Ceratonia siliqua

Carob, St. John's bread, locust bean

Evergreen tree up to 10 m high with smooth grey bark. The glossy dark-green leaves are bipinnate with almost round, leathery leaflets, 2-5 cm long. The green flowers occur in short spikes on woody branches. The pods are brown, usually straight and 10-20 cm long. The seeds are embedded in the thick fleshy sugar-rich pods. The seeds, all being the same size, are used as weights in eastern Mediterranean countries (the word "carat" comes from the Arabic name of the seeds).

The tree is native to the mediterranean countries but is now found in many arid areas of the subtropics. The species is trioecious: some bear only staminate flowers, others only pistillate flowers, and still others only hermaphrodite flowers. For this reason the trees should be planted in groups of ten or more, as otherwise pollination may not take place.

Carob is cultivated for its abundance of pods, rich in sugar when ripe, which are used for the production of alcohol or ground with the seeds to make carob bean meal for animal feed. The seed, representing about 10% of the whole pods, are processed for mannogalactan, and germ meal is produced as a by-product. The seeds are extremely hard; unless ground before feeding they are not digestible.

Carob beans are very palatable to cattle and pigs, but they contain tannic acid, which reduces digestibility, especially of protein. If large amounts are fed, the tannic acid will reduce also the digestibility of other feeds used together with carob. Carob bean meal has been used as a substitute for grain in the diet for ruminants; 10% is a common level but higher proportions have been used. If used for pigs, the liveweight gain decreases in proportion to the amount of carob bean meal included in the diet; a level of 10% or less will affect the liveweight gain only very slightly. The maximum amount of carob bean meal that can be included in the pig diet is about 20% of the total ration. For poultry the only available nutrient component seems to be the sugar, and poor results are obtained because of the bulkiness. If supplemented with fat to increase the energy intake, carob bean meal gives satisfactory results when it constitutes up to 20% of the diet.

Carob germ can be used for all classes of livestock, and up to 20% without supplementation has been used in poultry diets with good results.

The pulp obtained from the industrial processing of alcohol has a satisfactory chemical analysis, but is nearly indigestible and unpalatable to animals.

Carob beans have been used as substrate in the production of microbial protein for animal feeds in Cyprus.

As % of dry matter

DM

CP

CF

Ash

EE

NFE

Ca

P

Ref

Pods ground

89.3

6.9

12.0

3.7

1.2

76.2

0.56

0.12

229

Pods, Cyprus

90.7

5.4

6.3

3.3

0.4

84.6

369

Seeds, Italy

18.5

8.0

3.5

2.0

68.0

327

Pod husk, Zimbabwe

4.2

10.2

2.8

2.4

80.4

19

Germ meal

89.4

45.1

3.6

5.9

5.2

40.2

0.11

0.97

121

Residue after alcohol

production, Cyprus

7.7

15.0

4.5

0.2

72.6

0.10

369

Residue after sugar

extraction, Cyprus

6.5

13.4

2.4

0.3

77.4

"

Digestibility (%)

Animal

CP

CF

EE

NFE

ME

Ref

Pods

Sheep

2.2

40.3

64.4

62.3

2.03

327

Seeds

Sheep

67.0

64.8

70.5

87.8

3.00

"

Germ meal

Sheep

90.3

85.2

82.9

11.1

2.36

121

Fermented residue

Sheep

15.0

49.0

0.0

79.0

2.40

365

Pods, ground

Pigs

15.0

46.0

99.9

80.0

2.84

229

Amino acid composition as % of crude protein

Germ meal

Ref

158

Arg

Cys

Gly

Hys

Ils

Leu

Lys

Met

Phe

Thr

Try

Tyr

Val

1.2

1.4

5.5

4.7

4.7

6.1

5.9

0.8

4.5

4.4

1.0

-

3.6