Abstract
In the two previous reports, we described the influences of the life-long in-door group-feeding upon the dunging sites of pigs in particular relationship to the conditions of the adjacent pigpens and the structure of pigpens. In the present study, we have conducted experiments on the relationship between the dunging behaviors of pigs within pigpens with attaehed open yards and the external environmental factors. The results were as described below.
1) Under the conditions kept in a pigpen with free access to the open yards, the pigs tend to prefer dunging outdoors to that within the pigpen. This would be attributable to the factors of instability in the outdoor yards such as the irregularities of weather and noises and passage of other animals including humans, for which reason the pigs may instinctively prefer using the inside of the pigpen as the resting sector to the open space, which is used for dunging and walking area. However, if excessive irregularities causing horror or sense of over-instability to them such as stormy wind or heavy rainfall are noted, pigs tend to hesitate and very often choose the inside of the pigpen as the dunging area.
2) It appeared that pigs can adapt themselves for the gradual fall of temperature, but they tended to be hesitant to go outdoors on the days with sudden drop in the atmospheric temperature and tended to dung in the pigpens.
3) Comparison between winter and summer in terms of their dungings revealed that more or less dungs were found in the pigpens in the winter, whereas the majority of the summer days saw no dunging in the pigpen. This finding may be attributed to the fact that the pigs take their resting sites all over the floor of the pen, whereas, in winter, they rest in groups to warm each other, by which considerably large space is left in the floor for their dunging.
4) It was noted that once the diarrheal feces by a pig soiled the floor of the pigpen, the others tended to fllow it with dunging in the pen. This phenomenon suggested the likelihood that there would be a type of learning effects by the pigs to refrain from dunging in the pen by keeping the inside of the pen as clean as possible at all times.
5) As a general trend, it was noted that the size and structure of a pigpen have little to do with the dunging behaviors if there is an open yard attached. However, if the pigs in the pigpen on the opposite side of the partitioning fence are kept confined within it so as to force their dunging therein, the pigs kept in the pigpen on this side also tended to dung within the pigpen on this side possibly because they are lured by the pigs on the opposite side. It was therefore conjectured that it is desirable to have all the partitioning fences in the pigpen made of boarded type which will not allow any see-through.
