Amino acid nutrition in egg production industry

Teru Ishibashi

ABSTRACT

The egg production industry is facing various problems that need to be solved. For amino acid nutrition to achieve scientific and economical feeding of laying hens, it is necessary to elucidate the content, digestibility, or availability of nutrients of feedstuffs and feeds and the requirement of amino acids for laying hens. In addition, improvement to quality of eggs and meat of spent hens, methods of management and development of new feedstuffs are essential. For sustainable animal production, decrease in excreta and animal welfare should be studied. The real-time determination of content and digestibility of amino acids in feedstuffs are essential for formation of feeds. Recent advances in the near infrared reflectance analysis will be able to determine the content, digestibility and availability of nutrients in feedstuffs and feeds, if we have a supplemental amount of conventional analysis to define the calibration population. The amino acid requirements are affected by various factors. Therefore the method to quickly and exactly determine amino acid requirements in response to various factors is necessary. By using plasma free amino acid concentration as a criterion, it is possible to determine amino acid requirements in various conditions of laying hens within a short experimental period, repeatedly using the same animals. Because the amino acid requirements differ among individual animals, it should be expressed as grams per hen per day. Practically, it is impossible to formulate various feeds for individual hens. The various expressions have been developed and these expressions have advantages and disadvantages. The nitrogen excretion of laying hens is easily reduced by reducing dietary nitrogen levels and restricting the feed intake. The availability of amino acid may be improved by feeding management, and supplementing enzyme, but the quality of eggs and meat of spent hens and welfare of laying hens are not affected by amino acid nutrition.

Adapted from materials provided by Blackwell Publishing.

How to test if an egg is fresh

Firstly, fill a deep bowl with water and carefully lower the egg into the water.

A very fresh egg will immediately sink to the bottom and lie flat on its side. This is because the air cell within the egg is very small. The egg should also feel quite heavy.

As the egg starts to lose its freshness and more air enters the egg, it will begin to float and stand upright. The smaller end will lie on the bottom of the bowl, whilst the broader end will point towards the surface. The egg will still be good enough to consume, however, if the egg fully floats in the water and does not touch the bottom of the bowl at all, it should be discarded, as it will most likely be bad.

A bad egg will also feel extremely light in weight and give off a pungent smell.

The second method to test the eggs freshness is by breaking the egg onto a flat plate, not into a bowl.

The yolk of a very fresh egg will have a round and compact appearance and it will sit positioned quite high up in the middle of the egg. The white that surrounds it will be thick and stays close to the yolk.

A less fresh egg will contain a flatter yolk, that may break easily and a thinner white that spreads quite far over the plate.

Nutrient Content of a Large Egg

Nutrient (unit)	Whole Egg	Egg White	Egg Yolk
Calories (kcal)	75	17	59
Protein (g)	6.25	3.52	2.78
Total lipid (g)	5.01	0	5.12
Total carbohydrate (g)	0.6	0.3	0 .3
Fatty acids (g)	4.33	0	4.33
Saturated fat (g)	1.55	0	1.55
Monounsaturated fat (g)	1.91	0	1.91
Polyunsaturated fat (g)	0.68	0	0.68
Cholesterol (mg)	213	0	213
Thiamin (mg)	0.031	0.002	0.028
Riboflavin (mg)	0.254	0.151	0.103
Niacin (mg)	0.036	0.031	0.005
Vitamin B6 (mg)	0.070	0.001	0.0069
Folate (mcg)	23.5	1.0	22.5
Vitamin B12 (mcg)	0.50	0.07	0.43
Vitamin A (IU)	317.5	0	317
Vitamin E (mg)	0.70	0	0.70
Vitamin D (IU)	24.5	0	24.5
Choline (mg)	215.1	0.42	214.6
Biotin (mcg)	9.98	2.34	7.58
Calcium, Ca (mg)	25	2	23
Iron, Fe (mg)	0.72	0.01	0.59
Magnesium, Mg (mg)	5	4	1
Copper, Cu (mg)	0.007	0.002	0.004
Iodine, I (mg)	0.024	0.001	0.022
Zinc, Zn (mg)	0.55	0	0.52
Sodium, Na (mg)	63	55	7
Manganese, Mn (mg)	0.012	0.001	0.012

Egg

Definition:

A hard-shelled reproductive body made by birds. There are many different types of eggs, but chicken eggs are the ones that are used most commonly in cooking. Domestic chicken eggs have white or brown shells. The color of the shell does not affect the flavor or nutritional value of the egg.

Grades and Sizes

Eggs are sold by both grade and size. Grade primarily measures an egg's appearance once it is broken out of the shell. Most eggs sold are Grade AA or A. Grade AA eggs spread less and have a slightly higher, firmer yolk and white than Grade A eggs. Grade B eggs spread more than the other two grades and usually are sold only for use by food manufacturers.

The sizes of eggs include jumbo, extra large, large, medium, small, and peewee. Price differences are based largely on egg size, with larger sizes costing more per dozen than smaller sizes. There is about a 3-ounce difference in weight per dozen between sizes.

Selecting

Select clean, fresh eggs from refrigerated display cases. Don't use dirty, cracked, or leaking eggs. They may have become contaminated with harmful bacteria.

Storage

Fresh eggs can be refrigerated for up to 5 weeks after the packing date (a number stamped on the carton from 1 to 365, with 1 representing January 1 and 365 representing December 31).

To store raw egg whites, refrigerate them in a tightly covered container for up to 4 days. Refrigerate raw yolks, covered with water, in a tightly covered container for up to 2 days. Refrigerate hard-cooked eggs in their shells in their cartons for up to 7 days.

Raw whole eggs, whites, and yolks can be frozen to use in recipes. Eggs cannot be frozen in their shells.

To freeze whole eggs, break them into a bowl and beat just until blended before freezing in a freezer container. If freezing several eggs in one container, indicate the number of eggs on the label.

To freeze raw egg yolks, add one-eighth teaspoon salt or 1/2 teaspoons sugar or corn syrup per 4 yolks. The salt or sugar will help prevent gelling. Freeze the yolks in a freezer container.

When freezing raw egg whites, place each one in a different compartment of an ice-cube tray. Cover tightly with plastic wrap and freeze until solid. Transfer the egg white cubes to a freezer container and freeze.

Thaw the eggs in the refrigerator overnight and use yolks or whole eggs immediately after thawing. Egg whites can sit at room temperature for 30 minutes after thawing. Allowing them to stand will give them better volume when beating. Be sure to thoroughly cook eggs that have been frozen.

Safety Tips

When cracking eggs, avoid getting any eggshell in with the raw eggs.

When separating eggs, don't pass the yolk from shell half to shell half. Instead, use an egg separator, or pass the egg through clean, slightly separated fingers, so that if bacteria are present on the shell, it won't contaminate either the yolk or white.

Be sure to wash your hands, utensils, and countertops after working with eggs.

Serve hot egg dishes as soon as they're cooked. Refrigerate cold egg dishes immediately. Chill leftovers promptly and reheat thoroughly before serving.

Eating uncooked or slightly cooked eggs may be harmful because of possible bacterial contamination. The individuals most susceptible include the elderly, infants, pregnant women, and .those who are already ill. Check with your doctor to see if you are at risk. If you are, you probably should avoid eating foods that contain raw or partially cooked eggs.

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