Injurious pecking behavior of Pekin ducks on commercial farms: characteristics, development and duck welfare
Injurious pecking is one of the major welfare concerns for poultry and other captive birds. Injurious pecking behavior can result in welfare problems including feather and skin damage, pain, substantial heat loss because of feather loss, and even death of the recipient bird. Injurious pecking can also cause economic losses because of reduced production efficiency, increased mortality and reduced feed conversion ratio. Injurious pecking behavior includes feather pecking, feather picking, cannibalism and aggressive pecking. Feather pecking, when a bird uses its beak or bill to peck at the feathers of another bird, can be categorized as either gentle feather pecking (repeated and light pecks) or severe feather pecking (singular and hard pecks). Feather picking is described as a self-damaging behavior that occurs in psittacine species such as parrots and also in ducks. Cannibalism is classified as either tissue pecking (persistently forceful pecks directed at exposed skin) or vent pecking (pecks directed at the top of cloaca or below the cloaca). Unlike feather pecking, feather picking and cannibalism, which are not associated with aggression, aggressive pecking establishes and maintains the dominance hierarchy. Limited studies have examined injurious pecking of Pekin ducks, but results from previous research examining duck picking behavior and feather quality suggested that ducks pick mostly at themselves and that the development of picking is related to feather growth and worsens with age. Scant information is available regarding the prevalence of injurious pecking behavior and characteristics of the behavior.
To address some of the gaps in the knowledge regarding injurious pecking behavior of ducks, this study examined 1) age-related changes in frequencies and durations of preening behavior and injurious pecking behavior of Pekin ducks, including self-picking and feather pecking; 2) the body locations most frequently affected, and whether feather removal and feather eating occurred concurrently with injurious pecking; 3) the prevalence of injurious pecking behavior; and 4) age-related changes in duck welfare that may be associated with injurious pecking. Information about preening behavior was recorded because injurious pecking and preening behavior may have similar age-related patterns, as previous studies have suggested that increased levels of preening behavior are related to feather growth.
Data were collected on 5 commercial duck flocks on 5 farms. Welfare data were collected from all 5 flocks and behavior data were collected from 2 of the 5 flocks. For the two flocks, duck behavior was video-recorded over two consecutive days at 20-22d (Period 1), 27-29 d (Period 2), and 34-36 d (Period 3). Scan sampling and focal animal sampling were used to analyze the video recordings and determine the frequencies and durations of injurious pecking behavior (gentle feather pecking, severe feather pecking, self-picking and aggressive pecking). For scan sampling, the percentage of ducks performing injurious pecking behavior were recorded every 30 min from 0900h to 1500h. For both scan and focal animal sampling, the viewing area of each camera installed in the barn was divided into eight equal squares (observation areas), of which four were randomly selected for analysis. For focal animal sampling, one duck was randomly selected from each observation area and observed for 30 min from 0945h to 1015h and 1345h to 1415h ((n=8 ducks per camera (4 ducks in the morning and 4 ducks in the afternoon) and n=24 ducks per barn)) to determine the duration and frequency of injurious pecking behavior and preening behavior. For all five flocks, duck welfare (feather quality, feather cleanliness, nostril cleanliness, eye condition, footpad condition and gait) was assessed in 100 ducks from each flock between 17-18 d (Period 1), 29-30 d (Period 2), and 36-37 d (Period 3). Welfare data and frequencies of behaviors from focal animal sampling were analyzed using the GLIMMIX procedure (SAS 9.4). Scan animal sampling data and behavioral durations from focal animal sampling data were analyzed using the MIXED procedure (SAS 9.4).
The most frequently observed form of injurious pecking behavior was gentle feather pecking, which increased from Period 1 to Period 2 (P < 0.001), then declined from Period 2 to Period 3 (P < 0.001). Gentle feather pecking was most frequently directed at the tail, wings and back. Removal of feathers was observed 13 times, and feathers were eaten 7 times in the 6 days of video observation. Ducks’ eye condition, feather cleanliness under the tail, and feather quality on all the assessed body locations, except for the neck, worsened with age. Age was a major factor affecting the development of injurious pecking behavior including the proportion of ducks performing gentle feather pecking behavior (P < 0.001), frequency and duration of gentle feather pecking behavior (frequency: P < 0.001; duration: P < 0.001), and other injurious pecking behavior (frequency: P = 0.038; duration: P = 0.036). From scan sampling, 1.85% of the ducks were observed performing severe feather pecking behavior, 6.84% of the ducks were observed performing aggressive pecking behavior, and no duck was observed performing self-picking behavior in the total of 1082 ducks performing injurious pecking behavior across the 3 periods. From focal sampling, 83.33% of the ducks were observed performing gentle feather pecking behavior, 13.89% of the ducks were observed performing severe feather pecking behavior, 16.67% of the ducks were observed performing aggressive pecking behavior, and only 1.39% of the ducks were observed performing self-picking behavior of the total of 288 ducks observed. Frequency and duration of preening behavior increased from Period 1 to Period 2 (frequency: P = 0.004; duration: P < 0.001), then declined from Period 2 to Period 3 (frequency: P < 0.001; duration: P < 0.001).
In conclusion, feather pecking between conspecifics was the most frequently performed pecking behavior of commercial Pekin ducks. Age was a major factor affecting the development of pecking behavior, which peaked at 27-29 d. The body locations that injurious pecking behaviors were most frequently directed at were the tail, wings and back, consistent with the welfare condition results that indicated a worsening tail, wing and back feather quality with age. Feather removal and feather eating were infrequently observed, which might indicate that injurious pecking behavior in Pekin ducks is not for the purpose of pulling out and eating the feathers. The frequency and duration of gentle feather pecking and preening behavior followed a similar pattern with age; however, further research is needed to evaluate whether these behaviors are associated. This study provided more details about age-related changes in injurious pecking behavior and welfare of commercial Pekin ducks. However, further work is needed to investigate specific causes of and methods to reduce injurious pecking behavior of Pekin ducks.