Glossary

This Glossary is derived from the 9th Edition of the BIF Guidelines for Uniform Beef Improvement book, which attributed the original work to John Hough, EPD International and Ronnie Silcox, University of Georgia

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A

Accuracy (of selection)

Correlation between an animal's unknown actual breeding value and an estimated breeding value for a trait, $r_{EPD,BV}$. For, EPDs, BIF recommends using a different calculation that provides more conservative estimates of accuracy. The relationship between the two measures of accuracy is expressed by

$Accuracy_{BIF}=1-{\sqrt {1-r_{EBV,BV}^{2}}}$

and,

$r_{EBV,BV}={\sqrt {1-\left(1-Accuracy_{BIF}\right)^{2}}}$

Across-breed EPDs

Procedures and adjustment factors that allow direct comparison of EPDs from animals of different breeds. They are based upon across-breed EPD adjustment factors which are added to EPDs provided by the separate genetic evaluation of each breed. The adjustment factors, which are updated each year, are based upon estimates of current performance differences among breeds and differences among breeds in genetic base for their evaluations.

Additive adjustment factors

A numerical quantity added to an animal's record to reflect expected performance if the animal had belonged to some baseline group. For example, 60 pounds could be added to weaning weight records of steer calves out of two-year-old dams to represent expected weaning weight if their mother had been five to nine years of age. The use of additive adjustment factors does not affect variability in the trait after adjustment.

Additive genetic effects

For a single locus affecting phenotype, the average effect that one allele has on the phenotype. The additive genetic effect for an animal is its breeding value, equal to the sum of its additive allele effects across all loci that affect the phenotype.

Adjusted weaning weight (WW)

An unshrunk, off-the-cow calf weight adjusted to 205 days of age and to a mature dam age equivalence.

Adjusted yearling weight (YW)

An unshrunk weight adjusted to either 365, 452, or 550 days of age.

Alleles

Alternate forms of genes. Because genes occur in pairs in body cells, one gene of a pair may have one effect and another gene of that same pair (allele) may have a different effect on the same trait.

Alliance

A cooperative business arrangement in which a cattle producer, sometimes in cooperation with other producers, arranges for the retained ownership and/or contract sale of his/her animals before they actually are produced. The agreement typically defines the breeding system, selection methods, management conditions, and product specifications for the cattle.

Animal model

A genetic prediction procedure in which EPDs are directly computed for all animals in the population.

Artificial insemination (AI)

The technique of placing semen from the male into the reproductive tract of the female by means other than natural service.

Autosome

A chromosome that is not a sex chromosome.

Average daily gain (ADG)

Measurement of the average daily body weight change over a specified period of time.

B

Backcross

The mating of a crossbred animal to another individual that is more similar to one of the animal's parental breeds. Example: A Hereford-Angus crossbred cow bred back to an Angus bull.

Base pair

The complementary bases found within a DNA molecule. There are four different bases: adenine (A), thymine (T), cytosine (C), and guanine (G). A always pairs with T, and C always pairs with G. The base sequence ultimately determines the effect of the gene.

Beef carcass data service

[See BCRC ] A program whereby producers, for a fee, can receive carcass evaluation data on their cattle by using a special carcass data ear tag for their slaughter animals. See county extension director, breed representative, Beef Cattle Improvement Association representative, or area office of USDA meat grading service for information.

Beef Improvement Federation (BIF)

A federation of organizations, businesses, and individuals interested or involved in performance evaluation of beef cattle. It seeks to build confidence of the beef industry in the principles and potentials of performance testing. The purposes of BIF are to achieve utilization of the most efficient and effective performance evaluation methods, uniformity of procedures, development of programs, cooperation among interested entities, and education of its members.

Best linear unbiased prediction (BLUP)

A general genetic prediction methodology used to produce EPDs (EBVs). BLUP models can include information from pedigrees, phenotypes, and genotypes.

Biological type

A group of cattle breeds having a similar geographic origin and past selection history and with similar genetic potential for traits of economic importance. British general purpose beef cattle breeds, for example, have genetic potential for moderate growth, muscling, and milk yield; whereas continental European dual-purpose breeds have genetic potential for high milk yield and rapid growth.

Birth weight (BW)

The weight of a calf taken within 24 hours after birth. Heavy birth weights tend to be correlated with calving problems, along with other factors.

Body capacity

A subjective assessment of the feed intake capacity of an individual or breed, typically assessed by visually evaluating body length, body depth, and spring of ribs.

Body condition score

A score on a scale of 1 to 9, reflecting the amount of fat reserves in a cow's body, where 1 = very thin and 9 = extremely fat.

Bos indicus

A subspecies of cattle of south Asian origin. Often known as Zebu, they have prominent humps forward of the shoulder. The Brahman breed is one example in the United States.

Bos taurus

A subspecies of cattle of western Asian origin but often referred to as "European". Most breeds commonly found in the United States and Canada, and their European ancestors, belong to this group. Bos indicus x Bos taurus crosses are viable and fully fertile and exhibit large amounts of heterosis.

Breed

Animals with a common origin and selection history. Animals within a breed have physical characteristics that distinguish them from other breeds or groups of animals within that same species.

