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India has witnessed a phenomenal increase in food grains production since Independence, and achieved a record harvest of about 259 million tonnes in 2011-12. Similarly, there was an impressive record production of pulses : 18.1 and 17.2 million tonnes in 2010-11 and 2011-12,  respectively. However, to meet the increasing demand of the continuously rising population, about 2 to 3 million tonnes of pulses have to be imported every year costing the country about Rs.3000 crores in foreign exchange. Despite the changes in the dietary habits, pulses in India are still considered an important source of proteins, particularly, for the poor. However, the per capita availability of pulses has been declining over time decreasing from 60.7 gm/day in 1951 to about 32 gm/day in 2010 mainly due to stagnant production (except in recent years), rising demand for consumption and other uses. Further, pulses play an even greater role in maintaining and enhancing soil fertility through nitrogen (N₂) fixation.

Pulses, grown on marginal and poor soils under low input management with very low yields, are the integral part of dryland farming systems and cover 12.8% of the total cropped area in Andhra Pradesh. There are no pulse based cropping systems in the state and they are only component crops of cereals or commercial based cropping systems as intercrops or catch crops in between two main crops or as sequence crops after exhaustive cereal or commercial crops raised on residual fertility and receding soil moisture. The important pulse crops grown are Chickpea, Pigeonpea (Redgram), Mung bean (Greengram) and Urd bean (Blackgram) which contribute to 97.7% of total pulse production in the state. Pigeonpea is mostly grown as intercrop under rainfed conditions with crops like sorghum, maize, castor, cotton etc. It is also grown as sole crop and at times, pigeonpea is intercropped with greengram/ blackgram.

Assam is surrounded by Bhutan and Arunachal Pradesh on the North; Nagaland and Manipur on the East; Meghalaya and Mizoram on the South and Bangladesh, Tripura and West Bengal on the West. The total land area of Assam is 78,523 sq. km and it accounts for 2.4% of total geographical area of the country. Demographically, Assam is the most populous state in the North East India. Economically, out of eight North East states, Assam is the most developed one, but compared to other states like Maharastra, Tamilnadu, Gujrat, it lags far behind in almost all economic spheres.

Pulses are considered to be the most effective means of overcoming protein and micronutrient malnutrition since they are excellent sources of dietary protein (19-25%), besides being rich in important minerals and vitamins (Ali and Kumar, 2004). In Bihar, people are mostly vegetarian in dietary habits and depend largely on pulses as the source of dietary protein. But production of pulses has not kept pace with the population growth and per capita availability of pulses has thus, declined from 61 g/day in 1950-51 to less than 28.0 g/day in 2001 as against 70 g/day the standards prescribed by ICMR. Moreover, in Bihar the contribution of cereals in total protein consumption is more than 73.0% which is not a healthy trend as cereal proteins lack many essential amino acids that are present in the pulses from which only 10.6% of total protein intake come in the diet of rural population. This alarming situation, perhaps, has arisen largely due to the quest for food security rather than nutritional security, being the prime national agenda. According to an estimate, more than 70% of gross cropped area in the state is occupied by paddy and wheat whereas, only 9.0% of it is shared by the pulses.

Rice is the principal crop of the region and cultivated in 3.9 million hectares area with an average productivity of about 1.3 t ha-1, which is very low. Irrigation resources are limited and confined to only 26 per cent and utilized for rice crop only. The region has rice based cropping system, in which lathyrus (grasspea),  is grown as utera (relay crop) in 0.46 million hectares. However, its productivity is not more than 2 to 3 q ha-1. Pulse crops are cultivated in an area of 0.44 m ha in kharif and 0.81 m ha in rabi season. The main pulse crops of the region are lathyrus, black gram, pigeonpea, chickpea, horsegram (kulthi), lentil and field pea. Area-wise, urd in kharif and lathyrus in rabi occupy the top position but as far as productivity is concerned, pigeonpea and chickpea are important. Pigeonpea and chickpea together can contribute a lot in increasing the pulses production in region. The average productivity of pigeonpea is 5.19 q ha-1 . It is also grown on rice bunds, which may give an additional production of 0.06 mt. Mung and urd are grown throughout the year in the region, however, powdery mildew and yellow mosaic virus diseases pose severe threat to these crops.

