Vieira L M, Rodrigues C A, Mendanha M F, Sá Filho M F, Sales J N S, Souza A H, Santos J E P, Baruselli P S
Departamento de Reprodução Animal, FMVZ-USP, São Paulo, Brazil.
Clínica Veterinária SAMVET, São Carlos, São Paulo, Brazil.
Theriogenology. 2014 Jul 15;82(2):204-12. doi: 10.1016/j.theriogenology.2014.03.018. Epub 2014 Mar 30.
The present study investigated the effect of Holstein donor category (cows vs. heifers) and climate variation (hot vs. cooler season) on the efficiency of in vivo embryo production programs as well as embryo survival after transferred to Holstein recipient cows. A total of 1562 multiple ovulation (MO) procedures (cows: n = 609, and heifers: n = 953) and 4076 embryo transfers (ETs) performed in two dairy herds were evaluated. Donor cows had greater number of CLs (10.6 ± 0.6 vs. 7.5 ± 0.4; P < 0.0001) and ova/embryos recovered (7.6 ± 0.6 vs. 4.6 ± 0.4; P < 0.0001) compared with donor heifers. However, fertilization rate (47.9 vs. 82.4%; P < 0.0001) and proportion of transferable embryos (31.5 vs. 67.4%; P < 0.0001) were lower in donor cows than heifers, respectively. Regardless of donor category, the proportion of freezable embryos was less (P < 0.001) during hot season than in cooler season (21.4 vs. 32.8%). However, greater decline in the proportion of freezable embryos during the hot season was observed in cows (21.7 vs. 10.7%) compared with heifers (46.2 vs. 38.1%; P = 0.01). In contrast, the season on which the embryo was produced (hot or cool) did not affect pregnancy rate on Day 31 (30.5 vs. 31.7%; P = 0.45) and 45 (25.3 vs. 25.1%; P = 0.64) of pregnancy. Regardless of the season in which the embryos were produced, embryonic survival after transferring embryos retrieved from donor cows was greater on Days 31 (36.0 vs. 30.7%; P = 0.001) and 45 (28.3 vs. 23.1%; P = 0.001) of pregnancy when compared with embryos from donor heifers. In conclusion, MO embryo production efficiency decreased during the hot seasons both in cows and heifers; however, the decline was more pronounced in donor cows. Regardless of the embryo source, similar pregnancy rate was observed in the recipient that received embryos produced during the hot and cooler seasons. Curiously, embryos originating from donor cows had higher embryonic survival when transferred to recipient cows than embryos originating from heifers.
本研究调查了荷斯坦奶牛供体类别（母牛与小母牛）和气候变化（炎热季节与凉爽季节）对体内胚胎生产程序效率以及胚胎移植到荷斯坦受体母牛后的存活率的影响。对两个奶牛场进行的总共1562次多次排卵（MO）程序（母牛：n = 609，小母牛：n = 953）和4076次胚胎移植（ET）进行了评估。与供体小母牛相比，供体母牛的黄体数量更多（10.6±0.6对7.5±0.4；P<0.0001），回收的卵子/胚胎数量更多（7.6±0.6对4.6±0.4；P<0.0001）。然而，供体母牛的受精率（47.9%对82.4%；P<0.0001）和可移植胚胎比例（31.5%对67.4%；P<0.0001）分别低于小母牛。无论供体类别如何，炎热季节可冷冻胚胎的比例低于凉爽季节（21.4%对32.8%；P<0.001）。然而，与小母牛（46.2%对38.1%；P = 0.01）相比，母牛在炎热季节可冷冻胚胎比例的下降幅度更大（21.7%对10.7%）。相比之下，胚胎生产季节（炎热或凉爽）对妊娠第31天（30.5%对31.7%；P = 0.45）和第45天（25.3%对25.1%；P = 0.64）的妊娠率没有影响。无论胚胎生产季节如何，与来自供体小母牛的胚胎相比，移植从供体母牛回收的胚胎后，妊娠第31天（36.0%对30.7%；P = 0.001）和第45天（28.3%对23.1%；P = 0.001）的胚胎存活率更高。总之，母牛和小母牛在炎热季节的MO胚胎生产效率均下降；然而，供体母牛的下降更为明显。无论胚胎来源如何，接受在炎热季节和凉爽季节生产的胚胎的受体母牛的妊娠率相似。奇怪的是，移植到受体母牛时，来自供体母牛的胚胎比来自小母牛的胚胎具有更高的胚胎存活率。
