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

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.

Uso de modelos de regressão logística para avaliar a composição físico-química do leite bovino in natura

“…A odds ratio de 0,035 para lactose indicou que o aumento em uma unidade de lactose (g/100g) esta relacionada a redução de 96,5% na probabilidade de ocorrência de mastite (Tabela 2). Associações negativas entre lactose e infeção por mastite em bovinos também foram documentadas na literatura por Reis et al (2013) e Gonçalves et al (2016). A menor síntese de lactose pode ser ocasionada pela destruição de tecido secretor, também pela perda de lactose da glândula para a corrente sanguínea decorrente do aumento da permeabilidade da membrana que separa o leite do sangue e à utilização da lactose pelos patógenos intramamários nos animais positivos para mastite (ARAÚJO et al, 2011).…”

“…Deste modo, o conhecimento dos fatores que influenciam a produção e a composição do leite é preponderante para o sucesso da empresa rural produtora de leite (ARAÚJO et al, 2011;VLIEGHER et al, 2012). A influência da mastite na composição físico-química do leite bovino in natura está bem documentada na literatura (PEREIRA et al, 1999;NIELSEN et al, 2005;ARAÚJO et al, 2011;RANGEL et al, 2013, REIS et al, 2013, GONÇALVES et al, 2016. Contudo, a relação entre composição físico-química do leite e probabilidade de ocorrência de mastite não foi quantificada.…”

Subclinical intramammary infection does not affect bovine milk ethanol stability

“…Mammary quarters were individually milked using a bucket milking system as described by Gonçalves et al (2016). This milking system allowed the milk to flow separately from each mammary quarter into a bucket.…”

“…Statistical analysis for comparison of contralateral mammary quarters: the effect of subclinical mastitis on MES was evaluated by comparison of contralateral mammary quarter using split plot design Gonçalves et al (2016). …”

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

“…Considering that healthy contralateral mammary quarters produce similar amounts of milk, and have independent milk production, using the comparison between the pair of infected quarters versus their healthy contralateral within the cow, it would be possible to evaluate the effect of subclinical mastitis caused by specific pathogens on SCC, milk yield and composition. Thus, this approach could minimize confounding factors at both cow and herd level (such as the cow's immune status at 32 the time of infection, management systems or environmental challenge) that could decrease the accuracy of milk loss estimation (GONCALVES et al, 2016). The use of SCCs to estimate milk yield reduction, associated with subclinical mastitis, has been widely used .…”