Monday, 28 March 2011 19:24

Cattle, sheep and goats

Rate this item
(4 votes)

Material on hair-cutting and shearing was written with the assistance of J.F. Copplestone’s article on the subject in the 3rd edition of this Encyclopaedia.

Several animals convert high-fibre feeds, called roughage (over 18% fibre), into edible food that is consumed by humans. This ability comes from their four-stomach digestion system, which includes their largest stomach, the rumen (for which they gain the designation ruminants) (Gillespie 1997). Table 1 shows the various types of ruminant livestock that have been domesticated and their uses.

Table 1. Types of ruminants domesticated as livestock

Ruminant type



Meat, milk, draught


Meat, wool


Meat, milk, mohair

Camelids (llama, alpaca, dromedary and bactrian camels)

Meat, milk, hair, draught

Buffalo (water buffalo)

Meat, draught




Meat, milk, wool


Meat, milk, draught


Production Processes

Processes for rearing ruminants vary from intensive, high-production operations such as raising beef cattle on large, 2,000-km2 ranches in Texas to communal grazing such as the nomadic herders of Kenya and the United Republic of Tanzania. Some farmers use their cattle as oxen for traction power in farm tasks such as ploughing. In humid areas, water buffalo serve the same purpose (Ker 1995). The trend is toward high-production, intensive systems (Gillespie 1997).

High-volume, intensive beef production depends on various interdependent operations. One is the cow-calf system, which involves keeping a herd of cows. The cows are bred by bulls or artificial insemination annually to produce calves, and, after weaning, the calves are sold to cattle feeders to raise for slaughter. Male calves are castrated for the slaughter market; a castrated calf is called a steer. Pure-bred breeders maintain the herds of breeding stock, including bulls, which are very dangerous animals.

Sheep are produced in either range or farm flocks. In range production, flocks of 1,000 to 1,500 ewes are common. In farm flocks, production is usually small and typically a secondary enterprise. Sheep are raised for their wool or as feeder lambs for the slaughter market. Lambs are docked, and most male lambs are castrated. Some enterprises specialize in raising rams for pure-bred breeding.

Goats are raised through either range or small-farm production for their mohair, milk and meat. Pure-bred breeders are small operations that raise rams for breeding does. Specific breeds exist for each of these products. The goats are dehorned, and most males are castrated. Goats browse on shoots, twigs and leaves of brush plants, and thus they may also be used to control brush on a ranch or farm.

Other major processes involved in rearing cattle, sheep and goats include feeding, disease and parasite control, hair clipping and fleece shearing. The milking process and livestock waste disposal are addressed in other articles in this chapter.

Cattle, sheep and goats are fed in several ways, including grazing or feeding hay and silage. Grazing is the least expensive way to deliver forage to animals. Animals typically graze on pastures, wild lands or crop residues, such as corn stalks, which remain in the field after crop harvests. Hay is harvested from the field and typically stored loose or in stacked bales. The feeding operation includes moving the hay from the stack to the open field or into mangers to feed the animals. Some crops such as corn are harvested and converted into silage. Silage is typically moved mechanically into mangers for feeding.

The control of diseases and parasites in cattle, sheep and goats is an integral part of the livestock-rearing process and requires animal contact. Routine visits to the herd by a veterinarian are an important part of this process, as is observing vital signs. Timely vaccination against diseases and quarantining diseased animals are also important.

External parasites include flies, lice, mange, mites and ticks. Chemicals are one control against these parasites. Pesticides are applied by spraying or through insecticide-impregnated ear tags. The heel fly lays eggs on the hair of cattle, and its larva, the cattle grub, burrows into the skin. A control for this grub is systemic pesticides (spread throughout the body through spray, dips or as a feed additive). Internal parasites, including roundworms or flatworms, are controlled with drugs, antibiotics or drenches (oral administration of a liquid medication). Sanitation is also a strategy for the control of infectious diseases and parasite infestations (Gillespie 1997).

