Abstract
The objective of the study was to evaluate the effects of using electronically controlled floor cooling pads(ECP) on boar physiology and semen quality during the summer season in a boar stud in Williamston, North Carolina. One hundred twenty boars(313± 130 days of age) were placed in five zones(24 pens 2.29 x 0.66 m) across two tunnel ventilated barns(244 and 148 boars) and randomly assigned to either CONTROL (n=60; partially slatted concrete floor with no ECP) or ECP (n=60) treatments. Cold water was continuously flushed through the individual ECPS at a flow rate of 9.1 L/min. Cold water was circulated when the temperature sensor, placed on the first outlet pipe for each zone, reached 24.5°C and the controller redirected the system to recirculate the water in the pipes when temperature is at 24°C. The boars were exposed to natural heat stress (daily mean temperature and humidity: 25.7°C; 97.99% and hourly mean peak 34.18°C; 100% respectively) in a period of 90 days from July 4 to October 2, 2024. The physiological indicators of heat exposure taken were respiration rate (RR) and rectal temperature (RT) once daily during the hottest part of the day (13:00-17:00h). Semen was collected at least once a week and was analyzed using MetroSperm for concentration, gram scale for volume and subjective analysis by trained technicians for motility and morphology. Detailed morphology was also done by staining samples with Hancock stain and evaluated using 100x oil immersion. Data collected were evaluated using PROC MIXED for repeated measures in SAS (v.9.4) with the main effects of treatment, barn, boar ID, week and their interactions, using classification (old/young) and zone (assigned variables to denote location in barn) as covariates for RR and RT. Same evaluation was done with main effects of treatment, barn, week, and classification, using rest interval and zone as covariates for semen quality estimates. RR and RT were decreased overall by ECP (P< 0.001), week (P< 0.001) and their interaction (P< 0.001). The zone in the barn across different weeks and treatments also influenced the RR (P< 0.001) with CONTROL boars in the zones farthest from the cool cell having higher RR (mean: Barn A-23.34 breaths/min; Barn C-20.65 breaths/min) compared to ECP boars (mean: Barn A-16.25 breaths/min; Barn C-14.34 breaths/min). The increase in RR in these zones (farthest from cool cells) results from increased environmental temperature ranging from 0.88°C to 1.52°C. There were no differences in semen quality estimates between CONTROL and ECP boars (P >0.05) with the exception of improved total motile and normal sperm on weeks 4 and 7 (P< 0.05). Overall, ECP use during the summer months improved the physiological indicators of heat exposure while having slight improvements on semen quality towards the later part.