Insemination of four cows per dose of frozen semen with a fixed-time artificial insemination protocol
Silveira, E CBortolloti, L AMorotti, FSilva-Santos, K CSantos, G M GAndrade, E RSeneda, M M
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 1:4) 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.(AU)
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