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Broiler Response to Energy or Energy and Protein Dilution in the Finisher Diet
Broiler Response to Energy or Energy and Protein Dilution in the Finisher Diet S. LEESON, L. CASTON, and J. D. SUMMERS Department of Animal and Poultry Science, University of Guelph, Guelph, Ontario, Canada, NIG 2W1 although energy intake was not maintained (P < 0.01). Diet energy dilution generally had little effect on carcass weight or yield of breast meat, although there was less abdominal fat (P < 0.01). In Experiment 2, dilution of both energy and protein had a comparable effect on growth rate as described in Experiment 1; however, in this study there was a linear decrease in carcass weight and breast meat yield as the diet was diluted. These results suggest that the male broiler chicken can grow quite well on very low energy diets but that a period of at least 7 d is required for adjustment to feed intake. Even with compensatory increase in feed intake, however, the bird is unable to maintain its energy intake when fed such diluted diets.
(Key zvords: broiler, energy, protein, diet dilution, carcass composition) 1996 Poultry Science 75:522-528
INTRODUCTION Increased growth rate of the broiler chicken is achieved by concomitant increase in feed intake. Few animals are able to consume feed at the rate exhibited by the broiler chicken, which can have a daily intake as high as 10% of body weight on a dry matter basis. Nutritionists are faced with the problem of accommodating this voracious appetite with modification to the diet nutrient profile so as to achieve desired growth and carcass characteristics. In addition to optimizing growth rate and feed utilization, there is also an ongoing demand to maximize growth of lean tissue and to minimize development of excess accumulation of body and carcass fat. As the broiler chicken gets older, its carcass is composed of progressively less protein and more fat (Perrault and Leeson, 1992). Because carcass fat deposition can be altered through modifying the energy intake of the broiler (Summers and Leeson, 1984) there seems to be some potential to control fat deposition through limiting energy intake. In previous studies, we have shown that diet dilution and physical feed restriction of older broilers can be used to reduce carcass fatness, but
that carcass weight is adversely affected (Leeson et ah, 1992). Leeson et al. (1992) assumed that the broiler could not physically eat more feed than occurs normally, and that diet dilution would then result in reduced energy intake. Such diluted diets did result in reduced energy intake, although there was still remarkably increased feed intake by these birds. Birds fed such diluted diets necessarily consume variable quantities of all nutrients, and so results may be related to deficiencies, excesses, or imbalances of nutrients other than energy or protein. The current studies were designed to study the broiler's response to diet dilution, where only energy or energy and protein (amino acid) components of the diet were affected.
MATERIALS AND METHODS Experiment 1 Six hundred 1-d-old male broiler chickens of a commercial strain were wing-banded and randomly allocated to one of six treatment groups each replicated four times. Birds were placed into pens measuring 2.44 x 1.83 m, 25 birds per pen. Combinations of treatment and replicate were allocated to one of two rooms maintained identically and each room contained two replicates from each treatment group. Temperature was maintained at 32.5 C for 5 d and gradually reduced in keeping with usual
Received for publication August 7, 1995. Accepted for publication November 29, 1995.
522
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ABSTRACT Two experiments were carried out with male broiler chickens in which diets from 35 to 49 d of age were diluted by oat hulls and sand. In one experiment only energy was diluted; in the second experiment, both energy and protein (amino acid) levels were affected. Each diet was tested with four replicate floor pens each containing 25 1-d-old birds. All birds received a standard starter diet to 16 d and then grower diet to 35 d. In Experiment 1, dilution of only energy resulted in a significant linear (P < 0.01) reduction in body weight at 42 d, although there was growth compensation after this time such that all birds weighed the same at 49 d. Diet energy dilution resulted in increased feed intake,
523
BROILER DIET ENERGY DILUTION TABLE 1. Percentage composition of starter and grower diets Ingredients
Starter
Grower
(%) Corn Soybean meal (48% CP) Limestone Calcium phosphate (20% P) Fat, animal-vegetable blend Iodized salt, 0.015% KI Vitamin-mineral premix 1 DL-methionine Stafac® Coban® Calculated nutrient content CP Energy, kcal ME/kg Calcium Available P Methionine Lysine
61.07 30.70 1.50 1.50 4.00 0.30 0.75 0.06 0.05 0.075
56.48 35.64 1.50 1.50 3.63 0.30 0.75 0.08 0.05 0.075 22.0 3,072 0.96 0.42 0.44 1.25
20.0 3,127 0.95 0.42 0.40 1.10
brooding practice. All birds received the same starter diet (Table 1, Diet 1) to 16 d of age, at which time the grower diet was introduced and fed until 35 d (Table 1, Diet 2). On Day 35, all birds were weighed individually and an average for each pen computed. Bird numbers per pen were reduced to 20 and mean pen body weight equalized (± 10 g). Diet treatment was applied at this time. Six finisher diets were formulated such that Treatment 1 birds
Experiment 2 Six hundred 1-d-old male broiler chickens were wingbanded, allocated to one of six treatment groups, each replicated four times, brooded, and at 35 d bird numbers per pen were reduced in the same manner as described in Experiment 1. The same starter and grower diets as used in Experiment 1 were fed to these treatment groups for the same time periods (Diets 1 and 2, Table 1). On Day 35, bird numbers were reduced to 20 per pen and the designated treatment groups were offered one of six diets (Diets 1 to 6, Table 3). Diet 1 was a standard broiler finisher, whereas Diets 2 through 6 involved 10 to 50% dilution of both energy and protein. This dilution was accomplished by
TABLE 2. Percentage composition of finisher diets with energy dilution, Experiment 1 Diet Ingredients
1
2
4
3
6
5
10/ \
Corn Soybean meal (48% CP) Limestone Calcium phosphate (20% P) Fat, animal-vegetable blend Iodized salt, 0.015% KI Oat hulls Sand Vitamin-mineral premix 1 DL-Methionine L-Lysine Calculated nutrient content CP Energy, kcal ME/kg Crude fat Calcium Available P Methionine Lysine
65.05 25.80 1.50 1.50 5.02 0.30 0.75 0.08
18.0 3,212 7.62 0.94 0.41 0.39 0.96
58.54 25.80 1.50 1.50 4.50 0.30 3.50 3.50 0.75 0.09 0.02
52.01 25.80 1.50 1.50 4.00 0.30 7.00 7.00 0.75 0.11 0.03
17.5 2,955 6.85 0.94 0.40 0.39 0.96
17.0 2,700 6.11 0.94 0.40 0.39 0.95
\'u)
45.49 25.80 1.50 1.50 3.50 0.30 10.50 10.50 0.75 0.12 0.04
38.96 25.80 1.50 1.50 3.00 0.30 14.00 14.00 0.75 0.13 0.06
32.43 25.80 1.50 1.50 2.50 0.30 17.50 17.50 0.75 0.14 0.08
16.4 2,450 5.36 0.94 0.39 0.39 0.95
16.0 2,200 4.61 0.94 0.39 0.39 0.95
15.3 1,950 3.86 0.94 0.39 0.39 0.95
Provided per kilogram of diet; vitamin A, 8,000 IU (retinyl palmitate); cholecalciferol, 40 /tg; vitamin E, 11 IU (dl-a-tocopherol acetate); riboflavin, 9.0 mg; biotin, 0.25 mg; pantothenic acid, 11.0 mg; vitamin B 12 ,13 mg; niacin, 26 mg; choline, 900 mg; vitamin K, 1.5 mg; folic acid, 1.5 mg; ethoxyquin, 125 mg; manganese, 55 mg; zinc, 50 mg; copper, 5 mg; iron, 30 mg; and selenium, 0.1 mg.
