Animal Breeding lectures

traits description

when we describe animals we characterize them in terms of appearance or performance of a combination of both. Examples of coat color, weight, etc

traits

are any observable or measurable characteristics of an animal

observed trait

one that describes the appearance of an animal with examples such as coat color, size, muscling, and leg set

measurable trait

one that can be subjectively measured and reported with examples such as weaning weight, speed, and staple length

phenotype

is an observed category or measured level of performance for a trait in an individual.

genotype

genetic makeup of an animal or better described as an animal's genotype provides the genetic background for its phenotype

what are animal breeders concerned with

changing a population genetically so not only want to know phenotype of animal but also genotype

what does phenotype equal

genotype plus environmental effects

environmental effects

the external factors (nongenetic) that alter an animal's phenotype

What are animals with similar genotypes said to be

same biological type

biological type

classification for animals with similar genotypes for traits of interest with examples such as tropically adapted cattle or draft horses

what does favorable changes in genotypes result in

improved phenotypes

what is the best animal

none

system

group of interdependent component parts with examples of combustion engine, an animal industry, the beef industry, a cow, a large ranch, or a small farm

animal category of system

contains the characterizes genotype or genotypes

physical environment of system

contains those elements to which humans have very little control such as the weather, soil type, and altitude, which may have a large effect in range cows and a small effect in a confined hog operation

fixed resources of system

include items like size of the farm, opportunity to grow supplemental feeds and available labor

management of system

involves the policies of the farmer such as amount of feed, heath care, and culling rate

economics of system

refers to the cost for farm inputs such as feed, labor, and supplies and the prices of farm outputs such as sales of animals

system components

interact with each other

interaction

dependent relationship among components of a system in which the effect of any one component depends on other components present in the system.

to determine best genotype

must have knowledge of the environmental, managerial, and economical components and how they interact with genotype to affect profitability

how to determine the traits of importance and optimal genotypes for those traits

thorough analysis of the system with an understanding of the interactions among the many components of the system

genotype by environment interactions (G x E)

dependent relationships between genotypes and environments in which the difference in performance between two or more genotypes changes form environment to environment. An example would be animals that are genetically adapted to a temperate environment compared to animals genetically adapted to tropical environment.

for many species genotype by environmental interactions play what role

a critical role in determining the most appropriate biological type for a given environment.

what are interactions always

graphable

Breeds

races of animals within a species and different breeds are often genetically adapted to different environments

genotypes are sometimes

superior under a particular kind of management

Pyramidal structure of breeders

suggests a flow of germ plasm, which is genetic material in the form of live animals, semen, or embryos. Ideally, breeders at each level produce animals that will be of the greatest demand to their customers at the next level down, thus breeders at all levels tailor their breeding objectives to meet the needs of end users

breeding objective

general goal for a breeding program which is a personal idea of what constitutes the best animal

commercial producer

an animal breeder whose primary product is a commodity for public consumption

purebred

group of animals wholly of one breed or one line

line

group of related animals within a breed

seedstock

animals whose role is to be a parent or in other words contribute genes to the next generation. historically have been purebred but they do not have to be purebred

Intermediate optimum

average level of performance that is optimal in terms of profitability and or function.

what is the purpose of animal breeding

it is not to genetically improve animals once they are conceived but to improve animal populations, to improve future generations of animals

population

group of intermating individuals. the term can refer to a breed, an entire species, a single herd or flock, or even a small group of animals within a herd

two tools to improve population

selection and mating

selection

we decide what animals become parents, how many offspring they may produce, how long they remain in the breeding population

mating

we decide what selected males will be mated to which selected females

two types of selection

natural and artificial

natural selection

selection that occurs in nature independent of deliberate human control. it affects wild and domestic plants and animals since all animals with lethal genetic defects typically never live to become parents

which selection is the most familiar type

natural selection

artificial selection

selection that occurs under human control

two types of artificial selection

replacement selection and culling

replacement selection

process of determining which animal becomes parents for the first time. normally young animals may not be limited to young animals for example using a proven diary sire the first time in your herd

