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Being a skin gland, the only way infection can reach the udder is from the outside.
Mastitis is the inflammation of the mammary gland which generally occurs as a result of white blood cells being released – the body’s response to invasion by bacteria, usually via the teat canal.
Over 200 different micro-organisms have been shown to cause intramammary infections, but most of the economic losses are associated with staphylococci, streptococci and coliform bacteria.
The microorganisms that most frequently cause mastitis are often categorised as either environmental or contagious pathogens, although organisms can show characteristics of both groups.
The root words contributing to the term mastitis are mast (udder/ breast) and itis (inflammation). Some people think of the udder as a bag of milk and mastitis a problem when the milk goes bad, but that is only part of the story.
The udder is in fact a very fleshy tissue, and while it has tiny milk producing pockets (alveoli) and milk ducts, the vast majority if it is cells and blood vessels. Therefore when the udder gets inflamed we have an inflamed tissue, or an inflamed organ (which, believe it or not, is classified as a skin gland by those in the know).
Being a skin gland, the only way infection can reach the udder is from the outside.
The teat end is designed to keep bacteria and other nasties (such as yeasts, e.g. thrush) on the outside.
It has a tight circular ring (sphincter) and sticky layers of keratin to stop would be intruders in their tracks. Infection only occurs when the teat canal is open/damaged and there is significant challenge (numbers of bacteria) on the outside.
Environmental
Exposure of the teat surface to environmental bacteria occurs mainly between milking times.
Sources of environmental bacteria like Strep. uberis include faeces, genital discharges, bedding material, feedstuffs, soil and water.
These bacteria cannot practically be eliminated from the cow’s environment, and the teat-end in particular is often in prolonged and close contact with some of these materials. Once udder infections with these environmental bacteria are established within the herd, transmission from infected quarters to other quarters and cows can occur at milking time.
Contagious Mastitis
Contagious bacteria often stem from an infected udder. However, bacteria such as Staph. aureus also readily colonises the teat canal and chapped or sore teat skin and may survive at other sites on the cow.
Contagious bacteria are primarily spread at milking time, when bacteria from infected quarters is spread to other quarters by splashes of milk during stripping, or by the hands of operator’s and milking machines.
Solid biosecurity practices, regular monitoring and timely vaccination are the three key pillars of effective Bovine Viral Diarrhoea (BVD) control on New Zealand farms. Zoetis veterinary technical advisor, Karley DeFrees, explains BVD is a costly but preventative disease that impacts a significant number of dairy farms in New Zealand. Implementation of a BVD control plan can help protect your herd from this avoidable disease.
Although preventable, lamb loss from clostridial diseases during the first year of life on New Zealand hill country farms continues to be an issue. A field trial, where lambs were vaccinated at docking and weaning, demonstrated that vaccination was highly effective, lowering clostridial deaths by 23%. Zoetis veterinarian Dr Victoria Chapman unpacks the importance of robust animal health programmes, vaccination timing and the potential harmful consequences for stock when vaccination isn't given.
Bovine Viral Diarrhoea (BVD) is estimated to cost New Zealand's dairy and beef industries more than $150 million every year, yet many of the tools needed to control it are already well understood. After more than 25 years in veterinary practice, Andrew Weir, animal health technical specialist at LIC, has seen firsthand the impact BVD can have on herd performance. We asked him about the role of persistently infected (PI) animals and the practical steps farmers can take to reduce their risk.
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