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Provided per kilogram of diet; vitamin A, 8,000 IU (retinyl palmitate); cholecalciferol, 40 jig; vitamin E, 11 IU (dl-a-tocopherol acetate); riboflavin, 9.0 mg; biotin, 0.25 mg; pantothenic acid, 11.0 mg; vitamin B12, 13 mg; niacin, 26 mg; choline, 900 mg; vitamin K, 1.5 mg; folic acid, 1.5 mg; ethoxyquin, 125 mg; manganese, 55 mg; zinc, 50 mg; copper, 5 mg; iron, 30 mg; and selenium, 0.1 mg.
received a standard broiler finisher and birds in Treatments 2 through 6 received diets of increasing energy dilution accomplished by increasing the percentage of oat hulls and sand in the diet; each diet was reduced by approximately 250 kcal M E / k g (Table 2, Diets 2 to 6, respectively). Protein levels were reduced slightly, although methionine and lysine levels were held constant by addition of synthetic sources. All diets were available for ad libitum consumption. On Day 42, all birds were weighed individually and 10 birds randomly selected for processing at the University's plant. After processing, the abdominal fat pad was removed and weighed according to the method of Griffiths et al. (1977). Carcasses were chilled for 1 h, weighed, and the breast meat on both left and right side of the carcass, consisting of the Pectoralis and Supracoracoideus muscles, dissected and weighed. On Day 49, the remaining birds were weighed and processed in the same manner.
524
LEESON ET AL. TABLE 3. Percentage composition of finisher diet with energy and protein dilution, Experiment 2 Diet
Ingredients
1
2
4
3
6
5
(o,\
0.75 0.08
58.55 23.20 1.50 1.50 4.52 0.30 4.80 4.80 0.75 0.08
52.04 20.64 1.50 1.60 4.02 0.30 9.54 9.54 0.75 0.07
45.54 18.06 1.50 1.65 3.51 0.35 14.29 14.29 0.75 0.06
39.02 15.48 1.50 1.70 3.01 0.35 19.07 19.07 0.75 0.05
32.52 12.90 1.50 1.75 2.51 0.35 23.84 23.84 0.75 0.04
18.0 3,210 0.94 0.41 0.39 0.96
16.2 2,890 0.94 0.40 0.36 0.86
14.4 2,570 0.95 0.41 0.32 0.76
12.6 2,250 0.96 0.41 0.28 0.67
10.8 1,925 0.96 0.41 0.24 0.57
9.0 1,605 0.97 0.40 0.20 0.48
65.05 25.80 1.50 1.50 5.02 0.30
Provided per kilogram of diet; vitamin A, 8,000 IU (retinyl palmitate); cholecalciferol, 40 fig; vitamin E, 11IU (dl-a-tocopherol acetate); riboflavin, 9.0 mg; biotin, 0.25 mg; pantothenic acid, 11.0 mg; vitamin B 12 ,13 mg; niacin, 26 mg; choline, 900 mg; vitamin K, 1.5 mg; folic acid, 1.5 mg; ethoxyquin, 125 mg; manganese, 55 mg; zinc, 50 mg; copper, 5 mg; iron, 30 mg; and selenium, 0.1 mg.
substitution of all major ingredients for a 50:50 (wt/wt) mixture of sand and oat hulls. Calcium, phosphorus, and trace nutrient levels were not affected. Birds were weighed at 42 d and 10 birds per pen removed for processing as described for Experiment 1. Remaining birds were weighed and processed at 49 d.
significant factor in the regression model and was, therefore, removed.
Statistical
Dilution of the energy content of the diet resulted in a significant (P < 0.01) linear reduction in body weight at 42 d, although the maximum growth depression was only about 4% (Table 4). Body weight at 49 d was unaffected by diet treatment. During the 1st wk of diet energy dilution there was a linear (P < 0.01) decrease in body weight gain, although from 42 to 49 d body weight gain was not statistically different and, in fact, there was numerically greater growth for birds subjected to the highest degree of diet dilution. This apparent growth compensation for
Analysis
Both experiments were arranged as completely randomized designs with pen as the experimental unit (Cochran and Cox, 1957). Data for response variables in terms of growth parameters and carcass characteristics were examined using a linear regression model (SAS Institute, 1990). A quadratic relationship was ruled out by its nonsignificance. Because conditions in each room were maintained as equally as possible, room was not a
RESULTS Experiment
1
TABLE 4. Effect of energy dilution of finisher diet on growth of broilers, Experiment 1 Diet treatment Percentage dilution
Body weight ME
(kcal/kg) 0 3,200 8 2,950 16 2,700 24 2,450 32 2,200 40 1,950 Regression analysis CV R2
42 d
49 d
Body weight gaini 35 to 42 d
42 to 49 d
35 to 49 d
612 603 599 582 699 669 NS 12.6 0.11
1,179 1,177 1,170 1,094 1,214 1,134 NS 6.9 0.01
lr\
\b>
2,370 2,395 2,371 2,331 2,323 2,277
*• 1.5 0.52
'Significant linear effect (P < 0.01).
