Fall Ushers in “Bloat Season” for Preweaned Dairy Calves

Fall is a busy time of the year for dairies and calf operations, and it’s also a time we need to be extra-vigilant about a life-threatening health condition for calves: bloat.

Many calf raisers report that their incidence of bloating rises in the fall. I think this is mainly due to the fact that the weather swings pretty significantly in September and October. The stress of those environmental changes can alter eating patterns, which fuels the cascade of events that can lead to bloating.

Unfortunately, the onset of bloat in young calves can be very sudden. Animals that appear to be perfectly healthy at one feeding may be found dead at the next – a frustrating and disheartening scenario for calf owners and caretakers.

“The most common bacteria associated with bloat is clostridia. Specifically, two strains of the bacteria – Clostridium perfringens and Clostridium sordellii, are responsible for digestive infections that can cause sudden — and sometimes deadly – bloat in preweaned calves.”

Most bloat in preweaned calves occurs in the abomasum, compared to bloat in the rumen that tends to happen to older animals. Anything that disrupts the passage of nutrients through the abomasum can trigger the gas build-up that then causes abomasal bloat. Some primary examples of those events in the fall include:

(1)   Disrupted milk-feeding schedules – Sometimes the hectic pace of fall can lead to altered work schedules and/or relief workers doing the calf chores. If calves are fed outside of their normal feeding times or go off feed due to stress, they are more prone to bloat when they consume their next meal.

(2)   Lack of water – If calves quit drinking water, or water is withheld as freezing temperatures set in, it increases the osmolality (concentration) of their total diets and slows feed passage through the digestive tract.

(3)   Higher-concentrate milk replacer – A similar scenario can occur when producers raise solids levels in milk replacer in an effort to supply more nutrients to combat the onset of cold weather. I recommend keeping milk replacer solids at a steady 12.5-13.0% throughout the year, and increasing total milk replacer volume instead of concentration as the weather turns colder. Also, weighing milk replacer powder versus scooping is recommended to ensure consistency between batches.

(4)   Changes in feeding temperature – If weather conditions shift but feeding practices do not, the result can be calves drinking cold milk or milk replacer. This, too, can slow the rate of passage through the calf’s digestive system and trigger bloat. Be sure to keep feeding temperature near the calves’ body temperature of 102.5°F.

(5)   Shifts in grain consumption – Calves may become hungrier for free-choice starter grain as ambient temperatures cool. This can cause digestive upsets – in this case, more likely in the rumen -- due to “slug” feeding if they run out of grain then overeat when it is replenished. Bloat also may occur because calves consume “fines” as they pursue every last morsel of feed. Be sure to keep an ample supply of fresh starter grain available to calves, and be prepared to replenish it more frequently in the fall.

(6)   Inadequate sanitation of feeding equipment – This may not be a “fall-specific” problem, but if calves consume harmful bacteria at the same time that other factors make them more vulnerable to gut infections, it creates an opportunity for those bacteria to invade.

The most common bacteria associated with bloat is clostridia. Specifically, two strains of the bacteria – Clostridium perfringens and Clostridium sordellii, are responsible for digestive infections that can cause sudden -- and sometimes deadly – bloat in preweaned calves. When clostridia proliferate in the digestive tract, they produce gas that then causes bloating.

The spores that carry clostridia are very hardy and readily present on most farms. That’s why sanitation of feeding and calf housing are so important. Many dairy producers also utilize clostridial vaccines as an extra layer of insurance to help keep clostridia at bay. Whether or not to vaccinate for clostridia is a decision that should be made with the advice of the herd veterinarian.

Clostridia also are susceptible to competition from other bacteria. Some producers have found the addition of Bacillus subtilis to the milk diet to be an effective measure in controlling clostridia.

While careful attention to feeding routines, water and grain delivery, and sanitation is important year-round, they require even more consideration in the fall to ensure a safe and healthy transition into the winter months ahead.

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