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How to investigate an outbreak of abomasal bloat in dairy calves

How to investigate an outbreak of abomasal bloat in dairy calves

Abomasal disorders (bloat, twists, infections and ulcers) are a common problem in primarily unweaned dairy calves. While each problem (e.g. bloat) may occur independently, they are inter-related ailments and they may also be misdiagnosed.

They accounted for some 12% of all cattle deaths in March 2021, and ~6% of deaths in calves (1–5 months) submitted to the regional vet labs annually, with no change over a decade. The clinical signs include reduced milk/milk replacer (MR) intake, dullness, colic, bloat (often recurrent), diarrhoea, dehydration, cold, collapse, and sudden death (‘perfectly healthy, found dead’).

The onset of bloat is thought to be precipitated by a combination of many factors, but the main cause/s of the condition are often feeding and hygiene-related. Abomasal disorders can occur as an isolated case or as an outbreak with severe losses year after year, even on well-managed farms. Here we outline how best to troubleshoot outbreaks of abomasal disorders in dairy calves from farmer, advisor and veterinary practitioner perspectives.

Investigating an abomasal bloat outbreak

Relevant background information should be recorded in a standardised questionnaire. Sample investigative questions (referring to the period prior to and during the outbreak and any recent changes) which should be asked during a farm visit include:

  • Case definition - what is the problem (e.g. just bloat or bloat plus calves dying suddenly)? Which calves were affected (heifers/bulls, breeds, fed milk/MR, from teated/open buckets/automatic feeder)? At what ages? How many were affected/died and how many were at risk? When did the problem occur (what was the weather like?) and is this the first year of it? Has the vet examined/treated/sampled the calves? Are there any sample results?
  • Farm background - what is the enterprise type, staff, calving pattern, number of calves at risk and calf management (e.g. if heifers and bulls are managed differently and number of heifers retained / when are bulls sold)?
  • Newborn calf care - describe colostrum (volume, quality, hygiene, storage, pooling, timing and methods of feeding) and navel (cord antisepsis) management;
  • Calf housing - detail of different calf ages, house/pen types, ventilation, bedding, calf groups, age ranges, stocking rates, disinfection, water sources and automatic feeder layout;
  • Calf health and performance - outline preventive medications (e.g. cow/calf vaccines, antimicrobial use, anti-crypto/cocci), vet involvement, number of treated calves, lab reports and whether/how often calves are weighed and average daily gain;
  • Environmental hygiene - describe cleaning/disinfection and replacement routines and hygiene score of colostrum and milk feeding equipment (condition of stomach tubes, buckets, teat/tubes, nipple bars, automatic feeder), housing (bedding, fittings, water sources, passageways) and feed (colostrum, milk/MR, water, ration, hay, silage, straw);
  • Calf feeding - how (automatic feeder/manual), how much (volume/feed/day, milk curve), how often (frequency), how warm (temperature at mixing/teat) and what (milk/waste milk/MR/ additives (e.g. electrolytes, antimicrobials/anti-cocci/anti-crypto)/water) liquid feed is offered (teat/no teat) and withdrawn (weaning policy, age, weight)? If MR is fed, what is the product, composition, mixing rate and total solids percentage (in normal/ cold weather)? If automatic feeders are used, view service/calibration reports and feeding/cleaning programmes. Detail water (source, type, availability, number of water points, quality), roughage and ration feeding management (type, provision, appearance, protein content).

In addition to these questions, a farm visit will involve examination of the calves (especially feeding behaviour, health and weights), their environment, feed and feeding equipment and, as necessary, collection of appropriate samples.


Depending on the questionnaire responses, the following sampling may be warranted. From the calf, blood samples (to check colostrum management), faeces (if diarrhoea), nasal mucus (if pneumonia), body weights (weighband/scales) and carcass (postmortem examination). Feed samples including colostrum/milk/MR [milk solids percentage as fed/refractometer reading, microbiology/adenosine triphosphate (ATP) swabbing, water (microbiology)]. Biofilm swabs from feeding equipment (e.g. teats, mixing bowl, tubes, buckets) for aerobic and anaerobic/capnophilic quantified culture or ATP bioluminescence. The final aspect of the investigation is the provision of a recommended list of changes to current calf management protocols, preferably in the form of a written, prioritised, ‘to do’ report.


Given the multifactorial nature of abomasal disorders in calves, a systematic calf management audit involving an investigative questionnaire and targeted sampling protocol is recommended. Critical to this audit is a holistic investigation of all aspects of calf management, not just focusing on the bugs or the milk/MR.


  • Abomasal bloat is a frustrating problem in unweaned dairy calves;
  • Investigation of outbreaks involves a farm visit to gather a detailed case history, examine the calves and their environment and collect relevant samples;
  • Systematic investigation is best conducted using a purpose-designed questionnaire.

Authors: John Mee1, Fergal Coughlan2, Martin Kavanagh3 and Jessica Cooke4. 1Teagasc, Animal & Grassland Research and Innovation Centre, Moorepark, Fermoy, Co. Cork; 2Teagasc, Clonakilty Agricultural College, Darrara, Clonakilty, Co. Cork; 3Veterinary Consultant, Cleghile, Tipperary; 4Volac, Hertfordshire, UK.

This paper was originally published as part of the Moorepark '21 - Delivering Sustainability open day.