Animal & Veterinary


The following terms are defined as they are used within the current risk assessment. Unless otherwise indicated, definitions provided are the commonly accepted use of the term(s) at the Center for Veterinary Medicine, and may have been derived from various 115 sources.

allele Any alternative form of a gene that can occupy a particular chromosomal locus.
anal atresia Abnormally closed anal opening.
analyte A substance undergoing analysis.
aneuploid Describes a cell or organism which has an abnormal total number of chromosomes and where numbers of individual chromosomes are out of proportion with the numbers of the other chromosomes. Too many chromosomes is called hyperploidy; too few is called hypoploidy.
animal clones Animals derived via somatic cell nuclear transfer techniques. The terminology employed in this assessment did not use “cloned animals.” The phrase “cloned animals” does not clearly differentiate between the animal serving as the source of genome being propagated, or the animal that has been generated from a particular source. For example, the sentence “That field contains several cloned animals” does not specify whether the animals had been used as a source of material for SCNT or whether they had been generated by that technology.
ARTs Assisted reproductive technologies.
biallelic Referring to expression of two alleles at the same time.
bioengineered animals The broadest category of animals associated with molecular biology techniques, including animal clones and all genetically engineered animals.
blastocyst An early stage in the development of mammalian embryos, when the embryo is a spherical body comprising an inner cell mass that will become the fetus and an outer ring of cells, the trophectoderm, that will become part of the placenta.
blastomere Any one of the cells formed from the first few cell divisions in animal embryology. The embryo usually divides into two, then four, then eight blastomeres, and so on.
Blastomere Nuclear Transfer ( BNT) An assisted reproductive technique in which a blastomere is used as a donor for nuclear transfer into enucleated oöplasts.
capacitation The process of sperm maturation (or activation) that occurs post-ejaculation. Allows the spermatozoa to go through the acrosomal reaction in which factors in the sperm head that allow it to penetrate the egg are released and fertilize an oöcyte.
caruncle The site of attachment in the maternal uterus of the ruminant for the placental cotyledon (see cotyledon).
centromere (centromeric) A specialized chromosome region to which spindle fibers attach during cell division (mitosis) that is genetically inactive. This is constricted region of a mitotic chromosome that holds sister chromatids together—the crossing point in the “X” often used to depict chromosomes.
chimera An organism or recombinant DNA molecule created by joining DNA fragments from two or more different organisms.
chondrocyte A mature cartilage cell.
chorion The outermost membrane enclosing the fetus. It is formed from tissues on the outside of the embryo such as the trophoblast, and the part of it attached to the uterus wall eventually develops into the placenta.
chromatid One of the two daughter strands of a duplicated chromosome.
chromatin The network of fibers of DNA and protein that make up the chromosomes of the eukaryotic nucleus during interphase.
chromosome(s) A structure composed of one very long molecule of DNA and associated proteins (e.g. histones) that carries hereditary information.
cleavage The series of mitotic divisions by which a fertilized animal ovum changes, without any overall change in size, into a ball of smaller cells constituting the primitive embryo.
clone A group of cells or individuals that are genetically identical as a result of asexual reproduction including nuclear transfer.
cloning Asexual reproduction of animals using somatic cell nuclear transfer (SCNT).
coherence The extent to which a hypothesized causal association is compatible with preexisting theory and knowledge.
colostrum The first fluid secreted by the mammary glands at the time of birthing that is rich in antibodies and nutrients, and precedes the production of true milk. Its ingestion confers passive maternal immunity on the offspring of some species.
