Effect of season and exposure to heat stress on oocyte competence in Holstein cows
Effect of season and exposure to heat stress on oocyte competence in Holstein cows
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DOI：
10.3168/jds.s0022-0302(02)74086-1
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发表时间：
2002-02-01
影响因子：
3.5
通讯作者：
Hansen, PJ
中科院分区：
文献类型：
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作者：
Al-Katanani, YM;Paula-Lopes, FF;Hansen, PJ
为了评价荷斯坦奶牛卵母细胞能力的季节变化，并测试夏季卵母细胞质量是否受热应激程度的影响，进行了两个试验。在第一个实验中，从屠宰场采集荷斯坦奶牛的卵巢，用于收集1年以上的卵母细胞(n=18个重复)。在体外成熟、受精和培养后，8天前发育到囊胚的卵母细胞和卵裂胚胎比例在暖季低于冷季。在第二个实验中，非哺乳期荷斯坦奶牛在屠宰前在以下三种环境之一饲养42d：热应激(夏季用遮阳布饲养；n=14)；凉爽(夏季饲养在有雾气和风扇的自由牛舍中；n=14)；冬季(与热应激组相似；n=12)。在发情周期的第18天至第19天屠宰奶牛。分别从每头奶牛最大的两个卵泡中抽取卵母细胞进行培养。然后解剖卵巢，收集额外的卵母细胞，并将其分组处理，进行体外成熟、受精和培养。不同处理之间的卵裂率相似，但单独培养的卵母细胞均未发育到囊胚。在其他组培养的卵母细胞中，第8天发育到囊胚的卵母细胞和卵裂胚胎的比例在夏季低于冬季，但热应激组和冷处理组之间没有差异。夏季荷斯坦奶牛卵母细胞质量下降明显，但冷却42d并不能缓解这种季节性影响。
Two experiments were conducted to evaluate seasonal variation in oocyte competence in Holstein cows and to test whether oocyte quality in summer is affected by the magnitude of heat stress. In the first experiment, ovaries of Holstein cows were collected from a slaughterhouse and used to harvest oocytes over 1 yr (n = 18 replicates). After in vitro maturation, fertilization., and culture, proportions of oocytes and cleaved embryos that developed to blastocysts by d 8 were lower in the warm season compared with the cool season. In the second experiment, nonlactating Holstein cows were housed in one of the following three environments for 42 d before slaughter: heat stressed (housed with shade cloth in summer; n = 14); cooled (housed in a free-stall barn with foggers and fans in summer; n = 14); and winter (housed similar to the heat-stressed group; n = 12). Cows were slaughtered at d 18 to 19 of the estrous cycle. Oocytes from the two largest follicles per cow were aspirated and cultured individually. Ovaries were then dissected to collect additional oocytes that were processed in a group for in vitro maturation, fertilization, and culture. Cleavage rates were similar among treatments, but none of the individually cultured oocytes developed to blastocysts. For other oocytes cultured in groups, proportions of oocytes and cleaved embryos that developed to blastocysts by d 8 were lower in summer than winter with no difference between the heat-stressed and the cooled treatment groups. Summer depression in oocyte quality in Holstein cows was evident, but cooling cows for 42 d did not alleviate that seasonal effect.