As swine veterinarians, we always strive to help provide the best care possible for the animals. I enjoy taking new clients through the Pork Quality Assurance Plus program because I find that most of them want to meet (and often exceed) the recommendations for swine care. Occasionally, however, we make mistakes in our efforts to do things right and we do harm. The key is to identify these situations quickly and fix them.
Case Study No. 1
If a producer “googles” mulberry heart disease (MHD), the first link describes it as a vitamin E deficiency problem. Pigs fed low levels of vitamin E will develop clinical signs of MHD, which includes stiff staggering, paralysis, recumbency and acute death. It is most common in 15-25-lb. nursery pigs. Postmortem results reveal petechial (dark spots) and white streaks in the heart muscle, clear fluid in the pericardium (heart sac) and blood in the abdomen.
Our first thoughts are either the diet is deficient in vitamin E or the vitamin E was past its shelf life. Our first line of defense is to ensure the vitamin premix stock is not out of date (more than 90 days) and raise vitamin E levels to stop clinical signs.
Recent studies outline the possibility of iron toxicity as a cause for MHD. Injections of iron dextran for prevention of anemia are standard practice in the swine industry. Piglets are commonly injected intramuscularly with 200 mg iron at processing. In one study, the data was fairly clear that 200 mg iron was toxic to the genetics line in question. The study showed a decrease from 0.8% death in the first week postweaning with clinical signs of MHD to 0.2%. A second study was designed to determine baseline iron values across eight lines within one genetics company. The conclusion was 100 mg iron at processing was enough to achieve normal blood values without the risk of toxicity.
Many hog farms use 200 mg iron and probably get along just fine. But if MHD has been a clinical problem in your operation, you might consider lowering the injectable iron level. Remember, do no harm.
Case Study No. 2
Another case involved accidental selenium toxicosis. A farm reported pigs were off feed. Initially, it was thought to be a mycotoxin issue, so feed was tested and bins were emptied and refilled using a different grain source. Diagnostics were also submitted to rule out porcine reproductive and respiratory syndrome (PRRS) and swine influenza virus (SIV), as the herd was thought to be negative and non-clinical, respectively.
All results were negative, yet pigs continued to eat very intermittently, and performance was poor. Two nursery pigs had central nervous system signs not typical of the streptococcus meningitis infections seen on occasion. These pigs were quadriplegic, yet very aware of their surroundings.
Through diagnostic laboratory submissions, a lesion in the spinal cord was found indicative of selenium toxicosis, confirmed by testing liver and kidney values. Feed testing revealed the mineral premix used was 10X the label value.
The good news was we had a diagnosis. The bad news was damage was already done and we had to figure out a way to set things straight. In the end, 17 pigs were euthanized due to severe lameness, paralysis or separation of the hoof wall. An additional 31 pigs were treated for moderate lameness issues and were eventually marketed. Decreased rate of gain was seen across the system in growing pigs, and the breeding herd suffered about a 10% reduction in farrowing rate.
We implemented a plan to feed a complete feed with no added selenium until serum levels of selenium returned to normal. We did not want to let the pendulum swing the other way and cause a selenium deficiency. It took almost 90 days for serum levels to return to normal.
When unexpected results occur, reassess your protocols and ask the right questions. In the case of MHD, field trials should be done to assess what the appropriate iron levels are for the type of pigs that you are raising.
The case of selenium toxicosis reminded me of the importance of good observational skills, rapid action in submitting diagnostics and the value of an excellent pathologist.
As veterinarians, we are constantly looking for new ways to help our clients produce a safe and wholesome food product as efficiently as possible. We strive to serve the best interests of the animals and above all, do no harm.