Comprehensive Veterinary Exam (CVE) Systematic approach for examining domestic livestock animals and making informed judgments as to their health. The CVE contains both objective and subjective information and is performed by a veterinarian.
congenital Existing at, and usually before, birth; referring to conditions that are present at birth, regardless of their causation.
consistency  Close conformity between findings in different studies conducted by different methods or different investigators.
cortisol The major natural glucocorticoid hormone synthesized in the zona fasciculata of the adrenal cortex; it affects the metabolism of glucose, protein, and fats. It also regulates the immune system and affects many other functions.
cotyledon A lobule structure in ruminant placentae that form contact points between the fetal-derived placental tissues with the maternal caruncles (attachment points) of the uterus to form the functional units called placentomes. It consists mainly of a rounded mass of villi.
cryptorchid A male animal with one or both testicles retained within the body cavity.
cull To remove unwanted members or parts from a herd.
cytoplasm The living contents of the cell, exclusive of the nucleus, consisting of an aqueous protein matrix or gel, and where essential membranes and cellular organelles (mitochondria, plastids, etc.) reside.
de novo Literally means “anew.” Beginning a process from its origin with out prior plans.
dermatitis vegetans A hereditary disease of the skin in swine (see hyperkeratosis).
differentiation The process whereby relatively unspecialized cells, e.g. embryonic or regenerative cells, acquire specialized structural and/or functional features that characterize the cells, tissues, or organs of the mature organism or some other relatively stable phase of the organism’s life history.
diploid Having two sets of chromosomes.
DNA Abbreviation for deoxyribonucleic acid; one of the two types of nucleic acids that constitutes the genetic material of most known organisms; usually in double helix form .
DNA polymerase The enzyme responsible for copying DNA. Common name for either of two categories of enzymes that catalyze the synthesis of DNA from deoxyribonucleoside triphosphates in the presence of a nucleic-acid primer.
ductus arteriosus The blood vessel between the pulmonary artery (carries blood from the heart to the lungs for oxygenation) and the aorta (carries oxygenated blood to the rest of the body). During gestation the ductus arteriosus bypasses the fetal lungs, and is normally sealed after birth.
ductus venosus The blood vessel between the umbilical vein and the caudal vena cava (carries oxygenated blood from the dam, bypassing the liver, through the vena cava to the heart of the fetus). It is normally sealed shortly after birth.
dysregulate Abnormal or impaired control of gene expression.
dystocia Abnormal or difficult labor.
ectoderm The outermost layer of tissue in a developing embryo that will eventually become the skin and/or other outer surface of the organism, the outermost parts of the nervous system, and various other outer and external organs depending on the organism.
embryo In mammals, the term is restricted to the structure present in the early part of gestation that develops into a fetus.
embryo cloning Another term for blastomere nuclear transfer.
empirical That which can be seen or observed alone, often without reliance on theory.
endoderm The innermost layer of tissue in a developing animal embryo that will eventually become the digestive tract, respiratory tract, and various other things depending on the organism.
enucleate Removal of an organ or mass from its supporting tissues.
epigenetic Describing any of the mechanisms regulating the expression and interaction of genes, particularly during the development process. These include changes that influence the phenotype but have arisen as a result of mechanisms such as inherited patterns of DNA methylation rather than differences in gene sequence: imprinting is an example of this.
epigenetic reprogramming In the case of somatic cell nuclear transfer (SCNT), the process of altering the instructions governing the expression of genes in the chromosomal DNA of the donor cell such that embryonic or totipotent ( able to differentiate along any line or into any type of cell) gene expression conditions are reestablished.
epigenetic variation/effects Non-hereditary, phenotypic changes in the expression in a single gene.
estrous Pertaining to estrus. (Adjective)
estrus The recurrent, restricted period of sexual receptivity in female mammals other than human females, marked by intense sexual urge. (Noun)
euchromatin One of two types of chromatin seen during interphase of the cell cycle. It is genetically active (transcription occurs in it) and less condensed than heterochromatin (the other type of chromatin).
eukaryote An organism whose cells have a true nucleus, i.e., one bounded by a nuclear membrane, within which lie the chromosomes, combined with proteins and exhibiting mitosis; eukaryotic cells also contain many membrane-bound compartments (organelles) in which cellular functions are performed.
