Rabbit Nutrition, Breeds, and Digestion

Rabbit Nutrition and Digestive System

• Rabbits require specialized feeding and their diet is crucial for their health, digestion, and well-being.
• Rabbits prefer nutrient-rich leaves and young plant shoots over mature, high-fiber material.
• Rabbits naturally select foods higher in energy density, which can cause obesity in captivity if diet is not managed.
• Rabbits are non-ruminant herbivores and are hindgut fermenters due to their enlarged hindgut.
• The cecum in rabbits houses microorganisms that ferment and digest nutrients.
• High-fiber diets are essential for rabbit health, as this process efficiently extracts nutrients from fibrous plant material.

Breeds of Rabbits

• Rabbits are bred to produce meat, skin, and fur.
• Some breeds for meat and skin production are known for fast growth, high meat yield and pelt quality.
• Some breeds for fur production are valued for their high-quality fur and used in textiles and fashion.

Digestive System of Rabbits

• Rabbits efficiently process high-fiber plant material through hindgut fermentation.

Parts of the Digestive System

• Lips gather food and pass it to the teeth for grinding.
• Teeth grow continuously to compensate for wear.
• Saliva moistens food for easier movement.

Esophagus

• Transfers food from the mouth to the stomach.

Stomach

• Large in size to hold big meals, due to rabbits being crepuscular.
• Mucus protects the stomach lining and moistens food.
• Hydrochloric acid (HCl) decreases stomach pH and kills bacteria.
• Pepsin breaks down proteins.
• Food mixed with stomach secretions is called chyme (digesta).

Small Intestine

• The primary site of digestion and nutrient absorption.
• The first section, the duodenum, is the site of most digestion. Buffers from the pancreas increase pH and enzymes break down food.
• The middle section, the jejunum, absorbs amino acids, fatty acids, and glucose.
• The ileum absorbs remaining nutrients, including B vitamins.

Large Intestine (Colon)

• Receives undigested material, sorts it, and moves indigestible fiber directly through to be excreted out the body (hay)
• Water is reabsorbed, forming hard, round fecal pellets. Gut motility prevents GI stasis (a life-threatening blockage).
• Soluble fiber/proteins are diverted to the cecum for further fermentation.

Cecum

• A large pouch at the junction of the small and large intestines.
• The cecum has 10 times the stomach capacity of the rabbit.
• Houses symbiotic bacteria and microbes that ferment soluble fiber and proteins, converting indigestible plant material into volatile fatty acids (VFAs).
• VFAs are absorbed directly through cecal wall for energy. B vitamins are critical for metabolism and blood health.
• Produces cecotrophs (nutrient-rich "night feces").

Cecotrophy

• Cecal microbes package fermented material into soft, sticky pellets (cecotrophs) 8-12 hours post-meal.
• Rabbits instinctively re-digest cecotrophs directly from the anus for two-pass digestion.
• The first pass extracts easily digestible nutrients. The second pass absorbs microbial proteins, vitamins, and VFAs from cecotrophs.
• Cecotrophy maximizes nutrient absorption from fibrous diets (e.g., hay, grasses).

Cecotropes

• Cecal pellets, soft feces, or night feces are soft, nutrient-rich pellets produced in the cecum, coated in a protective mucoid membrane.
• They contain high protein (28.5%), B vitamins, and water but low fiber (15.5%) and lipids.
• These are eaten directly from the anus (no contact with ground) and their mucoid layer prevents digestion in the stomach.
• Nutrients are absorbed in the small intestine about 17 hours after the original meal and fermentation continues inside the stomach, for 3-6 hours.
• Cecotrophy regulated by metabolic need for amino acid: Low-protein diets increase cecotrophy and high-protein diets reduce cecotrophy

Importance of Cecotrophy

• Provides amino acids, B vitamins, and volatile fatty acids (VFAs).
• Compensates for low-protein diets.
• Maintains cecal microbial balance and prevents deficiencies and dysbiosis.

