The aim of the study was to investigate the impact of the implementation of new health traits into the breeding objective and selection criteria for Czech Holstein cows on the genetic selection response in the breeding objective traits. Incidence of overall claw diseases was included into the current breeding objective for cows (11 traits together). Three traits that indicated claw health (incidence of claw diseases overall and infectious and non-infectious claw diseases) and incidence of clinical mastitis were successively added to the current selection criteria in a cow selection index (a maximum of 19 traits). Selection responses in the breeding objective traits were estimated by applying the general principles of the selection index theory. The required genetic variances for the new traits, the economic weights for all breeding objective traits and the genetic correlations among the selection index traits were estimated within this study. The marginal economic weights, which were calculated for two-year-old cows by applying a bioeconomic model with implemented gene flow, were -193 and -168 € per case for clinical mastitis and overall claw disease incidence, respectively. Using the comprehensive selection index with 19 traits, the reduction in the incidence of both udder and claw diseases was calculated to be 0.004 cases per cow per year. At the same time, a more favourable genetic selection response was obtained for other functional traits, e.g., +0.020% for cow conception rate and +0.010 years for productive life of cow (which represented the profit of 67 € and 367 € per herd and per year, respectively) when compared to the current index. Based on this study, a direct selection of cows for claw and udder health is nowadays recommended to improve the health status of herds and economics in production systems.
Cases of mastitis (CM) from 38,236 lactations belonging to 16,497 cows were recorded on seven farms in the Czech Republic from 1996 to 2014. Clinical mastitis was analyzed with linear animal model as an all-or-none trait for each recorded lactation (CM305) and separately for each trimester of lactation (CM1, CM2, and CM3). Bivariate linear animal models were used to estimate the genetic correlation between these CM traits and lactation means for somatic cell score (SCS305), the interval between calving and first insemination (INT) and days open (DO). Factors included in the linear model were parity, herd, year of calving, calving season, fixed linear and quadratic regression on age at first calving, fixed linear and quadratic regression on milk production in the corresponding parity, permanent environmental effect of the cow, and additive genetic effect of the cow. Estimated heritabilities of the CM traits ranged from 0.01 to 0.03. Permanent environmental effects accounted for approximately two-thirds of the phenotypic variance. Genetic correlations of SCS305 with CM traits were 0.85±0.029, 0.81±0.086, 0.82±0.087, and 0.67±0.088 for CM305, CM1, CM2, and CM3, respectively. Genetic correlations of INT with CM305, CM1, CM2, and CM3, respectively, were 0.22±0.065, 0.19±0.084, 0.20±0.121 and 0.15±0.121: and genetic correlations of DO and the four CM traits were 0.28±0.079, 0.26±0.101, 0.43±0.134, and 0.15±0.131. For the 140 sires in the dataset, Spearman rank correlations among breeding values for the four CM traits and for SCS305 were uniformly high at 0.99±0.001.
The aim was to investigate the antimicrobial susceptibility of most frequently isolated streptococci from Czech dairy herds. A total of 3,719 quarter milk samples were collected and cultivated between January 2017 and June 2018 from cows with clinical or subclinical mastitis from 112 farms. Only one isolate of each species, collected from the same farm per six-month period, was included in the susceptibility testing. The susceptibilities of Streptococcus uberis (163 isolates) and S. dysgalactiae (25 isolates) to 10 antimicrobials (penicillin – PEN, amoxicillin/clavulanic acid – AMC, ceftiofur – EFT, clindamycin – CLI, gentamicin – GEN, streptomycin – STR, trimethoprim/sulfamethoxazole – SXT, enrofloxacin – ENR, tetracycline – TET, rifampicin – RIF) from 9 groups were determined by measuring their minimum inhibitory concentrations. The percentages of resistant S. uberis isolates to the antimicrobials were as follows: TET (63.2%), STR (52.1%), CLI (30.1%), and RIF (2.5%). Intermediate susceptibility was found to RIF (63.2%), PEN (35%), ENR (2.5%), EFT (1.8%), and AMC (1.2%). All the S. uberis isolates were susceptible to GEN and SXT (100%). However, only 6.7% of S. uberis isolates were susceptible to all tested antimicrobials, and 38.7% of isolates were multidrug resistant (≥ 3 groups of antimicrobials). All the S. dysgalactiae isolates were susceptible to PEN, AMC, EFT, GEN, SXT, and ENR (100%). Resistant S. dysgalactiae isolates were found to TET (60%), STR (28%), CLI (12%), and intermediate to TET (24%) and RIF (20%). Sixteen percent of S. dysgalactiae isolates were multidrug resistant. The relatively high occurrence of (multiple) resistance, relative to mastitis pathogens, highlights the importance of monitoring this condition in dairy herds.