A dietary supplement of calcium soaps of fatty acids enhances luteal function in sheep

The effect of a dietary supplement of calcium soaps of fatty acids on lutea l steroidogenic activity was studied in sheep. Mature 3- to 5-year-old Nort h Country Cheviot ewes were given either a pelleted control diet (C; grass, beet pulp, barley; no. = 15) providing daily, 29.8 g nitrogen and 13.7 MJ of metabolizable energy (ME) or the same diet with 5% (w/w) of the ingredie nts replaced with protected lipid (C + CaFA; calcium soaps of fatty acids, Megalac, Volac Ltd; no. = 15) for 21 days. The latter diet provided daily 3 0.2 g nitrogen and 15.9 MJ ME. At the end of the feeding period the ewes we re slaughtered and blood samples and ovaries were collected from individual animals. The numbers of large- (greater than or equal to 4 mm diameter) an d small- to medium-sized (1 to 3 mm diameter) follicles were recorded and f ollicular fluids from both size groups were stored for later analyses follo wing centrifugation. Each mature corpus luteum (CL) was isolated from its o vary and sliced to provide a pair of ca. 0.3 mm diameter sections. These se ctions (mean = 163 (s.e.12) mg) were cultured separately (4 h; 39 degrees C ; 5% CO2) in 3 ml Medium 199 in the absence or presence of 100 mu IU LH. Di etary supplementation of calcium soaps of fatty acids increased progesteron e concentrations in the plasma (P < 0.05) and follicular fluid (P < 0.01 an d P < 0.05 for large and small to medium follicles, respectively); trigylce rides in plasma (P < 0.05); fetal cholesterol in plasma (P < 0.002) and fol licular fluid (P < 0.001); HDL-cholesterol in plasma (P < 0.001) and follic ular fluid (P < 0.01) and LDL-cholesterol in plasma (P < 0.01). Progesteron e released by luteal tissue into the culture medium in vitro from ewes give n protected lipid was higher than that from tissue of control ewes (P < 0.0 5) and supplementary LH in vitro stimulated progesterone secretion by lutea l tissues from both groups (P < 0.05). In conclusion, a dietary supplement of calcium soaps of fatty acids altered the intra-follicular environment su rrounding the oocyte and follicular cells and enhanced luteal function in s heep.