F 1 Abbreviation for filial generation 1 (first generation). The initial hybrid generation resulting from a cross between two parents.
farrow In swine, the process of giving birth. Also used to describe a litter of pigs.
fat cow syndrome A multifactorial disease condition often occurring in dairy cows following parturition; associated with excessive mobilization of fat to the liver in well-conditioned cows. This mobilization is induced by the negative energy balance and hormonal changes. Presenting signs usually include depression, anorexia, weight loss, and weakness that can lead to recumbency.
fecundity The physiological ability to reproduce, as opposed to fertility.
fertility The capacity to conceive or induce conception.
foramen ovale A hole in the fetal heart between the right and left atria, for the purpose of bypassing the lungs. It is normally sealed shortly after birth.
founder animal An organism that serves as the progenitor of a particular lineage.
freemartin A sexually maldeveloped female calf born as a twin to a normal male calf. The reproductive tract hypoplasia results in an infantile uterus that does not develop appropriately with the growth of the rest of the calf and fails to respond to puberty. It is commonly sterile and intersexual as the result of male hormones reaching it through shared placental blood vessels.
gamete A mature reproductive cell capable of fusing with a cell of similar origin but of opposite sex to form a zygote from which a new organism can develop. Gametes normally have haploid chromosome content. In animals, a gamete is a sperm or egg.
gametogenesis The process of the formation of gametes.
gene expression The process by which a cell transcribes the information stored in its genome to carry out the functions of life.
genetic reprogramming The process of rearranging the genome of the nucleus to restore a cell’s totipotency so it can differentiate into different types of cells and develop into a whole organism. Also known as de-differentiation.
genetically engineered animals A subset of animals associated with molecular biology techniques. Includes transgenic animals, animals subjected to gene therapy and mosaic animals. This subset does not include animal clones.
genome The full set of genes in an individual, either haploid (the set derived from one parent) or diploid (the set derived from both parents).
genotype The entire genetic constitution of an individual.
germ cell A reproductive cell such as a spermatocyte or an oöcyte, or a cell that will develop into a reproductive cell.
gilt A female pig that is intended for breeding but has not yet given birth.
gonadotropin Any hormone that stimulates the testes or ovaries.
haploid An individual or cell having only one member of each pair of homologous chromosomes.
harm An adverse outcome.
hazard Something that can produce harm.
heifer A female bovine that has not yet produced a calf.
hematology The branch of medicine that deals with the blood and blood-forming tissues.
hemogram A written record or graphic representation of a detailed blood assessment such as the complete blood count or differential leukocyte count.
hermaphrodite An individual characterized by the presence of both male and female sex organs. The condition is caused by an anomalous differentiation of the gonads: an animal with ambiguous genitalia, typically a penis with ovaries or a vulva with testicles
heterochromatin The condensed and genetically inactivated portion of a chromosome.
histones Chromatin proteins commonly associated with the DNA of somatic cells in eukaryotes and they are involved in packaging of the DNA and the regulation of gene activity.
hormone A chemical substance produced in the body by an organ, cells of an organ, or scattered cells, having a specific regulatory effect on the activity of an organ or organs. The term was originally applied to substances secreted by endocrine glands and transported in the bloodstream to distant target organs, but later it was applied to various substances having similar actions but not produced by special glands.
hydroallantois A bnormal fluid accumulation in the allantoic cavity of the placenta. (See hydrops.)
hydrops Edema. H ydrops refers to a set of conditions relating to abnormal fluid accumulation in one or more compartments of the placenta and/or the fetus itself, and are alternatively referred to as hydroallantois, hydramnios or hydrops fetalis, depending on where the edema occurs.
hyperkeratosis Characterized by lesions of the superficial layers of the epidermis. These lesions rapidly become covered with scales, and then develop hard, dry crusts with deep fissures. Generally referred to as parakeratosis in swine.
hypoplasia Incomplete development or underdevelopment of an organ or tissue.
hypospadius A developmental anomaly in which the urethra opens inferior (below) to its usual location; usually seen in males with the opening on the underside of the penis or on the perineum.
