LABOR - A period of time during which the fetus(es) is expelled from the body of the mother. Labor may be divided into distinct stages: dilatation, expulsion, and placental. The dilatation stage begins with the onset of regular uterine contractions and ends when the birth canal is completely prepared for passage of the fetus. The expulsion stage starts when the fetus begins to move through the birth canal and ends when it is completely expelled from the mother's body. The placental stage begins at the end of the expulsion stage and ends when the placenta and membranes have been expelled. L10102. Definition from Hurnik et al., 1995.

LABORING ACTION (horse) - Locomotion performed with or requiring excessive effort. Compare: Free Going. L10103. Definition from Hurnik et al., 1995.

LACRIMAL REFLEX - Increased production of tears in response to corneal irritation. L10105. Definition from Hurnik et al., 1995.

LACTATION - The act of secretion of milk or the period of secretion of milk. L10106. Definition from Hurnik et al., 1995.

LAMB - A young sheep up to one year of age L10110. Definition from Hurnik et al., 1995.

LAMBING - Parturition in sheep. L10111. Definition from Hurnik et al., 1995.

LAMENESS - Deviation from normal gaits caused by injury or disease (e.g., foot-and-mouth disease, laminitis, milk lameness, etc.). Lameness can be further subdivided into supportive or suspensory lameness, and sudden, progressive or chronic lameness. Also see specific lameness - CHRONIC; PROGRESSIVE; SUDDEN; SUPPORTIVE; SUSPENSORY. L10112. Definition from Hurnik et al., 1995.

LANDAU INDEX - A procedure for quantifying a social hierarchy, calculated as the degree of deviation from a linear dominance order. L10201. Definition from Hurnik et al., 1995.

LATERAL - Pertaining to a position to the side of the median part of a body. L10209. Definition from Hurnik et al., 1995.

LATERAL GAIT - A gait in which the lateral pairs of legs move at the same time (e.g., pace). L10210. Definition from Hurnik et al., 1995.

LATERAL RECUMBENCY - Lying characterized by full lateral contact of the body trunk, neck, head, and legs on one side with the ground. The neck, head, and legs are usually extended during lateral recumbency. The frequency of lateral recumbency varies among different species of farm animals and different age groups and may also be influenced by environmental circumstances (e.g., type of ground surface, ambient temperature, time of day). L10211. Definition from Hurnik et al., 1995.

LAYING, EGG - See Oviposition. L10215. Definition from Hurnik et al., 1995.

LD CYCLE - A cycle with alternating light and dark periods. LD 16:8 designates 16 hours of light alternating with 8 hours of darkness. LL and DD designate continuous illumination or continuous darkness, respectively. L10216. Definition from Hurnik et al., 1995.

LEADERSHIP - The ability of an individual to control or direct the behavior of he members of a group. L10301. Definition from Hurnik et al., 1995.

LEADING LEG - The foreleg in a canter or gallop that is not diagonally synchronized with one of the hind legs and lands last in the gait sequence. In an animal traversing a circle, the leading leg is typically that on the inside of the circle. L10302. Definition from Hurnik et al., 1995.

LEANING - Partial support of the head or body on some object such as a wall, fence, or animal, achieved by shifting the center of gravity horizontally From a point of balance over the legs. L10303. Definition from Hurnik et al., 1995.

LEARNED BEHAVIOR - Any action performed as a result of, or influenced by, experience. This does not mean that learning is independent of inheritance, since the ability to collect, memorize, and utilize information for the learning process is influenced by genotype. L10304. Definition from Hurnik et al., 1995.

LEARNED HELPLESSNESS - A phenomenon that may occur when avoidance or reduction of some aversive stimulation is impossible or extremely difficult for the subject. Learned helplessness is manifested by continued acceptance of such stimulation even when the situation subsequently provides opportunity for an avoidance response. L10306. Definition from Hurnik et al., 1995.

LEARNED PREFERENCE - Any preference influenced by a conditioning process. L10307. Definition from Hurnik et al., 1995.

