Abortion B The delivery of fetuses or fetal membrances between date of servie and up to and inclusing the 109th day of pregnancy.

Accuracy (of selection) B Correlation between an animal's unknown actual breeding value and a calculated estimated breeding value.

Adjusted 21-day litter weight (W) B Total weight of all pigs from one litter adjusted to 21 days of age, to a 2nd parity sow and 10 pigs/litter after transfer.

Ad lib feeding B No limit placed on amount of feed intake. Self-feeding or allowing pigs to consume feed on a free-choice basis.

Alleles B 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.

Anestrous female B A female that is expected to express, but has not been detected in, estrous.

Artificial insemination B The technique of placing semen in the reproductive tract of the female by means other than natural service.

Average daily gain (ADG) B Amount of weight gained per day per pig during a defined period of time.

Backcross B The mating of a two-breed crossbred offspring back to one of its parental breeds. Example: A Yorkshire-Landrace cross sow bred back to a Yorkshire boar.

Best linear unbiased prediction (BLUP) B A method of calculating estimated breeding values or expected progeny differences that accounts for all known sources of information about the traits being evaluated.

Birth litter B The pigs produced by one mated female at one farrowing.

Birth weight B The weight of a pig taken within 24 hours after birth.

Boar B A replacement boar is any intact (uncastrated) male pig intended for use in the breeding herd, but which has not yet been used for breeding. A service boar is any boar that is being, or has been, used for breeding purposes.

Breeder B An indidvidual or company who is the owner of the sow at the time she was mated or bred to produce a litter of pigs.

Breeding female B An unmated or mated female kept for breeding purposes.

Breeding female day B One breeding female for one day.

Breeding herd B The total inventory of breeding females and boars in a herd.

Breeding program goals B The objective or "direction" of breeders' selection programs. Goals may vary among breeders due to relative genetic merit of their pigs, their resources, and their markets.

Breeding value B Value of an animal as a parent. The working definition is twice the difference between a very large number of progeny and the population average when individuals are mated at random within the population and all progeny are managed alike. The difference is doubled because only a sample half (one gene of each pair) is transmitted from a parent to each progeny. Breeding value exists for each trait and is dependent on the population in which the animal is evaluated. For a given trait, an individual pig can be above average in a population defined one way, and below average in a population defined another way.

Carcass merit B Desirability of a carcass relative to quantity of muscle, fat, bone, and quality of lean tissue. Many packers estimate carcass merit by measuring backfat and one or more other indicator traits such as carcass weight.

Carrier B A heterozygous individual having one recessive gene and one dominant for a given pair of genes (alleles).

Central test B A location where animals are assembled from several herds to evaluate differences in certain performance traits under uniform management conditions.

Chromosome B Chromosomes are long DNA molecules on which genes (the basic genetic codes) are located. Swine have 19 pairs of chromosomes.

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

Conceive B To become pregnant.

Conception B The act of conceiving or becoming pregnant and the fertilization of the ovum takes place.

Congenital B Acquired during prenatal life. Condition exists at or dates from birth. Often used in the context of congenital (birth) defects.

Contemporary group B A group of pigs that are of the same genetic background and gender and have been raised in the same management group (in the same location and on the same feed). Contemporary groups should include as many pigs as can be accurately compared.

Correlation B A measure of how two traits vary together. A correlation of +1.00 means that as one trait increases the other also increases -- a perfect positive relationship. A correlation of -1.00 means that as one trait increases the other decreases -- a perfect negative, or inverse, relationship. A correlation of 0.00 means that as one trait increases, the other may increase or decrease -- no consistent relationship. Correlation coefficients may vary between +1.00 and -1.00.

Crossbreeding B The mating of animals of different genetic backgrounds within a species. Crossbreeding usually results in heterosis (hybrid vigor).

Cross fostering B The transfer of baby pigs among litters.

Culling B The process of eliminating less productive or less desirable animals from a herd.

Dam B The female parent.

Deviation B A difference between an individual record and the average for that trait for that contemporary group. These differences sum to zero when the correct average is used.

