Oral Virtual Presentation (Virtual only) ESA-SRB-ANZBMS 2021

Field fertility of a novel bovine sperm storage medium following seven days of ambient temperature storage (#156)

Erin K Klein 1 , Allan J Gunn 2 3 , Cyril P Stephen 2 3 , Mohammad Bahrami 1 , Aleona Swegen 1 4 , Robert John Aitken 1 , Zamira Gibb 1
  1. Priority Research Centre for Reproductive Science, University of Newcastle, Callaghan, NSW, Australia
  2. School of Animal and Veterinary Sciences, Charles Sturt University, Wagga Wagga, NSW, Australia
  3. Graham Centre for Agricultural Innovation, Wagga Wagga, NSW, Australia
  4. Nuffield Department of Women's and Reproductive Health, University of Oxford, Oxford, UK

Northern Australian beef producers have been slow to adopt artificial insemination (AI) practices, in favour of the more traditional hands-off approach of ‘natural’ breeding. However, the rising demand for global food security requires an increased rate of genetic gain for production traits, which can only be met using AI. By simplifying the logistics around AI and improving pregnancy rates, we aim to make this a more feasible option for beef producers. To do this we developed a novel medium, SpermSafe-B (SS-B), containing alternative osmolytes, additional energy sources, and antioxidant supplementation capable of supporting sperm metabolism during ambient temperature storage. After thorough sperm parameter assessments and in vitro fertilisation trials, the field fertility of bull spermatozoa stored in SS-B was evaluated. Semen was collected via electroejaculation from three bulls with high quality spermatozoa selected using a 45/90 discontinuous BoviPure™ density gradient, resuspended at a concentration of ~50 million/mL in SS-B, and stored in the dark at ambient temperature (~22°C). No significant decline in total (TM) or progressive (PM) motility was recorded after seven days of storage (TM: 83.3±3.06% vs. 73.0±3.18%; PM: 82.8±2.83% vs. 70.9±3.97%; at Day 0 and Day 7 respectively; P>0.15). At Day 7, fixed-time AI following oestrus synchronisation was performed on 18 2-year-old virgin heifers using an insemination dose of 0.5 mL (15.75-18.75 million progressively motile spermatozoa). Ultrasonographic pregnancy diagnosis at 33 days post-insemination confirmed 14 of 18 (77.8%) heifers were in calf. This is the first trial of its kind assessing the field fertility of bull spermatozoa in an ambient temperature sperm storage medium. While this focused trial did not directly compare to current frozen-thawed AI protocols, the pregnancy rate achieved using spermatozoa stored in SS-B was higher than the industry-standard using cryopreserved semen (60%). These results serve as proof of concept to commence a large-scale fertility trial.