Investigation of in vitro parameters and in vivo fertility of rabbit spermatozoa after chilled storage

Artificial insemination (AI) programmes in the rabbit meat industry require improved longevity of spermatozoa stored in vitro. Two studies evaluated the effects of storage temperature and extender on in vitro quality and fertility of rabbit spermatozoa over 96 h of chilled storage. In Experiment 1, three ejaculates were collected from each of five bucks and diluted 1:10 in either Extender A or B, and then divided further for storage at 5 °C or 15 °C. Sperm motility (MOT) was assessed by CASA at 0, 24, 48, 72 and 96 h of storage. Viability, acrosome integrity, mitochondrial membrane potential (MMP), oxidative stress and DNA integrity of the two best extenders were assessed by flow cytometry. Extender B at 15 °C gave significantly higher values of MOT and MMP from 24 and 72 h, respectively. At 96 h, viability, acrosome and DNA integrity were best maintained at 15 °C (P < 0.05). In contrast, storage at 5 °C resulted in lower oxidative stress from 72 h. In Experiment 2, a pilot study examined fertility rates of does inseminated with spermatozoa diluted in Extender B and stored at 5 °C or 15 °C. Sixty seven multiparous does were inseminated with spermatozoa stored for 0 h (n = 12; control), 48 h (n = 26) or 72 h (n = 29). Kindling rates and litter sizes for does inseminated with semen stored for 48 h at 5 °C or 15 °C and 72 h at 5 °C were similar (P > 0.05) to those of the controls; kindling rate dropped following insemination with spermatozoa held at 15 °C for 72 h, though litter size did not.