Evaluation of somatic cell count thresholds to detect subclinical mastitis in Gyr cows

Abstract

The objectives of this study were (1) to determine the sensitivity (Se) and specificity (Sp) of somatic cell count (SCC) thresholds to identify subclinical mastitis in Gyr cows caused by major and minor pathogens; (2) to study the effects of month of sampling, rear or front mammary quarters, herd, intramammary infection (IMI), and bacterial species on SCC at quarter level; and (3) to describe the prevalence of IMI in Gyr cows in commercial dairy herds. In total, 221 lactating Gyr cows from 3 commercial dairy farms were selected. Milk samples were collected from individual quarters once a month for 1 yr from all lactating cows for SCC and bacteriological analysis. Mammary quarters were considered the experimental units and the SCC results were log(10)-transformed. Four SCC thresholds (100, 200, 300 and 400 × 10(3) cells/mL) were used to determine Se and Sp to identify infected mammary quarters. The overall prevalence of IMI in quarter milk samples of Gyr cows was 49.8%, and the prevalence of minor pathogens was higher (31.9%) than that of major pathogens (17.8%). Quarter samples with microbial isolation presented higher SCC compared with negative samples. Sensitivity and Sp of selected SCC thresholds varied according to the group of pathogen (major and minor) involved in the IMI definition. Sensitivity increased and Sp decreased when mammary quarters with only major pathogens isolation were considered positive. The use of a single SCC analysis to classify quarters as uninfected or infected in Gyr cows may not be a useful test for this breed because Se and Sp of SCC at the studied thresholds were low. The occurrence of IMI and the bacterial species are the main factors responsible for SCC variation in mammary quarters of Gyr cows. Milk samples with major pathogens isolation elicited higher SCC than those with minor pathogens.

Subclinical mastitis in dairy cows: somatic cell counts and associated bacteria in Mymensingh, Bangladesh

“…Almost similar to this result, Malek dos Reis et al, (2011) reported that rear quarter had higher log SCC (5.10) compared with front quarters (5.03). Schepers et al, (1997) also reported a higher SCC in rear quarters.…”

“…Most frequently isolated bacteria was staphylococcus aureus (18.33%) which suggests that the prevention of spread of contagious bacteria during milking was not effective. Similar to this, Staphylococcus aureus was the most frequently isolated pathogen in Sweeden (19%), Jordan (22.2%), and Brazil (30.8%) (Persson et al, 2011;Malek dos Reis et al, 2011;Alekish, 2015). Besides other minor pathogens, Staphylococcus aureus was still the most prevalent pathogen in clinically healthy animals and both environmental and contagious forms of mastitis may be caused by Staphylococcus aureus (Rall et al, 2013;Barkema et al, 2009).…”

“…Sargeant et al, (2001) reported that quarters infected with minor pathogens tend to have lower SCC values than quarters infected with major pathogens. Malek dos Reis et al, (2011) and Djabri et al, (2002) had also reported that log SCC was highest (5.51-5.79) in sample with major pathogen isolations (5.51-5.79) compared with the minor pathogen (5.04-5.31). The probability of isolating a major pathogen increases as SCC exceeds 200.00 × 10 3 cells/ml.…”

“…After 30 seconds the somatic cell count was presented on the instrument display. Individual quarter having SCC > 100 x 10 3 cells/ml were considered as SCM positive to reduce the occurrence of false-negative results (Malek dos Reis et al, 2011).…”

Ocorrência de patógenos causadores de mastite subclínica no município de Jaguapitã, estado do Paraná - Brasil

“…Subclinical mastitis is the biggest problem affecting dairy cattle worldwide (MEMON et al, 2013), usually cause a rise in somatic cell counts (SCC) and affect the daily milk production between 15-45% without visible changes to milk itself or the udder (MALEK DOS REIS et al, 2011) furthermore, may occurs expenses with treatment expenses, death or culling of animals.…”