The TRT sows had lower concentrations of melatonin than the CTL sows on day 4 (P < 0.05), but prolactin concentrations, milk composition and colostrum intake by piglets were unaffected by treatment (P > 0.1). Litter growth during lactation was unaffected (P > 0.1), but TRT piglets consumed less feed between 23 and 34 d of age (P < 0.05) and weighed less on day 35 (P < 0.05). The TRT piglets were more active than CTL piglets on day 3 of lactation only (P < 0.05). Increasing the period of daily light in the farrowing house did not improve the performance of primiparous sows and their piglets.
M.P. Lachance, J.P. Laforest, N. Devillers, A. Laperrière, and C. Farmer. Impact of an extended photoperiod in farrowing houses on the performance and behaviour of sows and their litters.Canadian Journal of Animal Science. 2010. Vol. 90(3): 311-319.