Evaluation of recently developed techniques for estimating diet composition in browsing herbivores.

Accuracy of estimates of botanical composition of herbivore diet may be improved through the use of recently developed techniques (alkane analysis, remote controlled oesophageal fistula valve). Three Boer goats allowed free choice of five forage species were used to compare seven methods of estimating diet composition with observed diet composition. The evaluated techniques either monitored intake [bite-count (IT1), bite mass corrected bite-count (IT2), relative bite mass corrected bite-count (IT3), micro-histological analysis of oesophageal extrusa collected at hourly intervals (IT4)] or faeces [alkane analysis (FT1), micro-histological faecal analysis (FT2), and in vitro corrected, micro-histological faecal analysis (FT3)]. Intake techniques had higher Kulczynski's similarity coefficients with measured values (70.7, 70.2, 65.5, and 78.6 respectively for IT1, IT2, IT3 and IT4) than did faecal techniques (58.9, 58.0 and 51.2 respectively for FT1, FT2 and FT3). Compared to IT2 and IT3, IT4 provided estimates of diet composition that was more similar to measured diet composition in terms of Kulczynski's similarity coefficients. However, estimates of diet composition were significantly different from measured values in 60% of cases for IT4 but only 40% of cases for IT2 and IT3. It is concluded that bite-count techniques (IT1 - IT3) can give as accurate estimate of diet composition as the more costly and technically demanding micro-histological analysis of oesophageal extrusa (IT4)