G

GPD (gaseous products of digestion) These include the combustible gases produced in the digestive tract during fermentation of the ration. Methane constitutes the major proportion of the combustible gases produced by ruminants; however, nonruminants also produce methane. Trace amounts of hydrogen, carbon monoxide, acetone, ethane, and hydrogen sulfide are also produced.
Galactopoietic Stimulating or increasing secretion of milk. 
Garget A common term for an inflammation of the udder of cows or the resulting abnormal milk. More accurately referred to as mastitis.
Gastroenteritis Chemical, bacterial, or viral inflammation of the mucosa of the stomach and intestines. 
Genetic appraisal Cows and sires are evaluated by researchers at the Animal Improvement Programs Laboratory, ARS-USDA, to determine their genetic values. (See PTA and PPA).
Genetic base The average genetic merit of a population (usually a breed) at a specific period, which is used as a reference point to express a genetic difference from a base population (genetic merit of cows and bulls).
Genetic merit The genetic value of the animal used in a breeding program. (Also see breeding value). 
Genetic trend Genetic change per year for a trait in the population. 
Genotype The actual genetic constitution (makeup) of an individual as determined by its germ plasm. For example, there are two genotypes for black-and-white Holsteins--BB and Bb. See dominant.
Gestation Pregnancy (gravidity). The period from conception to birth. The period of fetal development betweenfertilization of the ovum and birth of the offspring.
Get The offspring of a male. A get-of-sire refers to given number (commonly four) of progeny from a sire. 
Ghee Concentrated milk fat prepared by melting butter, decanting the fat after gravity separation from the serum, and driving off most of the remaining moisture by heating. About 1 percent moisture remains. It is used mostly in Asia and Africa.
Giving milk Lactating, or the act of yielding milk by a mammal. 
Goitrogenic Producing or tending to produce goiter (enlargement of the thyroid gland). 
Gossypol A toxic yellow pigment found in cottonseed. Heat and pressure tend to bind it with protein and thereby render it safe for animal consumption.
Grade Animals showing the predominant characteristics of a given breed. They usually have at least one purebred parent, ordinarily the bull.
Grade A milk Milk produced and processed under rigid sanitary regulations. Milking and processing facilities are approved and inspected by public health officials. Fluid milk products must meet this inspection standard.
Grade cattle An animal possessing the distinct characteristic of a particular breed but not registered with a breed association. Sometimes called commercial cattle.
Grading up The continued use of purebred sires on grade dams. 
Grass tetany A magnesium-deficiency disease of cattle characterized by hyperirritability, muscular spasms of legs, and convulsions.
Graze To consume standing vegetation, as by livestock or wild animals. 
Green cheese A term applied to the fresh uncured product. It refers to flavor, odor, body, and texture, not color. 
Green chop (fresh forage) Forages harvested (cut and chopped) in the field and hauled to livestock. This minimizes the loss of moisture, color, nutrients, and wastage. Also called zero grazing or soilage.
Gross energy (GE) The amount of heat, measured in calories, released when a substance is completely oxidized in a bomb calorimeter.
Growthy Describes an animal that is large and well-developed for its age.