RELATIONS ENTRE LES VARIATIONS PONDÉRALES DE LA TRUIE EN REPRODUCTION ET LES PERFORMANCES D'ÉLEVAGE

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Abstract
This investigation dealt with 459 litters farrowed by 186 Large White sows bred in the Station de Recherches sur l''Elevage des Porcs between 1954 and 1961. The sows were weighed at the time of mating, before and after farrowing and at the time of weaning (60 days). The litters were weighed at birth and when 21 and 60 days old. On the whole, 16 variables concerning either weight variations in sows or litter characteristics were studied. The means corresponding to the 1st 5 farrowings were compared by means of Duncan''s multiple range test. The weights of the sows increase during pregnancy (45-57 kg) and decrease during lactation (20-35 kg) so that the weight change during each reproductive cycle is positive. Litter size and weight at birth and at the time of weaning increase up to the 4th farrowing, whereas piglet mortality reaches a maximum at the 5th and subsequent litters. The duration of pregnancy is not related to the serial number of the litter. The linear correlation coefficients between the 16 variables were calculated within each year of birth and within the same serial number of litters. There is scarcely any relation between litter size and weight at birth and weight gain of the sow during pregnancy. Weight gain during pregnancy and loss during lactation are correlated (r = 0.27); weight loss during lactation is correlated with litter weight at 21 and 60 days (r = 0.40). It appears that any increase in the gain during pregnancy does not considerably improve litter characteristics (correlation gestation gain to weight of the litter at the time of weaning: r = 0.11).