Recent studies have suggested an association between reproductive failure and mastitis in lactating dairy cows, but our understanding of how mastitis affects reproduction is still limited. In the present study we investigated the effects of naturally occurring chronic mastitis on the follicular reserve and dynamics. Ovaries and milk samples were collected from 74 cows at the time of slaughter. Quarter milk samples were analyzed following National Mastitis Council procedures. Based on the presence of major pathogens and somatic cell count results, animals were sorted in 9 groups but only the two extremes were considered for further analysis: uninfected (n = 8) and affected by chronic mastitis (n = 9). Primordial, primary and secondary follicles were counted and scored on similar surface area of ovary sections for each animal (mean ± SD= 5.65 ± 0.25 cm2). The association between health status and follicle number was estimated by odds ratios ± confidence limits. Vasculature area in the ovarian cortex of healthy and mastitic animals was identified using Bandeiraea simplicifolia-I lectin (BSL-I). Results were quantified with the dedicated software MacBiophotonics image J, NIH, USA and subsequently analyzed with t-test for statistical significance. Follicles were further characterized by immunostaining with a GDF-9 specific antibody. The intensity of the staining was semi-quantified using a relative scale: 0, 1 and 2 for no, weak and strong staining respectively. Our results indicate no statistically significant difference between the numbers of primordial and primary follicles between affected and healthy animals. In contrast, the number of secondary follicles was significantly lower in sick animals (Odds ratio 10.50*; p<0.05), indicating a 10 times higher risk for mastitic animal to have less than 2 secondary follicles per square centimeter. Ovarian stromal vasculature represented the 6.38±0.66 % of healthy animals cortical area vs. 4.24±0.37%; (P<0.001) in affected cows. GDF-9 immunostaining revealed decreased fluorescence intensity in mastitic animals. Our results show that chronic mastitis is associated with considerable alterations in the follicle growth and differentiation with a decreased ability of primary follicles to develop into secondary state in affected animals. This is accompanied by a significant decrease of ovarian vasculature and the down regulation of the follicle differentiation associated factor GDF. The present findings substantiate the hypothesis that mastitis can reduce fertility exerting a negative effect on ovarian function.
|Titolo:||Naturally occurring chronic mastitis compromises folliculogenesis, affects vascularization and interacts with differentiation factor GDF-9 in bovine ovarian stroma|
|Autori interni:||MAZZILLI, MARIA (Secondo)|
ZECCONI, ALFONSO (Penultimo)
GANDOLFI, FULVIO (Ultimo)
|Settore Scientifico Disciplinare:||Settore VET/01 - Anatomia degli Animali Domestici|
|Data di pubblicazione:||2011|
|Enti collegati al convegno:||International Embryo Transfer Society|
|Digital Object Identifier (DOI):||10.1071/RDv23n1Ab170|
|Appare nelle tipologie:||01 - Articolo su periodico|
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