A Practical Approach, Second Edition=Ronald D. Ho.pdf

TESTING FOR REPRODUCTIVE TOXICITY 4718. All Pups in a Litter DieIf all the pups in a litter die, the dam may remain in the study until her scheduled sacrifice date,or the dam may be sacrificed at the discretion of the study director.9. Gender Determination ErrorsIf it is discovered that an error was made in the determination of pup gender, the appropriate editshould be written and the raw data (manual form or computer printout) corrected for that day andeach preceding day. For example, if a sexing error is found at necropsy of a culled pup on LD 7,an edit is written to correct the gender, and the data from the previous lactation days are corrected.After the litter observations, the bedding in the nesting box can be replaced with clean beddingor a new box with clean bedding can be obtained. The dam is weighed and observed for clinicalsigns, and the feed jar is weighed (if appropriate). The dam and pups are placed into the clean box,and the dam’s cage tag and feed jar are transferred to the new box. The nesting box is returned tothe rack.A. Pup Body Weights1. Pup Birth WeightVI. PUP EVALUATIONSBirth weight should always be measured for each pup on the day of parturition. Data from individualpups are reported as the entire litter weight and as weight by sex per litter. Growth rate in utero isinfluenced by the normality of the fetus, uterine milieu, uterine position, and fetal gender, withfemales tending to be smaller than males. 163 Maternal nutritional status, intrauterine growth rates,litter size, and gestation length influence birth weights. Individual pups in small litters tend to belarger than pups in larger litters. Therefore, reduced birth weights that can be related to large littersize or increased birth weights that can be related to small litter size should not be considered anadverse effect unless the altered litter size is considered treatment related and survivability and/ordevelopment of the offspring have been compromised.2. Postnatal Pup Body WeightsPostnatal weights are dependent on litter size and on pup gender, birth weight, suckling ability,and normality, as well as on maternal milk production. With large litters, small or weak offspringmay not thrive and may show further impairments in growth or development. Because one cannotdetermine whether growth retardation or decreased survival rate was due solely to the increasedlitter size, these effects are usually considered adverse developmental effects. Conversely, pupweights in very small litters may appear comparable to or greater than control weights and thereforemay mask decreased postnatal weights in other litters.3. Crown-Rump LengthCrown-rump lengths for fetuses are measured with a caliper. Fetuses may be euthanized beforemeasuring the crown-rump length. Place each fetus on its side on a flat surface, and place thecaliper with one prong touching the top of the head and the opposite prong touching the base ofthe tail. Do not stretch or compress the fetus. Record the measurements in millimeters.© 2006 by Taylor & Francis Group, LLC