Dairy calf weaning strategies
In the North American dairy industry, there is a strong belief that by avoiding contact with other calves, the calf suffers less exposure to pathogens and will therefore be healthier. However, this practice appears to subject the calf to much stress at the time it is weaned and moved to a group pen, as evidenced by many articles that have been published regarding health and weight gain issues surrounding freshly weaned calves.
The following observations suggest that the practice of maintaining pre-weaned calves in isolated pens may not be as important as first believed.
1. New Zealand dairies routinely group their newborn calves one to two weeks after birth and experience a somewhat lower death rate (five percent) than U.S. dairies (eight percent).
2. Recent experience with automated group milk feeding equipment has found that death rates have not increased when the farm switched from individual housing to group housing of very young calves.
3. In beef cowherds on pasture, the cow typically keeps a newborn calf isolated from the remainder of the herd for at most three days. After that the calf is in close proximity to other calves and cows almost continuously, yet the average U.S. beef herd experiences a death loss of about two percent after 24 hours of life through weaning (about 200 days), including losses to predators.
4. U.S.-based research has shown, in limited trials, much lower death rates and significantly lower production costs for colostrum-deficient calves raised in groups as compared to calves raised in isolated pens.
5. The Bach, Ahedo, and Ferrer study about optimizing weaning strategies of dairy replacement calves is one of the very few studies that has specifically examined the effects of weaning strategies on health; most studies have focused on short-term growth. This was a large study involving a total of 560 calves in two different experiments.
In the first experiment, calves that were moved out of individual pens immediately upon weaning at 49 days of age had one-half as many cases of respiratory disease as calves that were kept in individual pens for six days past weaning.
The second experiment compared calves moved to group pens and then gradually weaned, and calves gradually weaned and then moved to group pens; calves moved and then weaned had 60 percent fewer repeat respiratory cases. These researchers also state in their article that the practice of holding calves in individual pens after weaning is widely practiced, but "there seems to be no scientific evidence to back up such a recommendation."