Effect of environmental enrichment on weaned piglets: physiological responses

The aim of this research consisted in assessing the effect of various kinds of environmental enrichment (EE) on the physiological responses of weaned piglets. The mean age of the 96 piglets that participated was 27 days. The piglets were weaned and then housed under two conditions: with no disruption of the social order (SO), and with disruption of the social order (DSO). After establishing the two experimental conditions, we proceeded to evaluate four different treatments; namely, control (C), suspended ropes (SR), aromatized bottles (AB) and pet toys and balls (PTB). The protocol required drawing three blood samples: at 30 (T-30), 60 (T-60) and 90 min (T-90) after weaning. The DSO piglets had higher pH and haematocrit levels than those weaned in the SO condition (P < 0.05). Also, pCO(2), potassium (K+) and base excess (BE) concentrations were higher in the SO animals than in those in the DSO group (P < 0.05). The control piglets, which did not receive any type of EE, showed higher pCO(2) levels, but lower glucose and pH (P < 0.05) values, while the ones enriched with SR had increased lactate levels, but lower values for pH and HCO3- compared to the piglets in the other EE treatment regimens (P < 0.05). The SR-enriched piglets had higher lactate and haematocrit levels, but lower values for pH and bicarbonate (HCO3-) than the animals in the other EE groups (P < 0.005). The piglets subjected to sensorial EE with AB had higher plasma glucose than the ones in the other groups (P < 0.005). Finally, the PTB-enriched subjects showed higher Na+ levels than controls (P < 0.005). The alterations that were found to be related to the factor sampling time were more pronounced at T-30 (P < 0.05) than T-60 and T-90. These results indicate that the conditions (SO, DSO) and EE (C, SR, AB, PTB) under which the piglets were weaned influenced the blood variables measured in the study.