Relationships between blood and follicular fluid urea nitrogen concentrations and between blood urea nitrogen and embryo survival in mares

High blood urea nitrogen (BUN) concentration is linked to low fertility in cows and ewes; however, this relationship has not been reported mares. The study characterized the between BUN follicular fluid (FUN) during follicle growth (Experiment 1) impact of from embryo donors on pregnancy outcome recipient mares 2). In experiment one, samples were collected diestrus with growing follicles estrus pre-ovulatory (n = 16 10 mares, respectively). two, concentrations related after transfer. there was a strong positive correlation FUN (R 0.83; P < 0.0001), higher than preovulatory (P 0.004) 0.031). donor that produced unsuccessful embryos compared resulting successful pregnancies at D14 0.03). Additionally, an effect age 0.01) interaction lactation 0.009) for survival Donor older embryos. Therefore, these experiments showed environment as well Day 7–8 transfer