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For those few bird species that are exclusively frugivorous, the low protein content of fruits is likely a major nutritional constraint. Physiological mechanisms that allow strict frugivory remain enigmatic, but reduced protein requirements may suffice. We investigated protein requirements of Pesquet's Parrot (Psittrichas fulgidus), a highly specialized, obligate frugivore. Three isocaloric, fruit-based diets of varying protein content (6.1, 3.3, and 2.6% dry mass crude protein) were used in feeding trials lasting three to five days per diet. A minimum dietary protein requirement of 3.2% dry mass was estimated from balance trials. Endogenous nitrogen losses were 0.05 gN kg−0.75 day−1 and nitrogen equilibrium occurred at 0.32 gN kg−0.75 day−1. Those values are extremely low compared to those of granivorous and omnivorous bird species, but higher than those of nectarivorous species. In terms of nitrogen losses and requirements, Pesquet's Parrot most closely parallels the highly frugivorous Cedar Waxwing (Bombycilla cedrorum). Thus, reduced protein requirements appear to play an important physiological role in ability of highly frugivorous birds to subsist on fruit diets.
Nitrogen balance among Pesquet's Parrots, represented by the solid line, where Y 0.86X 0.05 (R 2 0.96; n 9). Data for different birds are indicated by different symbols. Values below the dashed line (Y X) indicate net N anabolism, whereas values above this line indicate net N catabolism. mined (Robbins 1993, Murphy 1993); minimum endogenous N losses (i.e. theoretical N excretion on a protein-free diet) are indicated by the y-intercept, and N equilibrium occurs where N intake equals N excretion. To compare N balance plots among individuals, ANCOVA were used. Once N equilibrium was determined, CP requirements for maintenance of body mass were calculated for each bird by regressing percentage CP in the diet against N intake; the point at which percentage CP N intake at N equilibrium provided estimated minimum protein requirement for maintenance (Brice and Grau 1991, Murphy 1993, Robbins 1993). All statistical analyses were conducted with SPSS v.7.5 software (SPSS Inc., Chicago, Illinois), with alpha set at 0.05. Results and discussion. Dry mass intake remained constant among birds (F 3.20, df 2 and 6, P 0.11) and among diets (F 1.77, df 2 and 6, P 0.25; Fig. 1). The birds did not compensate for low dietary protein content by increasing consumption, as apparently occurs in some frugivorous birds and bats (Thomas 1984, Izhaki and Safriel 1989). Body masses remained constant throughout all feeding trials (F 0.49, df 2 and 6, P 0.64; Fig. 2), indicating no net catabolism or anabolism occurred. All birds exhibited similar N balance, as indicated by similar slopes (F 0.10, df 2 and 3, P 0.91) and y-intercepts (F 0.87, df 2 and 5, P 0.47; Fig. 3). Endogenous N losses were 0.05 gN kg 0.75 day 1 and N equilibrium occurred at 0.32 gN kg 0.75 day 1. Based on regression analysis and N equilibrium, a diet containing 3.2% dm CP (using a 4.05 nitrogento-protein conversion factor) would meet the minimal requirements for maintenance in Pesquet's Parrot.
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... It is also needed for understanding survival and productivity (6,7), and it is therefore critical to implement adequate conservation strategies (3,8,9). There is an increasing volume of research on the nutritional requirements for growth and maintenance of psittacines (4,(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22), but malnutrition is still one of the main issues in the care and propagation of this group (4,5,(23)(24)(25) and providing nutritionally adequate diets must be a primary concern ...
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Thesis
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Research
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Article
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