Pollution is a horrible blow to the modern era. lt is disastrous for all the living creatures, as all the living organisms are directly or indirectly affected by it. Various factors are responsible for polluting earth’s atmosphere. There are several kinds of environmental pollution. But as all parts of the earth’s environment 

are closely related, one type of pollution that harms one part of the environment may also affect others. Major types of pollution are air pollution, water pollution and soil pollution. On one hand livestock also contributes to these type of environmental pollutions in one or other way but on the other hand they are also clearing environmental pollution. Here these two aspects are discuss separately.

 Livestock as a source of environmental pollution.

 Modern livestock production involves concentrating large population in relatively limited areas to economize feeding and handling. Unfortunately, the corresponding increase in animal and animal wastes has intensified the pollution problem from that of earlier less efficient production methods. Methane is one of the major gas that constitute between 15 and 20% of the gases associated with the “greenhouse effect”, causing global warming and prominent changes to the environment. Carbon dioxide release into the atmosphere, associated with the burning of fossil fuels, may exert an even greater threat to environmental stability. These changes are expected to cause significant disruption to the environment in all regions of the world. As a result existing pattern of crop production may be dramatically changed. The global warming can cause the sea level to rise and climatic zones shift. Consequences of these changes could include flooding of major coastal cities along with other problems like serious reduction in the productivity of some areas currently used for crop production.

 Livestock and in particular ruminants (Cattle, buffalo, sheep, and goats) are one of the major producer of methane. It is estimated that ruminants generate approximately 80 million tonnes of the gas per year,  which is equivalent to 18% of total world production of this damaging “greenhouse” gas. The rate of its production in the rumen  is most rapid immediately after a meal and in the cow may exceed 30 l/hour. The typical composition of rumen gas is carbon dioxide, 40 percent; methane, 30-40 percent; hydrogen, 5 percent; together with small and varying proportions of oxygen and nitrogen (from ingested air). Carbon dioxide is produced partly as a by-product of fermentation and partly by the reaction of organic acids with the bicarbonate present in the saliva. The basic reaction by which methane is formed is the reduction of carbon dioxide by hydrogen, some  of  which  may be derived from  formate. The major precursor of methane appears to be formic acid through carbon dioxide and water.

       Through methanogenesis about 4.5 g of methane is formed for every 100 g of carbohydrate digested, and the ruminant loses about 7% of its food energy as methane. This figure indicates that methane is not only causing environmental pollution but its production is also a loss of food energy.

       In order to reduce methane gas production it is of great importance to have a balanced rumen fermentation, which will not only improve the utilization efficiency of feeds but also ensure the maximum degradation of complex carbohydrates to volatile fatty acids by ensuring suitable circumstances for microbial fermentation. It may be achieved by supplementing NPN sources and the supply of bypass carbohydrates and proteins in the ration which will supply sugars and amino acids post ruminally and hence reduce the production of methane. Urea or alkali treatment of straws, use of urea molasses blocks and legume and other fodder trees (as protein sources) for livestock are also of great importance in this regard.

       Second major threat to environment comes from animal wastes, which are causing air as well as soil pollution. It is estimated that a 100 lb steer produces about 56 lb of manure and urine daily, an average beef cattle feed lot of 30,000 head capacity produces 850 tons of animal waste per day. The major air pollution aspect of concentrated animal wastes is odor production, however, particulate emission and possible pathogen proliferation are also of concern. Turkey production in ventilated units produced 40-50 ppm of NH₃ and 3500 ppm CO₂. The gaseous constituents associated with poultry droppings include NH_3, CO₂, CH₄, H₂S, mercaptans, diketone, volatile organic acids, indole, and skatole. Similarly methanediol, H₂S, dimethyl sulfide, diethyl sulfide, propyl acetate, ethylamine, and trimethylamine are some of the gases which are associated with cattle wastes.

       By utilizing gas chromatographic methods, it was found that dimethyl sulfide is associated with the most intense odor from dairy cattle production units. It was found that the concentration of ammonia and amines were 20-40 times higher in the air of a large dairy farms than in urban areas 7 mile upwind from the boundary of the dairy unit.

       Humic acid (in feed) can be used to reduce the odor of poultry excreta. Use of ventilated litter floor may reduce upto 80% in NH₃ production. Ammonia emission can probably be reduced by the use of nitrifying and denitrifying micro-organisms. The production of nitrogen gas from ammonia and uric acid by the microorganism “thiosphaera pantotropha” in the presence of oxygen provides a prominent biotechnological tool in reduction of ammonia production and emission from manure. Manure has been recycled into cattle feed as wastelage, i.e., mixing about 40% fresh manure with 60% hay, and by using it fresh as an economic incentive to clean cattle pens daily.

       Odor reduction can also be achieved through appropriate waste handling procedures. Thoroughly cleaning and washing enclosed feedlots daily can substantially reduce odor producing compounds in the air. Potassium per mangnate (KMnO₄₎ was found effective in reducing odors from cattle feedlot operations when a 1% solution was sprayed at the rate of 20 lb/acre three times a year. Other odor control technique includes catalytic and thermal incineration, adsorption with activated carbon, and the use of alkaline scrubbing solutions.

       In arid agricultural regions, windblown feedlot dust can contribute to atmospheric particulate levels. Approximately 8 tons of particulate matter per year per 1000 head could be expected from uncontrolled lots with less than 25,000 cattle. Methods for the control of feedlot dust emission include frequent watering, chemical stabilization, increasing cattle density in pens and removal of manure. As in the control of malodors, good housekeeping in a feedlot is an effective control of dust emissions.

