Growth, Development, and Body Composition Flashcards
Define growth
an increase in body mass or physical size
How do we measure growth?
- weight
- height
- length
- body composition
How do we calculate average daily gain (ADG)?
W2-W1/T2-T1 (in days)
ex. A horse weighs 300 lbs, and 2 weeks later it weighs 342 lbs. What is the ADG for the horse?
342-300/14 = 3 lbs./day
What are the ways that growth occurs or changes?
Hyperplasia
Hypertrophy
Atrophy
Tumors
Define hyperplasia
increase in cell numbers (early, prenatal stages)
Define hypertrophy
increase in size of cells (after birth)
Define atrophy
when cells shrink
Define tumors
abnormal localized cell growth without normal control mechanisms
What are the stages of prenatal growth?
- Blastocyst: occurs after fertilization; nutrition is from uterine secretions and the egg itself
- Embryonic: cell differentiation into tissues and organs; very small increase in weight
- Fetal: major growth in weight and composition, nutrition is from maternal bloodstream
Describe the prenatal growth curve
an exponential positive growth
x axis: days after conception
y axis: body weight
What factors influence prenatal growth?
- Size of dam
- number of fetuses
- Implantation site in uterus (a more individual factor in growth)
- nutrition level of dam
- disease status of dam
- genetics
- sex of the animal
Describe the postnatal growth curve
sigmoid shape (tilted S)
x axis: time
y axis: weight
self accelerating: the initial exponential phase of growth
self-inhibiting: growth slows due to restraints
What is the function of thyroxin?
Thyroxin is produced by the thyroid gland and it targets general body tissues. It sets the metabolic rate
What is the function of insulin in terms of growth?
Insulin is produced by the pancreas and it targets body cells to promote division
What is the function of adrenal corticoids in terms of growth?
Adrenal corticoids are produced by the adrenal glands they target general body tissues.
Mineralocorticoids regulate concentrates of minerals, especially Na and K
Glucocorticoids help regulate carbohydrate conversions and metabolism
What hormones regulate growth of specific organs?
Thyrotropin
Adrenocorticotropic hormone
Gonadotropins (FSH and Lutenizing Hormone)
What is the function of thyrotropin?
Thyrotropin (aka thyroid stimulating hormone) is produced by the anterior pituitary gland and it targets the thyroid to stimulate secretions.
What is the function of adrenocorticotropic hormone?
ACTH is released by the anterior pituitary to target the adrenal glands to stimulate secretions.
What are gonadotropins and what do they do?
Gonadotropins are produced by the anterior pituitary and they target the gonads.
Two examples are follicle stimulating hormone and luteinizing hormone.
What is the function of growth hormone?
Growth hormone, also know as somatotropin, is a protein hormone that causes growth everywhere. It is released by the anterior pituitary.
What factors limit growth?
- Nutrition (poor nutrition limits growth)
- Disease
- Parasites
What sets the maximum mature size and rate of growth?
Genetics sets the maximum mature size and rate of growth while all other factors determine the proportion of the maximum that will be obtained.
How can we sum the growth curve?
- Different organs and tissues grow at different rates
- Different organs and tissues grow at different times
- Distribution of body parts and body composition changes during life of the animal
What are the four phases of the growth curve?
- Short time after birth
- Early growth
- Middle growth
- Late growth
What occurs during the short time after birth phase?
the head, neck, and legs grow and are the largest proportions of the body
bone, muscle, and vital organs grow
What occurs during early growth?
the body increases in length
bone, muscles, and vital organs continue to grow
What happens during middle growth?
there is an increase in the depth and width of the body
bone, muscle, and fat grow
What happens during late growth?
the depth and width of the body continues to increase
the loin (in the middle of the back) and hindquarters develop
muscle and fat grow
Know the body composition chart
bone: shallow slope
fat: somewhat exponential before halting
muscle: steeper slope
carcass: levels out
What happens to the proportions of an animals tissues as they age?
As an animal ages and grows, its overall percentage of fat goes up while its percentage of bone and muscle decrease.
How do the sex hormones affect mature size?
Males are larger than females
M>F
How do the sex hormones influence rate of growth?
Males grow faster than castrated males which grow faster than females.
M > CM > F
How do sex hormones influence the rate of fattening in cattle and sheep?
Females fatten faster than castrated males, which fatten faster than males.
F > CM > M
How do sex hormones influence the rate of fattening in swine?
Castrated males fatten faster than females, which fatten faster than males.
CM > F > M
How do sex hormones influence the feed efficiency for animals.
Feed is more efficient for males, then castrated males, then females.
M > CM > F
In cattle, which carcasses tend to be leaner?
Male carcasses are leaner than castrated male and female carcasses due to the presence of testosterone.
M > CM, F
In cattle, which carcasses tend to be fatter?
Female and castrated male carcasses are fatter than male carcasses since they do not produce as much testosterone.
M < CM, F
Which systems are prioritized for use of nutrients?
- nervous tissue and vital organs
- skeletal
- muscle tissue
- fat
- reproductive (in a pregnant female, reproduction will take priority 2)
Why do highly productive animals often not display reproductive functions like entering heat?
High producing animals sometimes do not enter heat or show that they are in heat because the least energy from nutrients is directed toward reproduction unless the animal becomes pregnant.
What do stunted animals tend to have larger heads compared to the rest of their bodies?
Nutrients are mostly directed toward the nervous tissue and vital organs like the brain.
What is compensatory growth?
a period of accelerated growth that follows a time of nutrient restriction
What factors affect compensatory growth?
- how severe the restriction was
- how long the restriction lasted
- what time in the animal’s life did the restriction occur?
When does an animal typically reach their maximum growth?
at puberty
How does growth trend over time?
The general form of postnatal growth shows that growth rate is initially slow, increases to a maximum, then slows, and, if ultimate size is reached, will cease.
What tissues grow first and in what order since age of conception?
nervous tissue and vital organs grow first and at the fastest rate
skeleton grows at second fasted rate
muscle third
fat fourth
all are growing at the same time but at different rates
