下临床乳腺炎在新鲜小牛(FCH)中很常见,但牧群之间的患病率不同,可能是由于危险因素的变化。这项观察性研究的目的是根据泌乳早期的母牛SCC(CSCC),确定有良好或不良好的第一胎次乳房健康的牧群之间IMI发生的差异,并研究对乳房健康很重要的动物因素的群体差异,例如乳房和肺部皮肤损伤以及动物清洁度。包括三组牧群,那些具有高比例的FCH和低(≤75,000细胞/ml)CSCC在产牛后的前2个牛奶记录(LL),FCH比例高的群体,在第一次记录时具有高(>100,000个细胞/ml)CSCC,在第二次记录时具有低CSCC(HL),在两种记录(HH)中,FCH比例高,CSCC高。31群(13LL,11HL,15HH)在12个月内进行了3次访问,以观察清洁度和飞节病变,并使用牛奶喂养的小牛的拭子布取样乳房/乳头皮肤,早期怀孕的小母牛和晚期怀孕的小母牛。在25(9LL,9HL,7HH)在产牛后的第3-4天,从初乳和牛奶中获取乳房四分之一样本,由FCH的农民在一年内采取。农民还提供了关于产牛(个人或群体)的信息,在挤奶时使用约束和催产素,以及乳头和乳房皮肤损伤的存在。通过培养研究拭子样品和四分之一样品中的细菌生长,并使用全基因组测序(WGS)对分离株进行基因分型。清洁度,除乳房大腿皮炎外的胸部和乳房皮肤病变,草组之间的拭子样本中细菌的生长没有差异。更常见的是来自LL群的FCH,与HH和HL牛群的FCH相比,产于一群动物中。LL牛群比HH牛群在挤奶时使用约束更为普遍,而LL牛群中乳房大腿皮炎的发生率最低。在722个FCH的5,593个季度样本中,有14%发现了特异性感染。最常见的IMI是S.chimgenes。模拟链球菌的生长在HH中比在LL和HL牛群中更常见。在初乳样本中,溶血链球菌在HL和HH中比在LL牛群中更常见。在两个采样中,具有相同特异性感染的四分之一的比例在HH中高于LL牧群,而在HH中往往高于HL牧群。在两个采样中,具有S.chimgenesIMI的四分之一的比例在牧群之间趋于不同,并且在HH牧群中最高。WGS在几乎所有区域中的两个样品中发现了相同序列类型的S.染色体基因和金黄色葡萄球菌,在两个样品中具有相同的感染。牧群之间IMI的差异与HH牧群较高的SCC一致。嗜色链球菌IMI在FCH中占优势的原因需要进一步研究。
Subclinical mastitis can be common among freshly calved heifers (FCH), but the prevalence differs between herds, possibly due to variation in risk factors. The aims of this observational study were to identify differences in occurrence of intramammary infection (IMI) in FCH between herds with documented good or poorer first-parity udder health based on cow somatic cell count (CSCC) in early lactation, and to study herd differences in animal factors important for udder health, such as udder and hock skin lesions and animal cleanliness. Three groups of herds were included: those with high proportions of FCH with low CSCC (≤75,000 cells/mL) at the first 2 milk recordings after calving (LL), herds with high proportions of FCH with high CSCC (>100,000 cells/mL) at the first and low CSCC at the second recording (HL), and herds with high proportions of FCH with high CSCC at both recordings (HH). Thirty-nine herds (13 LL, 11 HL, 15 HH) were visited 3 times during a 12-mo period for observation of cleanliness and hock lesions, and sampling of udder and teat skin using swab cloths of milk-fed calves, early-pregnant heifers, and late-pregnant heifers. In 25 (9 LL, 9 HL, 7 HH) udder quarter samples from colostrum and milk on d 3 to 4 after calving were taken by the farmers from FCH during one year. The farmers also provided information on calving (individual or group), use of restraint and oxytocin at milking, and presence of teat and udder skin lesions. Bacterial growth in swab samples and quarter samples was investigated by culturing, and a selection of isolates was genotyped using whole-genome sequencing. Cleanliness, hock and udder skin lesions other than udder-thigh dermatitis, and growth of bacteria in swab samples did not differ between herd groups. It was more common that FCH from LL herds, compared with FCH in HH and HL herds, calved in a group of animals. Use of restraint at milking was more common in LL herds than in HH herds, whereas presence of udder-thigh dermatitis was lowest in LL herds. Specific infection was found in 14% of 5,593 quarter samples from 722 FCH. The most common IMI was Staphylococcus chromogenes. Growth of Staphylococcus simulans was more common in HH than in LL and HL herds. In colostrum samples, Staphylococcus haemolyticus was more common in HL and HH than in LL herds. The proportion of quarters with the same specific infection at both samplings was higher in HH than in LL herds and tended to be higher in HH than in HL herds. The proportion of quarters with Staph. chromogenes IMI at both samplings tended to differ between herd groups and was highest in HH herds. Whole-genome sequencing found the same sequence type of Staph. chromogenes and Staphylococcus aureus in both samples in almost all quarters with the same infection at both samplings. The differences in IMI between herd groups were in line with the higher somatic cell count in HH herds. The reasons for the predominance of Staph. chromogenes IMI in FCH need further studies.