Low level of chromium oxide to estimate faecal output in cattle

The aim of this research was to evaluate the use of a low level of chromium oxide (Cr2O3) incorporated into the concentrate ration to estimate faecal output (FO) in cattle. Four in vivo digestibility essays were conducted using four steers with live weights of 214±31kg, receiving fresh Italian ryegrass (Lolium multiflorum Lam.). About 200g of concentrate with 5g kg-1 of Cr2O3 was daily rationed during 12 days, where 7 days were used for animal adaptation and 5 days for measurements. The total faecal output was collected and compared with faecal output estimated from grab samples, collected twice a day (8:00 am and 4:00 pm) or at 2-hour intervals, from 8:00 am to 10:00 pm. The average faecal chrome concentration collected at 08:00 am and 04:00 pm (445mg kg-1) was similar with the average of samples collected at a 2-hour interval (447mg kg-1). The marker recovery rate (RR) increased linearly, from approximately 40% to around 80%, with the faecal chrome concentration until approximately 250mg kg-1 OM. When the faecal chrome concentration was higher than 250mg kg-1 OM the RR was relatively constant, with values around 0.76. The faecal output was overestimated up to 35% when the RR was not considered. When the RR was used, faecal output estimative was similar to the total faecal output collected. The faecal output can be accurately estimated in cattle eating ryegrass using a low level of Cr2O3 incorporated into the concentrate ration concomitant with twice-a-day faecal grab samples collection.

cattle; herbage intake; Lolium multiflorum Lam