Cockatiel transition from a seed-based to a complete diet.
Key words: transition, nutrition, seed-based diet, complete diet, avian, cockatiel, Nymphicus hollandicus
Psittaciform birds kept as companion animals are often provided with nutritionally incomplete seed-based diets and develop deficiencies in one or more essential nutrients. (1,2) Use of a complete diet, based on the nutritional ecology and diets of wild psittaciform birds and knowledge of the gastrointestinal anatomy, physiology, and nutrient requirements of the species in question or related species, may allow for greater success with the rearing and propagation of captive psittaciform birds. (1) If birds are currently reared on seed-based diets, then a transition strategy to a complete diet should be considered. In addition, commercially available diets advertised as nutritionally complete vary greatly in ingredient composition, ingredient particle size, nutrient profile, and method of processing. Limited data are available on the effectiveness of different commercially available diets to transition psittaciform birds from nutritionally incomplete seed-based diets. The purpose of this study was to determine the effects of diet transition in cockatiels (Nymphicus hollandicus) that were housed in a controlled experimental setting, by using a standardized transition strategy with 2 different commercially available cockatiel diets, both advertised as nutritionally complete.
Materials and Methods
True amino acid digestibility
A rooster assay was conducted on each nutritionally complete diet to assess amino acid digestibility variations. A total of 16 cecectomized, single-comb, white leghorn roosters were placed in individual raised-wire cages to comprise a completely random design. True amino acid digestibility was estimated by modified methodologies of Sibbald. (4) Roosters were fasted for 24 hours, then a 30-g sample of each diet was precision-fed to 8 replicate roosters. Excreta were collected 48 hours after precision-feeding. Excreta samples were lyophilized, weighed, and ground. The feed and excreta samples were analyzed in a commercial laboratory for amino acid content.
Birds and housing
Fourteen cockatiels, approximately 2 years of age and from the same commercial breeder, were used in the experiment. Cockatiels were deemed healthy by physical examination from the collaborating avian veterinarian. Initial cockatiel body condition ranged from normal to obese based on palpation of body mass and a normal body weight (BW) described between 80 and 100 g. (5,6) Cockatiels were individually housed in acrylic cages (53 cm x 43 cm x 41 cm) in an environmentally controlled room. Temperature was maintained at 24[degrees]C (75[degrees]F) and lighting was continuous for 12 hours per day. Each cage contained an acrylic feed hopper designed to minimize feed wastage, an acrylic water fount, wooden perches, and various toys to enhance social and physical well-being. All cages were positioned on large plastic trays to capture any feed wastage and allow for accurate feed intake measurement. Cages were cleaned daily. Feeding behavior using complete diets was mimicked, and birds were handled daily. Birds were weighed twice per week throughout the experiment.
Transition strategy and diet
One of 2 commercially available complete cockatiel diets was assigned to 14 cockatiels (7 birds received each diet): diet A, a baked feed kibble composed of large particle ingredients that were exposed to dry heat applied in an oven; and diet B, an extruded feed kibble composed of small particle ingredients that were exposed to steam and pressure. Diet A was beige in color, approximately 19 mm in diameter, and contained oat flour, white millet flour, oatmeal, sunflower oil, and sunflower meal as the first 5 listed ingredients. Diet B was multicolored (red, orange, yellow, and green), approximately 5 mm in diameter, and contained ground corn, soybean meal, ground wheat, wheat germ meal, and sugar as the first 5 listed ingredients. Treatment allocation was blocked by location of the cage in the room. Before starting the transition period, all birds were provided a commercially available seed-based diet for ad libitum consumption while housed at a commercial breeding facility as well as for 30 days at the research facility. Water was provided ad libitum throughout the experiment. Each diet used in the experiment was analyzed for selected nutrients (Table 1).
