In dairy cows ketosis is most commonly seen in early lactation (first month after calving) during periods of high milk production when cows are typically in negative energy balance. The occurrence of this disease is related to increased demand for glucose.

Ketosis has received little attention because it rarely manifests itself in a clinical form – cases are estimated at 3% of the herd. However, subclinical ketosis is much more prevalent and widespread at farm level, affecting as many as 30% of cows in some high-producing herds.

Subclinical ketosis has a severe impact on animal performance and productivity. Research conclusively reports that sub-clinical effects are the basis for future problems, such as cystic ovaries, left-displaced abomasum (LDA), retained placentas, reduced immunity to many diseases and that it is a contributing factor in extended calving intervals and higher culling rates.

Ketosis can have costly consequences as it leads to lower milk production, reduced fertility and a depression of the cow’s immune system. Veterinary consultant Dr Dick Esselmont estimates the cost of a case of subclinical ketosis can range from €600 to €850 per cow, taking into account the direct (reduced milk yields and poorer fertility) and indirect (such as extended calving intervals and higher culling rates) costs on herd profitability.

Diagnosis

Ketosis can occur when the demand for energy (glucose) is high, intake of dietary energy is inadequate, and the body begins to use fatty acids and ketone bodies as its fuel source. The common cause is straightforward; it requires the combination of intense fat mobilisation and a high glucose demand. Both of these conditions are present in early lactation.

Primary ketosis occurs when high-producing cows cannot eat enough to satisfy their needs, or where the feed available is deficient in carbohydrate. Secondary ketosis occurs where some other disease or condition prevents the cow from meeting its energy requirements. Ulcers, a displaced abomasum, mastitis, or other painful conditions can all reduce the cow’s appetite during a period of high demand, resulting in ketosis.

Initial clinical signs of ketosis are due to the low glucose supply to the brain and usually occur within a few days to a few weeks after calving. Typical signs might include cows that become dull, either lethargic or excitable, occasional incoordination, lack of appetite, weight loss, and depressed milk production. Diagnosis is initially based on these clinical symptoms. Further diagnosis depends on detecting the ketones and fatty acids. Ketone bodies have a distinctive “pear drop” smell and many people can smell this on an affected cow’s breath. Biochemical tests can also be performed by veterinarians on urine, milk, or blood to detect the presence of ketones. The “gold standard” test for ketosis is blood level of ß-hydroxy butyrate (BHB; > 1.4 mmol/l).

Treatment

Treatment is aimed at restoring glucose. A quick-acting supplement is necessary to increase blood glucose levels combined with nursing support for the animal. As soon as ketosis is suspected, consult your vet for the most appropriate therapy as overdosing can lead to a depression to the central nervous system and side-effects of making the cow more prone to infectious diseases.

Glucose replacement - Intravenous administration of a dextrose solution (500 ml of 50% solution) by a veterinarian is effective in the short-term, but follow-up treatment is essential if relapses are to be avoided. Oral drenching with propylene glycol or glycerine (glucose precursors; 250-400g/dose) has longer term effects. Treatment should be continued for two to four days.

Hormonal therapy - Many of the long-acting corticosteroids (i.e. dexamethasone) have beneficial effects in ketosis as they help stimulate liver function. Corticosteroids have the ability to break down protein in muscles to produce glucose, which immediately replenishes the depressed blood glucose levels. When using corticosteroids, in combination with other therapies, it is important to ensure an adequate amount of glucose is either in the diet and/or propylene glycol drenches to prevent excessive breakdown of muscle protein.

Prevention and control

To prevent cases of ketosis, attention to the nutrition and management of both dry cows and calved cows is required. Many dairy producers focus their ketosis prevention strategy on the postpartum period, missing several factors observed prior to calving (transition period). Ketosis rarely occurs due to one single factor. However, if cows are managed correctly in the transition period, most risk factors can be avoided.

Managing body condition score (BSC) towards the end of lactation is critical in minimising ketosis risk. Target a BCS of 2.75 at drying off and an optimal BCS at calving should be 3-3.25. Importantly, over-conditioned cows (BCS>3.5) at calving are at the highest risk of developing ketosis. Such animals mobilise excessive amounts of fat post-calving, have a reduced appetite and feed intake potential and are therefore more likely to have a bigger energy deficit, predisposing them to metabolic problems not only ketosis but also maybe milk fever, LDA and fatty liver.

A pivotal area in ketosis prevention is maintaining and promoting feed intake. Every effort should be made to maximise feed intake post-calving so that energy consumption better matches output. In this respect, good practices include feeding quality forage and balanced diets and eliminating any factor that can reduce feed intake. For instance, nutritional imbalances, deficiencies, or erratic management of feeding programmes should be avoided at all costs.

In terms of the housing requirements ensure adequate trough space (0.6m per cow), avoid factors such as limited water availability, poor grouping strategy/overcrowding, excessive time standing after milking and slippery floor at the feed face.

In milk recording herds, it advisable to monitor energy balance by checking milk fat and protein percentages. Suspect energy balance problems if a high proportion of early-lactation cows on the farm have a milk protein percentage less than 3.05, or a milk fat: protein ratio of more than 1.5.