This article first appeared in our sister publication, Dairy Farmer.
Growing heifers that go on to meet their full potential when they join the herd can be a challenge, but there are several things a farmer can do to ensure the heifers are well grown and healthy.
A Smaller Milk and Supply Herds (SMASH) field day held late last year at Andrea and Thomas Annabells Hāwera, South Taranaki, farm was designed to help farmers hit their heifer targets.
The field day featured a number of speakers, including Dallas Nelley, a large-animal vet at Taranaki Veterinary Centre – Pātea Clinic, who explored the factors that go into producing well-grown heifers.
Nelley spoke about heifer health issues of parasites and farm biosecurity.
Parasite burden is by far the most common problem that Nelley sees on farms. In theory, every farmer should undertake faecal egg counts, but he has performed very few in 25 years of vetting.
He emphasised that farmers must at least have a drench plan, and not just drench whenever they feel like it.
“A quarantine drench should be used on any animal that comes onto a farm. The farmer should do it even if the previous owner has said that they were recently drenched. You need to drench them with something that you know works, so you know it’s been done,” Kelley says.
“You wouldn’t believe how many times I’ve talked to farmers and been told that they’d recently drenched their stock, and it turned out that they’d been drenched six months ago. You must be in control.”
A triple combination oral drench is the ideal quarantine drench, but most farmers tend to use a double pour-on.
“There is now resistance to all of the drench families. You need a thorough understanding of your system, because eventually it’s going to become an issue for every farmer if they’re not aware of it and know how to manage it.”
“Refugia” refers to a population of parasites in the environment that hasn’t been exposed to anthelmintic drenches. These worms have no drench resistance, and by remaining in the environment (either on the ground or in the animal) they provide a population of worms that are still susceptible to drenches.
“There are many ways of achieving refugia. It can be created by not drenching your best animals, because they don’t need it, due to them having non-resistant worms. Or you can drench them and put them back into the same paddock instead of a new, clean paddock, so they eat the non-resistant worms straight away.”
If you drench stock and put them somewhere clean, the worms that are left (1-2%) and the animal is still carrying, can only breed with the resistant worms. So, you breed the population a great deal faster towards resistance.
“If you drench them and put them somewhere ‘dirty’, or don’t drench some of the animals so some cows have got resistant and non-resistant worms, they’ll breed, and the number of drench-susceptible larvae will significantly outnumber the drench-resistant population.”
He also highlighted biosecurity as a major animal health issue, saying stock movement is the number one biosecurity risk. Bulls travelling between and onto farms pose one of a farm’s highest biosecurity risks.
“Grazing blocks are very prone to contracting diseases because graziers often receive stock from many farms in many different localities. They also receive bulls. Bulls are often the most disease-ridden animals imaginable, and can carry all manner of diseases,” Nelley says.
He emphasises the need to have a very good relationship with your grazier and to never be afraid to ask them to explain their biosecurity protocols. You must know your bull buyer well and trust them implicitly.
“Here in Taranaki, for example, bulls come here from all over the country, including the South Island. Many have already done a season on a farm. So, unless you run your own bulls you don’t really know their history.
“When the bulls are put in with the heifers, they see many animals at once, so you need a good idea of where they’ve come from. Ideally you should wait three to four weeks before putting them in with the heifers. However, usually the bulls come off the truck and go straight in with them.”
Most farmers are familiar with the disease bovine viral diarrhoea (BVD) and every bull should be tested for it and vaccinated against it.
“We had one case where a farmer lost 35 out of 100 heifer calves because they used a bull that they were told was vaccinated and tested but wasn’t.”
Theileriosis is another disease to be aware of. It’s a disease caused by a species of theileria (a blood-borne parasite) that affects only cattle and is primarily transmitted by ticks. Nelley has tested more positive bulls than negative.
“One farm used cow monitoring boluses and they were constantly getting decreased rumination alerts. It turned out that theileria was going through their herd again. They wouldn’t have known if it wasn’t for the boluses.
“I could give you examples of farms that have lost around 40 cows in a year with theileria. It’s not really heard of a lot, yet it’s quite common in south Taranaki.”
When bulls or any other stock arrive on your property you must remember that it’s your property, and you’re in charge.
Ask your grazier to use the same vet that your farm uses, if at all possible. This gives a continuity of care and everyone, including the vet, knows what’s happening at each property.
Farmers can eradicate some diseases that occur on farm, but not drench-resistant worms. Theileria is the same, says Nelley: “Once it’s on your farm it’s there forever.”
Nelley knows of an instance where a farmer bought one BVD-infected cow from a sale and had to put down 35 heifer replacement calves.
“You don’t hear of those cases because very few farmers want to talk about them.
“About 75% of biosecurity issues are caused by stock movement. Of the other 25%, 12.5% is made up of ‘across the fence’ disease infections. It’s not as big a risk as stock movement, but still a considerable biosecurity threat.”
