AGHAGALLON milk producers Gary and Michael McHenry are among the growing number of progressive farmers using annual vaccination as a central part of their BVD control programme.
The father and son team run a high performing 200-cow herd at Aghagallon outside Lurgan. Expansion in recent years has seen a new cubicle shed built with a straw-bedded transition area for dry cows, optimising comfort and performance.
Working closely with veterinary practitioners at Lurgan Veterinary Clinic, the McHenrys operate a rigid animal health programme. A key priority is to prevent easily controllable diseases such as BVD from impacting on farm profitability.
For the past 15 years, the entire breeding herd is vaccinated with Bovilis BVD four weeks before breeding. The herd is also routinely screened for the presence of the disease and no carrier animals have been found.
They operate a closed herd which also reduces the disease risk. However, Marcel Mulholland of Lurgan Veterinary Clinic is adamant that annual vaccination is still a must.
“While the McHenrys have not identified any PI (persistently infected) animals there is a constant risk of disease being introduced to any herd from neighbouring animals or animals breaking in during the grazing season. We strongly believe that the best insurance policy is to continue to vaccinate so that the herd is not unprotected if disease is introduced,” said Marcel.
The McHenrys are now participating in the voluntary stage of the BVD eradication programme which started in January and is concentrating on identifying PI calves.
“This is something which I have been keen to see implemented across the country for many years. If all herd owners participate and eliminate persistently infected animals from their herds, BVD will become a disease of the past,” said Gary.
BVD Vaccination Strategy
Vaccination combined with identification and removal of PIs and good bio-security are crucial in controlling BVD.
Two injections of Bovilis BVD, given about four weeks apart, are needed in non-vaccinated cows and heifers. The second shot should be given four weeks before breeding.
A booster shot of Bovilis BVD should be given four weeks before breeding.
Leptavoid H, a vaccine for controlling leptospirosis, can be given at the same time as Bovilis BVD.
How to avoid PI nightmares!
Symptoms of BVD infection include infertility, abortions, birth defects and dead calves. In many cases, infection may not be obvious to the farmer or vet. Animals may simply fail to thrive.
The nightmare of PI (persistently infected) animals is the manifestation of the worst effects of BVD infection. This happens when a foetus becomes infected with the virus between days 90 and 126 of pregnancy.
The virus becomes a part of the calf and is not removed by the immune system. Blood samples or ear notches can be taken to test for the virus. Most calves that are BVD virus positive within one week after birth are PIs.
PI animals remain infected with BVD all their lives, shed massive amounts of the virus and are a constant source of infection. From four to 18 months of age, they may start to show signs of weight loss, a chronic scour, and ulcers in the mouth and feet and sometimes along the gut. This is called mucosal disease. Affected animals often die at six to 18 months of age.
Those that do not develop mucosal disease continue to shed the virus and are a chronic source of BVD infection. A minority of PI animals will live to breeding age but most die within two years of birth. A PI cow will always produce a PI calf hence the importance of correctly identifying and testing the dam of any PI calf found.