Chapter 11 Male Mating Behavior

A. Factors related to male participation in reproductioon in natural breeding:

a. Dominance (superiority of social hierarchy)--+ Correlation between these
b. Libido --------------------------------------+ Mating | traits is low. Therefore,
c. Ability to copulate -------------------------+ behavior | each trait should be
d. Ability to produce fertile semen ------------+ evaluated separately.

B. Mating behavior: influenced by genetic and environmental factors

C. Factors for evaluation of mating behavior

a. Time to first copulation after placing the male with an estrous female
b. Number of copulations in a specified time
c. Number of copulations before sexual exhaustion( loss of libido)
d. Time required to regain mating disire after exhaustion

D. Sequential events of male mating behavior

Sexual arousal ¡æ courtship (sexual display) ¡æ erection ¡æ mounting ¡æ intromission ¡æ ejaculation ¡æ dismounting

E. Courtship patterns by species: See FIGURE 11-1

a.Vocalization: Bull: bellow; Stallion: neigh; Ram and Boar: grunt
b.Sniffing and licking of female genitalia and urine
c Extending neck and curling upper lip: in bull, ram, and stallion
d Tactile stimuli as licking, bunting and biting: in most males
  * Dominant male: separate estrous females from other males and females

11-1 Regulation of mating behavior

11-1-1 Hormonal influence

A. Testosterone (T): Inc. sexual activity to a certain threshold, but not accentuate the response:

* Experimental evidences for T influence:

a. Reduced sexual activity following castration: can be restored by testosterone infusion, but only to its activity level before castration
b. Seasonally reduced sexual activity of stallion, ram and buck: associated with seasonal reduction in T
c. Summer reduction in T and sexual activity in bull and boar: related to reduced metabolic rates ¡ç reduced thyroxine

B. Interaction of T with experience

a. Males castrated before puberty: Only some mounting behavior continue.
b. Males castrated after sexually experienced: Copulate for several years, but with less frequent activity and no ejaculation from involuted accessory glands

C. Interaction of T with senses (sight etc.) and pheromones: See FIGURE 11-2

Figure 11-2 Interaction of factors that regulate sexual behavior in bulls and other species 

11-1-2 Social and sexual interaction

A. Social interaction: Prepubertal social interaction with others of same species: important to attain superior sexual ability, though males isolated in short period show normal behavior.

B. Sexual interaction: Males reared in isolation or without females:low libido or permanent impairment; Sexually inexperienced bulls: More training is necessary for collecting semen in AI centers

11-1-3 Senses

A. Sense of smell: Most important in males as in females:

a. Pheromones in urine of estrous females: stimulatory to males
b. Sprinkling urine of estrous females: effective for mount training in bulls and stallions
c. Distance for males to detect pheromones: different by species

B. Sense of sight: Important to male's sexual arousal:

a. Sight of mounting activity, sexually active group, immobile castrate, and padded dummy mount etc: stimulate mounting behavior in bulls (strong factor: immobility)
b. Mature bulls wearing blindfolds: copulate normally, but males blind from birth: delayed sexual maturity

C. Sense of touch: Important to normal copulatory behavior:

a. Temperature: best response from approx.45¡É in artificial vagina for bull
b. Pressure: important to semen collection in boar and stallion

D. Sense of hearing: important in females

E. Effects of all senses: additive; Senses interact with experience and conditioned reflexes

11-2 Erection and ejaculation

11-2-1 Erection

A. Under control of autonomic nervous system

B. With sexual excitement, blood is pumped into by way of longitudinal carvenous spaces, and temporarily trapped in cavernous areas: Corpus cavernosum penis: a closed system with no venous outlet at distal levels, and erector muscle pulls penis against pelvis and aids in erection by compressing veins of penis; and corpus spongiosum penis

C. Fibroelastic penises : in bull, ram buck and boar, except for stalliion

D. Pressure in corpus cavernosum penis before ejaculation: 15,000 mm Hg in bulls and 6,500 mm Hg in stallion

11-2-2 Ejaculation

A. Ejaculation = ejcection of semen: spermatozoa + seminal plasma B. Initiation of ejaculation: By stimulation of sensory nerves in glans penis:triggers a series of peristaltic contractions of smooth muscles in reprodcutive tracts.

C. Ejaculation time, and volume and sperm concentration of ejaculate: See TABLE 11-1 Segmented ejaculate in boar and stallion: Sperm-free ¡æsperm-rich ¡æ sperm-poor segments: sperm-free segment is discarded in boar AI.

11-3 Maintaining libido (in bulls)

A. Provide balanced diet:

a. Underfeeding in young bulls: reduce libido and dec. semen production
b. Overfeeding in mature bulls: more likely to be a problem

1) Foot, leg and joint problems ¡æ shorten reproductive life
2) Reduce libido
3) Inc. sperm abnormality

B. Protect from diseases and injuries: not a problem of frequent incidence Hoof care and moderate exercise: lengthen reproductive life

11-3-1 Sexual exhaustion

* Sexual exhaustion: A physical probelm from loss of libido, in dominant males, during heavy breeding season under range conditions: regain libido after adequate rest.

11-3-2 Sexual satiety

A. Sexual satiety: A mental problem = sexual indifference, from being exclusively used for semen collection in AI center

B. Cure and prevention

a. By changes in collection procedure: 1) changing teaser animal using a second teaser, 2) moving to another collection area, 3) using an estrous female, and 4) sprinkling urine from estrous female

b. Careful to use artificial vagina properly not to make bulls unpleasant from: 1) too hot or too cold AV, 2) excessive bending of penis, or 3) grasping penis