The removal of hair from live animals helps to maintain their cleanliness or comfort and to prepare them for exhibitions. Hair may be sheared from live animals as a product, such as the fleece from sheep or mohair from goats. The sheep shearer catches the animal in a pen and drags it to a stand where it is laid on its back for the shearing operation. It is pinned by the shearer’s legs. Hair cutters and sheep shearers use a hand-operated scissors or motorized shears to clip the hair. The motorized shears are typically powered by electricity. Prior to shearing and also as part of gestation management, sheep are tagged and crutched (i.e., hair encrusted with faeces is removed). The cut fleece is manually trimmed according to the quality and staple of the hair. It is then compressed into packs for transportation using a hand-operated screw or hydraulic ram.

Facilities used for raising cattle, sheep and goats are generally considered to be either confined or unconfined. Confined facilities include confinement houses, feedlots, barns, corrals (holding, sorting and crowding pens), fences and working and loading chutes. Unconfined facilities refer to pasture or range operations. Feeding facilities include storage facilities (vertical and horizontal silos), feed grinding and mixing equipment, haystacks, conveying equipment (including augers and elevators), feed bunks, water fountains and mineral and salt feeders. In addition, sun protection may be provided by sheds, trees or overhead lattice work. Other facilities include back rubbers for parasite control, creep-feeders (allows feeder calves or lambs to feed without adults feeding), self-feeders, calf shelters, cattle-guard gates and cattle treatment stalls. Fencing may be used around pastures, and these include barbed wire and electric fences. Woven wire may be required to contain goats. Free-ranging animals would require herding to control their movement; goats may be tethered, but require shade. Dipping tanks are used for parasite control in large sheep flocks (Gillespie 1997).


Table 2 shows several other processes of cattle, sheep and goat handling, with associated hazardous exposures. In a survey of farm workers in the United States (Meyers 1997), handling livestock represented 26% of lost-time injuries. This percentage was higher than any other farm activity, as shown in figure 1. These figures would be expected to be representative of the injury rate in other industrialized countries. In countries where draught animals are common, injury rates would be expected to be higher. Injuries from cattle usually occur in farm buildings or in the vicinity of buildings. Cattle inflict injuries when they kick or step on people or crush them against a hard surface such as the side of a pen. People may also be injured by falling when working with cattle, sheep and goats. Bulls inflict the most serious injuries. Most of the people injured are family members rather than hired workers. Fatigue can reduce judgement, and thus increase the chance of injury (Fretz 1989).

Table 2. Livestock rearing processes and potential hazards


Potential hazardous exposures

Breeding, artificial inseminating

Violent acts by bulls, rams or bucks; slips and falls;
zoonoses; organic dust and dander


Organic dust; silo gas; machines; lifting; electricity

Calving, lambing, kidding

Lifting and pulling; animal behaviour

Castrating, docking

Animal behaviour; lifting; cuts from knives


Animal behaviour; cuts from trimmers; caustic
salves; burns from electric irons

Branding and marking

Burns; animal behaviour


Animal behaviour; needle sticks

Spraying and dusting/drenching, worming


Foot/hoof trimming

Animal behaviour; awkward postures; tool-related
cuts and pinches

Shearing, tagging and crutching, washing and clipping

Awkward postures and lifting; animal behaviour;
hand-shearer cuts; electricity

Loading and unloading

Animal behaviour

Manure handling

Manure gases; slips and falls; lifting; machines

Sources: Deere & Co. 1994; Fretz 1989; Gillespie 1997; NIOSH 1994.


 Figure 1. Estimates of lost-time injury frequency by farm activity in the United States, 1993


Livestock exhibit behaviours that can lead to injuries of workers. The herding instinct is strong among animals such as cattle or sheep, and imposed limits such as isolation or overcrowding can lead to unusual behavioural patterns. Reflexive response is a common defensive behaviour among animals, and it can be predicted. Territorialism is another behaviour that is predictable. A reflexive escape struggle is apparent when an animal is removed from its normal quarters and placed in a confined environment. Animals that are restrained by chutes for loading for transportation will exhibit agitated reflex response behaviour.

