Typically, rates of subclinical ketosis decline in fall, likely because rates of dry matter intake again increase as the effects of heat stress abate.
This past fall, however, rates of subclinical ketosis actually increased as fall turned into early winter, says Robert Fourdraine, VP of research and development for AgSource, Verona, Wis. The analysis is based on milk tests taken on almost 3,400 Midwest herds, more than 215,000 cows and almost 400,000 observations over the past three years. Ketosis was detected using AgSource’s KetoMonitor test, which detects the disease from milk samples taken from cows five to 20 days in milk.
Fourdraine is not sure why the rates increased this year, but the results suggest dairy farmers should be monitoring fresh cows for signs of ketosis and intervene quickly if they occur.
Ketosis can be a costly disease, with first-calf heifer costs estimated to be $375 per case and older cows, $256 per case. The costs come from lower peak milk, slightly higher somatic cell counts, reduced conception rates (6% lower in heifers; 2% lower in cows) and higher rates of culling (6% higher in heifers; 5% higher in cows). “Impacts are greater if subclinical ketosis is observed in the first five to 11 days in milk,” adds Fourdraine.
Analysis of more than 100,000 cows shows that once cows are found to be ketotic, they are more likely to have ketosis in subsequent lactations. If a first calf heifer is negative in her first lactation, there is only a 14% chance she will be ketotic in her second lactation. But if she does have ketosis as a heifer, she has a 22% chance of being ketotic in her second lactation.
The risk goes up for older cows. If an older cow is negative in a lactation, there’s still a 28% chance she will be ketotic in her next lactation. But if she is positive in a lactation, there is a 45% chance she will be ketotic in the next lactation.
Mid- and Late Lactation Abortion Risks
While many dairy farmers pregnancy check cows 30 days or so following breeding, few again recheck cows 30 days after that. But research shows there’s a one in six chance that cows abort in that next month. And another 7% will abort by about 200 days after breeding, says Robert Fourdraine, VP of research and development for AgSource.
As a result, nearly a fourth of cows initially confirmed pregnant at that first pregnancy check can be open when it comes time to dry cows off. Those losses are particularly acute if cows are bred in late summer or early fall, where early embryonic death is more common.
New, highly accurate milk-based tests are now available to test for and confirm pregnancy. Available through some DHIs, farmers can simply schedule a pregnancy test along with normal milk sampling for a nominal additional fee. AgSource can also run individual tests from stripped milk samples from a single quarter.