Gujarat grows more than half a dozen pulse crops on  7.84 lakh hectares  area with an annual production  of 6.09 lakh tonnes and a productivity of 777 kg/ha. Amongst these, pigeonpea, chickpea, greengram, blackgram, cowpea, mothbean and clusterbean are the important pulse crops grown in the state. Mothbean, greengram and clusterbean are the predominant pulse crops grown in arid region of North Gujarat, though other pulses are also grown on a sizable area. Despite this distinction of being the largest producer, the availability of pulses is far from satisfactory which is evident from the fact that per capita availability has not kept pace with the population increase and has declined to merely 28 g/capita/day as against the mandated minimum and optimum quantity of 80 and 104 g/capita/day, respectively, as per WHO standards. As a result, with 11 per cent of the world’s import, it is also the largest importer of pulses.

Viable cropping systems involving new rewarding crops infuse new opportunities and challenges as well as demonstrate the potential for land productivity with higher growth and economic achievements.  As far as agricultural production is concerned Haryana is a surplus agricultural state and is one of the largest food supplier to the national kitty. The cropping patterns have undergone drastic changes over the years with a major shift in favour of cereals like paddy and wheat. Consequently, the existing cropping system viz. paddy-wheat, has started showing its adverse effect on soil health and consequent decline in crop productivity. Diversification of existing system by involving pulses, vegetable, fodder and other high value crops, is considered to be the potential alternative to address many present day problems. For example, under assured irrigation, pearlmillet-potato-moongbean gave almost 65% higher yield than the existing cotton-wheat cropping system because the leguminous crop in summer gave higher economic yield and benefit to pearlmillet crop. The package of practices with focus on pulses crops grown in Haryana state are discussed here.

Pulses occupy an important place in hill agriculture. They are complementary to cereals in production and consumption being an important source of protein and nitrogen fixing ability which helps in improving soil health. Thus, cultivation of pulses has a positive relationship with our environment, human health and food security. Pulses produced in the hills are famous for their cooking quality, taste and flavour.
 
Himachal Pradesh has emerged as a model hill state in which agriculture is a dominant economic activity and major source of employment and income to the rural people. Being a hilly state, agriculture is practiced on about 10% of the geographical area. Out of which nearly 80% is rainfed. During the last three decades, the farming scenario has changed significantly. The area under fruits, vegetables and cereals has increased tremendously at the cost of pulses and oilseeds. There is, therefore, an urgent need to reverse this trend as pulse cultivation will not only increase soil health but save precious foreign exchange.

The geographical area of the union territory of Andaman and Nicobar Islands is 8, 24,900 ha with 86.9 % of it under reserve and protected forests. The humid tropical climate that prevails in the Andaman and Nicobar islands provides a unique opportunity to grow various crops. Owing to a number of factors, hardly 4.8% of the area is under cultivation. Maximizing the productivity and farm income mainly depends on effective management of natural resources like rain, soil, land as well as labour present in the Island ecosystem.  On an average, the Islands receive 3074 mm of rainfall distributed over 8 months. The rainfall is intense from June to September and may have even up to 30 rainy days per month sometimes, however, from January to April, the rainfall is scanty or absent, particularly in March. The undulating terrain results in severe water crisis during the period which is aggravated by higher evapotranspiration. The Islands receive south-west monsoon from May to September and north-east monsoon during October to January. The topography of A&N Island is undulating with a stiff terrain exposed to soil erosion due to heavy rainfall.  The crop growing season can be divided in to two major seasons viz., wet 
and dry seasons.

