I

IP See intake protein. 
IU (international unit) A unit of measurement of a biologic (e.g., a vitamin, hormone, antibiotic, antitoxin) as defined by the International Conference for Unification of Formulae. Potency is based on bioassay that produces a particular effect agreed on internationally. Also called USP unit.
Ice milk A frozen product resembling ice cream, except that it contains less fat (2 to 5 percent versus 10 percent) and more SNF (12 percent versus 10 percent) than ice cream. Both ice milk and ice cream contain stabilizers and emulsifiers and about 15 percent sugar.
Imitation milks Mixtures of nondairy ingredients (other than milk, milk fat, and nonfat milk solids) which are combined forming a product similar to milk, lowfat milk, or skim milk. Sodium caseinate, though derived from milk, is commonly termed a nondairy ingredient and is often used as a source of protein in imitation milks. Vegetable oils are commonly used as the source of fat.
Immunity The power an animal has to resist and/or overcome an infection to which most of its species is susceptible. Active immunity is attributable to the presence of antibodies formed by an animal in response to antigenetic stimulus. Passive immunity is produced by the administration of preformed antibodies.
Impaction Constipation. See compaction. 
Incomplete record A cow's production in a lactation that is terminated early for some reason. (Lactations not yet completed may be referred to as a "record in progress.")
Individual handler pool See pool, individual handler. 
Induced lactation A lactation that is artificially initiated by the use of hormones, not by birth. 
In milk Designating a lactating female. 
Intake protein (IP) Total protein or nitrogen consumed without regard to quality. 
In vitro Within an artificial environment, as within a test tube. 
In vivo Within the living body. 
Involution A decline in size or activity of tissues and/or organs. For example, the mammary gland tissues normally involute with advancing lactation. It is part of the process of lactating cows wherein they dry off. 
Iodinated casein Milk protein (casein) to which iodine is bound. It is commonly referred to a thyroprotein and can be used to stimulate dairy cows to secrete more milk.

K

Ketonuria The presence of ketone bodies in the urine, as with ketosis in high-producing cows. 
Ketosis See acetonemia. 
Kid A goat up to one year old. 
Kidding Parturition in the goat; the act of giving birth to young. 
Kilocalorie (kcal) Equivalent to 1000 calories.