1999 March

The Dry Period, Dry Cow Therapy and Culling

After each lactation, dairy cows require a dry period which is sufficiently long to allow the udder tissue to repair and rejuvenate. Many of the milk producing cells are removed and replaced again before the next calving. Areas of damage are repaired, and this period provides us with the best opportunity to remove chronic udder infections by using dry cow antibiotics. Culling can be used at this time to remove the cows that have irreparably damaged udders and those that are unlikely to be cured of udder infections.

The dry period can be thought of as a factory shut down and refit. The worn out and damaged tissues are repaired and replaced. As this process requires approximately six weeks to be completed, ideally cows should be provided with a minimum of six and preferably eight weeks from dry-off to calving.

Dry cow therapy (DCT) has been a crucial part of mastitis control for over a decade. The intent of dry cow therapy is to administer high doses of antibiotics into the udder that persist for the much of the dry period (20 to 70 days depending on the preparation) and kill mastitis bacteria. The prolonged time of exposure to antibiotic and the formulation enhance penetration and give an increased chance of curing infections embedded deep in the udder. Dry cow therapy has also been shown to reduce the number of infections developed during the dry period by promoting the formation of the keratin plug that seals the teat canal.

Over the years different dry cow therapy programs have been promoted. There are two basic programs, Strategic and Blanket DCT. A guide to assist you determine how you treat your herd is available here. Selective DCT only treats selected cows with dry cow antibiotics. The cows that are treated are the ones that have the greatest likelihood of being infected, for instance cows with a cell count above 250,000 and cows that have been treated for clinical mastitis. Strategic therapy works well when the level of infection in the herd is low and the risk of cows acquiring new mastitis infections is low. Blanket Therapy involves treating all cows in the herd, irrespective of their infection status.

Traditionally blanket therapy has been advocated in herds that have a high BMCC and/or high rate of clinical mastitis. However, many farmers with very low rates of mastitis have decided to continue to blanket treat their herd, thereby keeping the level of mastitis low. A majority of the recipients of last years VDIA Milk Quality and Cell Count awards used blanket dry cow therapy and attributed some of their success to this policy. Further, recent research from Holland has shown that the farms that repeatably produced low cell count milk treated all cows in their herds with dry cow antibiotics at drying off and had done so for a number of years.

Culling cows for mastitis and high cell count can be the only way of eliminating chronic infections from the farm. However, it comes at the cost. Culling cows with chronic infections helps protect the healthy, young cows which are the future of the herd. Culling alone seldom solves farm mastitis problems. Failure to prevent new infections will mean that other cows take their place at the top of the mastitis culling list. Culling should be reserved for removing cows from the herd who are unlikely to be cured by other means, or who are going to be a continual problem.

Cows that should be considered for culling include:

  • Older high cell count cows
  • Cows that have had three or more cases of mastitis
  • Cows with high cell counts for two consecutive lactations
  • Cows with damaged or deformed udders
Please contact the clinic if you require assistance in selecting an appropriate dry cow therapy and culling program.

 


back to top

Ryegrass Staggers

Seasonal conditions over the past few weeks have resulted in a large number of reports of ryegrass staggers throughout the district.

Animals affected:

  • Cattle, predominantly calves and yearlings.
  • Sheep, adults and weaners
  • Alpacas
  • Horses, very occasionally
Signs Observed: (more than one animal in the group will be affected)
  • Head movements, usually weaving from side to side.
  • Stiff legged gait noticeable, particularly in the front legs.
  • The signs are exacerbated with movement. Often animals are almost normal until they are driven when the "proppy" gait is noticeable.
  • Eventually they may fall over and while struggling are unable to rise.
  • If left alone, most animals will eventually get up.
Cause:
Rye grass staggers is caused by a toxin associated with a fungus called an endophyte that lives in the ryegrass plant. There is a positive correlation between plant yield and presence of endophyte, so that newer varieties of ryegrass that have higher dry matter yields tend to have more endophyte than some of the older varieties.
Management:
The toxin is very rarely fatal and most deaths occur due to misadventure eg. affected calf drowns in mud on a dam bank. There is no specific treatment. Like any poisoning, the logical approach is to remove the animals from the source of the toxin.

If animals are removed to an unaffected pasture, the signs will disappear in a few days to weeks. Alternatively, reducing the intake of pasture by feeding hay, silage or grain will reduce the severity of signs.


back to top

Guaranteeing Successful Pasture Renovation

A recent visit by Peter Notman to Western Victoria once again highlighted the keys to successful autumn pasture sowing. Many farmers will struggle to establish new pastures well enough by the end of autumn resulting in a battle to survive a typical wet winter. Apart from a late break or an exceptionally wet winter, the cause of this will be entirely due to the farmer who has total control over the sowing of these paddocks.

A good target to aim for is four three weekly grazings from these new pastures by 1st July. To achieve this with the first grazing being seven weeks after sowing, the deadline for sowing is mid March. This year the below average yield of turnip crops has resulted in most crop paddocks being ready for resowing early. By early March there is nothing to be gained by delaying sowing.

As Peter Notman says ".... the seasonal conditions in Western Victoria during March are such that any perennial or annual seed sown in early March will survive an early strike except in the lightest of soils. A delay in sowing will have a marked reduction in first season yields and accentuated pugging problems in winter."

Farmers offer many excuses (not reasons) for not having sown their bare paddocks in early March

  • It's too dry
  • I'm waiting for the break
  • I've done OK with later sowings in other years (that's alright in a dry winter)
  • The contractor has let me down
  • I'm too busy
  • The seed is not purchased yet
  • I haven't decided what to do yet
Let's not have any of these excuses as reasons why this year's new pastures have not worked as well as the best.

A few key pointers that Peter Notman reiterated were:

  • It is essential to have adequate bed preparation. Clods of dirt or root material bigger than a golf ball are unacceptable.
  • Remove all weeds with broadleafs or glyphosate before preparation.
  • Apply lime if required (up to 5 tonne per hectare on acid soils)
  • Ensure adequate soil fertility (up to 60kg P on soils with Olsen P <20).
  • Spread seed evenly. Dropping to the surface using a seed box is the most effective.
  • Ensure adequate seed is sown (25 to 30kg per hectare of perennials or annuals).
  • Roll with a heavy roller to maximise seed soil contact. This allows better and quicker germination to beat competition such as winter grass.
  • Effective control of broadleafs with sprays such as Tigrex at 300-400ml per hectare at 5-6 weeks after sowing.
  • Aim to graze by 7 weeks or at a maximum of 8cm if pastures pass the pluck test. This is important to maximise pasture establishment.
  • Use insecticides to control earth mite and lucerne flea on newly established clover based pastures.
  • Use light doses of urea after the first grazing to promote early growth and tillering (20kg N).

back to top