Friday, 21 February 2014

Beef production: Rearing systems and feeding

Beef is produced from dairy breeds and beef breeds, which can reside either in farms focused on dairy, beef or both.There are several options, which are all discussed in further detail.

Dairy breeds

Ayrshire calf
On a dairy farm the focus is on milk production. In the first option the farmer keeps only the dairy cows, heifers and calves which they will use for milk production. Less promising heifers and cows may be inseminated using beef breed semen to improve the carcass weight of their calves. Bull calves and other unwanted calves are sold to a calf rearing farm at the age of 1-8 weeks. Unwanted heifers and old or poorly producing cows are slaughtered.

On another rearing system calves are sold to the beef producer at a later stage, at the age of 2-3 months.

Some farms produce both milk and beef.  In this case all calves are reared on the farm until slaughter.  The farmer may buy more beef calves from surrounding farms. Dairy breed calves are kept for milk production, while beef breeds and less promising dairy breed animals are used in beef production.

Calves are most often reared using a three-phased method. The first phase is when the calf is born, and spends its first 10-26 days on the farm it was born in. Then it is sold to a rearing farm. The calves stay on the 2nd phase until their teens. The rearing time depends on the growth of the animals: in Northern Europe, the 2nd phase lasts 4-6 months. The farmer aims at daily growth of 900g and a mortality less than 4 %. The third phase is the finishing phase. Here the calf is reared until it's ready for slaughter. Finishing phase lasts 12-16 moths, and aims at animals weighing 350 kg. The animals are kept in groups in 15-30. When possible, each group is send to slaughter at the same time, and groups are kept steady to prevent fights.

Beef breeds
Ayrshire x Simmental -calf
Beef breeds are reared on a beef farms, which tend to be more extensive than dairy farms. Dairy animals are kept mainly indoors and fed heavily to promote milk production, while beef cattle is kept outside in paddocks. Feedlots especially in the Northern America are a concerning example of a production system, which is both extensive and intensive.

There are three types of beef production farms. Calf producers focus on keeping dams, who produce up to 10 calves during their lifetime. The calves are sold to a rearing farm, which is the second type of beef production. The third type is a combination farm, where the calves are bred and reared until slaughter.

Usually all breeding cattles, where the main target is to improve the genetics of the animals, are combination farms. In another option the calves are weaned and sold to a finishing phase farm. Here the animals are reared for 8-16 months, when they are sent to slaughter. The targeted live weight of animals depends on the breed, but ranges between 340-440 kg. The finishing phase farms usually accept only animals which are at least 75% beef breed.


In beef production calves may be kept under their dams for 4-6 months, in which case weaning is a slow and natural process. If the calf is weaned from its mother sooner, usually during the first few days, one has to consider best methods for feeding the calf.

There are several options for feeding calves after the first few days of their lives, when they must be fed with colostrum.  Full milk is the most natural option, where calves get the milk which cannot be sent to the dairy. Liquid feeds are another option. the digestive tract of calves under 2-4 weeks of age does not secrete amylase, pepsin or rennin enough to be able to utilize vegetable fats or vegetable proteins. They can only utilize milk protein (casein), lactose and fats. After 4 weeks the calf
Their feed must have casein or whey protein and animal based fats. Water, hay and concentrated feed should be freely available at all times to support to development of the digestive tract.

Calves can be fully weaned from milk once they ingest at least 1 kg of silage a day. This happens usually at the age of 8 months, when the size of the rumen has changed from 30 % to 70 %, and in proportion the omasum and abomasum have shrunk from 70% to 30 %.

Distribution of energy from feed.
Growing cattle need energy, proteins, fat and water to maintenance and to production (see the picture on the left). The energy need for maintenance is measured as a BMR, basal metabolic rate. It includes the energy need for
  • breathing
  • blood circulation
  • molecular synthesis to balance natural catabolism of tissues
  • moving and using substrates in cells
  • contraction of muscle cells, transfer of nerve impulses
  • maintaining body temperature
Factors affecting the energy need for BMR are age, gender, breed, earlier energy status (prolonged malnutrition decreases BMR) and physiological status (is the animal for example in gestation or suckling its offspring). BMR is measured either direcly with a calorimeter or indirectly in a respiration chamber by calculating how much oxygen the animal uses, and much nitrogen and carbon dioxide it produces. The amounts of gases (liters / day) are then inserted to the Brouwer equation:
16,18 * O2 +5,16 * CO2 - 2,42 * CH4 - 5,90 * N in urine (g/day)

For growth, beef breed bulls need on average 10-27 MJ energy / day. A small bull growing 1 kg a day needs 10-15 MJ, while a bull putting on 1,5 kg a day needs 18-27 MJ a day and over 200 grams of protein a day. Castrated bulls (oxes) and heifers utilize energy less efficiently than bulls, and tend to grow slower and have a larger fat percentage than intact bulls.


