Effect of allowing to use paddock and administering gamma-amino acid for welfare of piglets

The objects of this study were to compare the endocrine and behavioral effects among three welfare-intentioned treatments and to discuss the effective index of welfare level on piglets. Thirty Landrace x Large White piglets that were 7-8 weeks old were investigated. These piglets were evenly divided into three treatment group: GABA (orally administered 20 mg/kg/day of gamma-amino acid), paddock (allowed to use a paddock (10 x 10 m) situated next to the pen) and control (non-treated). Each pen of the three groups was equal in area (3.1 x 3.6 m) and concrete floor. Behavior, salivary cortisol, growth performance, and skin lesion in the body were measured regularly during 3 weeks. Self maintenance behavior was recorded by 5-min scan sampling, and social behavior and conflict behavior were recorded by continuous recording. As results, salivary cortisol level and growth performance were not significantly different between treatments. And these values are within normal limits, suggesting that piglets in the three treatments should not feel stress. As for behavior, the proportion of resting was lower, and feeding, drinking and eliminating were higher in GABA group than in control group. Fighting was lower and ear-biting, and penmate-sucking were higher in GABA group than in control group. In paddock group, resting, feeding, litter-eating and drinking were lower and exploring was higher than in control group. Threat, playing and penmate-sucking were higher and ear-biting, and crib-biting were lower than in control group. The number of skin lesions in the ear, shoulder, flank and back was significantly lower in GABA and paddock groups. As described above, behavior was different between treatments, especially in exploring and playing. In addition to this, conflict behavior occurred even in paddock group that piglets were most active, and its proportion varied quantitatively. Thus, piglets seem to express the conflict behavior with an eye to accommodating themselves to their environment. In conclusion, exploring, playing and conflict behavior should be the effective index of welfare level on piglets, and these behavior should need to be measured comprehensively.