पशुओं में विभिन्न तनाव और उनकी शमन रणनीति
Stress is the necessary response of the living body to maintain homeostasis. The stress response is highly integrated. Livestock responds to various kinds of stress including production, parturition social, environmental stress, and nutritional stress, in a well-coordinated effort of the brain, and other body organs.
The stress response is classified into four types; under stress, eustress, overstressed & distressed. Under stress; when an animal feels boredom due to lack of an object of interest, eustress; makes animal produces extraordinary responses called as good stress, overstressed; when environmental condition is not that favourable and produces mild activation stress response, and distressed; when the major stress response is provoked.
While livestock raising farmer engaged in so many activities regularly that are not perceived as stressful by the farmer but have a large impact on production and shows poor animal welfare. Like Vaccination, transportation, and improper milking practices.
Livestock’ reared in a tropical environment like India has generally been subjected to multiple stresses at a single point in time. In the case of thermal stress aggravated when feed restriction is involved. Stressed animals need at least 30 min to calm down and have their heart rate return to normal.
On the other hand, calm animals are less stressed. Negative handling techniques are known to directly impact livestock production. Animals raised in a calm environment have better weight gain and better meat quality.
Symptom of stress in livestock:
- Respiratory issues could result from heat stress, cold stress or sickness.
- Rapid Heart Rate
- Standing hours increase/decrease.
- Frequent Urination
- Trembling
- Open-Mouthed Breathing
- Slobbering
- Lack of Coordination
- Restlessness
- Hurdling behaviour in cold stress
Various stress encountered by livestock
1. Heat stress
Heat stress can be defined as a group of conditions due to over-exertion in excess environmental temperature. The condition includes a beat cramp. Heat exhaustion, and heat stroke. It is now widely accepted that heat stress is the major cause of lower production and economic loss in sheep and goat, poultry, swine, beef cattle, and dairy cattle. The thermal comfort zone for most animals is between 4 and 25°C.
When the temperature exceeds 25°C, animals suffer heat stress in severe cases of heat stress, the deep body temperature (core temperature) rises, animal cells are affected, and production performance is reduced. The effect is more pronounced when the relative humidity is greater than 50%. Thresholds for animal heat stress are important for distinguishing between thermoneutral and thermally challenging environmental conditions.
It is a well-recognized biometeorological problem that heat stress has a negative impact on productive performance, poor immune status, and ultimately the survival of livestock. Accurate estimates of heat stress thresholds are useful for evaluating heat dissipation capabilities, growth rate, feed conversion efficiency, and for comparing management techniques for overcoming the adverse effects of heat stress.
Heat stress leads to a reduction in feed intake, and also includes altered endocrine status, reduction in rumination, and nutrient absorption. Heat stress is one of the major concerns in pork production during summer because pigs do not have functional sweat glands like other livestock species to assist them in efficiently removing body heat.
In thermal stress, increased respiration rate leads to increased losses of carbon dioxide from the lungs, resulting in the reduction of partial pressure of carbon dioxide, and consequently the concentration of bicarbonate in the blood. The ensuing lowered concentration of hydrogen ions causes a rise in plasma pH, a condition widely known as blood alkalosis.
2. Nutritional Stress
Nutrition plays an important role in the production performance of animals, inadequate nutrition results in lower growth rate, milk yield, meat production, and other performances. Nutritional factors such as excessive or insufficient nutrition adversely affect the entire body function. Grazing animals in arid and semi-arid regions are generally subjected to periods of undernutrition during extreme hot environments due to non-availability of feed and poor pasture conditions caused by lower availability of nutrients, which in turn results in low productivity.
The animals suffer severe nutritional stress in the dry season when the natural pasture is of low nutritional value and usually in scarce supply. During this time of the year, animals also waste a lot of energy, as they have to walk long distances in search of food and water.
As a result of these dry seasons and adverse conditions, animals lose weight, and body conditions and have low milk yields, low conception rates, and increased calf mortalities, all of which culminate into heavy economic losses to the smallholder farmers.
