ASAE Conference Proceeding
This is not a peer-reviewed article.
Working Conditions & Ergonomics when Milking Cows
P. Lundqvist, M. Stål and S. Pinzke
Pp. 59-65 in Fifth International Dairy Housing Proceedings of the 29-31 January 2003 Conference, (Fort Worth, Texas, USA), ed. K. A. Janni. ,Pub. date 29 January 2003 . ASAE Pub #701P0203
When milking cows in stanchion barns, milkers use various working postures and movements that involve walking, sitting, rising, squatting, kneeling, stooping, bending twisting and stretching. They must do this while holding a load of 3-6 kg (cluster, teat cups) in one hand under the cow's udder at a relatively long distance from the body. This is still the usual working situation for many farmers and farm workers in Swedish dairy production. An increasing part of the Swedish dairy farms have now loose-housing system with parlor milking, which reduces a lot of the ergonomic stress.
On the other hand there is a transition to large-scale milk production which involves new type of problems. An increasing number of the milkers and the relief personnel now working in dairy farming are young women who may have less physical strength than men. Additional research is needed to obtain data necessary for planning of safer and better dairy barns, in which all men or women can work. This paper is a short review of our research conducted over the past 20 years, with some analysis and recommendations for the future.KEYWORDS. Dairy production, working conditions, ergonomics, milking
Agriculture is one of the most dangerous occupations in many countries (U.S. Department of Labor, 1989). A number of studies at the Department of Agricultural Biosystems and Technology, Swedish University of Agricultural Sciences in Alnarp have also shown that people working in milk production have many ergonomical problems, including musculoskeltal injuries (Lundqvist, 1988; Pinzke, 1999; Stål, 1999). The need for improvements and prevention were discussed at a recent conference in Sweden. Improved legislation, education and information plus technical and organizational actions were suggested (Lundqvist and Pinzke, 2000).
The work in dairy barns is characterized by high work intensity, long working hours and considerable risk of injuries. Although the handling of silage and manure (heaviest work tasks in dairy farming, according to Ahonen et al, 1990) is now being mechanized, the basic tasks of milking are not changing rapidly, and are creating major ergonomic risks.
In the beginning of the 1970´s Vos (1974) and Tomlinson (1971) studied the design of the milking parlour to make it more suitable for the milker. Ergonomical research about milking in Sweden was started in the late 1970´s by a research group in Stockholm. Their laboratory studies of simulated milking assessed the shoulder load and the load on the knees and the leg muscles. The result revealed the importance of reducing milking machine weights and determined the optimal distance (vertical and horizontal) from the milker’s body to the cows udder (Arborelius et al, 1986).
Research on ergonomical aspects of cow milking are now being studied in a number of countries such as the Nordic countries, the Netherlands, the United States and Australia. Several literature reviews (Lundqvist, 1992; Fuller, 1994; van den Top, 1995) show that there is a need for further research and that international co-operation is the key to solving the existing problems. The Division of Work Science started in the 1980´s to conduct studies in milking ergonomics.
Observational Studies of Stanchion vs. Parlour Milking
Lundqvist (1988) carried out studies at nine selected farms that varied with respect to size, production patterns, layout, mechanization and other factors. The purpose of this investigation was to collect information to improve our ability to design work places in livestock buildings that are efficient, safe and acceptable from the point of view of ergonomics. The method used for ergonomical studies of body postures and body movements, was the Ovako Working posture Analysing System (OWAS), (Karhu et al., 1997; 1981). The OWAS method has been used in many different studies including the construction industry (Kivi and Mattila, 1991). The purpose of this investigation was to collect information to improve our ability to design work places in livestock buildings that are efficient, safe and acceptable from the point of view of ergonomics.
The results indicated that the postures and movements during milking are influenced by the work methods as well as by the layout of the work place. According to the results (Table 1) there is still no ideal ergonomic method for milking cows. Milking in stanchion barns involved unacceptable working postures during 38 per cent of the working time. The corresponding figure was 10 per cent in systems with a milking parlour.
Table 1. Percent of working postures observed during milking in four different action categories, according to the OWAS analysis (Action category in descending of acceptability I - IV). Arabic numerals 1 - 9 represent nine observation sites.
