Genetic parameters for the size of udder cisterns in ewes diagnosed by ultrasonography among breeds: Improved Valachian, Tsigai, Lacaune and their crosses
|Cathegory||Publication in SCOPUS DB|
Udder cistern size in ewes was diagnosed by ultrasonography, using a 3.5MHz linear probe applied laterally from side or ventrally from bottom. The acquired ultrasound images were used to digitally determine the left and right cistern sizes. Both cisterns were scanned approximately 12 hours after the last milking. The area of the left (ALC1; 1933.35 mm2) and right udder cisterns (ARC1; 1970.72 mm2), were determined using from side scans of 378 ewes, obtained at different phases of the lactation cycle), for a total of 1198 measurements. The area of the left (ALC2; 2137.67 mm2) and right udder cisterns (ARC2; 2171.12 mm2) as determined using from bottom scans, from 265 ewes; for a total of 753 measurements. The sums of both cross-sectional areas detected by the method from side (SLRC1) was 3904.07 mm2, and by the method from bottom (SLRC2) was 4308.77 mm2. Primary data were processed using REML methodology and the multiple trait animal model, using the programs REMLF90 and VCE 4.0. In the models, animal was ascribed as a random additive genetic effect and ewe as a permanent effect. Control year (7 or 5 levels), lactation stage (4 levels), breed group (9 levels) and parity (3 levels) were all ascribed as fixed effects. We found higher values of heritability (h2) for the parameters determined by the method from bottom. Heritability coefficients for ALC1 and ALC2 were 0.07 and 0.18 respectively, for ARC1 and ARC2 were 0.17 and 0.2 respectively, and for SLRC1 and SLRC2 were 0.12 and 0.17 respectively. Genetic correlations between ARC1 and ARC1 or ARC2 and ARC2 were high (rg= 0.73 and 0.91). Similarly, the correlations between the size of left and/or right cistern and the total size of both cisterns were high using both ways of scanning (rg= 0.90 to 0.98). In conclusion, measuring the size of the udder cisterns from side is recommended, although measurements from bottom show slightly higher heritability coefficients.
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