Effects of Rearing Densities on Behavior Characteristics in Korean Native Broilers

Rearing density is a major factor in welfare production and health of broiler chicks. An experiment was conducted to investigate the effect of rearing density on the behavioral characteristics of Korean native chicks. In the study, 20, 30, and 40 chicks per pen (3.17 $m^2$) were used in each treatment and randomly allotted to 6.3 bird/$m^2$, 9.5 bird/$m^2$, and 12.6 bird/$m^2$ density, respectively. The broilers' behavior was recorded for 12 hours continuously during 1 to 8 weeks of age. The time budgets (standing, sitting, and walking) and frequencies of certain behaviors (drinking, feeding, preening, scratching, dust bathing, flapping, aggressive pecking, and pecking) in the broilers were checked during the day. The behavioral characteristics in the early period (1 to 4 weeks) were compared to the later period (5 to 8 weeks) to know the changes in each behavior as the chicks matured. It was observed that 40 chicks per pen showed significant decrease in feed intake and body weight. Corticosterone hormone was higher in the order of 12.6 bird/$m^2$ > 9.5 bird/$m^2$ > 6.3 bird/$m^2$ (p<0.05). The behaviors of standing and sitting were the highest in groups of 30 and 40 respectively. The walking behavior was gradually decreased as rearing density increased. The frequencies of the other behaviors also decreased in a high density treatment; especially for feeding, drinking, preening, and pecking. These tendencies widened the gaps of behaviors as time passed. It was concluded that a group of 20 chicks (6.3 bird/$m^2$) was the proper rearing density among these three treatments. Broilers in the lower rearing density showed more activity than that with higher density and therefore this environment may lead to better welfare condition.

사육밀도가 토종육계의 행동특성에 미치는 영향

본 실험은 사육밀도에 따른 토종육계의 행동을 분석한 것이다. 10일령의 토종육계(한협3호)를 3.17 $m^2$의 칸에 각각 20수, 30수 그리고 40수를 수용시켰다. 각각의 사육밀도는 6.3수/$m^2$, 9.5수/$m^2$ 그리고 12.6수/$m^2$ 이다. 사료섭취량 및 체중은 40수 처리 구에서 가장 낮게 나타났고, 혈장 내 coriticosterone의 농도는 20수 처리 구에서 가장 낮게 나타났다. 닭의 행동은 하루에 12시간씩 일주일에 이틀, 총 8주간 녹화한 후 관찰하였다. 서기, 앉기 그리고 걷기는 행동 소요시간을 측정하였고 음수, 섭식, 몸단장, 긁기, 모래욕, 날개짓, 쪼기 그리고 다른 닭 쪼기는 빈도수를 측정하였다. 서기는 30수 처리 구에서, 앉기는 40수 처리 구에서 가장 높게 나타났고 걷기는 사육밀도가 증가할수록 낮게 나타났다. 다른 행동의 빈도수 또한 사육밀도의 증가에 따라 감소하였는데 특히 음수, 섭식, 몸단장 그리고 쪼기에서 그 차이가 크게 나타났다. 그리고 이러한 행동의 차이는 사육 후기로 갈수록 차이가 커졌다. 모든 처리구 중 활동적인 행동을 많이 하는 20수 처리 구(6.3수/$m^2$)가 타 처리구 보다 상대적으로 복지측면에서 가장 적합한 사육밀도라고 판단된다.