The dairy farmer is a livestock specialist whose aim is optimizing the health, nutrition and reproductive cycling of a herd of cows with the ultimate goal of maximal milk production. Major determinants of the farmer’s exposure to hazards are farm and herd size, labour pool, geography and degree of mechanization. A dairy farm may be a small family business milking 20 or fewer cows per day, or it may be a corporate operation using three shifts of workers to feed and milk thousands of cows around the clock. In regions of the world where the climate is quite mild, the cattle may be housed in open sheds with roofs and minimal walls. Alternatively, in some regions barns must be tightly closed to preserve sufficient heat to protect the animals and the watering and milking systems. All of these factors contribute variability to the risk profile of the dairy farmer. Nevertheless, there are a series of hazards which most people working in dairy farming around the world will encounter to at least some degree.
Hazards and Precautions
One potential hazard which clearly relates to the degree of mechanization is noise. In dairy farming, harmful noise levels are common and always related to some type of mechanical device. Leading offenders outside of the barn are tractors and chain-saws. Noise levels from these sources are often at or above the 90-100 dBA range. Within the barn, other noise sources include bedding choppers, small skid-steer loaders and milking pipeline vacuum pumps. Here again, sound pressures may exceed those levels generally considered to be damaging to the ear. Although the studies of noise-induced hearing loss in dairy farmers are limited in number, they combine to show a convincing pattern of hearing deficits affecting predominantly the higher frequencies. These losses can be quite substantial and occur considerably more frequently in farmers of all ages than in non-farm controls. In several of the studies, the losses were more notable in the left than the right ear—possibly because farmers spend much of their time with the left ear turned toward the engine and muffler when driving with an implement. Prevention of these losses may be accomplished by efforts directed at noise abatement and muffling, and institution of a hearing-conservation programme. Certainly, the habit of wearing hearing protective devices, either muffs or earplugs, may help substantially to reduce the next generation’s risk of noise-induced hearing loss.
The dairy farmer has contact with some chemicals which are commonly found in other types of agriculture, as well as some which are specific to the dairy industry, such as those used for cleaning the automated vacuum-powered milking pipeline system. This pipeline must be effectively cleaned before and after each use. Commonly this is done by first flushing the system with a very strong alkaline soap solution (typically 35% sodium hydroxide), followed by an acidic solution such as 22.5% phosphoric acid. A number of injuries have been observed in association with these chemicals. Spills have resulted in significant skin burns. Splatters may injure the cornea or conjunctivae of unprotected eyes. Tragic accidental ingestion—often by young children—which may occur when these materials are pumped into a cup and then briefly left unattended. These situations can be best prevented by the use of an automated, closed flush system. In the absence of an automated system, precautions must be taken to restrict access to these solutions. Measuring cups should be clearly labelled, reserved for only this purpose, never left unattended and rinsed thoroughly after each use.
Like others working with livestock, dairy farmers may have exposure to a variety of pharmaceutical agents ranging from antibiotics and progestational agents to prostaglandin inhibitors and hormones. Depending upon the country, dairy farmers also may use fertilizers, herbicides and insecticides with varying degrees of intensity. In general, the dairy farmer uses these agrochemicals less intensively than persons working in some other types of farming. However, the same care in mixing, applying and storing these materials is necessary. Appropriate application techniques and protective garb are as important for the dairy farmer as anyone else working with these compounds.
Although data on the prevalence of all musculoskeletal problems are currently incomplete, it is clear that dairy farmers have increased risk of arthritis of the hip and knee compared to nonfarmers. Similarly, their risk of back problems may also be elevated. Although not well studied, there is little question that ergonomics is a major problem. The farmer may routinely carry weights in excess of 40 kg—often in addition to considerable personal body weight. Tractor driving produces abundant vibration exposure. However, it is the portion of the job devoted to milking that seems most ergonomically significant. A farmer may bend or stoop 4 to 6 times in the milking of a single cow. These motions are repeated with each of a number of cows twice daily for decades. Carrying the milking equipment from stall to stall imposes an additional ergonomic load on the upper extremities. In countries where milking is less mechanized, the ergonomic load on the dairy farmer might be different, but still it is likely to reflect considerable repetitive strain. A potential solution in some countries is the shift to milking parlours. In this setting the farmer can milk a number of cows simultaneously while standing several feet below them in the central pit of the parlour. This eliminates the stooping and bending as well as the upper-extremity load of carrying equipment from stall to stall. The latter problem is also addressed by the overhead track systems being introduced in some Scandinavian countries. These support the weight of the milking equipment when moving between stalls, and can even provide a convenient seat for the milker. Even with these potential solutions, much remains to be learned about ergonomic problems and their resolution in dairy farming.
A closely linked problem is organic dust. This is a complex, often allergenic and generally ubiquitous material on dairy farms. The dust frequently has high concentrations of endotoxin and may contain beta-glucans, histamine and other biologically active materials (Olenchock et al. 1990). Levels of total and respirable dust may exceed 50 mg/m3 and 5 mg/m3, respectively, with certain operations. These most commonly involve work with microbially contaminated feed or bedding within a closed space such as a barn, hay loft, silo or grain bin. Exposure to these dust levels may result in acute problems such as ODTS or hypersensitivity pneumonitis (“farmer’s lung disease”). Chronic exposure may also play a role in asthma, farmer’s lung disease and chronic bronchitis, which seems to occur at twice the rate of a non-farm population (Rylander and Jacobs 1994). The prevalence rates of some of these problems are higher in settings where moisture levels in the feed are likely to be elevated and in areas where barns are more tightly closed because of climatic requirements. Various farming practices such as drying of the hay and shaking out of feed for the animals by hand, and the choice of bedding material, can be major determinants of the levels of both the dust and its associated illnesses. Farmers can often devise a number of techniques to minimize either the amount of microbial overgrowth or its subsequent aerosolization. Examples include the use of sawdust, newspapers and other alternative materials for bedding instead of moulded hay. If hay is used, the addition of a quart of water to the cut surface of the bale minimizes the dust generated by a mechanical bedding chopper. Capping vertical silos with plastic sheets or tarpaulins without additional feed on top of this layer minimizes the dust of subsequent uncapping. The use of small amounts of moisture and/or ventilation in situations where dust is likely to be generated is often possible. Finally, farmers must anticipate potential dust exposures and use appropriate respiratory protection in these situations.
Allergens may represent a troublesome health challenge for some dairy farmers. Major allergens appear to be those encountered in the barns, typically animal danders and “storage mites” living in feed stored within the barns. One study has extended the storage mite problem beyond the barn, finding sizeable populations of these species living within farmhouses as well (van Hage-Hamsten, Johansson and Hogland 1985). Mite allergy has been confirmed as a problem in a number of parts of the world, often with differing species of mites. Reactivity to these mites, to cow dander and to multiple other less significant allergens, results in several allergic manifestations (Marx et al. 1993). These include immediate onset of nasal and eye irritation, allergic dermatitis and, of greatest concern, allergy-mediated occupational asthma. This can occur as either an immediate or delayed (up to 12 hours) reaction and may occur in individuals not previously known to be asthmatic. It is of concern because the dairy farmer’s involvement in barn activities is daily, intensive and lifelong. With this nearly continual allergic re-challenge, progressively more severe asthma is likely to be seen in some farmers. Prevention includes avoidance of dust, which is the most effective and, unfortunately, the most difficult intervention for most dairy farmers. The results of medical therapies, including allergy shots, topical steroids or other anti-inflammatory agents, and symptomatic relief with bronchodilators, have been mixed.