Hen reproductive system

Question 1

Anatomy of hen reproductive system

Answer 1

Left ovary and oviduct, right are vestigial (may become cystic)

Cephalic end of the left kidney

Immature ovary contains >14000 ova

2000 visible to the naked eye

Maximum 350 reach maturity and are ovulated in domestic species annually

Dont live that long (about 100 weeks???)

Question 2

Anatomy of oviduct of poultry

Answer 2

5 distinctive areas

infundibulum
- thin fimbrinated portion that engulfs ova when released
- sperm nests
- 30 minute duration

magnum
- glandular organ
- albumen formed
- 3 hours

isthmus
- less glandular
- 1.25 hours

uterus or shell gland
- thick muscular
- shell
- shell pigment
- 20.75 hours
- cuticle

vagina

Question 3

Ovulation in hens

Answer 3

Hormonal control of ovulation complex

Progesterone produced by the maturing F1 follicle

LH influences this maturation and LH release dependent on light/dark cycle

Occurs in a specific time frame, if it does not then it results in a non-egg laying day - more frequent as she gets older

Laying and brooding habits vary between spp.
○ Clutches
○ Number of eggs and interval between eggs
○ Domestic hens bred to lay eggs and not to go broody and incubate the eggs

Question 4

Light stimulation of hens

Answer 4

Light energy stimulates the hypothalamus

Not the entire period of light
○ Initial lights on and successive 11-13 hours (photosensitive phase)
○ Perceives light in the period 11-13 hours after lights on then stimulatory

Light sets the circadian rhythm, biological clock

Important since alteration can significantly affect production

Dont want to stimulate them when in rearing phase

Question 5

Photosensitivity of hens

Answer 5

Intensity of the light more important, darkness is non-stimulatory

Intensity of light period 10x >intensity of dark period

Important not to reduce light intensity, affects lay

Question 6

Clutch length

Answer 6

Longer clutch length increases overall production

E.g. 30 eggs in 31 days = 96.7% production

Breeders at 85% production average clutch will be 7-8 eggs, some birds>20 eggs and some very short of erratic producers

Long clutches only possible when successive ovipositions lag each other by a short time. This is in part
○ Age related
○ Genetic

Older hen has shorter clutches

The position of a hatching egg in the clutch appears to influence its physical characteristics, this may influence the viability of the chick

Eggs laid earlier in the day tend to be larger while those laid later in the day (end of clutch) tend to have more shell material

Evidence suggests that the first egg laid in a clutch have higher rate of embryo mortality (longer retention in the oviduct?)

Longer clutches would result in better embryo viability

Question 7

What is a pullet?

Answer 7

A laying hen before she is sexually mature (the chicken version of a heifer)

Question 8

Light programs for pullets

Answer 8

Rear on 8hrs of light

Stimulate with light when they reach body maturity
○ Absolute BW
○ % fat
○ Stimulating too early can affect overall production

Rapid growth of ova reach maturity in 9-10 days

Follicular hierarchy, 4-8 follicles in chicken. Depends on laying sequence length

Longer clutch length means more maturing ovi

Question 9

Composition of a hens egg (outside to inside)

Answer 9

Shell
Shell membrane
Air space
Outer layer of thin albumin
Fibrous layer
Inner layer of thin albumin
Chalaza
Chalaziferous layer
Blastoderm
Vitelline
White yolk and yellow yolk
Latebra

Question 10

Albumen of a hens egg

Answer 10

Four distinct layers
- Chalaziferous attached to yolk
- Inner liquid
- Dense of thick layer
- Outer thin or fluid layer

Question 11

What proteins make up the albumen of a hens egg

Answer 11

§ Ovalbumen 54%
§ Ovotransferrin
§ Ovoglobulin
§ Lysozyme bacteriocidal
§ Ovo-mucoid-protein enzyme inhibitor
§ Ovomucin-insoluble fibrous glycoprotein

Question 12

Shell of a hens egg

Answer 12

○ Four layers
○ 2 proteinaceous membranes
○ True shell
○ Proteinaceous cuticle

Question 13

Shell formation

Answer 13

• Shell is mainly formed in uterus
  
  • True or calcified shell consists of
    ○ Mammilary
    ○ Pallisade or spongy layer
  • Dry matter is:
    ○ 2% organic material
    ○ 98% crystalline calcium carbonate
    ○ MG, PO4, Na, K, and citrate

Question 14

Shell pigment

Answer 14

Shell pigment laid down in uterus

Brown pigment
○ Protoporphyrin IX a by-product of haemoglobin

Blue pigment
○ Oocyanin bile pigment

Question 15

Calcium around laying time

Answer 15

Turnover of Calcium very high

Last 15 hrs of shell formation calcium moves across shell gland rate 100-150mg/hr- Active transport, energy dependant

Calcium not stored in shell gland must come from blood.

If an egg shell problem check what they are feeding, simple things can have a dramatic effect

Serum calcium rises from about 10mg% to 16-30% in 10 days before a pullet starts lay

Rise is oestrogen dependant and results in increase in Ca+ binding protein production

Can grind up oyster shell for calcium supplement

Skeletal weight increases by approximately 20% in 10 days prior to onset of lay, responsive to oestrogen and

Production of the egg is a really dynamic process so if thing go wrong with nutrition, management, you will lose eggs- first sign likely thinner shells, then no shell at all

Question 16

Hatching eggs

Answer 16

For breeding purposes, require fertile eggs

Usually housed male to female ratio 9% at 24 weeks and reduce to 6.5% by depletion

Eggs collected daily

Stored on setter trays in controlled temperature depending on egg storage time. Ideal storage time is 3-5 days between laying and setting

Trigger point is 25 degrees so must be below this, otherwise embryo will die

Eggs sanitised

Hatchery collections 2-3x /week

Small eggs lead to small chicks which dont survive as well so selected for size as well