Meeting Abstract

P1.109  Sunday, Jan. 4  Does dietary protein limit mass gain in migrating blackcaps refueling at stopovers? AAMIDOR, Sarah E*; BAUCHINGER, Ulf; PINSHOW, Berry; Ben-Gurion University of the Negev; Ben-Gurion University of the Negev; Ben-Gurion University of the Negev amidors@bgu.ac.il

Both fat and protein are used by birds as fuel during migratory flight, and need to be restored at stopovers. Mass gain is initially slow but increases after 2-3 days into the stopover. One explanation for this is the catabolism of digestive tract tissue (GIT), which causes reduced digestive function and hence slow body mass gain. We tested the prediction that dietary protein limits a bird’s readiness to leave a stopover because it affects the rate at which the GIT is rebuilt, and, thereby, the rate of tissue accumulation. We measured body mass, pectoral muscle size, and body composition (by dual energy x-ray absorptiometry). Thirty migrating blackcaps (Sylvia atricapilla) were mist-netted and divided into three equal groups. The birds were deprived of food for 24 hours to assure stopover behavior. The groups were then provided semisynthetic diets, that differed only in protein content (i.e. 3%, 5.3% and 10%), and water ad libitum during the 6 day experiment. Mean daily food intake differed significantly among groups (Holm-Sidak multiple comparison F_(2,172)= 4.103, p=0.018). Body mass changed differently over time among the groups (-0.13±0.08 g/d, -0.10±0.16 g/d, 0.01±0.26; RM ANOVA, time*group: F_(12,168)=3.08, p<0.0006; for 3, 5.3, and 10%, respectively) as did pectoral muscle size (RM ANOVA time*group: F_{(12, 168)}=2.11, p<0.05). There were no significant differences in the change of fat fraction from day 1 to day 7 between the groups (ANOVA F_(2,6)=0.38, NS). Thus, the data suggest protein may be a limiting dietary factor, and that blackcaps require more protein than that we provided to replace fat used as fuel during migratory flight.