EFFECT OF LIGHT REGIMEN UNDER VARIOUS AMBIENT-TEMPERATURES ON SOW ANDLITTER PERFORMANCE

Primiparous Large White females were exposed to one of two light regim ens characterized by an increase (from 12 to 16 h/d, LONG treatment) o r a decrease (from 12 to 8 h/d, SHORT treatment) in photoperiod during gestation. Two successive replicates were conducted, and farrowings o ccurred in January and July. During the last month of gestation, durin g lactation and after weaning, ambient temperatures varied between 18 and 25 degrees C and between 25 and 38 degrees C for the first and sec ond replicates, respectively. Weaning occurred at 3 wk postpartum. Per centage of sows in estrus within 10 d after weaning was higher (P < .0 5) in the SHORT than in the LONG group for both replicates and when fa rrowing occurred in January compared with July for both photoperiod gr oups (SHORT-January: 92%, LONG-January: 53%, SHORT-July: 32%, LONG-Jul y: 14%). Loss of live weight in sows during lactation was higher in Ju ly than in January and higher in the SHORT than in the LONG photoperio d (P < .05). Live weight of pigs at birth was higher in July than in J anuary, whereas growth rate of pigs until weaning was higher in Januar y (P < .05). Temperature may have a greater influence on sow and litte r performance than photoperiod.