Group pens after weaning: Is there a "right" way?

By Roy Williams, DCHA Leadership Class Member

Most dairy research scientists as well as dairy operators agree that calves that are weaned and moved from individual pens to group pens experience stress that makes the calf more likely to become ill than it would if those stresses did not exist.

One of the practices that is generally followed is to move calves from individual pens to groups of 4 to 8 calves, then move them to somewhat larger groups, and perhaps move them to still larger groups as they age. This practice is based on the belief that the calf will suffer less stress with the step-wise increase in group size than it would suffer if it is put in a large group pen directly out of the individual hutch or crate. However, these assumptions may not be correct.

Extensive and numerous research efforts have shown that many biochemical changes occur in the body of a calf that is subjected to any type of stress. Typically, these stress-induced changes cause the calf to be more likely to develop some type of disease. Events and conditions such as weaning, transportation, being moved to a new pen, being grouped with calves with which it has had no previous contact, a change in feed and new objects in its environment can all cause stress. Research has also found that the stress of the event lasts for one to two weeks, and, during this time, the calf's immune system is compromised, making it more likely that the calf will get sick. Biochemical and immunopathology research has shown that the mucus lining of the respiratory system - the body's first defense against respiratory disease - undergoes significant changes in response to stress, which may help explain why calves are so likely to get respiratory disease.(1)

Thus, each time we move the calf to a new pen, we subject the calf to a period of one to two weeks in which its ability to resist disease is weakened, while at the same time it may be subjected to disease organisms to which it has not previously been exposed. If we move the calf three times, then each time we move the calf the same increased susceptibility to disease occurs. If the calf stays in the same physical pen, and unfamiliar calves are moved into the pen, a less severe stress response occurs.

Repeatedly regrouping calves is not only labor-intensive, but you may not be improving your chances of having disease-free calves: (a) you are repeatedly stressing your calves, and (b) if you have a disease in one pen, by regrouping you may move the disease to another, larger, group of calves.

Reference
1. Mitchell, Clark, Siwicky, et al. Stress alters the cellular and proteomic compartments of bovine bronchoalveolar lavage fluid. Veterinary Immunology and Immunopathology. 2008; 125: 111-125