154 A method of oviductal semen deposition for use in the goat

Abstract

The objective of this study was to investigate a method of oviducal semen deposition as a strategy for producing offspring from poor-quality cryopreserved goat sperm. In vitro fertilisation (IVF) and AI are common assisted reproductive technologies used in small ruminants, but they have varied results in the goat. The use of poor-quality cryopreserved-thawed sperm (<50% live/dead ratio at post-thaw) can decrease the rate of success. These procedures were performed in the month of November in Central Massachusetts in the United States (42° N). Seven 10-year-old dairy goats (Saanen, Toggenburg, and Alpine breeds) were synchronised and superovulated using a progesterone implant on Day 0, a prostaglandin injection at Day 7, two daily injections of 36 mg of FSH ~12 h apart on Days 12-15, and progesterone implant removal on Day 14 followed by an injection of 50 µg of gonadotrophin-releasing hormone. Sperm deposition was performed on Day 17 (72 h after implant removal). The animals were anaesthetised using a standardised protocol, intubated, and maintained using isoflurane, and sterile prep was performed before a midline laparotomy procedure. Straws from a single ejaculate from a transgenic founder that was cryopreserved using a commercial two-step glycerol-egg yolk-based extender were used. A straw from this collection was post-thawed 30 days after collection and, using a commercial live/dead stain, 67% live sperm was determined. The optimal type of sperm prep and sperm concentration is unknown and may be dependent on sperm quality. Therefore, different gradient preps using Vitrolife SpermGrad at three volumes (1.5 (used on two animals), 1.0, and 0.5 mL) as well as two volumes of IVF Bioscience Bovine BO-SemenPrep (4.0 mL (used on two animals) and 2.0 mL) were used. All five pellets were diluted in 1.0 mL of IVF Bioscience Bovine BO-IVF media. Sperm concentrations ranging from 75 × 10⁶ to 27 × 10⁶ sperm mL⁻¹ were deposited into one oviduct; then, a 10:1 dilution was performed and 7.5 × 10⁶ to 2.7 × 10 sperm mL⁻¹ were deposited into the contralateral oviduct. The depositions were performed just proximal to the uterotubal junction in a volume of 0.1 mL of diluent via a tuberculin syringe attached to a 20-gauge needle. Two days following the procedure, oviducts were flushed postmortem from three of the seven randomly selected goats. All three had fertilised embryos, and nineteen 8-cell embryos were retrieved. Three of these embryos were surgically transferred to the distal uterine horn of a suitable recipient. The recipient became pregnant and produced a single offspring. The remaining four of seven goats were killed 41 days post-surgery. Two of the four goats were pregnant, with one carrying one fetus and the other carrying five fetuses. Further studies are needed to optimise this method, but these initial results indicate that oviducal semen deposition directly into the oviduct proximal to the uterotubal junction may be a suitable alternative for producing offspring from suboptimal cryopreserved-thawed goat sperm.