Cattle get protein from two sources: from feed protein which has passed the rumen, and from rumen microbes. Both types of protein are metabolized in and absorbed from the small intestine. Therefore the animal's need for protein can be expressed as a need for protein absorbed from the small intestine. Another measurement is the protein balance of the rumen, which measures the amount of protein in the feed compared to the microbe's ability to utilize it. If the balance is negative, the microbes do not get enough protein from the feed. In a positive balance the microbes can utilize only a portion of the proteins, and often proteins pass through to the faeces. The balance is not calculated for animals weighing over 200 kg, for their rumen microbes are developed well-enough to withstand even a slightly negative balance.

The metabolization and utilization of protein is described in the picture below. Protein is originally acquired from feed. Undegraded protein, or unmetabolizable protein, is passes through the rumen to the small intestine, where a portion of it is metabolized and absorbed. The rest is exreted as faeces. Metabolizable protein is used by the rumen microbes, which in turn die and are passed to the small intestine. Major part of the amino acids in the microbes are metabolized, absorbed and used as tissue protein (or milk, if the animal is lactating).

The metabolization of protein in the digestive tract of a cattle. Original source unknown.

Sources for information on feeding: 

ARC1980. Agricultural Research Council. 1980. The nutrient requirements of ruminant livestock, technical review.

AFRC1990. Agricultural and Food Research Council. 1990. AFRC Technical Committee on Responses to Nutrients , Report Number 5, Nutritive Requirements of Ruminant Animal : Energy. Nutr . Abstr . Rev.(Series B): 60: 729 - 804

Dryden , G. McL . 2008. Animal Nutrition Science.

Sunday, 16 February 2014

Beef production: Breeds and beef quality

Beef cattle are generally sturdier, meatier and larger than dairy breeds. In addition, they may have stronger maternal instincts, because in several systems the dam suckles her calves for several months. In dairy farming, calves are usually taken from the dam within 24 hours from birth. The information here is referenced from the website of Oklahoma State University and from other sources.

Angus or Aberdeen Angus is a medium-sized beef breed with either black or red coloring. Grows slower and gains fat faster than larger breeds.
Size (cows): 650-850 kg
Size (bulls): 1000-1300 kg

Belgian Blue has a mutation, which causes it to be double-muscled. The extreme size of its muscles causes severe problems when calving, and most cows must undergo several cesarean sections during their lives.
Size (cows): 700-850 kg (source)
Size (bulls): 1100-1250 kg

Blonde d'Aquitane, or blond, is a muscular and docile breed.
Size (cows): 700-900 kg
Size (bulls): 1200-1400 kg

Charolais is a white or cream-colored, large beef breed from France. It grows fast and generally gains fat slower than smaller breeds.
Size (cows): 700-950 kg
Size (bulls): 1200-1400 kg


Herefords are massive, red and white colored animals. The head is usually entirely white and covered in curly, thick fur. Grows slower and gains fat faster than larger breeds.
Size (cows): 600-850 kg
Size (bulls): 1100-1300 kg

 Simmental is colored much like the Hereford, but the head is usually not entirely white. It is originally from the Simme Valley in Switzerland. It grows fast and generally gains fat slower than smaller breeds.
Size (cows): 700-950 kg
Size (bulls): 1200-1400 kg

Limousin  is another French beef cattle breed, and has originally been used as a working animal as well as for beef production. It has a high carcass percentage, i.e. the ratio between carcass weight and live weight. It grows fast and generally gains fat slower than smaller breeds.
Size (cows): 650-850 kg
Size (bulls): 1100-1300 kg

Carcass quality

Beef quality starts from carcass quality. A carcass is more valuable the less fat and bone is has, as the meat is the only economically important portion. The measurements are subjective, and based on the shape of the carcass. Most valuable cuts are evaluated especially carefully. In the European Union carcass quality is measured in an europ-scale: S > E > U > R > O > P (EEC  1208/81):

  • S (superior) = All profiles extremely convex; exceptional muscle development (double-muscled carcase type)
  • E (excellent) = All profiles convex to super-convex; exceptional muscle development
  • U (Very good) = Profiles on the whole convex; very good muscle development
  • R (Good) = Profiles on the whole straight; good muscle develop- ment
  • O (Fair) = Profiles straight to concave; average muscle develop- ment
  • P (Poor) = All profiles concave to very concave; poor muscle development
In addition to the EUROP-scale, the fatness of the carcass is evaluated from scale 1 (fat-free) to 5 (extremely fatty).

