News March - April 2023
Your first step in managing Bovine Leukemia Virus With the USDA estimating that Bovine Leukemia Virus (BLV) has infected up to 94% of all dairy herds in the United States; chances are you have it! While it’s true that BLV is incurable, it is not unmanageable. The easiest and most cost effective step to take to start managing BLV is to estimate your overall herd prevalence through a BLV Herd Profile. A BLV Herd Profile (below) is achieved by testing DHI samples of the 10 most recently fresh cows in each of the 1st, 2nd, 3rd and ≥4th lactation groups. With individual animal results known, a lactation specific prevalence is calculated showing the percentage of cows in each lactation group that tested positive. This prevalence is useful for understanding your herd risk, determining which management practices to implement and monitoring the BLV status of your herd. Armed with a BLV Herd Profile, you can decide where to target your efforts for controlling it. If the herd has low prevalence and does not detect any positive cows, you could consider doing a whole-herd BLV test and segregate or cull positive cows to eliminate BLV from your herd. If you have a higher prevalence (or if culling/segregating positive animals is not practical), you can reduce prevalence with management changes. The BLV Herd Profile helps you identify where in the production cycle cows are becoming infected, enabling you to target management changes.
The BLV Herd Profile is the most cost effective (you do not have to test the entire herd) and easiest (ask your DHI Specialist to identify samples during routine DHI testing) first step to managing BLV. With a Herd Profile you can: • compare your herd to other herds in the 2014-2016 National BLV, • track the effectiveness of management changes to reduce BLV, and • monitor changes of your herd’s BLV status. Once herd prevalence is known, a testing and management strategy should be developed. With low herd prevalence, follow up may be as simple as completing a Herd Profile annually, with routine ELISA screenings on incoming fresh cows to keep prevalence low. When herd prevalence is higher, follow up may include an annual herd profile, testing all incoming fresh cows to find new infections; follow up testing of all positive cows to identify the most contagious (super-shedders) animals so action can be taken to slow/eliminate the spread. For convenience, testing results can be uploaded to PCDART to further assist in making management decisions of positive cows. As easy as establishing a Herd Profile is, you don’t have to go it alone. CentralStar provides follow up consultation to answer questions and discuss next step management strategies. Talk to your DHI Specialist for more information.
BLV Herd Profile Your Herd
National 2014-2016
70% 60%
Percent BLV Positive
60%
60%
50%
54%
40% 30%
20%
0%
38% 47%
44%
30%
10%
60%
In this example, the BLV Herd Profile shows low prevalence in first lactation with an increase in later lactations. From this you can surmise the majority of ongoing transmission is happening in the milking herd. Adjusting management practices that influence the spread of BLV in the milking cows (single-use needles and palpation sleeves, fly control, etc) could be effective.
20%
10%
1st
2nd
3rd
4th and greater
Average
Lactation Group
Learn more about managing BLV in this on-demand webinar with Dr. Don Niles and leading Michigan State University researcher, Dr. Tasia Kendrick when they discussed recent research efforts that help manage the effects of BLV.