Sickness and poor growth rates of calves between birth and weaning can negatively affect future productivity.
A study out of Ireland investigated the use of calf jackets in the hope of reducing the negative effects of low temperatures, wind speed and rain on the growth and health of young calves.
Key points
No differences in weight, growth or feed conversion efficiency in calves with or without jackets in the first 3 weeks of life
The week after removal of jackets, calves grew slower and had a lower feed conversion efficiency
Calf jackets are not likely to be of benefit in the New Zealand system, however, studies on the use of jackets for sick calves is needed
Holstein-Friesian calves (heifers and bulls) were split into two groups:
Jacketed from birth until 3-weeks-old
Non-jacketed
The calves in this study were group housed in indoor pens using straw as bedding and were fed milk replacer and concentrates using automatic feeders. Calves were weaned at 8 weeks, and the experiment was completed at 9 weeks.
The calves without jackets consumed more milk replacer than the calves with jackets on. This resulted in greater total dry matter intakes (DMI; milk and concentrates) for non-jacketed calves up to 3 weeks of age.
Even though the non-jacketed calves ate more, both groups were similar in live weight (LWT) throughout the 9 weeks that the calves were monitored.
After the removal of the jackets, total DMI were similar for both groups. Interestingly, the week after the removal of their jackets, the jacketed calves grew slower than the non-jacketed calves (0.49 kg/d vs 0.61 kg/d).
This resulted in a lower feed conversion efficiency of the calves that previously had jackets on for that week, as they grew slower but had comparable DMI to the non-jacketed calves.
The researchers measured the skin surface temperature of the calves over a 24 hour period (Figure 1 below).
Using the right axis of the graph, the mean ambient temperature was 7.7°C (solid black line below), rising to approx. 10°C in the early afternoon.
Using the left axis, the skin surface temperature was relatively constant over the 24 hour period for both groups. However, skin temperature was on average 6°C higher in calves with jackets on (dashed line; J) compared with the calves without jackets (dotted line; NJ).
Although there was a pretty big difference in skin temperature, there were no differences between the groups in core body temperature, eye temperature or rectal temperature throughout the first 4 weeks of life. The authors suggested that the non-jacketed calves were able to use the extra energy (due to their increased DMI) to regulate their core body temperature.
When calves are cold, they conserve energy by lying down for longer periods rather than standing. Therefore, it was expected that the non-jacketed calves would have had longer periods of lying compared with the calves with jackets on.
It was also expected that in the week after the jackets were removed these calves would also spend more time lying down. Nevertheless, there were no differences in lying behaviour, with calves in both groups spending approximately 18 hours/day lying down both before and after jacket removal.
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Were jacketed calves healthier?
There were 44 calves with jackets and 46 calves without jackets. As discussed in our heifer growth pattern summary (here), it is difficult in experiments with low numbers to compare proportion data (for example: pregnant yes vs no, or disease yes vs no).
For this reason I believe the researchers could not comment on whether there were any differences in the proportion of calves with scours or other health issues. It would be really interesting to repeat this experiment with many more calves to see if the calves without jackets were more likely to get sick. Or to compare indoor vs outdoor systems with and without jackets.
The researchers concluded that under the conditions of their experiment (group housed indoors), there were no benefits to calf performance as a result of the use of calf jackets in group-housed calves in the first 3 weeks of their life. They did note that the slower growth and reduced feed conversion efficiency in the week after the jackets were removed could indicate that perhaps the jackets should be left on the calves for longer than 3 weeks. I would argue that if there were no benefits in the first 3 weeks, what benefit would leaving them on for longer have? Maybe the majority of calves won't need jackets at all?
A NZ study in Mossburn, South Island recorded an average air temperature of 9°C inside the calf-rearing facilities. This is a few degrees warmer than that found in the Irish study reported here. Therefore, it is unlikely that using calf jackets would be of benefit in the New Zealand rearing system. However, the Irish authors did suggest that a study using diseased-challenged calves would be of interest to test if providing jackets to calves that have been exposed to disease would decrease their chance of becoming sick.
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