Effects of method of determining heat energy:heart rate of confined and grazing Boer goats

Heat energy (HE) of 11 yearling Boer goat wethers (43.4±1.4 kg) consuming fresh Sudangrass ad libitum while confined in 1.2 × 1.2 m pens (C) or grazing a 0.8-ha pasture (G) was determined in a crossover from heart rate (HR) measured over 24 h and the ratio of HE to HR (HE:HR) estimated two ways. The BARN method involved a prior period in metabolism cages with head-boxes of an indirect calorimetry system measuring oxygen production and emission of carbon dioxide and methane for 24 h (i.e., 96 individual measurements) while consuming a moderate quality grass hay. The SPOT method entailed a portable face mask system measuring oxygen consumption and carbon dioxide production for 5 min while standing near grazing and confinement areas at 08:00, 12:00, 16:00, and 20:00 h, after 30 min of adaptation. With both methods, HR, HE, and HE relative to BW0.75 (HEMBW) were greater (P0.05) between methods for C in HR (76.4 and 70.0 beats/min; SE=2.68), HE (8.4 and 7.9 MJ/d; SE=0.20), HEMBW (485 and 455 kJ/kg BW0.75; SE=10.7), or HE:HR (6.420 and 6.573 kJ/kg BW0.75 per heart beat for BARN and SPOT, respectively; SE=0.1939). For G, HR (100.9 and 92.5 beats/min; SE=2.35; P