Protocol for the Recovery of In Vivo Matured Canine Oocytes Based on Once Daily Measurement of Serum Progesterone

Abstract

The collection of in vivo matured canine oocytes relies on the accurate prediction of ovulation. The present study was designed to develop a protocol for the recovery of in vivo matured canine oocytes based on once daily measurements of serum progesterone (P₄) concentrations. Blood samples (2 mL) were collected every day at 0900 h, and P₄ concentrations were analyzed using a DSL-3900 ACTIVE^® Progesterone Coated-Tube Radioimmunoassay Kit. The average number of oocytes at the metaphase II (M II) stage was significantly higher at or after 72 h (6.7 to 7.5) compared to 56 h (1.7) following ovulation. The highest numbers of corpora lutea, and therefore the highest numbers of oocytes, were recovered from bitches with initial ovulatory P₄ concentrations ranging from 6.0 to 8.0 ng/ mL (12.2 and 11.4, respectively) compared to from 4.0 to 4.9 ng/ mL (9.6 and 8.8, respectively; p < 0.05). The average number of M II oocytes recovered at 84 h from bitches with initial ovulatory P₄ levels of 5.0 to 5.9 ng/mL (7.7) was higher compared to bitches with P₄ levels of 4.0 to 4.9 ng/ mL (3.5) and 6.0 to 8.0 ng/ mL (4.8; p < 0.05). When oocyte recovery time was adjusted for initial ovulatory P₄ concentration, no significant difference in recovery rates or oocyte quality were observed. In conclusion, once daily measurements of P₄ can be used to predict ovulation in bitches, and oocyte recovery time should be adjusted for initial ovulatory serum P₄ concentrations.