Seasonal Effect Flashcards
How does the season (daylight hours) affect horses?
- Mares foals in spring
- ~10.5 - 12 mo gestation
- therefore conceive in spring (lengthening days)
How does the season (daylight hours) affect ewes?
- Ewes lamb in spring
- ~21 week gestation (5mo)
- Conceive in fall (shortening days)
How does light detection work in seasonal breeders?
- Photoperiod influences prolactin secretion via its affect on melatonin secretion by pineal gland
- If light is detected during a specific time period, day is perceived as “long”
How are the hormone levels different during Equine Anestrus?
- GnRH concentration in hypothalamus is low
- LH and FSH secretion by anterior pituitary are reduced
- Ovaries are “inactive” (few follicles - little follicular maturation)
- Steroid production is low
- nearly undetectable estradiol and progesterone
- Same result in males
What changes are seen in mares during the spring transition?
- GnRH concentrations begin to increase shortly after winter solstice
- FSH levels rise as GnRH ⇡
- Number and size of ovarian follicles increase (detectable by ultrasound)
- first few large follicles do NOT ovulate
- First Ovulatory follicle is accompanied by an estradiol and LH surge - leading to ovulation
How can horses be bred early?
- Increase day length with artificial lights will return seasonally anestrous mares to reproductive competence
- Light therapy doesn’t shorten the transition phase (i.e. phase with anovulatory follicles) it just moves it early in the year
- Strategy - add artificial light during evening hours starting in Nov and December
How is ovine Estrus affected by the photoperiod?
- Pattern of light from summer solstice to autumnal equinox is most critical
- Follicular waves continue during anestrus
- Follicles do reach ovulatory size, but do NOT ovulate
- Estrogen production is low
- The first LH surge of the season is not followed by ovulation - but progesterone from luteinized follicles rises
- The second LH surge of the season is accompanied by ovulation and estrus
- First LH surge of the season is NOT followed by ovulation - but progesterone from luteinized follicles rises
- Second LH surge of the season is accompanied by ovulation and estrus
How can Sheep be bred out of season?
- Gestation length and speed of lamb growth should allow for 2 pregnancies per year (spring and fall)
- Some breeds are easier to “trick” into breeding during shorter days
- Block exposure to morning or evening light by housing in light-tight barns (difficult)
- Expose to additional artificial light for 8-12 wks, followed by 8-12 wks of short days
- Short day = 6-8 hrs shorter than long days
- Or melatonin implants for 4+ wks
- Rams need to be exposed to light treatment also
- In addition to light therapy:
- withhold contact with rams until ready to breed
- Treat with CIDR P4 sponge or CIDR for 12 days with eCG injected at P4 removal
What are the male sexual behaviors? what controls these behaviors?
- Courtship
- Copulation
- Both under control of testosterone
- Brain undergoes sexual differentiation during a short period of time near puberty - necessary for normal sexual behavior
What animals are stimulated by visual cues for sexual behavior?
bovine and equine
What animals are stimulated by olfactory cues for sexual behavior? how do males effect females and vice versa?
- porcine, ovine, equine
- Male-effect on females
- can stimulate earlier puberty, induce ovulation, increase speed of sperm transport in female tract
- Female-effect on males
- identification of the presence of females in estrus
- Female-effect on males
- identification of the presence of females in estrus
What are the olfactory cues that are being detected for sexual behavior? how are these detected?
- Pheromones - airborne chemicals released by urine / feces or secreted by cutaneous glands
- Flehmen response - particular type of lip curling, adopted when examining scents, helps expose vomeronasal organs and draws scent molecules back toward it
What is Sex Odeur Aerosol?
- held ~50cm from the head of a sow with the nozzle directed at the nose
- Spray for 2 seconds
- if gilt/sow is in estrus the standing reflex will be exhibited
What are hormones regulate female sexual behavior? effects?
-
Estrogen - necessary for mating
- high when a follicle is mature and able to ovulate a viable egg
-
Progestogens - inhibit mating behavior
- high during pregnancy and during stages of estrous cycle w/out a fertilizable egg
What mating behaviors are expressed by a bull?
- Libido = desire to mate
- Mating ability is the ability to successfully mate
- Both appear to be influenced by genetic
- Bulls house in groups will establish dominance hierarchy quickly
What are the mating behaviors of cows/heifers?
- Form sexually active group (SAG) that stays in visual contact with bulls
What is the mating activity of bovines (bull and heifer) when together?
- Bulls will “sham mount” a female to test her willingness to “stand” to be mated
- greatest stimulus is a female that is immobile
How long does the spring transition take in mares?
6 - 12 weeks
Would breeding during the spring transition phase in mares be successful?
NO
What sexual behavior is exhibited by stallions?
- Includes: vocalization, olfactory, and tactile investigation, and the flehmen response
- When teased - stallion begin sexual behaviors within 2 minutes
- respond more vigorously when provided more than one stimulus mare
- Can have “psychological breeding issues”
- Ritual bound
- Bored - need variety
- Preference for certain types of mares
What are the different sexual behaviors exhibited by mares?
- Estrus in a pasture:
- will approach stallion and exhibit sexual behavior - urination, deviation of tail, standing still
- Diestrus in pasture:
- will avoid stallion and exhibit aggression if he persists - squeal, strike, bite
- Mares occasionally exhibit estrous behaviors during the anovulatory portions of the year
What sexual behaviors are exhibited by boars?
- When placed near females - will “chant”, salivate profusely, nuzzle the flank and head-rest on the back
How impactful is the first mating on a boar? how is the outcome controlled?
- Confidence - intimidation by a group of gilts or being beat-up by a large sow can ruin a young boar for future mating
- Young boars should be exposed to one gilt of similar size that is in a strong standing heat
- Do not hurry the first mating
Why has AI replaced pen-breeding in pigs?
- Boars show a strong preference for some females in pen-mating
- I/e/ boars won’t breed all the available females - will breed a few multiple times
What sexual behaviors are exhibited by sows/gilts?
- Male presence is necessary for females to show obvious estrus behavior
- Take the female to the male - she searches for the male
- Even in heat - female may run away from the boar and he will follow her
- Mating stance - will stand immobile with back arched and ears erect
What is the “tie” in canine mating?
- After ejaculation - the dog dismounts but the penis is ‘locked’ in the vaginal vault by the swollen bulbus glandis and the muscular vulva
- Dog and bitch position posterior-to-posterior
- Lasts for a few minutes to over an hour