Development and evaluation of deep intra-uterine artificial insemination using cryopreserved sexed spermatozoa in bottlenose dolphins (Tursiops truncatus)

Since its development in bottlenose dolphins, widespread application of AI with sex-selected, frozen–thawed (FT) spermatozoa has been limited by the significant expense of the sorting process. Reducing the total number of progressively motile sperm (PMS) required for an AI would reduce the sorting cost. As such, this research compared the efficacy of small-dose deep uterine AI with sexed FT spermatozoa (SEXED-SMALL; ~50 × 106 PMS, n = 20), to a moderate dose deposited mid-horn (SEXED-STD, ~200 × 106 PMS; n = 20), and a large dose of FT non-sexed spermatozoa deposited in the uterine body (NONSEXED-LARGE, 660 × 106 PMS, n = 9). Ten of the 11 calves resulting from use of sexed spermatozoa were of the predetermined sex. Similar rates of conception (NONSEXED-LARGE: 78%, SEXED-STD: 60%, SEXED-SMALL: 57%) and total pregnancy loss (TPL: NONSEXED-LARGE: 28.6%; SEXED-STD: 41.0%; SEXED-SMALL: 63.6%) were observed across groups, but early pregnancy loss (EPL, <day 120 post-conception) was greater (P = 0.04) for SEXED-SMALL (54.5%) compared to NONSEXED-LARGE (0%). Animals experiencing EPL were older (31.3 y, P = 0.007) than those that calved (21.4 y) or did not conceive (19.4 y). After excluding females ≥25 y, SEXED-SMALL (15.4%) had a tendency for having reduced calving rates compared to NONSEXED-LARGE (50.0%; P = 0.08), while SEXED-STD did not differ (40.0%, 4/10; P = 0.341). Current findings indicate that acceptable conception and calving rates using sexed FT spermatozoa are achieved after mid-horn deposition of 200 × 106 PMS, when used with females aged less than 25 y.