Relationships between external and internal udder measurements and the linear scores for udder morphology traits in dairy sheep

Abstract

Udder morphology traits were measured and subjectively assessed by the use of linear scores in 266 ewes of Tsigai (T), Improved Walachian (IW) and Lacaune (LC) dairy breeds. Animals were recorded repeatedly within and between lactations, therefore 772 sets of measurements and linear scores were collected in total. Udder measurements included: udder length, udder width, rear udder depth, cistern depth, teat length, teat angle, sum of cistern cross-section areas scanned by the ultrasound technique from the side and from the bottom in a water bath. Linear scores were assessed for: udder depth, cistern depth, teat placement, teat length, udder attachment, udder cleft, and udder shape from the aspect of machine milking. Analysis of variance was conducted by the mixed procedure of SAS statistical package. The model included effects of experimental day, parity, days in milk, random effect of animal and residual error. Subsequently, correlations between random animal effects for udder measurements and linear scores were computed for individual examined breeds separately. Subjectively assessed linear scores for udder depth, cistern depth, teat position and teat size showed high correlations with actual measurements of the respective traits on udder in all examined breeds (r_p = 0.65–0.80). Linear scores for cistern depth and teat position were highly correlated (r_p = 0.84; 0.77 and 0.90 for T; IW and LC ewes), suggesting that they are nearly identical traits. Linear score for udder shape was significantly correlated with the linear score for udder attachment in all examined breeds (r_p = 0.79; 0.80 and 0.78 for T; IW and LC). In T and IW assessments of the udder shape were also highly correlated with linear score for udder height (r_p = 0.84 resp. r_p = 0.79) while in LC this correlation was close to zero. In LC assessment of the udder shape was more dependent on teat position (r_p = –0.37) and cistern depth (r_p = –0.30).