Enteric System: Post-Weaning Pigs
Intestinal torsion and hemorrhagic bowel syndrome (HBS) typically affect pigs between four and six months of age. Both are sporadic but ubiquitous and can occur any time of the year. Intestinal torsion is more commonly seen in US herds. Their primary symptom is sudden death, so they can cause major economic losses.
The entire intestinal tract of the pig is held in the abdomen by a loose set of connective tissue. Torsion of the intestine usually occur when the pig exercises after a meal, with a full gut. Pigs are social animals and play together when housed in groups. After the first cut of finishing pigs is sent to market, the remaining ones suddenly have more space to run in the pens increasing the risk of torsion. The torsion and the following dilatation of the intestines pinch mesenteric veins and prevents the blood from returning to the heart. Poor venous return associated with hypoxia due to increased pressure on the lungs, lead to a quick death.
In the case of HBS, the cause of the sudden death is identical. However, no torsion is found at necropsy. Until now, highly fermentable rations such as liquid feed or rations including whey have been most often associated with clinical cases of HBS.
Most common sign is sudden death, often overnight in both cases. In the rare occurrences when the pig may live long enough to observe clinical signs, abdominal pain, vocalization, difficulty to move, and pallor can be seen. Diarrhea is uncommon.
In both cases, the main macroscopic lesion is blood-filled, distended intestines. This is usually accompanied by thinning of the intestinal walls. In cases of intestinal torsion, a counterclockwise rotation, along the longitudinal axis can be found. This means that at necropsy, organs will be displaced instead of having the jejunum on the left hand side and the colon on the right.
What is the main clinical sign associated with intestinal torsion and HBS?
- Sudden death
- Bloody diarrhea
Congestion is the most common microscopic lesion seen, with mucosa and the intestinal wall most likely being affected. Necrosis of the mucosa can also be present.
Intestinal torsion is diagnosed by finding the part of the intestine that has been twisted.
However, the diagnosis of HBS is done by eliminating all other causes of blood in the intestine. Differential diagnosis includes Intestinal torsion, ulcer, hemorrhagic ileitis, and swine dysentery.
Differential Diagnosis for HBS
Gastric ulcers are also part of the differential, but necropsy should reveal characteristic lesions in the pars esophagea, as well as lack of bloating in the abdomen. Proliferative Enteritis also produces similar clinical signs, but the intestine is not nearly as damaged and diarrhea is commonly seen. No torsion of the intestine can be found.
Which population is more at risk for HBS?
- Finishing pigs after the first cut is sent to market.
- Sows after they farrowing due to the change of size of the uterus.
- Pigs fed liquid feed in a trough.
Treatment, Prevention and Control
There is no way to treat those two diseases, as it usually kills the pig before treatment can be applied. For a herd afflicted by HBS, the best course of action is typically to assess the diet of the pigs and make the necessary changes such as smaller meals or decreasing the amount of whey in the ration. Lowering stress of the herd is often the best prevention method against this disease. Management practices such as preventing out-of-feed events and avoiding mixing of pigs will typically be enough to prevent HBS.