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Assessing the risk of subclinical intramammary infection in non-clinical quarter(s) by test day somatic cell count or clinical symptoms.

K. Morrill

Events

06-24-2020

Abstract:

356
Assessing the risk of subclinical intramammary infection in non-clinical quarter(s) by test day somatic cell count or clinical symptoms.
K. Morrill*, J. Scillieri Smith. Cornell University Ithaca, NY.

The objectives of this project were 1) to evaluate the rate of subclinical mastitis (SCM) in non-clinical quarters (NCQ) of cows with clinical mastitis (CM), cows with low somatic cell count (SCC; LSCC; < 200,000 cells/mL) and high SCC (HSCC; > 200,000 cells/mL) and 2) evaluate the rate of persistent infection. Herds (n = 4) aseptically sampled milk from quarters of cows identified with CM and herdmates with LSCC or HSCC, based on DHIA testing and confirmed upon sampling. Samples were cultured using standard microbiological methods by Quality Milk Production Services (Canton, NY). Quarter level SCC was analyzed by an optic cell counter (DeLaval Cell Counter, Tumba, Sweden). All quarters with intramammary infections (IMI) were re-sampled 2—4 weeks later for aerobic culture and SCC to determine persistency of infection. Data were analyzed using SAS 9.4. A total of 1698 quarters (CM = 246, NCQ = 575, LSCC = 486, HSCC = 391) from 433 cows were included in the study. Overall, 25.7% of samples had an IMI at initial culture. Mastitis pathogens were identified in 55.3% of CM quarters and in 24.6% of NCQ. Samples from NCQ and HSCC cows were at a greater risk of having an IMI as compared with samples from LSCC cows (OR = 2.7207; CI = 1.9833 — 3.7322). One hundred and 2 CM cows (41.46%) had an IMI in at least one NCQ. Only 26 of the 209 CM cows had an IMI in the CM quarter and at least one NCQ concurrently. Only 10 CM cows had an IMI in all 4 quarters, while 49 CM cows did not have an IMI in any quarter. Follow-up samples from CM quarters were at a lower risk of having a IMI (OR = 0.519; CI = 0.3042 — 0.8281) as compared with NCQ, LSCC and HSCC quarters. Overall, 8% of quarters had a persistent IMI. High SCC quarters had a higher risk of having a IMI at follow-up sampling as compared with all other sample groups (OR = 2.9455; CI = 1.6937 — 5.1224). In conclusion, samples from CM quarters were at a greater risk of having an IMI as compared with NCQ, HSCC and LSCC quarters, however, NCQ and quarters from a HSCC cow were at a greater risk of having an IMI as compared with samples from LSCC cows.

Keywords: mastitis, somatic cell count, subclinical.