Ontario Beef Magazine

December 2017

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Gut Aches and Grain Gorging

By Katharine Found, DVM, Kirkton Veterinary Clinic

It was complete carnage! I was only a few weeks into my career as a veterinarian when the phone call came in “Send someone quick, everything’s dying!” I rushed to the farm only to find four dead calves and three more down and not looking particularly healthy. A gate had accidentally been left open the night before and this particular group of 600 lb calves decided to venture out, knock over the grain cart and consume more than their fair share of the ground corn that was meant to last a few days and not just a few hours.

Grain overload is a result of animals consuming a large quantity of grain in a short period of time, especially when they are not accustomed to the feed. The grain releases carbohydrates quickly into the rumen, which ferments rapidly rather than being digested normally. Due to the fermentation, bacteria in the rumen produce lactic acid. This lactic acid build up lowers the pH of the rumen which decreases the number of good rumen bacteria and causes rumen contractions to slow and even stop. Lactic acid draws fluid into the rumen from the tissues and blood which causes rapid dehydration. And in severe cases, the animal’s blood may become more acidic, resulting in organ failure and death.

For animals that don’t die suddenly, the lactic acid build up in the rumen can cause severe damage to the rumen papillae, which are the finger-like projections on the rumen wall that assist with nutrient absorption. This rumenitis allows bacterial and fungal pathogens to enter into the body and can result in liver abscesses and abdominal infections for up to a week after the initial grain poisoning. Laminitis and severe, painful lameness may also be seen in animals that survive the initial insult. Most of these survivors become poor doers, or have significant welfare concerns and euthanasia is sometimes the most appropriate course of action.

Grains with higher fibre content are less likely to cause grain overload, since the fibre slows the rate of digestion. Alternatively, cracking, rolling or grinding the grain increases the rate of digestion of the carbohydrates and consequently may increase the risk of causing grain overload.

Any factors that cause variation in the amount of grain consumed or variation in the availability of carbohydrate may also lead to grain overload. For example, inclement weather may put cattle off their feed for a day, but the following day they gorge. Or animals are fed more than their normal ration because it will make chores easier on a busy weekend, but the cattle don’t get the memo that they are supposed to ration the portions appropriately and they gorge. Both are common causes of grain overload, despite the animal’s eating the same ration they are used to.

The severity of the signs of grain overload will depend on the quantity of grain eaten and the degree of adaptation of the animal to that grain, and clinical signs usually do not develop until 12-24 hours after the grain consumption. Mildly affected animals will have a reduced appetite and may appear quiet and depressed. Abdominal pain is often present so the animal may be getting up and down or kicking at its abdomen. Diarrhea is also a common sign of mild acidosis.

More severely affected animals will show profuse diarrhea of pale, smelly feces. If a whole grain was consumed, these grains may be present in large quantities in the diarrhea. Heart rate and respiratory rate will increase and the animal may bloat due to slow or ceased rumen contractions. Animal’s may go down and not be able to stand. At this point prognosis is very grave and animals usually die within 24 hours.

If the likelihood of poisoning is considered high and the animals are close to slaughter weight, emergency slaughter should be considered as a potential treatment. This is only an option if adverse symptoms have not appeared, because meat quality will be negatively affected once signs of acidosis develop, and the animal will quickly become unfit for transport.

Aggressive treatment therapy must be initiated immediately for all episodes of grain overload where clinical signs are observed, but in severe cases, prognosis is always guarded at best. The treatment plan will vary based on the severity of the clinic signs, but often includes removing all grain and offering the animal only high quality hay. Intravenous fluids will be used to rehydrate the animal and a bicarbonate drench should be administered to increase the pH of the rumen. Anti-inflammatories are used to control pain and inflammation and intraruminal antibiotics can be administered to prevent bacterial overgrowth in the rumen. Surgery can also be an option in very acute individual cases, where clinical signs have not started. Your veterinarian will remove the rumen contents and may try to replace it with healthy rumen content from a donor animal. This is called transfunation.

Following grain overload if the animal survives, the rumen lining takes up to six weeks to repair, so recovering animals will show poor growth rates during this time. As such, prevention is important. Cattle should receive a minimum of 10-20% roughage in any ration and always transition cattle onto grains gradually to ensure the animal’s rumen has sufficient time to adapt. If cattle are being turned out onto grain stubble, it is recommended to feed some grain beforehand, to prepare the rumen bacterial population.

The addition of an ionophore, such as rumensin, to the ration can help to prevent grain overload, as they modify the rumen bacteria to decrease the amount of lactic acid produced. Sodium bicarbonate can also be included in grain-based rations to help prevent drops in rumen pH. Feed additives only help when all other feed practices and programs are appropriate for cattle.

Grain overload episodes must be taken seriously and need to be acted on very quickly – don’t wait and see if signs show up. For best results, be aggressive and administer therapy. It’s better to be safe than sorry!

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