DS 825 Ruminant Nutrition Physiology DS 825 Ruminant Nutrition Physiology Glossary

Condition characterized by a low rumen pH (below 6). The normal rumen function are impeded usually because too much concentrates were fed.

A latin word that means "to one's pleasure." In nutrition, ad libitum (abbreviated "ad Lib") refers to feeding management in which animals are fed without restriction. Cows are usually considered fed ad libitum when the refusals (orts) amount to approximately 5 to 10% of what has been offered the day before.

One of the 20 building block units of protein. Amino acids contain both an amino group (NH₂) and an acid or carboxyl group (COOH).

Protein released in the blood that is generated in reaction to a foreign protein (antigen) that has entered the body. Antibodies produce immunity against certain micro-organisms or their toxins.

Any of a group of chemical compounds, including sugars, starches, and cellulose, containing only carbon, hydrogen, and oxygen, with a ratio of hydrogen to oxygen of 2:1.

A gas produced by combustion or oxidation of organic matter. Carbon dioxide is also produced in large quantities during ruminal fermentation.

A measure of the amount of protein in a feed determined as the amount of nitrogen multiplied by 6.25. The factor 6.25 is the average grams of protein that contains 1 gram of nitrogen. The word "crude" refers to the fact that not all nitrogen in most feed is exclusively in the form of protein. Because most feeds contain non-protein nitrogen (NPN), crude protein generally overestimates the actual protein content of a feed.

A measure of the concentration of matter per unit of volume (e.g., g/l or kg/m3)

Pathologically excessive evacuation of watery feces. Diarrhea may be due to an infectious agent (bacterial infection) or a dietary imbalance.

The mixture of digestive secretion, bacterial population and feeds undergoing digestion in the gastro-intestinal tract (such as rumen content).

A measure of the proportion of a feed that is digestible. The digestibility of a nutrient is often measured as the difference between the amount of nutrient ingested minus the amount of nutrient excreted in the feces, expressed as a percentage of the nutrient ingested: 100 x (intake - excreted)/intake.

A non-lactating cow. The dry period is the time between lactation, when the cow is not secreting milk.

That part of the feed which is not water. It is usually determined by the residual weight of a sample placed for a period of time in a drying oven that removes the water from the sample. Usually, the dry matter content of a feed is expressed as a percentage. For example, an hay of 85% dry matter contains 85 g of dry matter for each 100 g of fresh feed.

A method of expressing the concentration of a nutrient in a feed. For example, a feed containing 12% crude protein on a dry matter basis contains 12 g of protein for each 100 g of feed dry matter

Quantity of dry matter ingested by a cow in a 24 h period. For example, a cow eating 18 kg of grass silage of 33% of dry matter ingest 18 x 0.33 = 6 kg of grass silage dry matter.

First part of the small intestine. The secretions of the liver and pancreas are discharged into the duodenum.

The nutritive tissue of a plant seed, surrounding and absorbed by the embryo.

A measure of the concentration of energy in a feed or a ration usually expressed as a unit of energy (megacalorie or megajoule) per lb of dry matter or per kg of dry matter.

A chain of carbon terminated by an acid (carboxyl) group (COOH). Fatty acids with less than 4 carbon units are volatile. Fatty acids with 5 to 20 carbon units are usually found as part of fats and oils.

Nutrient of low energy density present in large quantities in forages. Fiber is composed of structural carbohydrates (cellulose and hemicellulose) and phenolic compounds. Fiber is important for dairy cows because they stimulate rumination and promote a healthy rumen environment for bacterial growth. However, in large amounts in the diet, fiber may fill the rumen, limit intake of energy and constrain milk production.

Hemicellulose and cellulose that can be quantify by the neutral detergent fiber procedure.

Coarse feeds, such as straw, corn or sorghum stalks.

A period of 9 to 24 hours preceding the ovulation during which cows are receptive to bulls and exhibit a typical behavior of mounting other cows or standing when mounted by other cows (or a bull).

