Thyroid stimulating hormone enhancement of bovine oocyte maturation in vitro

Efforts to improve bovine embryonic development in vitro involved study of effects of thyroid stimulating hormone (TSH) alone or in combination with LH on bovine oocyte maturation (IVM). Putative effects were assessed by observing cumulus expansion (CE), fertilization (IVF), and development to morulae/blastocysts (M/B). Effects of prolactin (PRL) were also investigated. Variables for the 24‐hr IVM interval were no hormone (control), TSH (0.1, 0.5, or 1.0 μg/ml) or PRL (10, 100, or 1000 μg/ml), luteinizing hormone (LH) (0, 10, or 100 μg/ml) + TSH (0.1 or 0.5 μg/ml), and serum (20%, v/v) + 0.5 μg TSH/ml; data were from 4–5 trials for each IVM treatment. Higher proportions of oocytes exhibited complete CE with hormones or serum than without (P < 0.05). All oocytes (with and without CE) were inseminated with heparin‐capacitated sperm. A higher proportion of inseminated oocytes cleaved after IVM with 0.5 μg TSH/ml (53.4%) than for other TSH treatments (P < 0.05). The combination of TSH (0.1 and 0.5 μg/ml) with 10 μgLH/ml for IVM enabled higher proportions (P < 0.05) of ova to fertilize (67.4 and 69.2%) than did medium alone (28.3%), LH (10 μg/ml) alone (54.1%), or serum + 0.5 μg TSH/ml (55.6%). No improvement in proportions undergoing fertilization was seen after addition of TSH to 100 μgLH/ml for IVM. Frequency of CE and cleavage did not differ among PRL treatments. More M/B developed from cleaved ova after IVM with LH or TSH than with PRL or no hormone (P < 0.05). Data document the beneficial influences of TSH and LH during IVM on the quality of the resulting ova.