Effect of chlortetracycline supplementation during prebreeding and early gestation on age at puberty, ovulation rate, embryo survival and fetal development in gilts

A total of 166 crossbred gilts weighing approximately 87 ± 1 kg was limit-fed (2.5 kg/d) a corn-soybean meal gestation diet containing either 0 or 220 ppm of chlortetracycline (CTC) from 157 ± 1 d of age until 15 d after breeding. These gilts were slaughtered at 31 ± 1 or 71 d ± 1 d of gestation for evaluation of reproductive performance. Age (190 ± 3 d vs 195 ± 3 d) and body weights (106 ± 2 kg vs 106 ± 2 kg) at puberty were similar for control and CTC-fed gilts, respectively. Although not significant (P > 0.05), ovulation rate was higher in CTC-fed than in control gilts as assessed at both 31 d (14.2 ± 0.7 vs 12.9 ± 0.9, P = 0.31) and 71 d (13.9 ± 0.6 vs 12.4 ± 0.5, P = 0.10) of gestation. There was an increase (P = 0.04) in the number of live embryos for CTC-fed gilts at 31 d (12.1 ± 0.7 vs 9.7 ± 0.7) but not at 71 d (10.0 ± 1.1 vs 9.6 ± 1.0) of gestation. The mean uterine length, placental length, placental weight, fetal length, fetal weight, and allantoic fluid volumes were similar between the control and CTC-fed gilts. Results indicated that feeding CTC during prebreeding and early gestation did not influence the proportion or age of gilts at puberty. However, CTC feeding may have influenced a trend to-ward an increased ovulation rate and increased number of live embryos in gilts.