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.

Polio Encephalomalacia (P.E.)

We are once again seeing several cases of P.E. (polio encephalomalacia), a nervous disease seen primarily in calves and younger stock.  P.E. is caused by a lack of vitamin B1 (not to be confused with a cobalt deficiency, which is associated with a vitamin B12 deficiency).  P.E. is thought to be nutritionally induced, when there is a sudden change in diet from stalky, higher DM diet, to a lush, low fibre diet.  A high dietary sulphur intake, especially with brassica's, has also been incriminated as a cause of P.E.

Calves with P.E. appear blind, may walk aimlessly, appear wobbly, have muscle tremors and head press.  If calves are treated early in the disease process with a series of vitamin B1 injections, survival rates are good.  In an outbreak situation we have had good success, by prophylactically treating the remaining, unaffected calves, in the group with an oral vitamin B1 drench.  This has proved a very cost effective preventative measure.

Healthy Hoof Update

Lame cows continue to be among the three main problems affecting farms in our area together with mastitis and reproduction.

Lameness figures on local farms range from 5-25%, but there is still a significant problem with under-recording of lameness and under-estimating its importance and control.

Early detection and treatment of lameness problems remains the best solution.  The Veterinary Centre has been running Healthy Hoof programmes on many farms with lameness issues this season.  Having staff trained by one of our vets so that they are competent and confident with lame cow treatments and understand the causes of lameness has made huge differences to lameness on these farms. 

An influx of lame cows over the Christmas and the New Year period will sound familiar to many farmers, these can be challenging to deal with as many farms go onto skeleton staff with public holidays and annual leave.

We ask you to be proactive if you are seeing an increase in the number of lameness cases.  Do not hesitate to organise a lameness consult with a member of our team.

How long should I mate for?

As we enter a new era without inductions we now have to think longer about how we manage our calving spread.

It is important to have as many cows calving as possible in the first three weeks of calving every season to ensure that cows have plenty of time to resume cycling before the next mating. Getting this right should also maximise your 'days in milk' which is one of the biggest drivers of farm profit.

The above graph from a local herd clearly illustrates the impact that calving date has on subsequent reproductive performance. The blue cows are those that had calved in the first 3 weeks and shows that they were also the fastest group at getting back in calf. If you have too bigger percentage of a herd calving down in the 3rd or 4th cycle it will have a major impact on future herd performance. A standard recommendation is not to let your calving spread go beyond 10 weeks to ensure late calving cows do not impact too greatly in the following mating. 10 weeks after a PSM date of the 23rd of October is the 1st of January. This would be the date for bull removal if you did not wish to have any cows calving beyond the 10th of October.

In some herds restricting the mating period to 10 weeks may result in an unacceptably high level of empties so make sure you fully understand the economic consequences of bull removal date on your farm (discuss with your vet or consultant).

A new strategy of doing AI for a short burst of 10days after the 1st of January with LIC short gestation semen would allow you to mate for a further 10days but still have all cows calved by the 10th of October. This strategy will potentially limit cow wastage.

Making the Most from Mating

With the loss of induction as a management tool for condensing calving spreads it has become more important than ever to get cows in calf early.  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 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.