Yersinosis in Calves

Yersiniosis frequently rears its head in the months of December through to May in calves of 4-10 months of age. Calves with the disease suffer a chronic scour, elevated temperature, loss of appetite and weight loss. It is caused by the bacteria Yersinia pseudotuberculosis, which can be found in the gut in over 85% of herds of yearling heifers around the country and up to 60% of individuals. Although it is commonly found in the gut of healthy calves, an overgrowth of the bacteria and invasion of the gut lining results in millions of micro-abscesses throughout the length of the intestines.

Conditions which may precipitate an overgrowth in the gut are low levels of the trace elements copper and selenium, parasitism, BVD, long transport, poor feed quality or feed stress.

Once an outbreak starts, an insidious spread through a mob of calves occurs via the faecal-oral route.

Control and treatment comprise the removal of affected animals and use of appropriate antibiotic. Further prevention should focus on the underlying risk factors – correction of trace mineral status, drenching and increasing feed allocation. We have seen a lot of success with the use of Multimin injection.

There is a registered Yersinia vaccine available for deer. This has been used off-label in cattle but can result in anaphylactic reaction. We have a limited number of clients that have used a single dose of this vaccine with apparent protection inferred. You would need to talk with your prime vet about the pros and cons of using this product off-label.

Correctly Identifying the Lame Claw

Over the years I have witnessed multiple occasions where farm staff have attacked hooves with knives, grinders and hoof trimmers before correctly determining the site of lameness. This will have frequently resulted in an exacerbation of the overall lameness in the cow.

Before putting any lame cows into the crush, it is important to determine which leg is affected. Our vets tend to record these on a recording sheet. Look for:

• obvious swelling (and hoof shape)

• weight bearing while standing still (the lame foot will be positioned so not to carry as much load)

• a head nod while walking in the case of front leg lameness

• the stride length and speed (the lame leg will have a short stride before taking weight, then the sound leg swings through with a longer stride and is weight loaded for longer.

Once you have determined the lame leg, have tied it up, washed it down and checked for footrot, use hoof testers to confirm where the lameness is located. This simple tool works by squeezing and putting pressure on the claw. Watch for a repeatable pain response which is easy to recognise in the hind legs by a tensing of the ‘hamstring’ muscles and the front legs by a tensing of the shoulders. Cows with sole bruising will often have very soft hooves and you will see that the testers easily depress the sole. If there is no response to either claw to hoof testers, then chances are you either have the wrong foot or the cause of lameness is located further up the leg.

Fonterra on Farm Efficiency & Emissions

Many of you will be getting your heads around Fonterra’s recent emission target of a 30% reduction in on farm emissions intensity by 2030 compared to 2018. This target has been put in place for several reasons.

1. Fonterra’s customers are requiring this. They all have green house gas targets and require it from their suppliers. To be able to access these high value markets targets must be set and met.

2. Finance: Sources of capital want to see a reduction in emissions over time.

3. Regulatory; Fonterra must meet disclosure requirements about their greenhouse gases.

While NZ dairy farmers start in a good position with them having the lowest baseline emissions intensity, the international competition is moving quickly. If Fonterra did nothing the overseas competition would overtake them. This would mean Fonterra’s high value customers would potentially move to other suppliers.

The 30% reduction is a collective target across the whole Co-op. To reach this there are four areas that will be addressed, with individual farmers probably most interested in the adoption of best farming practices. Think of it as an opportunity to use all the metrics you are being provided with, to improve efficiency on farm by addressing areas such as:

• Animal health: e.g. mastitis, Johne’s or lameness.

• Improving reproductive performance

• Genetics

• Nutrition

• Minimising environmental stress.

As the season progresses, we can have discussions about what this all means and talk through your Farm Insights Report.

Effect of Lameness on Reproduction

Lame cows continue to be among the three main problems we are seeing on our clients farms together with mastitis and infertility. Lame cows are clearly visible but often not treated promptly.

At this time of year with peak milk production and AB well under way, the economic effect of lame cows can be huge due to lost milk production, lost body weight and the fact that lame cows are less likely to cycle on time.

Lame cows are half as likely to conceive and take on average 40 days longer to conception, compared to their healthy herd mates.

If you need help with lameness contact Andrew, Luke or Ryan at The Veterinary Centre.

Milk Urea Nitrogen

Milk Urea Nitrogen (MUN), provides an indication of dietary crude protein status in a herd. MUN is a by-product of microbial protein/nitrogen breakdown in the rumen. Where there is surplus in dietary crude protein, milk urea will rise. A deficiency will result in a fall in MUN. It is generally considered MUN levels above 15-19mg/dL indicate dietary protein is not limiting for milk production. Above 25-30mg/dL there is a surplus (which will load up nitrogen in the urine).

It is considered in herds where there is no deficit in energy but a restriction in protein, cow production may suffer but weight gain can occur. The exception to this rule will be cows that are genetically programmed to make milk ‘at all cost’ (e.g. overseas Holstein type breeds). These cows will mobilise muscle tissue to support milk production which adversely affects reproduction.

Before the introduction of the 190 Nitrogen cap, we sometimes saw these MUN levels drop below 15mg/dL towards the end of the first grazing round, but then sharply increase as cows enter lusher second round grass that had significant urea application.

This season the average MUN figures to date look like they have fallen further again in a lot of farms. This begs the question – are our pastures/soils becoming more nitrogen deficient - it has been a dry winter/spring so significant nitrogen leaching is unlikely? Is this low MUN really limiting production? Do we need to be more strategic with N application in spring? Many farms have removed more expensive protein supplements from cow diets this year – i.e. DDG which may be adding to the picture.

To answer these questions the Vet Centre has partnered with Dr Jim Gibbs at Lincoln University and will be sampling grass on these low MUN farms through the season starting with end of first round grass.