Faculty of Veterinary Medicine, Department of Production Animal Clinical Sciences, Norwegian University of Life Sciences, 1432 Ås, Norway.
Department of Animal and Aquacultural Sciences, Faculty of Biosciences, Norwegian University of Life Sciences, 1432 Ås, Norway; Geno Breeding and AI Association, 2317 Hamar, Norway.
J Dairy Sci. 2022 Jul;105(7):5946-5953. doi: 10.3168/jds.2021-21752. Epub 2022 May 5.
Subclinical endometritis (SCE) is highly prevalent in dairy cows, causing negative effects on reproductive outcomes and the producer economy. Genetic selection for animals with better resilience against uterine disease should be prioritized due to both sustainability and animal welfare. Therefore, the aim of the present study was to estimate the heritability of SCE in the Norwegian Red (NR) population. Moreover, future perspectives of the condition as a fertility phenotype for breeding are discussed. A total of 1,642 NR cows were sampled for SCE at the time of artificial insemination, using cytotape. The percentage of polymorphonuclear cells (PMN) in each sample was established by cytology, through the counting of 300 PMN and epithelial cells. The mean percentage of PMN was 5%. Different trait definitions were examined, and SCE was defined as binary traits, based on the following cut-off levels of PMN: Cyto0 = PMN >0, Cyto3 = PMN >3%, Cyto5 = PMN >5%, Cyto10 = PMN >10%, and Cyto20 = PMN >20%. The mean ranged from 0.07 (Cyto20) to 0.59 (Cyto0). We also analyzed PMN as a continuous variable using percent PMN. Information on the animals and herds was obtained from the Norwegian Dairy Herd Recording System. The pedigree of cows with data included a total of 24,066 animals. A linear animal model was used to estimate the heritability. The only trait definition that had an estimated genetic variance larger than the standard error was Cyto5, with an estimated heritability of 0.04. For all other definitions, the genetic variance was not significantly different from zero. A cut-off level of 5% PMN has been established as a general threshold for the definition of SCE in earlier literature. The standard errors of the estimated variance components were relatively large, and results should be interpreted with caution. However, the current study indicates that SCE is heritable at a similar level to that of clinical endometritis and metritis, and has potential as a future fertility phenotype to be used for breeding purposes. A more feasible method to diagnose SCE is needed to establish larger data sets.
奶牛亚临床子宫内膜炎（SCE）发病率较高，对繁殖性能和养殖经济效益有负面影响。由于可持续性和动物福利的原因，应优先对具有更好子宫疾病抗性的动物进行遗传选择。因此，本研究旨在估计挪威红牛（NR）群体中 SCE 的遗传力。此外，还讨论了将其作为一种繁殖力表型的未来前景。共对 1642 头 NR 奶牛进行了人工授精时的 SCE 采样，使用 cytotape。通过对 300 个PMN 和上皮细胞进行计数，用细胞学确定每个样本中多形核细胞（PMN）的百分比。PMN 的平均百分比为 5%。检查了不同的性状定义，基于以下PMN 截断水平将 SCE 定义为二项性状：Cyto0 = PMN＞0，Cyto3 = PMN＞3%，Cyto5 = PMN＞5%，Cyto10 = PMN＞10%和 Cyto20 = PMN＞20%。均值范围从 0.07（Cyto20）到 0.59（Cyto0）。我们还使用PMN%分析了PMN 作为连续变量。动物和畜群的信息从挪威奶牛群记录系统中获得。包含数据的奶牛的系谱共有 24066 头动物。使用线性动物模型估计遗传力。只有 Cyto5 的性状定义具有大于标准误差的估计遗传方差，其遗传力为 0.04。对于所有其他定义，遗传方差与零没有显著差异。5%PMN 已被确立为早期文献中 SCE 定义的一般阈值。估计方差分量的标准误差相对较大，结果应谨慎解释。然而，本研究表明 SCE 的遗传力与临床子宫内膜炎和子宫炎相似，具有作为未来繁殖力表型用于繁殖目的的潜力。需要一种更可行的方法来诊断 SCE，以建立更大的数据集。
