Influence of supplemental light on sow performance during and after lactation.

A completely randomized block experiment with two treatments was designed to investigate the effect of supplemental light on sow performance during and after lactation. Crossbred multi- and primiparous sows were exposed to either limited (control, n = 164) or 16 h (n = 163) timer-controlled supplemental light beginning 3 to 9 d before expected farrowing. Overhead illumination (32 to 266 lux) was furnished by seven fixtures (two tubes each) of cool white fluorescent light at twice-daily feedings in control rooms (less than 1 h/d) and for 16 h/d in supplementally lighted rooms (16 h). Litter size was equalized within 48 h postpartum (10 +/- .1 pigs/litter; X +/- SE) in each of five identical rooms that served alternately as control or 16-h treatments during 10 consecutive weekly farrowings (September 24 to November 26, 1981). Litters were heavier (P less than .05) at weaning (26 +/- .1 d) for 16-h than for control sows (57.8 +/- 1 vs 54.3 +/- 1 kg) while pigs weaned (9.2 +/- .1 vs 9.1 +/- .1), piglet survival (90 vs 91%) and days to mating (5.9 +/- .4 vs 5.5 +/- .3) were similar (P greater than .05). However, more (P less than .01) 16-h than control sows (83 vs 68%) were mated by 5 d postweaning. Multiparous sows weaned heavier (P less than .05) litters than primiparous sows (57.9 +/- 1 vs 50.1 +/- 1 kg) while overall litter weight increased (P less than .05) 141 +/- 6 g for each 10 lux increase in light intensity. We concluded that litter weight is increased and return to postweaning estrus more synchronous when sows are exposed to 16 h supplemental ligh/d during a 4-wk lactation.