Photoperiod and heat stress influence on lactating sow performance and photoperiod effects on nursery XXXX performance.

@entity1707 @entity8291 @entity353
Three experiments were conducted to evaluate sow and piglet productivity under extended photoperiod. In Exp. 1, 98 crossbred, lactating sows were housed in one of four treatments: thermoneutral air temperature (23.6 degrees C) in either (h of light:dark) 1:23 or 16:8 photoperiods, or heat stress (30.4 degrees C) in either 1:23 or 16:8 photoperiods. @entity8291 reduced (P less than .05) sow feed intake, piglet mortality and piglet weaning weight and increased (P less than .01) sow lactation @entity353 . Number of @entity1707 weaned per litter was increased (P less than .01) when sows were heat-stressed. Extended photoperiod reduced (P greater than .05) time for sows to rebreed postweaning by .4 d. The interaction between air temperature and photoperiod was significant only for sow lactation @entity353 . @entity8291 increased sow lactation @entity353 , but this effect was more severe in the 1:23 than in the 16:8 photoperiod. Experiments 2 and 3 examined the effects of 1:23 or 16:8 photoperiods on nursery @entity1707 performance when @entity1707 were weaned from sows experiencing 1:23 (Exp. 3) or 16:8 (Exp. 2) photoperiods. In both nursery studies, photoperiod did not influence (P greater than .10) postweaning @entity1707 mortality, feed intake, weight gain or gain:feed ratio. In conclusion, extended photoperiod reduced days to return to estrus and reduced sow lactation @entity353 , especially during heat stress. No benefits in preweaning or postweaning piglet weight or survival were observed by use of extended photoperiod.
