A preliminary study of the relationships between echotextural characteristics of the mammary gland and chemical composition of milk during early lactation in ewes

Abstract This study aimed to examine the ultrasonographic characteristics of the mammary gland in post-partum ewes (1 to 4 weeks after lambing) of varying genotypes for correlations with the chemical composition of milk. Ultrasonograms of mammary glands in coronal (C) and sagittal (S) planes were obtained using 5.0- and 7.5-MHz transducers from four Polish Mountain (PMt) and six Olkuska (Olk) ewes. Computerized image analyses of all images have been performed to determine pixel intensity (numerical pixel values-NPV) and heterogeneity (pixel standard deviation-PSD) of the mammary gland stroma/parenchyma. In PMt ewes examined with the 5.0-MHz probe, the mean NPV-C correlated negatively with C17:0 (margaric acid) and C17:1 c10 (heptadecenoic acid). Furthermore, NPV-S correlated negatively with C17:0 content of milk. In PMt ewes examined with the 7.5-MHz transducer, the mean NPV-S correlated positively with the crude fat and total solids, and negatively with C18:3 c9, c12, c15 (n-3) (α-linoleic acid) content of milk samples, while PSD-S correlated positively with C16:0 (palmitic acid) and negatively with lactose. In the scans obtained with the 5.0-MHz in Olk sheep, the mean NPV-C was directly related to C10:1 (decanoic acid), C14:1 (myristoleic acid), C16:1 iso (iso-hexadecanoic acid), C16:1 c9 (palmitoleic acid), and C18:0 (stearic acid) content; the mean PSD-C correlated positively with total solids, C14:1, C15:0, C16:0, C16:1 iso, C16:1 c9, CLA (conjugated linoleic acids), and total saturated fatty acid content, and negatively with C18:1 c11 (n-7) (cis-vaccenic acid), C18:2 c9,c12 (n-6) (linoleic acid), and total polyunsaturated fatty acid content of milk; and the mean PSD-S correlated directly with ash and total saturated fatty acid content of the milk. Lastly, the mean NPV-C of images recorded with the 7.5-MHz probe in Olk ewes related directly to ash and C12:0 (lauric acid); the mean NPV-S related directly to ash and C16:1 iso; the mean PSD-C correlated positively with ash and total saturated fatty acid (SFA) content, and the mean PSD-S correlated positively with the total SFA. Echotextural attributes of the mammary gland in ewes have the makings of the technique for determining milk content of certain chemical constituents in a breed-specific manner; however, further studies are needed to verify the usefulness of echotextural analyses of the udder to consistently predict complete milk composition.