With the aid of a beat-meter, a fundamental investigation was conducted to detemine the heat production of grazing Japanese Black Breed of Cattle indirectly by means of the heart-rate counting.
The expired-air collection by the Douglas bag method and the counting of heart rate were carried on simultaneously under different conditions ─ various levels of resting and of walking on the treadmill.
The relations of heat production to heart rate were examined in four combinations of units for describing values. The correlation coefficents between heart rate and heat production were as follows :
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Beat number : Cal. + 0.82 ┐ (from 64 data with 18 cows)
Beat number : Cal. + 0.79 │
Beat number : R.M.R.+ 0.71 ├ (from 40 data with 12 cows)
Beat % : Cal. + 0.77 │
Beat % : R.M.R.+ 0.66 ┘
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These correlations were highly significant (P＜0.01). The regression equations between Beat number/min.(X) and Cal./kg./hr. (Y) were Y = 0.036 x 1.241 (from 64 data), or Y = 0.042X - 1.766 (from 40 data).
It was concluded that the most useful equation to estimate the heat production of grazing cattle was Y = 0.042X - 1.766.