Taconic's breeding specialists use proven, highly effective procedures to generate timed pregnant mice and rats. While gestational age cannot be determined with total precision, strict adherence to pre-defined mating procedures, and close monitoring of female rats after they are co-housed with males, can accurately define the 24-hour period during which mating, and presumably, conception occurs.
- At Taconic, the day of sperm cell detection in females is called the sperm-positive date and is considered Day 1 of gestation.
- After co-housing females with males the prior day, Taconic technicians take vaginal swabs of females between 7 and 10 a.m. daily or do plug checks, depending on the model to confirm that mating has occurred. In Murine Pathogen Free ™ SD rats an impedance meter is used. This procedure assumes that timed-pregnant females have mated and conception has occurred from 0 to 24 hours before the designated sperm-positive date.
- Presumably, the majority of matings occur around the midpoint of the previous day's dark cycle, from 6 P.M. to 6 A.M.
- When investigators order timed-pregnant rats at a specified developmental age for delivery on a specific date, Taconic technicians select rats based on the sperm-positive date. For instance, for an order for rats bearing embryos at Day 15 of gestational age for delivery on January 15, Taconic would select timed-pregnant females with a sperm-positive date of January 1.
- Since Taconic's method for selecting timed-pregnant females results in full-term pregnancies with a high success rate as evidenced by the chart below, extra mice and rats are not supplied with each order. However, spontaneous abortions and small litters do occur on occasion. In addition, animals under 14 days do not allow for a visual confirmation of pregnancy and cannot be palpated to confirm pregnancy. When expending considerable time and resources to prepare for a study using timed-pregnant mice or rats on a specific day, and especially when requiring a specific number of pups to be born on a particular day or using a small number of dams or fetuses, please be sure to order additional animals. Please see the chart below to assist in determining the appropriate number of animals to order for your study.
Tips for Ordering
- Specify the sperm-positive date when ordering timed pregnant models.
- Taconic advises customers to order extra timed pregnant animals to prevent any potential issues.
Pregnant Animal Recommendations and Policies
- Taconic's Timed Pregnant Sprague Dawley rats exhibit greater than 95% accuracy for timing of gestational age. For additional information on Taconic's timed pregnant rats and suggestions for ordering, see our Sprague Dawley® section. Taconic recommends orders for pregnant mice be less than 18 days gestation, and orders for pregnant rats be less than 19 days in order to prevent the animals from delivering in transit.
||Under 14 days Gestation
||14+ days Gestation
|Outbred Rats (other than SD)
- If problems regarding gestational age or pregnancy with timed pregnant orders, customers should immediately contact Taconic's Customer Service Department to provide information regarding the number of animals involved and how non-pregnancy or mistiming was determined. Whenever possible, necropsy information and pictures should be provided to assist complaint investigations for a root cause. Taconic will issue the appropriate credit based on our investigation.
- All untimed pregnant orders are filled using visibly pregnant females selected from Production Colony breeders. Customers should be aware that untimed pregnant mice and rats may deliver their litters while in transit and that no assurances are given regarding the size of the litter.