Respirometry and Ruminant Nutrition

Abstract

The gaseous exchange between an organism and the environment is measured by respirometry or indirect calorimetry. Once the oxygen consumption (O 2) and the production of carbon dioxide (CO 2) and methane (CH 4) are known, the energy losses by gas and heat can be calculated. Energy metabolism and methane production have been studied in the Calorimetry and Metabolism Laboratory of the Federal University of Minas Gerais, located in Belo Horizonte, Minas Gerais, Brazil. Animals used are mainly Zebu cattle and their crossbreeds that represent most beef and dairy cattle breed grazed on tropical pastures. System calibration and routine work are addressed in this text. The results obtained on respirometric chambers are expressed in net energy (NE), which can be net energy for maintenance (NE m), lactation (NE L), weight gain (NE g), and pregnancy (NE p). NE is, in fact, what is used by the animal for maintenance and each productive function. The values of k (conversion efficiency of ME into NE) for maintenance (k m), milk (k L), weight gain or growth (k g), and pregnancy (k p) are determined. Thanks to the peculiarity of the respirometric technique, the same animal can be evaluated several times, in different physiological states and planes of nutrition.

Energy metabolism of pregnant zebu and crossbred zebu dairy cattle

“…Right after each apparent digestibility trial, methane and heat production were measured for 22 to 23 hours by performing extrapolation for a period of 24 h, using an open-circuit indirect calorimetry system, adopted by the Veterinary School, UFMG, according to [9,10]. The respirometric chamber was made of steel with acrylic side windows, 3.45 m long, 1.45 m wide and 2.45 m high (22.391L of internal volume).…”