Aug. 31 2012 06:37 AM

Calves and heifers also suffer performance losses during heat stress.

Usually out of sight in the back of the dairy, replacements are also often out of mind when it comes to providing cooling relief during hot weather. But research has repeatedly shown that younger animals suffer from heat stress, too – just in different ways from milking animals. Fortunately, many of the same techniques used to bring relief to mature cows are also effective with youngsters.

With calves and heifers, "performance" means average daily weight gain and growth, and both can suffer significantly when heat stress hits. Shade, ventilation and more fresh drinking water are keys to helping reduce its effects. Perhaps surprisingly, so is more feed.

This may sound odd, since more feed means more calories and more calories means more internal heat produced by young animals. But more calories are what they need in order to fuel the increased respiration that they use to help dissipate internal, conductive, convective and radiant heat. Without more calories, young animals become physically fatigued more quickly.

Heat stress also reduces appetite, though, which means more energy-dense feeds may be needed to provide those calories. But getting more feed into calves can be a challenge during hot weather. Strategies to consider include feeding some or more whole milk, using replacers with higher protein content or adding whole milk powder to the mix. All are options worth discussing with your nutritionist.