Dominance B Dominant genes affect the phenotype when present in either homozygous or heterozygous condition. A dominant gene need only be obtained from one parent to achieve expression.

Economic value B The net return within a herd for making a unit change in the trait in question.

Environment B All external (nongenetic) conditions that influence the reproduction, production, and carcass merit of pigs.

Estimate B The process of calculating a particular value from data (verb). The value itself obtained from data (noun). The idea is that the true value is being obtained from the calculated value within limits of sampling variation.

Estimated breeding value (EBV) B An estimate of an individual's true breeding worth for a trait based on the performance of the individual and close relatives for the trait. EBV is a systematic way of combining available performance information on the individual, brothers and sisters of the individual, and the progeny of the individual. EBV's are usually expressed in actual units (pounds, cm, percent). See definition of "breeding value."

Estrous B A period of sexual receptivity to the male which may not imply service or mating.

Expected progeny difference (EPD) B The difference in performance to be expected from future progeny of a sire, compared with that expected from future progeny of the average boar in the same population. EPD is equal to one-half the estimate of breeding value obtainable from records. EPD's are generally expressed either as a plus difference or minus difference from the population average, reported in the units of measure of the trait (e.g., pounds, inches, square inches, percent, etc.).

Exposure B The act of entering a boar into a group of breeding females.

Farrowing B Production of a litter of one or more live, stillborn or mummified pigs on or after the 110th day of prognancy (day of service is considered as day 0).

Farrowing date B The date on which the first pig of the litter was born.

Farrowing frequency B A calendarized system for initiating group farrowing expressed in day or weeks.

Farrowing index B Litters per mated female per year.

Farrowing interval (days) B The number of days between two consecutive farrowings for an individual female.

F1 offspring B Offspring resulting from the mating of a purebred (straightbred) boar to purebred (straightbred) females of another breed.

Feed conversion (feed efficiency) B Units of feed consumed per unit of weight gained. Also, the production (meat, milk) per unit of feed consumed.

Generation interval B Average age of the parents when the offspring destined to replace them are born. A generation represents the average turnover rate of a herd.

Genes B The basic units of heredity that occur in pairs and have their effect in pairs in the individual, but which are transmitted singly (one or the other gene at random of each pair) from each parent to offspring.

Genetic correlations B Correlations between two traits that arise because some of the same genes affect both traits. When two traits (i.e., number pigs born alive and 21-day litter weight) are positively and highly correlated to one another, successful selection for one trait will result in an increase in the other trait. When two traits are negatively and highly correlated to one another, successful selection for one trait will result in a decrease in the other trait.

Genetic marker B a DNA fragment that has been mapped to a specific site on a chromosome and which can be used to help identify traits of interest.

Genotype B Actual genetic makeup (constitution) of an individual, determined by its genes or germplasm.

Genotype-environment interaction B Variation in the relative performance of different genotypes from one environment to another. For example, the "best" hogs (genotypes) for one environment may not be the "best" for another environment.

Gestation B Period of time between conception and farrowing.

Gestation length B Period of pregnancy, or the time between the conception service and the subsequent farrowing or abortion (the day of service is counted as day 0).

Gilt B A female of swine specie less than one year of age that has not produced a litter of pigs.

Half-sibs B Individuals having the same sire or dam. Half-brothers and/or half-sisters.

Heat period B The period of a female's receptivity to a boar. Syn: Estrous, estrous period.

Heredity B The transmission of genetic or physical traits of parents to their offspring.

Heritability B The proportion of the differences among individuals, measured or observed, that is transmitted to the offspring. Heritability varies from zero to one. The higher the heritability of a trait, the more accurately the individual performance predicts breeding value and the more rapid should be the response due to selection for that trait.

Heritability estimate B An estimate of the proportion of the total phenotypic variation between individuals for a certain trait that is due to heredity. More specifically, hereditary variation due to additive gene action.

Heterosis (hybrid vigor) B Amount by which traits measured on the crossbred offspring exceed the average of traits measured on the parents.

Heterozygous B Alleles of a specific gene pair are different in an individual.