Action category Stanchion barn Milking parlor Milking parlor &
Rating by remover
observer ----------------------- --------------------------- --------------------------
(nine sites) 1 2 3 4 5 6 7 8 9
I Acceptable 79 59 47 90 29 92 82 91 94
II Action soon 21 25 49 9 8 7 16 9 4
III Very soon - 10 4 1 - 1 2 - 1
IV Immediate - 6 - - - - - - 1
Musculoskeletal Symptoms in Swedish Dairy Farmers
Gustafsson et al. (1994) conducted a mail survey of dairy farmers regarding their musculoskeletal problems. The analysis was based on the 2 087 male and 920 female respondents who were = 64 years old and milked more than five cows. In all, 82% of the men and 86% of the women reported some kind of musculoskeletal symptoms during the previous 12 months. Compared to reference data from other occupations, pain, and discomfort among dairy farmers were especially frequent in the shoulders, elbows, lower back, hips and knees. In addition females reported severe problems with the wrists and hands. Males had significantly more problems with the lower back and knees than the females (Table 2). The females had significantly more symptoms in the neck, shoulders, elbows, wrists/hands, upper back and hips than did the men. For each symptom a series of dichotomized quantitative and qualitative factors were used as independent variables in multivariate analysis. A limited number of significant associations were found and used to test hypotheses. It was concluded that strategies for both preventive and intervention measures referring to musculoskeletal complaints in dairy farmers must consider physical work place factors (buildings, tools, equipment) as well as personal and life style characteristics, such as gender, age, height, body weight and leisure time activities.
Table 2. Frequency of self-reported symptoms (percent) during the last 12 months among Swedish dairy farmers (2 087 males and 920 females). The reference valuesa are based on data from studies in a large number of other male and female professions. (< remarkably low frequency, > remarkably high frequency).
________________________________________________________________________ Male Female _________________________ __________________________
Parameter % Low High % Low High
Neck 25 <20 >30 35*b <30 >55
Shoulders 37 <15 >35 49* <30 >55
Elbows 18 <5 >15 22* <5 >20
Wrists/hands 18 <5 >20 35* <15 >35
Upper back 12 <5 >15 18* <10 >25
Lower back 55* <30 >50 50 <35 >50
Hips 23 <5 >15 27* <10 >20
Knees 41* <20 >30 37 <15 >30
Ankles/feet 13 <10 >20 16 <10 >20
a The reference values Low and High (percent) are defined after Jonsson (1988) as the mean
symptom frequency plus (High) minus (Low) one standard deviation of 29 ”male”
occupations and 40 ”female” occupations registered in similar surveys of more than 50
b The * denotes p = 0,05 differences between sexes (conventional X2 - analyses were used)
The prevalence and impact of selected factors on self-reported musculoskeletal complaints in Swedish female milkers with special reference to symptoms in the upper extremities were investigated using data from mail-in surveys (Stål et al, 1996).
An agricultural study group was formed of three subgroups: 161 active milkers, 108 non-milkers and 62 ex-milkers, women were former milkers. In the course of the analysis these subgroups were compared with a non-agricultural population consisting of 166 nursing assistants. Problems in the upper extremities were significantly more common in the agricultural group than in the non-agricultural group. Milkers ran a higher risk of developing symptoms in the wrists and hands than non-milking women. Symptoms such as numbness, coldness in the wrists and white fingers were more common in all agricultural subgroups than in the non-agricultural group. Numbness and white fingers were related to vibration exposure in the ex-milker and the non-milker groups but not in the milker group. Psychosocial factors such as job satisfaction were not related to the occurrence of symptoms. Milking in a modernized barn gave fewer elbow problems than milking in a traditional barn. Milkers who had received ergonomical instruction on how to work in order to reduce muscle stress had fewer problems in the elbow region than those who had not received this information.
In Depth Studies of the Hands and Wrists During Machine Milking
The aim of the studies (Pinzke and Stål, 2000; Pinzke et al, 2001 ) were to objectivly measure and analyze the hands movements, positions and muscle loads and quantify the forces effecting the hands and wrists during different work operations when milking cows. The methods used in the project were electromyography (EMG) for measuring the muscular activity, goniometry for measuring hand movements and positions, video analysis for time consumption and pressure measurement for getting the pressure distribution in the hand during milking. The studied work tasks were: 1) Drying the cow’s udder, 2) Pre-milking, and 3) Attaching the milking unit.
The results showed that the static and median loads were particularly high on the forearm flexor muscles during all three work operations, with the highest values during the task “Drying the cow’s udder”. The peak loads were also high with the highest value during the work task “Attaching the milking unit”. The wrist was most dorsiflexed during “Pre-milking” and most ulnar deviated during “Attaching the milking unit”. The highest median velocities were found for the task “Drying the cow’s udder” and the peak velocities for flexion and deviation for the milking task “Attaching the milking unit”.