Pulses are important crops in the State of Jammu and Kashmir as they are the only source of protein, an essential part of the vegetative diet. Besides that, pulses enrich the soil fertility by fixing atmospheric nitrogen in the root nodules and improve the soil structure (Thakur et al., 2009). The tap root system explores the deeper soil strata and heavy leaf litter increases the soil organic matter. Pulses in J& K state are ideal crops for mixed and inter-cropping as well as vegetable and fodder crops. It has been estimated that by 2020 the pulse requirement for Jammu region of J&K alone will be 1.51 lakh tonnes (based on average per capita consumption of 68 grams for the projected population of 60.75 lakh) whereas the estimated requirement of J&K state as a whole works out to be 3.85 lakh tonnes (Digest of Statistics 2008-09).

Jharkhand, a newly created (15 November, 2000) state having total geographical area 79.72 lakh hectares, net sown area 18.1 lakh hectares with cropping intensity 114%, is rich in natural resources such as minerals, coal, soil, water, forest cover (29.3%), biodiversity but deficient (50%) in food grain production because of meagre irrigation facilities (10% of cultivated area) in absence of perennial rivers. This state is primarily rainfed and crop production largely depends on monsoon. The south-west monsoon contributes nearly 85% of rain water. Accordingly, the success or failure of crop production is closely linked with the onset, progress and withdrawal of monsoon. Delay in onset, intermittent dry spell (1-3 weeks), early withdrawal of monsoon are also usually observed. Failure of rain has adverse impact on the reproductive phase of rainy season crops and thus on crop yield as well as establishment of winter season crops. Sometimes high rainfall (140 mm/day) coupled with light soil texture and undulating topo sequence provides congenial environment for soil erosion with runoff. This also offers opportunity for water harvesting. Infact, soil and water are the two basic natural resources which must be conserved and utilized efficiently on long term basis.

In Karnataka, pulses are being cultivated in an area of about 20 lakh ha (about 17% of cultivated area) and the important pulse crops of the state are pigeonpea, chickpea, greengram and blackgram (Table 1).  In addition, horsegram and field bean (Dalichos lab) need a special mention, as they occupy a unique position among pulse crops especially in Southern Karnataka. However, major pulses like pigeonpea chickpea, greengram and blackgram are confined to few districts in Northern Karnataka, although some area is distributed throughout the state. Compared to the average productivity of nation (560 kg/ ha), the Karnataka state productivity is low (505 kg/ha). In spite of the best efforts, the progress made in improving the overall production as well as productivity of these pulse crops is not significant as compared to the cereals.

The total area under pulses in Kerala during 2008-09 was 3943 ha with a production of 2982 tonnes. The average yield per hectare is 756 kg. Cowpea, greengram, black gram and red gram are the important pulse crops traditionally grown in Kerala. Nearly 75% of area under pulses cultivation is occupied by cowpea. The remaining 25 per cent of area under this group of crops in the State is shared mainly by greengram, black gram and red gram. Among these, red gram is mainly confined to the Palakkad district and the crop season extends over kharif and rabi together. The other pulses are cultivated in all the districts of the State. Bengal gram is totally imported and there is little scope for its development in Kerala.

Madhya Pradesh is a major pulse producing state of the country and more than half a dozen of pulses are grown on 48.99 lakh  ha area with an annual production of 41.73 lakh tonnes and average productivity of 852 kg/ha (Table 1).  The pulses production share of Madhya Pradesh is 28.6% to national pulses production. Amongst the pulses, chickpea, pigeonpea, moong, urad, lentil and field pea are the important crops of the state. These crops contribute about 3296 thousand tones to national pulse basket from an area of about 4318 thousand hectares (Table 2). Among the pulse crops grown in the state, chickpea accounts 76% in production from 60% area. Second important pulse is lentil (13%) followed by uradbean (12%), pigeonpea (8%), field pea (5%) and mungbean (2%) with percent share of 8, 5, 7, 3 and 1 in production, respectively. The area and consequent production of pulse crops in the state showed, in general, an increasing trend since 1981 till date (Table 2 and Fig.1). Linear increase in yield of these crops from 531 kg/ha to 764 kg/ha in this period is also witnessed as the impact of technological advancement in these crops in the recent past. Natural calamities mostly drought in few to most of the districts is the main reason of low productivity in triennium ended in 2004.

