Comparison of Four Techniques to Estimate Forage Intake by Rams Grazing on a Panicum coloratum L. Pasture
The estimation of daily feed intake is important in the determination of animal production The objective of this experiment was to compare measurements of animal forage intake obtained by the use of four techniques: pre- and post-grazing difference in standing forage mass, total daily feces collection in combination with in vitro diet digestibility, total daily feces collection in combination with diet digestibility estimated by the fecal nitrogen index and the n-alkane technique. The experiment was carried out on a stockpiled Panicum coloratum L. pasture during two growing seasons. The treatments for the first season comprised standing forage mass accumulated after mid-October, mid-January and mid-February mechanical harvest to 8-cm stubble. In the second season, the treatments came from forage mass accumulated after mid-December, early January and February cuttings. Treatments were assigned at random to 0.5 ha plots in two replicates. The most closely correlated estimations of intake (r = 0.83; P < 0.01) were those obtained through total collection of feces and diet digestibility and the least with either the in vitro technique or the fecal N index. The apparent overestimation of intake by the n-alkane technique might be a consequence of the bias produced by forage sampling. In general terms, the techniques used to estimate intake were responsive to treatment effect.