Subclinical ketosis can have a significant negative impact on herd health and profitability year-round. But it can particularly be a problem in winter and early-spring months when incidences are historically most prevalent. Recent research also points to a potential correlation between subclinical ketosis and starch fermentability.
Feeding a highly rumen-fermentable-starch source such as high-moisture corn has been shown to depress early-lactation dry-matter intake. A greater reduction in dry-matter intake has been observed when certain starch sources are in the ration at high concentrations — 29 percent dry-matter basis versus 22 percent, for example.
The fermentation of ensiled high-starch feeds causes starch to become more available while in storage. Corn silage, a high-starch forage and contributor of highly rumen-fermentable starch, changes through time. The prolamin-protein matrix that protects starch from fermentation breaks down. The time periods that appear to have greater subclinical-ketosis prevalence coincide with increases in starch fermentability of corn silage, and presumably high-moisture corn.
Research by John Goeser, animal nutrition director at Rock River Laboratory, shows variations in corn-silage rumen-starch digestion follows patterns observed with subclinical-ketosis prevalence. Due to the potential risk of decreased dry-matter intake associated with increased starch fermentability, producers should pay extra attention to fresh cows fed diets high in starch fermentability.
By definition a diagnosis of subclinical ketosis is confirmed once blood beta-hydroxybutyrate is at or more than 1.2 millimolar per liter.
Studies have shown that fresh cows at the high end of subclinical ketosis with blood beta-hydroxybutyrate levels of as much as 2.4 millimolar per liter:
- produce about 400 pounds less milk in the first 30 days of lactation
- are less likely to conceive at first service
- are three times more likely to develop a displaced abomasum, and
- are 50 times more likely to be culled within 30 days.
- The economic burden means about $289 per case when considering cows with both subclinical and clinical ketosis.
Research done by Heather White, Tawny Chandler and Dr. Gary Oetzel, veterinarian, from the University of Wisconsin-Madison Dairy Science Department and School of Veterinary Medicine, led to the development of KetoMonitor, launched in 2015.
The KetoMonitor system allows dairy producers to monitor herd-level subclinical-ketosis prevalence through a milk sample. Of the data that has been collected, about 30 percent is from primiparous cows and 70 percent from multiparous cows. At least one milk sample was collected per cow between days five and 20 in milk. On average 25 percent of multiparous cows and 5 percent of primiparous cows were diagnosed with subclinical ketosis.
Though the data collected by the KetoMonitor system doesn’t indicate the cause of subclinical ketosis, identifying affected cows allows producers to mitigate its negative effects. It also allows researchers to observe patterns that may lead to a greater understanding of specific causes.