Review of physiological and anatomical factors influencing the milking ability of ewes and the organization of milking

The aim of this paper is to describe the results of the main research works undertaken on the physiological and anatomical factors of the milking ability of some genotypes of milk ewes. In all milk ewe breeds in the Mediterranean basin, milk production is always positively correlated to the size of the udder. This should, however, not be the sole criterium for the choice of animals with a view to a good milking ability. In fact: (a) the cisternal cavities must be voluminous, in order to assure the accumulation of the milk secreted over long intervals between milkings. This is the case for the Sardinian and Lacaune breeds; (b) the teats must be implanted vertically at the lowest point of the cistern (this is more frequent with the Lacaune than with the Sardinian), since teats that are placed too horizontally bend under the weight of the cups (causing the claw to fall off more easily). The milk flow is thus arrested and the ejection reflex is sometimes even blocked. Certain ewes (with one emission), in fact, retain a considerable portion of their milk (notably fat) in the “upper part of the udder” whilst others (with two emissions) successively release their cisternal milk and a large part of their alveolar milk. The latter, mainly found in the Sardinian and Lacaune breeds, are better milk producers (+25% in comparison with “one emission” animals); they adapt more easily to the suppression of hand stripping (“repasse”) and to the practice of one milking per day. Le but de cette revue est de faire le point sur le rôle des facteurs physiologiques et anatomiques en matière d'aptitude à la traite. Des exemples seront pris dans différents génotypes de brebis laitières. Dans toutes les races de brebis du bassin méditerranéen la production laitière est toujours corrélée positivement aux mensurations de la mamelle. La taille de celle-ci ne doit toutefois pas être le seul critère de choix des animaux en vue d'une bonne aptitude à la traite. En effet: (a) les cavités citernales doivent être volumineuses afin d'assurer le stockage du lait secrété au cours de longs intervalles entre traite, c'est le cas des races Sarde et Lacaune; (b) les trayons doivent être implantés verticalement au point le plus bas de la citerne (cas plus fréquent chez la Lacaune que chez la Sarde) car les trayons trop horizontaux se plient sous le poids des gobelets (qui tombent alors plus facilement). L'écoulement du lait est alors freiné etle reflexe d'éjection parfois même bloqué. Certaines bre