Dangerous environments are numerous in cattle, sheep and goat production facilities. These include slippery floors, manure pits, corrals, dusty feed areas, silos, mechanized feeding equipment and animal confinement buildings. Confinement buildings may have manure storage pits, which can emit lethal gases (Gillespie 1997).


Heat exhaustion and stroke are potential hazards. Heavy physical labour, stress and strain, heat, high humidity and dehydration from lack of drinking water all contribute to these hazards.

Livestock handlers are at risk for developing respiratory illness from exposure to inhaled dusts. A common illness is organic dust toxic syndrome. This syndrome may follow exposures to heavy concentrations of organic dusts contaminated with micro-organisms. About 30 to 40% of workers who are exposed to organic dusts will develop this syndrome, which includes the conditions shown in table 3; this table also shows other respiratory conditions (NIOSH 1994).

Table 3. Respiratory illnesses from exposures on livestock farms

Organic dust toxic syndrome conditions

Precipitin-negative farmer’s lung disease

Pulmonary mycotoxicosis

Silo unloader’s syndrome

Grain fever in grain elevator workers

Other important respiratory illnesses

“Silo fillers’ disease” (acute toxic inflammation of the lung)

“Farmer’s lung disease” (hypersensitivity pneumonitis)


Asphyxiation (suffocation)

Toxic gas inhalation (for example, manure pits)


Hair cutters and sheep shearers face several hazards. Cuts and abrasions may result during the shearing operation. Animal hoofs and horns also present potential hazards. Slips and falls are an ever-present hazard while handling the animals. Power for the shears is sometimes transferred by belts, and guards must be maintained. Electrical hazards are also present. Shearers also face postural hazards, particularly to the back, as a result of catching and tipping the sheep. Constraining the animal between the shearer’s legs tends to strain the back, and torsional movements are common while shearing. Manual shearing usually results in tenosynovitis.

The control of insects on cattle, sheep and goats with pesticide spray or powder can expose workers to the pesticide. Sheep dips submerge the animal in a pesticide bath, and handling the animal or contact with the bath solution or contaminated wool can also expose workers to the pesticide (Gillespie 1997).

Common zoonoses include rabies, brucellosis, bovine tuberculosis, trichinosis, salmonella, leptospirosis, ringworm, tapeworm, orf virus disease, Q fever and spotted fever. Diseases that may be contracted while working with hair and fleece include tetanus, salmonellosis from tagging and crutching, leptospirosis, anthrax and parasitic diseases.

Animal faeces and urine also provide a mechanism for infection of workers. Cattle are a reservoir for cryptosporidosis, a disease that can be transmitted from cattle to humans through the faecal-oral route. Calves with diarrhoea (scours) may harbour this disease. Schistosomiasis, an infection by blood flukes, is found in cattle, water buffalo and other animals in several parts of the world; its life cycle goes from eggs excreted in urine and faeces, developing into larvae, which enter snails, then to free-swimming cercariae that attach to and penetrate human skin. Penetration can occur while workers are wading in water.

Some zoonoses are arthropod-borne viral diseases. The primary vectors for these diseases are mosquitoes, ticks and sandflies. These diseases include arboviral encephalitides transmitted by ticks and milk from sheep, babesiosis transmitted by ticks from cattle and Crimean-Congo haemorrhagic fever (Central Asian haemorrhagic fever) transmitted by mosquitoes and ticks from cattle, sheep and goats (as amplifying hosts) during epizootics (Benenson 1990; Mullan and Murthy 1991).

Preventive Action

The principal occupational hazards that occur in rearing ruminants include injuries, respiratory problems and zoonotic diseases. (See “A checklist for livestock rearing safety practices”.)

Stair steps should be maintained in good condition, and floors must be even to reduce fall hazards. Guards on belts, mechanical screws, compression rams and shear sharpening equipment should be maintained. Wiring should be maintained in good condition to prevent electrical shock. Ventilation should be assured wherever internal combustion engines are used in barns.

