Determination of the grazing activity energy cost in Boer goat wethers using a portable indirect calorimety method

TitleDetermination of the grazing activity energy cost in Boer goat wethers using a portable indirect calorimety method
Publication TypeWeb Article
Year of Publication2015
AuthorsBrassard, M-E, Puchala, R, Sahlu, T, Goetsch, AL
Series TitleJournal of Animal Science
Type of Medium(Supplement s3)

Ten yearling Boer goat wethers (44.4±0.95 kg) were used to determine heat energy (HE) and the grazing activity energy cost (GAEC) while standing or grazing Sudangrass pasture with a portable indirect calorimetry system. The method entailed the use of a partial face mask that allowed unrestricted grazing to measure oxygen consumption and carbon dioxide emission for 30 min while restrained in a stanchion near the grazing area, followed by 60 min while grazing with other members of the group. The face mask of the animal was attached to a 15-m tether along with a corrugated plastic hose through which exhaled air was passed to FlowKit Mass Flow Generator and FoxBox Respirometry System (Sable System, Las Vegas, NV) that were carried by a researcher who allowed unrestricted goat movement. Prior to measurements animals were trained to become accustomed to presence of personnel and use of the equipment, with grazing behavior similar among all animals of the group. Measurement periods were during morning and afternoon grazing bouts. Heat energy while restrained was 18.7 kJ/kg BW0.75/h or 446±10.7 kJ/kg BW0.75/d. Heat energy while grazing increased to 35.1 kJ/kg BW0.75/h or 843±39.3 kJ/kg BW0.75/d, implying that the grazing activity energy cost (GAEC) was 16.4 kJ/kg BW0.75/h. While on the pasture goats spent 8.5 h/d grazing; therefore, the daily GAEC was 138±17.3 kJ/kg BW0.75. A very similar GAEC of (165±10.4 kJ/kg BW0.75/d) was determined from the difference in HE estimated indirectly from heart rate between times when grazing a 0.8-ha pasture and confined in nearby 1.2 × 1.2 m pens and fed fresh forage. In conclusion, this method offers promise for relatively simple and direct estimates of the sizable fraction of total HE comprised by GAEC.