SUMMER STRESS MANAGEMENT IN LIVESTOCK: A PRACTICAL APPROACH

SUMMER STRESS MANAGEMENT IN LIVESTOCK

Dr. Poonam Yadav

(PhD Scholar)

Department of Veterinary Physiology & Biochemistry

College of Veterinary Science and Animal Husbandry Jabalpur

NDVSU Jabalpur M.P – 482001

Corresponding author: poo90nam@gmail.com

Abstract:

In the changing climate scenario, heat stress seems to be the crucial environmental variable which decreases livestock production and fertility across the globe. Heat stress has long been known to affect animals comfort, health, growth and reproduction, which ultimately has great impacts on animal well-being and profitability. Modifications in the behavioral, psychological and biochemical thermoregulatory mechanisms are not sufficient to cope up with the heat stress. Hence implementing approaches like shelter management, nutritional strategies as well as improved health services and genetic improvement can have significant impact in ameliorating the heat stress effect on livestock sector.

Keywords: Heat stress, DMI, THI, Thermo-tolerance

 https://www.pashudhanpraharee.com/management-of-dairy-animals-during-heat-stress-practical-approaches/

Introduction:

Livestock is an important agricultural enterprise which is a major contributor to the global food security. Climate change emerged as one of the main threats to the livestock sector (Nardone et al 2010). The climate change induced heat stress has established as one of the crucial factors affecting livestock production. Farm animals are homeotherms as they can keep relatively constant body temperature within narrow limits despite wide variations in climatic environment. Deviation from the set level of body  temperature  under  stressful  hot  environment  leads  to  interference  with physiological  events  and  consequently  negative  impacts  on  animal  productivity.

The animals possess various adaptive mechanisms to cope with the changing climatic conditions (Alameen et al., 2012). The adaptive capability of the animals are determined by morphological, anatomical, physiological, biochemical and behavioural characteristics of these animals which helps them to survive in a specific environment (Das et al., 2016). Some of the physiological determinants of adaptations to heat stress are respiration rate (RR), rectal temperature (RT), pulse rate (PR), skin temperature (ST) and sweating rate (SR) (Indu et al ., 2015).
The assessment of thermal comfort or discomfort in dairy animals is widely investigated based on the THI (Hahn et al., 2003).

According to Reynolds et al (2010), rise in temperature may strongly affect the production, health, and reproductive performance of livestock. Heat stress also affects the metabolic and digestive functions due to altered or impaired feeding activity (Mader et al.,  2003). Heat stress slows down ruminal contractions, which in turns slow digestion. Heat stress may decrease milk production and quality, meat production, reproductive efficiency and animal health (Sejian et al., 2016).

There is a necessity to develop mitigation strategies that contain management measures, nutritional adaptations, health maintaining factors as well as animal breeding programs that include heat tolerance to deal with these challenges.

 

Strategies to alleviate summer stress

1. Provision of clean water

Increasing water availability to the animals is one of the most important strategy to alleviate heat stress. The consumption of water increases sharply as the environmental temperature increases because of greater water losses from rapid respiration and sweating.

2. Dietary management

Fermentation of feedstuffs in the rumen creates heat. This heat of fermentation is not beneficial in a hot season. Reduced DMI associated with heat is almost certainly the body’s mechanism of reducing heat of fermentation simply by reducing the amount of feed to be fermented in the rumen.

Various dietary approaches or feeding strategies have been used to alleviate the adverse effect of heat stress. They aim to maintain water balance, nutrients and electrolytes intake and/or to satisfy the special needs during heat stress such as vitamins and minerals.

The depressed feed intake in hot weather is commonly considered as an adaptation to reduce metabolic heat production. The most limiting nutrient for cattle during heat stress is usually energy intake. A common approach to minimize the reduction of energy and nutrient intake under heat stress is increase in energy density to reduce forage intake and also increase energy or protein concentrate in the ration to overcome the low DM intake.

1. Decrease Fiber level in the ration

Adequate fiber in the diet is essential to maintain rumen health, and high quality forage helps to maintain feed intake. The heat of fermentation of individual feedstuffs rises with its total fiber (i.e., NDF) content. Thus forages with the highest fiber quality (i.e., the fastest fermenting) should be fed as they have a lower heat of fermentation and higher energy value.