Training and experience in properly handling animals helps to prevent injuries related to the animals’ behaviour. Safe livestock handling requires understanding of both innate and acquired components of animal behaviour. Facilities should be designed so workers do not have to enter small or enclosed areas with animals. Lighting should be diffuse, since animals may become confused and balk around bright lights. Sudden noises or movements may startle cattle, causing them to crowd a person against hard surfaces. Even clothing hanging on fences flapping in the wind can startle cattle. They should be approached from the front so as not to surprise them. Avoid use of contrasting patterns in cattle facilities, because cattle will slow or stop when they see these patterns. Shadows across the floor should be avoided because cattle may refuse to cross over them (Gillespie 1997).

Risks of organic dust exposure can be minimized in several ways. Workers should be aware of the health effects of breathing organic dust and inform their physician about recent dust exposures when seeking help for respiratory illness. Minimizing spoilage of feed can minimize potential fungal spore exposures. To avoid such hazards, workers should use mechanized equipment to move decaying materials. Farm operators should use local exhaust ventilation and wet methods of dust suppression to minimize exposure. Appropriate respirators should be worn when organic dust exposure cannot be avoided (NIOSH 1994).

Preventing zoonoses depends upon maintaining clean livestock facilities, vaccinating the animals, quarantine of sick animals and avoiding exposure to sick animals. Rubber gloves should be worn when treating sick animals to avoid exposures through any cuts in the hands. Workers who become sick after contact with a sick animal should seek medical help (Gillespie 1997).



Read 12980 times Last modified on Wednesday, 07 September 2011 18:58
More in this category: « Dairy Pigs »

" DISCLAIMER: The ILO does not take responsibility for content presented on this web portal that is presented in any language other than English, which is the language used for the initial production and peer-review of original content. Certain statistics have not been updated since the production of the 4th edition of the Encyclopaedia (1998)."


Livestock Rearing References

Aldhous, P. 1996. Scrapie theory fed BSE complacency, now fears grow for unborn babies. New Scientist 150:4-5.

Ahlgren, GH. 1956. Forage Crops. New York: McGraw-Hill Book Co.

American Conference of Governmental Industrial Hygienists (ACGIH). 1994. Threshold Limit Values for Chemical Substances and Physical Agents and Biological Exposure Indices. Cincinnati, OH: ACGIH.

Auty, JH. 1983. Draught animal power in Australia. Asian Livestock VIII:83-84.

Banwart, WC and JM Brenner. 1975. Identification of sulfur gases evolved from animal manures. J Environ Qual 4:363-366.

Baxter, PJ. 1991. Toxic marine and freshwater algae: An occupational hazard? Br J Ind Med 48(8):505-506.

Bell, RG, DB Wilson, and EJ Dew. 1976. Feedlot manure top dressing for irrigated pasture: Good agricultural practice or a health hazard? B Environ Contam Tox 16:536-540.

Benenson, AS. 1990. Control of Communicable Diseases in Man. Washington, DC: American Public Health Association.

—. 1995. Control of Communicable Diseases Manual. Washington, DC: American Public Health Association.

Brown, LR. 1995. Meat production takes a leap. In Vital Signs 1995: The Trends that are Shaping our Future, edited by LR Brown, N Lenssen, and H Kane. New York: WW Norton & Company.

Bursey, RG. 1992. New uses of dairy products. In New Crops, New Uses, New Markets: Industrial and Commercial Products from U.S. Agriculture: 1992 Yearbook of Agriculture. Washington, DC: USDA.

Calandruccio, RA and JH Powers. 1949. Farm accidents: A clinical and statistical study covering twenty years. Am Surg (November):652-660.

Cameron, D and C Bishop. 1992. Farm accidents in adults. Br Med J 305:25-26.

Caras, RA. 1996. A Perfect Harmony: The Intertwining Lives of Animals and Humans throughout History. New York: Simon & Schuster.

Carstensen, O, J Lauritsen, and K Rasmussen. 1995. The West-Justland study on prevention of farm accidens, Phase 1: A study of work specific factors in 257 hospital-treated agricultural injuries. Journal of Agricultural Safety and Health 1:231-239.