Breed association

An organization that maintains pedigree and performance information and arranges for timely genetic evaluation of animals within that breed. Breed associations also establish regulations for registration of animals, promote the breed, and advance the interests of the breeder members.

Breeding objective

The goal of a breeder's selection program, for example, to produce high quality, lean meat at the lowest cost. It may also include a listing of economically related traits to be used as selection criteria to achieve the overall goal. Objectives may vary among breeders due to their genetic and physical resources and their markets.

Breeding soundness examination

Inspection of a bull, including evaluation of physical conformation and soundness through genital palpation, scrotal circumference assessment, and testing of semen for motility and morphological abnormalities.

Breeding value

Transmissible genetic merit of an individual, or the value of that individual as a parent. In the United States and Canada, genetic predictions are expressed as progeny differences rather than as breeding values. Because any parent contributes only half the genes in any one offspring, the progeny difference of an individual is half its breeding value.

British breeds

Breeds of cattle such as Angus, Hereford, and Shorthorn originating in Great Britain.

C

Caesarean section

A process in which the calf is surgically removed from the cow during parturition by making a large incision in the right side of the cow just above the flank.

Calving difficulty (Dystocia)

Abnormal or difficult labor, causing difficulty in delivering the fetus and/or placenta. Difficult births lead to increased calf and cow mortality and to more difficult rebreeding of the cow.

Calving ease

The opposite of calving difficulty. An easy calving is one that does not require assistance and does not impose undue strain on the calf or dam.

Calving ease score

A numerical score quantifying calving ease, ranging from 1 for an easy, unassisted calving through 5 for an abnormal presentation.

Calving season

The season(s) of the year when the calves are born. Limiting calving seasons is the first step to performance testing the whole herd, accurate records, and consolidated management practices.

Carcass evaluation

Techniques for measuring components of quality and quantity in carcasses and using the information for genetic prediction of carcass merit.

Carcass merit

Desirability of a carcass relative to the quantity of components (muscle, fat, and bone), USDA quality grade, and potential eating quality.

Carcass quality grade

An estimate of palatability based primarily on marbling and maturity and generally to a lesser extent on color, texture, and firmness of lean.

Carrier

An individual that is heterozygous, having one dominant and one recessive allele at a given locus. For example, an animal with one gene for polledness and one gene for horns will be polled but can produce horned offspring when mated to another animal carrying the gene for horns.

Categorical traits

Traits that are measured or observed in distinct categories. These traits are usually subjectively scored. Examples include calving difficulty score, condition score, pregnant versus open. To be useful for genetic evaluation when there are more than two categories, there must be a stronger association between adjacent categories than between non-adjacent categories.

centiMorgan (cM)

A measure of genetic distance based on recombination between loci. One Morgan is equal to a 100% chance a crossover occurring between two loci in a single generation. One one-hundredth of that, a centiMorgan, is equal to a 1% chance of of a crossover occurring between two loci in a single generation. The conversion between genetic and physical distance is approximately one cM per one million nucleotides (1 megabase (MB)).

Central test

A comparison conducted at a single location where animals are assembled from several herds to evaluate differences in performance traits under uniform management conditions.

Chromosome

Chromosomes are paired strands of DNA, with accompanying structural proteins, on which genes are located. Domestic cattle have 30 pairs of chromosomes, one chromosome of each pair having been inherited from each parent. One random chromosome of each pair is transmitted to each egg or sperm cell produced by a parent.

Closed herd

A herd in which no outside breeding stock (cattle) are introduced.

Codon

A sequence of three consecutive nucleotides in protein-coding DNA (or RNA) sequence that specify an amino acid in the protein.

Collateral relatives

Relatives of an individual that are not its ancestors or its descendants. Brothers and sisters are an example of collateral relatives.

Commercial producers

Producers whose primary goal is to produce animals for herd replacement, feeding, and slaughter rather than breeding stock for sale to other producers. Progressive commercial producers seek bulls or semen from seedstock breeders that have comprehensive programs designed to produce animals with optimum genetic merit for the combination of traits that increase profitability while managing risk in their production system.

Compensatory gain

Rapid, subsequent gain of cattle that have been nutritionally deprived for some portion of their life.

Composite breed

A breed made up of combinations of other breeds.

Complementarity

The combining of breeds or individual animals that have characteristics that complement each other, thereby obtaining optimum progeny.

Complementary DNA (cDNA)

A DNA copy made from RNA through reverse transcription.

Conformation

A description of the shape of body parts of an animal.

Congenital

A condition that was acquired during prenatal life and therefore exists at or dates from birth. The term is often used in the context of defects present at birth.

Contemporary group

A group of cattle that are of the same sex, are similar in age, and have been raised in the same management group (same location on the same feed and pasture, at the same time). Contemporary groups should include as many cattle as can be accurately compared.

Continental (European) breed

Breeds originally developed on the continent of Europe. Examples include Simmental, Limousin and Charolais.

Correlation

A numerical measure, ranging between 0 and 1 that indicates the degree to which two variables vary together in the same direction (positive correlation) or opposite direction (negative correlation).

Crossbreeding

The mating of animals of different breeds or subspecies, frequently resulting in heterosis (hybrid vigor) for many economically important traits.

