The possible use of long chain (C19-C32) fatty acids in herbage as an indigestible faecal marker

Abstract

The organic matter (OM) intakes of grazing ruminants can be calculated from the digestibility of the OM and faecal OM outputs which in turn are determined indirectly by administering known amounts of indigestible markers such as Cr₂O₃(Langlands, 1975). The possibility that the C₁₉–C₃₂fatty acids in fresh herbage could be suitable as an indigestible marker for determining intakes of grazing animals was examined. An early report had shown that when ‘Grasslands Ruanui’ perennial ryegrass (Lolium perenneL.) was fed fresh to sheep the C₁₉–C₃₂fatty acids appeared not to be absorbed because their concentration increased from 7·2% of the total dietary fatty acids to 23·9% of the total faecal fatty acids (Body & Hansen, 1978).