Chatterjee, A, D Chattopadhyay, D Bhattacharya, Ak Dutta, and DN Sen Gupta. 1980. Some epidemiologic aspects of zoophilic dermatophytosis. International Journal of Zoonoses 7(1):19-33.

Cherry, JP, SH Fearirheller, TA Foglis, GJ Piazza, G Maerker, JH Woychik, and M Komanowski. 1992. Innovative uses of animal byproducts. In New Crops, New Uses, New Markets: Industrial and Commercial Products from U.S. Agriculture: 1992 Yearbook of Agriculture. Washington, DC: USDA.

Crowley, M. 1995. Aquaculture trends and technology. National Fisherman 76:18-19.

Deere & Co. 1994. Farm and Ranch Safety Management. Moline, IL: Deere & Co.

DeFoliart, GR. 1992. Insects as human foods. Crop Protection 11:395-399.

Donham, KJ. 1985. Zoonotic diseases of occupational significance in agriculture: A review. International Journal of Zoonoses 12:163-191.

—. 1986. Hazardous agents in agricultural dusts and methods of evaluation. Am J Ind Med 10:205-220.

Donham, KJ and LW Knapp. 1982. Acute toxic exposure to gases from liquid manure. J Occup Med 24:142-145

Donham, KJ and SJ Reynolds. 1995. Respiratory dysfunction in swine production workers: Dose-response relationship of environmental exposures and pulmonary function. Am J Ind Med 27:405-418.

Donham, KJ and L Scallon. 1985. Characterization of dusts collected from swine confinement buildings. Am Ind Hyg Assoc J 46:658-661.

Donham, KJ and KM Thu. 1995. Agriculture medicine and enivronmental health: The missing component of the sustainable agricultural movement. In Agricultural health and safety: Workplace, Environment, Sustainability, edited by HH McDuffie, JA Dosman, KM Semchuk, SA Olenchock, and A Senthilselvan. Boca Raton, FL: CRC Press.

Donham, KJ, MJ Rubino, TD Thedell and J Kammenmeyer. 1977. Potential health hazards of workers in swine confinement buildings. J Occup Med 19:383-387.

Donham, KJ, J Yeggy, and RR Dauge. 1985. Chemical and physical parameters of liquid manure from swine confinement facilities: Health implications for workers, swine and the environment. Agricultural Wastes 14:97-113.

—. 1988. Production rates of toxic gases from liquid manure: Health implications for workers and animals in swine buildings. Bio Wastes 24:161-173.

Donham, KJ, DC Zavala, and JA Merchant. 1984. Acute effects of work environment on pulmonary functions of swine confinement workers. Am J Ind Med 5:367-375.

Dosman, JA, BL Graham, D Hall, P Pahwa, H McDuffie, M Lucewicz, and T To. 1988. Respiratory symptoms and alterations in pulmonary function tests in swine producers in Saskatchewan: Results of a survey of farmers. J Occ Med 30:715-720.

Douglas, JDM. 1995. Salmon farming: Occupational health in a new rural industry. Occup Med 45:89-92.

Douglas, JDM and AH Milne. 1991. Decompression sickness in fish farm workers: A new occupational hazard. Br Med J 302:1244-1245.

Durning, AT and HB Brough. 1992. Reforming the livestock economy. In State of the World, edited by LR Brown. London: WW Norton & Company.

Erlich, SM, TR Driscoll, JE Harrison, MS Frommer, and J Leight. 1993. Work-related agricultural fatalities in Australia, 1982-1984. Scand J Work Environ Health 19:162-167.

Feddes, JJR and EM Barber. 1994. Agricultural engineering solutions to problems of air contaminants in farm silos and animal buildings. In Agricultural Health and Safety: Workplace, Environment, Sustainability, edited by HH McDuffie, JA Dosman, KM Semchuk, SA Olenchock and A Senthilselvan. Boca Raton, FL: CRC Press.

Ferguson, IR and LRC Path. 1993. Rats, fish and Weil’s disease. Safety and Health Practitioner :12-16.

Food and Agriculture Organization (FAO) of the United Nations. 1965. Farm Implements for Arid and Tropical Regions. Rome: FAO.

