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Desert Research Center, DRC, Egypt

Almost the oldest scientific Center in Egypt.

It was established at 1950.

Effect of grazing activity and

supplementary feeding on energy

utilization by goats

By

Ahmed R. Askar, Ph.D.

Professor of Animal Nutrition

Desert Research Center, Cairo, Egypt

Maintenance energy

• Feed ----- 70% of the production cost.

• Maintenance ----- 70% of the feed cost.

• --------------------------------------------------

• Almost = 50% of the production cost

Maintenance energy

• There are many factors affecting the energy requirement for maintenance, such as

• Acclimatization, Patra et al. (2009), Helal et al. (2010)

• Feed quality, Mecawi et al. (2006, 2008), Nassar (2014), Askar et al. (2016)

• Feed intake level, Asmara et al. (2006, 2011, 2012), Helal et al. (2011), Askar et al. (2015), Askar (2016)

• Animal activity, Beker et al. (2009, 2010), Goetsch et al. (2010), Askar et al. (2013, 2015)

• etc

0

10

20

30

40

50

60

70

2400 0200 0400 0600 0800 1000 1200 1400 1600 1800 2000 2200

Time of day

Gra

zin

g,

min

.

T F

Confinement:

Almost: 10% of maintenance

Grazing:

Probably-up to 100% of maintenance

Animal Activity

Energy cost for grazing activity

Relationship between energy

Expenditure and energy

requirements

Gross energy

(heat of combustion)

Fecal energy Digestible energy

Urine energy Methane energy Metabolizable energy

Heat increment Net energy

Used for maintenance Used for production

Energy Expenditure (EE)

Gross energy




Heat increment Used for maintenance

Used for production


Estimate of pasture intake, composition and digestibility

Internal marker

Feces samples

•Hand-plucked forage •Individual plant species

•Simulated grazed samples

Freeze dried then ground and analyzed for internal markers

Metabolizable Energy Intake (MEI)

Metabolizable Energy Intake (MEI)


• Energy expenditure has been determined under

controlled or confinement conditions by

measuring oxygen consumption, and carbon

dioxide and methane production (Brouwer, 1965)

or by only oxygen consumption (McLean, 1972)

in respiratory chambers conditions,

• Expensive

• These conditions are not necessarily reflected

those of grazing animals or in group.

• Cannot follow the animal outside the chamber

Heart Rate (HR) Monitor

• Another potential means of assessing EE by

unrestrained animals is measurement of heart rate

(HR), which has been applied with sheep

(Barkai et al., 2002; El-Meccawi et al., 2008,

2009), cattle (Brosh et al., 1998, 2002), goats

(Puchala et al., 2003,2007; Helal et al., 2010),

and Camels (Askar et al., undergoing).

Heart Rate (HR) Monitor

Hear rate

Monitor (HR)

Indirect

Way

BUT

After

its calibration

To get

EE / HR

ratio

How to get the EE / HR ratio:

Energy expenditure will be measured from O2 consumption and CO2 and CH4 production (Brouwer, 1965), while simultaneously measuring HR with a Polar monitor (24 hours).

Head box

Respiratory calorimetry system

Flowkit 500

CO2, CH4, and O2 analyzers

Air dryer

The face mask open-circuit

respiratory system in DRC

Data collection and integration

McLean (1972)

Energy Expenditure (EE) = 20.53 x O2 consumption

Effect of grazing activity and

supplementary feeding on energy

utilization by goats

• Effect of grazing activity:

• In-door vs. Grazing

• Effect of supplementation:

• With vs. Without

concentrate supplement

MATERIALS AND METHODS

TREATMENTS

IN-DOOR vs. GRAZING

SUPPLEMENTATION

YES YES NO

In-door animals were fed alfalfa hay and supplementation

Grazing animals were grazing fresh alfalfa with or without

supplementation

Supplementation (Concentrate supplement) =

50% of the Metabolizable Energy for Maintenance (MEm)

33 3330

10

15

20

25

30

35

40

In-door

with

Grazing

with

Grazing

without

Body weight, kg

RESULTS AND DISCUSSION

*

53

64 64

10

20

30

40

50

60

70

In-door

with

Grazing

with

Grazing

without

Forage intake, g/kg BW0.75


*

6469

58

20

30

40

50

60

70

80

In-door

with

Grazing

with

Grazing

without

Dry matter digestibility, %


c

a b

1.41.5

1.2

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

In-door

with

Grazing

with

Grazing

without

Gross energy, MJ/kg BW0.75


0.931.07

0.69

0.20

0.40

0.60

0.80

1.00

1.20

In-door

with

Grazing

with

Grazing

without


c

a b

Digestible energy, MJ/kg BW0.75

In-door

with

Grazing

with

Grazing

without

Body weight, BW (kg) 33.8 33.8 33.4

BW 0.75 14.0 14.0 13.9

EE (MJ / day) 6.93 6.82 6.72

EE (kJ / kg BW 0.75) 495 487 484

Heart rate (HR) 79.2 78.5 77.7

EE / HR ratio 6.25 6.20 6.22

Calibration of the heart rate monitor with a face mask open-circuit respiratory system

In metabolic (individual) cages

In-door

with

Grazing

with

Grazing

without

EE / HR ratio 6.25 6.20 6.22

HR (Beat / min) 106c 121b 131a

EE (kJ / kg BW 0.75) 660c 751b 819a

Calculation of the energy expenditure with grazing and in-door goats

In the current experiment (in group)

*

Effect of grazing activity and supplementary feeding on energy expenditure (EE, kJ/ kg

MBW/day)

Energy expenditure,

kJ/kg MBW/day

500

550

600

650

700

750

800

850

900

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Hours of the day

In-door Grazing with supplement Grazing without supplement

In-door

with

Grazing

with

Grazing

without

EE / HR ratio 6.25 6.20 6.22


EE (kJ / kg BW 0.75) 660c 751b 819a

Calculation of the energy balance with grazing and in-door goats

EE / ME intake ratio 87b 86b 144a

In-door

with

Grazing

with

Grazing

without

EE / HR ratio 6.25 6.20 6.22


EE (kJ / kg BW 0.75) 660c 751b 819a

Calculation of the energy balance with grazing and in-door goats

EE / ME intake ratio 87b 86b 144a

EB (kJ / kg BW 0.75) 96.4a 120a -251b

Estimate energy expenditure in

natural rangeland

Gross energy




Heat increment Used for maintenance

Retention energy

=

used for production

Gross energy




EE for grazing activity

+ HP for lact. Preg.,

tissue accretion, etc

Used for maintenance

Retention energy

=

used for production

• Grazing animals have higher intake and

digestibility than those in the confinement.

• The concentrate supplement improved the

forage utilization for grazed animals.

• Grazing activity has a significant effect on the

energy expenditure and requirements, while

supplementary feeding is essential to maintain

grazing animals without deterioration under the

experimental condition.

CONCLUSION

Thank you for your attention

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