Effects of Sow Vocalization and Scent on Complete Blood Cell Count During Early Weaning Period

Abstract Piglets are deprived of the touch, sound, and smell of their sow after weaning which results in biological stress. The present study investigated continuing exposure of sow vocalization and scent during the early weaning period on complete blood cell count. A total of 12 litters, 8 piglets (4 male and 4 female) per litter were selected at weaning and assigned to 1 of 4 experimental treatments: control, O (olfactory group with scent and no vocal stimulation), V (non-olfactory with vocal stimulation), VO (vocal stimulation and olfactory stimulation) as a 2x2 factorial arrangement. Vocal stimulation was emulated by an audio recording of the sows, which was gathered between day-7 and day-14 of sow lactation. It was collected from 6 sows and compiled into a comprehensive audio file including all the vocal output of the sow. The VO group was exposed to sow vocal for 20 minutes, followed by an empty hour on loop for seven days postweaning. For olfactory stimulation, cotton fabric was rubbed on the udders of the sow and vacuum sealed. The respective scent of the sow was placed in a mesh basket outside of the pen for approximately 48 hours. Blood samples were collected on day-1, day-2, day-6, and day-28 into K2EDTA vacutainer tubes. The blood was processed within 6 hours of collection using an automatic hematological analyzer (Hemavet 950S). Data were analyzed using mixed procedure of SAS (Cary, NC) with vocal, scent and day as main effects. Interactions between day x vocal showed statistical significance (P = 0.0215) with both the vocal and non-vocal groups having a reduction on mean platelet volume (MPV) from d 0 to d 2 and while the non-vocal group continued an upward trend from d 2 to d 28, vocal group failed to restore MPV levels until d 28. As for Platelet (PLT) in the day x scent interaction, non-scent group increased PLT from d 0 to d 2 and a sharp decrease from d 2 to d 6. However, a similar level PLT from d 0 to d 2 observed in scent group (P = 0.0433). Neutrophil to lymphocyte ratio (NLR) decreased from d 0 to d 2 in all treatment groups. While control, V, and VO groups showed similar levels of NLR from d 2 to d 6, O group had increased NLR. This response on NLR is mainly driven by percentage of neutrophil (P = 0.0028) since no statistically significant difference on lymphocyte percentage was found. Results of this study indicated that continuing exposing scent potentially influences complete blood cell of weaning pigs, while the same effect was not found in sow vocal.