I was working on one of our monitor farms yesterday and had chance to watch some of the high yielders. With my phone’s stopwatch counting down a 15second interval I counted the respiration rate for four cows that were lying in the cubicles to get the above numbers. These convert to 68, 76, 80 and 72 breaths per minute – well above the normal of 40 and into the danger zone of over 60 breaths/min. It was midday and getting hot: the average THI in that shed over the past three hours was 70, the farmer was in shorts and a very sketchy old polo shirt.
The cows were obviously struggling with the heat; their main route for shedding heat load was working too hard. This cow had also stopped ruminating which will reduce saliva flow, rumen health, productivity and probably her daily feed intake.