Udder health and herd management practices associated with bulk milk somatic cell count and partial costs of subclinical mastitis on dairy farms in Uruguay.

Abstract

This study aimed to estimate the association of udder health and herd management practices with bulk tank SCC (BTSCC) and the partial costs of subclinical mastitis (milk yield losses and penalties) on dairy farms in Uruguay. As part of a cross-sectional study, a survey on udder health and herd management practices was conducted on 190 randomly selected dairy farms stratified by region and milk shipment volume (MSV). Herd data comprising 13 mo of BTSCC and MSV were obtained from the dairy processing company, and BTSCC values exceeding 250 × 10cells/mL (BTSCC >250) were identified. Multivariable regression models were developed to evaluate the association between udder health and herd management practices and 4 response variables on a monthly basis: BTSCC, BTSCC >250, milk yield losses, and penalties. In addition, we calculated the population attributable fraction (PAF) of practices associated with BTSCC >250 and their attributable cost. Postmilking teat disinfection (78%) and dry-cow therapy (80%) showed the highest adoption rates. Some practices such as culling of chronically infected cows based on records (11%), the use of automatic cluster removers (22%), the maintenance of calving areas (24%), monthly individual SCC (ISCC; 16%), and a monthly California Mastitis Test (CMT) on all cows (10%) showed low adoption rates. When adoption rates differed across MSV levels, small farms consistently had lower uptake. The lack of use of postmilking teat disinfection was associated with a higher BTSCC (30 ± 11 × 10cells/mL), higher odds of BTSCC >250 (odds ratio = 2.45), and higher milk yield losses ($1.22 ± $0.45 per cow per month). Similarly, farms that manually removed clusters showed higher BTSCC (29 ± 13 × 10cells/mL), higher odds of BTSCC >250 (odds ratio = 2.73), and higher penalties ($0.67 ± $0.28 per cow per month). For monthly ISCC, the odds of BTSCC >250 and the milk yield losses and penalties were lower, whereas on farms with maintenance of calving areas, the odds for BTSCC >250 and the penalties were lower. The partial cost of subclinical mastitis was $9.2 ± $3.9 per cow per month. Yield losses comprised 88% of the cost, and variability among farms was high. Practices associated with BTSCC >250 (postmilking teat disinfection, use of automatic cluster removers, monthly ISCC, and maintenance of calving areas) showed high PAF values. Our results highlight opportunities, some with a potential population effect, to reduce subclinical mastitis and increase overall farm profitability, particularly on smaller farms, and underscore the potential benefits of improved udder health management in Uruguay.