W produkcyjności loch nie stwierdzono statystycznie istotnych różnic pomiędzy grupą doświadczalną a kontrolną oraz między miotami (m_0) urodzonymi w czasie doświetla-nia w grupach doświadczalnych a następnymi miotami (m_1) urodzonymi w czasie eksperymentalnego programu świetlnego. Zaobserwowano tendencję do skracania okresu od odsądzenia miotu do zapłodnienia u loch w warunkach skróconego dnia świetlnego.%Two experiments were carried out on sows kept in artificial (group D) and natural light (group K). In the first experiment, the size of groups was 21 sows (5, 6 and 10 in replications, respectively), and in the second experiment it was 6 sows in the period from about 105 days of gestation until fertilization. In group D of experiment Ⅰ, in the spring-summer season the lighting time was gradually decreased from 16h to 8h, and in experiment Ⅱ in the autumn season it was increased from 11h 24' to 16h24'. Light intensity in group D was 9 lx, and in group K in experiment Ⅰ it was from 23 to 183 lx and in experiment Ⅱ from 32 to 41 lx. No statistically significant differences in sow productivity were found between groups D and K, and between litters (m_0) born during extra lighting in groups D and litters (m_1) born from fertilization during the experimental lighting programme. The period from litter weaning to sow fertilization was found to become shorter as the light day shortened.
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