Photoperiodism and pen colouration: effects on the performance characteristics of growing gilts
This study was carried out to investigate the effects of photoperiod and pen colouration on growth performance characteristics of grower gilts. Forty-eight crossbred (Large white x Landrace) grower gilts at 16 weeks of age with mean body weight of 16.82±0.26 kg were randomly allotted to four (4) treatments. Pens were painted with different colours: pantone441 (control), pantone293 (blue), pantone185 (red) and pantone361 (green) and exposed to photoperiods of 12, 15 and 18 hours (h). The experimental design was 4x3 factorial arrangement in a completely randomised design. Performance parameters measured were Feed Intake (FI), Final Weight (FW) and Weight Gain (WG), while Feed Conversion Ratio (FCR) was calculated weekly throughout the 8 weeks of the experiment. Respiratory and rectal temperatures were monitored. The ambient temperature-humidity index (THI) was also monitored. The main effect of pen colour showed significant (p<0.05) variations in FW and WG of gilts with values ranging from 33.68±0.78 kg (red) to 31.00±2.13 kg (green) and 2.10±0.10 kg (red) to 1.77±0.25 kg (green) respectively. Significant reduction was observed in the FCR of gilts in red pens (4.02±0.30) compared to their counterparts in blue (5.05±0.79), green (4.54±0.75) and control (4.13±0.22) pens. However, photoperiod had no significant effects on FW and WG across the treatments. Gilts in 12 h photoperiod had the highest significant (p<0.05) FI and FCR of 9.21±1.68 kg and 4.84±0.83 compared to 7.97±0.19 kg and 4.22±0.52 recorded for gilts exposed to 18h photoperiod respectively. Interactions of pen colour x photoperiods: control pen x 12 h (32.18±0.57), blue pen x 12 h (33.00±1.41), red pens x 12 h (34.25±0.50) and green pens x 12 h (29.00±0.82) was significant for FW. The same trend was also observed for WG, FI and FCR. The THI varied
from 79.5 to 71.5 throughout the period of the experiment. It can therefore be concluded that increasing the photoperiod (hour of day-length) beyond 12 hours may not lead to additional positive impact on the weight changes of gilts but resulted in better feed conversion ratio. However, gilts housed in red pen had better feed utilisation.
Keywords: Photoperiod, pen colour, performance, grower gilts