Comparison of Plasma Protein Fractions and Electrophoretograms in Non‐Laying and Egg‐Laying Domestic Chickens

BACKGROUND: Protein electrophoresis (EPH) is a valuable diagnostic tool in veterinary medicine, particularly in non-mammalian species where albumin measurement has historically been considered inaccurate by routine biochemistry analyzers. Physiologic processes such as egg-laying result in altered protein production, presenting a challenge in differentiating physiologic from pathologic processes on EPH. OBJECTIVE: We aimed to evaluate differences in total protein and protein fraction concentrations, as determined by the Biuret method and capillary zone electrophoresis (CZE), respectively, between non-laying and egg-laying healthy female chickens (Gallus gallus domesticus). METHODS: Blood was obtained from 24 healthy female chickens consisting of 12 Red Star and 12 Cornish Cross breeds, 36 and 14 months old, respectively. Plasma protein electrophoresis was performed on heparinized plasma on the Sebia MINICAP instrument. Median results for total protein and each protein fraction between non-layers and layers were compared with the Mann-Whitney test. RESULTS: Layers had significantly higher total protein (median 5.2 vs. 4.7 g/dL; p = 0.0015), prealbumin fraction (1.7 vs. 0.2 g/dL; p < 0.0001), and A/G ratio (1.15 vs. 0.8; p = 0.0012). Layers had significantly lower albumin (1.15 vs. 1.7 g/dL; p = 0.0005) and alpha-2 globulins (0.1 vs. 0.2 g/dL; p = 0.0003). The Cornish Cross had the lowest prealbumin concentration (0.9 g/dL) of layers, while the Red Stars had the highest prealbumin concentrations (0.5, 0.6 g/dL) of non-layers. CONCLUSIONS: Egg-laying in chickens is characterized by a higher total protein due to an increased prealbumin fraction, as determined by CZE, with breed differences noted. It is important to recognize these physiologic differences when interpreting EPH from laying chickens.