—. 1995. The State of the World Fisheries and Aquaculture. Rome: FAO.

Fretz, P. 1989. Injuries from farm animals. In Principles of Health and Safety in Agriculture, edited by JA Dosman and DW Crockcroft. Boca Raton, FL: CRC Press.

Froehlich, PA. 1995. Engineering Control Observations and Recommendations for Insect Rearing Facilities. Cincinnati, OH: NIOSH.

Gillespie, JR. 1997. Modern Livestock and Poultry Production. New York: Delmar Publishers.

Gorhe, DS. 1983. Draught animal power vs mechanization. Asian Livestock VIII:90-91.

Haglind, M and R Rylander. 1987. Occupational exposure and lung function measurements among workers in swine confinement buildings. J Occup Med 29:904-907.

Harries, MG and O Cromwell. 1982.Occupational allergy caused by allergy to pig’s urine. Br Med J 284:867.

Heederick, D, R Brouwer, K Biersteker, and J. Boleij. Relationship of airborne endotoxin and bacteria levels in pig farms with lung function and respiratory symptoms of farmers. Intl Arch Occup Health 62:595-601.

Hogan, DJ and P Lane. 1986. Dermatologic disorders in agriculture. Occup Med: State Art Rev 1:285-300.

Holness, DL, EL O’Glenis, A Sass-Kortsak, C Pilger, and J Nethercott. 1987. Respiratory effects and dust exposures in hog confinement farming. Am J Ind Med 11:571-580.

Holness, DL and JR Nethercott. 1994. Acute and chronic trauma in hog farmers. In Agricultural Health and Safety: Workplace, Environment, Sustainability, edited by HH McDuffie, JA Dosman, KM Semchuk, SA Olenchock, and A Senthilselvan. Boca Raton, FL: CRC Press.

Iowa Department of Public Health. 1995. Sentinel Project Research Agricultural Injury Notification System. Des Moines, IA: Iowa Department of Public Health.

Iverson, M, R Dahl, J. Korsgaard, T Hallas, and EJ Jensen. 1988. Respiratory symptoms in Danish farmers: An epidemiological study of risk factors. Thorax 48:872-877.

Johnson, SA. 1982. Silkworms. Minneapolis, MN: Lerner Publications.

Jones, W, K Morring, SA Olenchock, T Williams, and J. Hickey. 1984. Environmental study of poultry confinement buildings. Am Ind Hyg Assoc J 45:760-766.

Joshi, DD. 1983. Draught animal power for food production in Nepal. Asian Livestock VIII:86-87.

Ker, A. 1995. Farming Systems in the African Savanna. Ottawa,Canada: IDRC Books.

Khan, MH. 1983. Animal as power source in Asian agriculture. Asian Livestock VIII:78-79.

Kiefer, M. 1996. Florida Department of Agriculture and Consumer Services Division of Plant Industry, Gainesville, Florida. Cincinnati, OH: NIOSH.

Knoblauch, A, B Steiner, S Bachmann, G Trachsler, R Burgheer, and J Osterwalder. 1996. Accidents related to manure in eastern Switzerland: An epidemiological study. Occup Environ Med 53:577-582.

Kok, R, K Lomaliza, and US Shivhare. 1988. The design and performance of an insect farm/chemical reactor for human food production. Canadian Agricultural Engineering 30:307-317.

Kuo, C and MCM Beveridge. 1990. Mariculture: Biological and management problems, and possible engineering solutions. In Engineering for Offshore Fish Farming. London: Thomas Telford.

Layde, PM, DL Nordstrom, D Stueland, LB Wittman, MA Follen, and KA Olsen. 1996. Animal-related occupational injuries in farm residents. Journal of Agricultural Safety and Health 2:27-37.

Leistikow, B Donham, JA Merchant, and S Leonard. 1989. Assessment of U.S. poultry worker respiratory risk. Am J Ind Med 17:73-74.

Lenhart, SW. 1984. Sources of respiratory insult in the poultry processing industry. Am J Ind Med 6:89-96.

