Making the Most from Mating

Recommended mating lengths of 10 weeks are considered optimal to ensure all cows are calved by the 10th of October (if the PSM was the 23rd of October) to retain a healthy calving spread.  In this scenario a 10 week mating period would have bull removal occurring on the 1st of January.

The number of lactation days is one of the key economic drivers of your farms profitability.  Therefore success of mating should be measured in how quickly they get in calf (3 and 6 week in-calf rate) as well as the empty rate.  The reality of a 10 week mating period is that cows have just over 3 cycles to get back in calf.  The average cow has a ~50% chance of getting in calf at each cycle.  If given every opportunity she would have a 12.5% chance of being empty after 3 cycles.  However if she was to miss the first round of AI she will have a 25% chance of being empty.  Likewise if a heat is missed in the second round she has a 50% chance of being empty!

If your 3 week submission rate is tracking below the >90% target, review your heat detection practices immediately and look to get non-cyclers examined and treated.  Ideally all eligible non-cyclers (calved >40 days) should be mated inside of 3 weeks.  This involves hormonal treatment by day 11 of mating at the latest.  Failure to take proactive action will result in not only a protracted calving spread but also a higher empty rate.

All eligible cows not mated after day 24 of mating should also be examined and treated accordingly.

It is bloat season again....

A large number of farms have experienced deaths from bloat in the last week.  This has coincided with the introduction of high protein, low fibre second round pasture which generally has an increased clover content.

Risk factors for bloat:

• Swards where clover content is greater than 30%.
• Dew on grass at morning shift.
• Short swards.
• Warm windy conditions especially in the evenings.
• Young cows.
• Potassium to sodium ratios in pasture greater than 20 (this can easily be tested for at Feed Labs - known as the bloat index).

Factors which will reduce bloat risk include:

• Feeding longer length pasture.
• Feeding long chopped silage, hay or straw before introduction to a new paddock or break.
• Preferentially grazing older cattle (older herd) on at risk pastures - older cows have adpated grazing behaviour i.e. they do not gorge themselves.
• Feeding salt at 30gm per cow per day.

Rumensin bloat capsules should be considered in situations where dosatron type systems are not available or peta trough dispensers are not practical.  Alternatively if a dostron is available use Rumensin TT or Bloatenz Plus.  Rumensin products have been shown to reduce the risk of bloat by 80%, plus they give the added benefit of extra milk production.

High Coccidiosis Risk in Calves

In moist and cool conditions coccidia may survive for up to two years on pasture.  We have now had three favourable seasons in a row for coccidia survival and farms with dedicated calf rearing paddocks are at high risk.  Calves are typically greater than 3-4 weeks of age and present with a bloody diarrhoea which may contain gut lining.  The tail area is often smeared with this bloody diarrhoea.  Calves appear very uncomfortable and will be seen straining with tails held in the air.  A metallic sheen may also appear on the surface of faeces after a couple of hours.  In severe cases up to 10% deaths can occur due to anaemia and dehydration and growth checks in survivors may remain for many months.

Calf meals which contain coccidiostats are only protective once calves are ingesting about 1kg/day.  If treating/preventing an outbreak we recommend Deccox for at least four weeks, starting 2-3 weeks after being on pasture or Baycox C as s singular oral dose 3 weeks after being on pasture.  Amphoprim can be used in severely affected animals as it also gives anti-bacterial protection.

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.