Effect of high stocking density on performance, egg quality, and plasma and yolk antioxidant capacity in laying hens supplemented with organic chromium and vitamin C

This study was conducted to investigate the effects of dietary supplementation of chromium-methionine (CrMet) and vitamin C on performance, egg quality measurements, and plasma antioxidant capacity in laying hens subjected to high stocking density. A total of 360 Hy-Line W-36 laying hens, 26 wk of age, were used in a 2 x 2 x 3 factorial arrangement of treatments consisting of 2 cage densities [5 or 7 hens/cage (40 x 45 cm(2))], 2 supplemental vitamin C levels (0 and 500 mg/kg as L-ascorbic acid), and 3 supplemental Cr levels (0, 500, and 1000 mu g/kg as CrMet) with 5 replicate cages per treatment. The hens were kept in wire-floor cages in an environmentally-controlled room. After a 2-wk adaptation, the 70-d study was initiated and it was divided into two 35-d periods (28-33 and 33-38 wk of age). Results showed that although subjecting hens to high stocking density had no effect on egg production percentage during 28-33 wk of age, it decreased (P=0.031) during the 33-38 wk of age, resulting in a marked reduction (P=0.038) in egg mass. Dietary Cr supplementation (500 and 1000 mu g/kg) increased (P < 0.01) egg production and egg mass during both 35-d periods, and improved (P=0.005) feed conversion ratio (FCR) during the first 35-d period. There was a stocking density x vitamin C interaction (P=0.018) for FCR values during the first 35-d period, so that supplemental vitamin C improved FCR to a greater extent in high stocking density-challenged hens. Dietary CrMet supplementation (500 and 1000 mu g/kg) increased (P=0.001) feed intake during the second 35-d period. Shell thickness was greater (P=0.015) in hens under high stocking density challenge during the second 35-d period. Subjecting hens to high stocking density decreased (P=0.007) plasma vitamin C concentration, while plasma vitamin C level was increased (P < 0.05) as the result of dietary supplementation of vitamin C. Dietary supplementation of CrMet (500 and 1000 mu g/kg) increased plasma vitamin C level only in high stocking density-challenged hens, resulting in a stocking density x Cr interaction (P=0.039). Although high stocking density increased (P < 0.05) plasma and yolk concentrations of malondialdehyde (MDA), supplemental vitamin C decreased (P < 0.05) plasma and yolk MDA contents. Similarly, dietary inclusion of CrMet (500 and 1000 mu g/kg) decreased (P=0.046) plasma MDA level. The present findings indicate that dietary CrMet supplementation could increase antioxidant capacity in stressed hens, which improve production performance of laying hens. (C) 2015 Elsevier B.V. All rights reserved.