The main aim of this study was to assess the associations between the timing of lameness clinical case occurrence in lactation with productive and reproductive performances in grazing Holstein cows. A cohort study was carried out on a dataset with records from a commercial dairy herd (Buenos Aires, Argentina) for cows that calved and were dried off from January 2010 through June 2017. The first recorded event of lameness per lactation was considered for the study. Criteria for lactation inclusion included not having uterine diseases, mastitis, or anovulatory cysts during the studied risk period (i.e., up to 200 DIM). Therefore, a total of 7156 out of 20,086 lactations were included in the statistical analysis. The association between lameness case occurrence in lactation (cows not lame (LG0) vs. lame cows between parturition and first service (LG1) vs. lame cows between first service and first pregnancy (LG2)) with productive (i.e., accumulated milk yield to 150 DIM (MILK150) and 300 DIM (MILK305)) and reproductive performances (hazard of insemination and pregnancy) was analyzed with linear regression models and proportional hazard regression models, respectively. Lame cows produced 161 and 183 kg less MILK150 and MILK305 than non-lame herd mates, respectively. Moreover, LG1 cows produced 216 kg less MILK150 and 200 kg less MILK305 than LG0 cows, and LG2 cows also produced 58 kg less MILK150 and 158 kg less MILK305 than LG0 cows. The LG1 cows had a lower hazard of service than LG0 cows (HR = 0.43, 95%CI = 0.39–0.47). Furthermore, LG1 cows had a lower hazard of pregnancy than LG0 cows (HR = 0.52, 95%CI = 0.46–0.59) and took longer to get pregnant than LG0 cows (median [95%CI], 139 [132–144] vs. 101 [99–103]). Moreover, LG2 cows had a much lower hazard of pregnancy than LG0 cows (HR = 0.08, 95%CI = 0.05–0.12) and much longer calving to first pregnancy interval than LG0 cows (188 [183–196] vs. 101 [99–103]). In conclusion, cows that become lame in early lactation produce less milk and have lower hazards of insemination and pregnancy than herd mates that are healthy or become lame later in lactation. In addition, cows that become lame immediately after the voluntarily waiting period have the poorest reproductive performance (i.e., they have the lowest hazard of pregnancy and the longest calving to pregnancy interval).

中文翻译：

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泌乳早期跛行与一群补充性放牧奶牛的较低生产和繁殖性能有关

本研究的主要目的是评估泌乳期跛行临床病例发生时间与放牧荷斯坦奶牛的生产和繁殖性能之间的关联。对一个数据集进行了队列研究，该数据集记录了商业奶牛群（阿根廷布宜诺斯艾利斯）在 2010 年 1 月至 2017 年 6 月期间产犊和晒干的奶牛。本研究考虑了首次记录的每次泌乳跛行事件. 哺乳期纳入的标准包括在研究的风险期间（即高达 200 DIM）没有子宫疾病、乳腺炎或无排卵囊肿。因此，20,086 次哺乳中总共有 7156 次被纳入统计分析。哺乳期跛行病例发生率（奶牛不跛行 (LG0) 与不跛行之间的关联）生产（即累积产奶量达到 150 DIM (MILK150) 和 300 DIM (MILK305)）和繁殖性能（危害分别用线性回归模型和比例风险回归模型分析了受精和妊娠的影响。跛行母牛比非跛足的牛群产生的 MILK150 和 MILK305 分别少 161 公斤和 183 公斤。此外，LG1 奶牛比 LG0 奶牛少生产 216 公斤 MILK150 和 200 公斤 MILK305，而 LG2 奶牛也比 LG0 奶牛少生产 58 公斤 MILK150 和 158 公斤 MILK305。LG1 奶牛的服务风险低于 LG0 奶牛（HR = 0.43，95%CI = 0.39–0.47）。此外，LG1 奶牛的妊娠风险低于 LG0 奶牛（HR = 0.52，95%CI = 0.46–0. 59) 并且比 LG0 奶牛需要更长的时间才能怀孕（中位数 [95% CI]，139 [132-144] vs. 101 [99-103]）。此外，与 LG0 奶牛相比，LG2 奶牛的怀孕风险要低得多（HR = 0.08，95%CI = 0.05-0.12），并且比 LG0 奶牛产犊到第一次怀孕的间隔要长得多（188 [183-196] vs. 101 [99]） –103]）。总之，与健康或在泌乳后期跛行的牛群相比，在泌乳早期跛行的奶牛产奶量更少，受精和怀孕的风险也更低。此外，在自愿等待期后立即跛行的母牛繁殖性能最差（即，它们的妊娠风险最低，产犊至妊娠间隔最长）。LG2 奶牛的妊娠风险比 LG0 奶牛低得多（HR = 0.08，95%CI = 0.05-0.12），并且比 LG0 奶牛产犊到第一次怀孕的间隔要长得多（188 [183-196] vs. 101 [99-103]） ]）。总之，与健康或在泌乳后期跛行的牛群相比，在泌乳早期跛行的奶牛产奶量更少，受精和怀孕的风险也更低。此外，在自愿等待期后立即跛行的母牛繁殖性能最差（即，它们的妊娠风险最低，产犊至妊娠间隔最长）。LG2 奶牛的妊娠风险比 LG0 奶牛低得多（HR = 0.08，95%CI = 0.05-0.12），并且比 LG0 奶牛产犊到第一次怀孕的间隔要长得多（188 [183-196] vs. 101 [99-103]） ]）。总之，与健康或在泌乳后期跛行的牛群相比，在泌乳早期跛行的奶牛产奶量更少，受精和怀孕的风险也更低。此外，在自愿等待期后立即跛行的母牛繁殖性能最差（即，它们的妊娠风险最低，产犊至妊娠间隔最长）。与健康或在泌乳后期跛行的牛群相比，在泌乳早期跛行的奶牛产奶量较少，受精和怀孕的风险也较低。此外，在自愿等待期后立即跛行的母牛繁殖性能最差（即，它们的妊娠风险最低，产犊至妊娠间隔最长）。与健康或在泌乳后期跛行的牛群相比，在泌乳早期跛行的奶牛产奶量较少，受精和怀孕的风险也较低。此外，在自愿等待期后立即跛行的母牛繁殖性能最差（即，它们的妊娠风险最低，产犊至妊娠间隔最长）。