LIC Chief Says BVD Eradication in NZ Is Within Reach
A dairy industry leader believes eradicating the common and costly disease, Bovine Viral Diarrhoea (BVD) is within reach.
This may be so and you may not be getting grades, but there are still many financial advantages to maintaining a low cell count.
Apart from the obvious advantage of less veterinary care and antibiotics for uninfected cows, infected quarters produce less milk.
DairyNZ's farm fact sheet, 3-10 Somatic Cell Counts, says that cows with high somatic cell counts usually produce less milk than those with lower counts (up to 8kgMS/lactation for every increase of 250,000 cells/ml in the range 100,000-600,000).
Most mastitis problems are either calving related environmental problems, characterised by a high number of clinical cases in the spring, and/or contagion which usually results in a rising cell count later in the season.
The contagious form of bacteria is Staphylococcus aureus which is easily transmitted from cow to cow via milkers' hands and liners, so as the season progresses the number of infected cows goes up.
Some good tips for keeping this form of bacteria at bay are:
• Teat spray every teat, every day and every milking
• Wear milking gloves
• Avoid hosing down around cows when cups are off
• Where possible, milk high cell-count cows at the end of the milking.
Keeping a low cell count in the autumn can be difficult because as volume drops cells become less diluted and cell count rises. There is no benefit to treating high cell-count cows in late lactation; they should be dried-off early and treated with dry cow therapy.
Some chronically infected cows cannot be cured. These are cows which have had three or more cases of clinical mastitis during the season, and cows which have been high over consecutive seasons despite using dry cow therapy. They should be considered as culls and removed from the herd. Herd testing will provide this essential information and is an easy and accurate way to identify cows for dry cow treatment and possible culls.
The drying-off process requires good management in order to mitigate mastitis issues arising the following season. If the herd is producing more than 10L/cow/day at drying-off, feed supply will need to be actively managed to help the process.
This can be a balancing act as too much feed will make it difficult to dry off and too much restriction can result in stress, downer cows and weight loss.
Low protein feeds such as maize, hay or straw can be put to good use to reduce milk volume. Alternatively, reducing feed intake to 66% of the milking diet for around three days will produce the same effect.
Metabolic problems at drying-off can be mitigated by provision of magnesium and calcium. It is important not to restrict cows' water intake over this period.
Strategies to combat mastitis in the herd are a complex issue. Every situation is slightly different and on any given farm many factors will affect the outcomes.
Consult annually with your vet: explain your particular situation and help choose which treatment or dry cow therapy approach will suit your farming practice.
• Phil Fleming is FarmWise consultant.
