Study of factors affecting udder traits and assessment of their interrelationships with milking efficiency in Chios breed ewes

Abstract

Objective of the study was to assess udder morphology and milking characteristics of Chios-breed dairy ewes. Moreover, by using Principal Component Analysis, the probability of any correlations between various udder traits was studied. Thirty pure-bred Chios-breed dairy ewes in a commercial flock were assessed for 10 udder traits (6 direct and 4 indirect measurements) during three consecutive lactations. Milk yield (MY) and milking time (MT) were electronically recorded for each ewe on a daily basis. Direct measurements included udder length (UL), udder width (UW), udder height (UH), gland cistern height (CH), teat length (TL) and teat diameter (TD). Indirect measurements included teat placement (TP), udder depth CUD), udder cleft (UC) and degree of suspension of the udder (SU). Data analysis was performed using SPSS 16(C). The results showed that mean values for UL, UH and TP increased from first to third lactation; TL and TD did not change, whilst UD and UC decreased. The UH and CH were all negatively correlated with UD and SU (P<0.01) and positively correlated with TP (P<0.01). UW had a significantly negative and positive relationship with UD and UC (P<0.01), respectively. Significant negative correlations were also revealed between TL and TP (P<0.01). Four PCs ('udder dimensions', 'teat', 'udder morphology' and 'teat and suspension') were recognized explaining about 76% of the total variance. Effect of lactation number was significant for UL, UH, CH, TP, UD, UC, 'udder dimensions' and 'udder morphology' variables (P<0.05 to P<0.001). 'Udder dimension', 'teat' and 'udder morphology' were significantly related to MY (P<0.05 to P<0.001). In conclusion, the results provide significant information for udder characteristics of the Chios breed, which is the most popular indigenous Greek breed of sheep. Such information could be used as a basis for genetic improvement of the breed. (C) 2011 Elsevier B.V. All rights reserved.