LEARNING - The ontogenic process of attainment and memorization of information. Also see specific learning - INCIDENTAL; INSIGHT; LATENT; MOTOR; OBSERVATIONAL; PERCEPTUAL; PREPROGRAMMED. L10308. Definition from Hurnik et al., 1995.

LEARNING CURVE - Graphic illustration of changes in an animal' s responsiveness to the learning process, arranged according to consecutive units of practice. L10309. Definition from Hurnik et al., 1995.

LEARNING DISPOSITION - A theoretical concept referring to propensity of an organism to acquire associations in a given situation. The learning disposition of an organism is determined by genetic makeup, psychological and physical condition, and prior learning. L10310. Definition from Hurnik et al., 1995.

LEARNING SET - Mental representation of a principle common to a series of learning trials such that, although circumstances may differ between trials, the solution to each is governed by the common principle. An animal is considered to have acquired a learning set when it apprehends the principle. L10312. Definition from Hurnik et al., 1995.

LEE-BOOT EFFECT - Suppression of initiation of estrous behavior by overcrowding of animals. L10313. Definition from Hurnik et al., 1995.

LEG DROP (horse) - An action in which a horse rapidly tucks a leg under its body, and lowers itself somewhat toward the quarter with the tucked leg. The leg drop is performed to avoid bites directed at the legs in aggressive social encounters. L10314. Definition from Hurnik et al., 1995.

LEG LEADING - See Leading Leg. L10401. Definition from Hurnik et al., 1995.

LEG WEAKNESS SYNDROME - A clinical term for a variety of defects in the structure and function of the legs (e.g., broad hips, narrow lumbar area, hypermobility of joints, abnormal angulation of the foot, etc.). Behavioral symptoms are difficult rising from recumbency, staggering gait, inability to maintain positional balance, extended period of recumbency, and paresis. L10402. Definition from Hurnik et al., 1995.

LEG YIELDING (horse) - A dressage maneuver in which the axis of the horse's body is maintained at about 30 degrees from the direction of movement. The head of the horse is slightly bent at the poll so that it points even farther from the direction of movement. L10403. Definition from Hurnik et al., 1995.

LESION - Severe damage or loss of tissue characterized by discontinuity of the tissue's function. L10406. Definition from Hurnik et al., 1995.

LETHARGY - A state of pronounced drowsiness or loss of desire to act. L10409. Definition from Hurnik et al., 1995.

LETHISIMULATION - Complete temporary immobilization of an animal, visually approximating its death, induced by a sudden and inescapable exposure to a strong fear causing stimulus. L10410. Definition from Hurnik et al., 1995.

LEVADE (horse) - A dressage exercise of the Spanish High Riding School in which the horse raises the anterior portion of its body (approx.30 degrees) with its hind legs spread apart and bent at the hocks, and the forelegs folded underneath the chest L10412. Definition from Hurnik et al., 1995.

LIBIDO - Sexual motivation. The level of libido often is assessed from the reaction time between first detection of a sexual partner and first mounting attempt by the mate or display of receptivity posture by the female. L10414. Definition from Hurnik et al., 1995.

LICKING - An action whereby the tongue is slid over the surface of an object. Licking may have a nutritional, gustatory, prophylactic, or social function and also may develop as a stereotyped behavior pattern. Licking consists of self-licking (an animal licks its own body) or social licking (an animal licks is sexual licking which occurs predominantly during courtship and estrus. Also see specific licking - SEXUAL; SOCIAL. L10415. Definition from Hurnik et al., 1995.

LICKING SYNDROME - Excessive occurrence of social licking, assumed to be an indication of sodium deficiency. L10501. Definition from Hurnik et al., 1995.

