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OBJECTIVE: A suboptimal uterine environment contributes to the bovine repeat breeder syndrome. Subclinical endometritis is a component, so the mechanism by which inflammation affects embryo survival was investigated by assessing the effect of non-cellular products of an inflamed endometrium on embryo development to blastocyst. DESIGN: Endometrial fluid from a lactating dairy cow was collected by lavage using embryo culture medium. Aseptic inflammation was then induced by infusion of glycogen and lavage was repeated 6 h later. The recovered fluid was used to culture Day 5 in-vitro-derived embryos for 2 days. Embryo development and quality were compared for two treatment groups (culture media conditioned by inflamed or non-inflamed endometrium) and two controls (control or control + serum). RESULTS: Development to blastocyst was higher for conditioned media or media + serum (inflamed 42.2%; non-inflamed 49.3%; control + serum 50.9%; control 16.9%; P < 0.001). Blastocyst cell numbers were lower for the conditioned-inflamed group (inflamed, 83.1; non-inflamed, 99.8; control + serum, 100.6; control, 110.1; P < 0.001). Trophectoderm cell number, but not inner cell mass number, was reduced in the conditioned-inflamed group and the inner cell mass:trophectoderm ratio was increased (P < 0.001). CONCLUSION: Altering the embryo culture environment with the products of endometrial inflammation had a subtle effect on embryo quality. An increased inner cell mass:trophoblast ratio is likely to negatively affect embryonic survival. Altered embryo quality is a mechanism for early embryonic failure in cows with subclinical endometritis. Culture of embryos with normal endometrial fluid may improve in vitro embryo production.
Hill et al. (2008) studied this question.