Seventeen crossbred sows were used in a lactation trial to compare the effects of a 16-h photoperiod with an 8-h photoperiod from d 107 of gestation to weaning at 28 d postpartum. Crossbred sows were used to compare the effects of 16-h (n = 8) and 8-h (n = 9) photoperiods on litter and maternal performance traits. Females were moved into two identical farrowing rooms under either 16- or 8-h photoperiods on d 107 of pregnancy, litters were equalized across treatments at birth and the treatments terminated at weaning on d 28 postpartum. Traits evaluated included litter size at birth and weaning, 21-d pig and litter weights, milk yields and composition on d 15, litter survival rates, suckling frequency for a 24-h period on d 13 and percentage of sows returning to estrus and days to estrus after weaning. Pigs exposed to 16 h light nursed more often (P less than .05) than pigs exposed to 8 h light over a 24-h period. This advantage was greatest during the 4-h periods of 1200 to 2000, 0000 to 0400 and 0800 to 1200 h. This difference is perhaps an explanation of why litters exposed to 16 h light weaned more (P less than .05) pigs/litter with heavier (P less than .01) 21-d litter weights. Nonsignificant advantages were also seen in milk yield and litter survival percentage. In addition, sows exposed to 16 h light had higher (P less than .05) total solids content of their milk.
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Mabry et al. (1983) studied this question.