Culling

The process of eliminating less productive or less desirable individuals from a herd.

Cutability

An estimate of the percentage of salable meat (muscle) from a carcass versus percentage of waste fat. Percentage retail yield of carcass weight can be estimated by a USDA prediction equation that includes measured or estimated values for hot carcass weight, ribeye area, fat thickness, and estimated percent of kidney, pelvic, and heart fat.

D

he impact of alternative breeding or management strategies on production and profit within a producer's herd.

Decision Support System (DSS)

A set of rules, usually coded into a computer program, that helps a producer evaluate the impact of alternative breeding or management strategies on one or more aspects of a beef production enterprise.

Deviation

The difference between an individual record and the average for that trait in the individual's contemporary group. For all animals within a contemporary group, these differences sum to zero when the correct average is used. A ratio deviation is an individual's ratio minus the group average ratio or 100 when expressed in percentage units.

Direct effect

The effect that an animal's own genetics has on its own phenotype.

For example weaning weight has portion of preweaning growth that is due to the calf's genetics but also has a portion due to the genetics of its dam (see Maternal Effect).

Direct EPD

An EPD representing the one-half of the effect of the individual's own genes on the individuals on phenotype for a trait of interest. A calving ease direct EPD, for example, predicts calving ease of an individual's progeny as opposed to that individual's daughters' progeny (See also Maternal EPD).

Disposition (temperament)

A measure of an animal's docility, wildness, or aggression toward unfamiliar situations, human handlers, or management interventions.

DNA (Deoxyribonucleic acid)

The chemical compound that stores within each cell genetic information unique to an individual. A DNA molecule is composed of two strands of nucleotides bound to one another by chemical bonds between each complementary strand.

Dominant

An allele is dominant when its presence prevents a recessive allele from affecting the phenotype of an individual heterozygous at the locus in question. For example, the allele for polledness (P) is dominant to the allele allowing growth of horns (p), so an animal with the genotype Pp will have the polled form of the trait.

Double muscling

A simply inherited trait evidenced by an enlargement of the muscles with large grooves between the muscle systems especially noticeable in the hind leg.

Dressing percentage

(Chilled carcass weight/live weight) x 100.

Dystocia ( calving difficulty)

Abnormal or difficult labor causing difficulty in delivering the fetus and/or placenta. Difficult births lead to increased calf and cow mortality and to more difficult rebreeding of the cow.

E

Economic value

The net return for a one unit change (pound or percentage, for example) for an economically important trait under selection.

Economically relevant trait

ERT

Any trait that is directly associated with income or costs in a specific production system.

Traits that are of direct economic importance to cattle producers.

Effective progeny number (EPN)

An indication of the amount of information available for estimation of expected progeny differences (EPDs) in cattle evaluation. It is a function of number of progeny of a parent but is adjusted for their distribution among herds and contemporary groups and for the number of contemporaries by other sires. EPN is less than the actual number of progeny because the distribution of progeny is never ideal.

Electrophoresis

A process used to separate DNA fragments by length. DNA fragments are placed at the top of a gel matrix that is then exposed to an electrical current. This causes fragments to migrate through the pores in the gel at rates proportional to fragment size. Resulting fragment location on the gel can be visualized by appropriate labeling techniques.

Embryo Transfer

Removing fertilized ova (embryos) from one cow (the donor), generally in response to hormone-induced superovulation, and placing these embryos into other cows ( the recipients). More calves can be obtained from cows of superior breeding value by this technique.

Environment

All external (non-genetic) conditions that influence the reproduction, production, and carcass merit of cattle. When environmental influences on phenotypic merit are not properly be accounted for in genetic evaluations, they reduce the accuracy of breeding value estimation and of subsequent selection.

Estimated breeding value (EBV)

An estimate of an individual's true breeding value for a trait based on the performance of the individual and close relatives for the trait itself and sometimes performance of genetically correlated traits. EBV combines available performance information on the individual and sibs and the progeny of the individual and other relatives. Expected progeny differences (one-half EBV) have replaced EBVs in most breed association programs.

Exon

Those regions of a gene in which the nucleotide sequence actually codes for a biologically relevant product.

Expected Progeny Difference (EPD)

The difference in expected performance of future progeny of an individual, compared with expected performance at some base point for the population (e.g., the average EPD is 0). The base point may either be fixed or floating. A fixed base sets the average EPD to 0 at a specific point in time (e.g., a specific year). A floating base point changes over years as the number of records analyzed increases. Fixed base points are recommended, especially for traits that have intermediate optima. EPDs are estimated from phenotypic merit of an individual and all of its relatives and are estimates of one-half the animal's estimated breeding value. Genomic marker information is also used to compute EPDs in most cattle evaluations.

F

F1

Offspring resulting from the mating of a purebred (straight-bred) sire of one breed to a purebred dam of a different breed.

Fat thickness

Depth of fat in tenths of inches over the ribeye muscle at the 12th rib. It consists of a single measurement at a point three-fourths of the lateral length of the ribeye muscle from the split chine bone.

Feed conversion and feed efficiency

Feed conversion is the units of feed consumed per unit of weight gained or milk produced. Feed efficiency is the inverse of feed conversion and is thus the unit of weight gained or milk produced per unit of feed consumed.

