In the current era of genomic selection, there is an increased demand to collect semen from genomically selected sires at a young age. The objective of this study was to assess the effect of bull age, ejaculate number, and season of collection on semen production (ejaculate volume, sperm concentration, and total sperm number; TSN) and sperm motility (prefreeze and post-thaw total and gross motility) parameters in Holstein Friesian bulls in a commercial artificial insemination (AI) center. The study involved the interrogation of a large dataset collected over a 4-yr period, (n = 8,983 ejaculates; n = 176 Holstein Friesian bulls aged between 9 mo and 8 yr). Bulls aged less than 1 yr had the poorest semen production and sperm motility values for all parameters assessed compared with bulls older than 1 yr (P < 0.01). First ejaculates had greater semen production and greater prefreeze motility values than second consecutive ejaculates (P < 0.01), but despite this, there was no difference in post-thaw motility. When subsequent ejaculates were collected from bulls aged less than 1 yr, semen production and sperm motility did not differ compared with mature bulls. Semen collected in winter was poorest in terms of sperm concentration and TSN, but best in terms of post-thaw motility (P < 0.01). In conclusion, second ejaculates can be collected, particularly from bulls aged less than 1 yr, without a significant decrease in post-thaw sperm motility, thus may be a useful strategy to increase semen availability from young genomically selected AI bulls in high demand.

In Ireland, liquid bull semen is stored at unregulated ambient temperatures, typically at 5×106 spermatozoa per dose, and inseminated within 2.5 days of collection. In Experiment 1, the effect of storage temperature (5, 15, 22, 32°C and fluctuations (Flux) between these temperatures) on progressive motility, viability, acrosomal status, DNA fragmentation and osmotic resistance was assessed. In Experiment 2, the field fertility of liquid semen at 5, 4 and 3×106 spermatozoa per dose, up to Day 2 after collection, was assessed in comparison to frozen-thawed semen at 20×106 spermatozoa per dose (n=35328 inseminations). In Experiment 1, storage at 15°C resulted in the highest progressive motility (PP6 spermatozoa per dose on Day 2 of storage was reduced in comparison to frozen-thawed semen (P<0.01). In conclusion, liquid semen is versatile between storage temperatures of 5 and 22°C, but demonstrates reduced fertility on Day 2 of storage at lower sperm numbers in comparison to frozen-thawed semen.

Diluents using components of plant origin have been developed as an alternative to animal based extenders for the dilution of bull semen, however, it is unclear if use of these diluents results in in vivo fertility rates similar to those that occur with use of traditional egg yolk-based diluents. The aim of this study was to assess the effect of semen diluent on 60-day non-return rate (NRR) following artificial insemination (AI) with frozen-thawed bull semen. The effect of semen dilution in one of three different commercial diluents (BullXcell - egg yolk-based, OptiXcell - plant-based or AndroMed - plant-based) on post-thaw total and progressive motility as well as kinematic parameters (Experiment 1) and field fertility (Experiment 2, n = 1,480 inseminations) was assessed. Semen stored in OptiXcell had greater post-thaw total and progressive motility than AndroMed (P < 0.05) but did not differ from BullXcell. Semen stored in BullXcell had a greater beat cross frequency and straight line velocity compared to semen stored in AndroMed (P < 0.05) but did not differ when compared with use of OptiXcell; while values for these variables when using OptiXcell and AndroMed did not differ from each other (P > 0.05). There was no difference in any other sperm kinematic parameters (P > 0.05). There was no effect of diluent on 60-day NRR (71.5%, 67.8% and 70.6% for BullXcell, OptiXcell and AndroMed, respectively). In conclusion, while diluent significantly affected post-thaw sperm motility and kinematics, no effect on 60-day NRR was observed. Given that OptiXcell and AndroMed are animal protein-free media these diluents may be a suitable alternative to BullXcell for the storage of frozen-thawed bull semen.

23The objective of this study was to assess the effects of dietary supplementation of a 24 commercial algal product rich in docosahexaenoic acid (DHA) on boar fertility as assessed in increased semen volume and total sperm numbers but had no effect on any other semen 41 quality parameter as assessed in vitro or in vivo.

Semen 3Murphy et al. 4This study examined the effect of a wide range of semen diluents on both the in vitro and in 5 vivo fertility of liquid bull semen stored for up to 3 days post collection. The semen diluents 6 BioXcell, INRA96 and Caprogen maintained sperm motility best when stored at a constant 7 temperature, however, when used in the field, at an unregulated temperature, BioXcell 8 performed poorly. This study clearly illustrates the importance of in vivo fertility data in 9 assessing semen diluents. The aim of this study was to assess the effect of semen diluent on calving rate (CR) following 10 SEMEN DILUENTS FOR LIQUID BULL SEMEN 11 A Comparison of Semen Diluents on the