In vitro sperm characteristics and in vivo fertility of sex-sorted and conventional semen in suckled Nelore cows at a traditional schedule for timed-AI with estrus detection

ABSTRACT The aim of this study was to assess in vitro sperm characteristics and pregnancies/AI (P/AI) of conventional and sex-sorted semen at timed-AI of suckled, multiparous Nelore cows. All cows (n=348) were submitted to a traditional estradiol/progesterone(P4)-based protocol. At 48h after P4-device removal, the estrous behavior was recorded, and AI was performed with conventional or sex-sorted semen from two bulls. The following sperm assessments were performed: CASA, Hyposmotic Test, sperm morphometry and chromatin structure by TB staining. P/AI were reduced (P<0.001) for sex-sorted compared to conventional semen in cows expressing estrus (27vs47%) or not (11vs.37%). Membrane integrity (Bull1: 30.3±9.6 vs. 52.3±12.4%, P=0.01; Bull2: 24.5±3.0 vs. 48.7±1.6%, P=0.006) and sperm concentration (Bull1: 23.2±0.6 vs. 43.0±0.8x10⁶sperm/mL, P<0.001; Bull2: 25.1±2.8 vs. 42.1±0.7x10⁶sperm/mL; P<0.001) were reduced in sex-sorted compared to conventional semen, for both bulls. Total and progressive motility were reduced in sex-sorted semen for Bull1 (TM: 49.7±15.9 vs. 94.9±1.9%, P=0.007; PM: 16.7±3.4 vs. 44.1±13.2%, P=0.009) and no differences were detected for Bull2 (TM: 45.0±17.5 vs. 68.2±19.1%, P=0.098; PM: 12.8±4.7 vs. 30.0±13.0%, P=0.065). Sperm ellipticity from sex-sorted was lower than conventional semen for Bull2 (0.306±0.01 vs. 0.342±0.02, P=0.02) and no difference was detected for Bull1 (0.332±0.01 vs. 0.330±0.01, P=0.55). Reduced in vivo fertility was observed for sex-sorted semen, regardless of estrous behavior. In vitro sperm quality of sex-sorted semen was compromised for both bulls, but differently affected for each sire.

摘要 本研究旨在评估泌乳经产奈洛尔牛（Nelore）在定时人工授精（timed-AI）时，使用常规精液与性别分选精液的体外精子特性及妊娠率/人工授精率（P/AI）。所有受试母牛（n=348）均采用基于雌二醇/孕酮（P4）的传统发情调控方案。在孕酮阴道栓取出后48小时，记录受试母牛的发情行为，并分别使用两头种公牛的常规精液或性别分选精液开展人工授精。后续开展了以下精子检测项目：计算机辅助精子分析（CASA）、低渗肿胀试验（Hyposmotic Test）、精子形态学检测，以及台盼蓝（TB）染色检测染色质结构。相较于常规精液，使用性别分选精液的受试母牛，无论是否表现出发情行为，其P/AI均显著降低（P<0.001）：发情母牛的P/AI分别为27% vs 47%，未发情母牛则为11% vs 37%。两头种公牛的性别分选精液的膜完整性（种公牛1：30.3±9.6% vs 52.3±12.4%，P=0.01；种公牛2：24.5±3.0% vs 48.7±1.6%，P=0.006）与精子浓度（种公牛1：23.2±0.6 vs 43.0±0.8×10⁶精子/mL，P<0.001；种公牛2：25.1±2.8 vs 42.1±0.7×10⁶精子/mL，P<0.001）均显著低于常规精液。种公牛1的性别分选精液的总活力（TM）与前向运动活力（PM）均显著降低（TM：49.7±15.9% vs 94.9±1.9%，P=0.007；PM：16.7±3.4% vs 44.1±13.2%，P=0.009），而种公牛2的两种精液的总活力与前向运动活力则无显著差异（TM：45.0±17.5% vs 68.2±19.1%，P=0.098；PM：12.8±4.7% vs 30.0±13.0%，P=0.065）。种公牛2的性别分选精液的精子椭圆率显著低于常规精液（0.306±0.01 vs 0.342±0.02，P=0.02），而种公牛1的两种精液的精子椭圆率无显著差异（0.332±0.01 vs 0.330±0.01，P=0.55）。无论受试母牛是否表现出发情行为，使用性别分选精液均会降低体内受精能力。两头种公牛的性别分选精液的体外精子质量均受损，但不同种公牛的受损程度存在差异。