Two important concepts to consider are live weight and carcass weight. Live weight is the weight of the entire animal. Carcasss weight is live weight minus the weight of the head, genitalia, udder, digestive tract, internal organs, hide and hooves. The ratio between carcass weight and live weight is called carcass percentage. Carcass percentage varies between breeds, but is commonly 50-60 %.

When the carcass weight increases, to which the farmers often aim at, the relative proportion of lean meat decreases. In proportion, the amount of fat increases. The portion of the most valuable cuts (steak and filet) from the entire carcass does not change. Carcass weight can be increased by using plenty of concentrated feed, but a more effective method is to limit fattening by limiting energy intake at the finishing phase of the rearing.

Beef quality

Muscle becomes meat or beef after the animal has been slaughtered. Slaughtering causes chemical, physiological and biological changes in the muscle tissue. To prevent harmful changes, the animal and the meat must be handled correctly.

Beef quality consists of several factors:
  • Physiochemical properties: pH, color, sarcomere length, run-off, consistency
  • Chemical properties: Dry matter content, amount of protein, amount of fat
  • Sensory properties: juiciness, flavor, tenderness
Meat becomes stringy and chewy when the myocine and actin filaments of the muscle stick together after death (rigor mortis). Usually carcases are cooled under +7 C before rigor mortis sets in, which causes the muscle to constrict due to cold. To prevent cold constriction the meat may be stimulated with electricity. Once the meat is cooked, the proteins break and the meat becomes tender.

Juiciness means the amount of muscle fluid which is released when the cooked meat is bitten into. It
is related to the amount of fat in the meat, since fat increases the water retention capacity. The largest part, 64-80 %, of beef is water. The water is retained between actin and myocin filaments. Water retention capacity decreases as the pH decreases after slaughtering. The pH of muscle is 7,2, but it drops to 5,6 within 24 hours after death. Fat percentage varies between 2-25 %. 

If the animal has little glycogen in its body right prior to slaughter, the meat does not develop enough lactic acid after slaughtering and the pH does not drop as fast and low as it should. This results in a tar meat, or DFD meat (dark, firm, dry). DFD meat is not used for whole-meat products because it has poor shelf life. 

Friday, 14 February 2014

Beef production: Basics

 Beef production is the production of beef and veal, i.e. the meat from cows, steers, bulls, heifers and calves. First we look at the differences between beef production to the production of other types of meat. Then we discuss the anatomy of meat, the growth of the beef animals and their carcass composition. The different methods of rearing beef cattle are discussed in later posts.

What is beef? Beef is the meat from bovines, that is "cows" of different age, gender and breed. The beef you see in a market comes either from beef production, milk production or from a combined farm with both milk and beef production. In Northern Europe, for instance, nearly 90 % of all beed originates from the dairy industry.

Compared with other animals reared for their meat, cows are relatively inefficient at transforming vegetation into meat protein. Dairy cows produce much protein and energy to their milk, but as meat producers they are even less efficient than beef cows.The chart on the left shows only the energy and protein in edible cuts. Energy in tallow, lard etc is not included.

One can also compare the animal species in terms of how well they utilize nitrogen. Feed N recovery efficiency in the edible weight fraction is defined as the percentage of the N in the animal feed that ends up in the edible portion of the animal. N recovery efficiency is low in beef production, only 8 %, but much higher for pork (~20%) and poultry (~30%). (Oenema et al. 2005)

Growth models and carcass composition

Growth can mean either the actual daily growth of an animal, the extra growth it puts on due to management and feeding, or the increase in edible cuts. For example: A calf grows 1500 grams a day (actual growth). Of  that, 400 grams is due to heavy feeding (extra growth). After the calf is slaughtered one can then calculate backwards how much of the 1500g went to the edible meat (increase in edible cuts).

