Sprague Dawley® Rat Model - Taconic

Sprague Dawley® Rat 

The most widely used outbred rat model for research, the 

Sprague Dawley ® is ideal for applications requiring accurate 

estimation of gestational age. 

The excellent reproductive performance of the Sprague Dawley ® model makes it a 

preferred choice for generating timed-pregnant females. Taconic’s proven process for 

producing this model ensures timed-pregnant rats bearing litters within a 24-hour 

window of gestational age. 

Options Available: 

The preferred choice 

for generating timedpregnant 

females. 

This booklet presents abridged descriptions. For additional information on model origins and pricing as well as 

model datasheets and references, please see the Taconic website at www.taconic.com. 

US: 1-888-822-6642 • custserv@taconic.com | Europe: +45 70 23 04 05 • taconiceurope@taconic.com

Sprague Dawley ® Rat Model 

The Sprague Dawley ® outbred model was developed 

by R. Dawley, Sprague-Dawley Company, Madison, 

Wisconsin, in 1925. NIH received stock in 1945 

and Taconic later received stock from the NIH 

Animal Genetic Resource in 1970. Refreshed with 

NIH Genetic Resource stock in 1998, the rats are 

maintained by rotational breeding in a closed colony. 

Nomenclature: NTac:SD 

Characteristics 

• Most widely used outbred rat in biomedical 

research 

• Excellent reproductive performance, 

making it an ideal model for generating 

timed-pregnant females 

• Docile nature 

• Coat Color: Albino 

• Coat color loci: Tyr c 

Sprague Dawley ® One Year Growth 

6 7 8 9 10 11 12 13 14 15 16 17 18 22 26 30 34 38 42 46 50 54 58 

Research Applications 

• Toxicology, safety & efficacy testing, 

reproduction and development, 

behavior, aging, teratology, oncology, 

nutrition, and pharmacology studies 

• Study of maternal and fetal 

infection (Riggs) 

• Study of the effects of pre-natal 

high-salt diet on offspring 

(Porter) 

• Study of the effects of sex and 

hormonal status on restraint- 

stress-induced working memory 

impairment (Shansky) 

• Study of bone-specific 

osteocalcin gene in mouse and 

rat (Rahman) 

• Study of hippocampal excitability 

during the estrous cycle in 

rats (Scharfman) 

US: 1-888-822-6642 • custserv@taconic.com | Europe: +45 70 23 04 05 • taconiceurope@taconic.com 

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600 

500 

400 

300 

200 

100 

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Sprague Dawley ® Physiological Data 

Parameter Units SD Males SD Females 

Serum Chemistry Avg±D.D. 

Glucose mg/dL 82.4 ± 11.3 93.2 ± 10.3 

Creatinine mg/dL 0.3 ± 0.1 0.3 ± 0.1 

BUN mg/dL 9.1 ± 1.4 13.6 ± 3.0 

Total Bilirubin mg/dL 0.1 ± 0.0 0.1 ± 0.0 

Total Protein 

Blood Counts 

Erythron 

g/dL 6.4 ± 0.2 6.7 ± 0.2 

Red Blood Cells x106 /µL 6.9 ± 0.3 7.7 ± 0.3 

Nucleated RBC x106 /µL 0 0 

Hemoglobin g/dL 14.5 ± 0.8 16.1 ± 0.6 

Hematocrit % 48.3 ± 2.3 51.2 ± 2.6 

MCV fL 69.9 ± 1.7 66.9 ± 0.9 

MCH pG 20.9 ± 1.3 21.0 ± 1.1 

MCHC 

Platelets 

% 29.9 ± 1.6 31.4 ± 1.9 

Platelets x103 Leukogram 

/µL 1358.0 ± 123.8 1262.2 ± 278.4 

White Blood Cells x103 /µL 9.4 ± 3.2 6.0 ± 1.5 

Neutrophil x103 /µL 0.9 ± 0.5 0.4 ± 0.3 

Bands x103 /µL 0 0 

Lymphocyte x103 /µL 8.3 ± 2.9 5.5 ± 1.4 

Monocytes x103 Urinalysis 

/µL 0.3 ± 0.3 0.1 ± 0.1 

Glucose mg/dL Negative Negative 

Blood Negative Negative 

pH 6.75 ± 0.35 6.7 ± 0.4 

Protein mg/dL N/A N/A 

Specific Gravity 1.0195 ± 0.0068 1.0155 ± 0.0079 

Life Span 24 - 36 Months 

Food Consumption 4-5g/100g Body Weight 

Water Consumption 8-11ml/100g Body Weight 

Additional Data n=10 

Available at taconic.com/SD 

There are three health 

standard options available 

for Sprague Dawley ® : 

