POSTMATING FEEDING LEVEL EFFECTS ON CONCEPTION RATE AND EMBRYONIC SURVIVAL IN GILTS

One hundred and twenty-eight gilts were used to evaluate the effect of reducing the level of feeding at estrus on conception rate and embryonic survival. Within each of 4 yr, 16 Yorkshire and 16 Lacombe gilts were penned individually in a piggery, fed 2 kg of diet once daily and 11 days after being observed in estrus were fed 2.5 kg of diet (H). The gilts were mated on the first (day 0) and second day of estrus with two boars of the other breed. On day 1 feed intake was reduced to 1.5 kg (L) per day for one-half of the gilts of each breed. On day 11 the feeding level was switched for one-half of the gilts in each of the two groups to give four feeding level treatments of HH, HL, LH and LL. All gilts were slaughtered between days 30 and 35. The breeds did not differ in average daily gain (ADG), conception rate, or embryonic survival. The Yorkshire gilts had fewer (P < 0.01) corpora lutea (12.0 vs. 13.1) and fetuses (9.3 vs. 11.1) than the Lacombe gilts. The HH and LH gilts had higher ADG than HL and LL gilts (P < 0.01). The HH, HL and LH gilts had higher (P < 0.01) conception rates than the LL gilts (87.1, 86.2 and 87.1% vs. 64.3%, respectively). The numbers of corpora lutea and fetuses were not significantly different among treatments. However, when the H and L treatments to day 10 were compared, the L gilts had more fetuses (11.0 vs. 9.5) and a higher embryonic survival (86.2 vs. 75.8%) than the H gilts (P < 0.05). A body weight maintenance feeding level for 10 days after mating appeared to improve embryonic survival. Key words: Gilts, feed restriction, conception rate, embryonic survival