Flushing on L I T T E R Size in Gilts 735

A TOTAL of 146 gilts were randomly assigned at estrus to one of the following flushing treatments: (1) control--2.27 kg of feed daily; (2) 1-day flush--2.27 kg of feed daily, except for a 24-hr. period of ad libitum feed intake during mating estrus; and (3) 14-day flush--2.27 kg of feed daily except for a 2-week period of ad l ibitum feed intake starting on day 7 of the estrous cycle. Average ovulation rate in the 14-day flush group (15.7 ova) was significantly (P~.01) greater than that of gilts flushed for 1 day (14.2 ova) or in controls (13.8 ova). Gilts flushed for 1 day ovulated an average of 0.4 ova more per gilt than controls, but this difference was not significant (P<~.05). Season did not significantly affect ovulation rate (spring, 14.5 vs. summer, 14.6). The left ovary ovulated more ova (P ( .10 ) than the right (7.5 vs. 7.0). Gilts fushed for 14 days had significantly (P ( .01 ) more live embryos per litter (13.0) than the 1-day flush group (11.3) or control gilts (10.9). Gilts mated in the spring had significantly (P( .01) more live embryos per litter (12.4) than summer-mated gilts (11.0). Embryo survival (live embryo/corpora lutea) was not affected by treatment, but was higher in spring-mated gilts (85.3%) than in summer-mated gilts (75.7%). Slightly more live embryos were found in the right uterine horn than in the left (6.0 vs. 5.7) but this difference was not significant. Embryo size was not significantly affected by treatment or season. Average crown-rump length and weight of the embryos at 28 days gestation were 24.0 mm and 1.38 g, respectively.