Application of multiblock analysis to identify key areas and risk factors for dairy cow persistence.

The present study analysed the importance of individual variables and different thematic blocks of production areas, management, and herd infectious disease status on cow persistence, characterised by herd on-farm mortality rate (MR), culling rate (CR), and mean age of culled cows (MAofCC) applying multiblock partial least squares (mbPLS) analysis. This study included 120 free-stall dairy herds with ≥ 100 cows. Data on the previous year's predominant cow housing system and management practices were collected, and on-farm measurements and cow scoring were performed. Bulk tank milk (BTM) and heifer blood samples (10 samples per herd) were collected and analysed for antibodies against the selected pathogens. In total, 172 variables were aggregated into 14 thematic blocks. The annual CR, MR, and MAofCC values were calculated for each herd. Thematic blocks with significant impact on cow persistence (included herd MR, CR and MAofCC) were 'infectious diseases' (block importance index out of all blocks = 13.6%, 95% CI 10.3; 20.5), 'fertility management' (16.3%, 95% CI 6.8; 26.9), 'lactating cow management' (11.5%, 95% CI 6.4; 17.8), 'milking' (11.3%, 95% CI 3.2; 17.1), 'herd characteristics' (10.1%, 95% CI 6.3; 14.2), 'close-up period management' (9.7%, 95% CI 2.7; 15.7), 'calving management' (7.9%, 95% CI 3.1; 11.4) and 'disease management' (7.3%, 95% CI 0.2; 12.0). Variable categories with the highest importance in explaining composite outcome including herd MR, CR and MAofCC were rear-end and udder lesions in ≥ 20% of the cows, BTM and heifers seropositive to bovine respiratory syncytial virus, vaccination against bovine herpesvirus 1, twice daily milking and herd location in Northwest region. Larger herd size, higher levels of milk yield, and rearing predominantly Holstein breed cattle were herd factors associated with poorer cow persistency. Grazing cows and having semi-insulated barns were associated with lower CR and MR, respectively. Heat detection and farm pregnancy testing strategies were significant factors in the fertility block. Using disposable dry papers for teat cleaning and not using any wet teat-cleaning tools were risk factors for high MR. A robotic milking system was protective for increased herd MR and CR. A high pre-calving body condition score and poor rear body cleanliness of ≥ 30% of cows were associated with inferior herd persistency outcomes. Calving in group pens with deep litter bedding was associated with a lower CR. Multiblock PLS model is innovative tool that helped to identify most influential farming areas but also single risk factors associated with cow persistency described by multiple parameters.

Attitudes and personality of farm managers and association with cow culling rates and longevity in large-scale commercial dairy farms.

The farmer has the central role in determining cow culling policies on their farm and thus affecting cow longevity. The present study aimed to examine farm managers´ satisfaction, attitudes, personality traits and analyse the associations with dairy cow culling and longevity in large commercial dairy farms. Farm managers of 116 dairy herds rearing at least 100 cows in freestall barns were included. A questionnaire for the farm managers registered personal background information of respondent and included statements capturing their satisfaction, opinions and attitudes regarding dairy cow culling and longevity, farming in general, and a Ten Item Personality Inventory scoring. For each herd, the last 12 months cow culling rate (CR, excluding dairy sale) and herd mean age of culled cows (MAofCC) was obtained from the Estonian Livestock Performance Recording Ltd. A K-mean clustering algorithm was applied to subgroup farm managers based on their attitudes, opinions and personality traits. The yearly mean herd CR was 33.0% and MAofCC was 60.6 months. Farm managers´ were mostly dissatisfied with cow longevity and culling rates in their farms. Dissatisfaction with culling rates and longevity, priority for producing high milk yields over longevity and production-oriented attitude was associated with high culling rates and poor longevity. Farm managers' personality had an effect on herd culling rates and their attitudes explained one third of the variability of culling rates and longevity. Explaining the economic consequences of high culling rates and decreased longevity, improving the visibility of these parameters together with benchmarking could bring these issues into focus.

Seroprevalence of selected endemic infectious diseases in large-scale Estonian dairy herds and their associations with cow longevity and culling rates.

