ANSC 1401 - Growth and Development: Key Terms and Definitions

Growth

result of many physiological processes that produce meat

Meat

most important source of high quality protein in human diet

Growth rate of animals

important factor determining the economic return from an animal enterprise

Scientists growing understanding

have been able to successfully alter and improve development, boosting efficiency and profit margins.

True growth

net increase in body protein, amount synthesized over that lost

Fat, bone, water

can be increased or decreased any time in animals life, not included in growth definition

True growth definition

definition of true growth does not fit everyday usage of term growth

Typical growth curve for population/individual (early)

increase in cell numbers, little increase in weight

Typical growth curve for population/individual (later)

greater increase in weight and then maturity. Could be bacterial or animal numbers.

Measuring growth in layman terms

Growth=Weight/time or W2-W1/T2-T1

Cattle: A steer was 265 days old and weighed 650 lb when put on feed. In the feedlot, it gained 350 lb in 120 days. It then weighed 1,000 lb and was 385 days old.

ADG= 1000-650lb/120d= 2.92 lb.

WDA=1000lb/365 days= 2.60 lbs

ADG

average daily gain

WDA

weight per day of age, includes birth weight

Swine- 231st day of year a feeder pig weight 40lb, it was fed until 326th day of the year when it weighed 230lb. ADG?

ADG=(230-40)/326-231= 2.00 lb

Are higher or lower ADG's and WDA's more desirable?

if an animal gains faster, it goes to market sooner

Facility use (ADG, WDA)

Higher= using facilities over a shorter time, less overhead expenses

Profit (WDA and ADG)

higher is more profitable

compensatory gain period

happens after dieting

Growth of cells

hyperplasia, hypertrophy

hyperplasia

increase in number of cells, mainly prenatal

Hypertrophy

increase in size of cells, fattening, weight lifter, callipyge sheep

Periods or phases of growth

Prenatal, postnatal

Prenatal

in uterus between fertilization of ovum and birth

Prenatal (Litter weight)

lower birth weights are caused by larger litters, smaller younger mothers, and nutrition of mother.

Who profits from compensatory gain?

cow producer-running yearlings- feedlot operator-slaughterer

Feedlot buyers

pay more per pound for thin calves than those showing bloom

Hyperplasia occurs?

almost always prenatally

Postnatal growth

all hypertrophy

Exceptions of growth

rodents, much less developed at birth than farm animal babies

Preweaning

still getting mothers milk

Post weaning

fending for self

Being in larger litter

less space and nutrients

Small uterus and small mother

less space to grow and less uterine space

younger mother

is still growing

Stages of development

Egg+sperm-> fertilized ovum-> Morula-> Blastocyst-> embryo-> fetus

Blastocyst

fluid filled cavity

Morula

16-32 cells-

Which trimester does the most fetal weight growth occcur?

3rd Trimester

Postnatal

after birth, relative growth rate declines with age, but accelerates after puberty begins

Stages of postnatal

preweaning and post weaning

Preweaning (Calves, pigs, lambs)

Calves:7mnths, Pigs: 3-5 wks, Lambs:2-6mnths

Preweaning weight

weaning weight affected by mothers milk, creep feed, pasture, genetics, age of dam, sex, castration, diet.

Sow diet

expensive, early weaning of pigs may be practiced

Post weaning (Postnatal)

from weaning to slaughter or to entry into breeding herd

Post weaning market weights (steers and heifers)

Steers:1,300lb avg, heifers:1,200 lb avg.

Post weaning market weights (barrows and gilts)

both 270lb avg

Post weaning market weights (lambs)

135lb avg

Factors affecting post weaning gain

amount and type of feed, genetics, sex, age, climate

what declines after puberty?

ADG

Effect of uterine size on offspring

similar genetic makeup but vastly different birth weights

Calf weaning weight peak

cow age of 6 years with little difference at 5,6, and 7. Mainly a milk yield affect.

Climate

can have a large effect on post weaning gain

Sex factor (Post weaning)

male: castrates, Female: hormones

External factors affecting growth

nutrition and environment

internal factors affecting growth

genes, hormones

Hereditary factors

genetic constitution of individual

Hereditary factor weight

Mature weight vs growth rate vs birth weight

Hereditary factor (uterine space)

Differences are not as large for other large animal species, can be partially influenced by external factors.

Hereditary factors (list)

weight, growth rate, uterine space, sex

Nutrition (nutrient priorities)

nervous, skeletal, muscular and adipose tissues.

Flow of blood containing nutrients

Nerves, Bones, Muscles, Fats

Fat deposition priorities

internal fat>subq fat>intermuscular fat>

Genetic potential

cannot be achieved with inadequate nutrition

Hormones

Secretions of endocrine glands that are carried in blood to sites where the are used.

Adrenaline

fight or flight, get them on the truck before they get their tails up

growth hormone (GH)

somatotropin, from anterior pituitary, can be made by genetically engineered microbes.

GH

species specific, affects CHO and fat metabolism, stimulates N retention and protein synthesis

GH shortage

dwarfism

GH oversupply

acromegaly (giantism)

GH in dairy cows

can use to increase milk production, increases stress and shortens time in herd.

Thyroxin

Thyroid gland, regulates BMR. Under control of thyrotropic hormone of anterior pituitary

Hypothyroidsm

Too little, causes our motors to run too slowly. early in embryonic life causes disproportionate dwarfism.

Hypothryoidism symptoms

reduced BMR, lethargy, low blood sugar, lowered N retention, fattening, dull hair coat, less cold tolerance.

Hyperthyroidism

too much, causes motors to run too fast. Pop eyed condition.

Iodine and temperature effects

iodized salt, goiter

Gonadal hormones

from ovaries or testes

Estrogens

from ovaries and adrenals, close epiphyseal plates and slow growth.

Estrogen variable effects across species

reduce rat growth, fatten chicks, increase growth and decrease fat of sheep and cattle. Increase protein synthesis

Implant compounds

DES, MGA, prevent estrus and increase ADG about 10% in heifers

Androgens

from testes and adrenals, increase growth and decrease fattening.

Androgen effect

greater effect on females than castrates

Castration effects

behavior change, fattening, lower gain, less lean, higher meat quality, more long bone growth

Progesterone

from corpus luteum on ovary, growth stimulant

Heifers

fatten faster than steers and steers faster than bulls

Swine

barrows are fatter than gilts

Environment

heat, cold, humidity, elevation

Diseases

death loss and reduced productivity

Maturity

fattening, muscle deposition ceases except when muscles are loaded such as in weight lifting.

What closes at maturity?

epiphyseal diaphyseal junction on long bones, break or spool joints on lamb carcasses

What happens at maturity?

No more increase in height, slow daily gain, decrease in body functions and metabolic rate

Hens

lay the most eggs first year and steadily decline each year after

Body weight vs metabolic rate

Heavier weight= lower MR

Senescense

process of growing old, onset of old age

life span vs growth rate

shorter growth period=shorter life span and vice versa

Calories expended during lifetime

nearly same for all animals except man. Larger size= lower BMR

BMR

basal metabolic rate

Aging

less hormone secretion, reaction time slows, strength and speed decline, recovery time increase, skin less elastic, body wears out.

Theories of aging

genetic mutations, immunological, developmental, biochemical

Genetic mutation aging

mutations accumulate and interfere with body functions

Immunological aging

reduction in AB production= older more prone to disease condtions