Search

Objectives: To characterize putative AmpC-hyperproducing third-generation cephalosporin-resistant E. coli from dairy farms and their phylogenetic relationships; to identify risk factors for their presence; and to assess evidence for their zoonotic transmission into the local human population.Methods: Proteomics was used to explain differences in antimicrobial susceptibility. WGS allowed phylogenetic analysis. Multilevel, multivariable logistic regression modelling was used to identify risk factors.Results: Increased use of amoxicillin/clavulanate was associated with an increased risk of finding AmpC hyperproducers on farms. Expansion of cephalosporin resistance in AmpC hyperproducers was seen in farm isolates with marR mutations (conferring cefoperazone resistance) or when AmpC was mutated (conferring fourth-generation cephalosporin and cefoperazone resistance). Phylogenetic analysis confirmed the dominance of ST88 amongst farm AmpC hyperproducers but there was no evidence for acquisition of farm isolates by members of the local human population.Conclusions: Clear evidence was found for recent farm-to-farm transmission of AmpC-hyperproducing E. coli and of adaptive mutations to expand resistance. Whilst there was no evidence of isolates entering the local human population, efforts to reduce third-generation cephalosporin resistance on dairy farms must address the high prevalence of AmpC hyperproducers. The finding that amoxicillin/clavulanate use was associated with an increased risk of finding AmpC hyperproducers is important because this is not currently categorized as a highest-priority critically important antimicrobial and so is not currently targeted for specific usage restrictions in the UK. [ABSTRACT FROM AUTHOR]

Sub-optimal heifer growth is associated with higher disease rates and reduced future performance and longevity in the dairy herd. This report describes a system for measuring heifer growth from birth to first calving that was used on commercial dairy farms in South West England, in order to gather benchmarking data to feed back to farmers. Weights ( n  = 8443) were collected from 20 farms. There was a marked variation in individual and herd mean growth rates. Overall, calves gained no weight in the first 8 days after birth and had a very low growth rate (median 0.12 kg/day) up to 30 days, a period when feed conversion efficiency is high and calves are vulnerable to disease. Heifers whose growth rate up to 180 days was low were significantly less likely to achieve target service weight (374 kg) by 420 days. Monitoring heifer growth during the rearing period enables farmers to improve heifer growth rates and so impact both the efficiency of heifer rearing and, potentially, the productivity and performance of the adult herd. [ABSTRACT FROM AUTHOR]