Sometimes the best of intentions can lead to unintended consequences. Such was the case for one Wisconsin dairy that experienced a rash of illness and deaths in its young dairy calves.
When University of Wisconsin veterinary researchers Theresa Ollivett and Sheila McGuirk were called to the case starting in November, the 500-cow herd had lost 90% of its newborn calves before two weeks of age over the previous 4 months. In total, 85 calves had died.
The clinical signs displayed by the calves before death included anorexia, diarrhea, lethargy, abnormal gait and seizures. Some calves also displayed signs of respiratory disease, including nasal and eye discharge, fever and cough. Initial disease investigation showed no evidence of acute disease pathogens such as BVD, salmonella or E. coli.
Further evaluation of preweaned-calf-feeding practices on the farm eventually lead Ollivett and McGuirk to diagnose salt poisoning in the herd. The circumstances that led to excess salt intake included:
- The farm had experienced problems with its well. As a remedy, the depth of the well had been increased, and 400 gallons of sodium hypochlorite had been added to the well water supplying the calf barn to improve water quality. Testing showed extreme salinity in the well water that was being used to mix calf milk replacer. The salt content of the farm’s water was found to be 7,100 ppm; safe level is 1,000 ppm.
- Free-choice water was not offered to calves until 4 weeks of age.
- The owner was adding extra milk-replacer powder to the calves’ liquid diet in an effort to provide additional nutrients heading into winter.
- As calves became sick, attempts at treatment included adding electrolyte powder to the liquid feed, and supplementing with lasalocid (which already was in the liquid feed from the milk-replacer manufacturer, and is high in sodium).
As calves began to scour, loss of water further contributed to high blood-serum sodium concentrate, or hypernatremia. Ollivett explained that hypernatremia can lead to central-nervous-system disorders because neurons effectively shrink and lose function as water is lost.
In this particular farm’s case, the epidemic was quickly resolved by (1) switching from milk replacer to whole milk; (2) rectifying the farm’s issue with sodium in the well water; (3) offering free-choice water much earlier in life; and (4) mixing electrolyte powder with water and feeding it to sick calves separately, versus adding it to the liquid feed.
Ollivett said this farm’s lessons are instructive to everyone raising calves. Her advice:
- Monitor sodium levels in the water used to mix milk replacer, and do not used softened water.
- Offer free-choice water starting in the first week of life.
- Reconstitute electrolyte solution separately; do not add electrolyte powder directly to milk or milk replacer.
- Work with a nutritionist to determine feed-additive levels and modify rations according to environmental conditions.
To learn more about this case and other on-farm incidences in which salt poisoning has occurred, read the full case study from the Journal of Veterinary Internal Medicine.