       Thirdly, many of these animals particularly those extensively managed in developing countries of the world consume large quantities of plant material, but are inefficient (in terms of animal bio-energetics or energy input/output ratios) converters and produce very little animal products.  In this way they strip the ground cover from large areas, thereby reducing the capacity of rangeland to act as a sink for carbon dioxide. Overgrazing may also damage the soil and cause erosion in over-grazed areas. A carefully planned rotational grazing will be helpful in this regard. Here to protect the environment means that fossil fuel dependent inputs must be more rigorously controlled.

 Livestock Clearing Agent for Environmental Pollution

       On one hand it is considered as animals are one of the major source of environmental pollutiton by producing methane gas in large quantities. On the other hand animals are playing a great role in reducing environmental pollution as these (Buffaloes, cattle, goats, sheep, camels, poultry birds, and other animals) are the best users of agro-industrial by-products and wastes produced by agro-based industries in an effort to meet the increasing food demand of growing population. These industries are producing not only good quality food for human consumption but also producing great amount of agricultural wastes and by-products , which ultimately increase the environmental pollution.

      Animals are rendering useful service by converting feeds such as green fodder, dry forages, crop residues, damaged grains, fruit pulp and peelings, and vegetable/fruit market wastes into valuable foods like milk, meat, and eggs. These feeds which cannot be used for direct human consumption are thus gainfully utilized. Each animal assumes the role of an independent factory where raw material in the form of feed ingredients are converted into finished products for human use. Most of the animal  feeds, being inedible for humans, could not have been put to good use without the animals. Similarly, without livestock, it would  become a difficult task to eliminate these enormous agro-industrial by-products and wastes from the face of land by simply leaving them to rot in the open to become a source of environmental pollution.

       Non-conventional feed resources (estimated to be more than 60 million tonnes currently available in Pakistan), comming from agri based industries, represent a great amount of cheap nutrients that can be used as livestock feed by the application of modern scientific technologies and success in this direction might serve as a milestone in reducing and stabilizing cost of production of quality milk, meat, eggs and other products and also reducing the environmental pollution in the country. The other aspect of this is to prevent animals from competing with human for the same food resources like cereals and pulses etc., or requiring more land for fodder production.

      Industrial revolution that might be considered as the forerunner of “Green Revolution” , resulted in the production of large amounts of agricultural/industrial by-products as wastes. It was only possible through raising animals by utilization of these wastes to save the agricultural nations from the pollution and nuisance of these wastes.

      In our country agro-industries are producing huge quantities of by-products and wastes. These millions of tonnes of wastes and by-products like straws, wheat bran, wheat midlings, rice hulls, rice bran, etc, are blessings to the dairy, poultry and fish industry. Some of the rice husk is now being used through enzymatic process to convert it into an important and valuable feed ingredient. Similarly rice hulls is being used as litter material by poultry farmers thus cleaning the surroundings of the rice mills and ultimately reducing the pollution.

      Similarly by-products of sugar mills (sugarcane baggase, canesugar molasses, sugar beet pulp), corn and corn oil mills (corn bran, corn gluten meal, corn gluten feed, maize oil cake and corn oil), and coconut oil factories (copra meal, coconut oil cake, coconut meal), which used to be thrown into the rivers or dumped into the soil, there by polluting the environment. Today these wastes and by-products are being used in animal feed mills for the manufacture of balanced feed for livestock, poultry and fish (like molasses which has been used as a source of energy for the animals, as it is commonly used in compounding feed rations for livestock and poultry). Thus animals are directly helping to balance the environment.

      Slaughter house wastes (blood, meat scraps, bones) being left daily during the operation. The poultry birds are end user of such wastes and by-products as these by-products are now being converted into useful feed ingredients like blood meal, meat meal, bone meal. Poultry industry wastes are being recycled for poultry itself as offal meal/ feather meal and hatchery by-products meal. The droppings of poultry birds are being used in large animal rations and for fish as well.

      The feces of animals (livestock manure and poultry droppings) are the good source of nitrogen, minerals and other nutrients. It can be used as natural fertilizer, it will cut down the load on chemical fertilizer producing factroies, which are also polluting the environment through their exhausts.

      In the same way fish wastes, fruit peelings, brassica leaves and stems, vegetable and fruit market wastes, fruit processing plants wastes (peelings and pulp), are all can be used for feeding animals. Utilization of these by-products by commercial animal producers is clearing the premises of mills which otherwise would have become a source of pollution.

      In many cases, animals act as sowers of seeds of useful fodder trees, legumes and shrubs to far areas and disperse them widely for propagation. Thus they ultimately save the nature. Animals are also helpful in keeping the pasture and rangelands safe from the hazards by grazing overgrown plants.

 CONCLUSION

      Everyone wants to reduce environmental pollution these days. But the pollution problem is caused by things that benefit people. For example, the exhaust from automobiles causes a large percentage of air pollution. But at the same time they provide transportation for millions of people. Factories that discharge much of the material that pollutes air and water, provide jobs  for people. Too much fertilizer and pesticide can ruin soil, but fertilizers and pesticides are important aids to growing of crops. Actually Livestock and all other things that benefit peoples are not polluting the environment, we the human beings are the culprits who use pesticides, who provide access roads to remote areas, who allow the hunter to kill or livestock to graze. We are often classed as the “ Polluters” and not the “ Protectors “ of earth and earth life. According to psychologists our  desire for  convenience is another  cause  of  pollution.  Most synthetic materials that pollute the environment are produced” to save people, time work and money”.

         We as an environmental protectors can do many things to control the environmental pollution by livestock. If we put more emphasis towards production oriented programme instead of concentrating only on the treatment of animals in the national policy. If we only increase the productivity per unit animal then we will be in a position to reduce animal numbers, which ultimately leads to less methane production and less green fodder demand as compared to the existing situations in the country. Animal production man can play a vital role in improving the productivity per unit animal.