H

HTST (high-temperature short-time) The temperature and time combination for pasteurization of milk and milk products. The minimum for milk is 71.7øC (161øF) for at least 15 seconds. Higher temperatures are used in pasteurizing products of high solids because of the protection afforded
bacteria by solids.
Half-sib In genetics, a half brother or half sister. 
Handlers Processors or dealers of milk who commonly purchase raw milk and sell pasteurized milk and milk products. 
Hand milking The manual milking of an animal as opposed to mechanical milking. 
Hardware disease Commonly, an inflammation of the body cavity by an animal eating metal objects and perforation of the digestive tract.
Hay Dried forage (e.g., grasses, alfalfa, clovers) used for feeding farm animals. 
Haylage Low-moisture silage (35 to 55 percent moisture). Grass and legume crops are cut and wilted in the field to a lower moisture level than normal for grass silage, but the crop is not sufficiently dry for baling. It is commonly stored in a sealed, or airtight, storage system.
Heart girth The circumference of the body just back of the shoulders of an animal. It is used to estimate body weight. 
Heat See estrus. 
Heat increment (HI) The increase in heat produced following consumption of food. It consists of calories released in fermentation and nutrient metabolism. When environmental temperature is below critical temperature, this heat may be used to keep the body warm; therefore, it is not wasted. Also called work of digestion.
Heat period That period of time when a female will accept a male in the act of mating. Also called in heat or estrus. 
Hectare A metric unit of land measurement (2.47 acres). 
Heifer A bovine female less than three years of age who has not borne a calf. Young cows with their first calves are sometimes called first-calf heifers.
Herd A group of animals (especially cattle), collectively considered as a unit. 
Herd average Average milk and component production per cow for all cows in the herd unit for 12 months. 
Herd code An exclusive reference number that identifies every DHI herd. The first two numbers identify the state, the next two, the association, and the final numerical series identifies the herd within an association.
Herd owner The declared owner of a herd of dairy cattle as recorded on a legal document, registration papers or other official documents.
Herdmate comparison Method of estimating the genetic transmitting ability in which a cow's yield is compared to that of other cows in the same breed from different sires that calved in the same herd during the same season.
Heritability The proportion (fraction) of difference among animals for a trait, such as milk production, due to genetic difference rather than environmental factors. The fraction of variation in a trait that is genetically transmissible from parent to offspring.
Herringbone milking parlor A raised, zigzag-designed milking stall which allows the group milking of several cows at one time in a pipeline milking system.
High-moisture silage Silage usually containing 70 percent or more moisture. 
Holding area An area to hold cows prior to entry into the milking parlor. Sometimes called a holding pen. May also include a wash pen.
Homogenized milk Milk that has been treated to ensure breakup of fat globules to such an extent that, after 48 hours of quiescent storage at 7øC, no visible cream separation occurs on the milk. The reduced size of fat particles results in formation of a softer curd in the stomach.
Hundredweight (cwt.) Generally refers to milk sold off the farm in 100 pound units. 
Hybrid vigor (heterosis) The increased growth or production exhibited by the first generation over the average of its two parent breeds. It is usually expressed as a percentage.
Hypocalcemia See parturient paresis. 
Hypoglycemia Below normal blood glucose level.