Most dairy calf raisers unfortunately have familiarity with abomasal bloat. It’s the rapid accumulation of gas in the abomasum, which causes abdominal distension, depression, pain, diarrhea and often death. It can come on so quickly that calves appearing perfectly healthy at one feeding are found dead at the next.
According to Brian Miller, DVM, Senior Veterinarian for Merck Animal Health, abomasal bloat is not difficult to diagnose, but it is difficult to treat. Miller told the audience of a recent Dairy Calf and Heifer Association webinar that 50-60% of cases are fatal, even with veterinary intervention.
“Abomasal bloat occurs most commonly in calves from 5 to 14 days of age, but it can happen up to 21 days,” shared Miller. He said calves in this early stage of life are essentially monogastric, with all milk or milk replacer being digested in the abomasum. This makes abomasal function critical in young calves.
Researchers do not fully understand the cause of this frustrating disease, but Miller said there are three speculative sources:
- Gas-producing bacteria in the abomasum (most likely Clostridium perfringens or Sarcinia ventriculi).
- An excess of readily fermentable carbohydrates, along with fermentative enzymes, in the abomasum.
- Anything that delays the abomasal emptying rate.
Miller said clostridium bacteria are native to both the digestive tract and the cattle-housing environment. But they can become problematic when something fuels their exponential growth in the digestive tract, resulting in vast quantities of gas and potent toxins being produced.
“Milk-based as well as plant-based milk replacers are commonly fed to calves. Problems may arise when there are issues with osmolality which affects how the abomasum handles a meal. High- or low-osmolality solutions delay abomasal emptying which allows bacteria extra time to ferment nutrients,” he explained. “This leads to excessive gas production/bloat. Factors that can affect osmolality include: variations in total solids, addition of electrolytes to milk or milk replacer without additional water; improper mixing (agitation); milk replacer mixing errors; or feeding a poor-quality milk replacer that does not stay in solution.”
The veterinarian noted that accelerated liquid feeding programs delivering large quantities of milk or milk replacer have become the gold standard for feeding that potentially allow calves to reach their genetic potential for growth and future milk production. Rather, than a “step up” diet, it is more beneficial to place young calves on high-volume milk diets as quickly as possible after receiving colostrum to help them achieve early puberty, faster breeding and younger age at first calving.
Accelerated feeding programs also have been implicated as a cause of abomasal bloat. Miller does not believe that is the case because volume is not the issue as long as the quality is there. “Osmolality must be kept in a healthy range because high total solids in an accelerated program certainly can contribute to abomasal bloat,” he said. “That is why it is strongly recommended to offer free-choice water post-feeding to dilute out high total solids that may be present due to potential mixing errors.”
According to Miller, the most important means of prevention of abomasal bloat in calves is consistency, consistency, consistency. “The hardest part of raising healthy calves – and avoiding this disease in particular – is doing the simple things consistently, over and over again,” he advised. They include:
Measure total solids when feeding whole milk – Using a Brix refractometer and an evaluation standard of “Brix +2,” regularly test the milk delivered to the first, middle and last calf. Although imperfect, it is a field test that allows calf raisers to measure dietary consistency. Used on a regular basis, it allows caretakers to manage the diet for consistency and spot changes that might contribute to potential issues. If there is greater than a 2-point swing in total solids, there will be variation in appetites and potential for issues including abomasal bloat. A safe goal for total solids is 12-14% (don’t exceed 15%).
Mix properly – Follow the same protocol for assembling and agitating every batch of milk or milk replacer. Total solids also should be evaluated before every batch is fed. Hospital milk can vary greatly in solids content.
Include additives carefully – Avoid multiple additives, as this may alter the osmolality of a finished formula to unacceptable levels.
Monitor feeding temperature – Again, access at first, middle and last calf. Extremely cold weather may require extra measures to ensure the temperature remains the same from the first to the last calf.
Acclimate calves to large-volume feedings – Once calves are fed a large-volume colostrum meal, start them on large-volume feedings from the start and stay consistent. This reduces the risk of this disease, enhances growth rates and improves immunity. Although 3X a day feeding would be ideal, in absence of this, there is increasingly strong evidence that the “step up” diet is not needed.
Deliver feedings consistently – Ensure the same feed from first to last calf -- from one feeding to the next -- and consistency between feeders. Replace worn nipples to prevent excessive drinking speeds.
Sanitize feeding equipment – Follow routine protocols for cleaning and sanitizing all equipment used to mix and feed the liquid ration. Monitor sanitation regularly using ATP swabs.
Provide water – Deliver clean, free-choice water within 20 to 30 minutes of liquid feedings.
In addition to consistent feeding formulation and practices, a healthy calf starts with a healthy cow. For dry cows and replacement heifers, provide excellent colostrum management; adequate bunk and resting space; a clean, dry, low-stress environment; good ventilation and heat-stress abatement; and focused maternity pen management. These practices improve both cow and calf health.
Vaccination with 7-way clostridial vaccines and scour-prevention formulations also can help manage the bacterial piece of the disease. Miller suggested administering clostridial vaccines to late-gestation dams to fortify their colostrum, then implementing herd-wide programs to deliver the same vaccine to calves at 3 and 4 months of age; at prebreeding; and again in late gestation. Pre-calving administration of scours vaccines also provide colostral protection against organisms like E. coli, rotavirus and coronavirus, in addition to Clostridium perfringens.
Miller advised working collaboratively with both the herd veterinarian and nutritionist to evaluate the causes, preventive measures and treatment protocols for abomasal bloat in individual herds. “The most successful calf raisers are those who pay attention to detail, establish protocols, and follow the same routine, regardless of what else is happening on any given day,” he said. “Controlling the things you can will help your calves overcome the things you can’t.”