Maharashtra state is located in the north centre of Peninsular India. The topography of the state is the outcome of its geological structure. The state area, barring the extreme eastern Vidarbha region, parts of Kolhapur and Sindhudurg, is practically co-terminous with the Deccan Trap. The state enjoys a tropical monsoon climate; the hot scorching summer from March onwards yields to the rainy monsoon in early June. The rich green cover of the monsoon season persists during the mild winter that follows through an unpleasant October transition, but turns into a dusty, barren brown as the summer sets in again. The seasonal rains from the western sea-clouds are very heavy and the rainfall is over 400 cm on the Sahyadrian crests. The Konkan on the windward side is also endowed with heavy rainfall, declining northwards. East of the Sahyadri, the rainfall diminishes to a meagre 70 cm in the western plateau districts, with Solapur-Ahmednagar lying in the heart of the dry zone. The rains increase slightly, later in the season, eastwards in the Marathwada and Vidarbha regions.

Pulses occupy an area of 0.18 m ha with total production of 0.12 mt in NE Region. This region is one of the potential areas where pulse production can be increased horizontally by utilizing a part of 16.72 lac ha area under jhum cultivation (Bujarbaruah, 2004). Considering that pulses could be grown mixed with other crops and their feasibility for relay cropping; the area and production of pulses could be increased vertically. Intercropping system not only covers the risk but also give a bonus yield of pulse crop in addition to normal return of the main crop. Maximum area and production of 0.11 m ha and 0.60 mt which is 60.90 % and 51.28% of the total area and production of the region, respectively is contributed by Assam only. After Assam, Nagaland and Tripura are the major pulse growing states having 30 and 8 thousand hectares of area with 28 and 5 thousand tonnes of production, respectively. In Meghalaya, pulses are grown on 5 thousand ha area and 4 thousand tonnes of pulses were harvested. Other states of this region grow pulses in about 6-7 thousand hectares area and produce 3-6 thousand tonnes (Table 1). The productivity of pulses in all the states is 1000 kg/ha except Assam and Manipur where its productivity is only 500 kg/ha. The average pulse productivity of all the NE States (661 kg/ha) is higher than that of whole India (637 kg/ha)

Pulses are the second most important group of crops next to cereals in Orissa occupying about 22% of total cropped area as compared to 54% for cereals. The state grows ten pulse crops, namely, greengram, blackgram, pigeonpea, horsegram, lentil, gram, cowpea, Rajmash, Lathyrus and ricebean out of which the first four crops cover 88% of total pulses area and 85% of total pulses production.
 
During 2008-09, pulse crops in Orissa were grown in about 20 lakh ha having production of  9.94 lakh tonnes and average productivity of 497 kg/ha (Table 1).

Pulses play an important role in improving the soil health through biological nitrogen fixation. These crops also help to conserve natural resources and therefore help to conserve natural resources and sustain the agricultural productivity. With almost one-fourth population below the poverty line, the recent steep hike in prices has made the availability of pulses for this section of society even more difficult, thus, further jeopardizing both food and nutritional security.

The average productivity of pulses (Table 1) is only 460 kg/ha but it ranges from 199 kg/ha (Moth bean) to 1719 kg/ha (Field pea). Year to year fluctuation in productivity of different pulses was also observed. The highest productivity i.e. 1067 kg/ha was observed during the year 2006-07 & the lowest productivity i.e. 497 kg/ha was recorded during the year 2008-09. The trend of area under pulse crop during the last ten years has also shown a wide fluctuation. Year to year and crop to crop variations are most pronounced.  The crop wise major pulse growing districts in Rajasthan are as follows.

The average productivity of pulses (Table 1) is only 460 kg/ha but it ranges from 199 kg/ha (Moth bean) to 1719 kg/ha (Field pea). Year to year fluctuation in productivity of different pulses was also observed. The highest productivity i.e. 1067 kg/ha was observed during the year 2006-07 & the lowest productivity i.e. 497 kg/ha was recorded during the year 2008-09. The trend of area under pulse crop during the last ten years has also shown a wide fluctuation. Year to year and crop to crop variations are most pronounced.  The crop wise major pulse growing districts in Rajasthan are as follows.