Homozygous B Alleles of a specific gene pair are alike in an individual.

Hybrid B Progeny of genetically diverse parents (purebred or crossbred).

Inbreeding B Production of offspring from parents more closely related than the average of a population. Inbreeding increases the proportion of homozygous gene pairs and decreases the proportion of heterozygous gene pairs. Also, inbreeding increases prepotency and facilitates expression of undesirable recessive genes.

Independent culling levels B Selection based on animals meeting specific levels of performance for each trait included in the breeder's selection program. For example, a breeder could cull all boars with scrotal hernias and all boars with more than one inch of backfat.

Insemination B Placing semen in the reproductive tract of the female either by natural or artificial means.

Lactation B The production of milk by a breeding female commencing at farrowing and terminating at abrupt weaning.

Lactation length (days) B The number of days a breeding female spends from farrowing to weaning (farrowing = day 0).

Linebreeding B A form of inbreeding in which an attempt is made to concentrate the inheritance of some one ancestor, or line of ancestors, in a herd. The average relationship of the individuals in the herd to this ancestor (outstanding individual or individuals) is increased by linebreeding.

Linecross B Offspring produced by crossing two or more inbred lines within a breed.

Litter B Pigs born to a sow during one farrowing.

Litter birth weight (lbs.) B Total birth weight of all live born pigs farrowed in a litter within 24 hours of farrowing, and prior to cross-fostering.

Litter weaning weight (lbs.) B The sum of the weight of all pigs weaned and/or nursed off a breeding female during one lactation.

Live born pigs B Total pigs farrowed minus stillborn and mummified pigs.

Loin muscle area B The cross sectional area of the loin muscle measured between the 10th and 11th ribs.

Marbling B The specks of fat (intramuscular fat) distributed in muscular tissue. Marbling is usually evaluated in the loin muscle between the 10th and 11th rib.

Marker assisted selection B Using genetic markers to improve the accuracy of selection for traits of economic importance.

Mated female B Any breeding female which has been mated at least once and has not yet been removed from the herd.

Mated female day B One mated female for one day.

Mated female inventory B A count of mated females at a point of time.

Mating B The act of insemination where one or more matings in the same heat period comprises a service.

Mixed pigs B Male and female pigs commingled.

Mummified pigs B The pigs that are born degenerate (discolored and shriveled or decomposed) that died sometime during gestation.

Nonadditive gene effects B Favorable effects or actions produced by specific gene pairs or combinations. Nonadditive gene action is the primary cause of heterosis. Nonadditive gene action occurs when the heterozygous genotype is not intermediate in phenotypic value to the two homozygous genotypes.

Number born alive B Total pigs born, minus the stillborn and mummified pigs.

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

Outcrossing B Mating of individuals that are less closely related than the average of the breed. Commercial breeders and some purebred breeders should be outcrossing by periodically adding new sires that are unrelated to their herd. This outcrossing should reduce the possibility of loss of vigor due to inbreeding.

Parity B The number of times a sow has farrowed, i.e., a 4th parity sow has farrowed four times.

Pedigree B A tabulation of names of ancestors, usually only those of three closest generations.

Performance data B The record of the individual animal for reproduction, production, and carcass merit. Traits may include number of pigs born alive, 21-day litter weight, days to 240 pounds, backfat, etc.

Performance pedigree B A pedigree that includes performance records of ancestors, half and full sibs, and progeny in addition to the usual pedigree information.

Performance testing B The systematic collection of comparative production information for use in decision making to improve efficiency and profitability of swine production.

Phenotype B The visible or measurable expression of a character; for example, 21-day litter weight, postweaning gain, reproduction, etc. Phenotype is influenced by genotype and environment.

Phenotypic correlations B Correlations between two traits caused by both genetic and environmental factors influencing both traits.

Pounds of lean pork per day of age B A measure of cutability and growth combined, it is calculated from predicted carcass lean divided by age in days.

Prepotent B The ability of a parent to transmit its characteristics to its offspring so they resemble that parent, or each other, more than usual. Homozygous dominant individuals are prepotent. Inbred swine tend to be more prepotent than outbred swine.

