Facultad de Ciencias Veterinarias, Universidad Nacional del Litoral, Kreder 2805, Esperanza 3080, Santa Fe, Argentina.
Instituto de Investigación de la Cadena Láctea (IDICaL, INTA-CONICET) - EEA Rafaela INTA, Ruta Nacional 34 Km 227, Rafaela 2300, Santa Fe, Argentina.
J Dairy Res. 2024 Feb;91(1):76-82. doi: 10.1017/S0022029924000219. Epub 2024 Apr 19.
The aim of this study was to compare the effects of feeding pasteurized waste milk or saleable milk to calves on weight, health and emergence of antimicrobial resistance in strains isolated from those calves. An experimental study under field conditions on a commercial pasture-based Argentinian dairy farm was carried out. Forty Holstein calves were assigned randomly to either pasteurized waste milk (PWM) or non-pasteurized saleable milk (SM). The antimicrobial agents (AM) used on the farm, both to treat or prevent diseases, were recorded. The passive immunity level, calf live weight, AM presence in milk, clinical examination of calves, and isolation and identification, were performed. A total of 258 strains were isolated from fecal samples (132 isolates from SM calves and 126 from PWM calves at six sampling times). All isolated were used to perform AM susceptibility tests (disc diffusion and agar dilution). No differences were observed between groups in health parameters, average daily gain or prevalence of resistant strains to any AM evaluated throughout the study. Peaks of trimethoprim, sulfamethoxazole and enrofloxacin minimum inhibitory concentration (MIC) were observed at 30 d in from both groups of calves, whilst additional peaks to tetracyclin and ampicillin were observed only in SM calves. All MIC apart from gentamicin decreased at 75 and 90 d of age (during the weaning period). Gentamicin MIC behaved differently, having no peaks and increasing at 90 d only in PWM group. In conclusion, we found no evidence that emergence of antibiotic resistance is related to the consumption of pasteurized waste milk.
本研究旨在比较给犊牛喂食巴氏消毒废奶或商品奶对其体重、健康和从这些犊牛中分离的菌株出现抗药性的影响。在阿根廷一家商业牧场奶牛场进行了现场条件下的实验研究。40 头荷斯坦犊牛被随机分配到巴氏消毒废奶（PWM）或未经巴氏消毒的商品奶（SM）组。记录了农场使用的抗生素（AM），包括用于治疗或预防疾病的抗生素。进行了被动免疫水平、犊牛活体重、牛奶中 AM 的存在、犊牛临床检查以及分离和鉴定。从粪便样本中总共分离出 258 株 （SM 犊牛 132 株，PWM 犊牛 126 株，在 6 个采样时间）。所有分离株均用于进行 AM 药敏试验（药敏纸片扩散法和琼脂稀释法）。在整个研究过程中，未观察到两组在健康参数、平均日增重或任何 AM 耐药菌株的流行率方面存在差异。在第 30 天，两组犊牛的 trimethoprim、sulfamethoxazole 和 enrofloxacin 最小抑菌浓度（MIC）均出现峰值，而仅在 SM 犊牛中观察到 tetracyclin 和 ampicillin 的额外峰值。除庆大霉素外，所有 MIC 在 75 和 90 日龄（断奶期）时均降低。庆大霉素 MIC 的行为不同，仅在 PWM 组中在 90 日龄时出现峰值并增加。总之，我们没有发现抗药性出现与食用巴氏消毒废奶有关的证据。
