Abstract
The main goal of this preliminary study was to determine and compare ultrasonographic characteristics of the mammary gland in two genotypes of ewes varying in milk productivity at 2, 3 and 4 weeks after lambing. Ultrasonographic images of the udder were obtained using the 5.0- and 7.5-MHz transducers, in axial and coronal planes, in four low milk-yielding Polish Mountain sheep and six high milk-yielding Olkuska ewes. All ultrasonograms were subjected to computerized image analyses using commercially available image analytical software (Image ProPlus ® ; Media Cybernetics Inc., San Diego, CA, USA) to determine numerical pixel values (NPVs) and heterogeneity (pixel standard deviation-PSD) of the mammary gland parenchyma. During the 28-day period post-partum, the Olkuska sheep exceeded (P < 0.05) Polish Mountain ewes in milk productivity (31.6 ± 2.7 l and 25.0 ± 4.2 l, respectively; means ± SEMs) as estimated by the mean weight gains of suckling lambs. In animals examined with the 5.0-MHz transducer, mean NPVs of the mammary gland parenchyma in Olkuska ewes and mean PSD in both genotypes of ewes were lower (P < 0.05) before than after milking. In addition, PSD recorded both before and after milking were lower (P < 0.05) in the Polish Mountain compared with Olkuska breed. Mean PSD values for the mammary gland were less (P < 0.05) before than after milking in Polish Mountain ewes and they were greater (P < 0.05) in Olkuska compared with Polish Mountain ewes examined with the 7.5-MHz probe after milking. It can be concluded that milk quantity, histomorphology of the udder and ultrasound transducer frequency may all impinge on the echotextural characteristics of the mammary parenchyma in different breeds of sheep. Our observations warrant future studies of correlations between milk composition, mammary gland histophysiology and ultrasonographic image attributes of the mammary gland in ruminants.
Highlights
Grey-scale ultrasonographic images are composed of numerous brightness elements called pixels corresponding to multiple acoustic interfaces within the examined tissue (theUltrasound images of the mammary gland in ruminant species have been described as exhibiting granular texture due to the presence of less echoic lobular alveoli being dispersed within hyperechoic connective tissue (Olechnowicz and Jaśkowski, 2009; Santos et al, 2015; Barbagianni et al, 2017)
All ultrasonograms were subjected to computerized image analyses using commercially available image analytical software (Image ProPlus ; Media Cybernetics Inc., San Diego, CA, USA) to determine numerical pixel values (NPVs) and heterogeneity of the mammary gland parenchyma
In spite of similar lamb productivity, the Olkuska breed lambs exhibited greater (P < 0.05) weight gain and the Olkuska ewes had greater estimated milk productivity compared with the Polish Mountain sheep during the four-week period post-partum
Summary
Ultrasound images of the mammary gland in ruminant species have been described as exhibiting granular texture due to the presence of less echoic lobular alveoli being dispersed within hyperechoic connective tissue (Olechnowicz and Jaśkowski, 2009; Santos et al, 2015; Barbagianni et al, 2017). No studies to the best of our knowledge have quantitatively described the mammary gland parenchyma using precise measurements of echotextural variables in lactating ewes varying in milk yields. The goals of this preliminary ultrasonographic study were to describe quantitative echotextural changes in the mammary gland parenchyma of low and high milk‐yielding ewes at three different time points during the post-parturient period (at weekly intervals from 2 weeks after lambing until 4 weeks post-partum) and to examine additional factors that can impinge on mammary gland echotexture (e.g., scanning plane and the type of an ultrasound transducer used). The results of this study can serve as a set of reference values to standardize computerized image analysis of the normal ovine mammary gland ultrasonograms
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