Comparative performance of broiler chickens offered ten equivalent diets based on three grain sorghum varieties

as determined by response surface mixture design

Sonia Y Liu, Ha H Truong, Ali Khoddami, Amy F Moss, Peter C Thomson, Thomas H Roberts and Peter H Selle

sonia.liu@sydney.edu.au

Objectives

Using mixture design to generate response surfaces to interpret variations in performance of broilers offered nutritionally equivalent diets based on three different

sorghum grains

Experimental diets

• Three characterised sorghum (Block I,

Liberty and HP) with different protein, kafirin and phytate contents were used to formulate three nutritionally equivalent basal diets

• Through 3.2 mm hammer-mill screen • Steam-pelleted at a conditioning

temperature of 80°C • Following steam-pelleting, the three

basal diets were proportionally mixed to form ten dietary treatments

HP (0,0,100)

(0, 50, 50)

(50, 0, 50)

Block I

(100, 0, 0)

Liberty

(0, 100, 0)

(50, 50, 0)

(33.3, 33.3, 33.3)

(16.7, 16.7, 66.6) (16.7, 66.6, 16.7)

(66.6, 16.7, 16.7)

0

10

20

30

40

50

60

70

80

90

0 20 40 60 80 100

• 6 replicates (6 birds per cage) of 360 male Ross 308 chicks • 7 to 28 days post-hatch • Total excreta collected from day 25-27 post-hatch • Differences were considered significant at P < 0.05 by using

the JMP® 9.0.0 (SAS Institute Inc. JMP Software, Cary, NC). Response surface and contour plots are generated by R 3.0.3.

Bird management

Dietary effects on weight gain (P = 0.139)

1387

1431

1409 1421 1420

1441

1359

1432 1432

1392

1 2 3 4 5 6 7 8 9 10 Treatment 1A 2B 3C 4D 5E 6F 7G 8H 9I 10J Block I (%) 100 0 0 50 50 0 66.6 16.7 16.7 33.3 HP (%) 0 100 0 50 0 50 16.7 66.6 16.7 33.3 Liberty (%) 0 0 100 0 50 50 16.7 16.7 66.6 33.3

The predicted optimal weight gain 1439 g/bird was achieved when the proportions of diets based on Block I, HP and Liberty were equal to 0.0%, 79.2% and 20.8%, respectively.

Dietary effects on FCR (P = 0.142)

1.660

1.631

1.663 1.664

1.650

1.608

1.647

1.615 1.606

1.626

1 2 3 4 5 6 7 8 9 10 Treatment 1A 2B 3C 4D 5E 6F 7G 8H 9I 10J Block I (%) 100 0 0 50 50 0 66.6 16.7 16.7 33.3 HP (%) 0 100 0 50 0 50 16.7 66.6 16.7 33.3 Liberty (%) 0 0 100 0 50 50 16.7 16.7 66.6 33.3

The predicted optimal FCR 1.486 g/g was achieved when the proportions of diets based on Block I, HP and Liberty equal to 0.0%, 55.6% and 44.4%, respectively.

Dietary effects on AMEn (P = 0.158)

11.87 11.85

12.14

11.81

12.00

12.20

12.05 12.03

12.14

11.90

1 2 3 4 5 6 7 8 9 10 Treatment 1A 2B 3C 4D 5E 6F 7G 8H 9I 10J Block I (%) 100 0 0 50 50 0 66.6 16.7 16.7 33.3 HP (%) 0 100 0 50 0 50 16.7 66.6 16.7 33.3 Liberty (%) 0 0 100 0 50 50 16.7 16.7 66.6 33.3

The predicted optimal AMEn 12.38 MJ/kg was achieved when the proportions of diets based on Block I, HP and Liberty equal to 0.0%, 32.0% and 68.0%, respectively.

Dietary effects on ME:GE ratios (P = 0.029)

0.800a 0.800a

0.827c

0.802a

0.814abc

0.832c

0.807ab

0.816abc

0.823abc

0.811abc

1 2 3 4 5 6 7 8 9 10 Treatment 1A 2B 3C 4D 5E 6F 7G 8H 9I 10J Block I (%) 100 0 0 50 50 0 66.6 16.7 16.7 33.3 HP (%) 0 100 0 50 0 50 16.7 66.6 16.7 33.3 Liberty (%) 0 0 100 0 50 50 16.7 16.7 66.6 33.3

The predicted optimal ratio 0.845 MJ/MJ was achieved when the proportions of diets based on Block I, HP and Liberty equal to 0.0%, 31.1% and 68.9%, respectively.

Distal ileal protein digestibility = 0.00618𝑃𝐵𝑙𝑜𝑐𝑘𝐼 + 0.00691𝑃𝐻𝑃 + 0.00651𝑃𝐿𝑖𝑏𝑒𝑟𝑡𝑦

The predicted optimal distal ileal protein digestibility of 0.691 will be achieved when the diet contain 100% sorghum HP.

In contrast, the relationship between starch digestibility and the proportions of the three basal diets may be predicted by the following equation:

Distal ileal starch digestibility = 0.00887𝑃𝐵𝑙𝑜𝑐𝑘𝐼 + 0.00883𝑃𝐻𝑃 + 0.00894𝑃𝐿𝑖𝑏𝑒𝑟𝑡𝑦

The predicted optimal distal ileal protein digestibility of 0.894 will be achieved when the

diet contain 100% sorghum Liberty.

Nutrient concentrations in three sorghums

Kafirin Phenols Phytate ME:GE AMEn

Kafirin

Phenols

Phytate

ME:GE

AMEn

1.000

r = 0.999

P < 0.001

r = 0.965

P < 0.001

r = -0.796

P = 0.006

r= -0.658

P = 0.039

1.000

r = 0.951

P < 0.001

r = -0.776

P = 0.008

r= -0.633

P = 0.049

1.000

r = -0.863

P = 0.001

r= -0.744

P = 0.014

1.000

r = -0.920

P < 0.001

1.000

Conclusions

• Optimal growth performance and nutrient utilisation in broiler chickens can be predicted by contour plot biometrics

• The predicted optimal FCR 1.486 g/g was achieved when the proportions of diets based on Block I, HP and Liberty equal to 0.0%, 55.6% and 44.4%, respectively.

Acknowledgements