Basic Nutrition for Amazon Parrots

Abstract

Introduction

The Amazon Parrots belong to the order Psittaciiformes, in the class Aves. They are characterized by their predominantly green color, with red, blue and yellow highlights, and their heavy hooked beaks.

They are credited with being a friend to the pirate who always seemed to be missing an earlobe. More recently they are accused of horrible crimes against the farmers of South and Central America such as crop destruction. Most of us keep them to entertain us, and to be our pets.

Digestive System

Next to his color, the beak of a parrot is his most striking feature. This hooked structure is of very solid construction (Fig. 1) and has massive sized mandibles. Besides its obvious use in feeding, the beak is used as an aid to climbing and in behavioral display. The strength of the parrots beak is best judged during his feeding. A kernel of dried corn poses no obstacle. A hazel nut or an almond is cracked almost as if it were a sunflower seed. Obviously, perches, wood toys and pine molding can be reduced to toothpicks in a few days.

It seems that there is more to the beak than a mere feeding device. Many birds consume fruits, seeds, and nuts and their digestive systems are adapted to these foods without crushing beaks. Normally, most birds crack a seed and swallow the meat whole, or swallow it shell and all, letting the gizzard crush the object. Parrots, however, have their own method of particle reduction. The upper beak and tongue hold the food, and the lower beak grinds or shaves off pieces to be swallowed.

The tongue of parrots is markedly different from the tongues of other birds in that it is highly muscled. This strong

musculature is an aid to feeding. It also has a function in the well-known phonation of parrots. Normally a bird alters its vocal resonation by moving its glottis upwards and downwards. Parrots have the added option to use the tongue to alter the shape of the pharynx (the rear portion of the oral cavity) and shunt vocalizations through the nasal passages (Nottebohm, 1976).

The tongue of Amazons is broader at the tip than the base, bearing some resemblance to a thumb. It has shallow grooves in the central lateral edges. Salivary glands are in the back of the mouth (oropharynx), leaving the tongue dry. Taste glands are present on the surface of the tongue, but the density is not known. Hot and cold sensation also appears to be present.

Along with other feeding adaptations, the parrot has the ability to hold food in its foot and raise it to its mouth to eat. A majority of Amazons (71 % ) appear to use the left foot for feeding (Friedman and Davis, 1938).

The esophagus of parrots is typical of most omnivores and has abundant mucous glands. The crop is not as well developed as in many other seed eaters.

As in many other birds the Amazons' proventriculus, or glandular stomach, is lined with glands secreting pepsin and hydrochloric acid. These tubuloalveolar glands open into a collecting chamber that discharges by a duct into the lumen (food containing interior) of the proventriculus.

The ventriculus, or gizzard, is not of the muscular type as one would expect in a seed eater, possibly due to particle reduction by the beak.

The pancreas has two 'ventral and one dorsal lobe. The two ventral lobes may be fused at their posterior end. Each ventral lobe has a duct leading to an opening in the

ascending duodenum, one in front and the other behind the left hepatic duct. The dorsal lobe is composed of smaller lobes or lobules scattered around the beginning of the portal vein. The anterior lobule is the largest, and a duct goes from it to the ascending limb of the duodenum. The pancreas which secretes digestive enzymes, also secretes the hormones glucagon and insulin, making it an endocrine organ. Both are used in the regulation of blood sugar levels.

Parrots have no gall bladder. Bile from the liver travels down the bile ducts directly to the duodenum. In relative length, villi structure, and gland abundance, the Amazons' duodenum is similar to those of other birds. The rest of the intestine is equally typical except for the complete absence of ceca. Ceca are outpocketings of the large intestine which may have functions in fermentation of cellulose, water absorption and bacterial production of certain vitamins.

General Nutrition

We need to know a little about general avian nutrition before we can discuss Amazons, specifically. Birds like humans have a single stomach and are called monogastric. This makes their dietary nutritional requirements more critical than those of polygastrics or ruminants (cows, sheep). Very little information is available on the nutritional requirements of any birds other than domestic poultry. However, we shall try to make some generalizations.

Water is essential for all birds, but can be supplied by various means. A part of this water can be supplied by succulent foods. Parrots do need fresh drinking water.

Carbohydrates (starches and sugars) are provided by seeds, cereals and tubers. Starches are polysaccharides or long chains of monosaccharides. The most important monosaccharide or free simple sugar is glucose. It circulates in the blood, is trans-

ported across the cell membranes, and is utilized in oxidative metabolism as a source of energy. Glucose can be made metabolically by gluconeogenesis, or can be obtained from the breakdown of polysaccharides. Fructose and other monosaccharides are less important except to some fruit eating birds.

Birds are able to utilize fats and oils. Triglycerides (glycerol plus three fatty acids) appear to be utilized more readily than free fatty acids. The requirement for an essential fatty acid (usually linoleic acid) is generally accepted. Linoleic acid is abundant in most seeds and generally need not be added to the diet.

Protein requirements are not only quantitative but also qualitative. Proteins are made up of amino acids which are put into two categories: essential and non-essential. The body cannot synthesize enough of the essential amino acids to meet its requirements. The non-essential amino acids can be synthesized from the essential ones, but the metabolic cost of this synthesis can be excessive. So all of the essential and most non-essential amino acids should be provided in the diet.

Most essential amino acids are the same for all monogastric animals. They are arginine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine. In addition, glycine is needed by birds because it is a part of the uric acid molecule that facilitates nitrogen excretion.

The main symptom of a protein deficiency or of an amino acid deficiency is essentially poor growth. A deficiency of the amino acid lysine can cause a loss of feather pigmentation.

Vitamins for birds, as for all life, are essential and some act as coenzymes in biochemical pathways. All captive birds should have vitamin supplements added to their diets. Marginal deficiencies, in general, can result in retarded growth, poor egg production, and hatchability. Specific and serious deficiences in chickens can result in dermatitis, diarrhea, deformaties, paralysis, respiratory difficulties, internal hemorrages, and death. Some of these have been seen in caged birds also.