Dynamic of intramammary infections in Holstein x Zebu dairy cows from a herd of Minas Gerais State, Brazil

Wednesday, July 23, 2014
Exhibit Hall AB (Kansas City Convention Center)
Cristiane Viana Ladeira , Universidade Federal de Minas Gerais, Belo Horizonte, Brazil
Fernando Nogueira Souza , Universidade Federal de Minas Gerais, Belo Horizonte, Brazil
Denise Ribeiro Freitas , Universidade Federal de Minas Gerais, Belo Horizonte, Brazil
Luiz Gustavo Ladeira , EPAMIG, Belo Horizonte, Brazil
Daniel Sobreira Rodrigues , EPAMIG, Belo Horizonte, Brazil
Monica Oliveira Leite , Universidade Federal de Minas Gerais, Belo Horizonte, Brazil
Leorges Moraes Fonseca , Universidade Federal de Minas Gerais, Belo Horizonte, Brazil
Claudia Morais Penna , Universidade Federal de Minas Gerais, Belo Horizonte, Brazil
Maria Aparecida Paiva Brito , Embrapa, Juiz de Fora, Brazil
Monica Pinho Cerqueira , Universidade Federal de Minas Gerais (School of Veterinary Medicine), Belo Horizonte, Brazil
Abstract Text:

The aim of the present study was to assess the occurrence of subclinical bovine intramammary infections (IMIs) in ¾ Hosltein x Zebu cattle in a dairy herd from Empresa de Pesquisa Agropecuaria de Minas Gerais – EPAMIG. Thus, composite milk samples (n = 132) from 44 cows were collected in April, July and September (dry period) for bacteriological examination and somatic cell count (SCC). Bacterial analysis was conducted by culturing 0.01 mL of each sample on 5% ovine blood agar plates and MacConkey agar. The plates were incubated for 48 hours at 35 ºC, which was followed by Gram staining, observation of colony morphology and biochemical testing. The cow was regarded as uninfected when the milk SCC was < 200,000 cells/mL and bacteriologically negative. A new IMI was determined when a cow was bacteriologically negative and had SCC < 200,000 cells/mL, and in the next sampling the milk sample was bacteriologically positive and/or have SCC > 200,000 cells/mL, or a different pathogen was isolated. If the same pathogen was isolated in all milk samples, the cow was regarded as chronically infected for that pathogen. A cure occurred when a cow that was regarded as infected became uninfected at the end of experiment (bacteriologically negative and SCC < 200,000 cells/mL). From the 44 cows, 22 (50%) were chronically infected by S. aureus (77.27%, n = 17), Streptococcus sp. (9.09%, n = 2), coagulase negative staphylococci (CNS; 9.09%, n = 2) and Corynebacterium sp. (4.55%, n = 1). Six cows (13.64%) were initially regarded as healthy, and from these cows, four cows (75%) have become infected. Furthermore, three cows (6.82%) have been cured from IMI (two by S. aureus and one by CNS) at the end of experiment. Finally, 13 cows (29.55%) have become infected by a different pathogen from that established at the beginning of the experiment (four by S. aureus and CNS, two by Klebsiella sp., two by Corynebacterium sp. and one by S. aureus and Corynebacterium sp.). From those, five cows (38.46 %) have been cured and then, established a new infection by a different pathogen. The percentage of spontaneous cure of S. aureus IMI was 18.18%. Thus, this study demonstrated the dynamic of IMIs in a herd that needs a continuous assessment of mastitis pathogens for a comprehensive control of IMIs.

Keywords: mastitis, milk, dairy cattle