2,982 2,998 2,970 2,913 3,022 2,946 NS 2.8 0.01
567 574 571 512 515 465
** 6.6 0.53
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Corn Soybean meal (48% CP) Limestone Calcium phosphate (20% P) Fat, animal-vegetable blend Iodized salt, 0.015% KI Oat hulls Sand Vitamin-mineral premix 1 DL-methionine Calculated nutrient content CP Energy, kcal ME/kg Calcium Available P Methionine Lysine
BROILER DIET ENERGY DILUTION
525
TABLE 5. Effect of energy dilution of finisher diet on feed intake and feed efficiency of broilers, Experiment 1 Diet treatment
Energy intake
Feed intake
Percentage dilution
ME
(%)
(kcal/kg)
35 to 42 d
42 to 49 d
35 to 49 d
fWhirrll
0 3,200 8 2,950 16 2,700 24 2,450 32 2,200 40 1,950 Regression analysis CV R2
1,250 1,301 1,377 1,371 1,444 1,482
1,373 1,401 1,456 1,585 1,677 1,946
3.0 0.79
9.4 0.63
35 to 49 d •
2,623 2,702 2,833 2,956 3,121 3,427
Feed intake:body we ight gain 42 to 49 d
35 to 49 d
h—1
(Meal) 8,429 7,988 7,655 7,237 6,847 6,649
5.0 0.78
35 to 42 d
(&-S>
2.26 2.33 2.44 2.73 2.45 2.93
2.21 2.27 2.42 2.69 2.82 3.20
4.5 0.78
2.23 2.30 2.43 2.70 2.59 3.03
11.1
7.3
6.7 0.35
0.78
0.70
"Significant linear effect (P < 0.01).
abdominal fat were significantly (P < 0.01) reduced by decreasing the energy level of the finisher diet (Table 6).
Experiment 2 Dilution of both protein and energy in the diet caused reduced body weight at 42 d (P < 0.01), although there was no significant effect at 49 d (Table 7). During the 1st wk of treatment there was a linear (P < 0.01) reduction in weight gain as the diet was diluted, although after this time the birds seemed to adapt such that energy and protein dilution actually resulted in a highly significant (P < 0.01) increase in weight gain from 42 to 49 d (Table 7). This change in pattern of growth over time resulted in no significant effect (P > 0.05) on overall 35 to 49 d body weight gain. There was a linear increase in feed intake in response to diet nutrient dilution. From 35 to 42 d, the most extreme diet dilution resulted in a 31% increase in feed intake,
TABLE 6. Effect of energy dilution of finisher diet on carcass characteristics of broilers, Experiment 1 Diet treatment Percentage dilution
(%)
Carcass weight ME
(kcal/kg) 0 3,200 8 2,950 16 2,700 24 2,450 32 2,200 40 1,950 Regression analysis CV R2
42 d
(g)
(% LW)
1,675 1,686 1,711 1,701 1,680 1,655 NS 2.4
70.7 70.4 72.2 72.9 72.3 72.7 if
2.2
0.03 0.22
'Significant linear effect (P < 0.05). "Significant linear effect (P < 0.01). ^iveweight. 2 Carcass weight.
42 d
49 d 1
(g) 2,205 2,215 2,173 2,130 2,184 2,164 NS 2.9
Abdominal fat •weight
Breast weight
(% LW)i 73.9 73.9 73.2 73.1 72.3 73.5 NS 1.5
0.07 0.10
(g) 328 332 331 336 331 323
(% CW) 19.6 19.7 19.4 19.8 19.7 19.5
NS NS 3.6> 2.5 O.C1 0.00 1
42 d
49 d 2
(g) (% CW) 417 19.6 425 19.2 426 19.6 416 19.5 436 19.7 418 19.3 NS NS 4.4: 3.1 0.01 0 0.11
49 d
(% CW) 3.0 2.8 2.8 2.7 2.7 2.4
(g)
(% CW)
50 48 48 45 45 40
70 73 64 63 60 57
3.2 3.3 2.9 3.0 2.8 2.7
44
44
4*
44
(g)
8.3 9.1
8.3! 8.2
0.35 0.28
0.48 0.43
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birds fed the heavily diluted diet from 42 to 49 d resulted in no significant (P > 0.05) differences in weight gain throughout the 35 to 49 d growth period (Table 4). As expected, there was a significant (P < 0.01) linear increase in feed intake at all age periods, in response to diet energy dilution (Table 5). However the increase in feed intake was not sufficient to maintain energy intake, and over the 35 to 49 d period, diet energy dilution resulted in a significant (P < 0.01) linear decline in energy intake. For the most extreme treatment this was a 21% reduction in energy intake (Table 5). Diet energy dilution caused a significant (P < 0.01) increase in feed intake:body weight gain (Table 5). Carcass weights at 42 and 49 d were not affected by diet treatment (Table 6), although at 42 d there was a linear (P < 0.05) increase in carcass yield as a proportion of live weight, in response to increased energy dilution. Breast weight characteristics were not affected by diet dilution although the absolute and proportional quantities of
526
LEESON ET AL. TABLE 7. Effect of dilution of energy and protein in the finisher diet on growth of broilers, Experiment 2 Diet treatment
Percentage dilution
Body weight gain
Body weight ME
CP
42 d
49 d
35 to 42 d
(%)
(%)
(kcal/kg) 3,210 0 2,890 10 2,570 20 2,250 30 1,925 40 1,605 50 Regression analys is CV
42 to 49 d
35 to 49 d
527 554 559 650 742 674
1,107 1,110 1,071 1,098 1,112 1,077 NS 6.8 0.01
i>1
18.0 16.2 14.4 12.6 10.8 9.0
2,420 2,367 2,320 2,263 2,170 2,218
** 3.54 0.52
R2
580 556 511 448 370 404
2,948 2,921 2,879 2,913 2,913 2,892 NS 2.38 0.04
\b>
**
**
16.9 0.47
10.7 0.54
"Significant linear effect (P < 0.01).
