The effect of ovulatory follicle size at the time of insemination onpregnancy rate in lactating dairy cows

Abstract

The aims of this study were to determine the factors that affect follicle size at the time of artificial insemination (AI) and to detect the relationship between ovulatory follicle size at the time of AI and pregnancy rate in dairy cows. A total of 1428 follicle size measurements were obtained from Holstein-Friesian (HF) and Swedish Red (SR) cows that were inseminated with the fixed-timed AI protocols used in this study. Follicle size was affected by breed (P = 0.0001), milk production (P = 0.01), parity (P = 0.05), and season (P = 0.04). Follicle size was greater (P = 0.0001) in the HF (15.55 mm) than the SR cows (14.88 mm). Multiparous cows had larger (P = 0.04) follicles (15.35 mm) than the primiparous cows (15.07 mm). Cows with follicle sizes between 13.5 and 17.5 mm were more likely to be pregnant than cows with other sizes follicles (P < 0.01). Embryonic loss was lower (P < 0.01) in cows with follicle sizes between 13.5 and 16.5 mm. Thus, the follicle size was affected by breed, milk production, parity, and season. Pregnancy and embryonic loss in lactating dairy cows were significantly related to follicle size.

Effect of Some Factors on Number of Services per Conception in Dairy Cows

“…Also other authors [19][20][21] concluded that high ambient temperatures (heat stress) may adversely affect fertilization and embryo survival. Exposure to high temperatures may degenerate ovarian theca and granulosa cells, reduce steroidogenesis, and also compromise ovarian progesterone production [19].…”

Consequences of Transition Treatments on Fertility and Associated Metabolic Status for Dairy Cows in Early Lactation

“…Energy balance was positively correlated with the number of large follicles in ovary, and negatively correlated with the numbers of small and medium follicles [54]. However, cows with medium-sized follicles (between 14.5 and 17.5 mm) had a greater pregnancy rate than cows with follicles of other sizes [55].…”

Effects of injecting increased doses of vitamins C and E on reproductive parameters of Holstein dairy cattle

“…A relationship between size of preovulatory follicle and probability of a cow diagnosed as pregnant after a fixed-time AI has been reported in dairy cattle (19) . Cows with preovulatory follicles between 13.5 to 17.5 mm are more likely to become pregnant after a fixed-time AI (20) . A possible explanation for the effect of preovulatory follicle size on pregnancy rate could rely on the degree of oocyte competence.…”

“…The cows injected with vitamins C and E had preovulatory follicles falling under the threshold at which the probability of pregnancy after AI increases (20) . Since cows injected with the highest dose of vitamins tend to have a small preovulatory follicles, a similar tendency was expected in estradiol concentrations.…”