Effect of a deep uterine insemination on spermatozoal accessibility to theovum in cattle: A competitive insemination study

A competitive insemination study was conducted to determine the effect of a deep uterine insemination on accessory sperm number per embryo in cattle. Cryopreserved semen of a fertile bull characterized by spermatozoa with a s emi-flattened region of the anterior sperm head (marked bull) was matched w ith cryopreserved semen from an unmarked bull having spermatozoa with a con ventional head shape. Using 0.25-mL French straws and a side delivery embry o transfer device, deep uterine insemination (0.125 mt deposited in each ho rn) was performed 2 cm from the uterotubal junction. Immediately after, the uterine body was artificially inseminated using semen (0.25 mt) from an al ternate bull and a conventional insemination device. The complete dose (bot h inseminations) was 50 x 10(6) total sperm cells consisting of an equal nu mber of spermatozoa from each bull. Single ovulating cows (n = 95) were ins eminated at random with either the unmarked semen in the uterine body and m arked semen in the uterine horn, or the unmarked semen in the uterine horn and marked semen in the uterine body. Sixty-one embryos(ova) were recovered nonsurgically 6 d post insemination, of which 40 were fertilized and conta ined accessory spermatozoa. The ratio and total number of accessory spermat ozoa recovered was different among treatments: 62:38 (326) for the unmarked semen in the uterine body and marked semen in the uterine horn, and 72:28 (454) for the unmarked semen in the uterine horn and marked semen in the ut erine body (P<0.05). Deep uterine insemination using this semen in a split dose and a side delivery device favors accessibility of spermatozoa to the ovum compared with conventional uterine body insemination. (C) 1999 by Else vier Science Inc.