Effect of feeding level during rearing and mating strategy on performance of Swedish Yorkshire sows 1. Growth, puberty and conception rate

From 74 to 180 days of age, a complete died was offered either ad libitum ( AL) or at proportionately 0.8 of the observed consumption (R) to two groups of purebred Yorkshire gilts, comprising 128 and 127 animals, respectively. Half of the animals in each group was sewed at the first detected oestrus, and the other half at the third detected oestrus, according to a plan defi ned at the start of the experiment. Animals which failed to show oestrus be fore 240 days of age were culled. At 100 kg live weight (LW), AL gifts were younger (-20 days) and had thicke r backfat (+2.3 mm) than R gifts. At the first detected oestrus, AL females were also younger (198 v. 203 days), heavier (127 v. 117 kg LW) and fatter (17.8 v. 14.7 mm backfat thickness) than R gifts. No difference between fe eding treatments during rearing was observed in the percentage of females d etected on hear before day 240. Seventy-three animals were culled from the start of the experiment until service, half of them (54%) failing to show o estrus. At service, LW and backfat thickness in the four treatments ranged from 117 to 148 kg LW and 14.9 to 19.7 mm, respectively The body fatness, e stimated from the ratio of backfat to LW, was higher in AL than in R gilts (0.14 and 0.12, respectively), whereas no difference was observed between E l and E3 gilts (0.13 on average). After the first service 15% of the gifts came back into heat but the conception rate was not affected by feeding tre atment during rearing.