The metabolic cages are used to study the metabolism of feeds in the animal. Metabolic trials are conducted to collect the feces, urine and feeds residue using precisely for analysis nutrients intake, digestibility, nitrogen and mineral balance. It is generally conducted in confined shed/shelter with underground place for urine collection. It is observed that due to movement of animal urine collection pipes comes out of the drum resulting in loss of urine. In this method collection of feed residue also creates problem due to mixing of feeds with mangers. To solve this problem, cages may be constructed for large ruminants where collection and recoding of the required material is easy.
The cages designed to host animals of different sizes and be totally efficient in sampling urine and faeces, and also in providing water and food. Animals should be able to stand up, lie down comfortably and stretch within the metabolism cages/crates. It is often necessary to make complete and separate collections of urine and feces for several consecutive days in physiological and nutritional studies with cattle. Metabolism stalls to achieve this end have been described (Briggs and Gallup, 1949; Erwin et al., 1956; Nelson et al., 1954). The unique features of the stall to be described are (1) safe access to head and neck of animal (2) convenience in milking cows and (3) the unit can be dismantled. It also combines desirable features of previously described stalls such as construction materials which provide long life, ease of cleaning or decontaminating, convenience of watering cup and movability.
It can be easily dismantled for storage or moving through doorways. The frame is constructed of iron pipe and angle iron. The floor is made of iron plate covered with a rubber mat, and mat can be easily replaced if contaminated. The lower arms are slightly longer so that when the panel is extended the stall is narrower on the bottom. This reduces the tendency for the animal to fall to its knees when the stall is being used for maximum restraint. To facilitate work with lactating animals, the stationary side is constructed to provide unobstructed access to the udder. The manger is constructed of angle iron. It is mounted on front and can be locked to the stall by two U-shaped hooks or completely removed for free access to the head and neck of the animal. A plastic shroud around the back has been added to confine possible splattering of feces.
A. Objective of conducting metabolic trials
- The confinement of animal to enable the total collection of faeces for estimating the digestibility of a feedstuff for ruminants.
- The confinement of animal to enable the total collection of faeces and urine for determining the nutrient (N, minerals) balance of a feedstuff fed to ruminants.
B. Criteria for the metabolic cages:
- Metabolism cages may vary in their size and design depending on the type of animal, purpose, duration of experiment.
- All animals should able to stand up, lie down comfortably and stretch within the metabolism cages/crates.
- Animals may required to be tethered in cages for the length of the collection process (generally 10 days) to allow complete collection and maintain separation of the faeces and urine.
- Tethering may also be required to prevent the animals turning around during the collection process
- Any stresses caused by uncomfortable stalls and rough handling can bias experimental results therefore, it is necessary to give careful consideration to facilities used in metabolism studies.
C. Length of confinement
- Animals typically have an introductory phase for adjustment to the metabolism cage/crate, which may include several days for the animal to become accustomed to being tethered.
- The collection period requires a minimum of 7 days faecal and urine collection, however, this may need to be varied for specific purposes but should not exceed 14 days for cattle over 400 kg.
- Feed intake is generally determined 24 hours prior to the collection period given the lag between feed eaten, urine and faeces excreted.
- Animals are not exercised during this period, since faeces and urine would be lost upon removal of the animal from the crates, negating the purpose of the experiment.
Feed, water and environment:
- Diets should be formulated in a such a manner that the animal should not suffer from the laminitis, rumenitis, acidosis and other gastrointestinal upsets; however, the primary purpose of metabolic studies is feed evaluation.
- Animals should not be without feed for longer than 24 hours, unless otherwise justified to meet the experimental design protocol, ethical and welfare issue.
- Clean, fresh water should be available to the animal at all times. Food and water troughs in cages should be located to reduce their contamination by faeces and/or urine.
- Cages should be designed to be well-drained and minimise the risk of injury or disease to the animal.
- Flooring should permit excreta to pass through readily without imposing risks of hoof or leg injury.
- The building housing metabolism crates and cages should provide adequate ventilation for respiration, removal of excess heat and waste gases and have appropriate lighting.
- The building should be well insulated and properly sited to reduce high summer temperatures on animals and maintain adequate temperatures during winter.
- Faeces and urine should not be allowed to accumulate and present a health risk to the animals. Cages/crates should be cleaned each day.
Dimensions of metabolic cage for the cattle:
1. Floor space : Length = 258 cm
Width = 163 cm
2. Dimensions of the cage:
(a) Gate dimensions: Two parts of gate
One part gate dimensions:
Total height= 63 cm; out of that free height is 30 cm and iron plate height is 33 cm.
(b) Height of the cage from ground to upper end= 200 cm
(c) Height from ground to cage floor =30 cm
(d) Side width of cage= 263 cm.
Fig: 1. Back view of metabolic cage for cattle
3. Feeding trough :
(a) External dimension:
Front Height = 63 cm
Width trough = 100 cm.
(b) Internal dimension:
Height= 62 cm
Fig: 2. Detachable feeding troughs
Care of animals during/after the procedure
Careful observation by an expert to ensure the animals’ well-being is necessary. Any animals that refuse to eat or become ill, indicated by high rectal temperatures (> 39° C) or by ‘hot’ or inflamed shins, or by persistent lying, should be shifted to pasture and be treated appropriately to ensure recovery.
Metabolic cages to assist in the total collection of feed residue, urine and feces from large ruminants during metabolism trials are detail. This metabolic cages have the following features: (1) movability, (2) ease of cleaning, (3) easily dismantled for storage or moving, (4) removable manger (on wheels) to allow free access to head and neck. The features provide greater comfort and ease of handling of an experimental animal with more convenience and safety for the experimenter than any stall. The stall described here has been used with animals weighing from 290 to 600 kilograms. Animals are able to lie down and get up easily and yet could be sufficiently restrained for easy handling. A 2- to 3-week period in which the animals were gradually introduced to the stall was necessary before they were at ease. It is important to adjust the length of stall properly for collection of feces and urine.
Briggs, H. M. and W. D. Gallup. 1949. Metabolism stalls for wethers and steers. J. Anim. Sci. 8:479.
Erwin, E. S., I. A. Dyer, M. E. Ensminger and Wayne Moore. 1956. A portable metabolism stall for steers. J. Anim. Sci. 15:435.
Nelson, A. B., A. D. Tillman, W. D. Gallup and Robert MacVicar. 1954. A modified metabolism stall for steers. J. Anim. Sci. 13:504.
Rumsey, T. S. 1969. Collection system for cattle and its effect on EKG and respiratory patterns. J. Anim. Sci. 28:38.