Effect of altering dose of PG600 on reproductive performance responses in prepubertal gilts and weaned sows

This study evaluated the effects of altering dose of PG600 on estrus and ovulation responses in prepubertal gilts and weaned sows. Experiment 1 tested the effects of one (1.0x, 400IU eCG+200IU hCG, n=74), one and a half (1.5x, n=82), or two (2.0x, n=71) doses of PG600 for prepubertal gilts. Estrus (58%) and ovulation (90%) were not affected (P>0.10) by dose. Higher doses increased (P<0.01) numbers of corpora lutea (17, 24, and 25), but not (P>0.10) the proportion of gilts with cysts (26, 36, and 46% for 1.0x, 1.5x, and 2.0x, respectively). Experiment 2 tested the effects of 0x (n=30), 0.5x (n=32), 1.0x (n=29), or 1.5x (n=30) doses of PG600 in weaned sows. Dose did not influence return to estrus (90%, P>0.10). There was an effect of dose (P<0.05) on incidence of cysts (3.4, 1.8, 6.4, and 29.8%, for 0x, 0.5x, 1.0x, and 1.5x doses, respectively). The 0.5x dose increased (P<0.01) farrowing rate (83.2%) compared to 0x (72.1%) and 1.5x (58.6%), but was not different from 1.0x (76.4%). Total pigs born (10.5+/-0.8) did not differ (P>0.10) among treatments. These data suggest that increasing dose of PG600 to 1.5x for gilts increases the number of corpora lutea but does not alter the proportion expressing estrus or ovulating. Reducing dose of PG600 for weaned sows did not alter estrus or ovulation, but the 0.5x dose increased farrowing rate compared to no PG600.