DISCUSSION In previous studies, Leeson et al. (1992) showed that total diet dilution of up to 50% in the finisher period resulted in only a minor reduction in weight gain of male broilers. Because such diet dilution affected feed intake, there were variable intakes of calcium, phosphorus, salt, and micronutrients. Certainly in this earlier study, total diet dilution resulted in less dry matter in the excreta; the role of variable mineral intake was a suspected cause, and its potential effect on gut transit
time and overall diet digestibility was unknown. In the present studies, only diet energy or energy and protein components were affected, thus removing the potentially confounding effect of variable mineral intake. Diluting out only energy had an initial depressing effect on growth, although birds adapted rapidly during the 2nd wk of treatment (Table 4). This adaptation seems to relate to dramatically increased feed intake from 42 to 49 d (Table 5). Presumably the increased feed intake is caused by the bird's attempt at maintaining a normal energy intake, but even with a linear increase in feed intake in response to energy dilution, there was a linear decline in energy intake. Jackson et al. (1982) also indicated that male broiler chickens were unable to maintain a constant intake of energy when fed diets of lower energy content, even though feed intake was increased as seen in the current study. Summers and Leeson (1984) showed a comparable effect on energy intake when broilers were fed diets over the range 2,700 to 3,300 kcal ME/kg. Although energy intake was reduced in response to the reduced energy level of the diet, and although this reduction in energy intake was associated with no change in body weight, the birds fed lower energy diets were much more efficient in
TABLE 8. Effect of dilution of energy and protein in the finisher diet on feed intake and feed efficiency in broilers, Experiment 2 Diet treatment Percentage dilution
(%)
ME
(kcal/kg) 0 3,210 10 2,890 20 2,570 30 2,250 40 1,925 50 1,605 Regression analysis CV
Energy intake
Feed intake CP
35 to 49 d
35 to 49 d
35 to 42 d
42 to 49 d
1,299 1,445 1,517 1,844 2,201 2,610
2,583 2,763 2,904 3,273 3,673 4,295
(Meal) 8,299 7,991 7,466 7,361 7,082 6,902
2.22 2.42 2.72 3.24 4.04 4.63
O-r-1 \b-bl 2.48 2.64 2.73 2.85 2.96 3.89
**
**
»»
35 to 42 d
42 to 49 d
1,284 1,318 1,387 1,429 1,472 1,685
**
(~
(%) 18.0 16.2 14.4 12.6 10.8 9.0
R2
'Significant linear effect (P < 0.01).
IV.\rA\
V6i Dira; •
6.6 0.65
Feed intake :body weight gain
8.1 0.91
6.2 0.90
4.2 0.72
35 to 49 d 2.34 2.49 2.72 2.99 3.31 4.01
**
**
**
22.3 0.60
11.1 0.60
7.9 0.85
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whereas from 42 to 49 d, there was a dramatic 100% increase in intake (Table 8). However even this degree of feed intake adjustment was not adequate to maintain energy intake (Table 8). Diet energy and protein dilution resulted in a significant increase in feed intake:body weight gain (P < 0.01). At both 42 and 49 d of age, there was a linear decrease in weight of the carcass, breast meat, and abdominal fat pad (Table 9). Breast weight as a proportion of carcass weight was not affected (P > 0.05) although diet dilution did result in proportionally less abdominal fat at 42 d (P < 0.05).
BROILER DIET
ENERGY DILUTION
527
diet on carcass characteristics of broilers, Experiment 2
TABLE 9. Effect of dilution of energy and protein in the Diet treatment Percentage dilution
ME
CP
(%) (kcal/kg)(%) 0 3,210 18.0 10 2,890 16.2 20 2,570 14.4 30 2,250 12.6 40 1,925 10.8 50 1,605 9.0 Regression analysis CV R2
Breast weight
Carcass weight 42 d 49 d (g) (% LW)i 1,775 73.3 1,719 72.6 1,678 72.3 1,654 73.1 1,588 73.2 1,540 69.7 ** NS 2.4 3.1 0.80 0.12
(g) (% LW)1 2,184 74.1 2,107 72.1 2,063 71.6 2,088 71.4 2,073 71.2 2,038 70.5 ** ** 2.5 1.7 0.39 0.44
42 d (g) 326 320 305 305 295 285
(% C W ) 2 18.3 18.6 18.1 18.4 18.5 18.5
NS 3.5 1.8 0.63 0.02
Abdominal fat weight
49 d
(g) 418 404 400 402 390 378 * 4.2
(% CW) 19.1 19.1 19.4 19.3 18.8 18.6
NS 3.5
0.34 0.08
42 d
(g) 53 52 49 46 45 42 * 7.1
49 d
(% CW) (g) (% L 3.1 69 3.0 74 3.5 3.0 68 3.3 2.9 64 3.1 2.8 67 3.2 2.8 60 2.9 2.7 * * NS 10.3 10.3 7.3
0.59 0.19
0.21 0.10
"Significant linear effect (P < 0.05). "Significant linear effect (P < 0.01). ^iveweight. 2 Carcass weight.