1. Addition of Fat in the ration

Fats are commonly used feed ingredient in rations and they are very high in energy. Increasing the amount of dietary fat has been widely accepted strategy in order to reduce basal metabolic heat production.

Increasing the energy content of the diet via lipid addition can partially overcome the effect of heat stress. Recently Melo et al. (2016) reported that supplementation of palm oil significantly reduced rectal temperature and respiratory rate, increased milk yield, reduced dry matter intake and increased feed efficiency in lactating cow. Wang et al. (2010) showed that feeding supplemental saturated fatty acids (SFA) during heat stress decreased the body temperature during the hottest time of the day and increased milk yield. Growth performance was improved in heat-stressed finishing pigs fed high-fat diets (Spencer et al., 2001).

1. Protein supplementation

As DMI is depressed due to heat stress, it is necessary to increase the protein level of the ration (West, 1999). The proportion of the dietary protein that must be provided as rumen un-degraded protein (bypass protien), slow-release nitrogen or bypass amino acids must be increased, since the net passage of microbial protein from the rumen declines with lower DMI.

1. Mineral and Vitamin supplementation

The mineral densities in the ration should be increased relative to the decline in DMI. Bovines utilize potassium as their primary osmotic regulator of water secretion from sweat glands. Kumar et al. (2010) reported that supplementation of electrolyte relieved oxidative stress and improved cell mediated immunity in heat stressed buffaloes. Cows sweats more during heat stress, the sodium (i.e., salt) level of the diet should be increased.

 

Selenium

Natural and synthetic anti-oxidants in the feed as well as optimal levels of minerals help to maintain efficient level of endogenous anti-oxidants in tissues. Selenium protects tissue against oxidative stress. Tatcher (2006) reported an increase in immune-competence at parturition, an improvement in uterine health and second pregnancy rate during summer months in cows fed selenium-yeast prior to calving.

Chromium

Increased glucose availability and utilization has significant benefits in livestock during heat stress. Chromium is an essential micronutrient that potentiates insulin action on glucose and protein metabolism (Mertz, 1993). Spears et al. (2012) reported that heifers supplemented with increasing amount of chromium had increased insulin sensitivity, suggesting that chromium play essential role in glucose metabolism in ruminants. Chromium supplementation also minimizes the negative effects of the stress response by consistently decreasing serum cortisol during stress.  Dietary inorganic chromium supplementation in summer exposed buffalo calves improved heat tolerance, immune status and potency of insulin hormone (Kumar et al., 2015)

Niacin

Feed additives (e.g. vitamins) were investigated for their effects to improve the animals’ ability coping with heat stress. The vitamin niacin is known for its effects on blood vessels (vasodilatation) to increase sweat gland activity in cattle (Gille et al., 2008) and lipid metabolism. Zimbelman et al. (2010) showed that cows fed rumen-protected niacin had lower rectal and vaginal temperatures under moderate heat load. Rungruang et al. (2014) observed that supplementation of encapsulated niacin did not improve thermo-tolerance of winter acclimated lactating dairy cows exposed to moderate heat stress.

1. Rumen Fermentation Modifier

Monensin (an ionophore) is well described rumen fermentation modifier that increases the production of propionate, which is predominate glucogenic precursor in ruminants and thus improve the glucose status of heat stressed cows (Baumgard et al., 2011). The use of live yeast culture (Sacchromyces cerevisiae), has been extensively used to enhance nutrient utilization in ruminant animals (Francia et al., 2008)

 

 

3. Housing Management

Managing a dairy herd around frequent and intensive heat periods is highly demanding and accompanied with growing challenges. Several options are available on the level of the husbandry and management system, including structural alterations, cooling techniques (fans, misters, sprinklers and cooled waterbeds), provision of adequate shade (Kendall et al., 2007), management of feeding times i.e. shifting to cooler periods in the evening, night and early morning (Legrand et al., 2009) to minimize heat stress in animals.

1. Shade

The provision of shade is one of the easiest heat abatement methods to implement. Shade is beneficial for cattle physiologically, behaviorally, and in terms of production (Widowski, 2001; Kendall et al., 2006). Shade protects against solar radiation but may not affect air temperature or humidity around cows, which may inhibit their natural ability to dissipate heat (Renaudeau et al., 2012). Natural shade from trees provides variable protection against solar radiation and wind speed.

