Ansc 3133 Postnatal Growth with Genetic Influences on Growth

Phase IV:

-90-95% of additional growth is fat -5-10% of gain is muscle

Heterosis or Hybrid Vigor Influences

phenotypic appearance or production performance of an animal

Protein coding sequence-

the part of gene that encodes protein (change of even one nucleotide can result in significantly changed protein function)

with Expected Progeny Difference (EPDs) Some genetic merit can be compared within breeds across

different herds or flocks

Pigs carrying Halothane gene are sensitive to

halothane anesthesia and stress

Heritability Estimate Use:

-Selection of individuals for breeding programs -Response to selection indicates change in a trait that can be made through controlled breeding

Inherent Factors Affecting Animal/Carcass Growth & Composition:

-Species -Breed or Strain -Sex -Selection/Domestication -Other Genetic Factors

Genotype:

-The genetic constitution of an individual organism -DNA sequence -The effects of extrinsic factors on phenotype pass to the intrinsic factors

Animal Growth and Development Chemical components:

-Water -Protein -Lipids -Ash (minerals) -Carbohydrates -Vitamins

Porcine Stress Syndrome (PSS) Mutated RYR1 is involved in the Alteration in

Ca2+ homeostasis, hypermetabolism, intense muscle contraction, and malignant hyperthermia (resistant training)

with Porcine Stress Syndrome (PSS) RYR1 - Ca2+-channel protein in the skeletal muscle sarcoplasmic reticulum releases

Ca2+ to cytoplasm

Enhancer activity-

Often located far away from genes. Does not code protein but regulates promoter activity

One of earliest criteria for selecting animals-

Genetic potential to produce milk (dairy type) or meat (meat type)

Expected Progeny Differences (EPDs) is the

expected difference in performance of a sire's progeny compared to the performance of another sire's progeny

Regulation of gene expression is subjective to regulation by

extrinsic factors

Intact males grow

faster for longer

Domestication was done through

genetic selection

Different breeds differ in ability to

grow

Phenotype-

Genotype (intrinsic) plus environmental factors (extrinsic)

more realistic growth curve-

Growth spurts may occur at sporadic intervals

Quarterhorses-

HYPP, PSSM, mutation in the MYH1 gene to a muscle-wasting condition most commonly seen in Quarter horses

Mutated RYR1 is called

Halothane gene

Inherent Factors Affecting Animal/Carcass Growth & Composition- Selection/Domestication:

-Wild vs. Domesticated -Many changes through genetic selection +Took thousands of years -Muscle distribution differences +Wild animals have greater % of muscles in proximal pelvic limb -Muscle fiber types- red vs white?

Layer vs. Broiler:

-genetic selection for muscle growth has resulted in some change in distribution of muscle (in contrast to livestock species). -Industry successful in increasing proportion of breast meat as proportion of carcass muscle

Extrinsic Genetic Poultry Factors:

-maternal factors -intestinal microbiome -housing and hygiene -infections -medications and supplementation -temperature -feed -breed/genetic backgrounds

DNA methylation:

-negatively regulates gene expression -Methylation of cytosine -Blocks binding of gene transcription factor to the promoter -Induces histone deacetylation

alternative means of segmenting a typical growth curve:

-phase I -phase II -phase III -phase IV

Phase II:

-represents ~75% of total growth -organs reach mature size -bone growth completed -muscle growth maximal -fat accumulates slowly

Gene Expression Regulation - Long Noncoding RNA Functions:

-transcriptional activation -transcriptional regression -enhancer RNA -scaffolding protein for chromatin remodeling complexes -regulation of RNA splicing -sequestration of mRNA

Gene Expression Regulation- Epigenetic Micro mRNAs:

-~22 nt RNAs completely complementary with the target sequences within mRNAs -Block translation through inducing mRNA degradation by RNA-induced silencing complex (RISC)