imprinted genes Those genes whose degree of expression is determined by their derivation from either the dam or the sire.
in vitro Outside the organism, or in an artificial environment. This term applies, for example, to cells, tissues or organs cultured in glass or plastic containers.
in vivo Literally means "in life;” a biologic or biochemical process occurring within a living organism.
inner cell mass The group of cells in a blastocyst that are destined to form the fetus.
inner cell mass ( ICM) A cluster of cells within the blastocyst. The inner cell mass will form all of the tissues of the organism and these cells are pluripotent.
ketonuria Ketone bodies in the urine, as in diabetes mellitus; called also acetonuria and hyperketonuria.
ketosis A metabolic disease of lactating dairy cows characterized by weight loss, decreased milk production, and neurologic abnormalities that usually occur during the first 6 weeks of lactation.
Large Offspring Syndrome (LOS) A morphologic syndrome presumably expressed at the molecular and physiological level due to some alterations in embryonic gene expression. Animal clones with LOS may experience difficulties in developing and maintaining the placenta. An LOS fetus is unusually large for its species, has longer than usual gestation periods, and often has immature lungs or heart abnormalities. Kidneys and liver may also be affected.
leukocytosis A transient increase in the number of leukocytes (white blood cells) in the blood.
leukopenia A reduction in the number of leukocytes in the blood.
locus The specific site of a gene on a chromosome.
long terminal repeats A double-stranded sequence, generally several hundred base pairs long, at the two ends of the genetic sequence of retroviruses.
mastitis Inflammation of the mammary gland or breast.
meconium First stool in the intestine of a full-term fetus.
meiosis The process in which a single diploid cell becomes four haploid cells in two consecutive divisions of the nucleus of an eukaryotic cell. In multicellular higher organisms this occurs only in the progenitors of sex cells and never in somatic cells.
methylation The addition of a methyl group (-CH 3) to a larger molecule (e.g. cytosine methylation) cytosine 5-methyl cytosine
metritis Inflammation of the uterus.
mitosis The division of a eukaryotic cell nucleus to produce two daughter nuclei that contain identical numbers of chromosomes and that are identical genetically to the parent nucleus except where crossing over or mutation has occurred.
monozygotic twin One of a pair of twins derived from a single fertilized egg or zygote. Synonym: identical twin.
morphology The form and structure of an organism, organ, or part.
morula The solid mass of blastomeres formed from the cleavage of a fertilized ovum or egg.
murine Pertaining to or affecting mice or rats.
neoplasia Abnormal and uncontrolled cell growth that often produces a tumor (a neoplasm) that may or may not be cancerous (i.e., capable of spread or metastasis).
nuclear transfer Transferring the nucleus with its chromosomal DNA from one (donor) cell to another (recipient) cell.
nucleic acids A large molecule composed of nucleotide subunits. DNA ( deoxyribonucleic acid) and RNA ( ribonucleic acid) are examples.
nucleoside A molecule composed of a purine or pyrimidine nitrogenous base attached to the five-carbon sugar. This glycosylamine is a component of nucleic acids.
nucleotide A molecule composed of a purine or pyrimidine nitrogenous base attached to the five-carbon sugar which also has a phosphate group attached to it. It is the c onstitutional unit into which nucleic acids are broken down by partial hydrolysis and from which they are built.
nucleus The most conspicuous organelle of a eukaryotic cell; it contains the chromosomes and is the site of genomic DNA replication and or RNA synthesis in the cell.
oöcyte A cell of an animal ovary that undergoes meiosis to form an ovum.
oö plasmic remodeling After nuclear transfer, the cytoplasm of the oöcyte ( oöplasm) alters the morphology of the nucleus, so that it more closely resembles the nucleus of an embryo.
oö plast The remaining portion of the oöcyte following enucleation.
oviduct A tube from the ovary to the uterus through which ova (eggs) may pass.
ovum The female reproductive cell which, after fertilization, becomes a zygote that develops into a new member of the same species. Also called an egg.
