For a wide range of biomedical approaches, an accurate estimate of the age of embryos or pups is important. Overnight mating is the method that is mostly used to establish timed pregnancies. The oestrus cycle in mice repeats every four to five days. So, not all females will get pregnant because they are not in oestrus. Therefore, the aim of this study was to analyse whether polygamous mating could increase the rate of timed pregnancies per breeding cage and female. We compared overnight timed mating regimes with up to four females per male, using C57BL/6 and BALB/c mice as well as F1 hybrids of these two strains. The number of vaginal plugs, number of females that gave birth and weaned litter (including size and weaning weight) were recorded. Our results showed that the plug and pregnancy rate decreased, but the productivity per breeding cage increased for polygamous mating regimes. The proportion of females with vaginal plugs and females that gave birth was significantly higher in monogamous mating. The proportion of plugged females that gave birth, as well as litter size and weaning weight, were not influenced by the mating regime. After analysing 513 breeding cages with a total of 1090 females, we found that polygamous mating with up to three females per male can increase the number of timed pregnancies. However, in the mating regime with more than three females, the rate of timed pregnancy as well as number of pups per female declined.

中文翻译：

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通过使一只雄性与最多四只雌性交配，在C57BL / 6和BALB / c小鼠中进行定时妊娠的效率。

对于各种各样的生物医学方法，准确估计胚胎或幼仔的年龄很重要。隔夜交配是通常用于建立定时怀孕的方法。小鼠的发情周期每四到五天重复一次。因此，并不是所有的女性都会因为没有发情而怀孕。因此，本研究的目的是分析一夫多妻制交配是否可以提高每个繁殖笼和雌性的定时怀孕率。我们比较了使用C57BL / 6和BALB / c小鼠以及这两种菌株的F1杂种的过夜定时交配方式，每只雄性最多可携带四只雌性。记录阴道栓的数量，分娩的雌性数量和断奶的产仔数（包括大小和断奶的体重）。我们的结果表明，塞子和怀孕率下降了，但一夫多妻制交配制度下每个繁殖笼的生产率提高了。一夫一妻制的交配中，有阴道栓的雌性和分娩的雌性的比例明显更高。产卵的雌性比例，产仔数和断奶体重不受交配方式的影响。在分析了总共1090头雌性的513个繁殖笼之后，我们发现一夫多妻配偶（每头雄性最多3头雌性）可以增加定时怀孕的次数。但是，在有多于三只雌性的交配方式中，定时妊娠的速度以及每只雌性的幼崽数量都下降了。以及产仔数和断奶体重不受交配方式的影响。在分析了总共1090头雌性的513个繁殖笼之后，我们发现一夫多妻配偶（每头雄性最多3头雌性）可以增加定时怀孕的次数。但是，在有多于三只雌性的交配方式中，定时妊娠的速度以及每只雌性的幼崽数量都下降了。以及产仔数和断奶体重不受交配方式的影响。在分析了总共1090头雌性的513个繁殖笼之后，我们发现一夫多妻配偶（每头雄性最多3头雌性）可以增加定时怀孕的次数。但是，在有多于三只雌性的交配方式中，定时妊娠的速度以及每只雌性的幼崽数量都下降了。