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Effects of walking speed and forage consumption on heart rate and energy expenditure by Alpine does

T. Berhan1, R. Puchala1, A. L. Goetsch1, G. Animut1,2, R. C. Merkel1, T. Sahlu1, and Z. B. Johnson3

1E (Kika) de la Garza American Institute for Goat Research, Langston University, Langston, OK, 2Animal Science Department, Oklahoma State University, Stillwater, 3Department of Animal Science, University of Arkansas, Fayetteville

Eight nonlactating Alpine does (2.5 to 6.5 yr of age; 46 ± 8.7 kg BW) were used to determine effects of standing vs walking at different speeds and interactions between locomotion treatments and forage ingestion on heart rate (HR) and energy expenditure (EE). Coarsely ground alfalfa hay was fed at a maintenance level of intake, and measures were performed in 15- to 20-min periods with a head-box respiration calorimetry system. In Exp. 1, measures occurred at least 3 h after feeding while standing (0 m/sec) on a treadmill and walking at 0.14, 0.27, and 0.41 m/s. Heart rate and EE ranked (P < 0.05) 0 < 0.14 < 0.27 < 0.41 m/s (HR: 79, 95, 108, and 125 beats/min; EE: 495, 620, 711, and 818 kJ/kg BW0.75). The ratio of EE:HR was lowest among treatments (P < 0.05) for 0 (6.26, 6.54, 6.58, and 6.56 (kJ/kg BW0.75)/(beats/min) for 0, 0.14, 0.27, and 0.41 m/s, respectively). In Exp. 2, EE was first determined while standing, followed by measures when walking at 0.07, 0.14, and(or) 0.20 m/s. Measurements also occurred while consuming 50% of the daily allocation of hay when standing or walking at the different speeds. Differences between values for forage plus walking or standing and walking or standing were calculated to determine the origin of or factor responsible for change in EE (i.e., walking or standing (W) vs forage consumption (F)), with standing estimates without forage used as covariates. There was an interaction (P < 0.05) between walking speed and origin of EE; EE for W ranked (P < 0.05) 0 < 0.07 < 0.14 and 0.20 m/s and for F was lower (P < 0.05) for 0 than for 0.07 and 0.20 m/s (-7, 81, 115, and 141 kJ/kg BW0.75 with W, and 215, 257, 247, and 256 kJ/kg BW0.75 with F, for 0, 0.07, 0.14, and 0.20 m/s, respectively; SE = 11.8). Differences in HR were fairly similar in magnitude to those in EE (-1, 9, 17, and 20 beats/min with W, and 35, 51, 40, and 42 beats/min with F, for 0, 0.07, 0.14, and 0.20 m/s, respectively (SE = 2.1)). In summary, increases in HR elicited by increased walking speed were associated with increased EE and a relatively small difference in EE:HR between standing and walking regardless of speed, suggesting potential use of HR to predict EE while grazing. Feeding increased EE to a much greater extent than did walking; the magnitude of increase in EE in response to feeding was slightly less when standing than walking regardless of speed, and forage consumption did not appear to alter the impact of walking speed.


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