THE EFFECT OF ARTIFICIALLY EXTENDED PHOTOPERIOD DURING LACTATION ON MATERNAL PERFORMANCE OF THE SOW 1

Summary A 20-stall farrowing facility was partitioned into two separate rooms of 10 stalls each so that photoperiod could be controlled. In addi- tion, temperature and air movement were equalized in the two rooms. The two light regimens utilized were 8 h light: 16 h dark, and 16 h light:8 h dark. A total of 26 sows in two replicates were used. Females were moved into the facility on d 103 -+2 of pregnancy, litters were equalized at birth and weaning was at 28 d of age. Traits evaluated included litter size at birth and weaning, 21-d pig and litter weights, milk yield on d 15, survival rate and number of days from weaning to estrus for the sow. The number of pigs born alive was similar across treatments. However, after equalization of litter size, differences in the number weaned/ litter were significant (P<.05) as sows exposed to 16 h of light weaned approximately one pig more per litter. The survival rate within each litter from birth (after equalization) to 21 d of age was greater (P<.05) for sows exposed to 16 h light (91.2%) than for those from sows exposed to 8 h light (81.5%). Milk yield at d 15 was measured for 21 of the sows. The sows exposed to 16 h light produced significantly more milk (P<.05) than sows exposed to 8 h light. The time from weaning to first estrus was similar for each treatment group.