Reproduction exam

How does application of genetic information begin?

data collection 

• identifies what needs to be improved

1. abnormalities 

2. Traits

What is the calculation based on the performance of individual and close relatives?

Breeding value - estimated value of an individual as a parent

What calculation allows us to compare animals? (half of breeding value)

Expected Progeny Difference (EPD)

Definition of Expected Progeny Difference

predicted difference in performance between individual offspring and offspring’s contemporary group

What are the traits EPD looks at?

• Birth (weight, type, gestation length)

• Growth (weight at and/or time to benchmarks, frame size)

• Maternal (milk production)

• Terminal (carcass merit)

• Reproduction (scrotal circumference, litter size)

• Behavior (maternal instinct, docility, speed, agility)

What is accuracy a measure for?

Reliability 

What is the range for accuracy?

0-1

• 1 = high accuracy/confidence

• 0 = low accuracy/confidence

What increases accuracy

Increased information

How does progeny numbers influence accuracy?

• Males typically have a higher accuracy than females

• older animals have higher accuracy than young animals

Define Chromosome

Large molecules containing DNA; made of genes

Define Gene

Segment of chromosomes composed of DNA

Define DNA

Two strands of sugar phosphate Al backbone with bridges of nitrogen bases

Define Nucleotide

Sugar, phosphate and one of 4 nitrogen bases

Define Genotype

Genetic make-up, heritable traits.

Why are genotypes (the expression of genes) profitable?

• Transmit traits from parent to offspring.

• Key principle of breeding systems.

Define inheritance

Passing traits from parent to offspring

Define alleles

Alternative forms of a gene that affect the same traits

Define Gametes

Reproductive cells that carry half of the parent’s genetic code; only a single allele for each gene (A or a)

What are the 2 things a gamete consists of?

Sperm and Oocyte

define homozygous

Alleles that match at a specific location (AA or aa)

Define heterozygous

The alleles differ at a specific location (Aa)

Why do we want homozygous offspring?

Reduced variability (Same result every time)

Define haploid

Copy from mom and dad

Define a capital allele (A) and a lower case allele (a)

A - dominate trait

a - recessive trait

Which coat color is dominant and which is recessive?

Black coat color is dominant (R)

Red coat color is recessive (r.)

Which allele takes precedence if an animal is heterozygous (Rr)

The dominant trait (black coat color)

Define Codominance

Both alleles are expressed

Ex. Red (R) X White (W) = Roan (RW)

Define Incomplete dominance

Intermediate; no dominance, so heterozygotes appear as an intermediate rather than a combination

Ex. Black (R) X White (W) = Grey (G)

Define sex-influenced

Phenotype expressed differently between sexes

In males, what is the dominant and recessive for horns?

Horns (H) is dominant, polled (h) is recessive

In females, what is the dominant and recessive for horns?

Polled (h) is dominant, horns (H) is recessive

Define sex-limited

• Traits unique to one sex

• Both sexes carry the genes but only one capable of expressing

What major trait is limited to only females

Milk Production

Define Sex-linked

Genes found only on X or Y Chromosomes

male chromosomes

XY

Female Chromosomes

XX

X linked genes affect who?

Males and Females

Are males or females more impacted by sex-linked traits?

Males

Why are males more impacted by sex linked traits?

Males have only one X chromosomes, so the recessive X linked conditions are more commonly expressed.

Examples of X linked genes

Red/green colorblindness, hemophilia, Duchenne muscular

Who are affected by Y linked traits?

Males

Why are there fewer Y linked chromosome genes than X linked?

Y chromosome is smaller

Why are Y linked traits difficult to determine?

• only occur in males

• Occur in all sons of affected males

• Not occur in daughters of affected males or their offspring

Define selection

Determining which individuals reproduce

What are factors in natural selection?

• sustainability

  • weak/injured will be less likely to reproduce

• Opportunity

  • exposure to more potential mates (geography or behavior) will be more likely to reproduce

What are the factors of Artificial selection?