Lincoln, JM and ML Klatt. 1994. Preventing Drownings of Commercial Fishermen. Anchorage, AK: NIOSH.

MacDiarmid, SC. 1993. Risk analysis and the importation of animals and animal products. Rev Sci Tech 12:1093-1107.

Marx, J, J Twiggs, B Ault, J Merchant, and E Fernandez-Caldas. 1993. Inhaled aeroallergen and storage mite reactivity in a Wisconsin farmer nested case-control study. Am Rev Respir Dis 147:354-358.

Mathias, CGT. 1989. Epidemiology of occupational skin disease in agriculture. In Principles of Health and Safety in Aagriculture, edited by JA Dosman and DW Cockroft. Boca Raton, FL: CRC Press.

Meadows, R. 1995. Livestock legacy. Environ Health Persp 103:1096-1100.

Meyers, JR. 1997. Injuries among Farm Workers in the United States, 1993. DHHS (NIOSH) Publication No. 97-115. Cincinnati, OH: NIOSH.

Mullan, RJ and LI Murthy. 1991. Occupational sentinel health events: An up-dated list for physician recognition and public health surveillance. Am J Ind Med 19:775-799.

National Institute for Occupational Safety and Health (NIOSH). 1993. Injuries among Farm Workers in the United states. Cincinnati, OH: NIOSH.

—. 1994. Request for Assistance in Preventing Organic Dust Toxic Syndrome. Washington, DC: GPO.

National Institutes of Health (NIH). 1988. Institutional Administrator’s Manual for Laboratory Animal Care and Use. Washington, DC: GPO.

National Research Council (NRC). 1989. Alternative Agriculture: Committee on the Role of Alternative Farming Methods in Modern Production Agriculture. Washington, DC: National Academy Press.

National Safety Council. 1982. Accident Facts. Chicago, IL: National Safety Council.

—. 1985. Electrofishing. NSC data sheet I-696-85. Chicago, IL: National Safety Council.

Nesheim, MC, RE Austic, and LE Card. 1979. Poultry Production. Philadelphia, PA: Lea and Febiger.

Olenchock, S, J May, D Pratt, L Piacitelli, and J Parker. 1990. Presence of endotoxins in different agricultural environments. Am J Ind Med 18:279-284.

O’Toole, C. 1995. Alien Empire. New York: Harper Collins Publishers.

Orlic, M and RA Leng. 1992. Prelimenary Proposal to Assist Bangladesh to Improve Ruminant Livestock Productivity and Reduce Methane Emissions. Washington, DC: US Environmental Protection Agency, Global Change Division.

Panti, NK and SP Clark. 1991. Transient hazardous conditions in animal building due to manure gas release during slurry mixing. Applied Engineering in Agriculture 7:478-484.

Platt, AE. 1995. Aquaculture boosts fish catch. In Vital Signs 1995: The Trends that Are Shaping our Future, edited by LR Brown, N Lenssen, and H Kane. New York: WW Norton & Company.

Pursel, VG, CE Rexroad, and RJ Wall. 1992. Barnyard biotchnology may soon produce new medical therapeutics. In New Crops, New Uses, New Markets: Industrial and Commercial Products from U.S. Agriculture: 1992 Yearbook of Agriculture Washington, DC: USDA.

Ramaswami, NS and GL Narasimhan. 1982. A case for building up draught animal power. Kurushetra (India’s Journal for Rural Development) 30:4.

Reynolds, SJ, KJ Donham, P Whitten, JA Merchant, LF Burmeister, and WJ Popendorf. 1996. A longitudinal evaluation of dose-response relationships for environmental exposures and pulmonary function in swine production workers. Am J Ind Med 29:33-40.

Robertson, MH, IR Clarke, JD Coghlan, and ON Gill. 1981. Leptospirosis in trout farmers. Lancet: 2(8247)626-627.

Robertson, TD, SA Ribeiro, S Zodrow, and JV Breman. 1994. Assessment of Strategic Livestock Feed Supplementation as an Opportunity for Generating Income for Small Scale Dairy Producers and Reducing Methane Emissions in Bangladesh. Washington, DC: US Environmental Protection Agency.

