While it may feel like winter, positive thinking reminds us that summer is just around the corner.
On my home farm, it seems to be more challenging to keep calves healthy and growing in the summer than in the winter. Some studies comparing summer to winter calf growth show calves actually grow better in the winter.
My problem with summer is keeping calves cool and eating.
This past summer, we conducted a trial in two locations to look at reflective covers to keep calf hutches cooler.
The product we tried was the cool calf cover, which is designed to reflect heat off the hutch, helping keep calves cooler. Our trial recorded temperatures one inch from the top of the calf hutch for a 60-day period.
Temperatures averaged 2 degrees cooler with the covers from 11 a.m.-3 p.m. but had a higher relative humidity.
During the night, hutches stayed a degree warmer with the covers than without, but relative humidity was lower in the covered hutches.
From our trial, the cover did perform similar to the trials conducted in southern states but didn’t show as large of temperature difference.
A Texas study showed a 6-10 degrees difference between the covered and uncovered hutches during 90-100 degree days. In our study, we averaged 25 days with temperatures over 90 degrees.
While reflective covers may help lower temperatures several degrees, on the hottest days there are several other important factors to consider which will help improve calf health.
The first important number to remember is 79 degrees Fahrenheit, this is the temperature that calves start to experience heat stress and will need more energy to maintain growth above this temperature.
Some signs of heat stress include calves that decrease intake, consume more water, are lazy and don’t come see you when you walk in the barn at feeding time, are panting, breathing heavy or are mouth breathing.
The first step in heat stress management is to make sure calves have access to cool (50-60 degrees) clean water. Water should be dumped daily and fed in a separate bucket from the milk.
A study from Pennsylvania showed a .15 pound/day rate of gain advantage by dumping buckets daily compared to weekly.
If buckets were dumped every two weeks, mold and bacteria levels were higher in the bucket and more calves’ required medical treatment.
Clean buckets encourage increased starter intake. While starter feed should be fed ad lib, be careful not to over fill pans.
Some studies show daily dumping of feed refusals increases average daily gain.
Calves naturally eat less starter when they are hot. Feeding only a small amount in the bucket at a time so that it is almost cleaned up each feeding has been shown to increase starter intake, helps to keep the feed fresh, and decreases wasted feed that gets wet.
The next step is housing adjustments. Calf hutches can be propped up about 7 inches in the back to allow for better air movement in the hutch without calves escaping.
This has been shown to reduce bacteria levels inside hutches and reduce carbon dioxide lowering calf respiratory rates. If you still have older hutches without large back air vent, cutting air vents into these hutches improves ventilation.
Hutches should also face east in the summer to maximize ventilation.
In a calf barn, fans can be added to improve ventilation. Fans will work best when wire panels are used between calves, while it may cause more disease transfer between calves heat stress will be reduced.
One study found that running fans during day light hours improved average daily gain by 23 percent. In this study 3 1/2-feet fans provided air to seven pens.
One other practice, which does not work as well, is to bed calves with sand instead of straw or sawdust in the summer. While it does lower calf skin temperature average daily gain decreased on sand and scours increased. This is most likely due to calves experiencing chills at night without being able to nest in the straw.
While impractical most of the time moving a hot calf to sand during the day could help with heat stress. With any bedding material, be sure to keep pens dry and cleaned out often to decrease bacterial levels and fly pressure.
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