engleski

Semen Deposition Site and Seasonal Influence on the Number of Artificial Inseminations until Pregnancy in Simmental Dairy Cows

Semen deposition site and season can significantly influence the number of artificial inseminations until pregnancy (nAI's) in dairy cows. Alltogether 400 cows were randomly divided into the five groups during one year. All animals were of Simmental breed and Body Condition Score (BCS) 2.75 to 3.75 and pluriparae, including 3rd and 4th partus. The aim was to determine influence of the semen deposition site and season on the number of artificial inseminations until pregnancy (nAI's). Toward that goal, the semen was deposited into: Group 1 (n=80): canalis cervicis ; Group 2 (n=80): uterine body ; Group 3 (n=80): uterine horn ipsilateral to the ovary with dominant follicle ; Group 4 (n=80): both uterine horns ; Group 5 (n=80): uterine horn contralateral to the ovary with dominant follicle. Artificial insemination (AI) was performed daily until transrectal confirmation of ovulation, and only cows that ovulated at the end of estrus were included in the research. The same number of cows in each group was inseminated in each quartile of the year in order to eliminate influence of the season on the number of artificial inseminations between observed groups. Frozen semen of only one bull was used also in order to avoid bull influence on the number of inseminations until pregnancy. Results were initially tested using Kolmogorov-Smirnov test to determine distribution of data and finally by using the χ2 test and Two-sided sign test. The outcome measure was the number of artificial inseminations until pregnancy for each group and in each quartile of the year. Because fertility is a binary variable (a cow is either pregnant or not), it was analysed in a categorical mode using a semen site deposition and a quartile as a factors of variation. The highest number of inseminations until pregnancy was observed in the Group 1 with 175 AI's (P<0.05), following by the Group 5 (133 AI's). The lowest number of AI's until pregnancy was noticed in the Groups 3 (117 AI's) and 4 (118 AI's), yet slightly higher in the Group 2 (122 AI's). Differences in the number of artificial inseminations until pregnancy between Groups 2, 3, 4 and 5 were not statistically significant (P>0.05). Differences between Group 1 and the rest of the groups were statistically significant (P<0.05). Our results are proof of the significant sperm transport from the one uterine horn to another since the number of inseminations until pregnancy was also more then satisfactory in the Group 5. Our results are also the proof of a significant retrograde sperm loss after intracervical semen deposition resulting with the highest number of AI's until pregnancy. Season (quartile of the year) has a high and significant influence on the number of AI until pregnancy so the highest number of AI's until pregnancy was observed during the III quartile (summer months) (n=100 ; 190 AI's) and the smallest during the IV quartile (n=100 ; 151 AI's) (P<0.05).

cattle; conception; artificial insemination; semen deposition

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