Beef Cattle Introduction
Beef cattle are domesticated animals under two orders; Bos indicus and Bos taurus. The breeds under Bos indicus include the Brahman, Brangus, Beefmaster, Santa Gertrudis, and Simbrah. Examples of breeds under Bos taurus include Angus, Hereford, Shorthorn, Braunvieh, Charolais, Chianina, Limousin, Maine Anjou, and Simmental. Beef cattle are evaluated with a body condition score (BCS) rangeof 1-9. Those beef cattle with a score of 5, 6, or 7 are considered good body conditions. Below 5 is too thin and above 7 is too fat. A cow is female that has given birth to calves. A heifer has yet to give birth to a calf. A bull is a male.
Digestive System
![Ruminant stomach flow of digesta Picture](/uploads/5/6/7/3/56734417/4240792.png?1437343566)
Cattle are considered ruminants. This type of digestive system consists of the mouth, esophagus, a complex four compartment stomach, small intestine, and large intestine (Figure 1).
Four steps to Rumination
Rumination is an important factor for all ruminants, as it allows the animal to forage and eat rapidly, and then store for later digestion. Rumination time average for grazing animals consist of eating for 8 hours, ruminating for 8 hours, and resting for 8 hours. Feed is more readily digested by rumen microbes when particle size is reduced, thus the four R's of ruminant digestion are important processes for every ruminant. The four R's of ruminant digestion include:
Four steps to Rumination
- Rumen: Located on the left side of cattle, the rumen is also known as the fermentation vat. This vat holds a large number of microorganisms (bacteria and protozoa) which do the majority of digestion in the rumen. The inside of the rumen is covered with papilli (imagine a deep pile carpet) which create more surface area and allow more room for absorption of nutrients. The average cow can hold 40-50 gallons in there rumen.
- Reticulum: Has a two part job in the stomach, known as the "traffic cop." It is located in the more cranial area of the body cavity and looks like honeycomb. The reticulum receives feed stuffs from the esophagus and sends it to the rumen. It also receives partially digested feeds from the rumen and sends these down to the omasum. A cow with "hardware disease" will have a problem here in the reticulum. This disease occurs when a cow eats metal like nails or other sharp objects, and they end up in the reticulum. Using a magnet or surgery are the only ways to extract the objects. If not removed, infection and/or death of the animal will occur. About 2 gallons is all that a cow can hold in the reticulum.
- Omasum: Known as "many plies" or "pages of a book," the omasum absorbs water and other substances from the digestive contents. Feed material (ingesta) is drier within the folds of the omasum than other compartments. Ingesta here is also grinded up to smaller particles that then passes to the abomasum. The omasum can hold about 4 gallons of ingesta.
- Abomasum: The true stomach of cattle, the abomasum works similarly to that of non-ruminants. Like humans, the abomasum contains hydrochloric acid and other digestive enzymes to help break down ingesta. It is the only compartment of the stomach that has a glandular lining. Like the omasum, the abomasum can hold about 4 gallons of ingesta at any one time.
Rumination is an important factor for all ruminants, as it allows the animal to forage and eat rapidly, and then store for later digestion. Rumination time average for grazing animals consist of eating for 8 hours, ruminating for 8 hours, and resting for 8 hours. Feed is more readily digested by rumen microbes when particle size is reduced, thus the four R's of ruminant digestion are important processes for every ruminant. The four R's of ruminant digestion include:
- Regurgitation: The process of reverse peristalsis, where food is carried back to the mouth. Stimulus for this process occurs when digesta in fiber mat scratches the surface near the cardiac sphincter of esophagus. Contraction of the reticulum forces digesta to the sphincter and the animal inhales with the epiglottis closed to produce a vacuum. This vacuum causes the cardiac sphincter to open and esophagus dilates allowing rapid reverse peristalsis of digesta to the mouth. Once at the mouth, remastication begins.
- Remastication: Digesta that has just been regurgitated is now rechewed during this process. The digesta, known as a bolus, is chewed slower in order to reduce particle size.
- Reinsalivation: During remastication, digesta is reinsalivated to break down particles easier. Parotid glands secrete more saliva during this time than when eating initially. Saliva provides liquid for the microbial population and a buffer for the rumen. This buffer helps maintain a rumen pH between 6.2 and 6.8 for optimum digestion of forages and feedstuffs.
- Redeglutition: Swallowing the bolus this time includes smaller particles and more liquids. The rumen contracts to move the bolus into the rumen.
