Figure 4.

Frequency of aggressive behaviors at day 0 (pre-treatment) and day 14 (post-treatment) in probiotic fed hens and regular diet fed hens followed by the paired social test (n = 12). (A) The frequency of threat kick. (B) The frequency of aggressive pecking. (C) The frequency of feather pecking. (D) The frequency of threat. The exhibition of aggressive behaviors in the regular diet fed subordinates was not affected by treatment (p > 0.05, respectively), while the frequency of threat kick (p = 0.04) was reduced, aggressive pecking (p = 0.053) tended to be lower, and feather pecking was lower (60%, p = 0.33) in probiotic fed dominant hens post-treatment. Notes: The treatment effects on the measured behaviors were reversed between dominants and subordinates during the second social rank test. a,b Between the frequency at day 0 and day 14, least square means lacking common superscripts differ (p < 0.05); and † trend difference (0.05 ≤ p < 0.10). A modified copy from Hu et al. [178].