Once the dairy calf hits the straw of the maternal pen, it is removed from its mother and shuttled away to an individual pen or hutch where abomasal bloat is often waiting. Although not fully understood by dairy veterinarians and specialists, the relatively high incidence of abomasal bloat in young dairy calves can be significantly reduced when preventative measures are implemented in their pre-weaned feeding and management programs.
It is known that abomasal bloat needs three elements to occur: (1) a population of gas-producing micro-organisms, (2) a source of dietary carbohydrates and (3) a general abomasal environment, which results in the slowdown of the gas-emptying rate of the abomasum. There are also a multitude of mitigating nutritional and management factors that seem to tie these three conditions together, which substantially increase the threat of abomasal bloat in dairy calves.
Clostridium perfringens — a bacterium that is found in many environmental sources including the intestines of animals — is the first element often cited as the primary microbial culprit and leading cause of abomasal-related deaths in fast-growing/milk-fed dairy calves of two to five weeks of age. It is a relatively common organism found in many dairy barns, calf housing and even naturally in the gastrointestinal tract of exposed calves, but usually in small harmless populations.
Such passive existence of clostridium perfringens ends when large amounts of dietary energy such as from lactose (milk carbohydrate) become available. Type A of clostridia proliferates in the abomasum and small intestine of the calf, which rapidly produce toxins that cause damage to the intestinal mucosa lining. There is also excessive gas production by microbial fermentation of carbohydrates, coupled with the prevention of its expulsion, that leads to associated bloating.
Some research suggests that feeding a large volume of milk or mixed milk replacer in a single feeding, erratic feeding schedules or not feeding enough extra water to pre-weaned dairy calves contribute to a higher incidence of abomasal bloat. Furthermore, dairy calves fed high-osmolality milk replacers or electrolytes have been thought to increase the risk in some dairy calf barns.
Milk replacer particle size
High osmolality or the concentration of total particles in a solution (re: milk powder or electrolyte salts mixed with water) has been theorized to slow the natural digestive process of feeds in the calf’s abomasum. This delay could possibly allow the resident clostridia in the abomasum enough time to ferment available carbohydrates (re: milk lactose), which causes its population explosion, excessive gas and finally, bloat. Since cow’s milk has a natural osmolality (280-290 milliomoles/litre, mOsm/l — number of particles per litre) similar to that of blood; it usually does not lead to this abomasal unbalance.
This doesn’t mean dairy producers should abandon using milk replacer for feeding pre-weaned calves in favour of feeding whole milk in order to avoid abomasal bloat. More research has demonstrated dairy producers should only avoid feeding mixed milk replacer solutions of greater than 600 mOsm/l, as the risks of abomasal bloat significantly increases. Since, osmolality is the density of particles in solution; milk replacer powder should be weighed on a scale and mixed into water as per rates of 120-130 grams per litre of total milk replacer solution, which is similar to cow’s milk.
A good consistent mix is important too, so it also becomes a matter of spending adequate time to ensure this easy-to-follow mixing recommendation is followed every time that milk replacer is mixed. When most high-quality milk replacers are fed in this manner, osmolality of the final milk replacer solution is almost guaranteed to be under the dangerous threshold leading to abomasal bloat.
Now it becomes a matter of feeding milk replacer in a well-balanced calf-feeding program. Encompassing suggestions that help reduce abomasal bloat in pre-weaned calves are:
- Make sure colostrum is fed to newborn calves and afterwards provide milk replacer or whole milk at 2.5-4.0 litres per calf per feeding (twice a day) at approximately the same times (am/pm) each day.
- Start to feed a high-quality dry calf starter to calves at two to three weeks of age.
- Lastly, assure that extra clean water is provided in addition to milk replacer or whole milk feedings.
Aside from implementing such good bloat-prevention procedures, one should also talk to their veterinarian and discuss the best means of treating abomasal bloat discovered while walking along the calf hutches or pens. It might be a sporadic, fast-acting and often fatal disorder of young pre-weaned calves, but every animal saved is another possible high-producing and profitable milk cow of the future.