Time Mating Guinea Pigs by Monitoring Changes to the Vaginal Membrane throughout the Estrus Cycle and with Ultrasound Confirmation

Abstract

One of the greatest challenges to the development and implementation of pregnancy therapeutics is the ability to rigorously test treatments in clinically relevant animal models. Guinea pigs offer a unique advantage in studying the placenta, fetal development, and reproductive health as they have similar developmental milestones to humans, both throughout gestation and following birth. Tracking the guinea pig estrus cycle is imperative to ensuring appropriately timed mating and can be performed by monitoring the guinea pig vaginal membrane. Here, we describe a methodology to efficiently and accurately time mate guinea pigs, and provide a picture representation of changes to the guinea pig vaginal membrane throughout the estrus cycle. Utilization of this monitoring enabled a 100% pregnancy success rate on the first mating attempt in a cohort of five guinea pigs. This approach, along with early pregnancy ultrasounds as a secondary method to confirm pregnancy, offers a reliable approach to timed mating in the guinea pig.

Nanoparticle‐mediated transgene expression of insulin‐like growth factor 1 in the growth restricted guinea pig placenta increases placenta nutrient transporter expression and fetal glucose concentrations

“…In the initial studies to determine nanoparticle uptake and transgene expression in the guinea pig placenta, the Texas Red conjugated polymer was complexed with plasmid containing the GFP gene. Dams ( n = 6; 2 sham, 2 Plac1 promotor, 2 Cyp19a1 promotor) were time mated through daily monitoring of the estrus cycle by inspecting perforation of the vaginal membrane (R. Wilson et al, 2021). Ovulation was assumed to occur when the vaginal membrane was fully perforated and designated gestational day (GD) 1.…”

Cloprostenol effect with and without male stimulation on oestrus synchronization in Peru guinea pigs

“…On the contrary, an inversed relationship was observed, indicating a decrease in oestrus intensity following an initial peak as follicle growth approached its maximum (Myers et al., 1936). Notably, approximately 4 or 5 days before ovulation, changes in vulvar coloration with edematization occur before mating (Goldman et al., 2007; Wilson et al., 2021). In another study, Vargas‐Rojas et al.…”

“…The oestrus onset time and duration were recorded in minutes and converted later to hours. The oestrus intensity was classified by a subjective scale as frank, moderate, and mild by direct observation of the female's sexual behaviour due to male stimulation (Table 1) and changes in the vaginal membrane (Wilson et al., 2021).…”

“…In general, the application of reproductive biotechnology in guinea pigs is scarce and deficient. Guinea pigs exhibit polyestrous behaviour all year round, with an oestrous cycle lasting 15 to 16 days (Wilson et al., 2021). Guinea pigs are spontaneous ovulators and exhibit polyestrous breeding patterns under laboratory conditions.…”

“…Note: ++++: very pronounced; +++: noticeable; ++: weak; +: barely noticeable; −: not present. a Adapted fromWilson et al (2021).TA B L E 2Oestrus onset time in guinea pigs after cloprostenol administration (15 females per group).Dose (…”