Dairy cows can suffer from a range of welfare and disease problems, including mastitis, lameness, ketosis and milk fever. These are related to the high milking yields required by the modern dairy industry.
July 2009 saw new reports published by the European Food Safety Authority (EFSA) which concluded that cows in the European Union are bred to produce unreasonable amounts of milk and suffer from hunger, lameness and infertility.
This is one of the most common problems with over 30% of the UK dairy herd contracting this every year. Mastitis is a painful infection of the mammary gland (udder) caused mainly by bacteria such as streptococci, coliforms and staphylococci. Severe infections cause swelling of the udder, fever and sometimes death. Infection can lead to depressed appetite, dehydration and severe diarrhoea and can be fatal. Mastitis is commonly caused by poor hygiene in cubicle houses and milking parlours, especially where cattle are forced to lie in damp and dirty conditions. Milk is extracted by a method known as vacuum pulsation, this means that tissue may be weakened and so more prone to infection. Over milking can also cause teat injuries leading to mastitis.
This can affect around between 10 to 50% of dairy cows each year with practically all showing signs of foot damage by the time they are slaughtered. Cows suffering from lameness can be in considerable pain. Lameness is most commonly due to the abnormally large udder of the dairy cow distorting the gait and posture of the cow’s hind limbs so predisposing to foot damage and subsequent lameness. Lameness can also be caused or exacerbated by inappropriate housing or feeding. Many cows are still housed in cubicles built 20 to 30 years ago. Today's dairy cows are larger and longer than their predecessors and are often forced to stand with their hind feet in the passageway in which manure collects. This can soften the cow’s hooves and encourages infection. The use of silage rather than hay as the main winter fodder has increased the problem as cows eating silage excrete more urine and wetter faeces causing more problems with wet bedding and wet slurry in passageways. Dairy cows are fed starchy, high protein concentrated feeds in order to maintain high milk yields. These can lead to ruminal acidosis in which the rumen becomes increasingly acidic. Acidosis leads to inflammatory substances being released into the blood which supplies the sensitive laminae of the cow’s feet. The feet become hot, swollen and inflamed causing lameness.
Acidosis can also lead to the problem of ketosis. Ketosis is a very common disease that occurs during early lactation and is due to the cow’s metabolism being pushed too hard in order to sustain milk yield. Cows with ketosis become progressively depressed and lethargic. In severe cases cows lose weight, become dehydrated and show nervous, agitated behaviour such as delerium, bellowing and walking in circles.
Milk Fever (hypocalcaemia)
Milk fever is caused by the sudden depletion of the body's calcium reserves due to the onset of milk production after giving birth. Some cows may experience loss of body temperature control by the nervous system causing them to be cold rather than feverish. If untreated, the cow becomes progressively weaker and is unable to stand due to other nerve functions being affected. They may then become unconscious and die. Milk fever affects around 6% of dairy cows; this figure has remained relatively consistent for the last 15 years that the Dairy Herd Health and Productivity Service (DHHPS) have been keeping records(12).
BSE Bovine Spongiform Encephalopathy (BSE)
This was first recognised and defined in the UK in November 1986, reaching its peak in 1992 when over 37,000 cases were confirmed in the UK alone(1,13). BSE is a neurological disorder occurring in adult animals of 5 years old or older. Affected animals show signs including; a change in mental state, abnormalities of posture, movement and sensation. The clinical disease usually lasts for several weeks and is invariably progressive and fatal. Over 180,000 cases of BSE have now been confirmed in the UK alone(1). New legislation to replace the Over Thirty Month (OTM) rule by BSE testing was introduced in November 2005. The OTM rule imposed an automatic ban on all older cattle from entering the human food chain. Subject to negative BSE testing, the new system will allow UK cattle born after 31st July 1996 to be slaughtered and sold for human consumption. New legislation states that cattle born before 1 August 1996 cannot be slaughtered for human consumption and consignment of these animals to a fresh meat slaughterhouse will be an offence. These animals must be slaughtered under the Older Cattle Disposal Scheme (OCDS) (1,13).
Bovine Tuberculosis (bTB)
This is caused by the bacterium Mycobacterium bovis (M. bovis). Tuberculosis can also affect other species including other farm animals and wildlife, along with humans. The spread of infection to people by contaminated milk or dairy produce was an important public health issue before pasteurisation was widely used. Cattle with suspected bTB are usually identified by the tuberculin skin test before they develop clinical signs. Diagnosis is confirmed through post-mortem examination and bacteriological culture of M. bovis organisms(1).
Foot and Mouth
This is an infectious disease caused by a virus (of which there are 7 types). The virus affects cloven-hoofed animals such as cattle, sheep, pigs, goats and deer. The disease is not normally fatal to adult animals but it does cause debilitation and loss of productivity for farmers (decreasing milk yields and lameness). The virus causes a fever and the development of blisters, mostly in the mouth and on the feet. Animals contract the disease by either direct contact with an infected animal or contact with foodstuffs, etc. which have become contaminated by an infected animal. The UK last experienced the disease in 2001, with 2,030 confirmed cases of foot and mouth spread across the country. 0.7 million cattle were culled as a result of this outbreak(1).
Cows can also suffer from a range of other diseases. These can include grass staggers (due to magnesium deficiency), viral pneumonia, salmonellosis, bovine virus diarrhoea, brucellosis (causing abortion) and endometritis - an inflammation of the uterus caused by poor hygiene at calving. The majority of calf deaths occur in the first month of life, mostly from septicaemia and scours (localised infections of the intestines).
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