*2.4.3 Measurement of sexual behavior in bucks*

To determine the potential as a possible male, it is necessary to establish tests that allow the identification and categorization of males according to their score, taking into account comprehensively both their physical characteristics, such as weight, body condition, and sexual behavior [1].

Assessments to determine mount efficiency in bucks typically consist of exposing a male to a female in estrus, for a period of time ranging from 15 to 20 minutes to 1 hour in a pen without distractors [51]. During this period, an observer keeps track of the amount of sexual behavior. They are rapid, practical and inexpensive tests that allow identifying the willingness of the male to serve the female and together with this, discard males with unsuitable profiles within a reproductive program in natural mating in the shortest possible time [52].

In tests of reproductive capacity, motivation is linked to the animal's libido and for this reason some authors recommend the use of more than one female in estrus [49]. Other factors that influence the performance of males in the evaluation of reproductive capacity are the breed of the animal, season of the year, age, the sexual experience they have and the hierarchical position that the male occupies [33].

For the evaluation of sexual behavior in bucks there are different strategies that can be implemented to determine acts of courtship and mating acts. The reaction time test allows us to identify the time it takes for the male to achieve the first mount with ejaculate and thus have an estimate of the libido of the evaluated male [11].

The service ability test is one of the most widely used tests. It consists of placing the male before one or several females in heat for a certain period, usually between 15 to 60 minutes in a pen. During this period an observer counts the number of interactions between the male and the female (s), which can be optionally rated or, only indicate the frequency with which the courtship acts, the mounts or the ejaculations occur as the case may be [42].

Observations can be made individually or in groups. Individual observations should be made in the absence of other males, while group observations should take into account that they must be of similar ages to give accuracy to the test, seeking to carry out at least three tests to estimate service capacity [25, 53, 54].

*Animal Reproduction in Veterinary Medicine*
