Case summary: A seven-day-old layer flock experienced a sudden mortality spike, with neurological signs and watery droppings – symptoms of a relatively common nutritional condition. This case highlights the importance of balanced nutrition and proper management in brooding to prevent unintended harm.
Case history: I was called to a free-run layer farm to investigate unusual chick mortality in a seven-day-old layer flock imported from the U.S. to British Columbia. The chicks had been thriving until day six, when mortality spiked to 0.8 per cent, with about 40 chicks found dead throughout the barn. The producer also reported that a few chicks were displaying twisted neck and head tremors before death.
Postmortem and field evaluation: As per routine investigation, before entering the barn, I performed postmortem exams on fresh mortalities. The chicks had good general body conditions, proper hydration, and evidence of normal feed intake, with no signs of yolk sac infection or bacterial septicemia. However, all the chicks had pasty vents, dirty toes covered in feces, and mild abdominal edema.
The barn’s brooding conditions – temperature, feed and water access, litter, air quality, and sanitation were within normal limits. During the barn walk through, I observed more sick chicks showing neurological symptoms, including stargazing (chicks with the necks bent backward) and mild head tremor. What also struck me was the watery droppings on the chick papers and the high numbers of chicks with wet, pasty vents.
At this point, the mix of acute onset of neurological signs, mortality, edema, wet droppings, pasty vents, and the absence of infectious disease indicators suggested sodium toxicity. My first inquiry was about the feed. After verifying that another flock at a different farm consuming the same batch of feed did not display similar symptoms, a feed error became less likely.
The culprit:After digging into the flock’s history, I found that the flock had been supplemented with an electrolyte premix via drinking water since they were two days old. The producers added the water supplement due to prolonged transit time before arrival, intending to give the flock a nutrient boost. While electrolyte or vitamin premixes may be helpful during stressful periods such as prolonged transportation and overheating, in this case, the flock was accidentally given five times the labelled dose for an extended period. This overdose led to salt toxicity, with young chicks being particularly susceptible to sodium imbalance. It is important to note that although older birds are generally less susceptible to salt toxicity, it can still cause significant chronic issues. In breeder males, for example, salt toxicity can impact fertility, lead to testicular edema, cause muscular weakness, and result in wet litter.
Management plan and clinical outcome: Once the electrolyte supplement was discontinued and the water line flushed, the flock improved quickly. By the next day, they were more alert, and mortality tapered off over the following three days, with no further reports of wet droppings or neurological symptoms reported. I also collected and submitted some tissues and blood samples to the laboratory to help rule out other causes, including avian encephalomyelitis, a viral disease that may present similar neurological symptoms in young chicks.
Lesson learned:
- Proper use of electrolyte and vitamin premix: Quality poultry rations typically provide sufficient nutrients, making additional supplementation unnecessary under normal situations. When water-soluble electrolyte and/or vitamin premixes are used due to anticipated health concerns, they should be used cautiously, and dosing should always follow label instructions. Always select a product labelled for poultry use. Overuse or improper dosing can lead to salt toxicity, especially in young chicks.
- Signs of salt toxicity: Watch for early clinical signs, including excessive drinking, pasty vents, and watery droppings. Neurological symptoms, such as head tremors or ataxia, may occur in acute, severe cases.
- Feed and water sources: While this case was due to a water supplement overdose, feed mixing error or mechanical malfunctions at the feed mill are other potential sources of salt imbalance. When in doubt, conduct feed and water analyses and remove suspect feed from the system until confirmed safe.
Dr. Gigi Lin is a board-certified poultry veterinarian. She provides diagnostic, research, consultation, continuing education, and field services to all levels of the poultry industry in Western Canada. In this column, she will share case-based reviews of brooding best practices.