OPINION: Individually-housed calves are not always healthier than group-housed calves

Recently, I mentioned a public opinion survey where people were asked their opinion of individual, paired or group housing of pre-weaned dairy calves. In the survey, the majority of people who expressed their opinion at a state fair in the U.S. felt that individual housing was the least acceptable housing system and that group housing was the most acceptable system.
Many veterinarians, including me, are reluctant to recommend that every farm adopt group housing especially if the farm plans to have large groups. I wanted to talk about some of the reasons why veterinarians might feel that way.

Veterinarians are interested in the health and performance of all dairy calves. Proponents of group housing point out that there is no proof that group housing per se leads to poorer health for the group-housed calves. That is technically true. I don’t know of any controlled-research trials where the only differences between calves is whether they were housed individually or in groups. That sort of controlled trial would be a difficult trial to do. In a controlled-research trial, you would set up study groups that only differed in one or a few things: in this case, whether the calves were alone, in pairs or in groups. As you can imagine, it would be hard to be sure that feeding, bedding, bedding contamination, ventilation, mixing, etc. were the same and only the group size was different.

A few years ago, there was a controlled study comparing health in dairy calves raised from birth in groups versus calves raised individually for the first three weeks, then grouped. But there were differences in their feeding strategy too, so you could not figure out if the differences in health were only due to grouping. The calves group-housed since birth were fed free-choice milk replacer. The calves that were first individually housed were initially fed 2.5 liters of milk replacer twice daily. Then, at three weeks, they were grouped and fed three liters of milk replacer twice daily in a trough. These feeding levels are lower than many experts recommend now. They started to wean calves in both groups at 56 days of age. The calves that were grouped from the start were close to four times more likely to get diarrhea and close to six times more likely to get pneumonia. Again, it is important to note that there is no way to tell if the big risk was grouping since birth or something else.

So, if there is a lack of strong, controlled, experimental evidence that group housing actually causes poorer health, why are many veterinarians so cautious about recommending it for every dairy farm?

One of the reasons is that there are several observational studies that show the risk of disease is higher on farms that use group housing compared to farms that use individual housing. Observational studies do not try to ‘control’ what happens on farms, all they do is look at what actually happens on farms. Ideally, observational studies should include disease information from a large number of farms. Of course, the most useful observational studies have been conducted on farms that are similar to yours.

So, observational studies can detect differences that occur ‘in the real world’ but they do not usually identify the reasons for those differences. If you’ve been on farms, you know that there can be lots of ways that the management of calves in groups is different from management of calves housed individually, not just the housing. It takes even more research to figure out what parts of the management is important to keeping calves healthy when they are raised in groups.

Pneumonia and diarrhea are the most common preventable diseases in young calves. Observational studies in several countries in Europe, in the US and in Canada have shown that calves housed in groups are more likely to be treated for pneumonia. Interestingly, the study in Canada used ultrasound to detect calves with pneumonia. That study found that farmers were less likely to see that group-housed calves had pneumonia compared to farmers looking after calves that were individually housed.

I want to repeat that there are usually so many other differences in the management of calves that are group-housed compared to calves that are individually housed that it is not possible to say that any health differences are due to the difference in housing alone.

There are farms with group-housed calves that have the same or even better health amongst their calves than many farms that house calves individually. So in that sense, group housing does not necessarily lead to poorer health. No matter how you house calves, there are many other things you need to do well to keep those calves healthy.