Sheep and goats due to their inherent grazing habit are often susceptible to nutritional stress. Extensive rearing of sheep and goats in most of the arid and see arid regions is characterized by grazing during day hours and housing of the animals during night time, with possible supplementation of concentrate mixtures and of straw or hay. If the nutritional stress occurs during the mating season, it can reduce sheep fertility.
In the areas where sheep and goat breeding are more diffused, late spring and summer are characterized not only by poor grass availability and palatability. Young animals are more sensitive to nutritional stress because their adaptive mechanisms are poorly developed.
Overfeeding and changing feeding patterns can cause stress and result in ulcers in pigs. Poor quality drinking water containing high levels of dissolved minerals, including sulfates, increases the incidence of diarrhoea and worsens post-weaning growth in piglets.
3. Walking Stress
Livestock in tropical regions are subjected to walking stress, wherein, these animals have to travel long distances in search of grazing pasture. Small ruminants like sheep and goats spend a sizeable amount of energy in walking activity, especially in hot summer. Domestic livestock commonly spends around 7-12 h/day in grazing, which includes time spent for searching as well as consuming forages.
As the grazing time increases, more energy is used for activity and less for production purposes, thus, the minimum time that results in adequate dry matter intake is considered optimum. The grazing time of livestock in pasture depends on the ease of ingesting, which varies with the accessibility of plant parts, availability of total forages, and quality of the consumed diet.
4. Transportation Stress
Transport-related stress occurs in food animals primarily in commercial agriculture and to a lesser extent in rural areas. Transportation stress can be severe or mild, depending on a number of different stressors. Lack of exercise, prolonged standing, and environmental temperature and humidity are the major stress factors in livestock transportation.
Animals may be transported for marketing, slaughter, restocking from drought areas to better grazing areas, or for ownership transfer. Animals are typically transported on foot, by road, rail, ship, and, in some cases, by air. The majority of livestock in developing countries is moved by trekking on the hoof for short distances and by road or rail when necessary.
The majority of livestock in developing countries, in general, are moved by trekking on the hoof for short distances and by road or rail, when transportation involves long distances. Transport of livestock is undoubtedly the most stressful and injurious stage in the chain of operations between farm and slaughterhouse and contributes significantly.
1. Strategies to minimize the heat stress
Housing management
Animal shelters can be made from straw or locally available materials such as paddy straw, maize straw, plant leaves, crop residue stalk of leguminous fodder. Tree planting around the shelter benefits not only the animals but also the humans and the environment.
The required shed height should be greater than 2.4 m in order to allow proper air movement. Covering the window with a gunny bag and splashing water on it will relieve the discomfort caused by summer heatstroke.
These cooling methods have a beneficial effect as well. Wetting the animal with a cooling pad will absorb the heat and evaporate, leaving the surface cooler. High pressure sprinkling is now used in large dairy farms.
Feeding practices
During the summer, feed intake decreased, resulting in lower productivity. As a result, feed formulation should be designed in such a way that it meets both the requirement and the physiological demand.
By Increasing nutrient density, i.e., concentrated feed or fat supplementation, and reducing the fibrous part because it generates more metabolic heat feeding practice should be done in the early morning and late evening. Supplementing with antioxidants such as Vit C, Vit E, selenium, and other minerals such as K, Mg, and Na will help you overcome summer stress.
2. Transportation Stress Management
Provision for animal care should be made both during the journey and at the destination, particularly for animals that are tired, old, young, pregnant, or nursing. Avoid excessive animal loading.
During the journey, the animal should be protected from the harsh environment, which includes heat, cold, and rain. The supply of feed water necessitates a longer journey. If you need to travel for an extended period of time. Supplementing with vitamins C and E can help relieve transportation stress in hot weather.
Conclusion
Stress is unavoidable in livestock rearing. It has a negative impact on production, resulting in massive economic losses for farmers. Along with production losses, animal welfare compromised as well, so having a basic understanding of stress will aid in developing various strategies that will be useful at the ground levels.
Authors
Dr. Neha Rajawat, Dr. Gururaj VK, Dr. Amit Kumar, Dr. Lata Kant, Dr. Rishi Nanda
Division of Physiology and Climatology,
ICAR-Indian Veterinary Research Institute, Izzatnagar-243122, India
Email: