Biological Data
| | Mouse | Rat |
| Oestrus cycle | 4-5 days | 4-5 days |
| Gestation period | 19-21 days | 21-22 days |
| Litter Size | 6-10 | 6-14 |
| Weaning Age | 18-21 days | 20-21 days |
| Birth Weight* | 1.5-2.0 g | 6-8 g |
| Weaning Weight* | 10-12 g | 40-60 g |
| Weight at Puberty* | 18-22 g | 150-200 g |
| Adult Weight* | 30-35 g | 350 g |
| Puberty | 42 days | 70-80 days |
| Diet-daily consumption | 5g | 15g |
| Water-daily consumption | 6ml | 35ml |
* This information has been obtained from standard textbooks and not from animals at the Animal Resources Centre. Weights (*) refer to outbred animals. Inbred animals generally have lower body weights than outbreds. Adult males may be considerably heavier than females.
Average organ weights of Wistar rats at 29 months
| | Male | Female | %Bwt male | %Bwt female |
| Whole Body (g) | 519 | 341 | | |
| Brain (g) | 2.090 | 1.970 | 0.4 | 0.4 |
| Hypophysis (mg) | 19 | 29 | 0.004 | 0.009 |
| Thyroid (mg) | 38 | 27 | 0.007 | 0.008 |
| Thymus (g) | 0.199 | 0.141 | 0.141 | 0.04 |
| Heart (g) | 1.563 | 1.125 | 0.3 | 0.3 |
| Liver (g) | 15.495 | 9.905 | 3.0 | 3.0 |
| Spleen (g) | 1.628 | 0.907 | 0.3 | 0.3 |
| Kidneys (g) | 4.491 | 2.337 | 0.7 | 0.7 |
| Adrenals (mg) | 84 | 80 | 0.02 | 0.02 |
| Adrenals (g) | 3.622 | 0.127 | 0.7 | 0.04 |
| Prostate (g) | 0.557 | | 0.1 | |
| Seminal Vesicles(g) | 1.334 | | 0.3 | |
(Source: IFFA CREDO Laboratory Animals).
