Zhang Jinyue, Yu Langchao, Yin Guoan
College of Animal Science and Veterinary Medicine, Heilongjiang Bayi Agricultural University, Daqing 163319, China.
Animals (Basel). 2022 May 5;12(9):1184. doi: 10.3390/ani12091184.
The stall-housing system is commonly used in the modern swine industry in many countries; however, long-term space restrictions can cause affective and physiological abnormalities in sows. The pupil light reflex (PLR) can reflect the psychological and neurological changes in animals, and confined sows show higher pupillary rigidity. However, the PLR differs between same-parity sows, suggesting differences in behaviors and affective states between parity groups. We subjected confined Yorkshire × Landrace sows of parity 0, 2, and 5 to a PLR test and accordingly assigned them to the weak PLR (WR) group (n = 20) or the strong PLR (SR) group (n = 22). We then observed the sows’ behaviors and performed a sucrose/quinine response test and novel object test (NOT) to assess the differences in their affective states. The standing and lateral lying behaviors of the sows were less frequent in WR than in SR (p < 0.05), whereas ventral lying and sitting behaviors was more frequent in WR than in SR (p < 0.05). No changes in chewing behaviors and sucrose/quinine responses were observed (p > 0.05); however, the numbers and duration of novel object contact were lower and the novel object response latency time was longer in WR than in SR (p < 0.05). Regarding parity, standing and lateral lying behaviors were less frequent and ventral lying and sitting behaviors were more frequent at parity 5 than at parity 0 (p < 0.05). Bar-biting, rooting, trough-biting, and sucrose response score were lower at parity 5 than at parity 0 (p < 0.05), and vacuum chewing behavior and quinine response score were higher in sows of parity 5 than in those of parity 0 (p < 0.05). NOT showed that the number of contacts and contact duration in sows decreased with increasing parity (p < 0.05), and the response latency time was longer in sows of parity 5 than in those of lower parity (p < 0.05). In conclusion, the behavioral expression and responses of confined sows to novel objects differed between PLRs. The evaluation of the affective state of sows also revealed marked differences with increasing parity. Thus, confined sows with WR and high parity apparently suffer from more severe psychological problems, and PLR may be a potent indicator for evaluating the affective state of confined sows.
限位饲养系统在许多国家的现代养猪业中普遍使用；然而，长期的空间限制会导致母猪出现情感和生理异常。瞳孔对光反射（PLR）可以反映动物的心理和神经变化，限位饲养的母猪表现出更高的瞳孔僵硬程度。然而，不同胎次的母猪PLR存在差异，这表明不同胎次组之间在行为和情感状态上存在差异。我们对胎次为0、2和5的限位饲养的约克夏×长白母猪进行了PLR测试，并据此将它们分为弱PLR（WR）组（n = 20）或强PLR（SR）组（n = 22）。然后我们观察了母猪的行为，并进行了蔗糖/奎宁反应测试和新物体测试（NOT），以评估它们情感状态的差异。WR组母猪的站立和侧卧行为比SR组少（p < 0.05），而WR组母猪的腹卧和坐立行为比SR组更频繁（p < 0.05）。未观察到咀嚼行为和蔗糖/奎宁反应有变化（p > 0.05）；然而，WR组母猪接触新物体的次数和持续时间较少，对新物体的反应潜伏期比SR组更长（p < 0.05）。关于胎次，5胎母猪的站立和侧卧行为比0胎母猪少，腹卧和坐立行为比0胎母猪更频繁（p < 0.05）。5胎母猪的咬栏、拱地、咬槽行为和蔗糖反应评分比0胎母猪低（p <
