Lecture 11 Week 6 - Poultry Flashcards
How long does a chicken live for?
10-15 years
What type of breeders are chickens? How have humans exploited this?
They’re SEASONAL breeders, genetic selection has allowed them to breed all year round.
What is a Rhode Island chicken an example?
What is the offspring of a RIR male & RIW female?
A cross between many different chicken breeds. Can be red or white.
White male & brown female - males are euthanised.
Why did egg consumption skyrocket in the early 2000s?
Realised that the cholesterol in eggs was not actually that bad for you.
What % of eggs does Australia export?
5% - therefore we mostly consume domestic eggs.
What are 4 reasons why monogastric meat consumption is increasing?
- Relatively cheap to produce
- Accessible
- Considered healthy
- Growing population = need more food
Is there in an increase in free range egg consumption compared to cage eggs?
a greater percentage of eggs bought are FR.
What are 5 trends seen in the egg industry?
- Increase in the number of pullet & layers in Australia
- Increase in number of eggs being produced, therefore increase in value of the industry
- Increase in the price of specialty eggs - cage, FR & barn-laid all stayed the same price over time
- The number of eggs we are eating has increased
- Genetic progress - the average number of eggs a chicken can lay has increased (an extra 2.3 eggs/hen/year)
* ** Hens ‘persist’ in laying for longer. They can lay and lay and lay for longer periods of time before starting to reduce
What differentiates an egg laying chicken to a meat producing chicken?
Egg laying = smaller, more viable
Meat producing = larger with bigger breast muscles
Why is an egg a nutritionally complete food? Can it be supplemented with anything else?
It contains proteins, fats, vitamins & minerals. Can make it more complete by supplementing it with selenium, omega-3 or vitamin E —> ‘designer eggs’
What are some ‘supposed’ disadvantages of FR eggs?
- Increased mortality
- Poorer welfare
- Lower productivity - diet isn’t as controlled
What are 2 ways the weight of an egg can be altered?
- Adding methionine into the feed
2. Making it darker so hens hold off on layer eggs until they are older & bigger
Which part of the eggs takes the longest to produce? How many days does it take?
Yolk - 9 days
How long does it take to form an egg?
25 hours
What comprises the yolk? What is the name of the thin membrane surrounding it?
Lipids & proteins (& some antibodies). Most nutrition comes from the yolk. Vitelline membrane.
How many membranes enclose the albumen?
2 - fused except at air space.
What is the chalaza?
2 spirally proteins (1 at each end of egg) that help to stabilise the yolk.
What 4 parts comprise the egg shell?
Mammillary layer, palisade, pores, cuticle
What are 4 consumer expectations to do with eggs?
- Shell = uniform colour, free from defects
- Yolk = uniform colour, free from blood spots
- Albumen - stays together when egg is cracked on flat surface
- Neutral taste
* ** Overall, homogenous appearance
What 2 anti-spoilage mechanisms does an egg have?
- Physical attributes e.g. hydrophobic, proteinaceous layer (cuticle) which overlies the eggshell and pores, also a porous shell that allows gas exchange
- Chemical e.g. albumen
What are external quality indicators of eggs?
Basically all to do with the shell:
- Shell defects e.g. cracks - ‘Candled’ to detect these
- Egg shell weight as part of total weight
- Visible shell defects
- Eggshell thickness (using calipers)
What are internal quality indicators of eggs?
- pH (9.3 inhibits bacterial growth)
- Albumen height (indicator of membrane integrity and structure of proteins) - as egg ages proteins denature & also amount of water absorbed decreases
- Albumin pH
- Albumin:Yolk ration (decreases with age)
- Haugh unit (freshness measure)
- Yolk size (ratio compared to rest of egg increases) & colour (decreases with storage)
What 4 environmental factors can affect egg quality?
- Heat stressed hens – reduced egg quality
- Environmental – contaminated environment
- Animal behaviour – feather pecking, cannabilism, egg consumption
- Diet quality: protein quality, digestibility of feed, adequate level of calcium
What is one way that egg quality can be maintained after purchase?
Refrigerate them! High temperature 25°C versus 5°C increases the rate of egg degradation over time.
