Blood biochemical changes upon subclinical intramammary infection and inflammation in Holstein cattle

• Published in: Journal of dairy science Vol. 106; no. 9; pp. 6539 - 6550
• Main Authors: Pegolo, S., Giannuzzi, D., Piccioli-Cappelli, F., Cattaneo, L., Gianesella, M., Ruegg, P.L., Trevisi, E., Cecchinato, A.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01-09-2023; Elsevier
• Subjects: bacteriological examination; blood traits; somatic cell count; subclinical mastitis; bacteriological examination; somatic cell count; subclinical mastitis; blood traits
• ISSN: 0022-0302; 1525-3198
• DOI: 10.3168/jds.2022-23155

The aim of this study was to investigate the associations between subclinical intramammary infection (IMI) from different pathogens combined with inflammation status and a set of blood biochemical traits including energy-related metabolites, indicators of liver function or hepatic damage, oxidative stress, inflammation, innate immunity, and mineral status in 349 lactating Holstein cows. Data were analyzed with a linear model including the following fixed class effects: days in milk, parity, herd, somatic cell count (SCC), bacteriological status (positive and negative), and the SCC × bacteriological status interaction. Several metabolites had significant associations with subclinical IMI or SCC. Increased SCC was associated with a linear decrease in cholesterol concentrations which ranged from −2% for the class ≥50,000 and <200,000 cells/mL to −11% for the SCC class ≥400,000 cells/mL compared with the SCC class <50,000 cells/mL. A positive bacteriological result was associated with an increase in bilirubin (+24%), paraoxonase (+11%), the ratio paraoxonase/cholesterol (+9%), and advanced oxidation protein product concentration (+23%). Increased SCC were associated with a linear decrease in ferric reducing antioxidant power concentrations ranging from −3% for the class ≥50,000 and <200,000 cells/mL to −9% for the SCC class ≥400,000 cells/mL (respect to the SCC class <50,000 cells/mL). A positive bacteriological result was associated with an increase in haptoglobin concentrations (+19%). Increased SCC were also associated with a linear increase in haptoglobin concentrations, which ranged from +24% for the class ≥50,000 and <200,000 cells/mL (0.31 g/L) to +82% for the SCC class ≥400,000 cells/mL (0.45 g/L), with respect to the SCC class <50,000 cells/mL (0.25 g/L). Increased SCC were associated with a linear increase in ceruloplasmin concentrations (+15% for SCC ≥50,000 cells/mL). The observed changes in blood biochemical markers, mainly acute phase proteins and oxidative stress markers, suggest that cows with subclinical IMI may experience a systemic involvement.