The Use of Chromic Oxide in the Measurement of Individual Feed Intake in Cattle Fed on Silage and Barley

Abstract

SUMMARY1. Three experiments are reported in which chromic oxide, administered as a component of shredded paper at 09·00 and 16·30 hr daily, was used in the estimation of the faecal output of steers fed on silage and barley.2. Four Friesian steers of 160 kg live weight were used in experiment 1. They were fed on grass silage ad libitum with controlled allowances of concentrate supplement. ‘Absolute’ recovery of Cr2O3 in total collections was 85–91%, though it was apparent that some faeces may have been lost from the total collections. ‘Relative’ recovery in grab samples was 97%.3. Diurnal variation in Cr2O3 excretion was investigated in experiment 2 with four yearling Friesian steers. Faeces were sampled in three 24-hr periods at each natural defaecation. A significant and consistent diurnal variation was observed, with the lowest concentration of Cr2O3 occurring during the night. Concurrent grab samples taken at 09.15 and 17.00 hr over four days gave estimates of cr2O3 in the faeces which were 16·27% higher than the mean concentration for the three 24-hr sampling periods.4. Day-to-day variation in the Cr2O3 content of grab samples was examined in experiment 3 with eight yearling Friesian steers. Four steers received 3·63 kg/head per day of barley supplement and four received 1·81 kg. Both groups were offered silage of 25% dry matter ad libitum. Faeces were sampled per rectum twice daily at 09.15 and 17.00 hr over four-day sampling periods. The degree of day-to-day variation was small and tended to be random.