The Impact of Mastitis on Dairy Goats.

 By Jennifer Bentley - Iowa State University Extension and Outreach Dairy Field Specialist.

 Mastitis is an inflammatory condition of the mammary gland (udder) and can play a significant role in a dairy goat’s health and longevity in the herd. Not only does mastitis impact the dairy goat, but also the dairy goat producer’s income. Mastitis can directly reduce farm income through decreased milk production and cost of treatment. It can also indirectly impact the farm when factors such as time and labor to treat clinical cases, long-term decreases in production, culling and replacement costs, and loss of milk quality bonuses are considered.

Mastitis develops when bacteria gain access to the udder, via the teat canal. The teat end can be damaged because of over milking, poorly maintained milking equipment, how the clusters are removed during milking, getting teats caught on brambles or wire or because of teat biting. Other factors which may increase the incidence of mastitis include general sanitation both in the parlor and where the goats are housed and milking procedure protocols.

Signs of mastitis can include a decrease in milk production, changes in milk color and texture, and lameness. If kids are nursing, they appear to be hungry or kid mortality increases. The udder shape is another sign of mastitis. A swollen udder that is hot, reddened, and painful to touch may be an indication of an acute infection. A withered udder may be firm and show no signs of pain but may be an indication of a chronic infection. General illness symptoms can occur such as depression, fever, or loss of appetite.

Proper diagnosis using a combination of signs and symptoms the doe is expressing, taking a bacterial culture to determine pathogen, and reviewing somatic cell count (SCC) will aid in a more immediate action of a mastitis problem. Somatic cells are leukocytes (white blood cells per mL of milk) which increase in numbers to help fight off germs and often indicate the severity of the infection. Dairy goats generally have a higher somatic cell count than dairy cattle and so the interpretation is a little more complex. Other factors such as stage of lactation and breed need to be considered for the dairy goat when reviewing SCC. Finding the cause of mastitis on your farm will reap the most reward both productively and financially.

Contagious mastitis occurs when microorganisms (germs), live in the udder of sick does and are highly contagious during milking to healthy does. It is mainly due to organisms Streptococcus agalactiae, Staphyloccocus aureus, and Mycoplasma.  Often, contagious mastitis can be spread through milking equipment due to poor hygiene or post milking procedures. Good milking hygiene using clean or disposable gloves and use of a pre or post dip, can help minimize the risk of infection and spread of disease. According to the 2019 NAHMS Goat Study on Milking Procedures and Milk Quality on U.S. Dairy Goat Operations1, milking protocols that were implemented included by dairy goat producers included: using disposable gloves (17.7%), washing teats before milking (76.3%), using pre-dip on teats (11%), fore stripping does (76%), drying teats with a single use cloth/paper towel (33%), and using a post-milking teat disinfection (63%). Liner slips should be avoided to reduce the introduction of pathogens being pushed in with outside air. A routine milking equipment maintenance program will go a long way in preventing contagious mastitis. While bringing does in for milking, regular inspection of udders is very important to catch any signs of swelling. Separating known infected animals and milking them last will help reduce transmission. Culling may be the best option for chronic mastitis cases or cases that have been identified as untreatable. Identifying contagious mastitis early will be beneficial to keeping the problem from growing quickly.

Environmental mastitis occurs when microorganisms live in the environment, waiting to enter a doe’s udder through the teat canal, causing damage to the milk-producing tissue. These germs can be found in the bedding, manure, and soil. They include organisms namely: Coagulase negative Staphylococcus spp., E. coli, Klebsiella, Pseudomonas spp., Streptococcus spp., and Bacillus spp. Inspect the does coming into the milking area for cleanliness, making sure to wash and dry udders if needed. If does are noticeably dirty, then housing and bedding should be inspected, making sure they have clean, dry bedding and pens are not overcrowded. This should be done regularly as the weather elements change and the need to respond to increasing or removing dirty bedding is critical.  

Best management practices for managing mastitis:
• Identify the bacteria causing the mastitis using culturing to determine if it is coming from the environment or spread from doe to doe. Once identified, an appropriate treatment plan and control measures can be implemented effectively. Antibiotic treatment plans should be reviewed with your veterinarian.

• Evaluate the genetics of the herd. Can improvements be made in genetic selection to improve udder attachment, teat placement, and other udder health traits?

• Monitor somatic cell count, taking into consideration non-infectious factors that increase SCC in goats (estrus, parity, stage of lactation, stress). The current recommendation is to perform somatic cell evaluations on each individual animal every 3-4 weeks throughout the lactation. This can be accomplished through routine Dairy Herd Improvement (DHI) testing which aligns with the American Dairy Goat Association’s Dairy Herd Improvement Registry (DHIR). Producers may elect to have a full-service test done monthly by a DHI-certified testing supervisor or can self-submit samples depending on whether they participate in the DHIR program. Regardless of sample collection method, DHI provides producers with electronic records of each test day’s data which allows tracking of individual animal and whole-herd data throughout the year. This is the most effective method of evaluating trends in somatic cell counts as well as milk production and component levels. Not only is this valuable for detecting subclinical mastitis events but it can also assist producers in management decisions based on other production metrics.

• Whatever record-keeping system is used, it’s important to track the name/number of the doe, affected teat, dates and duration of the infection, type of treatment, length of withdrawal period, and outcome of the treatment. This will be beneficial in having conversations when reviewing issues or trends with your farm and veterinarian.

• Each farm will be different in selecting which does to cull. These decisions are based on economic factors, emotional ties, and pedigree of the animal.

According to the 2019 NAHMS Goat Study on Milking Procedures and Milk Quality on U.S. Dairy Goat Operations, dry-off management practices included skipping milking before completely drying off (88.7%), utilizing the California Mastitis Test or other individual-doe SCC test (5.4%), reducing the quality/energy content of feed (55%), reducing access to feed (31.4%) and water (2%), treating any does at dry-off with intramammary antibiotics (21.1%), and using an internal or external teat sealant (6.5%).

Milk procedures and management can vary widely in dairy goat herds depending on size, type of milking system, breed, genetics, and overall goals of the operation. What is common is that mastitis can be a costly disease, both financially and productively to any dairy goat farm. Implement best management practices including milking routines, milk quality testing, and dry-off procedures, culling and treatment decisions, and record-keeping will help improve the health and quality of milk being produced.  

https://www.aphis.usda.gov/animal_health/nahms/goats/downloads/goat19/go...