Abstract

Successful pregnancy in dairy cows requires accurate timing of artificial insemination (AI). Artificial insemination conducted in the morning, midday, and afternoon exposes cows to different environmental temperatures with high ambient temperatures can potentially reduce the viability of spermatozoa, thus disrupting the fertilization process and increasing the possibility risk of pregnancy failure. The purpose of the present study was to ascertain and determine how the effect of various AI timings (during the morning, midday, and afternoon) affected the pregnancy success of the pregnancies in Holstein-Friesian cows. The purposive sampling was used to select a total of 191 Holstein-Friesian cows based on the following specific criteria; cows showing symptoms of estrus, having healthy reproductive organs, having one parturition at least once, aged 2-6 years old, having body condition score of 2.5-3.5 (on a 1-5 scale). The cows were divided into 3 three treatment groups including T1 cows inseminated from 06.00 am to 10.59 am (n=38 cows), T2 cows inseminated from 11.00 am to 03.59 pm (n=82), and T3 cows inseminated from 04.00 pm to 08.59 pm (n=71). The non-return rate was monitored at 19-22 days post-insemination (NRR-1) and 39-42 days post-insemination (NRR-2) was monitored, while the conception rate (CR) was assessed on day 60 post-insemination. Artificial insemination was performed 8 hours after estrus. NRR-1 values for T1, T2, and T3 were 82%, 80%, and 89%, respectively, The NRR-2 values were 71% in T1, 66% in T2, and 79% in T3. The CR for T1, T2, and T3 were 50%, 48%, and 54%, respectively. Although AI timing did not yield conception rates based on AI timing did not show a significant difference in conception rates, artificial insemination performed in the morning insemination is recommended due to its higher likelihood of successful pregnancy compared to other times.