Efficacy of Probiotic in Improving Welfare and Mitigating Overcrowding Stress in Broilers

This study was conducted to investigate the efficacy of probiotic in improving welfare of broilers reared under low stocking density (LSD) and mitigating high stocking density (HSD) stress. A total number of 240 chicks were sub divided into four groups with three replicates for each. Two groups were reared under LSD (10 bird/m2).; 48 chicks (16 bird/ replicate) for each and another 2 groups were reared under HSD (15 bird/m2); 72 chicks (24 bird/ replicate). At each density, one group was supplemented with Protexin® and the other was not supplemented. Blood corticosterone (CS) level was measured and behavior of broilers was recorded weekly. At the end of the growing cycle, behavioral welfare fear response test (time of first attempt to stand, number of attempts to stand and tonic immobility duration) was performed and brain monoamines (serotonin, norepinephrine and dopamine) concentrations were measured. As a result, HSD stress increased the time birds spent to perform the first attempt to stand and prolonged TI duration. However, Protexin® supplementation only reduced the time of first attempt to stand at higher density without alteration of the number of attempts required to induce TI. No significant improvement in fear response in LSD birds supplied with Protexin®. Furthermore, HSD stress decreased feeding, drinking and walking duration. However, Protexin® supplementation improved feeding, drinking and walking behaviors at LSD and did not improve behaviors of birds at HSD. Moreover, HSD increased CS levels at the 4th, 5th and 6th week of the growing cycle. However, Protexin® supplementation had a decreasing effect on CS levels in the birds reared at HD at the last two weeks of the growing cycle. In addition, brain serotonin concentration was increased in birds reared at HD without Protexin® supplementation and showed no alteration in that supplemented with the probiotic at LSD and HSD. Data suggests that, Protexin® supplementation may be beneficial in improving welfare (behavior al indicator) of broilers reared at LSD and alleviate some effects of HSD stress on birds.