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Does timing of AI affect P/AI in seasonal-calving, pasture-based lactating dairy cows inseminated with sex-sorted sperm?

S.T. Butler

Events

06-23-2020

Abstract:

273
Does timing of AI affect P/AI in seasonal-calving, pasture-based lactating dairy cows inseminated with sex-sorted sperm?
E. Drake1,2, S.A. Holden1, A.R. Cromie3, F. Randi4, P. Lonergan2, S.T. Butler*1. 1Teagasc Fermoy, Co. Cork, Ireland, 2University College Dublin Dublin 4, Ireland, 3ICBF Bandon, Co. Cork, Ireland, 4CEVA Sante Animale Bordeaux, France.

The objective was to use ovulation synchronization with timed artificial insemination (TAI) to evaluate the effect of timing of AI (16 h or 22 h after second GnRH) with frozen sex-sorted sperm on fertility performance in pasture-based dairy cows. Ejaculates from three Holstein-Friesian bulls were split and processed to provide frozen sex-sorted sperm at 4 x 106 sperm per straw (SexedUltra-4M; SS) and frozen conventional sperm at 15 x 106 sperm per straw (CONV). A modified Ovsynch protocol with a PRID inserted for 8 days was used to synchronize ovulation in 2175 cows on 24 herds. Cows were randomly assigned to receive TAI 16 h after the second GnRH injection for cows assigned to CONV and either 16 h (SS-16) or 22 h (SS-22) for cows assigned to SS (n = 725 cows/treatment). All cows were only used for first AI. Generalized linear mixed models were used to examine effects on pregnancy per artificial insemination (P/AI). P/AI was greater (P<0.001) for CONV compared to both SS-16 and SS-22 (61.0%, 49.3% and 51.3%, respectively), and the SS treatments did not differ from each other (relative P/AI for SS-16 and SS-22 vs. CONV were 80.8% and 83.9%, respectively). There were significant bull and treatment by bull interaction effects. Marked herd to herd variation in relative P/AI was observed (range: 50.9% to 116.8%). The best third of herds achieved a mean relative P/AI of 101.5% (range = 93.9% to 116.8%), indicating that P/AI equivalent to CONV was achieved with SS. Conversely, the lower third of herds achieved a mean relative P/AI of 67.4% (range = 50.9% to 76.9%). All herds had acceptable P/AI with CONV (range 53.6% to 71.0%), indicating good response to the synchronization protocol and induction of a fertile ovulation event. Identification of factors responsible for the large herd to herd variation in P/AI with SS, and development of protocols to reduce this variation, warrant further research.

Keywords: sex-sorted sperm, synchronization, fixed time AI.