Fertilization

The union of the male and female gametes to form a new, genetically unique individual. In cattle, sperm and egg cells with 30 chromosomes each combine to form a zygote with the 60 chromosomes normal to the species.

Fingerprint (DNA)

Pattern of DNA fragments unique to an individual. Often produced by using restriction enzymes to cut the DNA into fragments at specific sequences of nucleotides. Using electrophoresis, these fragments can be sorted and then visualized, forming a unique "fingerprint" for each different animal.

Frame score

A score based on subjective evaluation or actual measurement of hip height. This score is related to slaughter weights at which cattle should grade choice or at which different groups of cattle should have comparable amounts of fat.

Freemartin

Female born twin to a bull calf and is sterile (approximately 9 out of 10 will be sterile).

G

Gel (gel matrix)

A porous substance that allows DNA fragments to migrate through it at a rate inversely proportional to fragment size, this allowing separation of DNA fragments.

Generation interval

Average age of parents when the offspring destined to replace them are born. It should be computed separately for male and female parents and then represents the average turnover rate of bulls and cows in the herd. When other factors are held constant, generation interval is inversely related to the rate of response to selection. That is, rapid generation turnover enhances rate of selection response.

Gene

A gene is a discrete segment of the DNA molecule, located at a specific site (its locus) on a specific chromosome pair. Two copies of each gene exist in each nucleated diploid cell in an animal. Only one gene of each pair is randomly transmitted to the offspring through the gamete. The unique nucleotide sequence of each gene determines its specific biological role. Many genes specify the amino acid sequence of a protein product. Others produce gene products that are involved in controlling metabolic and developmental events.

Gene marker

A specific sequence of nucleotides that is easily detectable and can be used to differentiate among alleles at a locus.

General purpose breed

A breed with acceptable genetic merit in reproductive, maternal, growth, and carcass traits, but not specialized in either terminal or maternal characteristics. Such breeds frequently are used in rotational crossbreeding programs.

Genetic antagonism

A genetic correlation in which desirable genetic change in one of the traits is accompanied by an undesirable change in the other. For example, because of the positive genetic correlation between milk yield potential and cow maintenance requirement, selection for increased milk would lead also to increased feed cost for maintenance.

Genetic correlations

Correlations between breeding values for two traits that arise because some of the same genes affect both traits. When two traits (weaning and yearling weight for example) are positively genetically correlated, successful selection for one trait will result in an increase in the other trait as well. When two traits are negatively genetically correlated (birth weight and calving ease, for example), successful selection for one trait will result in a decrease in the other.

Genetic linkage map

A diagram showing where genes and markers are located on a chromosome and their relationship to one another.

Genetic trend

An estimate of the annual change in genetic merit of individuals within a breed for a trait. It is usually computed from the average difference in estimated breeding values of animals born in a series of adjacent years.

Genome

The entire complement of DNA characteristic to individuals of a species.

Genotype

The two alleles present at a locus in an individual. For a locus with only two alleles, three genotypes are possible. For example, at the polled/horned locus in cattle, two common alleles are P ( the dominant allele preventing growth of horns) and p (the recessive allele allowing horn growth). The three possible genotypes are PP (homozygous dominant), Pp (heterozygous or carrier), and pp (homozygous recessive).

Genotype x environment interaction

When the difference in performance among genetic groups depends upon the environment in which they are compared. For example, the most profitable breed in the Great Plains is probably not the same as the most profitable breed on the Gulf Coast. Also, different breeds and crosses will be optimum for producing beef for different market specifications and requirements.

Gestation

The period of pregnancy or the period of time from conception until young are born, averaging about 285 days in cattle.

H

Half-sibs

Individuals having the same sire but different dams (or the same dam but different sires). Half-brothers, half-sisters, or half brother/sister.

Harvest

To slaughter an animal.

Heat (estrous) synchronization

Through hormonal manipulation, causing a group of cows or heifers to initiate estrous cycles at approximately the same time.

Heifer pregnancy EPD

Heifer pregnancy EPDs, expressed as probabilities of successful conception, predict differences among individuals in the ability of their daughters to conceive and calve at two years of age.

Heritability

The proportion of the differences among cattle, measured or observed, that is transmitted, on average, to their offspring. Heritability of different traits may vary from zero to one. The higher the heritability of a trait, the more accurately individual performance predicts breeding value and response to selection for that trait should be more rapid.

Heritability estimate

An estimate of the proportion of the total phenotypic variation between individuals for a certain trait that is due to transmissible genetic merit. It is the proportion of total variation for a trait caused by differences among individuals in breeding value.

Heterosis (hybrid vigor)

Amount by which the average performance for a trait in crossbred calves exceeds the average performance of the two or more purebreds that were mated in that particular cross.

Heterozygote

A genotype in which the two alleles at a locus are different, e.g. Pp.

Homozygote

A genotype in which the two alleles at a locus are the same, e.g. PP or pp.

Hot carcass weight

Weight of a carcass just prior to chilling.