Higher Expected progeny differences (EPD) value indicates higher

individual genetic merit for a specific trait

In all livestock species EXCEPT PIGS, castrated males are

intermediate to females

Holstein-

large frame, dairy type

Charolais-

large frame, meat type

Heritability Estimates Range from

low of 0.01 to high of 0.70

Porcine Stress Syndrome (PSS) is Also known as

malignant hyperthermia

Within a species, breeders have placed selection pressure on different traits- led to development of

many breeds or strains in all livestock species

Larger framed animals are generally later

maturing

DNA methylation-

methyl group (an epigenetic factor found in some dietary sources) can tag DNA and activate or repress genes

Regulation of gene expression by Transcription factors is done through interactions with

promoters and enhancers

Heritability is the

proportion or fraction of phenotypic variation resulting from additive genetic effects

Porcine Stress Syndrome (PSS) is usually associated with

ryanodine receptor 1 (RYR1) recessive gene mutation

Lower heritability estimates mean slower progress in

selection for desired traits

Expected Progeny Differences (EPDs) is Designed to compare

sires WITHIN THE SAME BREED

Angus-

small frame, meat type

Heterosis or Hybrid Vigor is Due to increased heterozygosity of genes due to mating of parents with different genes, resulting in

some genes expressing dominance over the allele paired gene trait

Heritability estimates for different traits vary with

species and specific population that is sampled

Variations in DNA sequence result from

spontaneous mutations

Heterosis or hybrid vigor indicates the performance of progeny is

superior to the average of the parents for a trait

histone modification-

the binding of epigenetic factors to histone "tails" alters the extent to which DNA is wrapped around histones and the availability of genes in the DNA to be activated

Heterosis or Hybrid Vigor equation % H = (O / P - 1) * 100:

-% H is degree of hybrid vigor -O is average of crossbred offspring -P is average of the parents

Phase I:

-15-20% of total growth -slow growth of all tissues -tissue growth order is organs > bone> muscle

Phase III:

-80-90% of growth attained -organ and bone growth complete -80-90% of muscle deposited -rapid accumulation of fat begins

Gene Expression Regulation - Histone Epigenetic Modifications:

-At the tails of histone proteins -Acetylation and phosphorylation - activation -Methylation and ubiquitination - activation and repression

as genetic companies and seedstock producers attempt to further improve productivity:

-Becomes increasingly evident that improvement of some economically valuable characteristics not possible -Improvement of others is rapid and fruitful

Myostatin Gene Mutation Examples:

-Belgian Blue bull -Bully whippet dog

Animal Growth and Development Physical components:

-Bone -Lean -Fat

Extrinsic factors:

-Climate -Stress -Nutrition -Exogenous substances (ionophores, growth agents) -Handling

Heritability genes:

-Combination of genes inherited from parents -Degree to which a trait is inherited can be determined through heritability estimates

Factors Affecting Animal/Carcass Growth & Composition- Species vary in:

-Composition -Ability to deposit different tissues -Relative proportion of each body part

General Animal Growth and Development steps:

-Conception -Birth -Self-accelerating postnatal growth phase -Inflection point (change in growth emphasis) -Self-retarding post natal growth phase -Maturity

Regulation of gene expression by Epigenetic modifications:

-DNA methylation -Histone modifications -microRNAs, long non-coding RNAs

Protein Synthesis- Amino acids -> Proteins:

-DNA transcribed into messenger RNA (mRNA) -Translocation of mRNA into sarcoplasm -Translation of mRNA into protein by transfer RNA (tRNA) -Post-translational modifications of protein -Transportation of protein -Degradation of protein

Blue Butt Pigs:

-F1 cross of Hampshire and Yorkshire -Terminal for meat- Hampshire -Maternal for mothering ability- Yorkshire

Tiger Striped Cattle:

-F1 cross of Hereford and Brahman -Hybrid vigor +Heat tolerance -Brahman +Meat grade - Hereford +Longevity - Brahman

Frame Size:

-Function of skeletal growth & maturation -Continuum from small to large

Another important trait during early selection programs was overall body size:

-Function of skeletal size = frame size -Large frame, small frame

Implementing Genetic Influences on Growth and Development:

-Genotype is expressed through phenotype -Breeding selection programs +Prediction of genetic merit +Mating systems to produce superior animals

