Investigating behavior changes of laying hens molted by high dietary zinc

Introduction The commercial egg industry commonly uses induced molt procedures to rejuvenate flocks for a second or third laying cycle. Molting may be induced by feed withdrawal for up to 10 days (7), water withdrawal for 2 days (19), or both, along with a reduction of day length (14). Such programs cause concern about animal welfare because it is thought that they may be harmful to hens (28). Given the concerns for potential bird stress, various methods of nutrient restriction that would avoid long term feed withdrawal have been investigated (20, 24). One of the alternative methods for molt induction is high-dietary Zn (4).
Materials and Methods In this study, a total of 30 Hy-line W-36 leghorn hens (at 50 wk old) (1400 ± 150 g), were randomly assigned to 5 replicate. Ten cages (3 hens in each cage) on both the upper and lower tiers were considered to observe behavior patterns. Data recording of predetermined behavioral patterns were carried out using five Camera Digital Video Recorder Multiplexer System. Behavior recording began at 9:00 h each day and ended at 11:00 h and a second observation starting at 16:00 p.m and ended at 18:00 p.m. Total of ten cages (containing 3 hens/ cage (30 hens total)) were used to collect 5 behaviors (feeding, drinking, nonnutritive pecking, preening and aggression pecking) and one posture (sitting). The following ethogram was adopted from Webster (27) feeding defined as pecking behavior directed toward the feed trough or toward a neighboring feed trough. Drinking was defined as the appearance of ingesting water from the nipple at the near of the cage. Nonnutritive pecking was defined as non aggressive pecking at anything other than feed, which included cage pecking, feather pecking, bill pecking and air pecking. Preening behavior involved the manipulation of the plumage with the beak. Aggressive was the sum of pecks that occurred within a cage or between neighboring cages. Sitting was defined as a crouched posture with shanks or breast in contact with the cage floor.
Results and Discussion Percentage of observation of all behaviors except for non-nutritive pecking was significantly affected by high dietary zinc (P