Profitability B A criterion for measuring the relationship between income and expenses for different investments, operations, or firms.

Progeny records B The average, comparative performance of the progeny of sires and dams.

Progeny testing B Evaluating the genotype of an individual by a study of its progeny records.

Purebred B An animal of known ancestry within a recognized breed that is eligible for registry in the official herdbook of that breed.

Qualitative traits B Those traits in which there is a sharp distinction between phenotypes, such as hair coat color. Only one or few pairs of genes are involved in the expression of qualitative traits.

Quantitative traits B Those traits in which there is no sharp distinction between phenotypes, with a gradual variation from one phenotype to another, such as backfat. Usually, many gene pairs are involved, as well as environmental influences.

Random mating B A system of mating where every female has an equal or random chance of being assigned to any male used for breeding in a particular breeding season. Random mating is required for accurate progeny tests.

Rate of genetic improvement B Rate of improvement per unit of time (year). The rate of improvement is dependent on: 1) heritability of traits considered; 2) selection differentials; 3) genetic correlations among traits considered; 4) generation interval in the herd; and 5) the number of traits for which selections are made.

Reach B See "Selection differential."

Recessive gene B Recessive genes affect the phenotype only when present in a homozygous condition. Recessive genes must be received from both parents before the phenotype caused by the recessive genes can be observed.

Reference sire B A boar designated to be used as a benchmark in progeny testing other boars (young sires). Progeny by reference sires in several herds enable comparisons to be made between boars not producing progeny in the same herd(s).

Regression (regressed) B A measure of the relationship between two variables. The value of one trait can be predicted by knowing the value of the other variable. For example, easily obtained carcass traits (hot carcass weight, fat thickness, and loin muscle area) are used to predict percent lean. Likewise, breeding value estimates based on limited data are regressed back toward the population average to account for the imperfection of this relationship.

Rotational crossbreeding B Systems of crossing two or more breeds in which the crossbred females are bred to boars of the breed contributing the least genetic material to that female's genotype. Rotation systems maintain relatively high levels of heterosis and typically produce replacement females from within the system.

Seedstock breeders B Producers of breeding stock for purebred and commercial breeders. Progressive seedstock breeders have comprehensive programs designed to produce an optimum or desirable combination of economical traits (genetic package) that will ultimately increase the profitability of commercial swine production.

Selection B Causing or allowing certain individuals in a population to produce offspring in the next generation.

Selection differential (reach) B The difference between the average for a trait in selected animals and the average of the group from which they came. The expected response from selection for a trait is equal to selection differential times the heritability of the trait.

Selection index B 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 weight the traits for their relative net economic importance and their heritabilities plus the genetic association among the traits.

Sibs B Brothers and sisters of an individual.

Sow B Any breeding female that has farrowed at least one litter or has reached 12 months of age.

Stillborn pigs B Fully developed pigs found dead behind the sow, or in the afterbirth, after farrowing. Lungs of stillborn pigs do not float in water.

Stress B Any force causing or tending to cause a change in a pig's function, structure, or behavior.

Systems approach B An approach to evaluating alternative individuals, breeding programs, and selection schemes that involves assessment of these alternatives in terms of their net impact on all inputs and output in the production system. This approach specifically recognizes that intermediate optimum levels of performance in several traits may be more economically advantageous than maximum performance for any single trait.

Tenth rib backfat B Backfat taken over the loin muscle at the 10th rib. Divide the longest axis of the loin muscle into quarters. Measure the fat depth opposite a point three-fourths the distance along the long axis toward the belly. The measurement is from the edge of the muscle to the outer edge of, and perpendicular to, the skin.

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

Ultrasonics B Technique for estimating certain aspects of body composition and for pregnancy detection.

Variance B Variance is a statistic that describes the variation seen in a trait. Without variation, no genetic progress is possible, since genetically superior animals would not be distinguishable from genetically inferior ones.

Weaning B The act of separarting the pigs and the female.

Weight per day of age (WDA) B Weight of an individual divided by days of age.

More terms and exact definitions of equations may be found in NPPC=s publications.