Spot the Difference: Using the domestic cat as a model for the nutritional management of captive cheetahs. Katherine M. Bell

Transcription

1 Spot the Difference: Using the domestic cat as a model for the nutritional management of captive cheetahs Katherine M. Bell Edited by Lucy A. Tucker and David G. Thomas Illustrated by Justine Woosnam and Sarah Hollebon

2 Table of Contents Chapter One: Introduction 1 Chapter Two: Phylogenetics 5 Chapter Three: Ecological comparisons 11 Prey size 12 Prey diversity 16 Feed intake and frequency 18 Chapter Four: Anatomical and physiological comparisons 23 Limbs and claws 25 The hyoid 27 The eyes 27 The skull and brain 27 Dentition 30 Heart and lungs 30 Thermoregulation and muscular adaptations 31 Liver, kidneys and spleen 13 Blood chemistry 32 The digestive system 35 Microflora of the intestinal tract 36 Chapter Five: Reproductive comparisons 41 Anatomy of the reproductive tract 43 Life history characteristics 44 Fertility and fecundity 45 The female reproductive cycle 47 Steroid hormone changes of the oestrous cycle 48 Vaginal cytology 51 Ovulation induction 54 Seasonality 55 Puberty onset and sexual maturity 56 Microflora of the reproductive tract 57 Oestrus behaviour 57 Gestation and pregnancy detection 58 Litter size and survival 59 Birth weight 60 Maternal milk composition 60

3 Interbirth intervals 62 Neonatal growth 63 Chapter Six: Nutrient requirements, utilisation and metabolism 65 Nutrient digestibility 69 Nutrient requirements and deficiencies 73 Energy 74 Protein 75 Amino acids 77 Sulphur amino acids 78 Fats, lipids and fatty acids 79 Carbohydrate 81 Fibre 83 Vitamins 84 Minerals 87 Secondary plant compounds 89 Chapter Seven: Conclusions and practical implications 93 Practical implications 100 Chapter Eight: Bibliography 105 Index 125

4 Phylogenetics 1 1 INTRODUCTION

5 Phylogenetics 3 All living species of felids, except the domestic cat (Felis catus), are listed as endangered or threatened in at least part of their natural range 1. Thus, captive populations of these species play significant roles in their conservation through research, education, breeding and the potential for release of individuals into protected wilderness areas. The health of these captive populations therefore requires careful management. In order to better conserve and manage both the wild and captive felid populations it is necessary to enhance our understanding of their physiology and ecology. Of particular importance for the captive population is an understanding of the nutritional requirements of these species, since adequate nutrition underpins the majority of health parameters. Not only is proper nutrition important for the more obvious reason of preventing starvation (i.e. providing sufficient energy and nutrients to maintain body tissues and normal physiological function), but it also has vital roles to play in disease prevention, immune competency and drug metabolism 2. However, of the 37 extant species of Felidae, the domestic cat is the only one to have been the subject of detailed scientific investigations, and for which we have more than just a basic understanding of its nutritional needs 3. As a result, scientists have relied heavily on the extrapolation of findings in the domestic cat to predict nutritional requirements or reproductive function in endangered felid species 3-5. The cheetah (Acinonyx jubatus) and domestic cat are both members of the family Felidae. In common with the other felid species, they are specialist meateaters and are thought to have diverged early in their evolution from a common mammalian ancestor 6; 7. Fossil records suggest that the dietary modifications of various species of the order Carnivora were established early in their evolution as minimal changes in cranial and dental anatomy have occurred since the late Eocene or early Oligocene periods 8. Hence, the specialist nutritional features of cats may reflect a lack of significant genetic modification from the ancestral carnivores 9. Alternatively, evolutionary pressures may have favoured a physiology that included only those metabolic pathways associated with the consumption of animal tissue 3; 10, whereby the ability to digest plant material was lost. The array of metabolic deficiencies now seen in cats, such as the absence, lowered efficiency or disparate processes employed to handle ingested plant material, may actually be adaptations in themselves 3; 6. Due to these nutritional adaptations and our awareness of the key role that diet plays in disease and reproduction, the nutrition of captive exotic felines is a topic which is receiving increasing attention from the scientific and zoological community. Yet, due mainly to their highly endangered status and the relatively small number of individuals available for research, the digestive and

6 4 Spot the Difference: Are Cheetahs Really Just Big Cats? metabolic physiology of many of the non-domestic felids is largely unknown. In a similar fashion, although the gross reproductive anatomy of felids appears to be generalised across the taxon, the understanding of the reproductive physiology in non-domestic cats is still inferior compared to their household counterparts. The limited data available suggest that non-domestic felids share similar dietary needs with the domestic cat 3; 4; 11. However, despite the widespread use of domestic cat nutrient requirements to formulate diets for captive non-domestic felids, nutritionally-related disorders still occur in captive species such as cheetahs, albeit with a lowered frequency in recent years Likewise, the fertility of the captive cheetah population is still dramatically lower than that of free-ranging populations 15, despite advances in reproductive technology developed with the domestic cat model. This book reviews the known differences and similarities between cheetah and domestic cat biology, with particular reference to characteristics relevant to the nutritional management of captive cheetahs. Where examples from one or both species are missing, comparisons are made with other members of the Felidae in order to estimate the likelihood of interspecific differences between the cheetah and domestic cat. The use of the domestic cat as a model for establishing nutritional requirements in the cheetah is critically evaluated and the practical implications of the findings are provided.

7 Phylogenetics 5 2 PHYLOGENETICS

8 Phylogenetics 7 Cat-like carnivores are thought to have separated from dog-like carnivores approximately 55 million years ago, with modern felids appearing in the late Miocene (about 10.2 million years ago) 16 (Figure 1). However, ancestral cats are thought to have developed dentition suggestive of a truly carnivorous diet more recently, up to 15 million years ago 3 and DNA studies suggest that modern cats evolved from eight phylogenetic lineages, within the past million years 3; 17; 18 (Figure 2). Time (millions of years) Eocene Oligocene Miocene Plio - Pleist Feliformia Carnivora Caniformia Pinnipedia Arctoidea Musteloidea Nimravidae Amphicyonidae Nandiniidae (African palm civet) Felidae (Cats) Viverridae (Civets, genets, linsangs & relatives) Hyaenidae (Aardwolf, hyaenas) Herpestidae (Mongooses) Eupleridae (Malagasy carnivores) Candidae (Dogs) Ursidae (Bears) Otariidae Eared seals (fur seals & sealions) Odobenidae (Walruses) Phocidae (Earless seals) Alluridae (Red pandas) Mephitidae (Skunks, stink badgers) Procyonidae (Coatis, raccoons) Mustelidae (Badgers, otters, weasles & relatives) Figure 1. Evolution of the Carnivores.