In vitro induction of the acrosome reaction in bull sperm and the relationship to field fertility using low-dose inseminations

Birck, A.; Christensen, P.; Labouriau, R.; Pedersen, J.; Borchersen, S.

doi:10.1016/j.theriogenology.2009.10.010

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Volume 73, Issue 9 , Pages 1180-1191, June 2010

In vitro induction of the acrosome reaction in bull sperm and the relationship to field fertility using low-dose inseminations

A. Birck
- Copenhagen University, Faculty of Life Sciences, Department of Large Animal Sciences, Veterinary Reproduction and Obstetrics, Frederiksberg, Denmark
- Present address: SPZ Lab A/S, Fruebjergvej 3, 2100 Copenhagen OE, Denmark.
- Corresponding author. Tel.: +45 39 17 97 84; fax: +45 39 17 97 66.
P. Christensen
- Copenhagen University, Faculty of Life Sciences, Department of Large Animal Sciences, Veterinary Reproduction and Obstetrics, Frederiksberg, Denmark
- Present address: SPZ Lab A/S, Fruebjergvej 3, 2100 Copenhagen OE, Denmark.
R. Labouriau
- Aarhus University, Faculty of Agricultural Sciences, Department of Genetics and Biotechnology, Tjele, Denmark
J. Pedersen
- The Danish Cattle Federation, Danish Agricultural Advisory Service, Aarhus, Denmark
S. Borchersen
- Dansire, Randers, Denmark

Received 1 February 2009; received in revised form 20 September 2009; accepted 11 October 2009. published online 16 March 2010.

Abstract

The acrosome reaction (AR) is a prerequisite for normal sperm fertilizing capability and can be studied in vitro after induction by various agents. The efficacy of a sperm population to undergo the AR in vivo is expected to influence male fertilizing potential. During the past two decades, a number of attempts have been made to relate the in vitro–induced AR to field fertility in several species. However, to our knowledge, no studies have combined in vitro induction of the AR with the simultaneous detection of sperm viability and acrosomal status using a high-precision flow cytometric technique. Furthermore, large-scale fertility trials using low-dose inseminations are pending. In the current study, the relationship between field fertility and the in vitro–induced AR was investigated using three ejaculates from each of 195 bulls, 156 Holstein and 39 Jersey bulls (Bos taurus), participating in a progeny test program including low-dose inseminations. A range of insemination doses, varying from 2.0×10⁶ to 15×10⁶ sperm/dose, was obtained by a controlled dilution process applied to each ejaculate. Different insemination doses were distributed at random among 75,610 experimental first inseminations in 4721 herds and 208 artificial insemination (AI) technicians. Simultaneous detection of sperm viability and acrosomal status was achieved using a triple color flow cytometric technique. Sperm samples from the bulls displayed a wide range of ability to acrosome react in response to calcium ionophore A23187. Both reproducibility of the AR response after induction and relationship between ability to acrosome react and field fertility was highly dependent on the definition of AR inducibility. Six basic and six combined AR indices were assessed. The AR index expressing the fraction of acrosome reacted sperm in the live sperm population after induction by ionophore had the highest repeatability, best described the biological variation in the studied population, and yielded the best significant predictive values on field fertility among the 12 indices considered. Moreover, the ability of sperm to acrosome react appeared to be a noncompensable trait that affects fertility regardless of the number of sperm per insemination dose. The current results therefore indicate that this sperm parameter is important in the field and also may play a role in the IVF laboratory.