An infection of a cow’s udder and mammary gland is called mastitis.
There is a tremendous amount of ongoing research into mastitis, often described by researchers as the most important economic disease of dairy cows, largely because of the negative effects that subclinical infections of the udder have on milk production.
Mastitis is often divided into two categories in cattle: environmental and contagious infections.
A cow’s habitat, including soil, plant material, manure, bedding and contaminated water, is the primary source of environmental mastitis pathogens. Exposure to environmental pathogens occurs primarily between milkings in dairy cows.
In some cases, environmental infections can cause sudden and severe systemic illness in the affected animal.
The mammary gland is the main source of contagious pathogens in a dairy herd.
Transmission of contagious bacteria to uninfected quarters and cows occurs primarily during the milking process. Milk from infected quarters can contaminate milking machines, milkers’ hands and towels, which spread the infections from cow to cow.
Most dairy producers know how to prevent both types of mastitis through environmental hygiene and preventing the spread.
Mastitis is far less common in beef cows but may still be a disease of some importance that often goes unnoticed.
A great deal of research on mastitis and subclinical mastitis in dairy cows has been performed, but the same cannot be said for beef cows. In the few studies that have been done, reports on prevalence of infection ranged from less than 10 percent to 37 percent of cows.
The bacteria that are isolated from beef cows are similar to those that affect dairy cows. One of the common contagious bacteria, Staphylococcus aureus, is one of the more frequent isolates found in beef cows.
Older cows are more commonly affected and most infections occur during the first month after calving. In most cases, only one quarter of the udder is infected.
The spread of the contagious infections from cow to cow is most likely the result of cross suckling by calves.
Cross suckling is thought to be a relatively rare event, but it does occur occasionally. Orphans and rejected calves are often seen suckling briefly from a number of cows opportunistically.
These cross-suckling events could spread the infectious bacteria from one cow’s udder to another.
Flies may be another significant way to spread the contagious pathogens from one cow to another.
Environmental infections can also occur in crowded or unhygienic conditions, especially in older cows with poor udder conformation.
Many of these mastitis infections may show no clinical symptoms, depending on the bacteria involved.
Some environmental infections may result in a swollen quarter and may eventually result in a dry quarter if untreated.
In rare cases, environmental infections can result in severe clinical disease, which causes the animal to be severely depressed, off their feed and have an extremely swollen quarter. These animals rapidly go into shock, become severely dehydrated and can die if left untreated.
Treating beef cows with clinical mastitis may require systemic antibiotics as well as anti-inflammatory drugs. Severe clinical cases may require fluids and other supportive care. I
ntra-mammary antibiotic suspensions also work in some instances. The cow should become a candidate for culling if the quarter has atrophied and dried up.
A calf’s growth rate is largely de-pendent on its dam’s milk production. Almost 60 percent of the variation in weaning weights is related to the cow’s milk production.
Studies have shown that the weaning weights of calves suckling cows with subclinical mastitis are seven to 12.5 percent lower than calves suckling non-infected cows.
The loss of a quarter can also cause significant decreases in a cow’s ability to feed an older calf and can significantly reduce weaning weights.
The methods for preventing mastitis in beef cows have not been as well researched as in dairy cows.
Fly control is important, and culling cows with atrophied quarters and poor udder conformation may be of some benefit.
Avoiding overcrowding at calving time and having cows calve in hygienic conditions will help prevent environmental infections.
Antibiotic treatments in cows at weaning time have not been shown to be of benefit in preventing beef cow mastitis.
Maintaining your cows’ body condition and keeping them in good nutritional status will help maximize immunity and lower the risks of beef cows contracting mastitis.
John Campbell is head of Large Animal Clinical Sciences at the University of Saskatchewan’s Western College of Veterinary Medicine.