LIE - To assume or maintain a recumbent position. The behavior patterns involved in lying down show a high degree of uniformity within species, hut may be modified by environmental circumstances (e.g., restriction of movement, injury). The posture when lying can be categorized as lateral recumbency, semi-lateral recumbency, or ventral or sternal recumbency. The body position of a recumbent animal may reflect health status (e.g., unusual posture to prevent pressure on an injured or inflamed area), level of exhaustion (e.g., selecriveness of place to lie and tendency to adopt lateral recumbency), degree of thermal comfort (e.g., the area of exposed body surface), and level of relaxation (e.g., position of the head, eyelids, or limbs). L10502. Definition from Hurnik et al., 1995.

LIFT, REAR-LEG (horse) - See Rear-leg Lift. L10505. Definition from Hurnik et al., 1995.

LIGHT - Radiant energy in the range of frequencies that stimulates visual receptors. L10506. Definition from Hurnik et al., 1995.

LIGHT REFLEX - Contraction of the pupil when exposed to light. L10508. Definition from Hurnik et al., 1995.

LIGNOPHAGIA - The eating of wood or wooden substances.Lignophagia is commonly identified as wood gnawing. L10509. Definition from Hurnik et al., 1995.

LIMITED FEEDING - Any feeding program that provides less feed than the animals would consume ad libitum. Such a program frequently is used to prevent excessive fattening of animals. Synonym: Restricted Feeding. L10513. Definition from Hurnik et al., 1995.

LIMINAL SENSITIVITY - The lowest level of stimulation that evokes a detectable response. L10511. Definition from Hurnik et al., 1995.

LIMITED FEEDING - Any feeding program that provides less feed than the animals would consume ad libitum. Such a program frequently is used to prevent excessive fattening of animals. Synonym: Restricted Feeding. L10513. Definition from Hurnik et al., 1995.

LINE - A group of animals interrelated through an ancestor(s) and possessing some common genetic and phenotypic characteristics. L10514. Definition from Hurnik et al., 1995.

LINEAR HIERARCHY - A type of social hierarchy formed as a straight rank. The highest ranking animal dominates all, the second highest all but the first, the third highest all but the first two, etc., down to the animal subordinate to all. L10515. Definition from Hurnik et al., 1995.

LIP-CURLING - A response to pheromones, manifested by inhalation followed by distinct upward curling of the upper lip and dorsiflexion of the neck. Lip-curling is most noticeable in male ungulates when in proximity to estrous also be exhibited by female bovines when close to estrous peers. Synonym: Flehmen. L10604. Definition from Hurnik et al., 1995.

LIP SMACKING (horse) - A rhythmical smacking action of the lower lip toward the upper lip. Lip smacking is exhibited by some horses when under saddle or in unfamiliar environments. Lip smacking is thought to be indicative of mild excitement and is considered to be a nuisance vice. L10606. Definition from Hurnik et al., 1995.

LISTEN - To attend to sound stimuli. L10607. Definition from Hurnik et al., 1995.

LITTER - A group of siblings born during one parturition period. Also see specific litter - DEEP. L10609. Definition from Hurnik et al., 1995.

LIVESTOCK - Farm animals used for production purposes. L10610. Definition from Hurnik et al., 1995.

LOCALITY MEMORY - The ability of an organism to identify particular areas. L10612. Definition from Hurnik et al., 1995.

LOCOMOTION - The activity of an organism moving itself between points in space. Also see specific locomotion - DIGITIGRADE; PLANTIGRADE; RICOCHETAL. L10616. Definition from Hurnik et al., 1995.

LOLLING, TONGUE - See Tongue Lolling. L10703. Definition from Hurnik et al., 1995.

LOOSE HOUSING - A housing system where animals are not restricted in ambulation within a pen. L10705. Definition from Hurnik et al., 1995.

LORDOSIS - Dorsiflexion of the spine occurring during the stage of sexual receptivity of females of some mammalian species. L10706. Definition from Hurnik et al., 1995.

LOW SET - A term used to designate a short-legged animal L10708. Definition from Hurnik et al., 1995.

LYING - Maintaining a recumbent position L10715. Definition from Hurnik et al., 1995.

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