Gestational losses in a rabbit line selected for growth rate

Prenatal death can occur due to several genetic and environmental factors which alter normal embryo development, maternal environment to support normal fertilisation, development of embryos, placenta and foetus, or affect the necessary relationship between embryo and endometrium. The aim of this work was to study gestational losses and progesterone, 17 ß-estradiol and IGF I serum levels in a rabbit line selected for growth rate (paternal line). In this study, a maternal line well characterised in previous studies was used as a reference line. A total of 211 laparoscopies were carried out, and the number of corpora lutea and implanted embryos at 12 th days, total born and live born were recorded per female. To analyse the endocrine levels, blood serum was collected from 54 females with implanted embryos at 12 th and 24 th day of gestation (27 from each line). The paternal line showed the lowest ovulation frequency, number of implanted embryos, total born and live born (0.70, 11.3, 7.4, and 6.4 vs 0.86, 12.8, 11.1 and 10.6 for maternal line, respectively) and consequently, the highest implantation, gestational, foetal and perinatal losses (0.31, 0.60, 0.40, and 0.15, respectively). Progesterone serum levels at 12 th days of gestation were similar between lines; however, progesterone serum level at 24 th day of gestation was significantly lower in the paternal line (4.8 vs 8.2 ng/mL). Serum levels of 17ß-estradiol and IGF-I at 12 th days of gestation were different between lines (14.6 vs 26.5 pg/mL, 237 vs 149 ng/mL for paternal and maternal lines respectively). These higher gestational losses of the paternal line could be explained by differences in 17 ß-estradiol level at 12 th days of gestation and the possible effect on low progesterone serum levels at 24 th days of gestation. Further studies in steroid production and bioavailability have to be done during oestrus and pregnancy related with metabolic activity of this line. © 2012 Elsevier Inc.
We are grateful to the Researcher Training Programme from Valencia Polytechnic University. This work was supported by the Spanish Research Project (CICYT AGL2008-03274). The authors thank Neil Macowan Language Services for revising the English version of the manuscript.