EFFECT OF LIGHT ON THE DEVELOPMENT OF MARKET PIGS AND BREEDING GILTS

A total of 176 Yorkshire pigs (112 barrows and 64 gilts) were raised from weaning to market weight, second estrus or parturition, in a piggery maintained under normal daylight conditions or in darkness. Average daily gain and feed required for gain were not affected by the treatments. There was no significant difference in total backfat or loin eye area between barrows housed in darkness and barrows housed in normal daylight conditions. Gilts raised in darkness reached puberty 11 days earlier than gilts raised in daylight (P < 0.01). Ovulation rate and litter size at birth were not affected by the treatments. Optical enucleation delayed the onset of estrus by 14 days, but had no other detectable effects.