ANSC 107 1nd Edition Lecture 11 Outline of previous lecture I Evaluation of slaughter animals a Yield grade b Quality grade c Dressing II Factors influencing value of slaughter animals a Dressing percent b Fatness c Marbling d Muscling e Carcass weigh and age Outline of current lecture I Qualitative Quantitative II Inbreeding III Line breeding IV Outcrossing V Cross Breeding VI Future Learning objectives To understand the differences in line breeding in breeding and cross breeding To understand the election methods used in breeding livestock o In breed same breed clearly relatable i e father daughter These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute Created more homozygous genes Line breeding same breed related down the line Cross breeding completely different breeds Genetic problems o Sheep Spider gene o Cattle Angus bulls curly calf o PSS Pietrain o Horses HYPP Qualitative Traits Those for which phenotypes can be classified into groups rather than numerically measured o i e coat color horns vs polled o Commonly controlled by a single gene Quantitative Traits Those that are usually controlled by many genes having a small effect Most traits that are economically important are quantitatively measured o Additive in nature o Many genes contribute to a measured effect Gene Action Sex linked traits traits genetically controlled by genes located on the sex chromosomes o i e hemophilia color blindness are controlled by a gene on the X chromosome Sex limited traits that are expressed in only one sex o i e milk production egg production and cryptorchidism Selection Determining which animals will reproduce o Natural selection mating of animals in a natural environment o Artificial selection humans dictate breeding of animals castration Inbreeding Mating of relatives More closely related the higher the degree of inbreeding o Creation of more homozygous genes o Animals are more likely to breed true o Only allows genes to be expressed Avoided by most producers dues to commonality of genetic defects and an overall decline in vigor and performance Inbreeding depression loss of reduction of vigor viability or production that usually accompanies in breeding Inbreeding does not increase problems it only allows genes to be more expressed Creation of more pairs of homozygous genes o Therefore animals are more likely to breed true does not increase the number of recessive genes in the population it merely allows them to be expressed Where is inbreeding used Crops Corn o 99 all corn produced o 1 plant female 800 or more Animals chickens o Hen can produce 200 225 chicks year o Seedstock producers Breeding purity BB Bb bb Intensive inbreeding o mating closely related animals for many generations line breeding o mild form where inbreeding is kept low o keep high genetic relationship Phenotype effects of inbreeding increases phenotypic uniformity if accompanied by selection o superior genetic high homozygous and likely to pass on can result in a depression of traits related to physical fitness o i e fertility viability and growth rate animals are less vigorous High inbreeding Usually detrimental to reproduce performance pre weaning and post weaning growth as they are more susceptible to environment stress o 60 70 of inbreeds show detrimental effects while 30 40 show no effect and posses improved productivity Inbreeding in livestock production Crossing of inbred lines heterosis Genetic testing o Quickly identifies some desirable and undesirable genes Especially hidden and serious recessive traits Inbred animals with superior performance generally have superior inbreeding value sand uniform progeny Heterosis compensates for inbreeding depression o Industry with most in breeding Dogs most detrimental Outcrossing Unrelated animals within the same breed are mated o Angus and angus different genes o Hereford breeder good line developed but low in yearling weight will go out and find a bull with high EDP in yearling weight perhaps from another line Crossbreeding Mating to different breeding Hybrid vigor defined as the superiority of the crossbred offspring over the average of the pure breeds parents used to make the cross The two primary reasons to crossbreed o heterosis and complementary of traits mix of different traits preferred system of mating for commercial swine production because more pigs survive from birth to weaning and are heavier at weaning o crossbred sows may wean 40 45 heavier litters than purebreds o 90 are crossbred Two basic types of crossbreeding Rotational o Combines 2 or more breeds o Different breed of boar is mated to a replacement crossbred female produced by the previous generation Terminal o None kept for breeding Dairy Cattle Line breeding Performance of offspring o DHIA keeps records o What mating systems are used in the horse industry Line breeding o Look at performance Intelligence is highly heritable o Ancestors What does the future hold for livestock mating systems Composite animals o Fit environment o Super efficient o Super productive Increased testing o Performance o Genetic