Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, T6G 2P5, Canada.
Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, T6G 2P5, Canada; Department of Large Animal Clinical Sciences, University of Saskatchewan, Saskatoon, S7N 5B4, Canada.
Theriogenology. 2023 Jan 1;195:249-256. doi: 10.1016/j.theriogenology.2022.10.036. Epub 2022 Nov 3.
To understand the mechanisms underlying the inverse relationship between anogenital distance (AGD) and fertility in dairy cattle, we determined if embryo yield and quality differed between cattle of short- and long-AGD (Study 1), and whether anti-Müllerian hormone (AMH), antral follicle count (AFC) and superovulation responses differed by AGD group (Study 2). In Study 1, records of embryo yield and quality in Holstein heifers (n = 43) and cows (n = 14) from two commercial dairy herds were analyzed, retrospectively. Short- and long-AGD groups were based on the median AGD cut-points of 113 and 134 mm, for heifers and cows, respectively. The mean numbers of total (7.4 vs. 9.0; 9.4 vs.12.9), fertilized ova (5.6 vs. 6.2; 6.6 vs. 6.9), and viable embryos (4.4 vs. 4.8; 5.9 vs. 5.3) per heifer and cow did not differ between cattle of short vs. long AGD. Short-AGD cows, however, had greater proportions of fertilized ova (69.7 vs. 53.3%; P = 0.07) and viable embryos (62.1 vs. 41.1%; P = 0.03) than long-AGD cows. The odds of short-AGD cows yielding fertilized ova and viable embryos were 2.0 and 4.0 times greater, respectively, than the odds of long-AGD cows. In Study 2, lactating cows (n = 24) of a research herd had their AGD categorized as in Study 1, and AFC, AMH, and superovulation responses (i.e., no. of preovulatory follicles [≥ 10 mm] and CL) were determined. Mean AFC (27 ± 4.5 vs. 21 ± 4.0) and CL (9 ± 1.6 vs. 7 ± 1.4) per cow did not differ between short- and long-AGD groups. Serum AMH concentration (pg/mL) was lesser in short-AGD cows compared with long-AGD cows (114 ± 30.4 vs. 200 ± 26.8; P = 0.05), but the no. of preovulatory follicles was greater (15 ± 1.9 vs. 8 ± 1.7; P = 0.01) in short-AGD than in long-AGD cows. The overall proportion of follicles ≥10 mm was also greater in short-AGD cows than in long-AGD cows (56 vs 44%; P = 0.03). Preovulatory follicle number was affected by a parity x AGD group interaction (P = 0.04), with multiparous short-AGD cows accounting for the largest number of follicles. No associations were found among AGD, AFC and AMH. The associations between AFC and superovulation responses (follicles: r = 0.67, and CL: 0.58; P < 0.01) were moderate but AMH was not associated with superovulation responses. In summary, whereas AGD-associated differences in the yield and quality of embryos were not evident in heifers, the proportions of fertilized ova and viable embryos were greater in short-AGD than in long-AGD cows. In addition, the proportion of preovulatory follicles, an indicator of superovulatory response, was greater in short-AGD cows than in long-AGD cows.
为了理解牛的肛殖距（AGD）与生育率之间的反比关系的机制，我们确定了在短 AGD 和长 AGD 的牛之间（研究 1），以及在抗苗勒管激素（AMH）、窦卵泡计数（AFC）和超数排卵反应之间是否存在差异（研究 2）。在研究 1 中，我们分析了两个商业奶牛场的荷斯坦小母牛（n=43）和奶牛（n=14）的胚胎产量和质量的记录，是回顾性的。短 AGD 和长 AGD 组分别基于小母牛和奶牛的中位数 AGD 切点 113 和 134mm。小母牛和奶牛的总卵子数（7.4 对 9.0；9.4 对 12.9）、受精卵（5.6 对 6.2；6.6 对 6.9）和可存活胚胎（4.4 对 4.8；5.9 对 5.3）的数量在短 AGD 牛和长 AGD 牛之间没有差异。然而，短 AGD 奶牛的受精卵（69.7%对 53.3%；P=0.07）和可存活胚胎（62.1%对 41.1%；P=0.03）的比例大于长 AGD 奶牛。短 AGD 奶牛产生受精卵和可存活胚胎的可能性分别是长 AGD 奶牛的 2.0 和 4.0 倍。在研究 2 中，研究牛场的泌乳奶牛（n=24）按照研究 1 进行 AGD 分类，同时确定 AFC、AMH 和超数排卵反应（即，促卵泡素≥10mm 的卵泡数量和黄体）。短 AGD 和长 AGD 组的每头奶牛的 AFC（27±4.5 对 21±4.0）和 CL（9±1.6 对 7±1.4）没有差异。短 AGD 奶牛的血清 AMH 浓度（pg/mL）比长 AGD 奶牛低（114±30.4 对 200±26.8；P=0.05），但短 AGD 奶牛的促卵泡素≥10mm 的卵泡数量更多（15±1.9 对 8±1.7；P=0.01）。短 AGD 奶牛的≥10mm 卵泡比例也高于长 AGD 奶牛（56%对 44%；P=0.03）。促卵泡素≥10mm 的卵泡数量受到胎次×AGD 组相互作用的影响（P=0.04），多胎短 AGD 奶牛的卵泡数量最多。AGD、AFC 和 AMH 之间没有关联。AGD 与 AFC 和 AMH 之间没有关联。AFC 和超数排卵反应（卵泡：r=0.67，CL：0.58；P<0.01）之间的关联是中度的，但 AMH 与超数排卵反应没有关联。总之，虽然在小母牛中，AGD 相关的胚胎产量和质量差异并不明显，但短 AGD 奶牛的受精卵和可存活胚胎的比例大于长 AGD 奶牛。此外，短 AGD 奶牛的促卵泡素≥10mm 的卵泡数量比例大于长 AGD 奶牛。
