MARINE MICROALGAE EFFECTS ON ENDOMETRIAL EXPRESSION OF KEY MOLECULES IN PREGNANT DAIRY COWS

Abstract

Feeding fish meal, high in omega-3 long chain polyunsaturated fatty acids (PUFA) has been shown to inhibit uterine secretion of series 2 prostaglandins and improve pregnancy rates. The objectives of the current study were to evaluate the effects of two sources of long chain omega-3 PUFA supplements, fish oil and marine microalgae, on the expression of key receptors and the prostaglandin H synthase-2 enzyme in bovine endometrium at the time of pregnancy recognition. Within a week of calving, lactating Holstein cows (n=12) were assigned to one of three supplements: hydrogenated plant oil (control), rumen-protected fish oil (PFO) or rumen-protected marine microalgae (PMA) high in docosahexanoic acid (DHA; C22:6, n-3). Diets were isolipidic and isonitrogenous, and were fed for four months. Circulating omega-3 PUFA concentrations were 5.96, 6.80, and 7.53% of total plasma fatty acids in control, PFO- and PMA-supplemented cows, respectively, after four months of supplementation. The PMA-supplemented cows had higher plasma DHA levels (0.72% ± 0.03, P<0.01) than PFO-supplemented cows (0.33% ± 0.02, P<0.01), which had higher levels than control animals (0.082% ± 0.005, P<0.01). Upon confirmation of pregnancy at day 17, uterine tissues were collected for analysis of relative expression and localization of progesterone receptor (PR), estrogen receptor-alpha (ERalpha), oxytocin receptor (OTR), peroxisome proliferator-activated receptor-delta (PPARdelta) and the enzyme prostaglandin H synthase-2 (PGHS-2). Cows fed either PFO or PMA showed stronger reactivity with PR antibodies in the deep glandular epithelium than those supplemented with the control (P≥0.05). Treatment differences in PR expression in other endometrial compartments were not significant, and western blotting failed to detect differences in overall PR expression (P>0.10). There was a tendency for stronger ERalpha antibody reactivity in the adluminal stroma in cows fed PMA (P<0.10), although western blotting of whole endometrial extracts indicated a trend for reduced ERalpha expression in PMA- versus PFOsupplemented animals (P<0.10). Immunohistochemistry did not indicate treatment effects on OTR, PPARdelta or PGHS-2 localization (P>0.10). However, relative protein levels of PGHS-2 were higher in cows supplemented with PFO or PMA in comparison to the control (P≥0.05), and PPARdelta expression was higher in PFO- than control- supplemented cows (P≥0.05). The results confirm the importance of source of omega-3 long chain PUFA in supplements for dairy cows. Marine microalgae are an alternative source of omega-3 PUFA that affect reproduction through different pathways than those of traditional fish-based supplements. (poster)