Subclinical ketosis (SCK) is a significant health challenge in our dairy herds, primarily occurring in early lactation when cows experience a severe negative energy balance. Characterised by elevated ketone body levels and without overt clinical signs, SCK can negatively impact milk production and reproductive performance, and increase the risk of other metabolic disorders. Understanding the metabolic processes leading to ketosis, the role of the liver, and the importance of balanced nutrition, including macro minerals and trace elements, is the key to effective prevention and management of subclinical ketosis in dairy cows.
Metabolic process and contributing factors
Subclinical ketosis is a metabolic condition that occurs when a cow’s energy intake is insufficient to meet its energy demands, leading to excessive mobilisation of body fat reserves. Although often considered a disease, ketosis is more accurately described as a finely-tuned metabolic process that is disrupted when the liver is overwhelmed.
The body’s energy storage system is designed to store energy during periods of abundance and release it during times of need. However, this system can falter under conditions that require the cow to expend high levels of energy, ie. disease pressure, calving, and peak milk production.
These stress events can quickly drain energy reserves. When cows are provided with a properly formulated diet during early lactation, they usually shed some of the condition gained during the previous season, using this fat as ketones to fuel production. If a cow is under extreme stress and her diet lacks sufficient energy, she may lose condition rapidly, causing fat to be converted to ketones at a faster rate. This rapid conversion strains the liver, which must process the excess ketones. If unchecked, subclinical ketosis can progress to a clinical stage, exhausting the cow’s energy reserves and potentially leading to collapse and death.
Do cows show symptoms of SCK?
Subclinical ketosis lacks blatant clinical signs, but several subtle symptoms may indicate its presence, including decrease dry matter intake, lethargy and reduced activity, mild to moderate weight loss or failure to regain lost body weight post-calving, and a distinctive sweet or fruity odour on the breath due to acetone accumulation.
Minerals in prevention
Proper nutrition is essential in preventing SCK, with balanced diets rich in essential macro minerals and trace elements playing a key role. Phosphorous is vital for energy production, while calcium and magnesium are essential for maintaining normal metabolic function and preventing ketosis. Ensuring adequate levels of these minerals in pre- and post-calving diets is also a must.
Potassium supplementation is seldom necessary under New Zealand conditions, as pasture typically provides adequate potassium. Excess potassium, however, can be problematic as getting rid of the excess requires more energy. Sodium is important for regulating the rumen and energy flows from the rumen, making careful calculation of salt supplementation necessary based on the diet and total intake.
Trace elements such as chromium, selenium, iodine, and cobalt play key roles in glucose metabolism and antioxidant defence mechanisms, contributing to overall metabolic health and resilience against ketosis. Regular monitoring of blood ketone levels and regular dietary adjustments based on nutritional analysis can help in early detection and management of subclinical ketosis.
The central role of the liver
We can’t talk about ketosis without emphasis the role of the liver. Maintaining liver health and capacity is essential in effectively addressing ketosis. Farmers can reduce the severity or incidence of ketosis by increasing the liver’s capacity to process adipose tissue. This can be achieved by ensuring minimal condition gain over the dry period, managing transition diet efficiency (correct NDF, energy, protein, and diet volume), and completing the full 21-day transition length. Additionally, it involves formulating the correct mineral balance, maintaining rumen stability, and minimising stress.
Feed, energy, and minerals will only remediate ketosis once they reach the liver and are converted to usable energy at the cell level. Trace elements are fundamental in producing hormones that drive optimal liver function and regenerate and replace liver cells. The liver has the highest cell turnover rate of any organ, underscoring its capacity for renewal and its central role in managing ketosis.
By focusing on these preventative measures and understanding the metabolic processes involved, dairy farmers can effectively manage subclinical ketosis in their herds, ensuring better health and productivity for their cows.
First published in Dairy News, August 2024