• Murine Pathogen Free 

• Restricted Flora 

• Germfree 



Flexible Health 

Standard Options 

Taconic offers the Sprague Dawley ® model 

at a variety of health profiles, enabling you 

to choose a profile that suits the needs of 

your specific research project and facility. 

Transportation methods for all models are 

designed to ensure the integrity and safety of 

your animals during shipment. 

Rats bred to the Restricted Flora TM (RF) 

health standard and Murine Pathogen Free TM 

(MPF) health standard are shipped in our 

unique Taconic Transit CageTM . Taconic is 

the only commercial supplier of the Sprague 

Dawley ® model at the Germfree (GF) health 

standard, delivered in our Germ-Free 

Shippers. Regardless of the health standard 

selected, Taconic Sprague Dawley ® rats 

provide 95% or greater accuracy on timedpregnant 

gestation.


The Role of Timed-Pregnant 

Sprague Dawley ® Rats in 

Biomedical Research 

The ability to monitor embryonic development and 

accurately determine gestational age of lab animal 

embryos is vital in many areas of biomedical research. 

For this reason, embryos of timed-pregnant Sprague- 

Dawley rats are used in the study of embryonic 

development, teratology and reproductive toxicology, as 

well as experiments using fetal tissue that requires cell 

harvesting and culturing at specific embryonic ages. 

Critical investigations by R.J. Blandau and his colleagues 

more than 50 years ago established procedures 

for measuring and timing gestational development 

in rats with high accuracy. Monitoring gestational 

development requires a reliable determination of the 

time of conception. Since no scientific method exists 

to determine the exact time of conception, indirect 

indicators are used. Vaginal swabs can confirm male 

fertility and offer a quantitative indicator of the likelihood 

of fertilization, making the presence of sperm in the 

vagina of female rats in estrus a reliable indicator 

of conception. 

The female rat accepts the male for mating only at the 

end of the 12-hour preliminary period of proestrus and 

during the 12 hours of estrus. Ovulation occurs about 

10 hours after the onset of estrus. Sperm migrate 

from the uterus to the oviduct about 15 minutes after 

copulation; at one hour, sperm are found throughout 

the oviduct and at three hours, 90% of the ova are 

fertilized. Based on this data, using proper monitoring 

and controls, the onset of embryonic development can 

be estimated with considerable accuracy. 


Gestational age is measured from the time of 

conception, which marks the beginning of embryonic 

Day 1. At 24 hours after conception, as Day 2 begins, 

the embryo has cleaved or is about to cleave into the 

two-cell stage. At the beginning of Day 4, the embryo – 

a morula that contains 12 to 16 cells – begins to enter 

the uterus. Implantation usually begins on the evening of 

Day 5 as the embryo settles into the maternal uterine 

wall. Implantation occurs when the blastocyst, or 

germinal vesicle, becomes clasped by the endometrium; 

the blastocyst orients itself with the inner cell mass 

facing the underlying maternal tissue. Estrogen and 

other hormonal conditions in the uterus affect the rate 

of development at implantation. 

During Day 6, the blastocyst increases in size and 

elongates. Implantation sites are visually evident by 

Day 7. During Days 9 and 10, the beginning of somite 

formation takes place. Somites – segments formed on 

either side of the embryo’s neural tube – develop into 

external body forms as they transform into muscle 

mass connected to a spinal nerve. The number of 

somites increases at a known progression, which can 

be used to track development. 

The organogenesis stage begins at Day 5 and continues 

for 8 or 9 days. During this period rudimentary 

organs, or anlagen, appear. The anlagen undergo 

cellular growth, with development branching off or 

differentiating toward unique organs and an adult organ 

morphology achieved. This is the period of greatest 

susceptibility to carcinogens or teratogens, which cause 

fetal tumors, malformations or disruption of the normal 

development rate.