parakeratosis A nutritional deficiency disease of 6- to 16-wk-old pigs that is characterized by lesions of the superficial layers of the epidermis. It is a metabolic disturbance resulting from a deficiency of zinc or an excess of calcium in the diet.
parity The condition of having given birth.
parthenogenesis The development of a new individual from an unfertilized female gamete.
parturition The act or process of giving birth to offspring.
patent ductus arteriosus The failure of the ductus arteriosus to close after birth resulting in extra blood flow to the lungs and recirculation of oxygenated blood to the lungs rather than the rest of the body.
patent urachus The failure or the urachus to close during parturition, resulting in the inability to excrete urinary waste.
phagocytosis The uptake of extracullular materials by the formation of a pocket from the cellular membrane and its subsequent pinching off.
phenotype The totality of the observable functional and structural characteristics of an organism as determined by its genotype and its interaction with its environment.
phytate(s) A form of phosphorus commonly occurring in grain products, which is indigestible in non-ruminant species.
placentomes Placental junctures consisting of the uterine caruncle and the placental cotyledon, which permits vascular transport of nutrients into and waste out of the fetal environment.
ploidy Degree of repetition of the basic number of chromosomes.
pluripotent Capable of differentiating into more than one cell type.
polar body A small cell containing little cytoplasm that is the by-product of o ö cyte meiosis in female animals.
polycythemia An increase in the total red cell mass of the blood.
polymorphism Describes a substance that can take on several different forms. Can refer to subtle differences in DNA sequences among individuals. It also may refer to a protein which can be coded by several different sequences; these variations do not ruin the protein's function.
polyploidy The state of a cell having more than two times the haploid number of chromosomes in its nucleus.
portal Anatomical nomenclature pertaining to an opening, especially the site of entrance to an organ of the blood vessels and other structures supplying or draining it.
predation The capturing and consumption of prey as a means of maintaining life.
pregnancy toxemia A pathologic metabolic disturbance of pregnancy that results when fetal carbohydrate or energy demand exceeds the maternal supply during the last trimester of pregnancy. Specific to sheep and goats.
preimplantation A period very early in embryo development, before the embryo attaches to the uterus.
progeny An animal derived from sexual reproduction that has at least one cloned animal as a parent (but could result from two cloned animals mating).
promoter A sequence of the DNA molecule to which RNA polymerase will bind and initiate transcription.
promoter A segment of DNA acting as a controlling element in the expression of a gene.
promoter-enhancer sequence A control element that can increase expression of a gene.
pronucleus The pronucleus is the structure that contains the haploid genome of the sperm or ovum after fertilization occurs, but before they fuse to make the nucleus of the zygote, or the single-celled diploid organism.
p-value A measure of the probability that a difference between groups during an experiment happened by chance.
recumbancy Lying down.
rendering Reducing, converting, or melting down animal by-products by heating; a cooking and drying process that yields fat of varying grades, both edible and inedible (depending on raw material source), and animal protein that is useful for animal feeds and fertilizer.
risk A set of conditions that links an exposure to the likelihood of an adverse outcome.
risk assessment The methodology used to characterize potential risks and the conditions that result in the potential to experience risk.
risk management The set of activities applied to identify and evaluate alternative strategies (often regulatory), and select among them on the basis of economic, political, scientific, ethical and social conditions or criteria.
RNA Abbreviation for ribonucleic acid that serves to carry information from DNA to other parts of the cell or that has other functions. The generation of messenger RNA is a critical step in gene expression.
RNA polymerase An enzyme that transcribes the information in a DNA sequence into RNA.
ruminant Animals having a rumen - a large digestive sac in which fibrous plant material is fermented by commensal microbes, prior to its digestion in a "true" stomach (the abomasum). Common farm ruminants are cattle and sheep.