In both experiments, broilers were slow in adapting to diet dilution. In the first 7 d of study, growth rate declined because birds ate less protein or energy. Compensation is seen in body weight gain from 42 to 49 d, although such effects were significant (P < 0.05) in only one study. Savory and Gentle (1976a), in studying the feeding pattern of quail fed diets diluted with 20% fiber, showed that "normalization" of energy intake took some 8 to 10 d. In this study with quail, birds were able to normalize their nutrient intake, although growth rate was not maintained. Data from Savory and Gentle
(1976a) suggest that diet dilution with fiber in some way influenced energy partitioning. It is possible that dilution of diets with fiber alters diet digestibility or influences retained energy directed to growth. Savory and Gentle (1976b) measured ME of their diluted quail diets and showed that the reduction in ME was as expected in relation to fiber inclusion. This result suggests that fiber yer se had no effect on utilization of other feed components. Hakansson (1978) also suggested that sudden changes in diet energy had no unexpected effect on diet ME, and that there was virtually no lag time in such adjustment. Fiber per se may also influence rate of feed passage through the digestive tract, and this has previously been discussed in relation to influencing digestibility or absorption of nutrients. For example, Sibbald (1979) suggests that with the force-feeding technique, increased feed intake causes increased rate of passage of excreta. However, it must be remembered that these levels of intake used in the TME bioassay are at or near maintenance, whereas the intakes discussed in the current work are at the extreme of maximum physical feed intake. Tuckey et al. (1958) also suggest that dilution of a diet with fiber (oat hulls) has no effect on rate of passage of digesta. Washburn (1991) showed no relationship between rate of feed passage and feed efficiency in broilers. Reduced growth rate with diluted diets more likely relates to differential partitioning of retained energy. Broilers fed diluted diets consume much more feed and this means that birds must expend more energy in eating and in travelling to feeders. Working with laying hens van Kampen (1976) suggested that the physical act of eating represented about 3% of daily heat production. Because the broiler chicken normally eats proportionally more feed than does the Leghorn, this value is expected to be higher for broilers, and particularly so when feed intake is increased even further by diet dilution. These data suggest that broiler chickens are not eating to near physical capacity, and that when confronted
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converting energy to body weight gain. For example, birds fed at 3,200 kcal/kg needed some 7.1 Mcal/kg gain, whereas for birds fed 1,950 kcal/kg, the efficiency was increased to just 5.9 Mcal/kg. At the same time, however, as energy efficiency was increasing, there was reduction in efficiency of protein used per unit of weight gain. Because there was no major dilution of protein or amino acids in Experiment 1, it is perhaps not too surprising that neither growth rate nor breast weight were affected by diet dilution. Thus, when energy level was reduced, birds would consume much more protein because feed intake was increased. In Experiment 2, when both energy and protein were diluted, birds were not able to maintain constant intakes of either energy or protein. Under these dietary conditions, there was no significant effect on 49-d body weight, because again there was an apparent adaptation to these diluted diets from 42 to 49 d. However, the more sensitive variable of carcass weight and breast weight did show a significant linear decrease in response to diet dilution. The older broiler chicken, therefore, seems more sensitive to protein and amino acid intake than it does to energy intake alone. In both studies there was a decline in the quantity of abdominal fat as diet energy intake was voluntarily reduced. Jackson et al. (1982) and Summers and Leeson (1984) showed similar results for broilers fed a more narrow range of diet energy levels.
528
LEESON ET AL.
with diluted diets they are still capable of adaptation. Reducing the energy level of the finisher diet may have some application for older broilers, although the situation is confounded with a lag period of adaptation to physical intake, during which time feed and energy intake are inadequate and so there is reduced growth rate. Low energy finisher diets will reduce carcass fat content, although the overall picture of energy partitioning for growth vs maintenance needs more careful study.
ACKNOWLEDGMENT This work was supported by the Ontario Ministry of Agriculture, Food and Rural Affairs contract with the University of Guelph.
Cochran, W. G., and G. M. Cox, 1957. Experimental Design. 2nd ed. John Wiley and Sons, New York, NY. Griffiths, L., S. Leeson, and J. D. Summers, 1977. Fat deposition in broilers: Effect of dietary energy to protein balance and early life caloric restriction on productive performance and abdominal fat pad size. Poultry Sci. 56:638-646. Hakansson, J., 1978. Effect of feed energy level on growth and development of the digestive tract of chicks. Sveriges Lantbruksuniversitet. Report 44.
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REFERENCES
Jackson, S., J. D. Summers, and S. Leeson, 1982. The response of male broilers to varying levels of dietary protein and energy. Nutr. Rep. Int. 25:601-606. Leeson, S., J. D. Summers, and L. J. Caston, 1992. Response of broilers to feed restriction or diet dilution in the finisher period. Poultry Sci. 71:2056-2064. Perrault, N., and S. Leeson, 1992. Age-related carcass composition changes in male broiler chickens. Can. J. Anim. Sci. 72: 919-929. SAS Institute, 1990. SAS/STAT® User's Guide. Vol. 2. Version 6. 4th ed. SAS Institute Inc., Cary, NC. Savory, C. J., and M. J. Gentle, 1976a. Effects of dietary dilution with fibre on the food intake and gut dimensions of Japanese quail. Br. Poult. Sci. 17:561-570. Savory, C. J., and M. J. Gentle, 1976. Changes in food intake and gut size in Japanese quail in response to manipulation of dietary fibre content. Br. Poult. Sci. 17:571-580. Sibbald, I. R., 1979. Passage of feed through the adult rooster. Poultry Sci. 58:446^59. Summers, J. D., and S. Leeson, 1984. Influence of dietary protein and energy level on broiler performance and carcass composition. Nutr. Rep. Int. 29:757-767. Tuckey, R., B. E. March, and J. Biely, 1958. Diet and rate of food passage in the gravious chick. Poultry Sci. 37: 786-792. van Kampen, M., 1976. Activity and energy expenditure in laying hens; the energy cost of eating and posture. J. Agric. Sci. Camb. 87:85-88. Washburn, K. W., 1991. Efficiency of feed utilization and rate of feed passage through the digestive system. Poultry Sci. 70:447-452.