I

Inbreeding

Matings of parents more closely related than average in the population. Inbreeding decreases the proportion of heterozygous gene pairs in the offspring and increases the proportion of homozygous gene pairs. It increases the frequency of expression of genetic defects caused by recessive genes. Inbreeding may increase prepotency for simply inherited and highly heritable traits.

Inbreeding coefficient

A numerical measure, ranging from zero to 1.0, of the intensity of inbreeding of an individual. It represents the proportion of gene loci in the individual at which both genes are identical copies of the same ancestral gene.

Inbreeding depression

The reduction in performance level for many economically important traits that accompanies, on average, an increase in inbreeding coefficient.

Incomplete dominance

A situation in which neither of two alleles at a locus is fully dominant to the other. As a result, both are expressed. Typically the phenotype of the heterozygote is intermediate between that of the two homozygous genotypes.

Indicator trait

Any trait that is not associated with income or costs in a production system but is (genetically) correlated to an economically relevant trait.

Independent culling levels

Selection based on cattle meeting specific levels of performance for every trait included in a selection program. Equivalently, culling based on the failure of cattle to meet the required standard for any trait in the program. For example, a breeder could cull all heifers with weaning weights below 400 pounds (or those in the bottom 20% on weaning weight) and yearling weights below 650 pounds (or those in the bottom 40%).

Integrated resource management (IRM)

Producing beef cattle in a manner that efficiently, profitably, and sustainably uses available human and physical resources.

Interim EPD

An expected progeny difference computed from an individual's own performance information and(or) the EPDs of its parents. Interim EPDs may be used to support selection and merchandizing decisions before EPDs from regularly scheduled national cattle evaluations become available.

International cattle evaluation

An evaluation utilizing data from more than one country, allowing comparisons of estimated genetic merit of cattle across countries.

Intron

DNA whose nucleotide sequence does not code for a product. An intron is transcribed but is excised and not translated. Therefore, it does not affect the sequence of sub-units in the gene product.

K

Kidney, pelvic and heart fat (KPH)

The internal carcass fat associated with the kidney, pelvic cavity, and heart. It is expressed as a percentage of chilled carcass weight. The weight of the kidneys is included in the estimate of kidney fat.

L

Lactation

The period of calf nursing between birth and weaning

Lethal gene

A gene or genes that cause the death of any individual in which they are expressed.

Libido

Sex drive. In bulls, the propensity to detect and mate estrous females.

Linebreeding

A form of inbreeding in which an attempt is made to concentrate the inheritance of some favored ancestor in descendants within a herd. The average relationship of the individuals in the herd to this ancestor is increased by linebreeding, but at the cost of an increased level of inbreeding.

Linecross

Offspring produced by crossing two or more inbred lines.

Linkage

The occurrence of two or more loci on the same chromosome within 50-cM linkage distance of one another.

Linkage disequilibrium

The degree to which to alleles at different loci occur together due to non-random mating in a given population.

Loci

The plural of Locus

Locus

The specific location of a gene or mutation on a chromosome.

M

Maintenance energy requirement

The amount of feed energy required per day by an animal to maintain its body weight and support necessary metabolic functions.

Marbling

The specks of fat (intramuscular fat) distributed in muscular tissue. Marbling is usually evaluated in the rib eye between the 12th and 13th rib. It is a major factor in assigning USDA quality grade of a beef carcass.

Marker Assisted Selection (MAS)

The use of genetic markers to select for specific alleles at linked QTLs and therefore specific traits.

Maternal effect

For weaning weight, the dam's maternal ability which influences preweaning growth.

Maternal EPD

An EPD representing the effect of the genes of an individual's daughters on the trait of interest. A calving ease maternal EPD, for example, represents the ease with which an individual's daughters calves are born. See also Direct EPD.

Maternal heterosis

Amount by which the average performance for a trait in the progeny of crossbred cows exceeds the average performance of progeny of purebred cows of the two or more breed ancestors of the crossbred cows.

Maternal sires

Sires whose major function is to sire daughters (often crossbreds) with outstanding genetic merit for reproductive and maternal traits, adaptability to prevailing environmental conditions, and longevity. Such females would ideally be crossed to sires of a terminal breed with all offspring marketed.

Maturity

An estimation of the physiological age of the animal or carcass. It is assigned by assessing muscle characteristics and the stage of bone maturity.

Metabolic body size

The weight of the animal raised to the 3/4 power (WT^0.75); a value indicative of the feed required to meet metabolic needs and maintain current body weight.

Microsatellite

A type of genetic marker. It is composed of repeating nucleotide sequences within DNA that are locus specific and variable in the number of times the sequence is repeated.

Minisatellite

A type of genetic marker widely used in DNA fingerprinting that consists of repeating subsets of nucleotides that are highly polymorphic and widely distributed throughout the genome.

Morphology

A parameter recorded during microscopic examination of semen in the standardized breeding soundness evaluation quantifying the visual characteristics of spermatozoa, expressed as the percentage that appear normal.

Most Probable Producing Ability (MPPA)

An estimate of a cow's future superiority or inferiority for a repeatable trait (such as progeny weaning weight) based upon the cow's past production in comparison to her contemporaries, her number of past records, and the repeatability of the trait in question.

