Effects of intramammary infection and dry-off treatment on the immune-metabolic profile of Alpine dairy goats

Sixty Alpine dairy goats were classified as healthy (HEAL, n = 30) or infected (INFE, n = 30) based on bacteriological culture of udder-half samples collected 7 d before dry-off. At −61 d from kidding (DFK), goats were dried off and randomly allocated to 2 homoge- neous groups either receiving no treatment (15 HEAL, 15 INFE) or being treated intramammarily with 250 mg of cefazolin per half-udder (15 HEAL, 15 INFE). Milk yield, composition, and SCC were monitored at −82, 17, 45, and 80 DFK, and blood samples were collected at −66, −56, −7, and 8 DFK to assess plasma analytes. Antibiotic administration at dry-off did not affect pro- ductive performances in the new lactation or plasma an- alyte trends. Regardless of udder health status, lactose decreased in late lactation despite stable yield, likely due to increased SCC and mammary permeability dur- ing involution. The INFE goats had higher SCC before dry-off and higher SCS at 45 DFK. Following dry-off, plasma urea decreased across all groups, reflecting di- etary changes aimed at easing milk cessation. Glucose and nonesterified fatty acids (NEFA) remained stable during the dry period. The INFE goats showed elevated plasma cholesterol at −57 DFK, suggesting transient dyslipidemia due to IMI. After kidding, all goats showed peaks in NEFA, NEFA/albumin ratio, BHB, bilirubin, and glutamate oxaloacetate transaminase, indicating body reserve mobilization and hepatic stress. Concur- rently, increases in haptoglobin and ceruloplasmin, and decreases in albumin/globulin ratio and paraoxonase, reflect an acute phase response. The INFE goats showed higher reactive oxygen metabolites and thiol concen- trations between −57 and 8 DFK, and elevated cerulo- plasmin at −7 and 8 DFK, indicating sustained systemic inflammation. Plasma analytes could serve as effective diagnostic tools to improve the detection of subclinical mastitis in dairy goats.