Some 450 delegates attended a programme of 36 presentations over two days at the Total Dairy Seminar on 19 and 20 June 2019. The various parts of the dairy industry attended with an active exhibition area and posters covering a wide range of research and analysis. Veterinary surgeons were able to discuss aspects of cow management and nutrition beyond the obvious areas of veterinary involvement and there was a positive buzz of activity throughout the event/
Chris Hudson, Clinical Associate Professor in Dairy Health and Production at the University of Nottingham, reviewed the changes that have taken place in the recognition of pain with cattle herds. There was interaction with the audience throughout, with responses to key questions recorded on screen and compared to other group observations. In general, the groups of veterinary surgeons, farmers, industry representatives and mixed workshops demonstrated a level of agreement. Fundamentally, cows and calves do feel pain; pain does increase the period of recovery; and reducing pain speeds up recovery. However, it is difficult to demonstrate the benefits of pain relief in commercial terms.
With calf disbudding, it is accepted that the farmer now feels better after using non-steroidal anti-inflammatories (NSAIDs) and sees their use as an improvement in animal welfare. This approach has changed considerably over the years and administering NSAIDs before disbudding is now considered common practice.
Studies with clinical mastitis indicate that controlling pain, together with antibiotics, has not only led to a more rapid recovery but tangible benefits including reduced cell count, less culling and improved conception rate. It has been shown that using NSAIDs in cows with mastitis can lead to the cow behaving subsequently as though she never had the disease.
It was also mentioned that NSAIDs have a short duration of activity and cases of lameness often persist for weeks. The combination of hoof trim, hoof block and pain relief has been shown to be more beneficial than any one procedure alone.
Considering welfare with mastitis
Jim Reynolds, a professor in large animal medicine at Western University California, explained the factors related to the welfare aspects of bovine mastitis. When using NSAIDs, tissue damage releases prostaglandins, which are potent activators of inflammation and lead to lower pain receptor thresholds. NSAIDs block prostaglandin production in tissues; inflammation is reduced and blood flow activity is normalised; white blood cell activity is maintained; and pain receptor thresholds return to normal.
With experimental E. coli infections, NSAIDs have been shown to reduce fever, reduce heart and respiratory rates and improve rumen function. Lipopolysaccharides in the cell walls of Gram-negative bacteria are extremely immunogenic and stimulate a strong immune response in local tissues, with a reaction from the cow delivering a massive white blood cell release into the mammary gland. The white blood cells release immunochemicals that damage tissue and affect blood flow. The amount of lipopolysaccharide released from the bacteria determines the severity of toxic shock that is experienced, from mild to fatal. Vaccinated cows have been shown to react to Gram-negative infections more rapidly and the bacteria are killed before effective volumes of endotoxin are produced, but can be overwhelmed by a large infectious dose.
Jim emphasised the benefits of handling cows so as to reduce stress. Cows need to be calm. Noise or quick movements can scare cows and stop the production of oxytocin, due to the release of epinephrine when a cow is nervous. Blocking the production of oxytocin decreases the immune system, inhibits milk let-down and increases the risk of mastitis.
Behavioural changes are noted with cattle in pain, including: inappetance, decreased water consumption, decreased milk production, depression with increased lying and vocalisation. Cattle are stoic and do not show the impact of pain readily, so when signs are noted, action needs to be taken to reduce the pain at the earliest opportunity.
Non-aureus staphylococci mastitis
Sarne De Vliegher, a professor at Ghent University, is editor of M2 magazine (Rekad Publishing) and, in introducing his involvement with non-aureus staphylococci mastitis, referred to the identification of a new Streptococcus species high-lighted in 2018. Streptococcus bovimastitidis was identified from a milk sample by genome sequencing from one farm in New Zealand. Unfortunately, the organism has not been identified again, even from samples taken on the same farm. If anyone can contribute to the hunt for the new species, which has a similar presentation to Streptococcus uberis, please contact the university.
Non-aureus staphylococci (NAS) are the principal cause of culture-positive milk samples around the world. There are 50 different species and sub-species of NAS, with five typically found in milk samples. Each herd has its own population of NAS and, as commensals, are considered to prevent clinical mastitis.
The organisms can be found surviving on the udder and in the environment as well as within the mammary gland and they can shift between habitats. Bacterial shedding takes place in faeces with colonisation of the teats and the udder. Teat apex colonisation stimulates higher neutrophils, which provide protection against other bacterial invasion. Cows infected with coagulase-negative staphylococci produce as much milk as non-infected cows, but with a raised cell count. Studies have shown that a pre-existing NAS infection after calving shows a reduced incidence of pathogens during lactation.
Antimicrobial resistance is prevalent with NAS but treatment with antibiotics is rarely indicated. One of the many research questions is whether NAS drug resistance is transferable to other bacteria. Other milk producers can also be affected and goats have been shown to have a higher somatic cell count and milk yield than non-infected animals. The speaker said it needs to be recognised that there are many differences between and within NAS species. The overall view is that NAS are not a problem for udder health, except in herds where major pathogens are minimal and more “virulent” NAS species are involved.
Sarne provided an update on heifer mastitis. Heifers can become infected at 9 to 10 months of age and up to calving. A herd is considered to be a heifer mastitis problem herd if more than 15 percent of heifers have mastitis around calving or if more than 15 percent of heifers have a first test day somatic cell count (between 10 and 35 days in milk) of over 150,000 cells per ml. Cleanliness, fly control, transition feeding, nutritional deficiency, optimal per partum feeding management and the avoidance of cross suckling are included in a management plan.
Antibiotics administered intramammarily before calving, in the face of an outbreak, have been shown to be effective. External teat sealants have traditionally been applied to reduce the effect of flies and the administration of internal teat sealants is under investigation. During the discussion, it was indicated that antibiotics can be administered to pre-calving heifers without inserting the syringe nozzle into the teat canal, but it was not known whether the same technique would work with teat sealant products.
In general, the heifers are an important economic resource and mastitis can be a considerable problem ranging from total loss of an animal to reduced yield in the first lactation. The location of heifers in distant pasture has been a problem with mastitis only being detected around calving. Managing the heifers as a valued resource is required to combat heifer mastitis. The administration of dry cow minerals has been shown to improve the quality and quantity of neutrophils in the milk of heifers.