The amount and timing of electrolyte replacement therapy is critical for rapid recovery from dehydration. A common mistake is waiting too long before administering electrolyte solutions to affected calves. Giving fluids too little, too late allows progressive fluid loss. As a result, the calf’s condition continues to deteriorate. Most calves that die of scours usually die from loss of water and electrolytes, not from direct action of pathogenic organisms. The focus of any treatment plan should be on replacing lost fluids.
Good candidates for oral rehydration therapy are those calves that can stand and suckle. Weak calves with a poor suckle reflex may need to be tube-fed. Calves that have lost the suckle reflex and are recumbent and unable to rise, are poor candidates for oral rehydration therapy. Subcutaneous and/or intravenous infusions are indicated in more advanced stages of dehydration. The calf's ability to recover declines as the severity of dehydration increases
The amount of supplemental fluid a scouring calf needs each day depends on its rate and degree of dehydration. Instructions found on electrolyte packaging are general and don't really describe what specific calves needs for rehydration and recovery. So it helps to have a basic understanding of what a scouring calf needs.
It's safe to assume that a calf with diarrhea and no other visible signs of dehydration is about 4-5% dehydrated. If the calf weighs 100 lb, it needs to receive 4-5 lb of water to recover the water it has lost.
100 lb calf x 0.04 = 4 lb; 100 lb calf x 0.05 = 5 lb
easy to calculate for a calf of any weight
Since a gallon of water weighs about 8 lbs, a quart of water weighs 2 lb. To replenish lost fluids, this 100 lb calf needs to consume at least 2 quarts of electrolyte solution. This is the amount of electrolyte solution that would be administered each day to this calf until it improves.
Keep in mind that this calf became 4-5% dehydrated while it was drinking its regular milk/milk replacer feedings. This means the calf needs the 2 quarts of electrolytes in addition to the liquid nutrition it normally receives, not instead of.
If the calf shows additional signs, such as sunken eyes, depression, tight skin (skin tents when pinched), or water-like diarrhea, it may be 7-8% dehydrated and in need of additional electrolyte feeding. The table below summarizes daily electrolyte requirement for 100, 80 and 60 lb calves.
Another way to look at this is that a calf with diarrhea and no signs of advanced dehydration requires treatment at the 5% dehydration level. Calves with water-like diarrhea or other clinical signs of advanced dehydration are likely losing water at a higher rate and would benefit more from treatment at the 8% dehydration level. Calves that are 10% dehydrated may not be good candidates for oral rehydration therapy, and usually require other methods of administering supportive fluids such as intravenous administration.