Feeding Systems in Rabbits

• Limited feeding provides a measured amount of feed per day which prevents overeating and helps regulate nutrient intake, but requires daily monitoring.
• Free-choice or ad libitum feeding provides unlimited access to feed at all times which ensures rabbits always have food and is suitable for fast-growing rabbits.

Factors Affecting Feed Requirements

• Ration composition includes the nutrient balance of the feed.
• Environmental temperature includes colder temperatures increasing feed intake.
• Breed of rabbit includes larger breeds requiring more feed.
• Size & age includes younger and growing rabbits eating more per unit of body weight.
• Life cycle stage includes pregnant/lactating does and growing kits requiring more feed.

Feeding Behavior & Feed Conversion

• Rabbits eat more at night and meat-type rabbits consume 110–170 g of food per day, depending on size.
• An ideal feed conversion ratio (FCR) is 3:1 (1.4 kg of feed = 0.45 kg weight gain).
• Poor feeding management reduces efficiency.

Nutrient Requirements of Rabbits

• Essential nutrients include protein, energy, fiber, carbohydrates, fat, minerals, vitamins, and water.
• Protein is required for growth, lactation, maintenance, and fur production.
• Dietary protein requirements vary based on animal type and physiological state.
• Lactating does require high dietary protein, often leading to a negative protein balance (18% protein is recommended).

Essential Amino Acids for Rabbits

• Essential amino acids are obtained through feed and cecotroph consumption which include: Histidine, Isoleucine, Leucine, Lysine, Methionine, Phenylalanine, Threonine, Tryptophan, and Valine
• Rabbits compensate for low-protein diets through cecotrophy. Also, they use the functional urea cycle, which supplies sufficient arginine, unlike poultry.

Factors Affecting Protein Requirements in Rabbits

• In relation to Dietary Energy Level, a high-energy diet requires a higher percentage of amino acids due to lower feed intake.
• Low-energy diets decrease amino acid requirements.
• Increasing fiber leads to higher protein requirements in most animals, but rabbits compensate for fecal protein losses by consuming cecotrophs.
• Low temperatures decrease the percentage of dietary protein needed and high temperatures should increase the percentage of dietary protein.
• Excess protein can cause increased plasma urea, raising cecal pH, and creating a favorable environment for Clostridia and Escherichia overgrowth.

Energy Requirements in Rabbits

• Expressed using different parameters:
• Gross Energy (GE) is the total energy
• Digestible Energy (DE) is the energy absorbed.
• Metabolizable Energy (ME) is the energy available after accounting for losses.
• Net Energy (NE) is the energy available for cellular metabolism (35–40% of GE).
• Energy requirements are typically expressed in digestible energy (DE).

Factors Affecting Energy Requirements in Rabbits

• Body size/weight is affected as smaller rabbits have higher metabolic rates and pregnant or lactating does demand higher energy.
• Requirements vary depending on growth, pregnancy, or lactation.
• Cold weather raises energy needs, while hot weather lowers it, and stress and nervousness increase consumption.
• Healthy rabbits regulate feed intake to meet digestible energy (DE) needs.

Effects of Digestible Energy (DE) on Growth & Reproduction

• Increased DE intake affects body weight and the proportion of energy stored.
• Restricting food intake can lead to enteritis, poor growth, and reproductive issues.

Energy Requirements in Pregnancy & Lactation

• High fiber diets cause does cannot able to meet their energy needs, resulting in a negative energy balance.
• Rabbit milk is energy-rich, containing high levels of fat, protein, and dry matter (DM) and lactating does are more efficient during mid-lactation

Fiber Requirements in Rabbits

• Fiber’s play a role in digestive health, metabolism, and overall well-being, particularly in growing rabbits as hindgut fermenters must naturally adapt to a high-fiber diet.
• Diets should promote dental health and gastrointestinal Motility

Dental Health

• Long-strand fibers wear down molars naturally due to plant silicates and large particles, ensuring proper occlusion.

