Factors Affecting Variation of Udder Traits in Merino Rambouillet Ewes

Authors

  • M. Ochoa-Cordero
  • G. Torres-Hernández.
  • P. Mandeville
  • M. Díaz-Gómez
  • F. Morón-Cedillo
  • C. Meza-Herrera

Abstract

The aim of this study was to determine some udder morphological characteristics and some souces of variation affecting them in Merino Rambouillet ewes under stall-fed conditions (n=54, 57.010.3 kg BW, 1 to 3 lambings). The study was conducted at the Agronomy College, San Luis Potosi Autonomous University, Mexico (22° NL, 100° WL, at 1835 m, and annual means of 17.8°C and 271 mm). Evaluation considered morphological traits, collected from d-60 to d-120 post-lambing, related to udder (U) size (depth, UD; width, UW; circumference, UC), cistern (C) morphology (hight, CH; depth, CD), and those definning teat (T) size and position (width, TW; angle, TA). No differences (P>0.05) between both halves occured for any variable, observing from low to high correlations among U, C and T traits (r=0.32 to 0.73). While udder traits diminished (P<0.05) as stage of lactation advanced, no changes in CH, CD, TW, and TL were observed. In contrast, TA decreased (P<0.05) as lambing number advanced (P<0.05). The UW increased (P<0.05) between first and the following lambings, while 2nd or 3rd lambings ewes had the largest (P<0.05) UD and UC. No differences (P>0.05) accross lambings occurred for CH, although CD increased (P<0.05) as lambing number augmented. While TW increased (P<0.05), TA (P<0.05) decreased with increases in lambing number. Average milk production from day 60 to 120 post-lambing ranged from 0.166 to 0.700 mL d-1. UW and UC were positivelly as associated to high milk yield, without UD differences (P>0.05) according to milk production level. A non clear trend for CH, CD, TW and TL occured according to milk production level. Ewes producing 10 to 20 kg of milk depicted the largest TA as compared to the high milk producing ewes. While design of milking machines for Merino Rambouillet ewes should consider proper udder traits dimensions, inclusion of these udder traits when designing future selection schemes could be of economic significance for the recently emerging Merino Rambouillet milk industry in Mexico.

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Published

2006-06-29

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Articles