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Effect of low-sperm number combined with fixed-time deep cornual insemination on pregnancy rate in progesterone-treated beef cows

Abstract:

The aim of the study was to evaluate effect of single and double fixed-time artificial insemination into the uterine horn ipsilateral to the ovary bearing the dominant follicle (DF), combined with low dose spermatozoa in beef cows upon the pregnancy rate (PR). A total of 177 suckled cows (Hereford and Braford, multiparous, postpartum range: 35-94 days) from two farms were used. The cows were treated with a progesterone intravaginal device during 8 days and were fixed-time artificially inseminated (FTAI). Ultrasonography was used to identify the DF (presumptive ovulatory follicle) 24 h after device removal. The semen of two bulls was used. One ejaculate from each bull was split into two spermatozoa concentrations: 5 (LD: low dose) and 25 (SD: standard dose) million spermatozoa per dose (0.5 ml straws). The straws were then frozen in a programmable freezing machine. The animals were assigned to four treatments (T); T1 (control) (n=47): FTAI into the uterine body with SD, T2 (n=45): FTAI into the uterine body with LD, T3 (n=43): FTAI into the uterine horn ipsilateral to the ovary bearing the DF with LD and T4 (n=42): two FTAI into the uterine horn ipsilateral to the ovary bearing the DF with LD. Cows were inseminated 54-56 h after device removal. The second FTAI of T4 was performed 72 h after device removal. Pregnancy was diagnosed by ultrasound at 35 days after FTAI. Pregnancy rate was higher (P<0.05) for the T3 (58.1%) than T1 (38.3%) and T2 (28.9%), but it was not higher (P>0.05) than T4 (42.9%). Nevertheless, the PR did not differ (P>0.05) among T1, T2 and T4. It is concluded that a single FTAI into the uterine horn ipsilateral to the ovary bearing the DF combined to LD spermatozoa in suckling cows is more efficient than a FTAI into uterine body with LD or SD and it is equally efficient than double FTAI into the uterine horn ipsilateral to the ovary bearing the DF with LD sperm.