Healthy calves are the foundation of the future of a dairy. Raising healthy, well-grown calves can be a challenge. Research studies suggest that calf-death losses have not improved much in the past three decades. Of course, death losses are only a small part of the total losses. Just having calves that get sick carries large costs, even if they survive.
One way to try to reduce those losses is to develop tools to treat calves more effectively, by recognizing earlier than we do now, when they are sick. That is one of the reasons why the Wisconsin calf respiratory scoring system (online at www.vetmed.wisc.edu and in the search window type: calf respiratory scoring chart) and ultrasound to diagnose pneumonia can be so helpful. Pneumonia is not the only reason calves get sick but it is the major reason that most calves get sick and die.
Even better is a workable strategy to keeping calves from getting sick in the first place. Veterinarians often suggest that raising calves individually until weaning goes a long way to assuring their health. That is usually why they recommend using hutches or similar housing. This suggestion is often not nearly so popular with the people who actually look after the calves.
Over the past few years, researchers began to look more seriously at social development of calves. Their research studies have built evidence that isolation early in life can have a lasting positive impact on calves. Now that creates the situation where dairy farmers and people who advise dairy farmers may need to modify recommendations on how to raise dairy calves — especially in that critical pre-weaning period.
In addition to the new research on social development in dairy calves, this fall, there have been two new reports comparing health in group-housed calves to individually-housed calves. In one report, pneumonia detected using ultrasound was just about twice as common in calves that were group-housed than in calves that were individually-housed.
In the second trial, researchers looked at the difference in risk of diarrhea and pneumonia in calves raised individually or in groups before weaning. There were two different feeding systems too but the difference in feeding systems should have given an advantage to the calves that were group housed because they were fed free-choice milk replacer. The individually housed calves were fed 2.5 L of replacer twice daily for the first three weeks and then it was increased to 3 L twice daily. It turned out that the group housed calves were 4 times more likely to be treated for scours and 6 times more likely to be treated for pneumonia.
The researchers suggested that the increased risk of scours was due to a greater risk of exposure to the microbes that cause scours. Different feeding systems can lead to differences in the consistency of manure too. The same increased risk of exposure to different microbes would be true for pneumonia because of the increased contact amongst grouped calves. The grouped calves had the additional risk because a common nipple was used to offer them the free-choice milk replacer. Calves that were group housed and fed free-choice were almost two weeks older when they were first treated for pneumonia. The researchers speculate that the difference in the age when calves were first treated might be due to increased vigour in calves that were not limit-fed from birth.
This new research helps to reinforce that calf health still seems to be impacted by grouping even as the industry moves toward different management systems.
The industry will need to balance the welfare implications of meeting behavioural needs of calves with the welfare implications of the impact of preventable illness on calf wellbeing.
Dr. Robert Tremblay is a veterinarian for Boehringer-Ingelheim and lives near Guelph.
