Sartori R, Sartor-Bergfelt R, Mertens S A, Guenther J N, Parrish J J, Wiltbank M C
Department of Dairy Science, University of Wisconsin, Madison 53706, USA.
J Dairy Sci. 2002 Nov;85(11):2803-12. doi: 10.3168/jds.S0022-0302(02)74367-1.
Two experiments in two seasons evaluated fertilization rate and embryonic development in dairy cattle. Experiment 1 (summer) compared lactating Holstein cows (n = 27; 97.3 +/- 4.1 d postpartum [dppl; 40.0 +/- 1.5 kg milk/d) to nulliparous heifers (n = 28; 11 to 17 mo old). Experiment 2 (winter) compared lactating cows (n = 27; 46.4 +/- 1.6 dpp; 45.9 +/- 1.4 kg milk/d) to dry cows (n = 26). Inseminations based on estrus included combined semen from four high-fertility bulls. Embryos and oocytes recovered 5 d after ovulation were evaluated for fertilization, embryo quality (1 = excellent to 5 = degenerate), nuclei/embryo, and accessory sperm. In experiment 1, 21 embryos and 17 unfertilized oocytes (UFO) were recovered from lactating cows versus 32 embryos and no UFO from heifers (55% vs. 100% fertilization). Embryos from lactating cows had inferior quality scores (3.8 +/- 0.4 vs. 2.2 +/- 0.3), fewer nuclei/embryo (19.3 +/- 3.7 vs. 36.8 +/- 3.0) but more accessory sperm (37.3 +/- 5.8 vs. 22.4 +/- 5.5/embryo) than embryos from heifers. Sperm were attached to 80% of UFO (17.8 +/- 12.1 sperm/UFO). In experiment 2, lactating cows yielded 36 embryos and 5 UFO versus 34 embryos and 4 UFO from dry cows (87.8 vs. 89.5% fertilization). Embryo quality from lactating cows was inferior to dry cows (3.1 +/- 0.3 vs. 2.2 +/- 0.3), but embryos had similar numbers of nuclei (27.2 +/- 2.7 vs. 30.6 +/- 2.1) and accessory sperm (42.0 +/- 9.4 vs. 36.5 +/- 6.3). From 53% of the flushings from lactating cows and 28% from dry cows, only nonviable embryos were collected. Thus, embryos of lactating dairy cows were detectably inferior to embryos from nonlactating females as early as 5 d after ovulation, with a surprisingly high percentage of nonviable embryos. In addition, fertilization rate was reduced only in summer, apparently due to an effect of heat stress on the oocyte.
在两个季节进行的两项实验评估了奶牛的受精率和胚胎发育情况。实验1（夏季）将泌乳的荷斯坦奶牛（n = 27；产后97.3±4.1天[dpp]；日产奶量40.0±1.5千克）与未产犊的小母牛（n = 28；11至17月龄）进行比较。实验2（冬季）将泌乳奶牛（n = 27；产后46.4±1.6天；日产奶量45.9±1.4千克）与干奶期奶牛（n = 26）进行比较。基于发情的人工授精使用了来自四头高繁殖力公牛的混合精液。在排卵后5天回收的胚胎和卵母细胞用于评估受精情况、胚胎质量（1 = 优秀至5 = 退化）、核/胚胎以及附属精子。在实验1中，从泌乳奶牛中回收了21个胚胎和17个未受精的卵母细胞（UFO），而从小母牛中回收了32个胚胎且无UFO（受精率分别为55%和100%）。泌乳奶牛的胚胎质量评分较低（3.8±0.4对2.2±0.3），每个胚胎的核数量较少（19.3±3.7对36.8±3.0），但附属精子较多（37.3±5.8对22.4±5.5/胚胎）。精子附着在80%的UFO上（每个UFO有17.8±12.1个精子）。在实验2中，泌乳奶牛产生了36个胚胎和5个UFO，而干奶期奶牛产生了34个胚胎和4个UFO（受精率分别为87.8%和89.5%）。泌乳奶牛的胚胎质量低于干奶期奶牛（3.1±0.3对2.2±0.3），但胚胎的核数量（27.2±2.7对30.6±2.1）和附属精子数量（42.0±9.4对36.5±6.3）相似。从泌乳奶牛的冲洗液中53%以及干奶期奶牛的冲洗液中28%只收集到了无活力的胚胎。因此，早在排卵后5天，泌乳奶牛的胚胎就明显不如非泌乳母牛的胚胎，无活力胚胎的比例惊人地高。此外，受精率仅在夏季降低，显然是由于热应激对卵母细胞的影响。