Heritability calculation:

-H^2 = Vg/Vp -H^2 is heritability -Vg is genetic variance -Vp is total, or phenotypic, variance +The total of Vg and Ve (variance due to external factors)

Porcine Stress Syndrome (PSS) Mutated RYR1 results in:

-High lactic acid level in muscle -Lead to pale, soft, exudative (PSE) meat

Heritability Estimate Ranges Product, carcass, or composition traits:

-Highest heritability at >40% -Marbling, ribeye (or loineye) area, subcutaneous fat thickness, tenderness, protein concentration

Double Muscled Cattle Issues:

-Large body size coincides with size reduction of most vital organs +Dystocia (calving difficulty) +Susceptibility to respiratory disease, urolithiasis, lameness, heat stress +Reduced feed intake capacity so diet must have greater nutrient density -Modified myofiber types lead to lower capillary density and more glycolytic metabolism -Less intramuscular fat (marbling), but higher unsaturated fatty acid content

Heritability estimates:

-Lowest for reproductive traits -Medium for production traits -Highest for product or composition traits

Heritability Estimate Ranges Reproductive traits:

-Lowest heritability at 0 to 20% -Fertility, birthing difficulty, conception rates

Heritability Estimate Ranges Production or growth traits:

-Medium heritability at 20 to 40% -Liveweight gain (ADG), feed conversion or efficiency (FE, G:F), weaning weight

Double Muscled Cattle Due to mutation in myostatin (MSTN) gene, which encodes growth regulating factor myostatin:

-Member of TGFβ superfamily -Inhibits myogenesis (satellite cell/myoblast proliferation and protein synthesis)

different animal types:

-Milk vs. Meat -Mothering vs. Meat -Layer vs. Broiler -Wool vs. Meat -Hardiness vs. Quality -Wild vs. Domesticated

Gene Expression Regulation- Long Noncoding RNA:

-Partially complementary with target sequence (both mRNA and DNA) -Non complementary sequence for binding with other proteins such as transcription factors -Have different functions

Heritability Estimate Use equation R = h2 * S:

-R is response to selection; the amount of gain that is made when mating the selected parents -h2 is heritability estimate -S is selection differential or the difference between the selected individuals and the herd or flock average for the trait

Double Muscled Cattle Hypertrophy, not double the total number of muscles, results in ______% increase in total number of fibers

40

Heritability Estimates can be 1 to _________% on percentage basis

70

Usually Expected Progeny Differences (EPDs) also has an _________________________ value associated with the Expected Progeny Differences (EPDs)

ACCURACY

Promotor activity-

At the 5' end of the gene. Does not code protein, but determines the gene expression level

Heterosis Effect on Dog Longevity-

Crossbred dogs outlived purebred by 1.2 years on average

Intrinsic Factors - Promotor Activity-

Do not code protein, but determines the gene expression level through recruiting transcription factors which attracts or repels RNA polymerase

Evolution has played important role in development of species (speciation)-

Increased selection pressures intermingled with evolution, ultimately responsible for species differences

_________________________ animals will reach heavier live weights at a given compositional maturity or fat endpoint

Large-framed

Intrinsic Factors - DNA Sequence-

Single Nucleotide Polymorphisms

cumulative growth curve-

Wt of animal expressed as total at any given time

Extrinsic Genetic Factors regulate gene expression through

actions on the intrinsic machinery

Acetylation and phosphorylation-

activation

Methylation and ubiquitination-

activation and repression

Expected progeny differences (EPD) are useful only for comparisons among animals and not as an indication of the

amount of progress in a mating system

Heritability estimate of 35% (h2 = 0.35) means 35% of total phenotypic variation is due to heredity and 65% due to

environmental factors

Expected progeny differences (EPD) can be estimated for a specific animal to predict the

average performance of its offspring

Epigenetics-

changes in organisms caused by modification of gene expression responding to external factors rather than alteration of the genetic code itself

Slow growing animal won't reach same wt as fast growing animal at the same

chronological age

Function of the gene-

distinct sequence of nucleotides forming part of a chromosome