Motility

A parameter recorded during microscopic examination of semen in the standardized breeding soundness evaluation quantifying spermatozoa movement, expressed as the percentage demonstrating forward progressive movement.

Multiple-breed evaluation

A genetic prediction simultaneously utilizing data from more than one breed or crossbred group. It accounts not only for differences among animals in transmissible genetic value (EPDs) but also in breed differences and heterosis effects.

Multiple-trait evaluation

A genetic prediction which uses phenotypic measurements of two or more genetically correlated traits (birth weight, weaning weight, and post

Multiplicative adjustment factors

A numerical quantity by which an animal's record is multiplied to reflect expected performance if the animal had belonged to some baseline group. The use of multiplicative adjustment factors affects variability in the trait after adjustment, inflating it when the multiplicative factor is greater than 1.0 and deflating it when less than 1.0.

N

National Cattle Evaluation (NCE)

Genetic evaluations conducted by breed associations to compute estimated genetic merit of a population of animals. Carefully conducted national cattle evaluation programs give unbiased estimates of expected progeny differences (EPDs). Cattle evaluations are based on field data and use on information from the individual animal, relatives, and progeny.

Nonadditive gene effects

Effects of specific gene pairs or combinations of gene pairs. Nonadditive gene effects occur when the heterozygous genotype is not intermediate in phenotypic value to the two homozygous genotypes. Undesirable homozygous gene combinations lead to inbreeding depression in inbred populations; whereas favorable heterozygous gene combinations lead to heterosis in outbred herds.

Nucleotide

The subunit of DNA composed of a five carbon sugar, one of four nitrogenous bases (adenine, thymine, cytosine, or guanine), and a phosphate group.

Number of contemporaries

The number of animals of similar breed, sex, and age against which an animal was compared in performance tests. The greater the number of contemporaries, the greater the accuracy of comparisons.

O

Optimum level of performance

The most profitable or favorable ranges in levels of performance for the economically important traits in a given management system and environment. For example, although many cows produce too little milk, in every management system there is a point beyond which higher levels of milk production will reduce fertility and decrease profit.

Outbreeding (outcrossing)

Mating together of animals that are not closely related. Mild outbreeding is illustrated by mating cows to a sire of their own breed but who is not closely related to them. Such outcrossing may widen the genetic base in a herd and reduce inbreeding accumulation. A higher level of outcrossing is illustrated by crossing two Bos taurus breeds. This generally would result in beneficial heterosis for economically important traits. Crossing of a Bos taurus to a Bos indicus breed is outcrossing of an even greater extreme. These two subspecies have been genetically isolated from one another for a very long time, so heterosis is expected to be greater than from a within subspecies cross. The widest possible outcross is between genetically distinct species, cattle and bison for example. Progeny from such crosses, even when viable, frequently are subfertile or infertile.

Ovulation

Release of the female germ cell (egg or ovum) by the ovary. Cows usually ovulate several hours (up to 15 hours) after the end of estrus or standing heat.

P

Palatability

Acceptable to the taste or sufficiently agreeable in flavor to be eaten.

Parturition

The act of giving birth; calving.

Pedigree

A tabulation of names of an individual's ancestors, often only those of the three to five closest generations. Pedigree information is used to establish genetic relationships among individuals to use in genetic evaluations.

Percent calf crop

The percentage cows and heifers exposed to breeding within a herd and year that produce calves.

Performance data

The record of the individual animal for reproduction, production, or carcass merit. The most useful performance records for management, selection, and promotion decisions may not be the same for all seedstock breeders and may be different for seedstock breeders and commercial cattle producers.

Performance pedigree

A pedigree that includes performance records of the individual, ancestors, relatives, and progeny in addition to the usual pedigree information. Expected progeny differences may also be included.

Performance testing

The systematic collection of comparative production information for use in genetic evaluation, selection decisions, and merchandizing.

Phenotype

The visible or measurable expression of a character; weaning weight, postweaning gain, or reproduction for example. For most traits, phenotype is influenced by both genotype and environment. The relative degree to which phenotypic variation among individuals is caused by transmissible genetic effects is the heritability of a trait.

Phenotypic correlation

The net correlation between two traits caused both by genetic factors and environmental factors simultaneously influencing both traits.

Plasmid

A circular piece of bacterial DNA often used as a cloning vector to produce recombinant DNA in large quantities.

Polled

Naturally hornless cattle. Having no horns or scurs.

Polymerase Chain Reaction (PCR)

A process used to rapidly amplify DNA. The original DNA is heated, causing the strands to separate. Specific primers are then added and bond to the single strands. DNA polymerase adds nucleotides to the primer, extending the new DNA strand. The PCR process can be repeated to produce many copies.

Polymerase

The enzyme system that facilitates the replication of DNA or RNA.

Polymorphism

The existence of two or more alleles at a gene locus in a population.

Possible change

The amount by which an individual's current EPD might reasonably be expected to change (either upwards or downwards) as more information becomes available in subsequent national cattle evaluations. This measurement of error in prediction decreases as the number of offspring per sire increases.

Postpartum

After the birth of an individual.

Postpartum interval

The number of days between parturition and the first postpartum estrus.