Tamil Nadu state is situated at the south-eastern extremity of the Indian peninsula bounded on the north by Karnataka and Andhra Pradesh, in the east by Bay of Bengal, in the south by Indian Ocean and in the west by Kerala state.  The state has a coastal line of 922 km and a land boundary of 1200 km. Tamil Nadu lies between 8°5’ and 13° 35’N latitude and 76°15’ and 80°20’E longitude. The total geographical area of Tamil Nadu is 13.03 m ha.

Pulse crops provide nutritious food, feed and fodder and thrive well in fragile eco-systems where other crops often fail. They have the ability to trap atmospheric nitrogen in their root nodules in association with Rhizobium, bringing qualitative improvement in soil health i.e. physical, chemical and biological properties of the soil.  These virtues enable pulse crops to remain an integral part of subsistence farming system of semi-arid tropics as well as of Indo-gangatic plains. The role of pulses has also been recognized for sustaining soil productivity under intensive cropping systems in irrigated conditions.

Pulses are an essential source of protein in the diet of the vegetarian population. Cultivation of pulses has been a long-standing tradition in Uttarakhand, where the availability of alternative sources of protein such as meat and milk is barely sufficient to fulfill the daily dietary requirements. Pulses assume big importance in these rainfed and environmentally harsh regions by being an ideal crop for the prevalent low-input agricultural conditions. In Uttarakhand, pulses not only form the major constituents of the staple diet but also serve as an important source of feed and fodder for the livestock. Pulses also improve the soil health by fixing atmospheric nitrogen as well as by increasing soil organic matter

Pulses are recognized as an integral part of Bengali as well as Indian diet and the ideal supplement of cereals by virtue of their high protein and essential amino acid content.  Pulses are inseparable ingredients of vegetarian diet and one of the cheapest sources of dietary nutrition protein in the state. The present emphasis on soil health, environmental quality and economic consideration, has stimulated a paradigm shift in cropping patterns leading to pulse based cropping systems. Any cropping system can become compatible and complete only when a pulse crop is included in it. Pulses won a strategic position in intensive as well as subsistence agriculture, as they are excellent source of dietary protein for millions of people, nutritional feed for livestock and having profound ameliorative effect on soil.

Definitions

        Toxicology: Knowledge (or science) of poisons, including their chemical properties, identification, biological effects, and the treatment of conditions they cause.

        Poison: Any solid, liquid, or gas that, when introduced into or applied to the body, can interfere with the life processes of cells of the organism - by its own inherent chemical properties - without acting mechanically and regardless of temperature.

Arsenic
General Information
    1.    Exists in elemental form (-3), trivalent As⁺³ and pentavalent As⁺⁵ oxidation states
    2.    Arsenic is an essential element for rats, chicks, mini-pigs and goats
    3.    The second most important pollutant for livestock. 

Source
    1.    Inorganic form is used in paints.
    2.    Pasture near smelters may be contaminated. 
    3.    Industrial effluents released into nearby water body
    4.    Insecticides (Arsenic trioxide, lead arsenate).
    5.    Herbicides (Sodium arsenite, lead arsenate)

Nitrate - Nitrite Poisoning
Sources
Accidental ingestion/grazing of Plants which are Nitrate accumulators 

Introduction

Plants are the main source of nutrition to farm animals for their maintenance and production. But, under certain conditions, plants intoxicate farm animal life due to the presence of some deleterious substances called phytotoxins. Such plants include a variety of fodder plants (Jowar, wheat straw, Lucerne), grasses (Millet grass), ornamental or fencing plants (Crotons, Nerium sps) and weeds (Tribulis) in the farm premises.

Introduction

The word mycotoxin is derived from myco, meaning mold and toxin, a poison. A great number of mold metabolites have been identified as mycotoxins. Thus mycotoxins are secondary fungal metabolites (i.e., metabolites not essential to the normal growth and reproduction of the fungus) which cause pathologic, physiologic, and/or biochemical lesions in other species (may include animals, plants, other microbes, etc.).

