Utilising faecal NIRS measurements to improve prediction of grower and breeder cattle performance and supplement management

Summary

F.NIRS is likely to be able to contribute as an input to the Decision Support Systems in two fundamental ways. Firstly F.NIRS provides a means to measure dietary digestibility and crude protein directly rather than having to estimate them from visual evaluation of the pasture.

Secondly it is likely that F.NIRS can be used to improve estimation of the voluntary intake, or the potential voluntary intake. Coates (2004) developed calibration equations to predict voluntary forage intake in penned cattle. In addition, prediction of the voluntary intake of pasture is implicit in the existing F.NIRS calibration equations to predict LW change of an animal, as LW change must primarily be a function of metabolizable energy intake, and therefore of digestibility and forage intake. The satisfactory F.NIRS prediction of animal LW change, even at high stocking rate when sometimes little pasture was available at the Swans Lagoon site in the present trials, also supports the hypothesis that voluntary pasture intake can be measured in at least some circumstances even when the amount of pasture on offer is limiting.

It is clear from the experimentation that the leaf content of tropical grasses, both as presented to the animal or after extensive rumen fermentation, can be described by NIRS calibration equations. It is therefore appears likely that the information to measure the leaf content of the tropical grass forage ingested can be determined in faecal NIR spectra, and thus allow F.NIRS to measure the voluntary intake of tropical forages with lower error than is presently possible.