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?

Lungworm - The Perfect Storm

Vets from our Waimate clinic were recently called to a farm where 4 calves had died, one calf was recumbent, and about 40 others showed signs of coughing and respiratory distress.  The history was consistent with lungworm, and this was subsequently confirmed on postmortem (see photo below) where large numbers of adult worms were present in the large airways of the calf.  We rarely see clinical lungworm cases, but this case saw a perfect storm; wet weather, long drenching intervals, and calves on the same paddocks for multiple years.

The lungworm lifecycle, much like gastrointestinal worms, revolves around the ingestion of L3 larvae from pasture.  Grazing paddocks which have previously held calves (as in this case) will obviously increase the risk of infection.  However L3's from lungworm are relatively inactive compared to their gastrointestinal cousins, and are incapable of traveling more than 5cm from the cow pats they are carried in.  Instead they rely primarily on a mushroom (P klenii) which grows in the cow pats and bursts to disperse the larvae as far as 3m.  The recent wet warm weather has been perfect mushroom weather, and has therefore increased the risk of lungworm.

A routine drenching programme normally limits lungworm as they are highly susceptible to anthelmintics.  In particular pour-on abamectin compounds (such as Eclipse) have a persistence efficacy of over 14 days.  In this case, in an effort to reduce costs the farmer used an oral abamectin/levamisole drench 8 weeks apart.  We traditionally recommend 4 weeks between oral drenches and up to 6 weeks for pour-on products at this time of year.

This case highlights the need to be aware of drenching intervals in young stock, particularly with the warm, wet weather we were experiencing.  As in all diseases prevention is much better than cure.  In this case the farmer has lost 4 calves, has another 40 severely compromised, and the whole mob will have reduced growth rates - severely outweighing the cost of an extra drench.  Talk to your Prime Vet about a Young Stock Health Plan if you don't already have one in place.