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A comparison of somatic cell count trends following the treatment of clinical mastitis with and without intramammary antibiotics : a case study on a large, commercial NY dairy

Author
Smith, Stevie E.
Abstract
Milk cultures from 153 cases of clinical mastitis were taken from day 0 (day at which mastitis
case was identified) to 28 days after case identification from cows housed in a commercial, free-stall
dairy in New York (Sunny Side Dairy). Cases included in this study were identified by farm personnel
as having clinical mastitis based on visible signs (udder and milk quality) and were confirmed using the
California Mastitis Test (CMT). Cows were randomly assigned to either a treatment group receiving
intramammary (IMM) amoxicillin or a no treatment group. Milk samples were taken from the affected
quarter at day 0 for microbiological culture and somatic cell counts (SCC). Additional milk samples
were obtained twice weekly for SCC for up to 28 days following the original date of clinical mastitis
identification. All cases had a minimum of three milk samples taken. Four pathogen groups were
assembled based on culture results: Escherichia coli, Streptococcus spp., No growth and Other (mixed
cultures, other common mastitis pathogens). Each pathogen group was then analyzed to determine if
there was significant difference in the drop in SCC per day after the identification of clinical mastitis.
The results of the study found no significant difference in the rate of decline of SCC post treatment
when compared to the rate of decline in SCC for cows receiving no treatment over all pathogen groups.
For the Escherichia coli group the SCC dropped numerically more quickly (-0.61) when there was no
treatment, but there was no significance difference in the rate of decline of SCC of the two treatment
groups (p=0.77). The No growth pathogen group had similar results with a greater rate of decline in
SCC (-0.73) when cases did not receive treatment numerically, but no significant difference (p=0.15)
between IMM amoxicillin and no therapy. Clinical cases caused by Streptococcus spp. had a slower
rate of SCC decline (+1.10) if they did not receive therapy showing a positive numerical effect in SCC
decline when IMM amoxicillin was used. This difference, however, was statistically insignificant
(p=0.09). The Other pathogen group also showed a numeric benefit in drop in SCC (+0.13) when IMM
therapy was used, but as all other groups was not significant (p=0.11).
(Key words: mastitis, somatic cell count, intramammary antibiotic therapy)
Journal/Series
Senior seminar paper Seminar SF610.1 2006 S66
Date Issued
2005-09-14Subject
Cattle -- Diseases -- Treatment -- New York (State); Mastitis -- Prevention
Type
term paper