Introduction

In the thirst of modernization and industrialization man has contributed pollution to the life and ecology of plants, animals and microbes. Increased demand for food and fiber has lead to the chemicalization of agriculture and we have reached on such a stage that modern agriculture is dependent on high yielding varieties, which can only be grown under the influence of fertilizers and pesticides. Pesticides are the man made chemicals which are being used to produce enough cheap food. In India, 90,000 MT of technical grade pesticides are used annually to control pests and plant diseases. The pesticides are classified as insecticides, fungicides, weedicides, herbicides, nematodicides and rodenticides; of which insecticides constitutes 77% of the total pesticides used in different agricultural and animal husbandry practices and in public health operations.

Introduction

A toxin (Greek: ôïîéêüí, toxikon, lit. (poison) for use on arrows) is a poisonous substance produced by living cells or organisms that is active at very low concentrations. Toxins can be small molecules, peptides, or proteins and are capable of causing disease on contact or absorption with body tissues by interacting with biological macromolecules such as enzymes or cellular receptors. Toxins vary greatly in their severity, ranging from usually minor and acute (as in a bee sting) to almost immediately deadly (as in botulinum toxin)

Introduction
The major conditions described under this heading are as follows :
    1.    Snakebite 
    2.    Scorpion bite 
    3.    Black widow spider sting 
    4.    Toad poisoning

Snake Bite
Poisonous snakes mainly belong to three categories

Introduction

Chemical warfare involves using the toxic properties of chemical substances to kill, injure or incapacitate an enemy.

Chemical warfare is different from the use of conventional weapons or nuclear weapons because the destructive effects of chemical weapons are not primarily due to any explosive force. The offensive use of living organisms (such as anthrax) is considered to be biological warfare rather than chemical warfare; the use of nonliving toxic products produced by living organisms (e.g., toxins such as botulinum toxin, ricin, or saxitoxin) is considered chemical warfare under the provisions of the Chemical Weapons Convention. Under this Convention, any toxic chemical, regardless of its origin, is considered as a chemical weapon unless it is used for purposes that are not prohibited (an important legal definition, known as the General Purpose Criterion)

Definition
 
Radiation poisoning, also called “radiation sickness” or a “creeping dose” is a form of damage to organ tissue due to excessive exposure to radiation. The term is generally used to refer to acute problems caused by a large dosage of radiation in a short period, though this also has occurred with long term exposure to low level radiation. Many of the symptoms of radiation poisoning occur as ionizing radiation interferes with cell division.
 
The clinical name for “radiation sickness” is acute radiation syndrome. A short exposure can result in acute radiation syndrome; chronic radiation syndrome requires a prolonged high level of exposure. A chronic radiation syndrome does exist but is very uncommon;

Introduction

Pollution is the introduction of contaminants into an environment that causes instability, disorder, harm or discomfort to the physical systems or living organisms they are in.
 
Pollution can take the form of chemical substances, or energy, such as noise, heat, or light energy.
 
Pollutants, the elements of pollution, can be foreign substances or energies, or naturally occurring; when naturally occurring, they are considered contaminants when they exceed natural levels. Sometimes the term pollution is extended to include any substance when it occurs at such unnaturally high concentration within a system that it endangers the stability of that system. For example, water is innocuous and essential for life, and yet at very high concentration, it could be considered a pollutant.

    ·    Radiology (Roentgenology): the science, which deals with diagnostic (radio-diagnosis) and therapeutic applications (radiotherapy) of radiant energy particularly of X-rays.

    ·    Veterinary radiology: the science, which deals with the uses of radiant energy for diagnostic (radio-diagnosis) and therapeutic applications (radiotherapy) in domestic, zoo, laboratory, exotic animals and birds.

    ·    Veterinary radiologist: a qualified person in radio-diagnosis and radiotherapy.

    ·    Radiography: is the making of film records (radiographs) of internal structures of the body by passing X-rays through the body to act on specially sensitized film.

