#### § 3.28 Primary enclosures.

All primary enclosures for guinea pigs and hamsters shall conform to the following requirements:

(a) *General.*

(1) Primary enclosures shall be structurally sound and maintained in good repair to protect the guinea pigs and hamsters from injury. Such enclosures, including their racks, shelving and other accessories, shall be constructed of smooth material substantially impervious to liquids and moisture.

(2) Primary enclosures shall be constructed and maintained so that the guinea pigs or hamsters contained therein have convenient access to clean food and water as required in this subpart.

(3) Primary enclosures having a solid floor shall be provided with clean bedding material.

(4) Primary enclosures equipped with mesh or wire floors shall be so constructed as to allow feces to pass through the spaces of the mesh or wire: *Provided, however,* That such floors shall be constructed so as to protect the animals' feet and legs from injury.

(b) *Space requirements for primary enclosures acquired before August 15, 1990* —

(1) *Guinea pigs and hamsters.* Primary enclosures shall be constructed and maintained so as to provide sufficient space for each animal contained therein to make normal postural adjustments with adequate freedom of movement.

(2) *Guinea pigs.* In addition to the provisions of [paragraph (b)(1)](/on/2024-07-03/title-9/section-3.28#p-3.28(b)(1)) of this section, the following space requirements are applicable to primary enclosures for guinea pigs:

(i) The interior height of any primary enclosure used to confine guinea pigs shall be at least 61⁄2 inches.

(ii) Each guinea pig housed in a primary enclosure shall be provided a minimum amount of floor space in accordance with the following table:

| Weight or stage of maturity | Minimum space per guinea pig (square inches) |
| --- | --- |
| Weaning to 350 grams | 60 |
| 350 grams or more | 90 |
| Breeders | 180 |

(3) *Hamsters.* In addition to the provisions of [paragraph (b)(1)](/on/2024-07-03/title-9/section-3.28#p-3.28(b)(1)) of this section, the following space requirements are applicable to primary enclosures for hamsters:

(i) The interior height of any primary enclosure used to confine hamsters shall be at least 51⁄2 inches, except that in the case of dwarf hamsters, such interior height shall be at least 5 inches.

(ii) A nursing female hamster, together with her litter, shall be housed in a primary enclosure which contains no other hamsters and which provides at least 121 square inches of floor space: *Provided, however,* That in the case of dwarf hamsters such floor space shall be at least 25 square inches.

(iii) The minimum amount of floor space per individual hamster and the maximum number of hamsters allowed in a single primary enclosure, except as provided for nursing females in [paragraph (b)(3)(ii)](/on/2024-07-03/title-9/section-3.28#p-3.28(b)(3)(ii)) of this section, shall be in accordance with the following table:

| Age | Minimum space per hamster (square inches) | | Maximum population per enclosure |
| --- | --- | --- | --- |
| *Dwarf* | *Other* |
| Weaning to 5 wks | 5.0 | 10.0 | 20 |
| 5 to 10 wks | 7.5 | 12.5 | 16 |
| 10 wks. or more | 9 | 15.0 | 13 |

(c) *Space requirements for primary enclosures acquired on or after August 15, 1990* —

(1) *Guinea pigs.*

(i) Primary enclosures shall be constructed and maintained so as to provide sufficient space for each guinea pig contained therein to make normal postural adjustments with adequate freedom of movement.

(ii) The interior height of any primary enclosure used to confine guinea pigs shall be at least 7 inches (17.78 cm).

(iii) Each guinea pig shall be provided a minimum amount of floor space in any primary enclosure as follows:

| Weight or stage of maturity | Minimum floor space | |
| --- | --- | --- |
| in2 | cm2 |
| Weaning to 350 grams | 60 | 387.12 |
| >350 grams | 101 | 651.65 |
| Nursing females with their litters | 101 | 651.65 |

(2) *Hamsters.*

(i) Primary enclosures shall be constructed and maintained so as to provide sufficient space for each hamster contained therein to make normal postural adjustments with adequate freedom of movement.

(ii) The interior height of any primary enclosure used to confine hamsters shall be at least 6 inches (15.24 cm).

(iii) Except as provided in [paragraph (c)(2)(iv)](/on/2024-07-03/title-9/section-3.28#p-3.28(c)(2)(iv)) of this section, each hamster shall be provided a minimum amount of floor space in any primary enclosure as follows:

| Weight | | Minimum floor space per hamster | |
| --- | --- | --- | --- |
| g | ozs | in2 | cm2 |
| <60 | <2.1 | 10 | 64.52 |
| 60 to 80 | 2.1-2.8 | 13 | 83.88 |
| 80 to 100 | 2.8-3.5 | 16 | 103.23 |
| >100 | >3.5 | 19 | 122.59 |

(iv) A nursing female hamster, together with her litter, shall be housed in a primary enclosure that contains no other hamsters and that provides at least 121 square inches of floor space: *Provided, however,* That in the case of nursing female dwarf hamsters such floor space shall be at least 25 square inches.

(3) Innovative primary enclosures that do not precisely meet the space requirements of [paragraph (c)(1)](/on/2024-07-03/title-9/section-3.28#p-3.28(c)(1)) or [(c)(2)](/on/2024-07-03/title-9/section-3.28#p-3.28(c)(2)) of this section, but that do provide guinea pigs or hamsters with a sufficient volume of space and the opportunity to express species-typical behavior, may be used at research facilities when approved by the Institutional Animal Care and Use Committee, and by dealers and exhibitors when approved by the Administrator.

[[32 FR 3273](https://www.federalregister.gov/citation/32-FR-3273), Feb. 24, 1967, as amended at [55 FR 28882](https://www.federalregister.gov/citation/55-FR-28882), July 16, 1990]