Herd culling rates and longevity represent herd health and welfare status as well as farm economic performance. The contribution of endemic circulation of the main cattle pathogens to herd performance has not been previously analysed. The aim of this study was to estimate the herd prevalence of selected endemic bovine pathogens among large commercial dairy herds and to analyse their associations with herd culling rates and longevity. Bulk tank milk (BTM) samples and 10 heifer serum samples were collected from 120 Estonian dairy herds with at least 100 cows, between August 2019 and July 2020. All samples were tested for antibodies against bovine herpesvirus 1 (BHV-1), bovine viral diarrhoea virus (BVDV), bovine respiratory syncytial virus (BRSV), Mycoplasma bovis, Mycobacterium avium spp. paratuberculosis (MAP) and Salmonella Dublin using commercial ELISA. Data on herd size, milk yield, culling rate (CR) and mean age of the culled cows (MAofCC) were collected from the Estonian Livestock Performance Recording Ltd. The apparent herd and animal prevalences were calculated, and linear regression models were used to identify associations between the herd status of six tested pathogens and CR and MAofCC. The herd seroprevalences for antibodies based on BTM and heifer serum sample testing were BHV-1 56.7 % (95 % CI 47.3; 65.7), Mycoplasma bovis 48.3 % (95 % CI 39.1; 57.6), MAP 2.5 % (95 % CI 0.5; 7.1) and S. Dublin 24.2 % (95 % CI 16.8; 32.8) in all tested herds. Excluding vaccinated herds, herds prevalence for BVDV was 27.0 % (95 % CI 19.0; 36.3) and for BRSV 94.7 % (95 % CI 88.1; 98.3). Herd seropositive status for BRSV was associated with lower MAofCC, and herds with BSRV-seropositive youngstock had increased CR. Herds with positive BTM test results for S. Dublin culled cows at an older average age (Coef = 3.79 months, 95 % CI 0.52; 7.07, p = 0.023). MAP-positive herds had somewhat lower herd MAofCC (Coef = -6.18 months, 95 % CI -12.98; 0.63, p = 0.075). There was also a tendency of BVDV-negative herds to have a lower CR than BVDV-positive herds (Coef = -3.03 %, 95 % CI -6.54; 0.49, p = 0.090), and vaccination against BVDV tended to be protective against high CR (Coef = -6.26 %, 95 % CI -12.61; 0.09, p = 0.053 compared to infected herds). This study shows that Estonian large-scale dairy herds are endemically infected with several important cattle pathogens. Most of the studied pathogens influence longevity and culling rates, thus entailing health and economic consequences.

Culling reasons and risk factors in Estonian dairy cows.

BACKGROUND: Culling is a major cost for dairy farms but also an essential part in managing herd productivity. This study aimed to identify the culling rates of Estonian dairy cows, identify the farmers' stated reasons and risk factors for culling. This observational study used registry data of all cows from herds with ≥20 cow-years in 2013-2015. Cow lactation-level analyses included data of 86,373 primiparous cows from 409 herds and 177,561 lactations of 109,295 multiparous cows from 410 herds. Weibull proportional hazard regression models were used to identify risk factors for culling due to slaughter or death. RESULTS: The overall culling rate of Estonian dairy cows was 26.24 (95% CI 26.02; 26.46) per 100 cow-years. The most common reasons farmers stated for culling were feet/claw disorders (26.4%), udder disorders (22.6%), metabolic and digestive disorders (18.1%) and fertility problems (12.5%). Animal-level risk factors for culling were Holstein breed, older parity, lower milk yield breeding value, older age at first calving, longer previous calving interval, having assisted calving, stillbirth and birth of twins/triplets. Lower milk yield, somatic cell count over 200,000 cells/ml and fat/protein ratio over 1.5 at first test-milking after calving were associated with greater culling hazard during the lactation. Cows from larger herds, herds with decreasing size and higher milk yields had a higher culling probability. CONCLUSIONS: This study emphasises the need for improved management of hoof health and prevention of mastitis and metabolic diseases. It is essential to ensure easy calving and good health of cows around calving in order to lower the culling hazard.