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Incubation through the embryos point of view
Sander Lourens (researcher poultry health & welfare)
Bas Kemp (professor at Wageningen University)
Henry van den Brand (Lecturer at Wageningen University)
Marcel Heetkamp (Technician at Wageningen University)
Ron Meijerhof (Hybro B.V., now at HatchBrood B.V.)
Incubation through the embryos point of view
Machine temperature ≠ embryo temperature
Balance between heat loss and heat production (HP)
Factors that affect heat loss
Factors that affect HP
Effects of uncontrolled embryo temperature
Take home message
0
50
100
150
200
250
300
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21
time (d)
he
at
pro
du
ctio
n o
f lo
ss (
mW
)
37,0
37,5
38,0
38,5
39,0
39,5
40,0
tem
pe
ratu
re (
ºC)
heat production
heat loss by evaporation
embryo temperature
machine temperature
development growth plateau phase internal pipping
external pipping
Machine temperature ≠ embryo temperature
0
50
100
150
200
250
300
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21
time (d)
he
at
pro
du
ctio
n o
f lo
ss (
mW
)
37,0
37,5
38,0
38,5
39,0
39,5
40,0
tem
pe
ratu
re (
ºC)
heat production
heat loss by evaporation
embryo temperature
machine temperature
development growth plateau phase internal pipping
external pipping
Machine temperature ≠ embryo temperature
0
50
100
150
200
250
300
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21
time (d)
he
at
pro
du
ctio
n o
f lo
ss (
mW
)
37,0
37,5
38,0
38,5
39,0
39,5
40,0
tem
pe
ratu
re (
ºC)
heat production
heat loss by evaporation
embryo temperature
machine temperature
development growth plateau phase internal pipping
external pipping
Machine temperature ≠ embryo temperature
0
50
100
150
200
250
300
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21
time (d)
hea
t pro
du
ctio
n o
f lo
ss (
mW
)
37,0
37,5
38,0
38,5
39,0
39,5
40,0
tem
pera
ture
(ºC
)
heat production
heat loss by evaporation
embryo temperature
machine temperature
development growth plateau phase internal pipping
external pipping
Machine temperature ≠ embryo temperature
0
50
100
150
200
250
300
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21
time (d)
hea
t pro
du
ctio
n o
f lo
ss (
mW
)
37,0
37,5
38,0
38,5
39,0
39,5
40,0
tem
pera
ture
(ºC
)
heat production
heat loss by evaporation
embryo temperature
machine temperature
development growth plateau phase internal pipping
external pipping
Machine temperature ≠ embryo temperature
Buckeye
96
98
100
102
104
1 4 8 11 15 18Day of incubation
ET
(F
)Multi-stage setter with trolley setting: side view
16-18 13-15 10-12 1-3
37.8
7-9 4-6
38.537.2
36.5
38.5
airfloweggs
40+
0 48 96 144 192 240 288 336 384 432 480
Time (hrs)
37
38
39
40
41
ES
T (
ºC)
Corner
36.0
37.0
38.0
39.0
40.0
41.0
0.0 0.5 1.0 1.5 2.0Air velocity (m/s)
Te
mp
era
ture
(ºC
)
Air temperature
Eggshell temperature
Machine temperature ≠ embryo temperature
Machine temperature ≠ embryo temperature
-0.5
0.0
0.5
1.0
1.5
2.0
2.5
0 2 4 6 8 10 12 14 16 18 20
Time (d)
ET
- M
T (º
C)
v = 0.0 m/s
v = 0.1 m/s
v = 0.5 m/s
v = 2.0 m/s
MT = ET only at 1 point, when heat loss = heat production
timing depends on air velocity across the eggs
differences between incubators
differences between positions in the incubator
Machine temperature ≠ embryo temperature
ET: balance between heat production and heat loss
Heat production
- Time / development
- Physical factors
- Biological factors
- Environmental factors
Heat loss
- Evaporation
- Heat transfer
- temperature difference
- heat capacity
- air velocity
40.0
39.5
39.0
38.5
38.0
37.5
37.0
36.5
36.0
Embryo temperature (ºC)
1. Factors that affect heat loss
2 components that determine heat loss:
Evaporation (latent HP)
• relative humidity and air temperature
• eggshell quality
Heat transfer
• temperature difference between egg and environment
• heat capacity of air (relative humidity)
• air velocity
0
5
10
15
20
25
30
0 25 50 75 100
Relative humidity (%)
Hea
t lo
ss (
mW
)Heat loss by evaporation
Average egg (10% at 37.8oC x 55% RH)
8%
12%
Heat loss: evaporation
Weight loss: 10.000 eggs of 60 g loose 0.6% of initial weight per day
• Eggs incubated at 37.5ºC and 55% RH
• Total weight loss: 150 ml water per hour
• ET is decreased by 0.2ºC
• Uniform at all places in the incubator
Heat loss: evaporation
Weight loss: 10.000 eggs of 60 g loose 0.6% of initial weight per day
• Eggs incubated at 37.5ºC and 55% RH
• Total weight loss: 150 ml water per hour
• ET is decreased by 0.2ºC
• Uniform at all places in the incubator
Spray nozzles or humidifying discs:
• Local cooling effects
• 150 ml water per hour at 10% of the eggs: ET is decreased by 2.0ºC!