Strong acid secreted by the abomasum that breaks down chemical bounds and thus contributes to the digestion of feeds.

Decomposition of a chemical compound by reaction with water.

Any of the numerous fat or fat-like materials that are generally insoluble in water, but soluble in common organic solvents. Nutritionally, lipids contain about 2.25 times more energy then carbohydrates.

A diet that supplies the nutrients required to maintain vital functions (heart beat, respiration) and assure a constant body temperature.

Morbidity is an incidence of ill health. It is measured in various ways, often by the probability that a randomly selected individual in a population at some date and location would become seriously ill in some period of time. Contrast to mortality.

A measure of the amount of cell wall in a feed determined by a laboratory procedure. Neutral detergent fiber includes cellulose, hemicellulose and lignin.

Carbohydrates that are not part of the neutral detergent fiber, but generally accumulate in the plant as energy reserve (e.g., starch). These carbohydrates usually are more rapidly and more completely digested than the fibrous carbohydrates (syn Non-structural carbohydrate).

(see non-fiber carbohydrate).

1. At least 2 but not more that 100 amino acids linked together by a peptic bound. 2. Product of pepsin digestion of proteins.

Organic substance in which the carbon atoms are linked together in a ring structure (also called aromatic structure). Lignin is an example of phenolic compound.

The structure that contains the seeds of leguminous plants. It usually splits open after drying of the plant.

The part of a plant embryo that develops into the primary root.

A fertilized and ripened plant ovule containing an embryo capable of germinating to produce a new plant.

Standard deviation (SD) is a measure of the dispersion of a set of data from its mean. If the data points are further from the mean, there is higher deviation within the data set. The SD shares the same unit as the mean. The SD is calculated as the square root of variance by determining the variation between each data point relative to the mean. The symbol for standard deviation is σ (the Greek letter sigma). Approximately, in a normal distribution,
38% of all observations are within ± 0.5 SD units of the mean;
68% of all observations are within ± 1 SD units of the mean;
95% of all observations are within ± 2 SD units of the mean;
99% of all observations are within ± 3 SDunits of the mean.

(see Fibrous carbohydrate).

A two-lobed gland located in the throat and secreting the hormone thyroxin, which regulates the iodine metabolism in the body.

Method of AI breeding in which the timing of artificial insemination (AI) is based on a hormonal protocol that synchronizes the timing of ovulation. This is in contrast to timing insemination based on direct or indirect detection of estrous behavior. Hormonal protocols for Timed AI were developed in 1995 and have been widely adopted by dairy producers for reproductive management.

Mixture of the forages, concentrates, minerals and vitamin supplements of a ration. The total mixed ration has the advantage of offering a balanced ration at each meal rather than on a 24 h basis.

A fat composed of three fatty acids and glycerol.

Mammary gland of a cow.

Usually refers to feeding insufficient energy.

Fat containing fatty acids that can accept hydrogen atoms to saturate their structure (e.g., oleic, linoleic, linolenic and arachidonic acids).

Particles that carry cholesterol and fat throughout the bloodstream. These particles are released from the liver into the bloodstream. They are similar to chylomicrons which originate from the gut because they both carry cholesterol and triglycerides which are gradually released in the bloodstream to be absorbed by body cells along the way. In the process of losing triglycerides, the VLDLs grow smaller and turn into LDLs (Low Density Lipoprotein) which have lost all their triglycerides.

Products of fermentation of carbohydrates (and some amino acids) by the rumen microorganisms. Acetic acid, propionic acid and butyric acid are the primary volatile fatty acids which are absorbed through the rumen wall and used as an energy source by the cow.

The number of days between calving and first attempt to breed a cow. A typical voluntary waiting period is 45 days. However, it may varies from less than 40 to 80 days depending on farmer’s preference and reproductive protocol in place on the farm.