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 sele ction, intake, and apparent digestibility of protein could be estimated wit h n-alkanes in comparison to observed intakes and digestibility estimated t hrough 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 b een 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 coll ection n-alkane recoveries were estimated and compared to published data fo r chickens. The intakes obtained using hentriacontane (C-31) and C-32 corre cted for relative recoveries were very similiar to the observed intakes. Wh en alkanes were not corrected for relative recoveries, the alkane method si gnificantly underestimated the intake. The recovery rate Of C36 n-alkane wa s 80% and the protein digestibility coefficients obtained after correction with the recovery rate did not differ significantly from digestibility obta ined with total excreta collection. In Trial 2 selective intake was measured in four birds offered three differ ent pelleted feeds ad libitum for 3 days of adaptation followed by 5 days o f sample collection. Pellet I was labelled with n-alkanes, C-28 (2000 ppm D M), 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 p atterns of n-alkanes in excreta, being in average within +/-2.5% of the act ual pellet selection in individual birds.