The maternal blood transcriptome reflects changes in foetal growth and is an accurate predictor of birth weight in cattle

Harnessing maternal blood to predict fetal growth is an emerging area in livestock research, offering a non-invasive approach to monitor fetal development and potentially enhance reproductive management in cattle. In this study, blood samples were collected from 20 recipient cows carrying female fetuses produced via in vitro embryo transfer at 63 days of gestation. At birth, calf weights ranged from 30 to 72.5 kg, with an average of 45 kg. RNA-seq analysis of maternal blood revealed transcriptomic patterns associated with calf birth weight. Furthermore, a transcriptomic signature was identified that enables accurate prediction of calf birth weight with low error. Overall design: Maternal blood samples (n=20) were collected via tail venipuncture using a 21-guage vacutainer needle in Tempus Tubes (Thermofisher Scientific, Waltham, MA USA) from recipients confirmed to be pregnant on day 63 of gestation with a female beef breed foetus, derived from X-sorted semen. Blood samples were kept at -20°C for 24 hours and then moved to -80°C for storage until processing for RNAseq. Birth weight was recorded at parturition for the ensuing calves.