By Eliza MacKereth, Graduate TRAC Ruminant Productivity Consultant
Ketosis is a metabolic disease that is commonly identified in ruminant animals, particularly dairy cattle. During the first 6-8 weeks of lactation, whilst milk production is increasing, cases are most common. This is due to a severe negative energy deficit in the diet, meaning that the energy required for the animal to be able to maintain body condition and lactate to provide for their offspring is not met. In dairy cattle, ketosis has been noted to affect an average of 7-14% of cows in a herd (Gulnski, P., 2021). However, clinical ketosis and sub-clinical ketosis can often be misdiagnosed or go unnoticed, leading to large economic losses for famers. The illness can have large impacts in terms of production losses, lower reproductivity and increase disease occurrences.
Signs + Symptoms
One of the most common signs of ketosis is a reduction in appetite or selecting forages over concentrates; for example, dairies may notice an increase of residual concentrate in the dairy bale of a ketonic cow. Some animals may display neurological signs. Animals suffering ketosis will also note a production drop and change in milk components. Furthermore, reproductive performance is often negatively impacted by ketosis as the energy required to sustain a true heat cycle or to facilitate a pregnancy is not met. For the animal to recover from ketosis, the diet must provide the animal with an energy surplus to replenish fat stores. Ketosis has also been noted to increase occurrences of other illnesses such as mastitis, metritis, and displaced abomasum (Gulnski, P., 2021). Changes in milk composition may vary, however can often be useful in detecting sub-clinical ketosis. A fat test increasing to above 5% and protein test decreasing to below 2.9% is noted to be a symptom of sub-clinical ketosis in Holstein herds. The fat to protein ratio is another measure to consider, particularly if above 1.4:1. The most accurate way to test for ketosis is by testing ketone levels in the blood; if βHBA concentration in blood is >1200 mmol/L then the case is considered ketosis. This quantity of ketone levels causes neurological changes in the brain to occur, causing a reduction in appetite, hence dry matter intake (DMI) decreases. This drop in DMI often leads to more ketone bodies being released as the animal is not able to meet energy requirements for maintenance. On a cellular level, ketosis is noted to be an abnormal metabolism of volatile fatty acids and carbohydrates caused by a high energy deficit. This leads to an excessive amount of ketone bodies being released into the blood stream of the animal as the fats are converted into carbohydrates. Ketone bodies consist of β-hydroxybutyric acid (βHBA), acetoacetic acid (ACAC), and acetone (AC). Ketone bodies travel to the brain via the bloodstream, triggering the animal to believe it’s full, which further prolongs the starvation and lack of nutrients. A ketonic response is then triggered and the body fat is mobilised.
Susceptibility
Susceptibility of an animal to ketosis can vary greatly depending on nutritional status, nutritional allocation, and management practices. Animals that are in good condition that undergo a sudden deterioration of nutritional allocation are susceptible to ketosis. Although animals are most susceptible in the first 6-8 weeks of lactation, animals in late lactation are also at risk to the metabolic disease. For example, dried-off dairy cows, or any ruminant in the last 6 weeks of pregnancy have a higher risk of developing ketosis. It is crucial that adequate nutritional management occurs at this stage of the animals’ cycle. This is a period where animals will concurrently have a reduced intake capacity due to foetus size alongside an increased energy demand. Low energy density feeds and forages during this time such as dry standing feeds or low quality/high fibre hays or straw can lead to a slowed rate of rumen passage, hence the animal cannot intake the necessary quantity of energy. This will lead to the animal mobilising stored lipid supplies in fat cells to release additional energy. When these fat stores are mobilised, compounds called ketones are released. These ketone bodies can become toxic to the animal if the concentration becomes too high, hence ketosis. Ketosis case occurrences have been shown to be positively correlated with milk production in some studies, meaning that theoretically, the more milk a cow produces, the higher the risk of ketosis. Multiparous cows are much more susceptible than primiparous cows. These groups should be closely monitored for any signs or symptoms of ketosis, alongside any animals with excess fat condition. Minimising climate and handling stress as well as ensuring low worm burden in animals can aid toward reducing ketosis cases.
Prevention
Prevention is key in avoiding the economic disruption that occurs due to ketosis. To prevent the occurrence of ketosis, care should be taken to monitor the body condition of pregnant and lactating animals. Alongside this, the nutritional values and intake of the feed on offer should be calculated to ensure that nutritional requirements are met, particularly energy requirements in an overall well-balanced diet. If animals are grazing pasture, focus on ensuring adequate feed is on offer, and pasture is not of low quality. Supplementary feeding of concentrates or high-quality forages may be required close to birthing. Avoid stress events if possible and shelter from undesirable climatic conditions. This may include strategic paddock selection; for example, selecting paddocks with adequate shelter from tree lines or windbreaks and avoiding hilltops. If possible, handling during critical times should be avoided, however, if necessary, practice low stress stock handling. Plan the calendar of operations ahead and ensure pasture growth and quality aligns with timing of calving to meet energy requirements, otherwise consider purchasing supplementary feeds. Supplementing or drenching glucogenic energy sources can aid in preventing, or sometimes treating ketosis, however, it is best to consult a veterinarian.
Nutritional Needs
Being aware of the nutritional value and composition of feeds is vital in understanding whether dietary requirements are being met. Likewise, awareness surrounding nutritional requirements of the specific class, age and lactation stage of the animal is critical. If diet changes are needed, they should be done gradually and avoid decreasing nutritional value of diet during susceptible periods. In dairy systems ensure that transition diet and lead feed diets account for these nutritional needs. In the 21 days prior to calving, the content of energy and protein in the diet should increase to support the foetus growth that is occurring and to account for reduction in DMI. In the 21 days following calving, keeping the cow separate from the rest of the herd as well as separating heifers and cows is best practice as it reduces competition and allows for a smoother recovery and transition back into the milking herd. Cows that go straight from the lead feed diet to the milking herd diet will often undergo a large amount of stress that may lead to a weakened immune system, hence greater susceptibility to many diseases. In the first 21 days post calving, the diet should have increased protein and starch levels, and decreased NDF (Neutral Detergent Fibre). Similar feed ingredients as the milking herd should be used. After this period, consider adding fats/lipids/oils into the ration to provide additional energy, allowing a higher milk peak and overall better lactation.
Producers that are impacted by clinical ketosis or sub-clinical ketosis should look to assess their production system and plan to ensure that their pregnant and lactating animals are exposed to less risk factors that contribute towards a ketonic state. Ketosis can have a significant impact on animal production in terms of milk production, weight gain and fertility. It is important to understand the potential economical impact that ketosis may have on an enterprise to understand the high value of prevention.
Your TRAC Experts In Ruminant Productivity are here to assist you in understanding & aiding in the prevention of ketosis through meeting the nutritional requirements of your animals, please get in touch with your local TRAC Consultant on
08 8733 1888 or email us at info@totalresult.com.au
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References:
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