EFFECT OF ENVIRONMENT ON GROWTH OF ANIMALS
ANJALI ARYA1*, SUBHASISH SAHU1 and RITU2
1Department of Livestock Production Management and 2Department of Animal Nutrition
Lala Lajpat Rai University of Veterinary and Animal Sciences, Hisar – 125004 (Haryana), India
*corresponding author: anjaliarya2609@gmail.com
Introduction
Any livestock enterprise depends heavily on the environment for profitability. Understanding how each environmental factor affects animal growth, welfare and reproduction is crucial. The livestock producer can mitigate the negative effects of the negative environmental factors on his livestock when he knows how each factor influences growth, welfare and reproduction. An increase in production can be achieved by applying the positive influence of any environmental factor. Mainly genetics and environment contribute to growth, as they do with any other trait. Genes determine the potential growth limit of each individual. Every cell contains genetic codes that control hormonal interaction and activity, and through them, growth and other functions are controlled. Genetic potential is influenced by the environment and its interactions with the genotype. The environment includes nutrition, climate, management and disease.
Importance of growth in animals
The key objective in animal production is to achieve maximum growth and productive output such as milk or wool, within the context of an efficient use of feed and other necessary resources and inputs. Animal growth, in simplest terms, can be defined as an increase in size. An increase in size, however, has many implications. Growth may be viewed much differently if one refers to growth of the whole animal or to growth of cells, tissues and organs or to growth before and after birth or before and after puberty. As an animal grows from conception to maturity, its body proportions and composition change because growth rates of the different organs and tissues of the body vary as the whole animal grows. The order of growth of the different tissues is similar for all species of farm animals and seems based on the relative importance of the functions of the body parts or tissues for survival of the animal.
Role of Nutrition on growth
Animals obtain their basic building blocks for growth from their environment through nutrition. During pregnancy, the foetus gets nutrients from the mother’s body reserve to some extent, so it takes precedence over the mother’s system. In the case of severly deficient maternal diet, animals are born with a low birth weight and vigour. Minerals and vitamins are essential to calf vitality. In the absence of these minerals and vitamins seriously lowers the vitality of the animal without substantially lowering its weight. Animal death is often associated with low vigour and vitality. Calves born with sub-normal birth weight can attain mature size if they are fed well after birth, regardless of their prenatal growth rate.
Furthermore, postnatal feeding has a significant impact on growth and attainment of mature size. Under-feeding has different effects on the size of the adult animal. It also depends on several factors like:
(i) The severity of the nutrient restriction,
(ii) The kind of restriction (energy, protein, vitamins or minerals),
(iii) Length of under-feeding, and
(iv) The age at which feed restriction occurred.
Role of climate on growth
The climatic conditions under which animals are reared may have marked influence on growth rate and even on body composition. The subject of heat regulation in farm animals has a wide economic significance. Sheep, cattle and pigs attempt to maintain their body temperature at a constant value which is optimum for biological activity. At both extremes of climatic conditions, growth and feed efficiency are adversely impacted. Under stressful hot conditions, feed intake is lowered in order to reduce heat production. Productivity and growth are affected by the climate in two ways: directly and indirectly. The direct action of climatic excesses on the animal’s physiology affects the nervous, endocrine, circulatory, respiratory, alimentary and other systems with adverse effect on feed intake, feed utilization and growth. Animals exposed to elevated temperatures lose weight, average daily gain (ADG), growth rate and body total solids, resulting in impaired reproduction. Crossbreds and buffaloes are most affected by diseases than indigenous livestock, according to NRCC (2007). Due to their greater sensitivity to temperature rise, crossbreds and buffaloes will suffer from growth problems, puberty delays, and maturity delays caused by global warming, if it rises by 2-6 °C. The high ambient air temperature and solar radiation cause steers to reduce daily dry matter intake, resulting in a decrease in average daily gain, carcass weight and fat thickness. However, disease incidence may increase. It is remarkable how heat stress affects feed intake even in buffaloes.
The indirect effects of climate is on the feed supply, nutritive value of feeds, incidence of parasitism and diseases.
Climate has four major physical components, namely, (i) ambient temperature (ii) humidity
(iii) solar radiation and (iv) wind velocity.
These factors operate directly up on the animals as well as indirectly by way of their effect on soil, vegetation, drinking water, vectors of diseases and other objects and materials in location where the animals stay.
It is but natural that the effect of various modifications of the microclimate around the animal vary significantly between situation to situation and animal to animal. But, in general, shade (protection from solar radiation), shelter (protection against rain, wind and snow), increased wind velocity, evaporative cooling etc. have been found to increase growth rate.
Role of management on growth
It is certain that various managemental factors like systems of housing, pen size and building design, feeding and watering systems, weaning and calf management, sanitation and disease control etc. have a definite effect on growth. Most of these effects have not been quantified so far. So it is mostly left to experience and managerial skill to chalk out an appropriate management plan for each situation. In groups, animals interact and develop relationships among themselves. Relationships are dominant subordinate to establish a socially dominant hierarchy. In cattle, dominance-related interactions cause stress, bruises and physical injuries. Since cattle feedlot systems may be restrictive to key resources such as self-grooming substrates, shade, feeding spaces and comfortable lying places. Competition for some of the abovementioned resources may produce disturbances and subsequent biological costs to the animals. Poor management aggravates some environmental factors such as, temperature, wind, light and humidity.
Role of disease on growth
Bovines in the growing stages are susceptible to many diseases which invariably produce a setback in growth. Depending on the severity of the disease or its duration, the effect on growth may be transient or of a more permanent nature. In the former case compensatory growth that follows after recovery will take care of the loss in growth during the course of disease. If the intensity of the disease had been severe, there is possibility of a more permanent stunting of growth. Similarly, in many chronic diseases of longer duration, the animal fails to grow satisfactorily and remains stunted. As a result, there should be a proper contingency plan for disease control in place and it should be in place at the national level with details of the management structure, disease control strategies, and operational procedures for disease control; animal welfare considerations should be addressed within these disease control contingency plans. The plans should also include a strategy to ensure that an adequate number of personnel competent in the humane killing of animals are available. Local level plans should be based on national plans and be informed by local knowledge. The operational activities should be led by an official veterinarian who has the authority to appoint the personnel in the specialist teams and ensure that they adhere to the required animal welfare and biosecurity standards. When appointing the personnel, he/she should ensure that the personnel involved have the required competencies.
Conclusions
Generally, animal growth and development are largely determined by two major factors. The first one is genetic factors, which include disease resistance, feed conversion efficiency, breed, and abnormal growth rate. Secondly, the environment consists of nutrition, climate, management and disease. In order to harness the resources of animals with optimum amount, it is necessary to provide favourable conditions, such as adequate photoperiods, thermoneutral conditions, access to adequate and quality food, a low stress environment, and control of diseases should be fulfilled.
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