Minimising Abomasal Bloat In Your Calves

Abomasal bloat is a condition seen sporadically in groups of young calves being fed whole milk or milk replacers which is characterised by gaseous overdistension of the abomasum.

The predominant clinical sign consists of a calf, or several calves, with a distended abdomen, usually within 2-3 hours of feeding. This is often accompanied by the characteristic signs of colic, such as kicking, stamping, glaring at their sides, teeth grinding (‘bruxism’), difficulty breathing (‘dyspnoea’), and unfortunately in some cases, a rapid death.

Any calf rearing enterprise which has experienced this condition will know that in many cases a clear-cut cause is not always evident. However, this post will delve into some helpful mitigation strategies which can be employed on farm to minimising the chances of it happening in your calves.

It is common knowledge that ruminants have four stomachs, namely the Reticulum, Rumen, Omasum, and Abomasum. However, only one of these is functional in early life – ‘the true stomach’, called the abomasum. It is this stomach which we will be focusing on here. If you remember when a calf suckles whole milk or milk replacer this diet is diverted directly to the abomasum via the oesophageal groove as a result of a distinctive reflex. However, the abomasum is not renowned for its capacity to expand. Hence, why this condition can present quite dramatically.

The first question we should ask ourselves: What is driving this gas production? After all, the abomasum is not responsible for any diet fermentation and therefore gas production should be minimal. Instead, this stomach degrades dietary components by secreting hydrochloric acid (HCl) and hosting a range of enzymatic reactions.

Precision Microbes offers a unique liquid probiotic and postbiotic solution specifically designed to stabilise gut flora and enhance digestive health in calves. The product acts rapidly, with postbiotic components working quickly to restore normal gut function. Its liquid formulation allows for easy administration, whether given orally or mixed with milk. It is also compatible with other treatments, making it safe to use alongside antibiotics and rehydration therapies. The dosing is flexible and can be tailored depending on the calf’s age and the severity of symptoms, making it a practical and effective tool for managing gut health during critical periods like weaning.

The production of gas within the abomasum is highly suggestive of an inappropriate microbial fermentation occurring within this stomach. Most frequently it is Clostridial species and Sarcinia Ventriculi which are implicated. If this is the case: Where do these unwanted microbes come from?

The immediate calf environment is teeming with microbes, including these unwanted pathogenic forces. Therefore, optimising hygiene around calf feeding is the first area of focus. Remember, this is frequently a numbers game.

1. Feeding Equipment: Whole milk and milk replacers are nutrient dense feed materials (i.e., rich in lipids, sugars, and proteins) which can allow pathogens to thrive if nutrients are allowed to stagnate in low flow areas of feeding equipment. The longer feed material is left behind the higher the probability of microbial multiplication, biofilm production, and spore formation. Manual calf feeders should be rinsed with warm and clean water, then an appropriate detergent used to efficiently remove feed materials. This equipment should then be soaked in a disinfectant to kill any residual microbes (such as dilute peracetic acid solution) and then allowed to drain for drying between feeds. Automated calf feeders should have a detergent wash used 2-3 times per day and an acid wash used 1-2 times per week, dependent on the hardness of the water used.
2. Water Supply: This includes the supplies for milk replacer mixing, for washing feeding equipment, and for water drinkers. The goal here is to always use clean water, which can be assisted with water filters and/or ultraviolet light. Always ask yourself what other areas of my farm receive the same water supply (i.e., milking parlour) and am I having issues here (i.e., mastitis)? If header tanks are used these should be cleaned out regularly, especially at the start of any concentrated calving season.

Now we must ask: How are these pathogens surviving the low pH of the abomasum in my calves? The ideal abomasal pH is around 2.0 as this acts as an inherent defence against pathogens coming in via the oral cavity and this also promotes efficient digestive processes. This is where our second focus area should be – feeding strategy.

1. Milk Volume Per Feed: When calves are consuming large quantities of milk rapidly the abomasal pH may rise, which risks the effectiveness of digestion and this innate defence. This may occur on farms with large groups of calves with significant competition at the level of the calf feeder, which promotes engorgement. This is worsened if there is sizeable variation in the age and weight of calves in the same group on communal feeders. Conversely, if calves are hungry and not receiving 13-15% of their bodyweight in milk/milk replacer daily they may remain at the feeder ‘suckling free air’ which may exacerbate the issue. These issues may be amplified at the transition from twice-a-day feeding to once-a-day feeding.
2. Milk Concentration: One of the benefits of using milk replacers is that it offers consistency with milk concentration, once mixed correctly every time. This is opposed to whole milk which may vary in nutrient density daily, depending on which cows are feeding calves and their stage of lactation. The goal is to mix milk replacer at 125g of powder into 875ml of clean water for each litre made up (i.e., 375g powder in 2625ml of water for a 3L feed). This is important because a high concentration (known as osmolality) can slow the emptying of the abomasum. Note that the osmolality of marketed milk replacers can vary significantly dependent on the ingredient list. For example, the ash content and protein source can influence osmolality greatly. Aim to provide a milk replacer utilising high quality milk-derived proteins and an ash content <8%.
3. Feeding Equipment: Calves love consistency and you must aim to ensure milk feeding occurs at the same height (especially for milk bars), at the same temperature, with a clean teat with an appropriate outflow every single feed.
4. Delay To Feeding: This may be an issue if whole milk or milk replacers are left following milking or mixing. If this period is protracted pathogens present in the milk or the mixing bucket can proliferate.
5. Mastitis Milk Feeding: A reem of pathogens can be present in whole milk harvested from cows with intramammary infections (seen as clinical mastitis or high somatic cell count). This milk should not be fed to calves, especially if farms have experienced abomasal bloat, neonatal calf enteritis (‘scour’), or bovine respiratory disease (‘pneumonia’).