Within a few weeks after November 8, 1895, Wilhelm Conrad Roentgen made the discovery of X-rays, they were being used in medicine and many sophisticated medical applications. This single discovery of X-rays revolutionized the entire medical field and developed into a separate discipline in the diagnostic and therapeutic applications in human beings and animals. On 10 December, 1901, Roentgen received the first Nobel Prize for Physics in recognition for discovery of X-rays. Radiography in veterinary practice may not always be used to arrive at a final diagnosis of the disorders. In the last few years, various types of X-ray scanners have been developed that allow highly detailed views of a particular section of the body. One type, known as a computerized tomography (CT) scanner, sends narrow beams of X- rays at various angles through a patient’s body. The information obtained from the X-rays is processed by a computer to produce an image of a cross-section of the body. The image shows much more detail than an ordinary X-ray picture. A section of the body can be studied in three dimensions by producing a series of adjacent cross-sectional images. Nevertheless, radiography remains a valuable modality in diagnostic purposes and has significantly extended the usefulness in medicine and research.

Radiographic positioning refers to placement of the body in respect to linear alignment of X-ray tube and film. Correct positioning is a most important prerequisite to obtain a diagnostic radiograph. Misinterpretations can result from inaccurate positioning.  Label the film before exposure with anatomical lead markers/ X-rite tape. The anatomical markers should be placed in close proximity to the area of interest without overlying important structures. At least two exposures of the part at 900 to each other should be taken to get complete anatomical information of the part.

Structure of matter: every structure is made up of elements. Elements can join together to make compounds. The smallest particle of a compound is a molecule. The periodic table gives details of all elements.

Nucleus: the center of atom containing protons and neutrons and hence almost whole mass of the atom. 

Atom: the smallest units of matter composed of electrons are negatively charged, protons have a positive charged and neutrons are neutral. If there are more electrons atom will be negatively charged, if there are more protons it will be positively charged. The total charge of electrons is equal to protons and hence the atom is electrically neutral.

To understand how radiographs are produced by using X-rays, an understanding of how photons of diagnostic range can interact with matter is necessary in five possible mechanism of interaction:
    ·    Coherent scattering.
    ·    Photoelectric absorption.
    ·    Compton scattering.
    ·    Pair production.
    ·    Photodisintegration.

    ·    An X-ray tube is an energy converter. It receives electrical energy and converts it into two other forms: X-radiation and heat.

    ·    It is a source of X-rays used in diagnostic radiology.

    ·    Designed and constructed to maximize X-ray production and to dissipate heat as rapidly as possible.

    ·    It is a thermo ionic diode type electronic vacuum tube where X-rays are produced.
 
    ·    A basic element of an X-ray tube (Figure) consists of the cathode, anode, glass tube and tube housing.

A tube rating chart is a guide regarding operational limits of the X-ray tube for single and multiple exposures and permissible heat load of the anode and the tube housing. It is an essential component for obtaining diagnostic X-ray examinations is a consistent way.
 
The tube rating chart provides important information on the maximum safe exposure time that can be used with specific mA and kV setting. If lower than designated exposure times are used, tube damage may occur. The size of the anode focal spot determines the rating of the tube because size controls the amount of energy it can absorbs and convert into X-rays and heat. Therefore, one should never use an X-ray chart formulated for another X-ray machine (even those made by the same manufacture) without making appropriate changes. Knowledge of three charts is important to extend tube life and includes tube rating chart, anode heat cooling chart and housing cooling chart.

X-ray photons are produced as a result of electrons hitting metal while extremely rapidly moving at high speed. This is achieved through the application of an electric current to a cathode (negative electrode) via a high voltage power source (electricity) which enables electrons to be released from the cathode into the X-ray tube. These electrons, being negatively charged, are attracted to the anode (positive electrode or target). When the electrons strike the metallic target (anode) in the tube, X-rays and heat are produced. Basically the process of producing an X-ray involves a source that produces X-rays and radiating them through a body or object, where they are absorbed at different rates until they are detected by a sensitive film or cassette. It should be mentioned at this point that most of the energy of the electrons is not converted into X-rays but is dissipated as heat. In fact 99% of the energy dissipated in the target is lost as heat, and only 1% is converted to X-ray energy.