The transition strategy took place gradually over a 12-day period (Table 2). Gradual changeovers from seed to complete diets have been recommended. (7) Diets were provided in 60-g total allotments each morning of the transition period. On the following morning, the amount of seed-based diet and complete diet in both the feed hopper and catch tray were recorded. After the 12day transition period, the birds remained on complete diets, and feed intake and BW measurements continued to be recorded for an additional 16 and 35 days, respectively.
Blood collection and analysis
Approximately 0.5 mL of blood was collected from the right jugular or medial metatarsal vein of each bird before the transition period and on days 15 and 29 of the experiment. Blood samples were collected at the same time each day, and collection was completed in the same amount of time to reduce variation. The samples were sent to a commercial laboratory (Avian & Exotic Clin Path Labs, Wilmington, OH, USA) for hematologic testing and plasma biochemical analysis. Measurements included red blood cell count, packed cell volume, hemoglobin, total protein, mean corpuscular hemoglobin concentration, mean corpuscular volume, white blood cell count and differential, aspartate aminotransferase, bile acid, calcium, chloride, cholesterol, creatine phosphokinase, glucose, lactate dehydrogenase, phosphorus, and uric acid. In the event of insufficient plasma volume to complete biochemical assays, statistical analysis was run on fewer replications. All procedures were approved by the West Virginia University Animal Care and Use Committee.
Data were analyzed by using a completely random and randomized complete block design for the digestibility and transition study, respectively. Data were analyzed by using the GLM procedure of SAS Version 9.0 (Cary, NC, USA). Alpha level was designated as .05. Statistical analysis was performed at each daily period that measured variables were collected during the experiment.
True amino acid digestibility data demonstrated that diet A contained higher levels of digestible arginine, leucine, isoleucine, tryptophan, alanine, histidine, proline, aspartic acid, and glutamic acid (P < .05, Table 3). Diet B contained higher levels of digestible methionine, threonine, and lanthionine (P < .05, Table 3).
All cockatiels accepted the transition strategy irrespective of complete diet. Cockatiels transitioned to diet A consumed significantly more of the complete diet and less of the seed-based diet during periods of measurement throughout transition (Figs 1 and 2). Total feed intake was significantly greater for cockatiels fed diet B for one-third of the measurement periods (Fig 3). Cockatiel BW was generally not affected because of complete feed utilized during or after transition (P > .05; Fig 4). However, a decrease in weight for both treatment groups was observed during the transition period. No significant differences were found in plasma biochemical or hematologic results between cockatiels fed the 2 complete diets before or on days 15 and 29 of the study period (data not presented due to lack of treatment difference). Moreover, all blood test results were generally within reference intervals before, during, and after transition. (8,9)
Despite significant differences among digestible amino acids of the complete diets, most levels of amino acids provided by each of the 2 complete diets used in this study were within 90% of the recommended total amino acid levels of broiler chicken finisher diets. (10) Amino acid requirements of cockatiels are likely not similar to production chickens, which are expected to grow rapidly and die young. (7) However, higher digestible amino acid levels may alleviate performance and health detriments due to stress. (11)
Cockatiel transition from a seed-based diet to each complete diet was successful based on consumption, maintenance of BW, lack of change in plasma biochemical and hematologic test results, and no observed morbidity or mortality. The decrease in BW of both treatment groups during transition was likely associated with weight loss in obese subjects, which subsequently decreased mean treatment BW data to within the reference interval. (5,6) Based on complete diet and seed-based diet consumption, it may be speculated that cockatiels were more accepting of diet A during transition, and that diet A more efficiently maintained BW. Diet A differed from diet B in terms of ingredient composition, ingredient particle size, nutrient profile, and method of processing. Perhaps these variations made diet A more acceptable or enhanced nutritional value, thus improving efficiency of weight maintenance. Diet A was composed of larger ingredient particle size and formed into a larger feed kibble, providing a greater diet structural component compared with the small particle size and kibble size of diet B. Past research focusing on poultry suggests that birds have a requirement for structural components that lead to increased nutrient utilization and performance. (12) Another possibility for variation in diet effect would be the method of processing for each diet: diet A was baked and diet B was extruded. Feed processing that combines shear forces, heat, residence time, and water may result in partial protein denaturation (13) and may result in changes in protein and other nutrient availability to a nonruminant animal. (14) Indeed, differences in thermal processes between baking and extruding in the current study could have affected nutrient availability.