• Management

1. decisions humans make to regulate opportunity (includes culling, castrating, and specified mating) 

Define qualitative traits

classified into groups

Examples of qualitative traits

• coat color

• Horned vs. Polled

Define Quantitative traits

Numerically measured

What are some example of quantitative traits

• marbling

• Muscling

Define Heritability (h²)

Impact of additive genes

Why will people pay more or less depending on heritability?

Confidence in desirable traits being passed down to offspring will cause the consumer to spend more.

What are the factors in calculating Heritability?

• Selection differential

• Heritability of a trait

Define selection differential

Mean advantage of parents over mean value of population

ex. litter size of 11 when the mean is 7 = differential of 4

What is a highly heritable trait? (0.4-0.6)

Carcass merit traits

• ribeye

• marbling

What is a moderately heritable trait? (0.2-0.4)

Growth traits

What is a lowly heritable trait? (0.0-0.2)

Reproductive traits

Define Inbreeding

mating closely related individuals

Benefit of inbreeding/linebreeding

Increases homozygous gene pairs

Concerns with inbreeding

• decreases reproduction and hardiness

• decreases variation

• decreases vigor and production

• increases the expression of potentially detrimental recessive genes

What are the genetic diseases of sheep/goats?

Scrapie, entropion, spider lamb syndrome, foot rot, internal parasites

What are the genetic diseases of Cattle?

Curly Calf Syndrome

What are the genetic diseases of swine?

PSS (porcine stress syndrome)

What are the genetic diseases of Horses?

• Hypp (hyperkalemic periodic paralysis Disease)

• PSSM (Polysaccharide Storage Myopathy)

Define Linebreeding

A form of inbreeding using repeated crossings to ancestors

What is the goal of linebreeding

maintain influence of outstanding ancestor (s)

Define outbreeding

mating less closely related animals than the general population

• can include crossing within a breed or between breeds

benefits of outbreeding

• increases heterosis (heterozygosity) 

• increases hybrid vigor and performance

Define crossbreeding

to use complementarity of traits

• The mating of two individuals from different breeds

What is the goal of crossbreeding?

• offspring outperform the average performance of the parents

• hybrid vigor

• heterosis

Why do we give a shot of prostaglandin to females that don’t breed?

• Resets cycles

• synchronizes females 

Why synchronize estrus?

• scheduled calving

• More heat per breeding season

• problem cows are identified

• Early conception

• Increased heifer management

Why is scheduled calving important?

Makes management easier

• weather

• Forage availability and quality

• labor

Why is more heat per breading season important?

• increased pregnancy rates

• increased cow productivity

Why is problem cow identification important?

• Cyclicity can be induced

Why is Early conception important?

• Higher weaning weights 

• more uniform calf crop 

Do we wait to A.I for a longer or shorter period of time if the animal’s estrus is longer?

the longer the estrus, the longer we wait to A.I

The timing of estrus and ovulation is what kind of practice?

Management

• how am I going to synchronize them?

How do we store sperm?

We freeze it

• They stop moving. The more energy they use, the quicker they die

Cattle in estrus intervals

21 days

Sheep in estrus intervals

17 days

Swine in estrus intervals

21 days

Horse in estrus intervals

21 days

cattle estrus duration

12 hours

Sheep estrus duration

24-36 hours

swine estrus duration

48-54 hours

horse estrus duration

6 days

Why is the pig’s estrus longer than the cow and sheep

litter bearing species 

Why do we breed before ovulation?

To give sperm a headstart because men are slow

Ovulation time in cow

10-18 hr. end estrus

Ovulation time sheep

18-24 hr. end estrus

Swine ovulation time 

30-36 hr. end estrus

What is required for estrous synchronization?

• Management 

• Feed resources

• Facilities 

• Uniform product

• utilize labor 

What does the liver do to hormones?

Metabolizes them

What is the ram effect?

a natural synchronization method that synchronizes females spontaneously using sight and smell stimuli

• in heat from the presence of a male

The ram effect only works on what kind of females?

Females with a corpus luteum

What is Gonadotrophins used on?

Mature females

What is Gonadotrophins function?

stimulates the anteritor pituitary

Trade names of gonadotrophins 

Fertagyl, cystorelin, OvaCyst

What do we use prostaglandins on?

Cycling females