Determination of milk production losses in Valle del Belice sheep following experimental infection of Mycoplasma agalactiae

Abstract

a b s t r a c tEconomic losses due to contagious agalactia (CA) in small ruminant herds are mainly associated with significant reductions in or complete loss of dairy production, mortality, abortions, ill thrift, early culling and costs of control. With the aim of estimating milk production losses caused by CA, 46 primiparous lactating Valle del Belice ewes were monitored after experimental infection. Sixty days after lambing, two ewes were each experimentally infected with a single dose of 10 8 CFU/ml of a live Mycoplasma agalactiae strain in both teats by intracanalicular route. Three days after inoculation, the infection was spread manually by the milkers dipping their hands in the pooled milk from the experimentally infected ewes just before milking each of the uninfected sheep. The milk yield was recorded daily (morning and evening) for 12 weeks: 5 weeks before and 7 weeks after infection. Daily milk data, collected from each ewe, were used to design individual lactation curves in order to estimate the impact of CA infection. Individual milk samples were screened for the presence of M. agalactiae as well other pathogens which cause mastitis in small ruminants comprising Staphylococcus aureus, coagulase negative-staphylococci (CNS), Corynebacterium spp. and Streptococcus spp. No pathogens were detected in the milk of 10 (22%) of the 46 ewes kept with the experimentally infected sheep. There was a reduction of 17% in milk output of 19 (41%) ewes from which M. agalactiae was isolated; the 17 (37%) remaining ewes had a similar drop in milk production but recovered quickly within 2-3 weeks, so the final losses were estimated to be 3%. The infected milk showed a significantly higher somatic cell count when mycoplasma excretion in milk was >10 3 CFU/ml. Percentages of milk protein and casein were higher in milk excreting M. agalactiae due to concentration, in contrast the percentage of lactose in the milk was significantly lower. No significant effect of M. agalactiae was found on the percentage of milk fat.In conclusion, the loss of milk following CA infection is variable and probably related to the degree of exposure and capacity of the individual ewe to resist the pathogen.

Effect of Mycoplasma agalactiae mastitis on milk production and composition in Valle dell Belice dairy sheep

“…With regard to the effect of losses in milk production, the estimated losses were approximately 12.5% and ranged from 1514 g for healthy ewes to 1327 g for infected ewes. The lower milk production of infected sheep was similar to results reported by Todaro et al (2015) who found a decrease of about 17% of milk in experimentally infected ewes of the same sheep breed. Our results showed that infection with M. agalactiae had a significant impact on milk production.…”

“…Similar results were obtained by Contreras et al (2008) in goat bulk-tank milk. An increase in somatic cell count was also reported in ewes experimentally infected with M. agalactiae (Bergonier et al 1996;Todaro et al 2015). In a study of bulk tank milk from different goat herds co-infected with various Mycoplasma spp., the presence of different Mycoplasma spp.…”

“…Leitner et al (2003) reported a higher total protein concentration and lower lactose in sheep with subclinical mastitis. Todaro et al (2015) reported negative effects of M. agalactiae on fat and protein content probably due to the lower functionality of the udders of infected ewes. In particular, the authors showed a higher protein percentage (5.66 versus 4.84%) and a lower lactose percentage (3.64 versus 4.66%) in experimentally infected Valle del Belice ewes compared to healthy animals.…”

“…Studies on the effects of CA on milk yield and composition in small ruminants are scarce. In one study on the same sheep breed a reduction of 17% of milk yield and an alteration of milk chemical composition was observed (Todaro et al 2015). In clinically affected herds, a significant increase in somatic cell counts from bulk milk tank in sheep and goat was observed (Gonzalo et al 2005;Contreras et al 2008).…”

Evaluation of effects of Mycoplasma mastitis on milk composition in dairy cattle from South Australia

“…It is generally thought that milk proteins increase during mastitis due to increases in blood albumins and immunoglobulins influx as an immune response [ 3 , 18 ]. Protein percentage increases have been reported during M. agalactiae experimental mastitis in small ruminant [ 60 ].…”