SCNT Acronym for Somatic Cell Nuclear Transfer. The process of generating a live organism asexually by transferring the diploid nucleus of a somatic cell from a donor animal to the enucleated embryo of a recipient animal.
scours Severe diarrhea in farm animals.
senescence The process or condition of growing old in which cells, tissues, and organisms deteriorate and finally die.
sequellae Morbid conditions occurring as a consequence of another condition or event.
sexual reproduction The production of offspring by the fusion of male and female gametes (in contrast to ‘asexual reproduction’).
somatic cell Any cell of an organism other than a germ cell.
stem cell A totipotent or pluripotent cell that can replicate indefinitely and which can differentiate into other cells; stem cells serve as a continuous source of new cells.
stochastic Pertaining to a random process, used particularly to refer to a time series of random variables. Arrived at by skillful conjecture; e.g. a stochastic model, a stochastic process.
superovulate To produce numerous ova at one time.
telomerase A DNA polymerase enzyme that maintains the structure of the telomere by adding the required repetitive sequences to the ends of eukaryotic chromosomes.
telomere The structure that seals the end of a chromosome.
tetraploid An organism or cell containing four haploid sets of chromosomes (see polyploidy).
totipotent Capable of becoming any cell type in the body.
transcription The process by which a single-stranded RNA with a base sequence complementary to one strand of a double-stranded DNA is synthesized.
transgenic Contains heritable DNA from another source. A transgenic animal is one that has been intentionally altered using molecular biology techniques that result in heritable changes (insertions, deletions or rearrangements) in the nucleic acid sequence of the nucleus or mitochondria, and includes any offspring that inherit those changes.
translation The second major step of gene expression in which the particular sequence of bases in the transcribed mRNA determines the sequence of amino acids in the proteins (or polypeptides) being synthesized (see transcription).
transposable element A genetic element that has the ability to move (transpose) from one site on a chromosome to another.
trophectoderm The group of cells in the blastocyst that form the placenta and other non-fetal tissues.
trophoblast A layer of extra-embryonic ectodermal tissue on the outside of the blastocyst. It attaches the blastocyst to the endometrium of the uterine wall and supplies nutrition to the embryo.
urachus A structure through which a fetus excretes urinary waste. In normal development, this structure would close at the time of parturition.
ventricle (ventriculus) A small cavity or chamber within a body or organ, especially: (a) the chamber on the left side of the heart that receives oxygenated arterial blood from the left atrium and contracts to force it into the aorta; and (b) the chamber on the right side of the heart that receives deoxygenated venous blood from the right atrium and forces it into the pulmonary artery.
villi Microscopic vascular protrusions from the surface of a membrane.
wild type The phenotype that is characteristic of most of the members of a species occurring naturally and contrasting with the phenotype of a mutant.
xist Enzyme that deactivates one of the two X chromosomes in female embryos.
zona pellucida The thick, transparent, non-cellular outer layer surrounding an o öcyte and fertilized ovum.
zygote The diploid cell that results from the union of a sperm cell and an egg cell.

 115  The various sources used for these definitions include:  Dorland’s Medical Dictionary, 30th Ed., W.B. Saunders Company, Philadelphia, 2003; Dictionary of Epidemiology. 3rd Ed. John M. Last. Oxford University Press, 1995; HTTP://;; Large Animal Internal Medicine, 2nd Ed., Smith, B.P., Ed., Mosby – Year Book, Inc., St. Louis, 1996.; Veterinary Medicine: A Textbook of the Diseases of Cattle, Sheep, Pigs, Goats and Horses. 7th Ed. Blood, D. C. and O. M. Radostits, Philadelphia: Bailliere Tindall Company, 1989. The Merck Veterinary Manual, 8th Ed. Online Version.  C.M. Kanh and S Line, Ed. Merck & Co., Inc, NJ, 2003; and The American Heritage® Dictionary of the English Language, 4th Ed., Houghton Mifflin Company. 2002.

Page Last Updated: 09/26/2014
Note: If you need help accessing information in different file formats, see Instructions for Downloading Viewers and Players.