Schou T M, Malmkvist J
Department of Animal Science,Aarhus University,Blichers Allé 20,8830 Tjele,Denmark.
Animal. 2017 Sep;11(9):1581-1589. doi: 10.1017/S1751731117000234. Epub 2017 Feb 20.
We investigated the effects of nest box climate on early mink kit mortality and growth. We hypothesised that litters in warm nest boxes experience less hypothermia-induced mortality and higher growth rates during the 1st week of life. This study included data from 749, 1-year-old breeding dams with access to nesting materials. Kits were weighed on days 1 and 7, dead kits were collected daily from birth until day 7 after birth, and nest climate was measured continuously from days 1 to 6. We tested the influences of the following daily temperature (T) and humidity (H) parameters on the number of live-born kit deaths and kit growth: T mean, T min, T max, T var (fluctuation) and H mean. The nest microclimate experienced by the kits was buffered against the ambient climate, with higher temperatures and reduced climate fluctuation. Most (77.0%) live-born kit deaths in the 1st week occurred on days 0 and 1. Seven of 15 climate parameters on days 1 to 3 had significant effects on live-born kit mortality. However, conflicting effects among days, marginal effects and late effects indicated that climate was not the primary cause of kit mortality. Five of 30 climate parameters had significant effects on kit growth. Few and conflicting effects indicated that the climate effect on growth was negligible. One exception was that large nest temperature fluctuations on day 1 were associated with reduced deaths of live-born kit (P<0.001) and increased kit growth (P=0.003). Litter size affected kit vitality; larger total litter size at birth was associated with greater risks of kit death (P<0.001) and reduced growth (P<0.001). The number of living kits in litters had the opposite effect, as kits in large liveborn litters had a reduced risk of death (P<0.001) and those with large mean litter size on days 1 to 7 had increased growth (P=0.026). Nest box temperature had little effect on early kit survival and growth, which could be due to dams' additional maternal behaviour. Therefore, we cannot confirm that temperature is the primary reason for kit mortality, under the conditions of plenty straw access for maternal nest building. Instead, prenatal and/or parturient litter size is the primary factor influencing early kit vitality. The results indicate that the focus should be on litter size and dam welfare around the times of gestation and birth to increase early kit survival in farmed mink.
我们研究了巢箱气候对水貂幼崽早期死亡率和生长的影响。我们假设，生活在温暖巢箱中的幼崽在出生后第一周因体温过低导致的死亡率较低，生长速度较快。本研究纳入了749只可获取筑巢材料的1岁繁殖母貂的数据。在第1天和第7天对幼崽进行称重，从出生到出生后第7天每天收集死亡幼崽，从第1天到第6天持续测量巢箱气候。我们测试了以下每日温度（T）和湿度（H）参数对存活幼崽死亡数量和幼崽生长的影响：平均温度（T mean）、最低温度（T min）、最高温度（T max）、温度波动（T var）和平均湿度（H mean）。幼崽所处的巢箱小气候相对于周围环境气候有缓冲作用，温度较高且气候波动较小。第一周内大多数（77.0%）存活幼崽死亡发生在第0天和第1天。第1天至第3天的15个气候参数中有7个对存活幼崽死亡率有显著影响。然而，不同天数之间的相互矛盾的影响、边际效应和后期效应表明，气候并非幼崽死亡的主要原因。30个气候参数中有5个对幼崽生长有显著影响。影响较少且相互矛盾表明气候对生长的影响可忽略不计。一个例外是，第1天巢箱温度大幅波动与存活幼崽死亡减少（P<0.001）和幼崽生长增加（P=0.003）有关。窝仔数影响幼崽活力；出生时窝仔总数越大，幼崽死亡风险越高（P<0.001），生长速度越低（P<0.001）。存活幼崽数量则有相反的影响，因为存活幼崽数多的窝中幼崽死亡风险降低（P<0.001），第1天至第7天平均窝仔数大的幼崽生长速度增加（P=0.026）。巢箱温度对幼崽早期存活和生长影响不大，这可能是由于母貂额外的母性行为。因此，在母貂筑巢有充足垫草的条件下，我们无法确定温度是幼崽死亡的主要原因。相反，产前和/或分娩时的窝仔数是影响幼崽早期活力的主要因素。结果表明，应关注妊娠期和分娩期前后的窝仔数和母貂福利，以提高养殖水貂幼崽的早期存活率。
