The relations between serum anti-Mullerian hormone (AMH), oocyte numbers, and in vivo embryo production in Holstein heifers were evaluated. The AMH levels of 15 unstimulated cows were followed at weekly intervals during their oestrous cycles and monthly for 4 months. Forty-one superovulated heifers were evaluated at ovum pick-up (OPU) performed 20 h after cystorelin administration, and 125 others were evaluated at embryo recovery. Animals were followed over 3 consecutive cycles induced using a modified Ovsynch protocol with 4 days of FSH (Pluset H, Minitube of America, Verona, WI, USA). Blood samples were collected in serum tubes and spun within 2 h. The samples were stored at –20°C until evaluation using the Minitube of America AMH-bovine specific immunoassay (AMH Fertility Assay™). The statistical analyses (ANOVA and data correlation) were performed using Statview 5 with P < 0.05. Serum AMH ranged from 43 to 960 pg mL–1. The average AMH level of all cows was stable during the oestrous cycle and for each of the 4 monthly measurements. There was a high correlation between all values per animal (r2 = 0.9077; P < 0.01), suggesting that AMH levels are consistent during the cycle and for at least 4 consecutive months. Animals that were repeatedly stimulated showed decreasing AMH levels (509 ± 295, 299 ± 210, 211 ± 119) and a decrease in recovered embryos (7.4 ± 4, 5.6 ± 3.8, 4.2 ± 3.2; P = 0.02). The number of oocytes was not altered by multiple stimulations (10.4 ± 9.8, 11.3 ± 6.2, 8.5 ± 7.6; P = 0.75). As AMH and embryo numbers decreased after multiple stimulations, only the first AMH value and results of the first OPU or flush were used to establish following correlation. Serum AMH showed a positive correlation to the number of oocytes (r2 = 0.245) and embryos collected (r2 = 0.27).When separated into AMH categories, low (<100), normal (100–400), and high (>400 pg mL–1), high-AMH OPU animals yielded significantly higher numbers of oocytes than the animals in the normal or low AMH groups (13.8 ± 9.2 v. 9.2 ± 5.2 and 5.6 ± 3.9; P = 0.001). Flushed animals with high AMH levels had significantly higher numbers of embryos than those with low AMH (10.9 ± 7.9 v. 5.7 ± 5; P = 0.002). Comparison of the first AMH value to the average number of oocytes or embryos collected over the course of 3 collections/animal showed a positive correlation to the average number of oocytes/collection from individual OPU donors (r2 = 0.436) and a positive correlation to the average number of embryos/collection from individual donors (r2 = 0.176). When separated into AMH groups, high-AMH flushed animals had significantly higher numbers of embryos than the normal- or low-AMH animals (9.3 ± 3.1 v. 5.7 ± 3.4 and 4.5 ± 2; P = 0.0001). As OPU animals with low AMH were used only once, average oocyte/collection data was not available for this category. A significant difference was observed between the high- and normal-AMH categories (12 ± 3.6 v. 7 ± 2; P = 0.0001). Circulating AMH is stable over time in unstimulated animals but decreases in repetitively stimulated animals. Anti-Mullerian hormone is highly associated with superovulation response and oocyte and embryo production, and its use should improve animal selection to achieve improve efficiency of multiple-ovulation embryo transfer.
Impact of eutrophication and climate change on Cd and other trace metal dynamic in the Gulf of Riga, Baltic Sea
