Effect of initial mating age on reproductive performance in NIH mice
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1.National Research Institute for Family Planning, Beijing 100081, China. 2. Zhongmu Industrial Co., Ltd., Beijing 100070

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R-33

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    Abstract:

    Objective We systematically studied the effects of initial mating age on reproductive performance in NIH mice. Methods Thirty pairs of mice were divided into 4 groups according to initial mating age: 50, 60, 70, or 85 days old. For the first to sixth litters from each pair, we recorded the average litter size, number of weaned mice, weight of the natal mice and weaned mice, and calculated the weaning rate and day, and compared these between the age groups. Results Compared with the 50-day-old group, the 70- and 85-day-old groups were significantly or extremely significantly different in terms of the average litter size, number of weaned mice, weaning rate, and weight of the natal mice and weaned mice (P< 0. 05, P < 0. 01). Compared with the 60-day-old group, the 70 - and 85-day-old groups were significantly different in terms of average body weight and the number of weaned mice (P< 0. 05). There were no differences in the intervals between litters among the groups (P> 0. 05). The average litter size in NIH mice for the second and third litters was significantly higher than that for the first litter (P< 0. 05). The fifth and sixth litters had a significantly decreased average size (P< 0. 05). The number of weaned mice in the third and fourth litters was different from that in the first litter (P< 0. 05). The average body weight and lactation rate of the mother increased with the age of parity (P< 0. 05, P< 0. 01). The average body weight and weaning rate of the infant mice increased with the age of parity. There were no significant differences in the average body weight of the weaned mice (P> 0. 05). Conclusions NIH mice have better reproductive performance at 70 ~ 85 days of age, and the second and third births are stable in terms of reproductive performance. For propagation of research animals, up to six litters are recommended.

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History
  • Received:November 11,2019
  • Revised:
  • Adopted:
  • Online: June 19,2020
  • Published: