Veterinary Physiology-III

SEXUAL BEHAVIOUR

• This behaviour mainly involves courtship and mating. Hormones mainly control it though some amount of psychological (learned) factors is also involved.
• Female farm animals are restless during estrus (heat) and have intense sexual desire. Mares in estrus sequel and urinate profusely. Cows and sows will stand when mounted by other females (this behaviour is not exhibited by mares and ewes).
• Males detect females in heat by sight or smell. Courtship behaviour involves a linked sequence of stereotyped behaviours, e.g. mating behaviour of a bull begins with his approaching the genital area of a female (probably in response to pheromones), nuzzles the vulva and the underside of tail, which elicits urination in the 4ow. The bull then licks the vulva, the underside of the tail followed by flehmen behaviour. In response, the cow signals her willingness to be mounted. Sexual behaviour is influenced by social facilitation; members of the opposite sex stimulate each other hormonally.
• The stallion bites or teases the mare in heat, preparatory to mating. The boar nudges the sow around the: head and nose and "grunts". The rooster will spread one of his wings and perform a dancing act before the hen.
• Male sexual behaviour is influenced by the social environment, sensory ability and sexual stimuli and testosterone. Female are sexually active during estrus and it is regulated by estrogen. During proestrus and estrus of dogs, vaginal secretions contain pheromones called as methyl-p-hydroxy benzoate, which is responsible for attraction of males.
• Boar taint- urine of boar contains 5d androsterone. This causes the sows in estrus to assume a reflex known as rigidity reflex- mating posture in sows.

View animation 

Pheromones are the cause of two classic phenomena in mice

• Whitten Effect
  • When a male mouse is introduced into a group of female mice, it causes synchronization of estrus because of release of GnRH.
• Bruce Effect
  • When a male mouse is introduced into a cage of an already bred mouse it leads to failure of pregnancy because introduction of male mouse blocks the release of prolactin.
• In domestic animals similar to the Whitten effect, Ram effect is noticed. Introduction of a ram into a flock of anestrus ewes, leads to synchronization of estrus due to the release of GnRH.

Physiological mechanism/neuroendocrine basis

Role of nervous system in sexual behaviour

• Hypothalamus- by releasing GnRH, regulates FSH and LH and, estrogen: as a part of limbic system, involved in regulating sexual behaviour.
• Spinal cord and medulla- to maintain postural reflexes; mating posture during copulation.
• Parasympathetic nervous system- involved in erection of penis and clitoris; parasympathetic nerves supply almost all reproductive organs.

Motor patterns during courtship/mating/copulation

• Sexual arousal
• Sexual display
• Erection
• Penile protrusion
• Mounting
• Intromission
• Ejaculation
• Dismounting
• Refractoriness

• Sexual behaviour in males
  • Sniffing, licking the female, Flehmen reaction, nuzzling-rubbing the female body surface with nose

• Sexual behaviour in females
  • During estrus- restless, loss of appetite, attempting to mount, bellowing Sniffing- particularly the scrotal region of male Mating posture- allow the males to mount

Species-specific characters

• Cow and goats- bellowing and bleating; mount on other animals and allow other animals to mount; goat turns its head back during mounting; sheep - flattening of tail and also turns itsfoack.
• Sows - grunting sound produced from guttural pouch; lordosis- binding the back like an arch is the mounting posture specific in pigs; cocking(erection) of ears are seen.
• Mares - frequent urination, winking of vulva and clitoris, vaginal mucus exudation

Duration of courtship and copulation

• Sheep- less than a second to few seconds.
• Cattle- few seconds
• Horse- 40 seconds
• Pigs- 2-5 minutes (minimum) to 20-30 minutes (maximum)

Factors affecting sexual behaviour

• Breed end strain affect genetic factors - variation in libido.
• Physiological factors- These are determined during fetal and postnatal life depending on neflnatal androgen.
• Environmental factors- These have more effect on male than the female. Males become more active when new females are introduced in a herd. Season and climate affect the sexual behaviour. Sexual drive is less during the hot climate.
• Previous experiences

Abnormal estrus patterns

• Nymphomania - also called "Buller cow"- cow acts like bull. It is a hereditary- disorder in cattle; cystic follicles are common in this condition, which produces more estrogen leading to persistent estrus; voice and behaviour will be like male.
• Split estrus - common in mares. There will be estrus for short period with interruptions.
• Quite estrus - there will not be estrus signs but ovulation will occur and if inseminated it will conceive.
• Prolonged estrus - also common in mares with prolonged estrus far. a period of 1-6 weeks.
• Weak estrus — estrus remains for a short period and conception rate is less.

Abnormal sexual behaviour in males

• Homosexuality - males exhibit mounting on male; common when young males/ are housed in pen
• Hypersexuality — increased sexual activity; increased frequency of copulation
• Hyposexuality - few animals fail to mount and abnormality in ejaculatory patterns
• Autoerotic behaviour - self sexual arousal; seen in stallions- it rubs its penis against hypogastrium; in bulls- pelvic movements of penis in and out of preputial orifice resulting in ejaculation