10 Effect of lunar cycle on oocyte quality, rate of cleavage, and in vitro blastocyst production in cows

It was recently shown that the lunar cycle influences the reproductive performance of Brahman cross-bred cows (Aguirre et al. 2021 J. Biol. Rhythms 36, 160–168). This study assessed the influence of the lunar cycle on the yield of viable oocytes (VO), cleaved embryos (CE), and blastocysts (B; seven-day embryos). Good quality cumulus-oocyte complexes (n = 7805) collected from 374 commercial ovum pickup were in vitro maturated, fertilised, and presumptive embryos cultured for six days. The lunar cycle (LC) was split into two phases (crescent: from new moon to full moon, and waning: from full moon to new moon), and four quarters (first: from new moon to first quarter; second: from the first quarter to full moon; third: from full moon to third quarter; fourth: from the third quarter to new moon). Data were analysed by a general linear model and logistic regression of SAS. Number (VO: 18.2 ± 1.2^a vs 13.4^b ± 0.9; CE: 13.9 ± 1.0^a vs 10.1 ± 0.7^b; B: 5.8 ± 0.5^b vs 4.1 ± 0.4^c; ^a–bP < 0.01; ^b–cP < 0.05) and proportions (VO: 72.5^a vs 69.2^b %; CE: 78.3^a vs 76.7^b %; B: 34.3^b vs 31.8^c %; ^a–bP < 0.01; ^b–cP < 0.02) of viable oocytes, cleaved embryos, and blastocysts were statistically greater in waning than in crescent phase of the lunar cycle. Number of VO, CE, and B were statistically different only between the fourth and second quarters of the LC. The difference in proportions of VO, CE, and B according to quarters of the lunar cycle are shown in Table 1. These findings are consistent with a previous study in cows in which better reproductive performance was demonstrated in the waning than in the crescent phase of the LC. In conclusion, the lunar cycle influenced oocyte quality, cleavage rate, and blastocyst yield, with greater numbers in the waning than in the crescent phase.

Table 1. Number and proportion of viable oocytes, cleaved embryos, and blastocysts according to quarters of lunar cycle