Dairy Sheep Symposium - the Department of Animal Sciences ...

nearly 1. As a consequence this change is not adequate since it has no advantages and it is more
expensive to measure.
Udder Morphology
Mechanical milking in sheep encounters several problems among which we can point out the
high udder morphology variability within populations and the negative evolution of udder morphology
with milk performance improvement. This situation has led to the establishment of the
optimal ovine udder morphology for mechanical milking called “udder machine” by Mikus
(1978) which main characteristics are: well attached (inserted) udders with vertical teats of
intermediate size and lower external cistern height. It is not difficult to obtain such an udder type
through genetic improvement if an adequate methodology for mammary morphology evaluation
is available. However, the methods traditionally used in sheep cannot easily be incorporated into
selection programs. The method described by Labussière et al. (1981) is based on several measures
performed directly on each animal and as a consequence it shows some drawbacks such as
low speed, laboriousness and expense in personnel making its application infeasible for commercial
farms. For its part classification by types (Sagi and Morag, 1974) is at a disadvantage because
BLUP methods are less suited for estimating genetic values for the non-continuous traits
involved in these analyses.
In order to solve this situation a system for morphological appraisal of the udder based on a
linear scale was proposed for dairy ewes as an alternative (de la Fuente et al., 1996). This method
relies on a limited number of traits, those with greater influence on aptitude for mechanical
milking. Of them four are basic udder traits (illustrated in figure 1) and the fifth globally defines
udder morphology.
Figure 1. Basic traits proposed for a linear evaluation of the udder in sheep
depth
attachment
placement
A linear scale “1 to 9 points” was fixed for the evaluation similarly to the methodology that
efficiently solved the appraisal of cattle studs for morphological types. The five traits proposed for
the evaluation method are described below following de la Fuente et al. (1996) and the punctuation
scale is illustrated in figure 2:
Udder depth is defined by the distance between rear attachment and the udder floor, using as
a reference the hock. Udders with excessive depth (below the hock) usually reflect deficiencies
in the suspensory ligament.
Udder attachment is determined by the perimeter of the insertion to the abdominal wall of
the ewe. The maximum insertion base (9 points) is considered optimum.
Teat placement is defined by the teat angle. The optimum is completely vertical teats (9
points), directed toward the ground, which coincide with minimum cistern height.
size