Following organogenesis, the embryo enters the stage 

of maturation, the time when organs grow and become 

functionally complete. By Day 15 the embryo’s head 

is growing faster than the rump; the previously pearshaped 

body evolves into a cylindrical shape; the eyelids 

are formed and fused. The bones develop joint cavities 

over several days of maturing development. The joint 

cavities develop for the shoulder, elbow, hip, and knee 

joints during Day 16, the carpal and tarsal joints on Day 

17, and the digital joints of the legs during Day 19 or 

20. By Day 22, blood-forming activity in the liver nearly 

ceases with the end of gestation. Since the gestation 

period is 21 to 23 days, Day 22 is the average date 

of birth. 

Another measure of gestational age is embryo crown-torump-length, 

for which standard rates of development 

are well documented. The crown-to-rump measurement 

is taken from the vertex to the rump, taking care to 

45 

40 

35 

30 

25 

20 

15 

10 

5 

0 



Fetal Crown-to-Rump Lengths 

avoid caliper pressure that would distort the natural 

curvature of the embryo. At Day 11, there are 4 to 13 

somites and the average crown-to-rump length is 2.00 

mm. By Day 16, there are 58 to 65 somites and the 

crown-to-rump length is about 13.5 mm. At Day 22 

– the average date of birth – the crown-to-rump length 

ranges from 40.5 to 42.6 mm and the weight of the 

neonate is 5.9 to 6.4 grams. 

Many factors influence the rate of embryo development, 

including the light-dark cycle that affects the onset of 

ovulation, the initial position of the embryo in the genital 

tract, the hormonal variables of the mother, litter size, 

maternal diet and environmental conditions. During 

the complex processes of development, toxicological 

and environmental factors also can affect the rate of 

development. As a result, the actual rate of embryo 

development can vary from the nominal gestational age. 

11 12 13 14 15 16 17 18 19 20 21 22 

Days In Gestation


Production of Timed-Pregnant 

Sprague Dawley ® Rats at Taconic 

Taconic breeding specialists use proven, highly effective 

procedures to produce timed-pregnant Sprague- 

Dawley ® 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 

define with accuracy 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 setup the prior day, animal 

care technicians take vaginal swabs of females cohoused 

with males between 7 and 10 a.m. daily. 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 mate 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. To avoid confusion over conflicting 

conventions for defining gestational age, 

Taconic advises investigators to specify the 

sperm-positive date when ordering timedpregnant 

Sprague Dawley ® rats. 


Since Taconic’s method for selecting timed-pregnant 

females results in full-term pregnancies approximately 

95% of the time, we do not supply extra rats with each 

order. However, spontaneous abortions and small litters 

of fewer than four pups do occur on occasion. When 

expending considerable time and resources to prepare 

for a study using timed-pregnant rats on a specific day 

– and especially when using a small number of dams 

or fetuses – we advise you to order extra timedpregnant 

rats. 

Reproduction Parameters 

of Sprague Dawley ® Rats 

Male Rats 

Age at pairing (mating): 8-10 weeks 

Weight at pairing: 250-300 grams 

Period of “Economic Reproductive Ability”: 6-9 months 

Female Rats 

Age at pairing (mating): 8-10 weeks 

Weight at pairing: 180-225 grams 

Period of “Economic Reproductive Ability”: 6-9 months 

Length of estrous cycle: 4-5 days 

Duration of estrous: 10-20 hours 

Time of ovulation: 8-11 hours after onset of estrous 

Gestation 

Time of copulation: Near midpoint of previou dark cycle 

Time sperm is detected in vagina: Day 1 

Time of implantation: Late Day 5 

Length of gestation: 21-23 days

Contact Us 

Consult with our specialists to discuss your Sprague Dawley ® needs: 

Taconic (US): 

1-888-822-6642 or custserv@taconic.com 

Taconic (Europe): 

+45 70 23 04 05 or taconiceurope@taconic.com 

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Sprague Dawley® Rat Model - Taconic

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