ANSC 201 OLVER 2025 material

lactation functions

provide nourishment, immunity, quick energy

lactation location

1. pectoral region - humans and elephants

2. inguinal region - cows

3. abdominal region - sows, mouse, dog (animals w litters)

arrangement of bovine udder

udder is divided into 4 separate quarters, each independent in its milk producing function

flow of milk out of the udder

-alveoli ( epithelial cells synthesize milk, myoepithelial squeeze milk out)

-lobules

-lobes

-ducts

-gland (udder) cisterns

-teat cistern

-streak canal/exit

ovine (ewe) gland arrangement

sheep, similar to bovine except there are only 2 glands

caprine (nanny) gland arrangement

goat, similar to ovine except the udder and teats are funnel shaped

equine (mare) gland arrangement

horse, 2 glands, 2 lobes, 2 streak canals per teat

teats = broad & flat

swine (sow) gland arrangement

10-14 glands located in parallel rows extending the length of the abdominal wall from the pectoral to inguinal region, there are several lobes per gland, 2 streak canals, 2 teat cisterns per teat

other multiparous animals similar to swine lactation arrangement

dog usually has 10 glands, 8-22 streak canals

cat has 8 glands, 4-8 streak canals

streak canals are arranged in a circular pattern on the surface of the teat

growth and development of the mammary gland - prior to birth

Prior to birth: mammary streak; primary sprouts (later- ducts) ; teats

growth and development of the mammary gland - from birth to onset of puberty

From birth to onset of puberty: streak canal and teat (nipple)

growth and development of the mammary gland - From onset of puberty to beginning of first pregnancy

From onset of puberty to beginning of first pregnancy: major ducts get larger

growth and development of the mammary gland - during pregnancy

During pregnancy:

a. Early: large ducts and development of smaller ducts

b. Late: alveoli and lobes are forming

growth and development of the mammary gland - during lactation

During lactation: alveoli begin functioning. After peak there is a gradual decline in number of functioning alveoli.

Peak = when the animal reaches the most milk

growth and development of the mammary gland - After termination of lactation

After termination of lactation: alveoli, lobes and lobules shrink/ regress (dry up). This process is called Involution.

Lactation- alveoli fully developed, then shrink

Involution: secretory tissue and ductile tissue regress (dry up)

growth and development of the mammary gland - subsequent gestations and lactations

Subsequent gestations and lactations:

Begin: alveoli begin functioning again

After Peak: gradual decline in number of functional alveoli

End: involution occurs

Cycle repeats with each gestation and lactation

somatotropin

mammary grow prior to puberty, growth isometric in first stages, increasing at same rate as other body parts

estrogen

contributes to duct and cistern growth at beginning of puberty, growth is allometric (faster than rest of body)

progesterone

contributes to the development of alveoli (secretory tissues) and lobes

prolactin

essential for milk production and secretion (maintaining lactation)

still in chickens (function = lay on eggs)

glucocorticoids, somatotropin, ACTH

with prolactin initiates lactation and maintenance of lactation

thyroxin

increases metabolic rate of tissue in mammary gland (mammary tissue has very high metabolism)

parathyroid hormone

regulates Ca levels in the blood, less active when animal is not lactating, if offspring - PTH is low, parturient paresis (milk fever), causes animal to not stand due to muscle contractions regulated by Ca gradient, Ca is not metabolized to meet needs

adrenalin

if mother is frightened, vasoconstriction (narrowing of blood vessels) will occur, reduced oxytocin flow

termination of gestation and initiation of lactation theory

gestation - inc progesterone levels, decreases prolactin release and decreases prolactin effect

just prior to parturition - decrease progesterone, increased estrogen, increased prolactin release and effect

milk synthesis process

1. filtration - water

2. selective absorption - vitamins, minerals

3. cell metabolism - casein, lactose, milk fat

blood precursors

1. water

2. lactose

3. proteins

4. lipids

lactose synthesis

lactose is synthesized from glucose

monogastrics - blood

ruminants - from blood and liver (gluconeogenesis from propionic acid)

lactose synthetase - enzyme only found in lactating tissue, derived from alpha-lactalbumin (protein)

**lactose is the solid component closely tied to yield

milk protein synthesis

caseins and whey protein are synthesized in mammary gland from amino acids

milk lipid synthesis

monogastric - blood lipids + glucose = milk fat

ruminant - blood lipids + acetic acids = milk fat

milk mineral and vitamin synthesis

mainly absorbed from blood stream

milk secretion

movement of milk into lumen of the alveolus

cycle of events:

