Long Acting Dry Cow Therapies - What's in a name?

Put simply all antibiotic intramammaries which are registered as Dry Cow therapies are long acting when compared to lactational intramammories.

The registered claims for these Dry Cow preparations stretch from 4 weeks to 10 weeks.  Cepravin for example is registered for up to 10 weeks based on clinical trials measuring udder residues (which were conducted in the Northern Hemisphere (NH)).  As dry periods in the NH do not tend to last longer than 10 weeks this trial finished measurements at 10 weeks.  Udder residues at this point in the study still exceeded levels required to control Strep bacteria.

Five years ago our practice in conjunction with MSD looked at Cepravin residues in springer cows with 14 week dry periods and found the majority still had protective levels in the pre-colostrum secretions. This is why it is the only DC antibiotic in NZ that can show proof in reducing early season BMSCC. The downside of course is that it is also by far the most commonly detected inhibitory substance in the early season, thus Cepravin treated cows must adhere to withholding the first 8 milkings from supply.

In short, a successful dry off strategy should cover 3 aims:

• Cure existing infections
• Prevent new infections immediately post-dry off
• Stop the establishment of new infections close to calving (springer period).

As the average dry period in Otago/Canterbury is between 85 and 90 days, few products registered in NZ (e.g. Cepravin) will provide significant protection close to calving.  There is little advantage in investing in products that provide protection for more than 4 weeks but less than 10 weeks if the dry period is going to be greater than 10 weeks.  This is because very few new infections are picked up in the mid-part of the dry period (see image below). If protection close to calving is desired in cows with longer dry periods we recommend Teatsealants.

"Fog Fever" - Cow Deaths

From a mob of in-calf heifers grazing regrowth rape, 3 heifers were noticed with an unusual grunting cough.  Twenty four hours later, two of these heifers died.  Post mortem of these affected heifers showed unusual inflammation in the lungs.  This was confirmed by the lab to be "Acute Bovine Pulmonary Emphysema and Odema" or "Fog Fever" for short.  The third heifer was treated symptomatically but died 36 hours later. Fog Fever is a James Herriot era name and the disease probably has nothing to do with fog and more to do with the fact the disease is more commonly seen in the autumn.  A rapid change in feed (also a risk factor for Vitamin B1 Deficiency) causes a particular gut bacteria to convert L-Tryptophan, a naturally occurring amino acid, to a toxic compound.  The toxin rapidly impairs lung function resulting in death.  No treatment is available but identifying the condition and removing affected animals from the paddock will prevent any new cases.

Early Pregnancy Test Results

The key measures of optimal reproductive performance are the 6-week in-calf rate (ICR) and the final not-in-calf rate.  To achieve the industry target of a 78% 6-week ICR, you need >90% 21 days SR and >60% CR.

The 6 week ICR rates to date have been very variable, with the average 6 week ICR for our area, dropping around 4% to 63% compared to last season (15/16) which was 67% - remembering last season was also down on the 2014/15 season.  Many farms have seen a 5-10% drop this season in 6 week ICR.  With most farms now settling in on a 10-11 week mating period, we can expect empty rates to be once again higher than desired.  Many farms experienced a drop in Submission Rate (SR) this season, and some farms experienced an unexpected drop in Conception Rate (CR) as well - a number of farms' CR dropping 5-8%.

Yersinia

Each summer we investigate several cases of calves souring post weaning.  While there are many causes of diarrhoea in weaned calves i.e. parasitic enteritis, Salmonella, and BVD, we regularly diagnose Yersinia, which is a bacteria that causes diarrhoea.  We often see Yersinia 'roll' through a mob of calves - with a small number of calves being affected at any one time.  Treatment is aimed at correcting dehydration and administration of antibiotics.  Prognosis is usually good except in advanced cases.

There is circumstantial evidence that Yersinia is often associated with concurrent disease i.e. BVD, parasite burden, low trace element status - especially selenium and copper.  Remember - that Yersinia (both Y. pseudotuberculosis and Y. enterocolitica) are zoonotic - and hence are a common cause of food poisoning in people.  Keep the hygiene standards high if you are dealing with scouring animals!  Please contact the clinic if you are concerned about ill thrift or scouring in your weaned calves.

When lame cows get out of control

We are visiting a few farms at the moment where lame cow numbers have got out of control.  The smart money is on picking up a foot ASAP and correcting any lesions before they get too bad.  If lame cows are left they're likely to eat less, produce less milk, have lower repro rates, and ultimately have a greater risk of being culled.

On some farms, however, we are seeing lame cow mobs of 30-100+ cows.  By this stage farmers are struggling with time, and the problem often seems insurmountable. Human nature takes over, and so these cows are often left in a close paddock under the "wait and see" treatment regime, rather than being picked up and treated.  If you are in this boat, or want to avoid getting there then we have three options to help:

• Staff Training - we can come out and teach your staff members about how to treat lame cows.  This can help spread the workload across more people on farm.
• Vets to Treat - we can send out a team of vets (if available) to treat enough cows to get the mob down to a manageable level.  To enable multiple vets to work at a time these animals would need to be treated on the platform/herringbone (rather than a race).  Budget on a treatment rate of around 4-6 cows per hour (per vet).
• Healthy-Hoof Lame Cow Prevention Training - Andrew, Luke and Ryan are all trained Healthy Hoof providers and can come out on farm to teach staff about how their actions (i.e. gate use, animal handling) can increase or decrease lameness.  We have had some amazing results on farms following these courses, with dramatic reductions in lameness just from a change in staff attitude and knowledge around cow handling. A more in-depth package is also available looking at diagnosing track and shed issues that are having an influence.

The hidden costs of lameness can quickly mount up, and only get worse the longer they are left. Traditionally we've used an industry figure of around $200 per lame cow. However DairyNZ recently proposed a figure of $500 if you have to start taking cows out of the vat. If you think your lameness issues may be spiraling out of control then give one of our vets a call and we can work out how we can best help you get back on top of the situation.