At an intermediate stage of measuring the endomysium connective tissue framework of meat with an image analysis system.


Measuring the growth of meat animals is a lot more difficult than measuring the growth of people. You can tell a people to stand still on the weigh- scale, you can ask them not to come to the measuring session plastered with several kilograms of mud, you can see their degree of subcutaneous fat cover and muscle bulging, and people normally do not fill their stomachs with fodder or their bedding material at every opportunity. Thus, it is difficult to assess the growth of meat animals. Of critical importance for the butcher, the live weight of an animal tells us little or nothing about the amount of fat it has, and a fair amount of groping is required to make even a rough estimate of the contribution of body fat to live weight.



Medical methods for the non-destructive analysis of body composition, such as computer-assisted tomography (CAT) and nuclear magnetic resonance (NMR) imaging, can be used to measure the growth of meat animals, but their extremely high cost and complexity restrict these methods to research. They would be extremely difficult to apply routinely in commercial agriculture and could not be cost effective.


Ultrasonic imaging is widely used for humans, and it is far, far less expensive than CAT or NMR. Ultrasonic measurements of fat and muscle thickness generally are quite reliable and are used routinely in comemrcial agriculture.


The relative development of commercially valuable carcass components such as the loin and hindquarter is difficult to assess subjectively in the live animal, but may be done by photogrammetry. This utilises the parallax effect of a stereo photograph compounded from two photographs taken simultaneously by two cameras separated by a known distance. The volume of the animal body or anatomically defined parts of the body may be calculated from the degree of the stereo effect. Although this method may be accurate, its cost and complexity have so far limited its use.

Specific gravity

The relative development of the carcass also may be studied using specific gravity. Instead of being immersed in water by the classical method of Archimedes, the air displacement technique uses negative air pressures around an animal in an experimental chamber. The accumulation of fat (low density) decreases the overall density of the body so that density then provides an index of fatness. In practice, however, it is difficult to obtain accurate volumetric measurements that allow for the offsetting effects of bones. In cattle, bone density increases with age and varies between sexes and breeds.

Water content

An alternative method for adipose tissue volume is based on the fact that adipose tissue has a very low water content. Chemicals such as antipyrin or one of its derivates are injected into the vascular system from whence they diffuse into the total volume of aqueous body fluids. Provided that the injected substance is only slowly metabolized or excreted by the body, and provided that it becomes adequately dispersed, the extent to which the injected substance becomes diluted indicates the total diluting volume. In general, fat animals have a proportionately smaller aqueous volume than lean animals.

Isotope methods

Another indirect method of estimating body composition is based on the fact that nearly all the potassium in the body is intracellular. Since adipose cells contain only a trace of potassium in their scanty amount of cytoplasm, the total amount of potassium in the body is approximately proportional to the lean body mass.

Radioactivity also may be employed in a similar manner using isotopes of hydrogen (deuterium or tritium) to estimate the water volume and, indirectly, the fat content of a live animal. The advantage of deuterium is that it is not radioactive, while the advantage of tritium is that it may be measured rapidly by liquid scintillation.

Electromagnetic methods

The volume of electrolytes in the animal body is estimated from the disturbance that their electrical conductivity creates in an externally-applied electromagnetic field. However, this system is adversely affected by any variation of the animal's position and orientation within the electromagnetic field and, consequently, it is not accurate enough for live animals. However, it works very well for boxed beef and carcasses that can be neatly lined up on a conveyer to pass through the machine - but that's another story.

Serial slaughter experiments

After an animal has been slaughtered its composition may be determined very accurately. Thus, a group of animals can be slaughtered one at a time throughout their growth to assemble a pseudo-growth curve. The major problem is the degree of variation between individual animals, the high cost involved, and the fact that all the animals are dead when the experiment is finished. The method can be used with the off-spring of expensive breeding stock (progeny testing), but all this takes a long time and is one step removed from the animal of interest - usually a prize bull or boar.