Abstract
Effects of amount of anechoic intrauterine fluid (IUF) and size of largest follicle at insemination on proportion of cows pregnant as a result of AI (P/AI percentage), as well as factors associated with amount of IUF and size of the follicle were investigated. Follicle size was determined, and amount of IUF in the largest uterine segment was categorized as containing no fluid, <= 10, >10-20, and >20 mm using the ultrasonic monitor grid in 735 cows at time of insemination. Multivariable regression models were constructed to evaluate effects of different variables on P/AI percentage, and variables associated with the IUF score and follicle size. On day 30 postinsemination, the P/AI percentage was greater in cows that had >10 to 20 mm IUF than cows with no IUF (OR = 1.9, P = 0.01), but on day 70 post-insemination, the P/AI percentage was similar in cows with different amounts of IUF. Follicle size was not associated with P/AI percentage on days 30 and 70 post-insemination. Cows in spontaneous estrus, multiparous cows, cows with a cystic structure and a typically functional follicle, and Holstein cows had a greater likelihood for a larger IUF value. Primiparous cows, cows on which there was imposing of a hormonal-ovulation-synchronization regimen, and crossbred cows were more likely to have smaller follicles. In conclusion, amount of IUF at the time of insemination and size of the follicle were not associated with P/AI percentage, and several variables were associated with amount of IUF or follicle size.