Establishment of biochemical reference values for backyard chickens in Colorado ( Gallus gallus domesticus )

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.