Usability of bacteriological milk analyses for genetic improvement of udder health in Austrian Fleckvieh cows

In addition to somatic cell count records and clinical mastitis diagnoses, results of bacteriological milk analyses provide valuable information regarding udder health. The pathogen causing an udder infection is currently not considered in Austria as part of the information used for estimation of routine breeding values for mastitis resistance. Therefore the objective of this study was to estimate heritabilities for, and genetic correlations between, udder traits of bacterial infection (bacterial infection, gram-positive and gram-negative bacterial infection) and routinely recorded udder health traits [acute mastitis, chronic mastitis, culling due to udder health problems, and somatic cell score (SCS)] in Austrian Fleckvieh cows. The basis for the genetic analyses was a data set with results from bacteriological milk analyses collected from 237 dairy farms and 6,822 cows over a period of 1 yr. Traits were defined as binary, apart from SCS, for which measures were available continuously. Multivariate analyses using a linear animal model were applied for estimating genetic parameters. The heritabilities for the occurrence of bacterial udder infection traits were 0.01. Heritabilities were 0.04 for acute mastitis, 0.02 for chronic mastitis, 0.02 for culling due to udder health problems, and 0.20 for SCS. Genetic correlations between bacteriological infection and the routinely recorded udder health traits were positive and ranged from 0.62 to 0.96. The genetic correlation between gram-positive and gram-negative bacterial infection was -0.20. The genetic correlation between acute and chronic mastitis was also close to zero. These results show that mastitis caused by different pathogens may be seen as different traits. As analyses were based on a relatively small data set and results were associated with rather high standard errors, further research with a larger data set should be carried out to confirm these results

Hind feet position score: A novel trait to genetically reduce lameness incidence

Lameness is an important health and welfare issue that causes considerable economic losses in dairy herds. The objective of this study was to investigate whether the hind feet position score (HFPS) can be used as an auxiliary trait for genetic evaluation of lameness. The HFPS is evaluated by visual scoring of the position of both the hind-digits to the mid-line of the cow\u27s body. The higher the heel height of the lateral claw, the higher is the HFPS, and the higher is the risk for development of lameness. In total, 3,478 records from 1,064 Fleckvieh cows from 35 farms were obtained between September 1, 2021, and March 5, 2022. Data collection was carried out by the regional milk recording organizations. Hind feet position was scored visually by trained personnel during routine milk performance testing in the milking parlor using a 3-class scoring system: score 1 = 0° to 24°. After all cows had been milked, locomotion scoring was performed for each animal using a 5-class scoring system with locomotion scores ranging between 1 (normal) and 5 (severely lame). Using HFPS, sensitivity and specificity were 69.5% and 66.8%, respectively, for detecting lameness defined by locomotion score ≥2. For genetic analyses, a bivariate linear animal model was fitted with fixed effects of herd, parity, lactation stage, and classifier, and random effects of animal and permanent environment. Heritabilities for HFPS and locomotion score were 0.07 and 0.10, respectively, and the genetic correlation between the 2 traits studied was 0.80. These results suggest that the HFPS could be used for genetic evaluations to reduce lameness incidence in dairy cattle