EFFET DU RÉGIME LUMINEUX IMPOSÉ DURANT LA GESTATION ET LA LACTATION SUR LES PERFORMANCES REPRODUCTIVES DES TRUIES À LEURS QUATRE PREMIERES PORTÉES

During a 3-yr period, 902 Landrace-Yorkshire gilts were randomly assigned to a 4 h light: 20 h dark (4) or a 16 h light: 8 h dark (16) photoperiod as they entered the reproductive herd at an average age of 225 ± 15 d. The two light regimens were maintained throughout gestation (G) until 1 wk prior to farrowing. For the lactation period (L) the gilts were either maintained on the same light regimen as during gestation or switched to the opposite one before being returned at weaning to the light regimen imposed during gestation. Four light regimens were then formed, namely G4-L4, G4-L16, G16-L4 and G16-L16, and the practical consequences of such light regimens evaluated in a commercial herd. Conception rate at first service, age at first farrowing and litter size in gilts were not influenced by light regimens. At first weaning, more sows in the L16 groups failed to be bred by 32 d postweaning (P < 0.08) while at second and third weanings only a few sows on either light regimen failed to be bred. The proportion of sows bred between days 4–7 postweaning was higher for the G4-L4 and G16-L16 light regimens in first, second and third sows (P < 0.03, 0.02 and 0.06 respectively). Litter size at second farrowing was greater in sows of the G16-L4 regimen than in any other one (P < 0.03) but was similar in all groups at third and fourth farrowings. These data indicate that alternation of light regimens between gestation and lactation increases the weaning-estrus interval while a G16-L4 sequence improves conception rate and litter size of second parity sows. Key words: Swine, photoperiod, productivity, physiological stage, parity