1. Shelter

Shelter management is one of the key techniques for reducing the impact of heat stress in livestock (Sejian et al., 2012). A good shelter should protect the animals from extreme climatic condition without compromising the animal performance in terms of growth, health and reproduction.

1. Orientation

Shed with its long axis running East – West provides a cooler environment than one with a North-South orientation (Kelly et al., 1950). The shelter is shaded for a greater part of the day resulting into lower floor temperature. Thus this orientation favours heat loss from animal body to environment both by radiation and conduction.

1. Shelter design and height of shelter

Open type of sheds has advantage over closed type shed. Minimum roof height should be 10 feet to reduce heat load. A height less than 3.0 m interferes with proper ventilation resulting into reduced convective heat loss from animals.

 

 

1. Shape and Roof type

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.

1. Roof material

It may be Hay or Straw, Galvanized steel, Plywood and several types of plastics are the roofing material. Hay thatch is more suitable for hot dry climate than hot humid climate. Wood makes good shed material but in it cracks develops and it needs treatments frequently. Asbestos sheet are more effective as top layer in double roof shelter. The most effective in terms of reducing heat load is a reflective roof such as a white galvanized or aluminum roof (Blackshaw and Blackshaw, 1994).

1. Color of Roof and Wall

It should be white outside and coloured inside. Painting of side walls white from outside reduces the surface temperature of the walls inside by 12 to 22⁰C in comparison to unpainted walls at air temperature above 37⁰ C.

1. Cooling system

Along with providing the shade, use of water as a cooling agent was found to be an efficient method for reducing effect of heat stress on animals particularly under dry hot and lower humidity climates. Evaporative cooling in animals can be accomplished either by direct evaporation from the skin surface of the animal or by indirect evaporation by cooling the microenvironment of the animals with cooling pads and fans in an enclosed shed (Dunshea et al., 2013)

Water can be used for spraying the floor and roof of shelter periodically or continuously during peak hot hours which lower their temperature and consequently reduces the heat load. Grass screens on sides of shelter when with water considerably cool down the air passing through them. It requires proper cross ventilation. During summer, we can reduce heat load of animals artificially by spraying small quantity of water on their body at repeated interval of 15-30 minutes. Fans or blowers fitted in cow shed help in increasing rate of evaporation of water.

Several direct methods of cooling are available like misting, fogging and sprinkling systems (Sejian et al., 2012). Sprinkling does not attempt to cool air as it does in the case of fogging and misting but instead uses large water droplet size to wet the hair coat of the animal directly. However, sprinkling increases the efficacy of non-evaporative cooling mechanism by reducing the ambient air temperature in the vicinity of the animals (Kalyan et al., 2013).

4. Health Management

Maintaining animal health is an important aspect if one attempts to sustain livestock production during heat stress condition. Efforts are need to be taken to maintain normal animal health during stressful condition. Developing public awareness and other health education programmes to tackle different diseases that arise as a result of heat stress are the primary requirement to tackle health issues.

5. Genetic and Breeding Management

The genomic and proteomic studies play a vital role in understanding the mechanisms of thermoregulation and delineation of genes conferring superior thermo-tolerant capability in different livestock species (Collier et al., 2003). Advancement in breeding technologies can be effectively used to develop a livestock breed with high thermo-tolerance. Breeds that cope up well to environmental stress conditions without compromising its productive capabilities have to be identified and subjected for breeding programs to evolve a suitable breed for different agro-ecological zones. Genetic improvement is an evolutionary action for development of heat resistant breeds (Guis et al., 2012).

 

Conclusion

Due to increased average temperatures and humidity, severe heat stress in dairy animals is observed, which leads to loss in production and health problems. The interventions to combat heat stress in animals include changing the physical environment, nutritional interventions, animal health and genetically thermo-tolerant animals. Due to heat stress, intake of dry matter decreases but requirement of energy increases. The nutritional strategies like increasing water availability, energy and nutrient densities, providing specific supplementation to alleviate heat stress in diary animals. In managemental perspective, shed construction, cooling systems (Fans and mist) along with shades are involved In environmental modification.

 

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