There were numerous presentations related to animal behavior at the recent joint meeting of the American Dairy Science Association and the American Society of Animal Science. Many focused on calves.
Research from the University of Guelph provided some insight into lying times of calves through the time of weaning. In one study (Ollivett et al.), lying times were compared for healthy calves and calves that developed respiratory disease over a 4-week period beginning at 10 days of age. Calves spent an average of 20.6 hours each day lying down, that"s 86% of the day. Lying time decreased 4 ± 1 minute each day as the calves grew older. In addition, calves with a fever had lying times that were 44 ± 14 minutes greater than healthy calves.
In a second study (Overvest et al.), calf behavior was monitored during three periods: 30 to 39 days of age (before weaning), 40 to 49 days of age (during weaning), and 50 to 56 days of age (after weaning). Calves spent approximately 18 hours a day lying down before weaning, 17 hours during weaning, and 16 hours after weaning. In another report, researchers from Texas A&M (Friend et al.) observed that during heat stress calves housed in hutches increase the amount of time spent lying down to avoid hot air near the top of the hutches.
A large part of a calf"s daily time budget is spent lying down, therefore the resting surface plays an important role in maintaining calf health. Effort spent to provide adequate resting space with a clean, dry surface and ventilation that removes ammonia near the bedding surface will be rewarded with healthier calves.
Guelph researchers recommend that group housing system designs include resting space that enables all calves to lie 75 to 85% of the day. In cold weather, the resting surface should not contribute to heat loss, and deep straw may be used to provide nesting sites that increase insulation. During hot weather, bedding hutches with inorganic material such as gravel or sand may help to keep calves cool because some body heat will be transferred to the bedding. Understanding the amount of time that calves spend lying down should make it obvious that maintaining calf pens is not a "minor" task on the daily list of chores. In addition, attentive calf managers may be able to use changes in lying behavior to identify sick calves early.