Decandia, M.; Molle, G.; Cabiddu, A.; Scanu, G.

Long chain n-alkanes, are reliable markers of faecal output (FO), but their chemical extraction is time-consuming. We hypothesized that polyethylene glycol (PEG), analysed by near infrared spectrometry (NIRS), can replace C36 for the estimation of FO in browsing goats. Faeces were sampled twice daily for 2 days, after 9 days of adaptation. Calibrations relying on the whole NIR region (1100 to 2500 nm), or relying only on segments not involved in PEG-tannin bonds (less than 2280nm), were calculated (R2 equal to 0.999, SECV equal to 0.32 less than and R2 equal to 0.998, SECV equal to 0.45 less than, respectively). Group estimates of FO, using C36 or PEG, did not differ when the restricted NIR equation was utilized. However, assuming that the FO value provided by C36 analysis is correct, FO tended to be overestimated (P less than 0.14) for PEG, when the whole NIR region equation was utilized.