(Key zvords: broiler, energy, protein, diet dilution, carcass composition) 1996 Poultry Science 75:522-528
INTRODUCTION Increased growth rate of the broiler chicken is achieved by concomitant increase in feed intake. Few animals are able to consume feed at the rate exhibited by the broiler chicken, which can have a daily intake as high as 10% of body weight on a dry matter basis. Nutritionists are faced with the problem of accommodating this voracious appetite with modification to the diet nutrient profile so as to achieve desired growth and carcass characteristics. In addition to optimizing growth rate and feed utilization, there is also an ongoing demand to maximize growth of lean tissue and to minimize development of excess accumulation of body and carcass fat. As the broiler chicken gets older, its carcass is composed of progressively less protein and more fat (Perrault and Leeson, 1992). Because carcass fat deposition can be altered through modifying the energy intake of the broiler (Summers and Leeson, 1984) there seems to be some potential to control fat deposition through limiting energy intake. In previous studies, we have shown that diet dilution and physical feed restriction of older broilers can be used to reduce carcass fatness, but
that carcass weight is adversely affected (Leeson et ah, 1992). Leeson et al. (1992) assumed that the broiler could not physically eat more feed than occurs normally, and that diet dilution would then result in reduced energy intake. Such diluted diets did result in reduced energy intake, although there was still remarkably increased feed intake by these birds. Birds fed such diluted diets necessarily consume variable quantities of all nutrients, and so results may be related to deficiencies, excesses, or imbalances of nutrients other than energy or protein. The current studies were designed to study the broiler's response to diet dilution, where only energy or energy and protein (amino acid) components of the diet were affected.
MATERIALS AND METHODS Experiment 1 Six hundred 1-d-old male broiler chickens of a commercial strain were wing-banded and randomly allocated to one of six treatment groups each replicated four times. Birds were placed into pens measuring 2.44 x 1.83 m, 25 birds per pen. Combinations of treatment and replicate were allocated to one of two rooms maintained identically and each room contained two replicates from each treatment group. Temperature was maintained at 32.5 C for 5 d and gradually reduced in keeping with usual
Received for publication August 7, 1995. Accepted for publication November 29, 1995.
522
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ABSTRACT Two experiments were carried out with male broiler chickens in which diets from 35 to 49 d of age were diluted by oat hulls and sand. In one experiment only energy was diluted; in the second experiment, both energy and protein (amino acid) levels were affected. Each diet was tested with four replicate floor pens each containing 25 1-d-old birds. All birds received a standard starter diet to 16 d and then grower diet to 35 d. In Experiment 1, dilution of only energy resulted in a significant linear (P < 0.01) reduction in body weight at 42 d, although there was growth compensation after this time such that all birds weighed the same at 49 d. Diet energy dilution resulted in increased feed intake,
523
BROILER DIET ENERGY DILUTION TABLE 1. Percentage composition of starter and grower diets Ingredients
Starter
Grower
(%) Corn Soybean meal (48% CP) Limestone Calcium phosphate (20% P) Fat, animal-vegetable blend Iodized salt, 0.015% KI Vitamin-mineral premix 1 DL-methionine Stafac® Coban® Calculated nutrient content CP Energy, kcal ME/kg Calcium Available P Methionine Lysine
61.07 30.70 1.50 1.50 4.00 0.30 0.75 0.06 0.05 0.075
56.48 35.64 1.50 1.50 3.63 0.30 0.75 0.08 0.05 0.075 22.0 3,072 0.96 0.42 0.44 1.25
20.0 3,127 0.95 0.42 0.40 1.10
brooding practice. All birds received the same starter diet (Table 1, Diet 1) to 16 d of age, at which time the grower diet was introduced and fed until 35 d (Table 1, Diet 2). On Day 35, all birds were weighed individually and an average for each pen computed. Bird numbers per pen were reduced to 20 and mean pen body weight equalized (± 10 g). Diet treatment was applied at this time. Six finisher diets were formulated such that Treatment 1 birds
Experiment 2 Six hundred 1-d-old male broiler chickens were wingbanded, allocated to one of six treatment groups, each replicated four times, brooded, and at 35 d bird numbers per pen were reduced in the same manner as described in Experiment 1. The same starter and grower diets as used in Experiment 1 were fed to these treatment groups for the same time periods (Diets 1 and 2, Table 1). On Day 35, bird numbers were reduced to 20 per pen and the designated treatment groups were offered one of six diets (Diets 1 to 6, Table 3). Diet 1 was a standard broiler finisher, whereas Diets 2 through 6 involved 10 to 50% dilution of both energy and protein. This dilution was accomplished by
TABLE 2. Percentage composition of finisher diets with energy dilution, Experiment 1 Diet Ingredients
1
2
4
3
6
5
10/ \
Corn Soybean meal (48% CP) Limestone Calcium phosphate (20% P) Fat, animal-vegetable blend Iodized salt, 0.015% KI Oat hulls Sand Vitamin-mineral premix 1 DL-Methionine L-Lysine Calculated nutrient content CP Energy, kcal ME/kg Crude fat Calcium Available P Methionine Lysine
65.05 25.80 1.50 1.50 5.02 0.30 0.75 0.08
18.0 3,212 7.62 0.94 0.41 0.39 0.96
58.54 25.80 1.50 1.50 4.50 0.30 3.50 3.50 0.75 0.09 0.02
52.01 25.80 1.50 1.50 4.00 0.30 7.00 7.00 0.75 0.11 0.03
17.5 2,955 6.85 0.94 0.40 0.39 0.96
17.0 2,700 6.11 0.94 0.40 0.39 0.95
\'u)
45.49 25.80 1.50 1.50 3.50 0.30 10.50 10.50 0.75 0.12 0.04
38.96 25.80 1.50 1.50 3.00 0.30 14.00 14.00 0.75 0.13 0.06
32.43 25.80 1.50 1.50 2.50 0.30 17.50 17.50 0.75 0.14 0.08
16.4 2,450 5.36 0.94 0.39 0.39 0.95
16.0 2,200 4.61 0.94 0.39 0.39 0.95
15.3 1,950 3.86 0.94 0.39 0.39 0.95
Provided per kilogram of diet; vitamin A, 8,000 IU (retinyl palmitate); cholecalciferol, 40 /tg; vitamin E, 11 IU (dl-a-tocopherol acetate); riboflavin, 9.0 mg; biotin, 0.25 mg; pantothenic acid, 11.0 mg; vitamin B 12 ,13 mg; niacin, 26 mg; choline, 900 mg; vitamin K, 1.5 mg; folic acid, 1.5 mg; ethoxyquin, 125 mg; manganese, 55 mg; zinc, 50 mg; copper, 5 mg; iron, 30 mg; and selenium, 0.1 mg.
