by Marina A. G. von Keyserlingk and Daniel M. Weary
The authors are with the Animal Welfare Program, University of British Columbia, Vancouver, Canada.
When calves are fed more milk, weight gains before weaning are drastically boosted. This system facilitates group housing which has added benefits on the dairy when well managed.
it is best suited for farms that already have a well-managed calf program.
Calf care is possibly the most challenging job on the dairy farm, in part because milk-fed calves are most likely to become ill. But, new methods of calf rearing provide the potential for widespread improvements in calf care over the next decade.
We predict that, as calves are fed more milk, there will be a boost in the use of labor-saving milk delivery systems that facilitate more natural milk drinking behavior. These improved feeding systems will ease the transition towards group housing of calves prior to weaning, saving time and money.
However, changes in feeding and housing systems pose new challenges that require additional innovation and research. Group housing is accommodated in systems that provide greater volumes of milk, promoting rapid growth, and more natural calf behavior. Group housing, though, can lead to more competition and a greater risk of disease transmission.
Less milk, lower growth rates
Calves are normally provided milk at 10 percent of birth weight, about 9 pounds per day for an average Holstein heifer in a conventional management scheme. Additionally, they are vulnerable to disease, often fail to gain adequate weight, and can sometimes experience high levels of mortality.
We tested the effects of feeding calves ad libitum by teat. In each experiment, we compared weight gain, milk intake, starter intake, and number of days with diarrhea for calves fed milk conventionally (twice daily at 10 percent of body weight) versus ad libitum. We found that weight gains during the first two weeks after birth are typically less than a pound per day for conventionally fed calves versus about 1.8 pounds per day for calves fed milk to appetite.
It is commonly thought that feeding less milk encourages solid feed intake. Indeed, we found that, over the first five weeks of life, feeding calves less milk does hike starter consumption (0.38 versus 0.2 pound per day). But, the extra starter intake cannot nutritionally compensate for the limited quantity of milk, explaining the poor weight gains for calves fed conventionally. We have also found that ad libitum milk-fed calves quickly caught up to the conventionally fed calves in their intake of starter after weaning; both groups consumed on average 4 pounds of starter per day during the two weeks after weaning.
Additional access to milk raises practical problems, such as maintaining milk quality throughout the day, especially during warm weather. An alternate approach to continuous access is to provide unlimited availability of milk a few hours each day. Our work has shown that calves provided unlimited access to milk spend just 45 minutes per day drinking and that the largest meals occur just after milk delivery. Therefore, we looked at the effect of limited access to milk (4 hours per day divided into two, 2-hour periods) versus continuous access on milk intake, weight gain, and behavior of calves. Calves consumed as much milk in the 4-hour-per-day treatment as they did in the continuous treatment.
Current recommendations for weaning age and method are specific to slow-growing calves fed conventionally. Little is known about how best to wean rapidly growing calves fed high milk rations. New work has shown that slowly reducing milk intakes in the days before weaning provides the best transition. In one study with calves fed up to 12 liters per day, we compared calves weaned abruptly or gradually over 4, 10, or 22 days. The abruptly weaned calves had the lowest starter intake and the best weight gains before weaning. After weaning, calves on the 22- and 10-day treatments ate more starter and had better weight gains than calves on the more abrupt treatments. Our findings suggest that a 10-day weaning period is optimal.
Calves benefit from group housing
For a number of years, common convention was that calves should be housed individually, in separate pens or hutches. This practice was thought to improve performance and minimize disease. Individual housing also helps avoid behavioral problems such as competition and cross-sucking.
New feeding systems work well for individually housed calves but also facilitate group housing. Group housing provides more space for calves and allows for social interactions.
Early social interactions better prepare calves for social interactions later in life. For example, in a recent study when introduced to a group pen after weaning, calves that had previously been housed individually took, on average, 50 hours to begin feeding, in comparison to 9 hours for pair-reared calves.
Research and practical experience show that group rearing can significantly reduce labor requirements for calf care. One study on a commercial farm in New York showed that calves kept in groups required one-third of the labor compared to individual housing.
Calves are social animals, and keeping calves in groups may provide a number of advantages to both producers and their calves. However, adoption of group housing could elevate problems with disease and competition. Recent research provides some insights into how these risks can be minimized.
Successful group rearing requires appropriate management, including feeding method and group size. Surveys of U.S. and Swedish dairy farms found mortality and disease on farms rose when keeping calves in large groups (more than seven or eight). Thus, small groups are a safer option on some operations.
System design impacts health
Calf immunity and the design and management of the housing systems, such as its cleanliness and ventilation, likely affect disease susceptibility more than group housing. Our work shows that housing young dairy calves in small groups is viable in terms of calf health, performance, and behavior. We encourage producers to consider keeping groups small and physically separated from one another (in super hutches) and managing group pens in an all-in-all-out basis.
Calves in groups sometimes compete with penmates. In one experiment using a simple teat-feeding system, we found that group-housed calves displace one another from the milk teat more often if there are not enough teats. However, giving each calf access to its own teat greatly reduced displacements. Improved access to teats resulted in longer feeding times and better milk intake.
Other research has focused on how computerized feeding stations can be managed to reduce competition between calves. Raising the daily milk allowance for calves from 5 to 8 liters per day cut calves' visits to the feeder in half, reduced occupancy time and displacements from the feeder, and improved equipment efficiency.
Our research shows that young calves can be introduced into a group with little disruption when they are trained to feed from the computerized feeding station prior to introduction. Although the calves visited the feeder less frequently on the day of mixing, they were able to compensate by amplifying both the duration and amount consumed per meal, and established their premixing feeding pattern after one day.
Current research on calves is paving the way for new methods of feeding and housing that will facilitate calf care and improve living conditions for young animals. For the good calf manager, the research that we describe provides opportunities to further improve calf care and reduce labor. However, like any new method, these are best adopted first by the most competent managers. New methods require a careful eye to ensure they are implemented in the best possible way.