Rylander, R. 1994. Symptoms and mechanisms: Inflammation of the lung. Am J Ind Med 25:19-24.

Rylander, R, KJ Donham, C Hjort, R Brouwer, and D Heederik. 1989. Effects of exposure to dust in swine confinement buildings: A working group report. Scand J Work Environ Health 15:309-312.

Rylander, R and N Essle. 1990. Bronchial hyperactivity among pig and dairy farmers. Am J Ind Med 17:66-69.

Rylander, R, Y Peterson, and KJ Donman. 1990. Questionnaire evaluating organic dust exposure. Am J Ind Med 17:121-128.

Rylander, R and R Jacobs. 1994. Organic Dusts: Exposure, Effects and Prevention. Chicago, IL: Lewis Publishing.
Safina, C. 1995. The world’s imperiled fish. Sci Am 272:46-53.

Scherf, BD. 1995. World Watch List for Domestic Animal Diversity. Rome: FAO.

Schmidt, MJ. 1997. Working elephants. Sci Am 279:82-87.

Schmidt, JO. 1992. Allergy to venomous insects. In The Hive and the Honey Bee, edited by JM Graham. Hamilton: DaDant & Sons.

Shumacher, MJ and NB Egen. 1995. Significance of Africanized bees on public health. Arch Int Med 155:2038-2043.

Sherson, D, I Hansen, and T Sigsgaard. 1989. Occupationally related respiratory symptoms in trout-processing workers. Allergy 44:336-341.

Stem, C, DD Joshi, and M Orlic. 1995. Reducing Methane Emissions from Ruminant Livestock: Nepal prefeasibility Study. Washington, DC: US Environmental Protection Agency, Global Change Division.

Sweeten, JM. 1995. Odor measurement technology and applications: A state-of-the-art review. In Seventh International Symposium on Agricultural and Food Processing Wastes: Proceedings of the 7th International Symposium, edited by CC Ross. American Society of Agricultural Engineering.

Tannahill, R. 1973. Food in History. New York: Stein and Day.

Thorne, PS, KJ Donham, J Dosman, P Jagielo, JA Merchant, and S Von Essen. 1996. Occupational health. In Understanding the Impacts of Large-scale Swine Production, edited by KM Thu, D Mcmillan, and J Venzke. Iowa City, IA: University of Iowa.

Turner, F and PJ Nichols. 1995. Role of the epithelium in the response of the airways. Abstract for the 19th Cotton and Other Organic Dust Research Conference, 6-7 January, San antonio, TX.

United Nations Development Programme (UNDP). 1996. Urban Agriculture: Food, Jobs, and Sustainable Cities. New York: UNDP.

US Department of Agriculture (USDA). 1992. Agricultural Waste Management Field Handbook. Washington, DC: USDA Soil Conservation Service.

—. 1996a. Livestock and Poultry: World Markets and Trade. Circular Series FL&P 1-96. Washington DC: USDA Foreign Agricultural Service.

—. 1996b. Dairy: World Markets and Trade. Circular Series FD 1-96. Washington DC: USDA Foreign Agricultural Service.

—. 1997. Poultry Production and Value, 1996 Summary. Washington, DC: National Agricultural Statistics Service.

van Hage-Hamsten, M, S Johansson, and S Hogland. 1985. Storage mite allergy is common in a farming population. Clin Allergy 15:555-564.

Vivian, J. 1986. Keeping Bees. Charlotte, VT: Williamson Publishing.

Waller, JA. 1992. Injuries to farmers and farm families in a dairy state. J Occup Med 34:414-421.

Yang, N. 1995. Research and development of buffalo draught power for farming in China. Asian Livestock XX:20-24.

Zhou, C and JM Roseman. 1995. Agriculture-related residual injuries: Prevalence, type, and associated factors among Alabama farm operators, 1990. Journal of Rural Health 11:251-258.

Zuehlke, RL, CF Mutel, and KJ Donham. 1980. Diseases of Agricultural Workers. Iowa City, IA: Department of Preventive Medicine and Environmental Health, University of Iowa.