From the Vet Should you ear notch or vaccinate? It really depends…ask your heifers! If you are reading this, you must be aware that BVD is the most significant disease affecting Southern Australian beef producers. If you are a seed stock producer, your produce is inherently presumably more valuable, hence the cost of BVD would be greater if your livestock were affected. Most Angus breeders are familiar with testing their sale produce to protect their clients but let me introduce you to a simple concept which should resonate with you, assuming you have chosen to invest in or are considering investing in herd level BVD control within your enterprise. It is my dream that every producer in Australia will work with their veterinarian to annually collect blood samples from a small proportion of each of their replacement heifer groups prior to mating to estimate their BVD immune status and then to act upon those results. At the low cost of a buck or two (distributed over the entire heifer group), the blood test results will provide a true value proposition for investment in the systematic management of BVD. Quite simply, immune heifers should be ear notch tested and naïve (heifers unexposed to BVD) vaccinated. If performed consistently and annually, each new generation of replacement heifers will go on to be mated both immune and PI free… The cost of BVD has been estimated at between $20 and $90 per breeder on affected endemic properties. Part of the variability in the cost of BVD relates to timing. When previously unexposed or unvaccinated animals make close contact with a Persistently Infected animal (PI), they almost invariably contract BVD, resulting in significant immune suppression and potential reproductive losses. Immune suppression can be significant if the affected animals are under stress or other disease challenge such as during a scours outbreak, pink eye challenge, or the early phases of lot feeding. Reproductive losses can occur at any stage of pregnancy, but are most significant during mating or early pregnancy, and can result in the production of more PI calves. Estimates of the cost of BVD also vary as they are linked directly to the value of the production system. As producers of some of Australia’s most valuable beef and genetics, there is no doubt in my mind that every Angus producer should be paying close attention to BVD and should strive for freedom from the virus within their own production system. BVDV is unique in that it is transmitted and maintained almost exclusively by PI animals. PI animals themselves were exposed to BVDV before they were born, whilst in utero. Either their dam was a PI herself, or, more commonly, she became infected with the virus whilst pregnant. When exposed between one and four months of gestation the calf’s developing immune system mistakenly assumes that the virus is “normal”. If the calf survives to birth, its immune system will continue to ignore the virus. They are born and remain Persistently Infected with BVDV for life. If you control PI’s, you will control BVD. I established our laboratory in Esperance in early 2006, in order to provide Australian producers and their veterinarians access to simple and accurate PI diagnosis from easily harvested ear notch tissue. Ours was the first laboratory of its kind in the southern hemisphere and it has led to us meeting hundreds of amazing Angus stud breeders whilst testing close to three quarter of a million ear notch samples for Persistent Infection. We work with hundreds of veterinarians and thousands of producers helping them to construct herd specific and herd level systematic BVD eradication programs. WA ANGUS NEWS June 2021
20
