Seasonal Effect

Question 1

How does the season (daylight hours) affect horses?

Answer 1

• Mares foals in spring
  
  • ~10.5 - 12 mo gestation
  • therefore conceive in spring (lengthening days)

Question 2

How does the season (daylight hours) affect ewes?

Answer 2

• Ewes lamb in spring
  
  • ~21 week gestation (5mo)
  • Conceive in fall (shortening days)

Question 3

How does light detection work in seasonal breeders?

Answer 3

• 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”

Question 4

How are the hormone levels different during Equine Anestrus?

Answer 4

• 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

Question 5

What changes are seen in mares during the spring transition?

Answer 5

• 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

Question 6

How can horses be bred early?

Answer 6

• 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

Question 7

How is ovine Estrus affected by the photoperiod?

Answer 7

• 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

Question 8

How can Sheep be bred out of season?

Answer 8

• 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

Question 9

What are the male sexual behaviors? what controls these behaviors?

Answer 9

1. Courtship
2. Copulation

• Both under control of testosterone
• Brain undergoes sexual differentiation during a short period of time near puberty - necessary for normal sexual behavior

Question 10

What animals are stimulated by visual cues for sexual behavior?

Answer 10

bovine and equine

Question 11

What animals are stimulated by olfactory cues for sexual behavior? how do males effect females and vice versa?

Answer 11

• 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

Question 12

What are the olfactory cues that are being detected for sexual behavior? how are these detected?

Answer 12

• 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

Question 13

What is Sex Odeur Aerosol?

Answer 13

• 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

Question 14

What are hormones regulate female sexual behavior? effects?

Answer 14

• 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

Question 15

What mating behaviors are expressed by a bull?

Answer 15

• 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

Question 16

What are the mating behaviors of cows/heifers?

Answer 16

• Form sexually active group (SAG) that stays in visual contact with bulls

Question 17

What is the mating activity of bovines (bull and heifer) when together?

Answer 17

• Bulls will “sham mount” a female to test her willingness to “stand” to be mated
  
  • greatest stimulus is a female that is immobile

Question 18

How long does the spring transition take in mares?

Answer 18

6 - 12 weeks

Question 19

Would breeding during the spring transition phase in mares be successful?

Answer 19

NO

Question 20

What sexual behavior is exhibited by stallions?

Answer 20

• 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

Question 21

What are the different sexual behaviors exhibited by mares?

Answer 21

• 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

Question 22

What sexual behaviors are exhibited by boars?

Answer 22

• When placed near females - will “chant”, salivate profusely, nuzzle the flank and head-rest on the back

Question 23

How impactful is the first mating on a boar? how is the outcome controlled?

Answer 23

• 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

Question 24

Why has AI replaced pen-breeding in pigs?

Answer 24

• 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

Question 25

What sexual behaviors are exhibited by sows/gilts?

Answer 25

• 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

Question 26

What is the “tie” in canine mating?

Answer 26

• 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