Nutrient Partitioning
Where are nutrients directed in early life?
Growth and Survival
What Threshold needs to be reached for puberty to occur?
Body Weight Threshold
What type of breeder is primarily affected by environmental factors?
Seasonal Breeders (sheep and horses)
BLANK from the male can influence the female system and age that puberty is reached
Pheromones
EASY MONEY
When GnRH is secreted, what two hormones are also secreted? Where are they secreted from?
GnRH causes LH and FSH secretions from the anterior pituitary gland
What do GnRH neurons sense to know if there’s enough energy?
Glucose Levels
In cattle, the threshold is generally what percent of their mature body weight?
55% - 65%
Name an Animal (or two) that is primarily influenced by environmental factors
Sheep and Horses
What factor is female:female influencing?
The density of females in a population
What does it mean, in terms of nutrients, when the body weight threshold is met?
Nutrients/energy can be directed towards functions outside of growth and survival
What are high frequency GnRH pulses controlled by?
Glucose and Free Fatty Acids
High glucose & free fatty acids = GnRH secreted more frequently = reproduction is moving
Low glucose & free fatty acids = GnRH secreted less frequently = reproduction is not moving
What is a more accurate indicator of puberty than body weight, and name the factor that can affect it?
Body Condition Score/Body Composition/Overall Fatness
Genetics can affect this! (some breeds of cows are inclined to put on more muscle)
If an ewe lamb is born in the fall (short photoperiods), will they reach puberty earlier or later?
Later! ~ 1 year
Sheep are short-day breeders, and they would not be mature enough to reach puberty before the short photoperiods turn into long photoperiods.
In pigs, does a higher female density increase or decrease puberty age?
Decrease!
The high density can increase pheromones in the environment, leading to a lower puberty age
What are the different types of energy that glucose, free fatty acids, and leptin provide?
Glucose: short-term energy
Free Fatty Acids: long-term energy
Leptin: signals energy storage
What is Leptin and how does it relate to reproduction?
Leptin is a peptide hormone secreted from adipose (fat)
High levels of leptin = supports reproduction
Low levels of leptin = suppresses reproduction
What are the environmental cues that can influence development of GnRH neurons?
Season of Birth and Photoperiod
If an ewe lamb is born in the spring (longer photoperiods), will they reach puberty earlier or later?
Earlier! ~ 6 months
Sheep are short-day breeders, so by the time the shorter photoperiods come they have matured enough for puberty to happen
Does the presence of male pheromones increase or decrease the age of puberty in females?
Decrease!
Scenario: you are trying to decrease the age that your sows reach puberty, so you decide to place your male pig near your sows.
Should you place your male in the same pen as your females or should you place him right outside of your female pen?
Outside!!!
Letting them have contact could be huge safety issue!!!
We want to keep our girls safe and celibate (until the time is right) ;)
What is 2-deoxyglucose (2DG) and how does it effect LH?
2-deoxyglucose blocks the body from using glucose as energy
When 2DG is present, GnRH pulses are limited, and that causes a decreases in LH surges
What are the social cues that can influence the development of GnRH neurons?
BONUS: what animal is really affected by them?
Density of Females and Presence of a Male
BONUS: Pigs (other examples in rodents, sheep, and cows)
Even though cats are induced ovulators, can the age they reach puberty still be affected by environmental factors?
Yes... I guess?
Apparently cats are influenced by photoperiod (longer photoperiods trigger more GnRH surges), and this can cause them to go a full year before reaching puberty if the photoperiod is wrong at birth.
But, if the cat is healthy and has reached the body weight threshold, puberty can still occur even if the photoperiod is "wrong".
What animals are proven to be affected by social cues?
Pigs, sheep, rodents, and cows
TESTING YOUR MEMORY
Average age that a female Holstein will reach puberty
12 months