Dairy management: do you need to dose cows for worms?

Dosing cows: Farmers are wondering if it’s a good idea to dose cows for worms during the summer. The popularity of this practice has definitely increased in recent years, but is it necessary? There is no clear answer to this. If a high proportion of cows are coughing with a very deep husky cough, then they probably have lungworm. This is nearly always seen alongside a drop in milk yield. Often, the milk yield will drop first. In such cases, dosing with a zero milk withdrawal wormer is necessary. Lungworm is tricky to diagnose as lungworm eggs don’t always show up in faeces.

The other worm to watch out for is stomach worms. These do not normally affect adult dairy cows but they have been known to be a problem in some cases, particularly among younger cows and where there was poor dosing protocol as calves.

Symptoms here will be milk drop, very loose dungs and low body condition score. Faecal egg counts are good at detecting stomach worms. Relying solely on bulk milk tank health screening to determine whether to dose is a poor strategy. The bulk milk test screens for exposure to certain parasites. It doesn’t mean that the cows are themselves infected.

Most pastures will have worm larvae present, but this doesn’t mean that the cows are suffering from worm infestations. To sum up, dosing cows’ mid-way during lactation is costly and using anthelmintic drugs where there is no need can lead to resistance. I’d be inclined to wait for evidence of parasites before dosing. Knowing what to look for is a better policy than blanket dosing.

Lime: Now is the time to be planning lime applications. Fields that are low in pH (less than 6.1) will need lime to bring them up. Soils with low pH don’t perform as well as those at the correct pH. There will be less soil microbes and the availability of other nutrients such as phosphorus and potassium will be curtailed. David Wall from Teagasc describes the effect of low pH on soil microbes like earthworms as sticking a naked hand into a drum of acid descaler. The low pH will burn your skin and it does the same to earthworms.

Lime is a bit awkward to manage as it can’t really be spread in small quantities. The minimum quantity is usually a 20t lorry load. At a spreading rate of 2t/acre, one load will do 10 acres.

There is no problem spreading lime on grazing land, but do so after the field is grazed, not before. Spreading lime after silage is cut is ideal. However, slurry and urea should be spread a week or so before the lime, and not for a few months after lime is spread.

Moorepark: We have a full preview of the 2019 Moorepark Open Day, which takes places next Wednesday 3 July. Key questions for the day will be around breeding and feeding policy for the future. There’s a lot of noise in this area, so it will be interesting to see what direction the research is going in. You always learn something at Moorepark Open Days.