This winter was one of the warmest we’ve experienced in the past several years. While the nice weather has advantages, these conditions also can be stressful for calves and heifers. Increased ambient temperatures during the day, increased humidity and cooler nights have clear impacts on heifer performance and health.
Ventilation requirements
The goal of any calf or heifer ventilation system is to provide enough air exchanges per hour without creating a chilling draft. Managing ventilation is challenging in the spring and fall with fluctuating temperatures.
In the winter, the minimum ventilation rate is four air changes per hour, which is often achieved utilizing a positive pressure tube system for calves and younger heifers. As the temperature increases so does the required ventilation rate. In mild spring and fall weather, a target rate of 15-20 air changes per hour is recommended. In summer months, it rises to 40-50 air changes per hour. This can be achieved by opening the sidewall curtains in stages in naturally ventilated barns.
Early spring is also a good time of year to perform regular maintenance on curtains, fans and positive pressure tubes. Also check eaves, soffits and weatherhoods for debris to ensure these systems perform efficiently and effectively.
Inconsistent dry matter intakes
Cold temperatures generally increase intakes. Conversely, intakes will often decrease when warmer temperatures follow a cold spell. Fluctuating temperatures and humidity often lead to variable intakes, making it difficult to evaluate the feed bunk and predict intakes.
In turn, variation in energy intake and nutrient supply impacts feed conversion efficiency. In heifer systems, where grain and hay are fed separately, producers are likely to see lower forage and higher concentrate intakes since heifers that are marginally hungry will typically have lower voluntary intakes.
Health challenges
Changes in feeding behavior and feed intake are typically the first signs heifers are feeling the stress of environmental change. Decreased or variable intakes may increase coccidia shedding, which can lead to exposure to other calves, especially in high-risk environments like wet bedding. Disease challenges in the digestive tract have been linked to higher risk for decreased respiratory health.
Higher daytime temperatures in the spring result in thawing of bedding packs and increased bedding moisture. With plenty of moisture and organic matter, microbial activity accelerates and ammonia concentration increases. This change can irritate the respiratory tract and increase risk of respiratory disease, especially in enclosed facilities where ventilation is not adjusted. Increased humidity also increases the risk for airborne pathogen transfer as pathogens can travel further on moist air.
All these factors make spring a good time to work with your veterinarian to review vaccination protocols to make sure heifers have optimal protection from respiratory disease-causing organisms.
Additional management considerations
Although this past winter was significantly milder than the previous year, heifers developed a thick winter hair coat. It may not always be practical to remove this winter coat, but some farms have installed brushes to assist with long hair removal in the spring.
Heifers with wet, dirty and matted hair coats will require significantly more energy to stay warm than animals with clean, dry coats. Increase bedding frequency and amount to maintain a clean and dry bedding pack. Box-scraping outside lots can also be helpful through the spring mud season.
Managing calf and heifer environments can go a long way in promoting youngstock health and performance. Finally, remember that energy demands increase when environmental quality decreases. Work with your nutritionist to ensure diets meet nutrient requirements.
Barry Visser is a nutritionist for Vita Plus.
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