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https://hdl.handle.net/2142/22918
Description
Title
Studies of pig social groupings
Author(s)
Moore, Aaron Scott
Issue Date
1990
Doctoral Committee Chair(s)
Gonyou, Harold W.
Department of Study
Animal Sciences
Discipline
Animal Sciences
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Agriculture, General
Agriculture, Animal Culture and Nutrition
Language
eng
Abstract
Experiments were conducted which focused upon specific aspects of the social environment of the pig and how manipulation of this environment through dynamic grouping affects the well-being of the animal. The broad objectives were to better understand the process of group formation and the importance of social stability within groups of pigs. The first study examined the effects of dynamic and static grouping and pen size on behavior, injuries, productivity and immunophysiology of growing pigs. The possibility of reducing aggression following regrouping in growing pigs by creating large within-pen weight variation via dynamic grouping was of particular interest. Time spent fighting by newly regrouped pigs in dynamic pens was reduced by more than 50% as compared to the levels recorded in static groups. However, the number of fights was three times greater for dynamically grouped pigs. Increases in the combined morbidity and mortality rate, live weight variation and injuries among pigs in dynamic groups as well as increases in plasma cortisol levels, neutrophil-to-lymphocyte ratios and a decrease in immune response in all pigs which were regrouped lead to the conclusion that dynamic grouping reduces the overall well-being of growing pigs and should be avoided. The second and third studies examined the effectiveness of a computer-controlled feeding system for dynamically group-housed gestating gilts. Of particular interest was the behavior of gilts housed in large dynamic groups and its influence on their well-being as compared to the well-being of gilts housed in standard gestation stalls. The daily pattern of feedstation use was characterized in two groups of 22 gestating gilts. Several faults in the design of the gating system were noted while observing these gilts. Most troublesome was that over 16% of all feeding visits were interupted by a second gilt which had circumvented the gating system. Many times this resulted in the primary gilt being displaced from the stall and losing a portion of her daily feed allotment to the second gilt. All in all, the gating system was unsatisfactory and was most likely a major source of frustration to the gilts using it. Other problems encountered during the trial were collar losses and the failure to eat following regrouping. While there was line difference in the productivity of gilts in both housing systems, injuries were more frequent and severe in dynamically grouped pigs using the computerized feeder. These results suggest that the welfare of computer-fed gilts in dynamic groups was reduced as compared to individually housed gilts. This was due in large part to problems associated with the formation and composition of the group, rather than the performance of the feedstation per se.
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