An open-circuit hood system for gaseous exchange measurements in small ruminants

The description of an open-circuit hood system to measure gaseous exchange in small ruminants is reported along with the equations and constants neede d for automatic calculations on a computer. The performance of the system w as evaluated by using a series of methanol combustion tests and respiration trials on sheep eating Rhodes grass (Chloris gayana) or Lucerne (Medicago sativa) chaffs. The total dead space was 821 including 721 of hood capacity which gave a lag-time for expired gas analyses of 50 s when the hood was v entilated at 1001 min(-1). The measured rate of oxygen consumption was 102/-1.1% of the value as confirmed by the methanol combustion tests. Prelimin ary animal evaluation tests showed that the postprandial profiles of gaseou s exchange in sheep could be readily measured by using the open-circuit hoo d system. Moreover, the pattern of gaseous exchange was dependent upon the type of forage being consumed by the sheep. (C) 1999 Elsevier Science B.V. All rights reserved.