Heat loss: heat transfer
Van Brecht et al., 2005
-0.5
0.0
0.5
1.0
1.5
2.0
2.5
0 2 4 6 8 10 12 14 16 18 20
Time (d)
ET
- M
T (º
C)
v = 0.0 m/s
v = 0.1 m/s
v = 0.5 m/s
v = 2.0 m/s
Heat loss: heat transfer
Calculated for eggs incubated at the same MT
2. Factors that affect heat production
Age of the embryo (time)
Physical factors
• storage conditions, egg turning
Biological factors
• egg size, breed, breed age
Environmental factors
• oxygen, carbon dioxide, humidity, temperature
O2
heat
CO2
H2O +
0
20
40
60
80
100
120
140
160
12 13 14 15 16 17 18 19 20
Time (d)
He
at p
rod
uc
tio
n (
mW
)
control
20 days storage
30 days storage
Physical factors: egg storage
Hague et al., 1996
0
50
100
150
12 13 14 15 16 17 18 19 20
Time (d)
He
at p
rod
uct
ion
(mW
)
Turned
Unturned
Physical factors: egg turning
Pearson et al., 1996
Biological factors: egg size
0
50
100
150
200
250
50 55 60 65 70 75 80
Egg weight (g)
HP
at 1
8d (
mW
.egg
-1)
Hoyt (1987)
Vleck et al. (1987)
Lineair (Vleck et al.(1987))
Biological factors: egg size
Lourens et al., 2006
Biological factors: egg size
Lourens et al., 2006
Biological factors: breed
Metabolic heat production (mW per egg)
d R308* R508* Layer* Traditional**
17 151 160 133 130
18 156 149 130 137
19 164 161 127 124
20 252 239 131 169
*Janke, Tzschenktke and Boerjan (2004)
** Romijn and Lokhorst (1960)
Biological factors: breed
Broiler and layer hatching eggs incubated at the same constant MT
Differences in egg size
Eggshell temperature at d18 for layer eggs: 38.3oC
Eggshell temperature for broiler eggs: 0,6 – 0,8oC higher
• metabolic rate higher
• HP and ET are linearly related
• oxygen conductance in broiler eggs higher? (poor eggshell quality?)
• Broiler embryos utilize more energy?
• Efficiency of energy utilization??
Experiment with broiler hatching eggs:
Eggs of similar size: 60 – 65g
EST between d8 – d19: 37.8ºC or 38.9ºC
O2: 17%, 21% or 25%
Climate Respiration Chamber (CRC)
Control Room
0
20
40
60
80
100
120
140
160
8 9 10 11 12 13 14 15 16 17 18 19
Time (d)
Hea
t pro
duct
ion
(mW
.egg
-1) 37.8°C x 17%
37.8°C x 21%
37.8°C x 25%
38.9°C x 17%
38.9°C x 21%
38.9°C x 25%
EST x O2
Source of variation 9 10 11 12 13 14 15 16 17 18 19
EST * * * ** ** ** * - - - -
O2 - - - - - * ** ** ** ** **
EST x O2 - - - - - - - - - * *
1
High EST initially increased HP
Between d 14 – d 17, O2 determined HP in both EST treatments.