Growth consists of four types of changes:
  1. Changes in size (live weight)
  2. Changes in appearance (height, diameter of chest...)
  3. Changes in anatomical composition (fat percentage, ...)
  4. Changes in chemical composition (chemical composition of muscles, fat etc)
Change in size, for example the weight, is an inaccurate measurement because it is affected by what the animal has eaten and drank. The weight of the digestive tract of a bovine varies tens of kilos during the day. The weight of a cow inceases most rapidly from birth until 6 months of age, when the growth slows and finally comes to an end at the age of 2-3 years. The model is very simplified, because bones, muscles, connective tissue and nerves have a very different rate of growth. This also affects the third measurement: the anatomical composition. First the animal gains mostly bones and nerves, then muscles and finally fat, all altering the anatomical composition of the carcass.

Daily growth is measured either as the proportion of daily growth to the live weight, i.e. 1500g / 250kg = 0,006 %, or simply as g/day. Final weight of beef breeds varies from 350 kg (a Dexter cow) to 1400 kg (Charolais bull). Bulls grow 10-20 % faster than steers (castrated bulls), while steers grow as fast as heifers (Galbraith and Topps 1982).

Changes in appeareance only describe how the different parts of the animal grow in proportion to one another. For example a calf has tall feet and a shallow chest, while a grown cow has shorter feet and very wide chest.

Chemical changes describe the changes in the composition of the body. The higher the live weight, the more fat there is in a kilo of carcass, and therefore also the relative energy content increases. At the same time the relative portion of crude protein decreases. As with all young animals, first to grow are the bones and nerve tissue, with muscles next and finally body fat. Breed and gender also affect the carcass composition. Steers gain 10-45 % more fat than bulls, and breeds like Angus and Hereford are fatter than for example Limousin and Charolais. Note that breed does NOT affect the composition of the lean (fatless) carcass.

All in all, the growth of an animal is summarized in the picture below (Rumsey 1991).

The anatomy of muscles

30-40 % of the live weight of a bovine consist of skeletal muscles. The quality of edible meat is affected by the chemical, biochemical and physiological qualities of the muscle both before and after slaughter. Growth, feeding, animal handling and meat processing after slaughter also all have an impact on the quality of the meat.For bovines, 30 largest muscles contribute 75 % of the weight of all the muscles. The largest muscle groups are in the pelvic limb (hind quarters) with 28,5 % of live weight, and neck/thorax with 22,4 %.

The anatomy of a skeletal muscle is shown in the picture to the left.The muscle is covered by epimysium, and consists of bundles of muscle fibres. The space between bundles is filled with perimysium, which has lots of nerves and blood vessels. Perimysium affects the tenderness of the meat. There is also fat between the muscle fibres, and this fat gives the meat it's marbling properties. Each muscle fibre is surrounded by endomysium, yet another type of membrane.

Each muscle fibre in the skeletal muscles has several nuclei. Fibres are surrounded by a sarcoplasm, which is a membrane, and sarcolemma, which is a type of elastic connective tissue. One fibre consists of 1000-2000 myofibrils. The functional unit of a myofibril is called a sarcomere. Sarcomere is where the muscle actually works, when thick and thin filaments of the sarcomere either slide closer or farther from a z disk (see the picture below). If the filaments become imbricated, the muscle constricts. When they slide farther apart, the muscle relaxes (returns to rest stage) or stretches. A very detailed video about the action potential and muscle activity can be found from Youtube.

Marbling and tenderness

Marbling of the meat means the increase of intramuscular fatty tissue, which occurs at the finishing phase of beef cattle rearing. Marbling is more pronounced with strong, grain-based feeding. The actual level of marbling is determined visually after slaughtering by estimating the percentage of fat in a cut of meat. Fat is seen as white areas in otherwise red meat.

The fat in the muscle is mostly based from de novo -fatty acid synthesis, which takes place in the rumen. The rumen biohydrogenates unsaturated fatty acids into saturated ones, so the fat of ruminating animals is more saturated than that of monogastric animals. For example, cattle have more saturated triglyceride 18:0 and less unsaturated 18:2 than pigs (Lawrence & Fowler: Growth of Farm Animals).

Tenderness is affected by the type of collagen in the perimysium, the connective tissue between bundles of muscle fibres. More important than types or the amount of collagen is cross-linking between the collagen types. Both the cross-linking and insolubility of collagen increase as the animal ages. That is why the meat from old animals is more stringent than the tender meat of young animals. However, when cooking meat in high temperatures even tender meat becomes stringent due to heat-induced chemical changes in the collagen.