest and least laborious mechanism where buffaloes are made to wallow in water bodies like tanks, ponds and rivers for hours together. Regular grooming and washing the livestock, should be done at least two hours before milking, followed by wiping of udder with clean duster soaked in mild/ diluted antiseptic solution.
Feeding Management
Summer stress directly affects the feed intake and nutrient utilization in the livestock. It may be to avoid generating enough heat to create heat stress through digestion and metabolism process in the body. Therefore, feeding management and dietary composition is one of the most important components to alleviate summer stress.
Dietary changes: Summer stress increases the requirement of certain nutrient concentration in the diet to overcome the decreased intake and increased demand of body to alleviate summer stress. As feed intake decreases during summer stress, the diet should have increased concentration of protein (higher nutrient density) and high quality forages preferably as total mixed rations. The succulent fodders like spineless cactus, azolla and hydroponic fodder may be given to supply both nutrients and water along with improving the appetite of the animals. The feed and fodder should be fresh and rich in nutrients (Krishnan et al., 2017). But, in reality this summer time fodder resources (green fodder and oilcakes) are scarce in nature except the dry roughages which are plentily available in some regions, but most of them are of low nutritional quality and digestibility. If possible, forage of high quality (emphasis on legumes) should be fed or low quality forage should be treated to make higher quality hay or silage and fed to the animals.
The ration should contain fodders and concentrate in the ratio of 70:30 in low yielding animals and may be increased to 60: 40 in high yielders. Higher proportion of concentrate will affect the rumen microenvironment and may result in acidosis, drop in pH and alteration in rumen fermentation. Therefore, adequate good quality fibre, with easily fermentable fiber and high digestibility, should be present in the diet. Presence of low-fibre and high fermentable carbohydrate in the diet results in lower dietary heat increment when compared with the high fibre diets. Use of local feeds like cottonseed meal, sugarcane tops, guar meal, wheat bhoosa, maize stovers, soybean staff, tree leaves, azolla, spineless cactus, agroindustry byproducts etc can be added to the ration of livestock. Prepared silage, urea molasses mineral block and urea treated straw may also be fed at the recommended doses. Cultivation of low water needing fodder crops like pearl millet (Bajra, Sorghum PC6 and MP Chari etc) and legumes (Moong, Cowpea BL1 and BL2 etc) as fodder and fodder grasses (like Stylo, Cenchrus ciliaris etc.) helps in the alleviation aspect.
In addition, it should have a buffer (sodium bicarbonate, magnesium oxide, calcium carbonate, bentonite and Lithothamnium calcareum), increased amount of vitamin-mineral mixture (Vitamin ACD3E and P, Cu, Zn, Se, Mn, Cr, Co) and potassium rich mineral mixture. Use of bypass proteins, certain feed additives like yeast, rumen enzymes, herbal supplements, essential oils, detoxifiers etc in the diet also help to stabilize the rumen pH, increasing the appetite and stimulating the rumen function may aid in overcoming the effect of summer stress.
Stabilizing Rumen: Rumen is a complex ecosystem with a near constant temperature of 39.1°C in the rumen fluid. The homeostasis is altered in summer stress due to inefficient heat out flow from the body leading to disturbances in rumen pH and temperature. In ruminant livestock like cattle, buffalo, goat and sheep, maintenance of rumen environment is the key to efficient rumen fermentation and efficient utilization of feed (Das et al., 1999). Supplementation of certain antioxidants and feed additives aids in gut barrier function, neutralise endotoxins in the intestine, improves digestibility, promotes feed intake and ensures proper liver function. They help to supply important nutrients to rumen microbiota (enzymes, amino acids, cell-wall carbohydrates, B-complex vitamins, and peptides, etc), which help to alleviate the effects of summer stress.
Changes in feeding schedule
In animals, abrupt change in feeding, watering and management plan should be avoided. It may further depress feed intake. Animals should be allowed to graze preferably during early morning and late evening hours (Das et al., 1999). Feed preferably in the form of total mixed ration should be offered during the cooler hours, i.e., early morning (30-40%), late afternoon, evening and night hours (60-70%) to avoid digestion and metabolic heat generation in the peak hours of scorching sun. Feeding frequency should be more (an extra feeding or two),
Water
Drinking of adequate clean and fresh drinking water enables the livestock to keep its production and reproduction traits near its optimal values and minimizes the effects of summer stress. The milch animals need more of water, for maintenance, production and thermoregulation purpose (Nienaber and Hahn, 2007). Therefore, adequate amount of clean and wholesome water should be made available at easily accessible places to the livestock round the clock. In day time, the water should be offered under the shade. The water troughs should be of sufficient numbers located near milking place, grazing area, travel alleys, feeding area and animal shed. The troughs should be cleaned regularly.
Genetic selection and breeding policy
In Cattle, the local or indigenous breeds are relatively more thermo-tolerant than the crossbred and exotic breeds of cattle (Holstein Friesian, Jersey, Brown Swiss etc.). The high yielding animals are more susceptible to summer stress (Fuquay, 1981). Buffaloes suffer more from summer stress than other species as it has about one sixth sweat glands than that of cattle, thereby less efficient in losing heat from the body. The black skin of buffalo absorbs more solar radiations thereby adding to the problems. This difference in response to breeds forced the policy makers to select breeds of heat tolerant animals based on specific molecular genetic markers.
Reproductive Management
Summer stress affects fertility traits directly through a complex mechanism and indirectly through decrease in feed intake. The heat symptoms are detected with difficulty as the signs of heat becomes lesser than normal heat signs (Devi et al., 2019). So, heat symptoms need to be observed minutely preferably thrice a day and at least once during night hours for the expected animals for cervical mucus discharge and its characteristics. Artificial insemination should be carried out between mid and late estrus period during cooler part of the day and night. Use of bulls is less preferred as summer stress also affects the semen quality. So, the heifers, buffaloes and bulls need to be provided enough care and management practices to provide thermal comfort, otherwise many young animals lose their optimal fertility traits to summer stress (Mittal et al., 2019). After AI, thermal comfort zone should be provided for a minimum 15 days period for better conception. Feeding of mineral-vitamin mixture should be a continued practice from 15 days before to 15 days after AI is done, if not regularly fed. Supplementation of mineral-vitamin mixture and other feed additives helps the animal to reducing age at first calving and calving interval which would have been severely affected by summer stress.
Treatment:
Awareness about the first aid while encountering summer stress is utmost necessary to the suffering animal. The affected animal should be attended immediately and shifted to a cooler place, preferably under a tree or shed with fan available nearby. It should be a well ventilated space. It has to be immediately bathed or sprinkled heavily with water or wrapped in wet gunny bags or cloth materials for cooling effect to be fast. This will help the animal loose the excess heat and become normal. The veterinary doctor available nearby should be consulted if the first aid does not work or in case of severe heat shock.
Conclusion
Summer stress alters the body metabolism affecting feed intake, production, reproduction and health of the livestock. High ambient temperature, hot winds and high humidity accelerate the adverse effects of summer stress in addition to solar radiation. Integrated managemental effects of adequate nutrition with changes in feed, feeding schedule and feeding management for better rumen function, provision of sufficient water along with proper cooling, housing, breeding and other management practices can help to provide a comfortable atmosphere in time of summer stress and keep the production and reproduction traits near optimal level.
References
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