Insemination of four cows per dose of frozen semen with a fixed-time artificial insemination protocol

ABSTRACT

The aim of the study was to evaluate the practicality of a 1 4 dilution of doses of semen in fixed - time artificial insemination ( FTAI ) programs. Nelore cows (n = 803 ) were synchronized by a conventional FTAI protocol. For AI in the dilut ed group (n = 392) , 0.5 ml semen straws were thawed and 0.5 ml of extender conta ining amino acids and methylxanthine derivatives was added. The straws were fractionated into four straws of 0.25 ml each (dilution 14) with approximately 2.5 x 10 6 spermatozoa each and the insemination was performed in the ipsilateral horn to the ovary c ontaining the dominant follicle . In the control group (n = 411), AI was performed in the uterine body with one straw of 0.5 ml (10 x 10 6 spermatozoa) containing seme n from the same bull and batch . The conception rate was 49.2% (193/392) for the diluted gro up and 50.1% (206/411) for the control group, with 1.97 and 0.50 pregnancies per dose of semen , respectively . T he dilution of semen provide d a pregnancy index similar to the control group ; however, the technique increased the number of pregnancies per dos e , allowing for the best use of semen of high genetic value and reducing the cost per pregnancy.