Degree Type


Date of Award


Degree Name

Master of Science


Animal Science

First Advisor

Cheryl L. Morris


Currently two protein sources (beef or horse) comprise the majority of raw meat diet formulations for exotic carnivores in zoological institutions. Pork-based diets have traditionally not been fed to managed exotic carnivores, primarily because of microbial and pathogenic concerns, and nutrient digestibility of pork has not been evaluated in captive exotic carnivores, such as felids. Additionally, commercially prepared raw meat diets, while nutritionally complete, rarely meet nonnutritive requirements of cats, such as locating, capturing, and killing prey as well as psychological aspects related to the feeding process, and oral health needs. The pork industry currently sends many by-products to rendering that have the potential to be used in raw carnivore diets or as environmental enrichment.

The overall objectives of this research were to evaluate a raw, pork-based diet for small and large captive exotic felids, including diet compositional analyses, fecal scores, palatability, and microbial loads. Additionally, the use of pork by-products as environmental enrichment devices for large captive exotic felids was evaluated. Our first aim was to determine apparent total tract macronutrient digestibility, fecal scores, and palatability of a pork-based diet compared with standard zoological carnivore diets formulated with either horse or beef, in large captive exotic felids. Our second aim was to determine if a pork-based diet had similar apparent total tract macronutrient digestibility and fecal scores as standard zoological carnivore diets formulated with either horse or beef, in small exotic felids, and evaluate microbial populations in raw diets. Our third aim was to evaluate 11 pork by-products for macronutrient and mineral composition and determine if a pig head would be a biologically relevant environmental enrichment device for large felids kept in a zoological setting.

In general, a raw pork-based diet was well digested and utilized by large and small captive exotic felids. All raw meat diets used in these studies were highly digestible, and the pork-based diet was similarly or more digested compared to other protein sources. Fecal scores were healthy when felids were fed the pork-based diet and the diet was determined palatable for the tested cats. The use of raw pork by-products also provides opportunity as potential environmental enrichment.

In our first aim, we demonstrated that a raw pork-based diet was highly digestible in large exotic felids by using four raw meat dietary treatments: one horse-based (Horse), two beef-based (B1, B2), and one pork-based diet (Pork). Dry matter (DM) and crude protein (CP) apparent digestibilities were higher (P<0.05) in cats fed Pork (87.97 and 95.74%) compared with cats fed Horse (83.59 and 92.71%) and B2 (85.60 and 93.14%). Apparent organic matter (OM) digestibility was higher (P<0.05) in cats fed Pork (90.76%) than cats fed Horse (88.53%). Apparent fat digestibility values were high across all treatments but were higher (P<0.05) in cats fed Pork (98.51%) compared with cats fed B1 (95.51%) or B2 (96.45%). Gross energy (GE) digestibility values were higher in cats fed Pork (92.38%) compared with B1 (90.21%). Using a scale of 1 to 5, with 3 considered ideal, average fecal scores were 2.30, 2.94, 3.42, and 3.54 for Horse, Pork, B1 and B2, respectively; and were different between every treatment with the exception of B1 and B2 which were not statistically different. The pork-based diet was palatable and was selected in 24 of 37 total (64.86%) observations of first approached and 23 out of 33 total (69.70%) observations for first tasted, compared to a raw beef-based diet.

In our second aim, we showed that a raw pork-based diet was highly digestible in small exotic felids by using raw horse (Horse), beef (Beef), beef/horse blend (Blend), and pork-based (Pork) dietary treatments. All diets were highly digestible, especially fat digestibility (98.58 to 99.73%) in which there were no statistical differences between diets. Digestibility of OM was higher (P<0.05) when cats consumed the Blend diet (97.15%) compared to the Pork diet (93.10%). Fecal scores ranged from 1.55 to 2.63, with Beef (2.63) being statistically higher (P<0.05) than Horse (1.55) and Pork (1.91). Additionally, microbial counts were shown to be highly variable in dietary treatments (E. Coli: 110 to 10,000 cfu/g; total coliforms: 150 to 28,000 cfu/g; yeast: 20 to 4,000 cfu/g; mold count: not detectable to 10 cfu/g; aerobic plate count: 23,000 to 26,000,000 cfu/g). Staphylococcus aureus was not detected in any of the diets. Salmonella was presumptive positive in the Pork and Blend diet, and was negative in the other three diets, but no signs of clinical illness were observed in cats fed any of the evaluated diets.

In our third aim, it was demonstrated that pork by-products ranged widely in composition and have potential for use as biologically relevant environmental enrichment for captive exotic felids. Ranges of macronutrient composition for 11 pork by-products were: DM: 26.01-71.23%; OM: 53.04-96.79%; CP: 22.90-79.29%; fat: 22.01-63.15%; CF: 0.25-19.54%; total dietary fiber (TDF): 0.04-3.44%; GE: 3.73-7.45 kcal/g. Potential use of these by-products as environmental enrichment was demonstrated by offering five large exotic felids a pig head, and observing their behavior on Baseline (before head offered), Enrichment (head offered), and Post enrichment (head removed) days, over 4 weeks, using instantaneous scan sampling at one minute intervals for 2 hours in the morning. Active behaviors were observed to be 55.70% higher (P<0.0001) on Enrichment days compared to Baseline and 26.42% higher (P<0.0001) compared to Post enrichment days. Active behaviors were 39.79% higher (P<0.0001) on Post enrichment days compared to Baseline days. Total active behaviors were observed to increase 44.24, 49.42, and 64.27% (P<0.0001) in week 3 compared to weeks 1, 2, and 4, respectively, and increased 35.93 and 29.36% in weeks 1 and 2, respectively, compared to 4. Number of location changes were greater (P<0.05) in week 3 compared to 2 or 4. Fecal scores were not statistically different across days or weeks. Time to approach the head (seconds) and loss in head weight from before to after offering to the cat (grams) were not statistically different (P>0.05) across weeks.

Dietary variety is important for exotic felid health as well as managerial flexibility. Enrichment also has been an area of increasing interest for zoos over the past several decades. This research has demonstrated that a pork-based raw meat diet can be included among dietary options for captive exotic felids and that, while microbial populations in these diets are high, felids can tolerate microbial load present in raw meat diets. Additionally, pork by-products can provide valuable nutrients while fulfilling nonnutritive needs of exotic felids that are not provided by commercially prepared soft, raw meat diets.

Copyright Owner

Cayla Jo Iske



File Format


File Size

165 pages