There is a growing body of evidence that domesticated animals and in particular laboratory animals exhibit behaviors that in humans are associated with sensory deprivation and depression. These abnormal behaviors not only impact the well-being of an individual animal but also have implications in studies involving such an animal owing to the physiological effects of sensory deprivation and depression. In humans, sensory deprivation and depression have an effect on metabolism, cognitive function, immune response and other parameters relevant to clinical studies. The ability to provide a laboratory animal with a degree of mental stimulation is hampered by the requirements of study protocols that attempt to avoid introduction of new reaction variables, as well as the requirement in many instances that only sterilized materials be brought into contact with a laboratory animal. Captive animals deserve an environment which is rich in social opportunity, mental stimulation, and physical challenges. Sterility conditions are typically enforced in instances where an animal has been immunocompromised or otherwise carries a genetic defect rendering an animal vulnerable to disease or infection.
With laboratory study requirements, litter provided to absorb animal urine and desiccate fecal material is one of a limited number of opportunities to provide a source of stimulation to a confined laboratory animal. Prior art attempts have been made to include folded squares of paper with the intention that the animal would occupy time delaminating and chewing or unfolding the small chips of paper. Unfortunately, such attempts met with limited success owing to the disinterest of mice (especially male species) and rats confined within laboratory cages to actually play with the folded squares of paper. The 1985 amendments to the Animal Welfare Act included provisions for the promotion of the psychological well-being of nonhuman primates and for exercise for dogs. Today, many research, teaching and testing facilities have established environmental enrichment programs for all animal species. (awic.nal.usda.gov/nal_display/index) are representative of this effort.
Sheehan (U.S. Pat. No. 5,909,718) teaches a method of making particulate absorbent material from waste paper for the use of the material as a base for animal bedding. The waste paper is shredded, mixed with water and a binder, and dried to form solid paper particles having a diameter of from about 0.05 to about 2.0 centimeters. These have met with limited acceptance owing to exposing laboratory animals to unknown substances associated with the waste nature of the paper, as well as the lack of play value afforded to animals.
Tucci (U.S. Pat. No. 4,038,944) provides a synthetic animal bedding in recognition of the fact that natural bedding material must be replaced periodically and is not reusable. Although having tried to solve prior problems associated with the reusability of natural straw bedding, Tucci disfavors straws and further requires that the synthetic plastic pieces be arranged relatively parallel to the ground or bottom surface.
Similarly, Mochizuki (U.S. Pat. No. 6,405,676) teaches a twisted paper cylindrical material as a urine-absorbing litter. However, this material has met with limited acceptance owing to a low density and asymmetric shape that makes scooping and handling difficult. Also, presumably owing to the uniformity of the material as being exclusively twisted paper cylinders, sensory deprived animals are observed to be indifferent to playing with the paper cylinders.
Thus, there exists a need for an animal litter product that engages the attention of a laboratory animal to occupy time and alleviate some of the symptoms associated with sensory deprivation and depression. There further exists a need for such a litter capable of being sterilized and still functioning as an effective animal litter product.