culling

process that determines which parents will no longer remain parents

which selection is of primary interest to animal breeders

artificial selection

are replacement and culling similar phrases in the process of improving livestock populations

yes

what is the idea behind selection

let individuals with the best set of genes reproduce so the next generation will have on average a more desirable set of genes than the current generation

what animals are said to have the best breeding values

animals with the best set of genes

breeding values

value of an individual as a genetic parent

phenotypic selection

the simplest form of selection as if demonstrates how selection works

phenotypic selection definition

selection based solely on an individual animal's own phenotype

heritability

measure of the strength of the relationship between breeding values and phenotypic values for a trait in the population

what happens when heritability is high

phenotypes are good indicators of breeding values

what happens when heritability is low

phenotypes selection is usually ineffective

what is an example of low heritability

fertility as whether an animal conceives usually has more to do with environment rather than breeding value

fertility

the ability to conceive or to impregnate

how is selection done using information on relatives

using the assistance of pedigree data or progeny data

pedigree data

information of the genotype or performance of ancestors and or collateral relatives of an individual

collateral relatives

relatives that are neither direct ancestors nor direct descendants on an individual example is siblings, aunts, uncles, nieces, and nephews

progeny data

information on the genotype or performance of descendants on an individual

why do we use information from relatives

individual cannot provide direct information and we use them to increase the accuracy of our predictions

accuracy

measure of the strength of relationship between two values and their predictions and when is is high, selection is usually effective

what has occurred in most meat, dairy, and fiber producing species genetic prediction technology

has evolved to where objective predictions of breeding values are available

genetic predictions

area of academic animal breeding concerned with measurement of data, statistical procedures, and computational techniques for predicting breeding values and related values

EBV

estimated breeding values

EPD

expected progeny differences

PD

predicted differences

ETA

estimated transmitting abilities

MPPA

most probably producing abilities

PC

probable change

ACC

accuracy values

when are sire summaries used to find outstanding sires

in beef, dairy, and swine

sire summaries

lists of genetic predictions, accuracy values, and other useful information that can be used to find the most outstanding sires in the breed

how are traits often affected

by a single gene or multiple genes

polygenic trait

one that is affected by many genes. no single gene has an overriding influence on the trait such as weaning weight and fertility

what do we rely on with polygenic traits

phenotypic performance, breeding values, and accuracy to help characterize the genotype for this trait

simply inherited trait

affected by only a few genes such as a horned/polled cattle from European origin

between breed selection

provides a way of using breed differences to make very rapid genetic change which can be done for many traits because the breed differences are very large therefore, this will allow a breeder to produce a more rapid genetic change than by using within breed selection.

when is between breed selection useful

crossbreeding and composite breed production

mating

where we decide which selected males will be mated to which selected females

mating system

set of rules for mating

why do breeders use mating systems

produce offspring with extreme breeding values in order to increase the rate of genetic change, to make use of complementarity, and to make use of hybrid vigor

complementarity

an improvement in the overall performance of offspring resulting from mating individuals with different but complementary breeding values

crossbreeding

mating sires of one breed or breed combination to dams of another breed or breed combination. this produces a crossbred and results in hybrid vigor or heterosis

hybrid vigor/heterosis

increase in the performance of hybrids over that of purebreds

Hybrid

an animal that is a combination of species, breeds within species, or lines within breeds

inbreeding

mating of relatives

inbreeding depression

reverse of hybrid vigor- a decrease in the performance of inbreeds most noticeably in traits like fertility and survivability

why is inbreeding good sometimes

concentrating genetics

corrective mating

mating designed to correct in their progeny faults of one or both parents

Gene

basic physical unit of heredity consisting of a DNA sequence at a specific location of a chromosome

DNA

deoxyribonucleic acid and is a very complex molecule that forms the genetic code for all living things

chromosomes

come in pairs and is one of a number of long strands of DNA and associated proteins present in the nucleus of every cell

humans

23 chromosome pairs

cattle

30 chromosome pairs

dogs

39 chromosome pairs

homologs

one of a pair of chromosomes having corresponding loci