Keeping Your Herd Safe From Brought in Health Risks

A number of North Island, New Zealand members have questioned the need to have bulls tested for BVD (bovine viral diarrhoea) and EBL (enzootic bovine leucosis) before they are brought into their herds and have asked what procedure is involved.
We note that circumstances differ between New Zealand and Australia. At present there is a big drive in Australia to vaccinate against BVD.

Here's an explanation for NZ members
from Chris Cricket B.V.Sc. Veterinarian, Cambridge, New Zealand.
There are a number of health procedures that as breeders and caretakers of your animals that should be normal routine practise. One of them is the testing of breeding bulls before sale or lease and making sure any bought in or leased bulls for mating with your females have been BVD and EBL tested. Testing for both is a simple blood test. When sending your bulls off farm for breeding purposes, having them vaccinated against BVD is a good idea.

BVD is a viral cattle disease in which carrier animals transmit the disease to non-immune stock. Infections can go unnoticed in adult animals but with calves and weaners it can be more severe with diarrhoea the main symptom. After infection, animals are usually immune for life though a serious consequence is that calves born from dams infected during pregnancy will shed the virus for their entire life.

These offspring are PI cattle or "persistently infected". Introducing a "persistently infected" bull to your herd is a significant threat to your herd's reproductive performance with a decreased conception rate, abortions, premature births, stillborn births, weak/dummy calves and congenital defects.

The percentage of "persistently infected" BVD bulls is very low but it is definitely not worth the risk of introducing such a bull to your females and those bulls should culled and not used or sold.

At the same time as testing for BVD, testing for Enzootic Bovine Leukosis (EBL) should be done. EBL is not common but it is a viral transmissible disease transferred in certain blood cells during procedures such as ear-tagging, vaccinations, TB testing and rectal palpations. Transmission can also occur across the placenta to the foetus and the virus can be transmitted in colostrum and milk.

After infection the virus becomes established in the recipient's lymphocytes and may result in one of two different conditions. It can be a persistent benign lymphocytosis in about 30% of infected cattle or a cancerous condition known as bovine lymphosarcoma in about 5% of infected cattle. For further explanation contact your local vet.


Your Questions are Needed to Help Us Share Knowledge
Do YOU have a question you'd like answered? Or perhaps ideas about things new Lowline owners need to know? Email Sally Yearbury or Tammy Breuer with your questions and they'll find you the answers. Send pictures if you have them.