Like a slow leak from a car tire that eventually turns into a flat, subclinical ketosis and milk fever can slowly drain profits from your dairy.
Cows with subclinical ketosis or milk fever will appear completely normal, floating under the radar of common detection tools and treatments. Making real changes to your transition cow program will help minimize subclinical fresh cow disorders and keep your herd on the road to success.
Some research suggests that up to 40 percent of fresh cows may be hindered by subclinical ketosis. Traditionally, subclinical ketosis is assessed for individual cows using urine strips or milk powders that measure ketones, including beta-hydroxybutyrate (BHBA). In the last few years, use of the Precision Xtra Meter® has become more common as this cowside tool measures BHBA levels through a simple blood test.
Across a handful of university studies, cows that showed elevated blood BHBA, but were not clinically ketotic, had 4 to 7 percent milk loss in early lactation compared to healthy herdmates. Beyond milk loss, additional profits are stolen by putting cows at higher risk for other metabolic disorders.
Sampling for BHBA can help you catch and treat subclinical ketosis sooner, often requiring less aggressive treatment. The University of Wisconsin-Madison and Cornell University conducted a large field study of subclinically ketotic cows. They evaluated differences between cows left untreated and those treated with 10 ounces of propylene glycol. The results showed:
- Untreated cows were 1.6 times more likely to get a displaced abomasum and 2 times more likely to be culled from the herd within the first 30 days in milk (DIM).
- Treated cows were 1.5 times more likely to resolve their subclinical ketosis and half as likely to develop clinical ketosis, and produced 1.5 more pounds of milk per day in the first 30 DIM.
Subclinical milk fever
Unlike subclinical ketosis, we have no quick cowside test for detecting subclinical milk fever. However, progressive nutrition practices can have significant effects.
The lowest blood calcium concentrations in fresh cows occur in the first 24 hours after calving. Subclinical milk fever is typically defined as a blood calcium concentration less than 8 mg/dl. Cows will typically show clinical signs of milk fever when blood calcium falls below 5 mg/dl.
Dr. Gary Oetzel, UW-Madison School of Veterinary Medicine, estimates that 50 percent of cows fed typical prefresh diets with no anionic salts get subclinical milk fever. He estimates the associated losses to be around $125 per case due to lost milk and higher risk of metabolic diseases. In contrast, the risk of subclinical milk fever is substantially lower for cows fed anionic diets, with just 15 to 20 percent of cows experiencing subclinical milk fever.
Balancing prefresh diets for dietary cation-anion difference (DCAD), feeding low-potassium diets prepartum and lowering prefresh diet calcium concentrations are all strategies for preventing milk fever. When feeding a negative DCAD diet, it is critical to monitor urine pH to ensure blood is being properly acidified in prefresh cows (urine pH should measure between 6 and 7). Each week, try to test 8 to 10 cows that have been on the anionic diet for a few days.
Stop the drain
Don’t let subclinical issues drain your herd’s health or farm profits. Work with your nutritionist and veterinarian to develop your strategies and get your fresh cows off to the best possible start.