Ketosis and hypocalcemia (milk fever) are often referred to as “gateway diseases,” meaning that when they occur, essentially the “floodgates” are opened and the risk of developing other metabolic diseases increases significantly. On the other hand, if the incidence level of these two metabolic diseases is kept very low, this will help to prevent many other transition disorders from occurring.

Subclinical ketosis (SCK) plays a significant role in the profitability of a herd because if it is not monitored, it can go completely unseen. The good news is: Vast amounts of research on underlying causes and prevention strategies of SCK have resulted in opportunities to put more milk in the tank and money in the bank.

Why does it matter?

Large-scale studies conducted on commercial herds across Canada have consistently shown that an average of 20% of fresh cows have mild to moderate fatty liver and would be classified as having SCK. These are the cows that typically go unnoticed and untreated, but what impact does this have on your bottom line?

We know SCK is associated with:

• Increased risk of getting other metabolic diseases
• Increased milk loss
• Decreased reproductive performance
• Increased culling and therefore decreased longevity

A study conducted in 2016 using Canadian data calculated a loss of around $200 per case of SCK when considering all of the losses listed above. At a typical incidence rate of 20%, this is a loss of $4,000 at a herd level with an average of 100 annual calvings.

SCK and liver health

The transition period dictates the success or failure of the lactation. When we dig a bit deeper into SCK, liver function is most critical. The liver plays a huge role in the following processes:

Gluconeogenic capacity: The ability to make glucose that is required for lactose production, which drives milk volume (Glucose is also required for other functions.)

Ureagenic capacity: The ability to convert ammonia into urea to be recycled or excreted

Capacity to clear bacterial infection: Immunity and proper liver function are closely related

The mammary gland sets the priority for nutrient utilization. As nutrient demands exceed nutrient intake, the cow will automatically begin to mobilize bodyfat (triglycerides = TAGs) to meet these energy demands. The TAGs are then broken down into the glycerol backbone and the remaining fatty acids, known as non-esterified fatty acids (NEFAs). NEFAs can only be utilized in a few different pathways (Figure 1).

Some NEFAs will be used by the mammary gland to make milkfat, but most will be taken up by the liver and utilized by one of the following processes:

• Completely oxidized in the tricarboxylic acid (TCA) cycle
  
  
• Incompletely oxidized, forming ketone bodies (BHB, acetone, acetoacetate), which can be used as an energy source but also take energy to export them from the liver
  
  
• Exported as very low-density lipids (VLDL) which can be used to make milkfat
  
  
• Stored in the liver as fat, leading to fatty liver

It is inevitable that all lactating cows will go through a period of negative energy balance when the demands of milk production outweigh what they can physically consume. Their system is then designed to use body reserves to make up that difference, but when this balance becomes too negative, everything starts “falling off the rails.” Fat begins accumulating in the liver cells, thus impairing the liver’s ability to make glucose, keep ammonia levels in check and support the immune system.

Prevention

When looking for ways to prevent SCK, non-nutritional strategies should never be overlooked. Overcrowding in dry cow facilities, lack of bunk space, empty bunks, heat stress, inadequate water supply, lameness and improper timing of pen moves have all been documented to negatively impact levels of SCK.

When it comes to nutritional strategies, however, the power of reviewing the basics around proper nutrition for both the far-off and close-up cow can never be underestimated. But of considerable interest more recently has been the impact of so-called “methyl donors.” Examples of methyl donors include the amino acid methionine, choline, folate and betaine.

What role do methyl donors play?

There is no question that we want to prevent fat from being stored in the liver, and that is where methyl donors come into play. Supplementation of methyl donors during the transition period has been shown to increase the formation of VLDL and decrease stored fat in the liver, thus consistently resulting in significantly less SCK (and clinical ketosis) and more milk.

In addition, most recent research is also showing methyl donors help to improve immune function of transition cows, making them better able to fight off other infections.

As a final point of interest, calves born from dams that received supplemental methyl donors during the dry period also had enhanced immune responses, allowing them to respond more effectively to pathogen challenges.

Monitor and manage

As the old adage goes, “You can only manage what you monitor.” Many operations have made SCK testing a standard part of their fresh cow protocol, either through regular blood work or milk testing. Regular snapshots of transition cow performance through the use of farm software can quickly identify areas of opportunity. As shown in the Figure 2 example, Farm A, with 100 calvings per year, tracked SCK and milk yield on a monthly basis.

With a three-month rolling average of greater than 40% SCK, this was costing them over $8,000 per year (Figure 3).

A nutritional strategy that included the use of a methyl donor in combination with additional antioxidants was implemented, and in less than two months, the rate of SCK had dropped in half and continued to decline steadily over time. Best of all, milk yield responded exactly as had been expected, resulting in an excellent return on investment.

What is the rate of SCK in your herd? What is it costing you? What prevention strategy is the best fit for your herd? Every herd will be different, but correcting potential management issues and exploring various nutritional strategies can lead to significantly more profitability.

Donna Benschop is a Canadian ruminant technical specialist with Cargill Animal Nutrition. Email Donna Benschop. 

References omitted but are available upon request. Click here to email an editor.

Mario Domingue is a dairy technical specialist with Cargill Animal Nutrition. Email Mario Domigue.