Calf Digestive System
![Calf digestive system Picture](/uploads/5/6/7/3/56734417/1202401.png?472)
Calf digestion is more similar to that of non-ruminants due to their underdeveloped rumen, reticulum, and omasum from birth to the first few weeks of life. This is because the abomasum is doing almost all the work in the young calf. During nursing or feeding from a bucket, milk bypasses the rumen via the esopageal groove and passes directly into the abomasum (Figure 2). Once a calf begins consuming grains and forage, a microbial population becomes established in the rumen and reticulum causing the compartments to begin development. Most feeding programs begin the calf on solid feed stuffs as early as 3 weeks of age. At 3 months of age the rumen becomes larger and more heavily covered in papillae that it begins functioning like the adult.
Nutrients
Water is essential for all animals, but it's importance in the beef cattle is it's use in the digestive tract. Energy provides the body with the ability to do work. Work includes digestion, lactation, reproduction, and movement. It is required by cattle in the greatest amount and is usually expressed at % Total Digestible Nutrients (TDN). Primary sources of energy for beef cattle is found in roughages and starch from grains, which contain cellulose and hemicellulose. Fats increase energy density in the diet because of the high calories per unit of weight than carbohydrates and sugars. Excessive use however, can be detrimental to the rumen microbes. Supplementary minerals are usually required to ensure proper amounts of the elements are available to beef cattle. Vitamin D aids in proper development of bone, with a deficiency resulting in bowing of leg bones in calves.
- There is a wide variety of feedstuffs that cattle can utilize due to their complex stomach. There are four groups that most common feeds can be categorized: Roughages, grains, oilseeds, and by-products.
- Roughages include hay, grass, grain hulls, and oilseed hulls. These are high in fiber (cellulose and hemicellulose) and usually low to intermediate in energy.
- Grains include corn, barley, and oats. They are a good source of energy and relatively low in fiber.
- Oilseeds include soybeans and canola meal. Nutrients seen with oilseeds are high in protein and usually high in energy.
- By products include distiller grains, sweet corn cannery waste, bakery waste, grain screenings, and apple pomace. There is variable nutrient content, but many may contain a high level of moisture.
Reproduction
Anatomy of the cow and bull is represented on the home page.
- Cows have many cycles in their lifetime. One such cycle is that of estrus or "heat." A cow in heat is ready to be bred. The average duration of estrus in cows is 12 hours, but can range from 6-27 hours. About thirty hours after the onset of estrus, a cow will be ovulating. The next cycle is estrous which can range for 19-23 days long in a cow. Gestation period in the cow is from 283 days to 297 days. During all these cycles, a number of hormones are increasing or decreasing within the cow, to tell her body what needs to happen.
- Important notes on the bull reproduction is that they have an extra step in their anatomy called the ampulla. The ampulla is an enlargement in the vas deferens which acts as a holding area for sperm cells that are ready to be ejaculated. The bull can ejaculate a volume of 3-8 ml. The factors that affect the fertility of that ejaculate include structural soundness of bull, capability of reproductive organs, quality of semen, level of libido (sex drive), and nutrition.
- In order for a cow to produce a calf every year, she must breed within 80 days after calving. In a pasture bull, it can be expected that a yearling can impregnate 15-20 cows in a 60 day breeding season. A 2 year old bull in the same conditions can impregnate 20-30 cows. 3+ year old bull can be expected to impregnate 30-40 cows in these conditions.
![Presentation of Calf at Birth Picture](/uploads/5/6/7/3/56734417/9383687.jpg?308)
- The first stage of parturition in a cow can take anywhere from 2-6 hours. The second stage is shorter, usually 30 mins to 2 hours. This depends on a number of factors, including first time heifer versus older cow, presentation of calf in body, size of calf, etc. It is estimated that ~5% of cattle births have some type of abnormal presentation (Figure3). Stage three can take anywhere from 30 mins to 3-5 hours.
References
- "Beef Bull Fertility." Ontario Ministry of Agriculture, Food, and Rural Affairs. OMAFRA, Jan. 2006. Web. 10 July 2015. <http://www.omafra.gov.on.ca/english/livestock/beef/facts/06-015.htm>.
- "Basic Beef Cattle Nutrition." Ontario Ministry of Agriculture, Food, and Rural Affairs. N.p., Sept. 1991. Web. 10 July 2015. <http://www.omafra.gov.on.ca/english/livestock/beef/facts/91-066.htm>.
- "Drovers Cattle Network." The 3 Stages of Parturition. N.p., Jan. 2015. Web. 31 July 2015. <http://www.cattlenetwork.com/advice-and-tips/cowcalf-producer/3-stages-parturition>.
- "Rearing Calves." Veanavite. N.p., n.d. Web. 15 July 2015. <http%3A%2F%2Fveanavite.com.au%2FRearingGuide%2FCalves.aspx>.
- "Added Fat in the Ration of Beef Cows to Enhance Reproduction." Penn State Extension. Penn State College of Agricultural Sciences, n.d. Web. 15 July 2015. <http://extension.psu.edu/animals/beef/reproduction/articles/added-fat-in-the-ration-of-beef-cows-to-enhance-reproduction>.