Use of artificially applied n-alkanes as markers for the estimation of digestibility, food selection and intake in pigeons (Columba livia)

The experiment was conducted to determine the accuracy with which food selection, intake, and apparent digestibility of protein could be estimated with n-alkanes in comparison to observed intakes and digestibility estimated through total excreta collection. Four pigeons (Columba livia) were used as study subjects and four pigeons as controls. All animals were individually caged. In Trial I the birds were fed a pelleted diet ad libitum which had been labelled with the n-alkanes octacosane (C-28 2000 ppm dry matter (DM)), dotriacontanc (C-32 1500 ppm DM), and hexatriacontane (C-36 2000 ppm DM). The birds had 6 days of adaptation to the diet followed by 4 days of total excreta collection. On the basis of observed intakes and total excreta collection n-alkane recoveries were estimated and compared to published data for chickens. The intakes obtained using hentriacontane (C-31) and C-32 corrected for relative recoveries were very similiar to the observed intakes. When alkanes were not corrected for relative recoveries, the alkane method significantly underestimated the intake. The recovery rate Of C36 n-alkane was 80% and the protein digestibility coefficients obtained after correction with the recovery rate did not differ significantly from digestibility obtained with total excreta collection. In Trial 2 selective intake was measured in four birds offered three different pelleted feeds ad libitum for 3 days of adaptation followed by 5 days of sample collection. Pellet I was labelled with n-alkanes, C-28 (2000 ppm DM), C-32 (1500 ppm DM), and C-36 (2000 ppm DM), pellet 2 was labelled with hexacosane (C-26 3000 ppm DM), and pellet 3 with triacontane (C-30 3000 ppm DM). Very accurate estimates of pellet selection were obtained using the patterns of n-alkanes in excreta, being in average within +/-2.5% of the actual pellet selection in individual birds.