1. synthesis

2. secretion

3. rest/regeneration

rate of milk secretion

- fast: low pressure

- slow: moderate pressure

- stop: high pressure (bc its full - pushing back)

**frequent milk removal keeps pressure low so there is fast rate of secretion

milk formation - lipid and protein process

fat - fat globule forms in epithelial cell

protein - made in golgi vesicle, is released with water

Milk let down

milk let down causes by stimuli (suckling or sounds), hypothalamus tells posterior pituitary to release oxytocin, oxytocin travels through the blood to the udder

**if cow is startled or stressed, epinephrine will release, BV's will constrict and not let milk down

milk removal types

1. suckling by young

2. hand milking

3. mechanical (historical with can or modern day with robots)

milk teat cistern is pinched or squeezed out

metaboilc burdens of lactation

beginning - negative energy balance (weight loss)

later lactation - zero energy balance

end lactation - positive energy balance (weight gain)

management - want to minimize negative energy balance at beginning to prevent obesity at the end (animal able to loose weight during partrition)

lactation persistance

how well animal maintains her milk production levels throughout lactation

older animals - higher peak, less persistent

young animals - lower peak, more persistent

**younger animals have lower peak because they direct their energy to growth and development

mastitis

inflammation of the mammary gland

most costly disease in dairy management

many causes: organism entering teat, infection

results in lower milk production

**not udder edema

What ligament separates the mammary into right and left halves?

median suspensory ligament

how can bacteria enter the mammary system most easily?

the teat end

For each pound of milk produced, how many pounds of blood must pass through the udder?

400lbs

Name 3 major items that pass through the inguinal canal

blood, lymphatic system, nerves

what are some functions of the lymphatic system

1. destroy bacteria

2. detoxifying metabolites

3. returns interstitial material fluid to the bloodstream

near the time of parturition, animals often accumulate large quantities of lymph in their mammary systems. what is this condition called?

udder edema

The streak canal secretes what fibrous protein that helps prevent the invasion of mastitis-causing organisms?

keratin (acts as plug)

what closes the teat end between milkings?

sphincter muscle

-keratin plugs teats if animal is dry

Microscopic milk-producing units contained in lobules are called what?

aveoli

where does milk collect between milkings?

lumen

what cells are directly affected by oxytocin in the mammary system?

myoepithelial cells

what things may cause a release of epinephrine (adrenalin) into the blood stream of an animal and decrease the effectiveness of oxytocin?

stress, constriction of ducts, rough handling

phenotype vs genotype

Phenotype: physical appearance

Genotype: genetic makeup

Pyrimidines vs purines

Pyrimidines: Cytosine, Thymine, Uracil

Purines: Adenine, Guanine

RNA composition and structure

-sugar is ribose

-thymine is replaced by uracil

C - G, A - U

replication

ensures precise inheritance

base pairing guarantee this result, when 2 strands of DNA are separated, another identical double helix is formed

mutation

when replication is not exact due to chemical changes in DNA, takes generations to occur

migration

bringing new genotypes through breeding stock into a population

selection

using some animals more than others as parents

natural selection - controlled by nature

artificial selection - controlled by management

How is the information in DNA made?

synthesis of animo acids and proteins

the products of genes are protein molecules via synthesis of amino acids

they are the directions for organization and metabolism of cells

codes for amino acids

Triplet codes (codons through RNA)

Sequences of 3 bases

64 possible codes

Several different triplet codes may designate the same amino acid

types of chromosomes

1. sex chromosomes - (X or Y) one pair, sperm and egg have haploid number

2. autosomes - in body cells, number of pairs varies by animal, every body cell has diploid number

# of pairs of chromosomes in body cells of animals

chicken - 39

horses - 32

cattle - 30

cat - 19

dog - 39

sheep - 27

humans - 23

swine - 19

transcription

synthesis of an mRNA molecule by copying from a DNA template

translation

production of animo acids from RNA codon sequences

protein synthesis DNA

DNA template --> transcription (in nucleus) --> mRNA strands --> translation (in ribosome) --> proteins

types of RNA

mRNA - messenger, carries info about particular proteins, directs AA and protein synthesis