X-ray Machines
 
There are many factors to consider when choosing X-ray equipment. The need of an individual practice varies depending on the species majority and case work load.
Types of X-ray machines: 
X-ray machines can be grouped into 3 categories:

I. Portable X-ray Machine

    ·    Is one that can be carried to the animal.
    ·    Portable X-ray machines are widely used in veterinary practice.
    ·    The maximum output is 15 to 35 mAs and kV ranges from 70-110 kVp.
    ·    Cost is less and easy to move around and transport. 
    ·    Suitable for X-raying of thin and small parts (limbs below stifle and elbow of large animals and can be used taking 
X-rays of abdomen an skeletal systems of small animals).

    1.    X-ray beam collimators: Comprised of 2 independently-acting sets of adjustable lead shutters. These are the devices made of lead and are used to restrict X-ray beam up to a desire area. In diagnostic radiology they are essential for safety of the patients, and persons and also to prevent fogging of films due to unnecessary radiations. The collimator is the most effective of beam limiting devices.

To set up of an X–ray (radiology) section following points should be considered while planning:
 
    1.    Anticipated present work load (number of cases and species of animals to be X-rayed) and future requirement in the next 10-15 years.
    2.    Financial resources available.
    3.    Type of equipment to be installed for radiographic work.
    4.    Requirement of radiation safety enforcing agencies e.g. of Bhaba Atomic Research Centre, Mumbai.
The overall set up of radiology section should consider the following requirements:

Handling

X-ray film is delicate and should not be handled carelessly or roughly. Avoid touching its surfaces, holding it as near the edges as possible with clean, dry hands. It is sensitive to maltreatment of any kind; heat and light adversely affect the emulsion. It can be handled safely and rapidly for all radiographic purposes as long as the X-ray specialist uses precaution to avoid the production of foreign marks (artifacts) on the film. 

The radiographic appearance of various tissues is influenced by a number of factors which determine the character of X-rays.  Various exposure factors control the radiographic dentsity, detail and contrast: milliamperage (mA), time (sec), kilovoltage (kV), focal spot/film distance (FFD) and object-film distance (OFD), thickness and nature of the part radiogaphed, speed and type of film and intensifying screens, temperature and time of developing, grid type, incoming line voltage, make and type of X-ray machine. Of these, first five exposure factors (milliamperage (mA), time (sec), kilovoltage (kV), focal spot/film distance (FFD) and object-film distance (OFD) are very important as radiographic technique chart may be worked out by varying one or more of the five factors.  These exposure factors are integral to image quality and should, therefore, to be adjusted appropriately in order to achieve a diagnostic radiograph of optimal quality (image contrast, brightness and clarity).

A diagnostic radiograph is defined as one showing the tissues adequately penetrated, sharply outlined, and the variations in tissue opacity sufficiently demonstrated. An ideal diagnostic radiograph should have excellent detail, correct density and proper scale of contrast. The sharpness of the image determines the detail or definition of an image. There are two factors in radiographic quality control, viz: photographic and the geometric effect.  Density, contrast and detail are photographic aspects of radiographic quality. Detail and distortion are geometric aspects of radiographic quality. Because a radiograph is a two-dimensional (2-D) image of a three-dimensional (3-D) object, the appearance of a radiographic image varies with the patient’s orientation in relation to the primary X-ray beam. 

One of the most important pieces of information in the field of  X-rays is a radiographic technique chart. If one select exposure factors from a good rating chart, consistent radiographic examinations of diagnostic quality will be obtained. In addition, there will be a saving of X-ray films because waste from repeated exposures will be avoided.

There are several types of techniques chart that can be formulated, each type must be formulated with the goat of maximum potential of a particular X-ray machine. Perhaps the most popular type of technique chart used by veterinarians is a variable kilovoltage technique chart. A variable mA second chart is probably more appropriate for the most powerful X-ray machine. However, combination of variable kilovoltage and mAs technique chart is best. Such charts take into consideration the need to adopt a technique chart for different body systems, such as a thoracic and abdominal study, as well as examination involving the musculoskeletal system. The principle of how to prepare a variable kilovoltage technique chart along with an example of such a chart is given.