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Provided per kilogram of diet; vitamin A, 8,000 IU (retinyl palmitate); cholecalciferol, 40 jig; vitamin E, 11 IU (dl-a-tocopherol acetate); riboflavin, 9.0 mg; biotin, 0.25 mg; pantothenic acid, 11.0 mg; vitamin B12, 13 mg; niacin, 26 mg; choline, 900 mg; vitamin K, 1.5 mg; folic acid, 1.5 mg; ethoxyquin, 125 mg; manganese, 55 mg; zinc, 50 mg; copper, 5 mg; iron, 30 mg; and selenium, 0.1 mg.
received a standard broiler finisher and birds in Treatments 2 through 6 received diets of increasing energy dilution accomplished by increasing the percentage of oat hulls and sand in the diet; each diet was reduced by approximately 250 kcal M E / k g (Table 2, Diets 2 to 6, respectively). Protein levels were reduced slightly, although methionine and lysine levels were held constant by addition of synthetic sources. All diets were available for ad libitum consumption. On Day 42, all birds were weighed individually and 10 birds randomly selected for processing at the University's plant. After processing, the abdominal fat pad was removed and weighed according to the method of Griffiths et al. (1977). Carcasses were chilled for 1 h, weighed, and the breast meat on both left and right side of the carcass, consisting of the Pectoralis and Supracoracoideus muscles, dissected and weighed. On Day 49, the remaining birds were weighed and processed in the same manner.
524
LEESON ET AL. TABLE 3. Percentage composition of finisher diet with energy and protein dilution, Experiment 2 Diet
Ingredients
1
2
4
3
6
5
(o,\
0.75 0.08
58.55 23.20 1.50 1.50 4.52 0.30 4.80 4.80 0.75 0.08
52.04 20.64 1.50 1.60 4.02 0.30 9.54 9.54 0.75 0.07
45.54 18.06 1.50 1.65 3.51 0.35 14.29 14.29 0.75 0.06
39.02 15.48 1.50 1.70 3.01 0.35 19.07 19.07 0.75 0.05
32.52 12.90 1.50 1.75 2.51 0.35 23.84 23.84 0.75 0.04
18.0 3,210 0.94 0.41 0.39 0.96
16.2 2,890 0.94 0.40 0.36 0.86
14.4 2,570 0.95 0.41 0.32 0.76
12.6 2,250 0.96 0.41 0.28 0.67
10.8 1,925 0.96 0.41 0.24 0.57
9.0 1,605 0.97 0.40 0.20 0.48
65.05 25.80 1.50 1.50 5.02 0.30
Provided per kilogram of diet; vitamin A, 8,000 IU (retinyl palmitate); cholecalciferol, 40 fig; vitamin E, 11IU (dl-a-tocopherol acetate); riboflavin, 9.0 mg; biotin, 0.25 mg; pantothenic acid, 11.0 mg; vitamin B 12 ,13 mg; niacin, 26 mg; choline, 900 mg; vitamin K, 1.5 mg; folic acid, 1.5 mg; ethoxyquin, 125 mg; manganese, 55 mg; zinc, 50 mg; copper, 5 mg; iron, 30 mg; and selenium, 0.1 mg.
substitution of all major ingredients for a 50:50 (wt/wt) mixture of sand and oat hulls. Calcium, phosphorus, and trace nutrient levels were not affected. Birds were weighed at 42 d and 10 birds per pen removed for processing as described for Experiment 1. Remaining birds were weighed and processed at 49 d.
significant factor in the regression model and was, therefore, removed.
Statistical
Dilution of the energy content of the diet resulted in a significant (P < 0.01) linear reduction in body weight at 42 d, although the maximum growth depression was only about 4% (Table 4). Body weight at 49 d was unaffected by diet treatment. During the 1st wk of diet energy dilution there was a linear (P < 0.01) decrease in body weight gain, although from 42 to 49 d body weight gain was not statistically different and, in fact, there was numerically greater growth for birds subjected to the highest degree of diet dilution. This apparent growth compensation for
Analysis
Both experiments were arranged as completely randomized designs with pen as the experimental unit (Cochran and Cox, 1957). Data for response variables in terms of growth parameters and carcass characteristics were examined using a linear regression model (SAS Institute, 1990). A quadratic relationship was ruled out by its nonsignificance. Because conditions in each room were maintained as equally as possible, room was not a
RESULTS Experiment
1
TABLE 4. Effect of energy dilution of finisher diet on growth of broilers, Experiment 1 Diet treatment Percentage dilution
Body weight ME
(kcal/kg) 0 3,200 8 2,950 16 2,700 24 2,450 32 2,200 40 1,950 Regression analysis CV R2
42 d
49 d
Body weight gaini 35 to 42 d
42 to 49 d
35 to 49 d
612 603 599 582 699 669 NS 12.6 0.11
1,179 1,177 1,170 1,094 1,214 1,134 NS 6.9 0.01
lr\
\b>
2,370 2,395 2,371 2,331 2,323 2,277
*• 1.5 0.52
'Significant linear effect (P < 0.01).
2,982 2,998 2,970 2,913 3,022 2,946 NS 2.8 0.01
567 574 571 512 515 465
** 6.6 0.53
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Corn Soybean meal (48% CP) Limestone Calcium phosphate (20% P) Fat, animal-vegetable blend Iodized salt, 0.015% KI Oat hulls Sand Vitamin-mineral premix 1 DL-methionine Calculated nutrient content CP Energy, kcal ME/kg Calcium Available P Methionine Lysine
BROILER DIET ENERGY DILUTION
525
TABLE 5. Effect of energy dilution of finisher diet on feed intake and feed efficiency of broilers, Experiment 1 Diet treatment
Energy intake
Feed intake
Percentage dilution
ME
(%)
(kcal/kg)
35 to 42 d
42 to 49 d
35 to 49 d
fWhirrll
0 3,200 8 2,950 16 2,700 24 2,450 32 2,200 40 1,950 Regression analysis CV R2
1,250 1,301 1,377 1,371 1,444 1,482
1,373 1,401 1,456 1,585 1,677 1,946
3.0 0.79
9.4 0.63
35 to 49 d •
2,623 2,702 2,833 2,956 3,121 3,427
Feed intake:body we ight gain 42 to 49 d
35 to 49 d
h—1
(Meal) 8,429 7,988 7,655 7,237 6,847 6,649
5.0 0.78
35 to 42 d
(&-S>
2.26 2.33 2.44 2.73 2.45 2.93
2.21 2.27 2.42 2.69 2.82 3.20
4.5 0.78
2.23 2.30 2.43 2.70 2.59 3.03
11.1
7.3
6.7 0.35
0.78
0.70
"Significant linear effect (P < 0.01).
abdominal fat were significantly (P < 0.01) reduced by decreasing the energy level of the finisher diet (Table 6).