Prepotency

The ability of a parent to transmit its characteristics to its offspring so that they resemble that parent, and one another, more than usual. An individual that is homozygous for a dominant allele will show prepotency for the trait controlled by that gene, but not necessarily for any other trait. Inbred cattle, having a higher than average degree of homozygosity, may be more prepotent than outbred cattle but only for simply inherited or highly heritable traits.

Preweaning gain

Weight gained between birth and weaning.

Progeny

The young, or offspring, of the parents.

Progeny testing

Evaluating the genotype or estimating the breeding value of an individual by evaluating the comparative phenotypic merit of its progeny.

Puberty

The age at which the reproductive organs become functionally operative and secondary sex characteristics begin to develop.

Purebred

An animal of known ancestry within a recognized breed that is eligible for registry in the official herd book of that breed.

Q

Qualitative (categorical) traits

Those traits in which there is a sharp distinction between phenotypes, such as black vs. red or polled vs. horned. Only one or a few pairs of genes are involved in the expression of many qualitative traits.

Quantitative traits

Those traits, such as weaning weight, in which there is no sharp distinction in the range of phenotypes, with a gradual variation from one extreme to the other. Usually, many gene pairs are involved as well as environmental influences affect variation for such traits.

Quantitative Trait Loci (QTL)

A gene locus that has an effect on a quantitative trait. Often the actual nucleotide sequence is unknown, so selection is based upon genotype at a linked gene marker.

R

RAPDs

Randomly Amplified Polymorphic DNAs. Genetic markers that are randomly amplified using PCR with random primers to find polymorphic regions.

Random mating

A system of mating in which every female (cow and/or heifer) has an equal or random chance of being assigned to any bull used for breeding in a particular breeding season.

Rate of genetic improvement

The amount of improvement per unit of time (year). The rate of improvement is dependent on: (1) accuracies in ranking animals for their breeding values of traits considered, (2) selection intensity (a function of the proportion selected, e.g., 1 out of 100 is more intense than 1 out of 10), (3) genetic correlations among traits considered, (4) generation interval in the herd, and (5) the number of traits for which selections are made.

Ratio

An expression of an animal's performance for a particular trait relative to the herd or contemporary group average. It is calculated for most traits as:

${\frac {\textrm {Individual\quad Record}}{\textrm {Group\quad Average}}}\times 100$

Recessive

Recessive alleles are expressed only when homozygous. They must have been inherited from both parents before the phenotype can be expressed. At the locus for growth or absence of horns, for example, homozygous recessive pp genotype individuals are horned whereas PP and Pp genotype individuals are polled.

Reduced animal model

A genetic prediction procedure in which EPDs are computed directly for all parents in the population, while EPDs for non-parents and progeny are computed from the parent solutions. Predictions are equal and equivalent to those from the animal model. See animal model and sire model.

Reference sire

A bull that has previously been progeny tested and subjected to national cattle evaluation that is used concurrently with a test sire or sires in a new progeny test program. Reference sires provide genetic linkages among herds and/or existing databases, allowing indirect comparison of the test sire with bulls evaluated at other places and times.

Regression

A measure of the relationship between two variables expressing the expected change in one of them per unit change in the other. Using regression methods, the value of one trait can be predicted by knowing the value of others. For example, easily obtained carcass traits (hot carcass weight, fat thickness, rib eye area, and percentage of internal fat) are used to predict percent cutability.

Relationship matrix

A table that stores numerical values for the genetic relationships among pairs of animals. It is used to predict genetic merit of each animal from its own phenotypic merit and that of all of its relatives. Examples of simple genetic relationships are: parent and offspring is 0.50, full-sibs is 0.50, and half-sibs is 0.25.

Relative economic value

The amount by which net income to the cattle enterprise will change, per unit change in genetic merit for a trait.

Residual Feed Intake (RFI)

The difference between actual and predicted feed intake (e.g., actual feed intake minus predicted feed intake; predicted feed intake is estimated by multiple regression of feed intake on average daily gain and mid–weight during a test period as independent variables).

Restriction enzyme (Endonuclease)

One of over 150 enzymes derived from bacteria that recognizes specific DNA sequences and cuts the DNA at those sites.

Restriction site

The specific recognition site in DNA at which a specific restriction enzyme cuts the DNA.

RFLP (Restriction Fragment Length Polymorphism)

Polymorphism identified by digesting DNA with a restriction enzyme. Individuals differ in their resulting fragment patterns, which are visualized radioactively after separation through gel electrophoresis.

Ribonucleic acid (RNA)

A single-stranded molecule composed of ribonucleotides. RNA differs from DNA in that it contains the base uracil (U) instead of thymine (T). RNA is formed from DNA through transcription. It is involved in transferring and translating the genetic message from a gene into a protein product with a specific physiological function

Ribeye area

Area in square inches of the longissimus muscle measured at the 12th rib interface on the beef forequarter.

Rotational crossbreeding

Systems of crossing two or more breeds where the crossbred females are bred to bulls of the breed contributing the lowest proportion of genes to those females. Rotational crossbreeding systems maintain relatively high levels of heterosis and allow for replacement heifers to be produced from within the system.

S

Scrotal circumference

A measure of testes size obtained by measuring the distance around the pair of testicles in the scrotum with a circular tape. Related to semen producing capacity and age at puberty of female sibs and progeny.

