L

Lachrymation The act of tearing; secreting and conveying tears. 
Lactate To secrete or produce milk; also, salt of beta-hydroxy propionic acid. 
Lactation average Actual 305-day average milk and component production for all cows in the herd that was completed during a 12-month period. (Since dry days are not included, lactation averages usually are 8 to 15 percent higher than rolling herd averages.)
Lactation period The number of days an animal secretes milk following each parturition. Usually 11 to 12 months. 
Lactation record The total milk and components produced by a cow beginning on the day of calving and ending on the day the cow goes dry. For purposes of genetic comparison, 10-month (305-day) lactation records are the standard of the industry. A 306 to 365-day lactation record may be used for promotion. Lactation records greater than 365 days will not be published.
Lactation totals to date The production totals for milk and components through the current test date. 
Lactogenic Stimulating the secretion of milk. 
Lactose The 12-carbon sugar unique to milk; a disaccharide composed of glucose and galactose. Average milk contains about 5 percent lactose which varies little by breed.
Lactose intolerance A condition in which lactose is not adequately hydrolyzed in the intestine because of insufficient lactase enzyme.
Lagoon see anaerobic treatment lagoon. 
Leaching The process of removal of soluble materials by the passage of water through soil. 
Lead feeding Gradually increasing grain fed cows to a level equal 1.0 to 1.5 percent of body weight beginning about three weeks prior to the predicted calving date. Following parturition, grain is increased until a cow reaches maximum feed intake. Also called challenge feeding.
Legume Clovers, alfalfa, and similar crops that can absorb nitrogen directly from the atmosphere through action of bacteria that live in their roots and use it as a nutrient for growth.
Letdown The process in a cow where physical stimulation causes a release of oxytocin and the contraction of smooth muscles surrounding milk alveoli resulting in fluid pressure within the udder and milk flow.
Libido Sexual desire or instinct. 
Lifetime production totals The production totals for milk and components for a cow since her first calving (or first time on DHI test). Totals will include production beyond 365 days in a lactation, production credits for an abnormally initiated record and any production from prepartum milking.
Lignin A compound which, with cellulose, forms the cell walls of plants. It is practically indigestible. 
Linear score (SCC) Linear scores for somatic cell counts (SCC's) convert SCC logarithmically from cells per milliliter to a linear score from 0 to 9. The linear score has a straight line, inverse relationship with milk yield. An increase of one in the linear score is associated with a 400-pound decrease in lactation milk yield or a 1.5 pound drop in daily yield.
Liner A flexible sleeve in the milking teat cup or rigid-walled liner holder. Responsible for massaging the teat end and intermittantly cutting vacuum at the teat end during milking. Also called inflation.
Liner slip Slippage of the liner and teat cup during milking. Caused a sharp change of milking vacuum within the unit or cluster.
Lipid Any one of a group of organic substances that are insoluble in water though soluble in alcohol, ether, chloroform, and other fat solvents, and have a greasy feel. They are rich sources of dietary energy.
Liquid-solid separation The process of passing a liquid-solid suspension, such as animal manure, over a screen or similar device to partially remove solids prior to storage or application.
Loafing (area) (alley) (barn) (shed) A resting area for cattle. 
Long feed Coarse or unchopped feed such as hay, as contrasted with short, or chopped, feed. 
Long test interval Routinely, tests are conducted each 15 to 45 days, or approximately one each month. An emergency or supervisor vacation schedules may extend the interval beyond 45 days. For herds on official plans, reasons for a long test interval (46 to 75 days) must be reported on the
barnsheet by the supervisor. Official status of the record is lost if the interval exceeds 75 days.
Loose housing Facilities which allow cattle access to a large, open bedded area for resting. Also known as free housing. Loose housing provides at least 200 square feet per animal for feeding and resting while freestall housing uses only 90 square feet per animal.
Lowfat milk Milk containing at least 8.25 percent solids and from which sufficient milk fat has been removed to produce, within limits of good manufacturing practice, a milk fat content of 0.5, 1.0, or 2.0 percent.
Low-moisture silage Silage that contains 35 to 55 percent moisture. See haylage. 
Lucerne Alfalfa (Medicago sativa); a legume of high feeding value for ruminants.