The authors of "Establishment of biochemical reference values for backyard chickens in Colorado (Gallus gallus domesticus)" 1 would like to provide additional reference value data generated during this study.A full description of the reference population, sample collection, and statistical evaluation can be found in the peer-reviewed manuscript in this issue. 1 Concurrent with other biochemical evaluations, heparinized plasma samples were evaluated using an assay targeting mammalian albumin to evaluate the rapid protein binding of bromocresol green (BCG) using bovine serum albumin as a reference standard on the Cobas analyzer (Roche Diagnostics, Indianapolis, IN, USA). The traditional biochemical mammalian globulin ([biuret total protein] -[BCG-bound protein]) and mammalian albumin:globulin ([BCG-bound protein]/([biuret total protein] -[BCG-bound protein]))calculations were also performed.The Mann-Whitney test documented that hens had higher median values from the mammalian albumin assay (median difference 0.2 g/ dL, 95.03% CI 0.1 to 0.3 g/dL). Reference values generated from all reference individuals and after partitioning for sex are provided in Table 1. The Mann-Whitney test did not document a statistical difference between samples collected in summer and winter, Table 2.

Background Previous literature pertaining to biochemical RIs of domestic chickens has primarily focused on commercial production flocks and not backyard birds. Objective We aimed to establish biochemistry RIs for privately‐owned backyard chickens (Gallus gallus domesticus) using reference laboratory equipment. Methods Samples were collected from 123 presumably healthy adult chickens between 2017 and 2019 from 22 different flocks in Colorado. Heparinized blood was obtained, and a biochemistry profile was evaluated, including sodium, potassium, chloride, calcium, phosphorous, uric acid, AST, CK, glucose, cholesterol, and total protein. Reference values were created according to current American Society for Veterinary Clinical Pathology recommendations. Results Differences in measurand intervals compared with previous literature were found for sodium, calcium, total protein, potassium, phosphorus, uric acid, and glucose. Hens were found to have higher median calcium (17.9 mg/dL vs 11.2 mg/dL [P = .0001]), total protein (5.2 g/dL vs 4.8 g/dL [P = .0046]), and potassium (3.80 mEq/L vs 3.48 mEq/L [P = .0267]) concentrations, as well as lower sodium (155 mEq/L vs 158 mEq/L [P = .0046]) concentrations, calculated osmolalities (310 mOsm/kg vs 314 mOsm/kg [P = .0249]), and AST (165 U/L vs 194 U/L [P = .0121]) activities, than roosters. Seasonal variation was found between summer and winter samples for median sodium (144 mEq/L vs 148 mEq/L [P = .0008]), chloride (111.8 mEq/L vs 113.5 mEq/L [P = .0033]) concentrations, calculated osmolalities (306 mOsm/kg vs 311 mOsm/kg [P = <.0001]), and AST (185 U/L vs 159 U/L [P = .0053]) and CK (1098 U/L vs 770 U/L [P = .0007]) activities. Conclusions This study presents biochemical reference values for backyard chickens in Colorado that can be a basis for evaluations in similar settings.