Most calf hutches look fine from the outside. But what’s happening inside the hutch, especially at calf level, is not always as obvious.
When wet bedding and manure break down, they release ammonia. In hutches, it builds up right where calves are breathing. Even at fairly low levels, it can affect intake, growth and overall performance.
During a recent episode of The Dairy Podcast Show, David Casper, a dairy nutritionist and owner of Casper’s Calf Ranch in Illinois, explains how ammonia develops in calf hutches and what it means from a management standpoint.
Airflow is a Strength
Calf hutches continue to be widely used across dairies because they naturally provide strong ventilation and keep calves in individual spaces that are easy to manage. They also offer flexibility as herds grow and do not require the same level of infrastructure as enclosed barns.
“In my opinion, the hutch would still be the gold standard as far as having the best environmental quality you could have, especially air quality, and not have to deal with ventilation problems,” Casper says.
Even so, ammonia can increase as bedding becomes damp. By the time it’s noticeable, calves have already been exposed.
“When we started using soy hulls, I started noticing ammonia in the hutches,” Casper says. “I could smell it and really picked up on it. And that’s when we started getting concerned.”
That realization prompted a closer look at ammonia levels in hutches and how they relate to calf growth and health.
Measuring Ammonia
To better understand the issue, Casper evaluated ammonia levels in 90 calf hutches. Calves were placed in alternating hutches assigned to either a control or treatment group, and ammonia was measured weekly.
“Once a week, we come through with a personal ammonia detector that’s digital, and we would turn that with the measuring system face down on the bedding,” he says. “After 30 seconds, you get a stable reading, and that was the ammonia reading in the hutch.”
Control hutches averaged about 10 parts per million, while treated hutches averaged around 1.5 parts per million, an 85% reduction.
“We actually reduced the ammonia levels in the hutches by 85%,” Casper says.
That difference was significat, as performance challenges can begin once ammonia exceeds about 4 to 6 parts per million.
“Basically the range is four to six parts per million,” he says. “Above that, you will actually start seeing performance losses or performance challenges.”
Ammonia levels varied widely between hutches. Wetter bedding, scours and older calves were all associated with higher readings.
“Some hutches would have values up to 100 parts per million and other ones would be very low,” Casper says.
Ammonia also tended to increase later in the preweaning period as calves consumed more starter.
“For our studies, week seven and eight were probably the higher ammonia readings,” Casper says. “The first week had almost no ammonia readings because they’re on freshly bedded straw and fecal output is very minimal.”
Impact on Calf Growth
Lower ammonia levels were also tied to better performance. Calves in lower ammonia environments gained more weight during the preweaning period.
“We actually picked up on a growth response as well,” Casper says. “We got .14 pounds more average daily gain.”
Milk feeding remained the same, pointing to differences in intake and environment.
“The calves that were in the lower ammonia levels in the hutches ate more calf starter and had better growth rates,” he says.
Calves in lower ammonia hutches also showed greater increases in heart girth, indicating more overall body development.
Managing Ammonia in the Hutch
While most dairies are not measuring ammonia regularly, several management areas influence how much builds up in hutches.
Bedding is the biggest driver. Keeping bedding dry and well maintained helps limit ammonia. Deep straw provides insulation and absorbs moisture, but it needs to be refreshed regularly, especially later in the preweaning period.
“A calf can take a lot of cold weather if they’ve got deep straw bedding that they can nest down into and stay warm,” Casper says.
Moisture control is also important. Hutches with scours or poor drainage tend to have higher ammonia levels, so identifying problem hutches early can help target extra bedding or cleanout.
Smell is another indicator. If ammonia is noticeable when checking calves, levels are already elevated.
Timing matters as well. Ammonia tends to increase as calves get older and consume more starter, so bedding management often needs to be more aggressive in the later weeks before weaning.
A few practical hutch-specific steps producers can use include:
- Add fresh straw more often in the back third of the hutch, where moisture tends to build first
- Pull wet bedding away from the calf’s resting area instead of just layering on top
- Pay close attention to hutches with scouring calves and re-bed them first
- Check bedding depth at the calf level, not just at the front entrance of the hutch
- Clean or fully reset hutches between groups when possible to reduce carryover moisture
Paying attention to these areas can help keep ammonia levels lower and support more consistent calf performance through the preweaning period.
