Looking after the health of dairy calves

At this stage most dairy calves should be off milk and on the best grass available. Aftergrass from bale silage taken in May is an ideal feed for calves and if not being fed to milking cows or finishing cattle, it should be grazed by the calves. Even if most of this grass is needed for other stock, it might pay to fence off a smaller section and give it to the lightest of the calves.

Separating the calves based on liveweight should be a priority from now on. Weighing and monitoring liveweight gains is the gold standard, but even separating the lightest calves on a visual assessment is really worthwhile. The key here though is to know what is on target and what is not. There is no point in separating out the lightest calves if even the strong calves are under target weight too.

If no scales is available, then try get your hands on a weighband (very accurate and easy to use on calves but less accurate on older stock). Alternatively, put three or four even heifers into a cattle trailer and weigh over the weighbridge in the local co-op or mart to calibrate your own eye.

Target weights for February born dairy replacement calves with an expected mature liveweight of 580kg is currently 135kg. Over the course of their lifetime, a dairy replacement animal’s average daily gain should average around 0.67kg per day. This seems low, but we must remember that growth rates decrease dramatically during the winter months when animals are housed, so higher than average growth rates are required during the summer months to achieve target weights. For beef calves, the daily liveweight gain targets are higher.

March and April born calves need higher daily liveweight gains to get them up to target weight. So these animals should be on the better quality grass and given preferential treatment. If there isn’t enough good quality grass for these calves, then meal should be fed too.

On meal feeding, 1kg of meal will provide about one third of the calf’s diet, with the rest coming from grass. So even if meal is being fed, it will not make up for feeding poor quality grass. The best calf performance seems to be when they are moved onto fresh pasture every four to five days and are not being asked to fully clean out the pasture.

Dosing

Most calves should have received their first worm dose in June or July. There are two types of worms that we are trying to prevent: gut worms (ostertagia) and lung worms (hoose), but lung worms generally aren’t a problem until late summer and autumn.

Calves have no immunity to gut worms, maiden heifers should have some immunity and adult cows should have full immunity.

Issues with a lack of immunity in the second year or in adult animals come about as a result of failure to build up enough immunity in the first year. This could be due to using too many doses and/or dosing too soon after turnout.

Calves should be left at least three weeks after turn out to build up natural immunity against gut worms, but ideally calves should only be treated for the first time when symptoms show. Symptoms are very loose dung and poor thrive as observed by liveweight gains. The gold standard here is to take faecal samples from a sample of calves to test for faecal egg counts.

There are three options for dosing calves using; a drench dose every three weeks; using an ivermectin based dose at weeks three, eight and 11 or using a long lasting dose such as bolus or an injection into the ear.

Cost wise, there isn’t a whole lot of difference between the three products when you take into account the extra labour and product needed for the drench products.

In brief

Keep dairy calves on the best quality grass available to ensure high liveweight gain.

Best policy is to move calves every couple of days and don’t fully clean out paddocks.

Calves have no immunity to gut worms, maiden heifers should have some immunity and adult cows should have full immunity.

The gold standard is to take faecal samples from a sample of calves to test for faecal egg counts before dosing for worms.