Effect of crossbreeding on linear udder scores and their phenotypic relationships in Iranian fat-tailed ewe's

Abstract

Now, image processing is a better technique than the subjectively assessments for linear scoring of morphologic traits, especially in fat- tailed ewe's. The objective of this study was to assess this application in animal characterization on a case study in order to comparing of, udder morphological characteristics in two Iranian crossbred sheep populations including Ghezel- Arkhamerino (GH-MR; 25 ewes), Moghani-Arkharmerino (MG-MR; 25 ewes) and a pure one that was Ghezel ewes (20 ewes). Ten udder factors and five milk traits were measured on seventy ewes during three stages of lactation. Digital pictures were analyzed by Digimizer 3.6 software. Statistical analysis of udder liner scores was performed by using the MIXED procedure of SAS 9.1 software. Results showed that long udders were more frequent in the Ghezel ewes than in crossbred's ewes. Least variation was observed for teat placement score in Ghezel purebred ewes. The means of udder depth in the Ghezel ewes were larger than in the crossbreds (P<0.01). A positive correlation between left and right teat length scores were found in the all genetic groups (rp=0.47-0.65). Milking rate (rp= 0.81) and milking time (rp= 0.37) showed significant correlations with milk yield (P <0.001). The most useful udder scores for predicting daily milk yield appears to be the left teat length, teat placement and attachment width in Ghezel ewes. Phenotypic correlations variations within linear scores and their relationships with daily milk showed the potential of improvement of these traits in breeding programs of dairy sheep.

Keywords

• crossbreeding
• milk yield
• sheep
• udder conformation traits