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Amanda L. Foreman, MS, Jesse A. Fallon, DVM, and Joseph S. Moritz, PhD
From the Department of Animal and Nutritional Sciences, West Virginia University, G018 Agricultural Sciences Building, Morgantown, WV 26506, USA (Foreman, Moritz); and Cheat Lake Animal Hospital, 286 Fairchance Road. Morgantown. WV 26508, USA (Fallon).
Table 1. Selected nutrient analyses of the complete diets and the seed-based diet fed to cockatiels (n = 14) during a 12-day diet transition period. (a) Seed-based Measurement diet Diet A Diet B % Protein, Kjeldahl (N x 6.25) 12.1 15.4 16.9 % Calcium 0.29 1.19 0.42 % Phosphorus 0.386 0.519 0.449 % Phytic acid, ion exchange 0.85 0.79 1.00 % Nonphytate phosphorus (b) 0.145 0.296 0.167 Sodium, ppm 300 1210 1240 Vitamin A retinol and esters, IU/kg 1016 3681 7119 Vitamin [D.sub.2], IU/g <0.5 <0.5 <0.5 Vitamin [D.sub.3], IU/g <0.5 1.25 1.05 (a) Diets were analyzed at NP Analytical Laboratories (St. Louis, MO, USA). (b) % Nonphytate phosphorus (NPP) was calculated by the following equation: % NPP = % total phosphorus--(0.282 x % phytic acid). Table 2. Cockatiel transition strategy from a seed-based diet to a complete diet over a 12-day period. A 60-g total allotment of feed was provided each day. Day % Seed-based diet % Complete diet 1 90 10 2 80 20 3 70 30 4 60 40 5 50 50 6 50 50 7 50 50 8 40 60 9 30 70 10 20 80 11 10 90 12 0 100 Table 3. True amino acid digestibility of 2 complete diets (diets A and B) fed to cockatiels during a 12-day diet transition study. (a) % Digestible amino acid Diet A Diet B SEM P-value Alanine 0.7748 0.6949 0.0123 <.001 Arginine 0.9209 0.8720 0.0142 .03 Aspartic acid 1.3263 1.1069 0.0193 <.001 Cysteine 0.2425 0.2540 0.0072 .28 Glutamic acid 2.5529 1.9903 0.0246 <.001 Glycine 0.2161 0.4414 0.1150 .19 Histidine 0.3928 0.3191 0.0074 <.001 Isoleucine 0.6239 0.5862 0.0086 .01 Lanthionine 0.0303 0.1492 0.0008 <.001 Leucine 1.2903 1.0850 0.0151 <.001 Lysine 0.7360 0.7490 0.0243 .71 Methionine 0.4029 0.4193 0.0029 <.001 Phenylalanine 0.7458 0.7449 0.0108 .95 Proline 0.8763 0.6310 0.0135 <.001 Serine 0.5622 0.5774 0.0090 .25 Taurine 0.0222 0.0401 0.0153 .42 Threonine 0.5063 0.6606 0.0117 <.001 Tryptophan 0.1927 0.1321 0.0012 <.001 Tyrosine 0.4359 0.4331 0.0063 .76 Valine 0.7449 0.7219 0.0122 .20 (a) Amino acid profile was analyzed at the Agricultural Experiment Station Chemical Laboratories, University of Missouri (Columbia, MO, USA).
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|Title Annotation:||Research Brief|
|Author:||Foreman, Amanda L.; Fallon, Jesse A.; Moritz, Joseph S.|
|Publication:||Journal of Avian Medicine and Surgery|
|Date:||Jun 1, 2015|
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