Bacterial subclinical mastitis and its effect on milk yield in low-input dairy goat herds

Abstract

The objectives of this study were (1) to record the major pathogens associated with subclinical mastitis (SCM), (2) to calculate their incidence during the milking period, and (3) to estimate the effect of SCM on daily milk yield (DMY) for goats reared under low-input management schemes. Dairy goats (n=590) of Skopelos and indigenous Greek breeds from 4 herds were randomly selected for the study. The study included monthly monitoring, milk yield recording, and bacteriological analyses of milk of individual goats during the course of 2 successive milking periods. Incidence and cumulative incidence were calculated for SCM cases. Moreover, 2 mixed linear regression models were built to assess the effects of (1) SCM and (2) different pathogens isolated from SCM cases, on DMY. The estimated incidence and cumulative incidence of SCM for the first and the second year of the study were 69.5 and 96.4 new cases of SCM/1,000 goat-months, and 24.1 and 31.7%, respectively. A total of 755 milk samples were subjected to microbiological examination, resulting in 661 positive cultures. Coagulase-negative and coagulase-positive staphylococci were isolated from 50.2 and 34.5% of the positive cultures, respectively. The incidence of infections (new infections per 1,000 goat-months) for the first and the second year of the study were 34 and 53 for coagulase-negative staphylococci, 23 and 28 for coagulase-positive staphylococci, 3 and 5 for Streptococcus/Enterococcus spp., and 5.5 and 9.1 for gram-negative bacteria. Goats with SCM had lower DMY when compared with goats without SCM (ca. 47g/d, corresponding to a 5.7% decrease in DMY). In particular, goats with SCM due to coagulase-positive staphylococci infection produced approximately 80g/d less milk (a reduction of ca. 9.7%) compared with uninfected ones, whereas SCM due to gram-negative bacteria resulted in approximately 15% reduction in DMY. Investigating the epidemiology of SCM and its effects on production traits is critical for the establishment of effective preventive measures against SCM and for the assessment of the sustainability of production in low-input dairy goat herds.

Microbial agents in macroscopically healthy mammary gland tissues of small ruminants

“…Already Bergonier et al (2003b) reported a CNS prevalence in subclinical mastitis ranging from 25 to 93%. Similar results (42.9%) were recently observed also in Portugal in milk samples from clinically affected sheep udders ( Queiroga, 2017 ), in Iran in subclinical ovine mastitis ( Narenji Sani, Mahdavi & Moezifar, 2015 ), in Greece in dairy goats ( Gelasakis et al, 2016 ) and in Italy in both species ( Dore et al, 2016 ). The identification of Staphylococcus xylosus in sheep and Staphylococcus caprae in goats is also in agreement with the literature ( Bergonier et al, 2003b ; Contreras et al, 2007 ; Ergün et al, 2009 ), while Staphylococcus equorum was isolated only by Hariharan et al (2004) in sheep and by Contreras et al (2003) in goats.…”

Clinical Mastitis Gives Off-Flavor and Reduces Quality of Milk in Smallholder Goat Farms

“…They report that culture-negative mastitis which contained >1×10 6 SCC/ml resulted in 43.9% (n = 466) mastitic milk, showing that high SCC does not indicate mastitis infection. In the current study, only Staphylococcus aureus (38.6%) and Escherichia coli (22.9%) were isolated, mainly due to poor milking hygiene (Murphy et al, 2007;Persson and Olofsson, 2011;Gelasakis et al, 2016) and these findings corroborate with the current study.…”

“…In Kenya, Ndegwa et al, (2000) reported a subclinical mastitis prevalence using three measures, which was 9.8% by CMT, 9.7% by direct leukocyte counts and 28.7% by bacterial isolation. However, White and Hinckely (1999) and Gelasakis et al, (2016) have reported a prevalence rate of 31.7% to 36.4% (n = 1061). Bacterial organisms were isolated in 127 cases (22.5%) of CMT-negative samples.…”

“…It is hypothesized that the very high background SCC levels may have a negative impact on the composition and quality of raw milk produced in addition to reducing yield by up to 15% (Gelasakis et al, 2016). This study, as a part of a wider programme on mastitis dynamics and milk quality in caprines, aimed at evaluating the prevalence of mastitis infection, lactation stage and parity, quarter SCC levels and raw milk compositional quality in smallholder dairy goats.…”

Prevalence of clinical and subclinical caprine mastitis of northern region in Bangladesh

“…(Kumar et al, 2016;Rashid et al, 2017). Earlier, the highest prevalence of Coagulase Negative Staphylococci (CNS) was reported by Gelasakis et al (2016), Nickerson et al (2015) and Silanikove et al (2014). Other than single infection (85%), mixed infections (15%) were also found in this study which was supported by the observation of Sarker and Samad (2011).…”