Gastrointestinal Motility

• Larger particles from non-digestible fiber promotes enterocyte turnover and prevent gastrointestinal stasis and its source.

Energy Source

• Fermentation of digestible fiber provides 30-50% of daily energy, with volatile fatty acids (VFAs) serving as a preferred energy source for the colon.
• Nutrient absorption is achieved by Cecotrophy (reingestion of cecal material), which supplies vitamins and essential amino acids.

Microbial Diversity

• Fiber enhances gut microbiota balance and reduces the risk of enteritis, and Ad-libitum hay (free-choice hay) satisfies natural foraging behavior.

Risks of Low-Fiber Diet

• Increased Risk of Gastrointestinal Disorders, Mortality, and Reduced Voluntary Food Intake

Factors Affecting Crude Fiber Digestion

• Factors to consider are Fiber Source, Diet Composition, and Breed Differences

Carbohydrate Requirements in Rabbits

• Carbohydrates digested into starch and simple sugars, although too much grain can lead to starch overload.
• Lipids are small but recommended, and shouldn't exceed 30-35 g/kg (3%-3.5%) relating to growth.

Lipid Digestion in Rabbits

• It's similar to non-ruminants, using pancreatic lipases, bile acids, and micelle absorption in the duodenum.
• Good signs include the absorption of fat-soluble vitamins, essential fatty acids (linoleic, linolenic, eicosapentaenoic, docosahexaenoic), precursors for eicosanoid hormones, improving food palatability etc.
• Essential deficiencies in male reduces gland weight and hair loss
• Water Requirements & Feed Type affect consumption

Water Requirements in Rabbits

• Rabbits require 50–150 mL of water per kg of body weight daily. High fiber/protein diets increase intake, while grain type reduces it. Also take into account the weather conditions and any conditions or diseases.

Warning signs for dehydration

• The signs include reduced excretion and a sticky gum

Treatment dehydration

• Treatment includes twice the maintenance fluids which is 240 mL/kg/day (or 10 mL/kg/hr) for at least 24 hours

Vitamin Requirements in Rabbits

• These include Fat-Soluble & Water-Soluble Vitamin Requirements

Fat-Soluble Vitamin Requirements

• Key points include Cecotropes providing vitamin K/B vitamins and Vitamin D found from hay and sunlight, Vitamin E in alfalfa meal and seed oils etc.

Vitamin Deficiencies & Toxicity Risks

• Deficiency and toxicity risks include chronic diseases such as Vitamin A/E/K

Mineral Requirements in Rabbits

• Minerals impact bone and heart health; there’s also Calcium (Ca) which is essential for many things.
• Diets play a role in this.

1. Hay

• Hay is an essential staple in a rabbit diet, providing satiety, energy and promoting gut health by preventing dental and stomach problems.

Types of Hay

• Leguminous and grasses vary in high-calcium and calories and should contain protein, energy and phosphorus.

Vegetables in comparison to hay

• Should be introduced into the rabbit's diet at 3 months of age to provide nutrients and added benefits.

Pellets in comparison to hay

• Crucial for their nutrient concentration and can be used in combination for optimal growth.

Other ingredients

• Such as water; fruits; and grains

Dietary needs of rabbits

• These include High Fiber, Limited Carbohydrates, Controlled Protein, Fresh Vegetables, & Limited Treats for good health.

Feeding Rabbits During Different Life Stages

• Feeding patterns should adjust depending on the status and health of the animal for safety. Also, maintain annual checkups.

Factors Affecting Feed Intake in Rabbits

• Factors include Age and growth during the physiological stage.
• The reproductive status of the rabbit and its health. The diet in regards to energy and water.
• Their current lifestyle and environment.

Metabolic Diseases of Rabbits

• Issues include Obesity and Metabolic Syndrome due to poor living.
• Or Hairballs due to poor grooming. There's also Mucoid Enteritis due to Colon issues and Pregnancy Toxemia in pregnant does.