Changes in heat production by sheep of Guirra breed after increase in quantity of barley grain on the diet

The heat production (HP) from CH4 and CO2 production and O2 consumption was determined by the respirometry quotient (RQ) method and by C–N balance measurements (CN method). Twelve dry and none pregnant Guirras sheep were fed with 3 diets consisting in the same quantity of alfalfa hay (2 kg/d offered) and increasing quantities of barley grain (150, 300 and 450 g/d). The experimental design was completely random with 4 replication by treatment. Fasting HP was determinate in one sheep from each group. Ewes were allocated to individual metabolism cages at thermoneutrality. After 10 d of adaptation, feed intake, and total fecal and urine output were recorded daily for each ewe during a 5 d period, as well as BW at the beginning and end of the period. Gas exchange measurements were recorded by open-circuit face mask respirometry system. Average HP measured by RQ method was in agreement with the average HP determined by CN method accounting for 395.6 and 393.4 kJ/kg0.75 BW/d, respectively. The metabolizable energy requirement for maintenance (MEm) was estimated by linear regression at 352.3 kJ/kg0.75 BW.