70 (6) 475-480

S. Verberckmoes, I. De Pauw, A. Van Soom, G. Vanroose, H. Laevens, A. de Kruif

In this study, the effect of the insemination dose (250 or 500 x 106 fresh spermatozoa) on pregnancy rate at 35 days post-insemination (PI) in synchronized ewes was analyzed. The 30 days non-return rate was determined by the introduction of an intact ram harnessed with a crayon at 10 days PI. At 35 ± 2 days PI, the ewes were scanned for pregnancy by means of transrectal ultrasonography (7 MHz). Five months PI, the lambing rate and fecundity were recorded. No significant differences (p<0.05) were found in non-return rate, pregnancy or fecundity between 250 and 500 x 106 fresh spermatozoa per insemination dose. Increasing the number of spermatozoa from 250 x 106 to 500 x 106 per insemination dose did however improve the lambing rate (p<0.1). Pregnancy control by transrectal ultrasound (7 MHz) at 35 ± 2 days was at least as reliable as a teaser ram.

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