Ammonia concentration in bovine follicular fluid and its effect during in vitro maturation on subsequent embryo development

Ammonia concentration in bovine follicular fluid (bFF) at different developmental stages and the effects on oocyte maturation in vitro were investigated in this study. In Experiment 1, 80 bFF samples were collected from follicles in four size categories (<1 mm, 2–4 mm, 5–8 mm, and >10 mm) to determine ammonia concentration. Ammonia concentration was greater (P<0.001) in the bFF from smaller follicles compared with bFF from larger follicles, and ammonia concentration decreased (P<0.05) as follicle size increased. Ammonia concentrations in bFF were 366±61 μM, 247±24 μM, 134±21 μM, and 33±10 μM in <1 mm, 2–4 mm, 5–8 mm, and >10 mm follicles, respectively. In Experiment 2, abattoir oocytes (n=2885) were matured in vitro in media containing ammonia at the concentrations of 0 μM (Control), 29 μM (A1), 88 μM (A2), 132 μM (A3), 176 μM (A4) and 356 μM (A5), followed by in vitro fertilization and culture. There was no difference (P>0.05) in cleavage rates and morula or blastocyst development between treatments, indicating that in vitro exposure of bovine oocytes to ammonia does not adversely influence subsequent embryonic development.