At d 18 and d 19, HP was highest for the combination of high EST
with high O2 and lowest for the combination of high EST with low O2.
CL BW YFB RY HW LW HT
(cm) (g) (g) (g) (g) (g) (d)
EST
37.8°C 19.7 41.5a 37.4a 4.0 0.40a 1.65a 20.5a
38.9°C 19.8 39.8b 35.8b 4.0 0.33b 1.53b 19.8b
O2
17% 19.0c 40.6 35.3b 5.3a 0.36 1.49 20.2
21% 19.9b 40.6 36.9a 3.7b 0.35 1.63 20.2
25% 20.4a 40.7 37.7a 3.0c 0.38 1.65 20.2
EST NS * * NS ** * **
O2 ** NS * ** NS NS NS
ESTxO2 NS NS NS NS NS NS NS
0
25
50
75
100
19.0 19.5 20.0 20.5 21.0 21.5
Time (d)
Hat
ched
(%
)
37.8ºC x 17% 37.8ºC x 21% 37.8ºC x 25%
38.9ºC x 17% 38.9ºC x 21% 38.9ºC x 25%
ET = 37.8ºC
ET = 38.9ºC
Hatch window???
In general,
For eggs of the same size, hatch time decreased when flock age
increased
Increased oxygen conductance in eggs of older flocks increased HP
As a result, ET increased as well, which decreased hatch time!!
What factor determines HP?
Energy utilization
EfficiencyO2
heat
CO2
H2O + +
%100x)()()(
)(YFB kJRYkJYolkkJAlbumen
kJYFBE
−+=
O2
heat
CO2
H2O + +
YFB RY
Energy utilization, efficiency of energy transfer between egg and hatchling (EYFB). After Lourens et al. (unpublished).
152a138b119c148a131bHP at d18 (mW.egg-1)
52.454.952.550.8b55.7aEYFB (%)326a313b286c311305Utilized (kJ)
31c43b68a4648RY (kJ)
171a172a150b158b170aYFB (kJ)
281281282282280Yolk (kJ)
7675737673Albumen (kJ)
25%21%17%38.9oC37.8oC
O2EST
Table 4. Factors affecting HP through energy utilization and efficiency of energy transfer between egg and hatchling (EYFB)
YesNoEggshell temperature
NoYesOxygen
NoYesBreed
NoYesEgg weight
EYFBEnergy utilization
Factors affecting HP through energy utilization and efficiency of energy transfer between egg and hatchling (EYFB). After Lourens et al. (unpublished)
Environmental factors
O2
heat
CO2
H2O + +Concentration
Air pressure
Altitude
Eggshell conductance
Oxygen availability to the embryo (red blood cells)
Environmental factors: H2O
RH, MT, and conductance determine weight loss during incubation
Development of air cell, required for internal pipping
But focus on ET first…
Ventilation early in incubation removes water from the machine
Not required
Creates cold spots
Spray nozzles / humidifiers to add moisture
High CO2 level during week 1 stimulates development of membranes to
support gas exchange later in week 3
High RH during week 1 needs to be compensated later
ET: balance between heat production and heat loss
Heat production
- Time / development
- Physical factors
- Biological factors
- Environmental factors
Heat loss
- Evaporation
- Heat transfer
- temperature difference
- heat capacity
- air velocity
40.0
39.5
39.0
38.5
38.0
37.5
37.0
36.5
36.0
Embryo temperature (ºC)
ET: balance between heat production and heat loss
Heat production
- Time / development
- Physical factors
- Biological factors
- Environmental factors
Heat loss
- Evaporation
- Heat transfer
- temperature difference
- heat capacity
- air velocity
40.0
39.5
39.0
38.5
38.0
37.5
37.0
36.5
36.0
Embryo temperature (ºC)
Eggshell temperature is the key!!!
To know EST, you have to measure it
Keep EST close to 37.8oC constantly
Take home message:
