Thursday, April 25, 2024
General Agriculture

Mechanism of Body Defence against Stress in Animal Production

Animals living in different ecologies of the world have for several decades and for every moment of the day developed means for coping with their environment as a matter of survival. Farm animals expectedly must go beyond survival to improve their productivity notwithstanding
the degree of stress to contend with.

Mechanism of Body Defence against Stress in Animal Production
Mechanism of Body Defence against Stress in Animal Production

Breeding or introduction of animal into an environment should recognise important adaptive traits and concepts that may help to achieve good performance. Consideration must be given to effects and adaptive mechanisms for different stress factor.

The concept of fitness of farm animal extends from ability to survive now and withstand environmental demands in future, to ability to produce sufficiently to justify cost of domestication. Homeostasis, physiological, biological and genetic adaptations are concepts in understanding the means by which animal cope with their environment.

The concept of energy balance forms the central pivot which tilts the environmental stress in different directions for animal to respond. Effective responses of animals to environmental stress often result in depressed productivity even in attempt to apply mechanisms to ward off
the pervading stress condition.

The responsibility of the producer is to understand these concepts in the management of the stock for survival and higher productivity by controlling the overbearing influence of the environment.

1) Mechanism of Body Defence against Cold

The animal body can defend itself against cold by three means namely: storing or conserving heat, through insulation and by increasing heat production or a combination of all. Increasing the body insulation against cold is more economical considering energy expenditure
involved.

Differences in species nurtured by adaptation have favoured economic ways of supporting higher body insulation to animals living in cold climates. The body insulation is in three classes:

1. Peripheral Tissue: This act by vasoconstriction of the coetaneous and sub-coetaneous to reduce the temperature gradient from the skin surface to the environment and also by the aid of subcutaneous fat.

2. Hair Coat Insulation: This depends entirely on trapped air which occupies over 95 per cent of volume of the air coat. The insulating capacity increases with thickness and air density of the
air coat. For example, temperature and arctic species of animals tend to develop thick air coat while most tropical animal have thin air coat.

There is also a non-linear fall of temperature along the hair coat, so that as the body size of animal decreases below certain level, the level of the hair coat decreases. However, wind and rain greatly reduce the efficiency of hair coat as insulating mechanism. But the impeding effect of wind diminishes with increasing hair coat density.

3. Insulation of the Air: This insulation is caused by the layer of air or boundary layer adhering to the surface of the hair coat in the hairy species and to surface of the body in non-hairy species. It varies from one specie to another and is almost independent of the body size. The insulating mechanisms of the boundary layer decreases with increasing air speed.

2) Mechanism of Body Defence against Heat

This can be effected by:

1. Behavioural means e.g. moving away from heat source, drinking more water, looking for shed or cold surface

2. Reduction in body insulation e.g.

(a) vasodilatation to the ears, legs and tongues as more blood flows there to dissipate heat by taking advantage of hairlessness of the body parts.

(b) Shedding of hair: If environmental temperature is equals to body temperature, vasodialation ceases to be very effective.

3. Increase in temperature loss: This occurs either from the skin or respiratory tract. The evaporation from skin is by sweating through sensible and insensible heat loss. Loss of heat energy from respiratory tract is by panting as often noted in chicken or dog.

4. By lower rate of heat production if exposed to heat stress. The appetite drops and animal consume less feed. It also reduces its motor and thyroid activities. The thyroid gland regulates basal metabolism for homeotherm.

5. Increase in the reflectance of hair coat to solar radiation. Animal with lighter hair coat reflect more heat than those with darker coat colour. The relative importance of cutaneous and respiratory evaporation varies from specie to another.

A sweating animal controls the amount of water while a panting animal controls the amount for larger proportion of total evaporation than European type of cattle. Also within a breed, heat tolerant animal have higher cutaneous and lower respiratory evaporation than heat intolerant counterpart.

Read Also: Effect of Stress on Animal Productivity

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Benadine Nonye is an agricultural consultant and a writer with over 12 years of professional experience in the agriculture industry. - National Diploma in Agricultural Technology - Bachelor's Degree in Agricultural Science - Master's Degree in Science Education - PhD Student in Agricultural Economics and Environmental Policy... Visit My Websites On: 1. Agric4Profits.com - Your Comprehensive Practical Agricultural Knowledge and Farmer’s Guide Website! 2. WealthinWastes.com - For Effective Environmental Management through Proper Waste Management and Recycling Practices! Join Me On: Twitter: @benadinenonye - Instagram: benadinenonye - LinkedIn: benadinenonye - YouTube: Agric4Profits TV and WealthInWastes TV - Pinterest: BenadineNonye4u - Facebook: BenadineNonye

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