Scurs

Horny tissue or rudimentary horns that are attached to the skin rather than the bony parts of the head.

Seedstock breeders

Producers whose primary goal is to produce breeding stock rather than animals for feeding and slaughter. Progressive seedstock breeders have comprehensive programs designed to produce animals with optimum genetic merit for the combination of traits to increase downstream profit of commercial beef production.

Selection

Choosing some individuals and rejecting others as parents of the next generation of offspring.

Selection differential

The difference between the average for a trait for selected cattle and the average of the group that was available for selection. The expected response to selection for a trait depends on selection intensity and accuracy of EPDs.

Selection index

A formula that combines performance records from several traits or different measurements of the same trait into a single value for each animal. Selection indexes assign relative emphasis to different traits according to their relative net economic importance, their heritability, and genetic associations among the traits.

Selection intensity

The selection differential measured in phenotypic standard deviation units of the selected trait. It is inversely proportional to the proportion of available replacements actually selected to be parents of the next generation. For example, with A. I. compared to natural service, only a small proportion of bulls needs to be selected, and the selection intensity, selection differential, and selection response will be high.

Serving capacity

A measure of the motivation, willingness, and ability of a bull to detect and service females in estrus.

Sibs

Brothers and sisters of an individual; full-sibs have the same sire and dam, paternal half-sibs have the same sire but different dams, and maternal half-sibs have the same dam but different sires.

Single nucleotide polymorphism (SNP)

A variation of base-pairs at a specific nucleotide location in DNA for a defined population.

Sire x environment interaction

When the difference in progeny performance among sires is dependent upon some factor of the environment under which the progeny were compared. For example, sires might rank differently for progeny performance in different contemporary groups, herds, or regions.

Sire model

A genetic prediction procedure in which EPDs are directly computed for all sires with progeny in the population.

Sire summary

Published genetic predictions (EPDs) of sires for economically important traits from national cattle evaluation programs.

Sperm

A mature male germ cell.

Standardized performance analysis (SPA)

A set of programs that allow producers to collect, process, and interpret information on biological efficiency and economic returns to a seedstock or commercial beef production enterprise.

Stayability EPD

The expected difference among individuals in the probability that a daughter will stay in the herd to at least six years of age. Because the majority of cows culled before the age of six are open, the EPD is primarily a prediction of sustained fertility in female offspring.

Super ovulation

Process by which a cow is treated with reproductive hormones to induce her to produce more eggs than normal.

Systems approach

An approach to evaluate breeding programs and selection schemes that involves assessment of alternatives in terms of their net impact on all inputs and output in the production system. This approach specifically recognizes that intermediate levels of performance in several traits may be more profitable than maximum performance for any single trait.

T

Tandem selection

Selection for one trait at a time. When the desired level is reached in one trait, then selection is practiced for a second trait.

Temperament (disposition)

A measure of the relative docility, wildness, or aggression of an animal toward unfamiliar situations, human handlers, or management interventions.

Terminal sires

Sires used in a crossbreeding system in which all progeny, both male and female, are marketed. For example F1 crossbred dams could be bred to terminal sires of a third breed and all calves marketed. Although this system allows maximum heterosis and complementary of breeds, replacement females must come from other herds.

Threshold model

Statistical procedures for analyzing traits that are expressed in an all-or-none fashion (alive vs dead or pregnant vs open, for example) or categorical (e.g., calving ease) but that are affected by environmental factors and by genes at many loci. When genetic predictions are conducted for such traits using the threshold model, resultant EPDs reflect the expected proportion of an individual's progeny that will or will not express the trait or fall within a given category.

Trait

Something measured or observed on an individual that is inherited.

Transcription

The process by which an RNA copy is made from a gene.

Translation

The process by which ribosomes use the nucleotide sequence in RNA to synthesize proteins.

U

Ultrasonic measurements

A noninvasive method used to estimate carcass characteristics and reproductive events. It operates off the principle that sound waves echo differently with different densities of tissue.

V

Variance

Variance is a statistic that numerically describes the differences (variation) among individuals for a trait in a population. Variance is the average squared deviation (difference) from the average. Without variation, no genetic progress would be possible, because genetically superior animals would not be distinguishable from genetically inferior ones.

VNTR (Variable Number of Tandem Repeats)

A type of minisatellite that is locus specific but cannot be generated by PCR.

W

Weight per day of age (WDA)

Weight of an individual divided by its age in days.

Whole Herd Reporting (WHR)

An inventory based performance recording system in which the production of all animals in a breeding herd and the performance of all progeny are accounted for annually. In calf-based systems, by contrast, progeny performance data may be recorded selectively but production information will not gathered on females that do not produce live calves. An inventory based Whole Herd Reporting system is necessary to acquire data for genetic evaluation of some reproductive traits.

Y

Yield grade (see cutability)

A numerical score ranging from 1 (high yield) to 5 (low yield) reflecting the expected proportion of boneless, closely-trimmed cuts from the beef carcass. It is estimated from a USDA prediction equation that includes measured or estimated values for hot carcass weight, rib eye area, fat thickness, and estimated percentage of kidney, pelvic, and heart fat.