Reproductive and Maternal Behavior of Livestock - Genetics and the Behavior of Domestic Animals - page 161

during the late fall and winter months, even in subtropical and tropical envir-
onments ( Chenoweth, 1994b; Randel, 1984; Taylor et al., 1995 ).
Although mounting behavior is an important component of the cattle
reproductive behavioral repertoire, it is not restricted to reproductive pur-
poses only. Young calves show mounting behavior as early as 1 week of
age, although this becomes more common as puberty approaches. In prepu-
bertal animals, mounting is probably associated with play behavior as well
as mimicry of adult behavior. In addition, mounting behavior plays a strong
social role in cattle in which dominant animals tend to mount those which
are more subordinate.

Male Reproductive Behavior
Bulls are sexually attracted to females primarily by the sight of females
standing to be mounted. In fact, this attraction can be elicited by any
inverted U structure which resembles the rear end of the female
( Buechlmann, 1950 ). This is useful in semen collection centers which often
employ steers as mount animals to reduce the risk of venereal disease trans-
mission ( Chenoweth, 1981 ). Pheromonal action is also useful in helping bulls
to detect estrous females, although close physical proximity is probably nec-
essary for this to occur in cattle ( Jacobs et al., 1980 ). Flehmen behavior,
which is often displayed during courting, is considered to primarily represent
an investigatory, rather than a cognitive process ( Chenoweth and Landaeta-
Hern´ndez, 1998 ).
The most important special sense that range bulls employ to detect estrous
females is vision ( Chenoweth 1986; Chenoweth and Landaeta-Hern´ndez,
1998 ). This is facilitated by formation of a sexually active group (SAG) com-
prising females in late pro-estrus and estrus which, although constantly in
motion, usually stays within visual contact of bulls ( Chenoweth, 1981;
Williamson et al., 1972 ). Females newly in estrus tend to be most attractive to
bulls, and sexual interest can be restored in satiated males by the presentation
of new stimuli. Bulls will form hierarchical groups in which social status
influences relative reproductive success ( Chenoweth and Landaeta-
Hern ´ ndez, 1998 ). For young bulls, a learning process may be necessary
before they achieve competence and confidence in their mating ability ( Boyd
et al., 1989 ; Landaeta-Hern ´ ndez et al., 2001 ). Once a bull achieves success-
ful mounting, copulation usually follows rapidly with ejaculation being com-
pleted within 1 2 seconds of intromission ( Seidel and Foote, 1969 ).

Bull Libido/Sex-Drive
In this discussion, the terms sex-drive and libido are used synonymously and
refer to the eagerness or willingness of the bull to mount and service a
female ( Chenoweth, 1981 ). Bull libido can be measured in a relatively