Effects of bovine subclinical mastitis caused by Corynebacterium spp. on somatic cell count, milk yield and composition by comparing contralateral quarters

Juliano Leonel Gonçalves,Tiago Tomazi,Juliana Regina Barreiro,Daniele Cristine Beuron,Marcos André Arcari,Sarah Hwa In Lee,João Pessoa Araújo Junior,Marcos Veiga Dos Santos

doi:10.1016/j.tvjl.2015.08.009

Juliano Leonel Gonçalves, Tiago Tomazi + Show 6 more

Open Access

https://doi.org/10.1016/j.tvjl.2015.08.009

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Abstract

Subclinical mastitis caused by Corynebacterium spp. (as a group and at the species level) was investigated by evaluating contralateral (healthy and infected) mammary quarters for somatic cell count (SCC), milk yield and composition. Selection of cows with subclinical mastitis caused by Corynebacterium spp. was performed by microbiological culture of composite samples collected from 1242 dairy cows from 21 dairy herds. For each of the selected cows, milk yield was measured and milk samples were collected at the mammary quarter level (i.e., 1140 mammary samples collected from 285 cows) for analysis of milk composition and SCC. The identification of Corynebacterium spp. isolates was performed by 16S rRNA gene sequencing.One hundred and eighty Corynebacterium spp. isolates were identified, of which 167 (92.77%) were C. bovis and eight (4.44%) non-C. bovis; for five of the Corynebacterium spp. isolates (2.77%), sequencing of 16S rRNA genes did not allow identification at the species level. Mammary quarters infected with Corynebacterium spp. as a group had a higher geometric mean SCC (197,900 cells/mL) than healthy contralateral mammary quarters (85,800 cells/mL). Species of Corynebacterium non-C. bovis were infrequently isolated and did not change SCC, milk yield or milk solid contents when evaluated at the contralateral quarter level. Although C. bovis infection showed no effect on milk yield, fat, protein, casein or total solids in milk, it increased SCC and decreased lactose and milk solids non-fat content.

Highlights

Mastitis is the most costly disease affecting dairy cattle (Djabri et al, 2007; Halasa et al, 2007) and it presents most commonly in the subclinical form caused by bacteria (Djabri et al, 2002; Andersen et al, 2010)
Species of Corynebacterium non-C. bovis were infrequently isolated and did not change somatic cell count (SCC), milk yield or milk solid contents when evaluated at the contralateral quarter level
Composite milk samples were collected from 1242 dairy cows during the first sample collection to screen cows with subclinical mastitis caused by Corynebacterium spp

Summary

Introduction

Mastitis is the most costly disease affecting dairy cattle (Djabri et al, 2007; Halasa et al, 2007) and it presents most commonly in the subclinical form caused by bacteria (Djabri et al, 2002; Andersen et al, 2010). Subclinical mastitis increases the somatic cell count (SCC) and reduces the milk yield of dairy cows (Forsbäck et al, 2009). Adoption of various strategies to control mastitis during the last few decades has resulted in a decreased frequency of clinical and subclinical mastitis caused by major pathogens. The frequency of subclinical mastitis caused by minor pathogens is still a challenge for dairy farmers (Haltia et al, 2006; Souto et al, 2008; Taponen and Pyorala, 2009). Corynebacterium bovis is a contagious microorganism frequently isolated from cases of subclinical mastitis. Despite the high frequency of isolation, Corynebacterium spp. are considered minor pathogens of mastitis (Bradley and Green, 2005; Schukken et al, 2009). The effects of Corynebacterium spp. on milk yield and composition remain largely unknown

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