Eureka! Institutional Repository

Laboratory animals have been recognized for their catalytic contribution to the evolution and development of the biosciences, especially for the lab mice whose participation in experimental trials represent more than 50% of the total lab animal population globally. The objectives of the presen study were the evaluation of the reproductive parameters (litter size in relation to the parity number, weaning rate, sex ratio, returns and replacement rate) of the HSD: ICR CD-1 lab mice strain of the specific breeding as well as the evaluation of the husbandry methods efficiency in order to improve the breeders’ performance and their welfare. The results showed that there was a significant difference (P≤0.05) between the first and second parity in litter size as well as in the number of weaned mice. Similarly, the ratio of the male born mice was greater (P≤0.05) in the first vs the second parity and the second parity vs the third one. This was not observed (P≥0.05) in the female born mice among all parities. In addition, it was observed a high incidence (44.1%) of sudden death in the lactating females during the first two parities, while a similar unexpected high incidence (16.7%) of returns was observed across all parities in contrast to the strain’s reproductive characteristics. Based on the study’s findings, the breeding stock’s reproductive characteristics, indicated by the breeding company, are within its range. However, it should be given special attention to the high incidence of sudden death in the lactating females as well as the high incidence of returns of the bred females. The above findings lead to the conclusion that the constant evaluation of the breeding stock’s reproductive performance and simultaneously the improvement of the husbandry protocol would contribute to the minimization of the above two nonproductive parameters