All behavioral data were obtained from the videotapes. Behaviors were analyzed from images digitally recorded from 08:00 h to 18:00 h on days 25, 50, and 75 (day 0 = birth day). Video tapes were analyzed using a video recorder with jog-shuttle function. Instantaneous scan sampling was carried out at 2-min intervals. All video recordings were viewed by one trained observer who was blinded to the treatment to eliminate subjective bias and inter-individual discrepancy (Li and Wang, 2011).