Peckler Gretchen L, Fuenzalida Maria Jose, Aulik Nicole, Adcock Sarah J J
Department of Animal and Dairy Sciences, University of Wisconsin, Madison, WI, USA53706.
Department of Animal and Food Sciences, University of Wisconsin, River Falls, WI, USA54022.
J Anim Sci. 2024 Jan 3;102. doi: 10.1093/jas/skae375.
Subclinical mastitis, the asymptomatic inflammation of the udder often caused by bacterial infection, is an important economic and welfare concern in meat-producing flocks. We conducted a longitudinal observational study to: (1) characterize the etiology, prevalence, incidence, and persistence of intramammary infections during the first 8 wk of lactation, and (2) investigate the potential risk factors of lactation stage, parity, and the number of lambs reared. Duplicate milk samples (n = 592) were collected aseptically from each udder half of 37 clinically healthy ewes (9 Hampshire, 22 Polypay, and 6 Targhee) weekly for their first 8 wk of lactation. A sample was considered a true infection if at least 100 CFU/mL of a bacterial species were isolated. Out of a total of 560 non-contaminated duplicate udder half samples, 186 (33.2%) were infected. The prevalence of subclinical mastitis in the first week of lactation was 26.0% at the udder half level and increased over lactation to 47.1% by 8 wk. Over the course of lactation, 34 of the 37 (91.9%) ewes had an intramammary infection in at least one udder half. The most common bacteria isolated were non-aureus Staphylococci (72.1%), Staphylococcus aureus (7.5%), and Mannheimia haemolytica (5.9%). The weekly incidence rate of new infections was 18.0% ± 10.2% (mean ± SD). Infections lasted 2.1 ± 2.1 wk, with 9.0% present the full 8 wk of observation. Spontaneous cures occurred in 36.0% of infection bouts but varied from 0% to 100% depending on the pathogen. The probability of subclinical mastitis infection increased as lactation progressed for ewes rearing single or multiple lambs and for ewes in their first or second parity, but not for ewes in later parities. In conclusion, intramammary infections in this flock were prevalent across lactation, parities, and litter sizes, and varied in their duration and spontaneous cure rate. Improved knowledge of the etiological agents and risk factors involved in subclinical mastitis is important in developing effective control measures in meat-producing flocks.
亚临床型乳腺炎是乳房的无症状炎症，通常由细菌感染引起，是肉用羊群中一个重要的经济和福利问题。我们进行了一项纵向观察研究，目的是：（1）描述泌乳前8周内乳房内感染的病因、患病率、发病率和持续时间，以及（2）调查泌乳阶段、胎次和所哺育羔羊数量的潜在风险因素。在37只临床健康母羊（9只汉普郡羊、22只波利佩羊和6只塔尔基羊）泌乳的前8周，每周从每只母羊的每个乳房半侧无菌采集两份乳样（n = 592）。如果分离出至少100 CFU/mL的某一细菌种类，则该样本被视为真正感染。在总共560份未受污染的乳房半侧重复样本中，186份（33.2%）被感染。泌乳第一周亚临床型乳腺炎在乳房半侧水平的患病率为26.0%，在整个泌乳期增加，到8周时升至47.1%。在整个泌乳过程中，37只母羊中有34只（91.9%）至少有一个乳房半侧发生乳房内感染。分离出的最常见细菌是非金黄色葡萄球菌（72.1%）、金黄色葡萄球菌（7.5%）和溶血曼氏杆菌（5.9%）。新感染的每周发病率为18.0%±10.2%（平均值±标准差）。感染持续2.1±2.1周，9.0%的感染在整个8周观察期内持续存在。36.0%的感染发作出现自愈，但因病原体不同而从0%到100%不等。对于哺育单只或多只羔羊的母羊以及头胎或二胎母羊，亚临床型乳腺炎感染的概率随着泌乳进展而增加，但经产母羊则不然。总之，该羊群中的乳房内感染在整个泌乳期、胎次和产羔数中普遍存在，其持续时间和自愈率各不相同。了解亚临床型乳腺炎的病原体和风险因素对于制定肉用羊群的有效控制措施很重要。
