88 CHANGING MATERNAL NUTRITION IN EARLY PREGNANCY MODIFIES FETAL OVARY DEVELOPMENT IN NELLORE COWS

Abstract

Environmental influences such as nutritional restriction during early gestation in cattle may impair fetal development and compromise functions in adulthood. During the first trimester of gestation fetal gonads are formed. We hypothesised that either restriction or excess of nutrients ingested by cows during the first third of pregnancy interferes with fetal body weight (BW) and ovary development. Twenty-one uniparous Nelore cows (BW = 488 ± 24 kg, body condition score, BCS = 3.1 ± 0.1) were subjected to timed AI with sexed semen (female) of a single bull and individually allocated to different diets. The diet of the control group (C) met the maintenance requirements, and the groups of high (A) and low (B) were either 180% or 60% of maintenance respectively. Live weight and BCS were assessed weekly to adjust the diet according to the individual weight of each animal. At 60 days of gestation, 9 fetuses (3/group) were removed by colpotomy (accessed through vagina), weighed, and their ovaries were dissected and weighed. One fetal ovary (of each pair) was analysed by RNA-seq (mRNA). The effects of treatments on both ovarian and fetal weight were compared by ANOVA (proc GLM, SAS 9.3, SAS Institute Inc., Cary, NC, USA). During the 60 days of treatment, cows from Group A gained 66 kg (from 474 ± 6 kg to 541 ± 10 kg) and 1.25 points in BCS (from 3.0 to 4.25), whereas the cows in group B lost 61 kg (from 458 ± 3 kg to 397 ± 6 kg) and 1 point in BCS (from 3.2 to 2.2). Fetal ovary weight (sum of the two) was lower in group B (0.007 ± 0.001 g; P < 0.04) than in groups A (0.02 ± 0.004 g) and C (0.013 ± 0.007 g), which did not differ (P > 0.08) between each other. Fetuses in group B weighed less (12.8 ± 1.14 g; P < 0.006) than in groups A (20.56 ± 2.2 g) and C (20.03 ± 0.8 g). Maternal nutritional status during the first 60 days of gestation changed the transcriptome of fetal ovaries. There were differences in the pattern of gene expression between the control, high, and low intake groups. A total of 79 genes out of 20 657 showed differential expression between treatments (false discovery rate 0.05), some of which were related to embryonic and ovarian development. Thus, we conclude that changing maternal nutrition during the first 60 days of gestation will change the transcriptomic profile of fetal ovaries. Poor maternal nutrition jeopardizes ovarian size and weight and fetal weight, suggesting impairment on the production of ovarian follicles. This is a critical period in fetal ovarian development, as oocytes grow and differentiate, and need to escape from degenerative processes to remain in the ovaries. Thus, the developmental impairment at the beginning of meiosis could reduce the number of oocytes in the fetal ovary. Histological examination of fetal ovaries is underway to evaluate the number of oocytes.

Funding provided by FAPESP 2011/50839-1; CNPq 487036/2013-3, CAPES.