A Comparison of Oocyte Yield between Ultrasound-Guided and Laparoscopic Oocyte Retrieval in Rhesus Macaques

SIMPLE SUMMARY: Research using Assisted Reproductive Technology (ART) in non-human primates (NHPs) is fundamental for improving human reproductive health as well as for generating models of disease. The first critical step for many studies utilizing ART is to obtain high-quality oocytes. Two techniques for oocyte retrieval are currently used at the Oregon National Primate Research Center (ONPRC): the standard surgical approach by laparoscopy and the less invasive ultrasound-guided approach. From a welfare perspective, ultrasound-guided oocyte retrieval provides many benefits; however, it has not been established whether this technique has a similar efficacy to laparoscopy. In our study, we compared an extensive data set on oocyte yield and fertilization rates from laparoscopic and ultrasound-guided oocyte retrievals in Rhesus macaques. Our analysis reveals that the ultrasound-guided technique is equivalent to the laparoscopic one in those aspects. In summary, the two techniques yielded statistically equivalent oocyte yields, therefore, the less invasive ultrasound-guided oocyte retrieval technique is recommended as a refinement that improves animal welfare. ABSTRACT: Obtaining quality oocytes is a prerequisite for ART-based studies. Here we describe a method for transabdominal ultrasound-guided (US) oocyte retrieval in rhesus macaques (Macaca mullata) and compare it to the standard surgical approach using laparoscopy (LAP). We analyzed oocyte yield from six continuous reproductive seasons (2017–2023) that included n = 177 US-guided and n = 136 laparoscopic oocyte retrievals. While the ultrasound-guided technique retrieved significantly fewer oocytes on average (LAP: 40 ± 2 vs. US: 27 ± 1), there was no difference in the number of mature metaphase II oocytes (MII) between the two techniques (LAP: 17 ± 1 vs. US: 15 ± 1). We show that oocytes retrieved by the ultrasound-guided approach fertilize at the same rates as those obtained via the laparoscopic procedure (LAP Fert Rate: 84% ± 2% vs. US Fert Rate: 83% ± 2%). In conclusion, minimally invasive ultrasound-guided oocyte retrieval improves animal welfare while delivering equivalent numbers of mature oocytes, which are ideal for ART. Furthermore, we show that oocyte competency, as represented by fertilization rate, is not affected by retrieval technique. Therefore, the Oregon National Primate Research Center (ONPRC) has adopted the ultrasound-guided approach as the standard technique for oocyte retrieval.