Effect of long-acting injectable progesterone supplementation, seven days after insemination, on embryo and fetal development in Nellore cows

Abstract

This study evaluated the effects of long-acting injectable progesterone supplementation (P4LA) on embryonic and fetal development and birth weight in Nellore cows seven days after timed artificial insemination (TAI). One hundred and nineteen Nellore female cows became pregnant after the TAI protocol and were divided into two groups: P4LA with cows that received 150mg of P4LA, seven days after insemination, in a single dose, and the control group, with cows who did not receive any hormonal supplementation after TAI. Blood samples were collected on days 17 and 30 after TAI to determine P4 concentration. Embryonic and fetal measurements were performed at 30 and 45 days of gestation, respectively, with the aid of ultrasonography, measuring craniocaudal length and thoracic diameter. No difference was observed in P4 concentration between the groups supplemented with or without injectable P4 on days 17 (P=0.73) and 30 (P=0.62) after TAI. There was no significant difference in embryonic and fetal development or birth weight between the supplemented and non-supplemented groups (P=0.59, P=0.09, and P=0.64, respectively). Supplementation with injectable progesterone seven days after TAI did not interfere with the embryonic and fetal development of Nellore cows, nor did it affect birth weight.