Ketosis

In early lactation, all cows experience negative energy balance; however, the severity of this can vary. During severe negative energy balance, the cow mobilises excessive amounts of body fat but cannot convert this to energy through the usual pathways. Instead, ketone bodies such as β-hydroxybutyrate (BHB) are produced. In small amounts, the cow can use BHB as an alternative energy source. However, when ketone production is high, the cow cannot use all the ketone bodies for energy and BHB concentrations increase in the blood. When this occurs, alongside other clinical signs, the cow may suffer from clinical ketosis.

Diagnosing clinical ketosis includes checking for clinical signs and analysing blood BHB concentration during physical examination. It's essential to manage feed allocation and body condition scores to reduce clinical ketosis risk. If a cow shows clinical signs of Ketosis, you should consult your vet. Increase the energy content of the diet or provide oral drenches for treatment. Treating cows with elevated blood BHB concentration using monopropylene glycol drench, without clinical signs of disease, is not recommended.

What are the signs of clinical ketosis?

Ketosis can be displayed in these ways:

Wasting form:

• Lethargy (head down, lack of energy).
• Decreased dry matter intake.
• Decreased milk production.
• Often a sweet smell on the breath (acetone).

Nervous form (less common):

• Excitable, uncoordinated and can become aggressive.
• Strange behaviour such as eating soil, licking fence posts and gates, walking in circles, or standing with heads raised up and pushed into a corner etc.

Risk factors for clinical ketosis

Overconditioned cows

Cows that are too fat at calving (BCS >5 mixed aged cows; BCS >5.5 heifers and second-calving cows) have an increased risk of clinical ketosis. For example, cows that calve at BCS 6.0 are twice as likely to suffer from ketosis than cows that calves BCS 5.5.

Cows that have been overfed pre-calving are also at risk of clinical ketosis. Refer to the feeding guidelines for transition cows.

Underfed cows

Cows that experience a sudden drop in energy intake are at risk of clinical ketosis. This can be due to underfeeding due to insufficient feed, poor quality silage, or adverse weather events.

Poor quality silage can impact rumen function and reduce a cows’ appetite. Silage undergoes a secondary fermentation and when ingested will increase the risk of dietary ketosis. See grass silage for more information on silage quality and testing.

Cows that have been underfed pre or post-calving are at risk of clinical ketosis. Refer to the feeding guidelines for transition cows.

Secondary or underlying health issue

A secondary or underlying issue may result in a reduced appetite that prevents cows from eating sufficient amounts of dry matter (i.e. clinical milk fever).

Responding to an inflammatory event can also cost a lot of energy with recent research suggesting that a dairy cow uses more than 1 kg of glucose within 12 hours when her immune system is activated. This can result in insufficient energy intake to meet demands increasing clinical ketosis risk.

Reducing the risk of clinical ketosis

Clinical ketosis can be prevented by managing feed allocation to ensure feed supply meets feed demand and BCS (both pre- and post-calving), appropriate transition cow management to reduce hypocalcaemia risk, and by paying attention to cow behaviour and adverse weather conditions.

Management strategies to reduce the risk of clinical ketosis

• Ensure cows calve at recommended BCS targets: BCS 5.0 for mixed-aged cows and 5.5 for heifers and second-calving cows.
• If at or below target BCS, feed 100% of their energy requirements during the last 2-3 weeks pre-calving.
• If over target BCS, a slight restriction can be applied by feeding 90% of energy requirements during the last 2-3 weeks pre-calving.
• Ensure cows have adequate feed allocated post-calving by using the spring rotation planner. Target post-grazing residuals of 1500 – 1600 kg DM/ha, considering weather conditions and pasture utilisation.
• Avoid sudden feed shortages, if possible. Allocate pasture accurately and use supplementary feeds if there is a pasture deficit.
• If feed restrictions are unavoidable, try to introduce the feed deficit gradually and consider using once-a-day milking to improve cow energy balance.
• Ensure any silage fed is of high quality and stored correctly.
• Cows that have had difficulty calving or metabolic issues, such as milk fever, can benefit from a starter drench that provides immediate energy, particularly if they have a poor appetite.
• For more information on how to manage the 2-3 weeks pre-calving, through to the end of the colostrum period, see transition cow.

Treating clinical ketosis

If a cow shows symptoms of clinical ketosis, seek advice from your vet. Successful treatment of clinical ketosis will involve providing cows with oral drenches that stimulate an increase in blood glucose. Treatments that have been used in severely affected cows include intravenous metabolic solutions (e.g. 4-in-1; Ca, Mg, P, glucose), intravenous dextrose, multivitamin injections, and use of oral monopropylene glycol drenches.

What can you do?

If the affected animal is still able to stand, increase the energy content of the diet supported by oral drenching (twice daily) of glucose precursors such as monopropylene glycol.

If the animal is not able to stand, provide it with shelter, soft bedding, and continued nursing, including regular rolling from side to side to avoid sores.

Use hip-lifters or similar lifting devices to assist the affected cow to her feet for some time. Hip clamps can only be used to help a cow stand, but not to keep her standing or to move a cow. For more information on lifting see down cows.

Does monensin reduce the risk of hyperketonaemia?

Monensin contains monensin sodium, which alters the rumen microbial population to increase priopionate relative to butyrate. Monensin lowers blood BHB concentrations and may reduce the risk of clinical ketosis in grazing dairy cows; however, it does not improve subsequent reproductive performance when fed immediately before or after calving. Research on the treatment of hyperketonaemia using monopropylene glycol drench was undertaken by DairyNZ in 2016 but had no economically important benefits when routinely administered to hyperketonaemic cows postcalving, see more about Blood BHB and cow performance.