The estimation of faeces output of shtall‐fed sheep using chromic oxide marker

Faeces were collected over 66 days from 12 penned sheep fed dried grass and dosed with 1.94 g chromic oxide in capsule form twice daily. Marker recovery estimated from analysis of representative samples of the faeces was 92.8 per cert. Faeces organic mattcr cut puts were estimated from the marker concentrations in: (1) daily representative samples, (2) “grab” samples bulked on an equal dry matter basis for each sheep over three days, and (3) “grab” samples bulked for each half‐day over all sheep. In each case the ectimates significantly exceeded the actual faeces by approximately 10 per cent, reflecting thc incomplete marker recovery. The standard deviations of the differences between actual and estimated outputs were, respectively, 15.5, 16.7, and 12.4 per cent of the actual faeces. In estimating total faeces outputs of 12 sheep over three‐day periods, bulking of grab samples over the 12 sheep for each half‐day and over the six half‐days for each sheep were of similar accuracy.