Determination of herbage intake of suckling lambs using long-chain n-alkanes as markers

Extract

The n-alkanes of grass outioular wax (odd-chain, C₂₅- C₂₅) can be used simultaneously with dosed n-alkanes (C₂₈or C₃₂) as markers for estimating the herbage intake of grazing sheep if the faecal recoveries of both herbage and dosed markers are the same. In adult sheep the accuracy of herbage intake estimation is not affected by the inclusion of concentrate in the diet as long as the intake and alkane concentrations of the concentrate are known. If, similarly, the ingestion of milk does not interfere with the relative absorption of dosed and herbage alkanes the herbage intake of suckling lambs at pasture could be estimated. To evaluate the potential of the technique in suckling lambs the faecal recoveries of odd-chain herbage n-alkanes and of dosed dotriacontane (C₃₂) were determined in lambs offered eves’ milk and freshly cut herbage.

From 2 weeks of age seven individually-housed male lambs received 1 kg/day homogenised ewes’ milk (166 g/day dry matter (DM)) in 4 feeds from an automatic feeder. The milk Has obtained by daily hand-milking of East Friesland ewes and was stored at -20° until used. Freshly cut perennial ryegrass was offered to the lambs ad libitum from the age of 4 weeks. A 6-day total collection of faeces was carried out when the lamba were 10 weeks of age.