Bovine subclinical intramammary infection caused by coagulase-negative staphylococci increases somatic cell count but has no effect on milk yield or composition

Abstract

The aim of this study was to evaluate the effect of subclinical intramammary infection (IMI) caused by coagulase-negative staphylococci (CNS) as a group and by specific CNS species on milk yield and composition and somatic cell count (SCC) of dairy cows. Selection of cows with IMI caused by CNS was performed by microbiological cultures of composite samples collected from 1,242 dairy cows distributed in 21 dairy herds. After selection of cows, milk yield was measured and milk samples were collected at the mammary quarter level (i.e., 1,140 mammary samples collected from 285 cows) for analysis of milk composition and SCC. In total, 108 isolates of CNS were identified at the species level by PCR-RFLP analysis. Forty-one pairs of contralateral mammary quarters, with and without IMI, were used to evaluate the effect of CNS on milk yield and composition. Mammary quarters infected with CNS had higher geometric mean SCC (306,106 cells/mL) than noninfected contralateral mammary quarters (62,807 cells/mL). Intramammary infection caused by CNS had no effect on milk yield or on contents of fat, crude protein, casein, lactose, total solids, and solids-not-fat. Staphylococcus chromogenes was the most prevalent CNS species in this study and the only species that allowed within-cow evaluation. The IMI caused by S. chromogenes increased SCC but had no effect on milk yield and composition at the quarter level. In conclusion, subclinical mastitis caused by CNS increased the SCC but had no effect on milk yield and composition of dairy cows.

Quarter- and cow-level risk factors for intramammary infection with coagulase-negative staphylococci species in Swiss dairy cows

“…Subclinical IMI caused by CNS are highly prevalent in European dairy herds (Roesch et al, 2007;Sampimon et al, 2009;Rüegsegger et al, 2014), including herds with a high bulk milk SCC (Piepers et al, 2007). With improved control of major mastitis pathogens, minor pathogens, such as CNS, are coming more into focus as causative agents of increased SCC Tomazi et al, 2015).…”

<b>Impact of subclinical mastitis on milk yield and economic return of dairy cows</b>

“…However, HAMANN and REICHMUTH (1990) In the present study, subclinical quarter IMI with minor pathogens had no significant effect on milk yield and composition. This is in agreement with recent results from other studies that evaluated natural IMI (TOMAZI et al, 2015; GONÇALVES et al, 2016), in whichCorynebacterium bovis and Staphylococcus chromogenes were most frequent minor pathogens causing SM. The impact of subclinical IMI by CNS and Corynebacterium bovis on milk yield and composition remain controversial (RAINARD; POUTREL, 1982;LEVAN;EBERHART; 79 KESLER, 1985).…”

“…Additionally, we determined the economic return (quarter milk yield × milk price) at the quarter level using one simulation of the milk price by MQPP. Mammary TOMAZI et al, 2015). The frequency of Gram-negative pathogens isolated from mammary quarters with SM (2.4%) was similar to previous study (< 1%) (COULON et al, 2002;KOSKINEN et al, 2010).…”

No effects of homeopathy on somatic cell count, bovine milk yield and composition

“…According to these authors, an animal with mastitis may fail to produce 0.5 to 3 L per day due to high levels of SCC. However, Tomazi et al (2015) did not show any influence of mastitis caused by coagulase-negative staphylococci on production and milk composition, which suggests that productivity may be affected by the severity of inflammation and even the causative agent. Comparing the results of both mentioned studies, it seems that milk yield is only affected when average levels of SCC are high enough to result in a severe inflammatory process that interferes with the proper physiological functioning of the animal.…”

“…Mastitis is the most prevalent disease in dairy cattle, especially in its subclinical form and is responsible for major losses in the milk industry (TOMAZI et al, 2015). The consequent inflammation of the mammary gland can result in a reduction in milk production and solids, caused by changes in secretory epithelial cells and vascular permeability of secreting alveoli during infection (ZHAO;LACASSE, 2008).…”