rRNA - essential for ribosomal structure and function

tRNA - identifies codons in mRNA, moves AA to proper place in polypeptide chain

locus

Location of a gene on a chromosome

homologous chromosomes

chromosomes with the same loci and structure

alleles = diff forms of same gene

diploid vs haploid

diploid - body cells

haploid - gametes

**independent assortment of chromosomes happens during meiosis

inheritance characteristics

controlled by single gene

phenotypes easily described

phenotypes are discontinuous

codominance

A condition in which both alleles for a gene are fully expressed

incomplete dominance

Cases in which one allele is not completely dominant over another

homogametic sex

mammal - XY or XX (male determines)

birds/reptiles - ZZ or ZW (female determines)

quantitative inheritance characteristics

1. many genes involved

2. phenotypes described by measurements

3. continuous distribution of phenotypes

**bell curve

effects of alleles

effects from alleles are equal and additive

there is no dominance expressed between alleles

contributing alleles will be designed by capital letters

phenotype = genotype in ideal conditions

effects from alleles are equal and additive

there is no dominance expressed between alleles

contributing alleles will be designed by capital letters

phenotype = genotype in ideal conditions

occur between corresponding genes on homologous chromosomes

Heterosis (overdominance; hybrid vigor)

heterozygous show better results than either of the 2 homozygoes (Aa is better than AA or aa), occurs in crossbreeding

gene/environmental interactions equation

phenotype= genotype + environmental effects

**must attempt to standardize environmental effects in genetic evaluations

formula for genetic progress

genetic gain/year = (heritability * selection differential) / generation interval in years

**can change by having younger pregnant females, IVF, AI

heritability (h^2)

explains the degree that genes control expression of that trait (% of differences caused by gene effects from generation to generation)

range of 0-1

fitness/health = low values

production/birthweight = high value

selection differential

(reach) the degree of selectivity used, the difference in a trait btwn a population mean (average) and the mean (average) of the animals selected from that population producing the next generation

males can be more selective - have a larger influence

ex) flock averages 4kg of wool

average of males selected = 8kg (8-4=4kg)

average of females selected = 6kg (6-4=2kg)

selection differential = (8-4) + (6-4) / 2 = 3kg

generation interval

average age of parents when offspring are born

**can be affected by management

evidence of genetic change

many examples

size in horses (draft vs miniature)

meat to bone ratio in turkeys

backfat in swine

genetic selection methods

1. tandem

2. independent culling levels

3. selection index

tandem

selection for one trait at that time, then selection for a second trait once desired level of first trait is achieved

VERY SLOW - might lose progress in first trait when selecting for second

independent culling levels

Minimum standards for traits undergoing multiple-trait selection

selected = animal hits all minimums

disadvantages - Animals failing to meet any one standard are rejected regardless of merit in other traits, traits are weighted

equally

selection index

several traits are evaluated and expressed as one trait, most effective, can factor in price, correlation, can weigh traits

grades vs registered

registered- recorded in a breed association and meets criteria outlined by org

grades- may be about the same genetically, but is not registered

inbreeding

mating of individuals who are more related than the general population

increases homozygosity - ex) dec repro, dec growth, inc stress, inc disease

**disadvantage = could have hidden recessive gene

linebreeding

milder form of inbreeding that tends to emphasize one outstanding ancestor

outbreeding

females are mated to unrelated males

3 types - species cross, crossbreeding, outcrossing

** reduces inbreeding, increases heterozygosity

species cross

2 diff species mated, widest possible form of outbreeding

ex) mule, beefalo

crossbreeding

mating 2 animals of same species but different breeds

maximizes heterosis and breed complementation

ex) german shepherd + golden retriever

outcrossing

mating unrelated animals within the same breed

ex) both german shepard but from diff families

selection of animals for mating - general comments

-can more intensively select males

-sometimes best matings can yield poor results because of random assortment

-heritabilities of traits must be considered

-traits with economic value are important

correlations

range of -1.0 to +1.0

positive - traits vary directly together

negative - traits are inversely related

not related = 0

What is the difference between high quality and low quality protein?

A high quality protein possesses all of the essential amino acids in appropriate quantities and proportions whereas a low quality protein may be deficient or void of one or more essential amino acid.

Why, in general, are milk proteins better for the growth of a young mammal than corn proteins?

Milk proteins are high quality for most young animals to grow at a normal rate while corn proteins are inferior and can't grow at a normal rate.

What is the typical protein percentage required in the diets for most young growing animals?

20-24%

Can an animal be deficient in protein even though it is fed a high protein percent diet?

Yes, if the protein is limiting amino acid (not essential).