Comparison of corpus luteum function and embryo quality in heifers and second/third parity lactating cows
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The aim of this study was to compare embryo quality, uterine environment and corpus luteum function in heifers and second/third parity cows. After superovulation and embryo recovery at day seven, 78 embryos (n = 17 from cows and n = 61 from heifers) were scored morphologically for quality and developmental stage. Significant differences were observed in fertilization rate (p =0,01) and transferability (p < 0,01) between heifers and cows. Blood was collected on 11 different days in the cycle for progesterone (P4) analysis from every heifer (n = 6) and cow (n = 7) that was involved in this experiment. Day 0 is the start of the Ovsynch protocol. The plasma P4 levels on days 13, 15, 17, 19, 26, 28 and 30/31 were significantly higher (p < 0,05) in heifers than in cows. There was a tendency for this difference on day 11 (0,05 < p <0,10). There were no significant differences in plasma P4 on day 9, day 21 and day 24.