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An enriched environment is widely used to improve domestic animals’ welfare and promote their natural behaviors. Music can reduce abnormal behavior in humans, nonhuman primates, and rodents. However, little is known about the effects of music on pigs. This study aims to explore the effects of repeated music stimulation on the behavior, physiology, and immunity of growing pigs. A total of 72 hybrid piglets (Large White × Duroc × Minpig) were randomly divided into three groups, including music (Mozart K.448, 60 to 70 dB), noise (recorded mechanical noise, 80 to 85 dB), and control (natural background sound, 0.05). In conclusion, short-term music stimulus (8 d) reduced the stress response, whereas long-term music stimulus (60 d) enhanced the immune responses. In addition, the noise increased the aggressive behavior, and long-term noise reduced the immunity of the growing pigs.

Enrichment environment is widely used to improve the welfare of domestic animals and satisfy their natural behavior. Music as an enriched environment can reduce abnormal behavior in humans, non-human primates and rodents. The aim of this study was to investigate the effects of repeated music stimuli on the behavior, physiology and immunity of growing pigs. A total of 72 5-week-old hybrid piglets (Large White × Duroc × Minpig) were randomly divided into three treatments groups of the music group (Mozart K.448, 65–70 dB), the noise group (mechanical noise, 85–90 dB) and the control group (silence, less than 40dB). During 60 days of auditory exposure, the behavioral responses, cortisol level and immune horizontal of the piglets were measured. The results showed that the active behavior of the growing pigs increased and lying behavior decreased in the music group compared to the control group (P < 0.05). The music stimulus increased tail wagging, tail in curl and playing behaviors (P < 0.05). The noise stimulus increased aggressive behavior (P < 0.05) but had no effect on the exploring and manipulative behaviors (P > 0.05). The frequency of the event behaviors decreased with the time of auditory stimuli (P < 0.05). Short-term music stimulus had a lower cortisol level than the noise and control groups (P < 0.05). Long-term music stimulus increased the level of IgG, IL-2 and IFN-γ (P < 0.05) and decreased the IL-4 level (P < 0.05). Noise stimulus reduced the level of IgG (P < 0.05) but had no effect on the level of IL-2, IL-4 and IFN-γ (P > 0.05). In conclusion, music stimulus triggers the pigs to show more positive behaviors, and the short-term music stimulus can reduce the stress response, while the long-term music stimulus can enhance the immune responses in the growing pigs.

Pupillary reflex has been used as a method to examine psychological problems in human clinics and mental disease research. Intensive animal farming has been shown to lead to chronic stress resulting in depression; however, comparing with humans we lack an effective clinical method to clinically inspect these psychological problems in animals. The goal of this study was to investigate the effect of age and housing conditions (confined crates vs. group pens) on pupillary light reflex (PLR) of sows to explore whether PLR can be used as an effective way to measure the psychological state of farm animals. In total, 270 pregnant sows were selected for PLR testing and divided into 6 treatments (45 sows per treatment) of 2 different environments (group-housed pen and confined gestation crates) and 3 parities (first, third, and fifth parities). Six selected pupil parameters: 1) latency of the pupil constriction onset (LAT); 2) the percent of the constriction (CON); 3) average constriction velocity (ACV); 4) maximum constriction velocity (MCV); 5) average dilation velocity (ADV); and 6) time of 75% recovery after constriction (T75) were examined. The results showed that there was no difference found in these PLR parameters between the breeds (P > 0.05) but the significant effects were found on LAT, CON, ACV, and MCV by age (P < 0.01). The group-housed sows had significantly higher CON, ACV, and MCV than those in the confined crates (P < 0.05). In conclusion, the pupillary light reflex of the sows was not affected by breed but by age. The results also indicate that some of PLR parameters were sensitive to housing conditions and suggest that ACV and MCV have potential to be sensitive indicators in relation to the psychological problem of sows.