Dropped Hock Outbreak

Over the last month we have seen an outbreak of an uncommon condition called dropped hock or sciatic palsy on one of our dairy farms.  This is a new condition of unknown cause that has only been recognised in New Zealand since 2011.  It affects rising 2 or rising 3 year old animals just prior to calving.  In this case they were all rising 2 year olds.  The heifers go from having a mild shifting hind limb lameness through to some animals being unable to stand because their hocks remain on the ground.  This happens when the muscle in their leg ruptures.  This is the first time our practice has seen an outbreak of the disease, but we have seen the odd individual with similar signs in the past.  In this outbreak there have been 22 animals affected.  Not all heifers go on to have hocks that touch the ground, but some have had to be euthanased.  Interestingly all the heifers tested have had very low copper levels.  While it is currently unknown what the exact cause is, there is a suspicion that inadequate copper supplementation is part of the problem.  Copper is crucial to the formation of collagen which makes tendons in animals.  There is also a suspicion that this condition is related to the humeral fractures that we have been seeing in recent years.

If you see any heifers with this condition or think they have this condition contact the Veterinary Centre.  It is also import to ensure that adequate copper supplementation is going into your young stock.

Rotavirus Scours

Now is the time to start considering the protection of this season's calves against Rotavirus scours.  As we know, Rotavirus is the most common causeof infectious diarrhoea in young neonatal calves - and is easily spread from calf to calf by contaminated faeces in the calf pen.  Successful calf rearing can be a real challenge, especially in the large herd situation.  Overcrowding in sheds, especially in wet/cold weather, damp sheds, poor colostral transfer and overstretched staff can allow an environment for the proliferation of bugs that cause infectious diarrhoea i.e. Rotavirus, Salmonella, coccidia.

Prevention of Rotavirus is a sound investment to protect your calves and their welfare.  The vaccine Rotavec Corona is administered to the pregnant cow as a single shot between 3 and 12 weeks prior to calving.  Therefore a herd should be vaccinated 3 weeks before the PSC to cover a 9 week calving spread.

A second option for cows which have already been vaccinated in previous years with Rotavec, is to boost these cows with Kolibin Neo, a new vaccine from AgriHealth.  Kolibin Neo provides protection against the prevalent and NZ relevant rotavirus serotypes.  Kolibin Neo has sound trial work, can be administered 2-12 weeks prior to calving, and offers a cost saving when used as a booster vaccine.  If Kolibin Neo is used in previously unvaccinated cows, the cow will need two vaccinations in her first year.  Therefore the net cost in year one is slightly more than a single vaccination of Rotavec.

Fodder Beet Over the Dry Period

Fodder beet is now becoming the mainstay crop for wintering cows in our area.  Many cows have been pre-transitioned onto this crop while on the milking platform but some of you will be putting cows on the crop for the first time at the start of June.  Follow these steps to avoid hassles:

• Measure your yield accurately - once you know the yield/ha (i.e. 25 tonne/ha crop), you can calculate your yield per square (two rows per metre square) and yield per linear row metre this would be 2.5kgDM/m2 and 1.25kgDM/linear row metre respectively.
• Allow at least 1 linear metre/cow at the crop face and at least 5m2 of turning room in the first break.
• Either drop wires on the permanent fence in the first break to allow a bigger area or scrape bulbs with a front end loader (and feed in paddock or stock pile) to create a headland.
• Best to calculate allocation in linear metres to be fed - i.e. if offering 3kg a cow from a 30 tonne crop this would be 2 linear metres or 1 square metre/cow.  To be accurate you will have to offer part rows - i.e. your live strand will have a dog leg in it at some point.
• Cows will comfortably graze 18 inches under a single strand wire.  Make sure that the wire sits back 12 inches from the row you are looking to graze.  It must be very high voltage!
• Always feed your supplement or grass first and give a gap of 2 hours before shifting onto break.  Cows must get a minimum of 2kgDM of "something chewy" in their diet.  This may be either straw, balage, silage or grass and must be maintained through the whole period while on fodder beet.
• For the first couple of days, drive over bulbs with tractor tyres or roller to break up bulbs to get cow eating it.
• Start at 1kgDM/day and increase intakes by 1kgDM every second day until fully transitioned (7kgDM).  This take a minimum of 14 days.  Once cows have reached intakes of 7kgDM FB they are unlikely to suffer acidosis but further intakes up to 10-11kgDM total (ad-lib) must still occur at 1kg every second day.
• If you are going to get acidosis this will tend to occur at days 7-10!!  It is critical to remain restrained with allocation over this time.  Do not let beet bulbs accumulate while still shifting breaks forward.
• Once cows have got over 10kgDM/day and looking to ad-lib feed there should be 20-25% of beet left from the previous day when shifting wire and about 5% from the previous day before that.  Cows will always eventually clean this up.  This is the true definition of ad-lib on beet.
• With a high ME and utilisation at around 95%, condition gain on fodder beet can be rapid.  Monitor cow condition (BCS) to avoid them becoming over-fat as this can predispose them to metabolic diseases in the spring.  Ensure you are not feeding more than required!

Teatsealants as a Mastitis Preventative at Dry Off

The use of antibiotics in agriculture will continue to come under increasing pressure.  The World Health Organisation has concerns about the use of antibiotics in animals and the risk of antimicrobial resistance transferring into the human population.  Dry cow antibiotic preparations have become an area of significant scrutiny.  Already dairy farms in some European Countries can not use antibiotic dry cow preparations unless the individual cow can be demonstrated to have an infection - i.e. a high SCC from a herd test.

We have had many farms last season that took the step to use Teatseal only in cows with herd test SCCs consistently below 150,000 for the season.  When administered hygienically Teatseal will significantly reduce the risk of picking up new infections at dry off and close to calving.

In the graph below from a local farm, clinical mastitis cases have been recorded from cows which either received Teatseal or Antibiotic Dry Cow Therapy.  Those that received DCT (not Teatsealed) had a higher rate of mastitis in the following season, but it must be remembered that being high SCC cows they have more risk factors for picking up new infections in the next season.  The Teatseal treated cows had extremely low levels of recorded clinical mastitis in the first 2 months of lactation.

Setting Your Herd and Your Farm Up for Ease and Low Cost Next Season

We are having regular conversations with our clients around dry cow strategies.  Cost reduction is at the forefront of everyone's minds at the moment but it is important that a plan is implemented that will not severely compromise milk quality, clinical mastitis and put additional pressure on the farm team next winter/spring.

An extreme case example from last season was a local farm that had used whole herd Cepravin in the previous year, maintained a BMSCC under 100,000 for the whole season and so elected not use DCT therapy in any cows at the end of last season.  Subsequently the equivalent of 25% of the herd was treated for clinical mastitis over the dry period, meaning the shed could not be shut down.  Over the ensuing 10 months, the equivalent of 100% of the herd has been treated for clinical mastitis.  The result has been massive cost and massive stress.

All cows - even low cell count cows, are at risk of developing mastitis post-dry off if the correct preventative measures are not taken.

Our advice would be to ensure every teat is treated.  If budget constraints are tight and you are considering treating just a few high risk cows with long acting products e.g. Cepravin, we would suggest that you would be better to spend the same amount on more cows with short acting products (or sealants).

Important Considerations

• Know what the risks and benefits are of the therapy/sealant you choose; actives, formulations, length of action and spectrum of activity are highly variable between products.
• Will you have less staff available in the shed next season if things go wrong?
• What will the environmental challenge be like for your herd over the winter/spring?
• Is your BMSCC climbing or higher than you are comfortable with?