The pressure distribution in the hand was fairly even for the task “Drying the cow’s udder” and got the highest mean load value of the three measured tasks. The work task “Pre-milking” showed the highest peak loads especially for the thumb and the index finger. The milking task “Attaching the milking unit” showed the lowest peak and mean load. The outermost part of the index finger and the little finger had most loads when holding the milking unit.
This study showed high load and position values for the work tasks “Drying the cow’s udder”, “Pre-milking”, and “Attaching the milking unit”. The development of new techniques that can facilitate these work tasks is necessary for reducing the musculuskeletal problems in the wrists and hands. Such research is going on at the Division of Work Science, Alnarp together with DeLaval, Sweden.
Measures to Improve Milking Ergonomics
Our department has been actively involved in the process of developing better and safer technologies for milkers. Examples of four such activities are described below:
What kind of practices can be recommended to reduce the health effect of poor working postures in milk production? Instructions to milkers about the importance of such factors as working methods, breaks and rest allowances, and the proper use of tools and equipment are often neglected. The Swedish Agricultural Relief Service Corporation (temporary hired help) has employed instructors to train their employees in prevention of ergonomic work injuries. They also present information at agricultural schools and farm meetings (Lundqvist, 1991).
A new milking system suggested by Ekelund (1978) for stanchion barns has been commercially available for a number of years. The milking system has an overhead rail which carries all the milking equipment. The equipment can easily be moved from cow to cow with minimal lifting and carrying. The farmers using this kind of system are reporting less strain on the neck and shoulders, arms, and to some extent, on the lower back (Andersdotter et al 1988). This system has later been developed with automatic milking cluster removal.
A measure to improve the working conditions in milking parlours is to install a floor adjustable to the height of each worker. It has been found that the milker´s elbows should be about 0.30 m above the floor level of the cow (Stål and Pinzke, 1991). In the study it was found that the standard milking parlours results in excessive bending for tall people and excessive stretching for short people.
It is important to reduce the weight of the milking unit (teat cups, cluster), to prevent hand, arm and shoulder problems. The unit normally weighs about 3 kilograms which, during the positioning, is held at a relatively long distance from the body. A device that supports the milking unit, reduces the handled weight, and automatically detaches the milking unit after milking, would improve the working conditions substantially. Such a device has been evaluated (Pinzke and Stål, 1992) by using biomechanical calculations and the Borg-scale for ratings of exertion. The results showed a 60% decrease in the load on the milker´s shoulder by using this device. The Borg-scale result was in good agreement with the biomechanical calculations. The development of this product is proceeding as well as further evaluation studies with promising results (Stål, et al., 2000; 2001).
The result of studies on the milkers´ musculoskeletal system clearly shows the great need for improved ergonomic systems. Female workers seem to suffer more serious problems than males. Through further studies we hope to find the reasons for their troubles. These findings might be used for preemployment examination of beginning female milkers, for physical training programs and for preventive process modifications at work.
In Sweden, there is a transition towards large-scale milk production. From traditional family farms with 20-30 cows, we now quite often see farms with 200 - 300 cows. Some are family farms, which have increased their herd of cows and made heavy investments. In other situations it is farms owned by a couple of farmers or other solutions. This means that much more investments, technology and labour are needed, which has an important impact on the working conditions. Financed by the Agricultural Research Program of Southern Sweden (Stiftelsen Sydsvensk Jordbruksforskning), we are now closely following a number of large-scale milk-producing farms in southern Sweden for a year (Lundqvist et al., 2000). Working conditions, such as ergonomics, accidents, work organization, stress, leadership etc. are monitore for everyone involved. Results are also linked to productivity and milk quality. The project is using Internet, for communication and reporting to and from the farms and also for reporting the project to interested people through the project home page (http://www.jbt.slu.se/AAT_MILK/). The aim is to find out what is needed to establish good working conditions in large-scale milk-production and to show how the Internet can be used both in research and extension activities.
Another area for future research, which is not covered in this paper is the development and use of automated milking machines. This revolution in dairy production - the automatic milking - brings up many discussion points. From the work science point of view the question about avoiding new risks when it comes to health and safety has been important (Lundqvist, 1992). We still believe that systematic evaluations of the consequences for human health and safety should go hand in hand with the evaluations of animal health and welfare. Reports from farmers show that there have been initial problems, and improvements still need to be made. So far the main impression is that this development will make dairy production less stressful, less risky and much more interesting.
In conclusion, it is necessary to improve the ergonomic design of the milking process. However, the highest degree of safety and comfort that is economically possible must be planned in advance and built into the design of tools and equipment as well as new automated milking systems!
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