Experiment 2 Dilution of both protein and energy in the diet caused reduced body weight at 42 d (P < 0.01), although there was no significant effect at 49 d (Table 7). During the 1st wk of treatment there was a linear (P < 0.01) reduction in weight gain as the diet was diluted, although after this time the birds seemed to adapt such that energy and protein dilution actually resulted in a highly significant (P < 0.01) increase in weight gain from 42 to 49 d (Table 7). This change in pattern of growth over time resulted in no significant effect (P > 0.05) on overall 35 to 49 d body weight gain. There was a linear increase in feed intake in response to diet nutrient dilution. From 35 to 42 d, the most extreme diet dilution resulted in a 31% increase in feed intake,
TABLE 6. Effect of energy dilution of finisher diet on carcass characteristics of broilers, Experiment 1 Diet treatment Percentage dilution
(%)
Carcass weight ME
(kcal/kg) 0 3,200 8 2,950 16 2,700 24 2,450 32 2,200 40 1,950 Regression analysis CV R2
42 d
(g)
(% LW)
1,675 1,686 1,711 1,701 1,680 1,655 NS 2.4
70.7 70.4 72.2 72.9 72.3 72.7 if
2.2
0.03 0.22
'Significant linear effect (P < 0.05). "Significant linear effect (P < 0.01). ^iveweight. 2 Carcass weight.
42 d
49 d 1
(g) 2,205 2,215 2,173 2,130 2,184 2,164 NS 2.9
Abdominal fat •weight
Breast weight
(% LW)i 73.9 73.9 73.2 73.1 72.3 73.5 NS 1.5
0.07 0.10
(g) 328 332 331 336 331 323
(% CW) 19.6 19.7 19.4 19.8 19.7 19.5
NS NS 3.6> 2.5 O.C1 0.00 1
42 d
49 d 2
(g) (% CW) 417 19.6 425 19.2 426 19.6 416 19.5 436 19.7 418 19.3 NS NS 4.4: 3.1 0.01 0 0.11
49 d
(% CW) 3.0 2.8 2.8 2.7 2.7 2.4
(g)
(% CW)
50 48 48 45 45 40
70 73 64 63 60 57
3.2 3.3 2.9 3.0 2.8 2.7
44
44
4*
44
(g)
8.3 9.1
8.3! 8.2
0.35 0.28
0.48 0.43
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birds fed the heavily diluted diet from 42 to 49 d resulted in no significant (P > 0.05) differences in weight gain throughout the 35 to 49 d growth period (Table 4). As expected, there was a significant (P < 0.01) linear increase in feed intake at all age periods, in response to diet energy dilution (Table 5). However the increase in feed intake was not sufficient to maintain energy intake, and over the 35 to 49 d period, diet energy dilution resulted in a significant (P < 0.01) linear decline in energy intake. For the most extreme treatment this was a 21% reduction in energy intake (Table 5). Diet energy dilution caused a significant (P < 0.01) increase in feed intake:body weight gain (Table 5). Carcass weights at 42 and 49 d were not affected by diet treatment (Table 6), although at 42 d there was a linear (P < 0.05) increase in carcass yield as a proportion of live weight, in response to increased energy dilution. Breast weight characteristics were not affected by diet dilution although the absolute and proportional quantities of
526
LEESON ET AL. TABLE 7. Effect of dilution of energy and protein in the finisher diet on growth of broilers, Experiment 2 Diet treatment
Percentage dilution
Body weight gain
Body weight ME
CP
42 d
49 d
35 to 42 d
(%)
(%)
(kcal/kg) 3,210 0 2,890 10 2,570 20 2,250 30 1,925 40 1,605 50 Regression analys is CV
42 to 49 d
35 to 49 d
527 554 559 650 742 674
1,107 1,110 1,071 1,098 1,112 1,077 NS 6.8 0.01
i>1
18.0 16.2 14.4 12.6 10.8 9.0
2,420 2,367 2,320 2,263 2,170 2,218
** 3.54 0.52
R2
580 556 511 448 370 404
2,948 2,921 2,879 2,913 2,913 2,892 NS 2.38 0.04
\b>
**
**
16.9 0.47
10.7 0.54
"Significant linear effect (P < 0.01).
DISCUSSION In previous studies, Leeson et al. (1992) showed that total diet dilution of up to 50% in the finisher period resulted in only a minor reduction in weight gain of male broilers. Because such diet dilution affected feed intake, there were variable intakes of calcium, phosphorus, salt, and micronutrients. Certainly in this earlier study, total diet dilution resulted in less dry matter in the excreta; the role of variable mineral intake was a suspected cause, and its potential effect on gut transit
time and overall diet digestibility was unknown. In the present studies, only diet energy or energy and protein components were affected, thus removing the potentially confounding effect of variable mineral intake. Diluting out only energy had an initial depressing effect on growth, although birds adapted rapidly during the 2nd wk of treatment (Table 4). This adaptation seems to relate to dramatically increased feed intake from 42 to 49 d (Table 5). Presumably the increased feed intake is caused by the bird's attempt at maintaining a normal energy intake, but even with a linear increase in feed intake in response to energy dilution, there was a linear decline in energy intake. Jackson et al. (1982) also indicated that male broiler chickens were unable to maintain a constant intake of energy when fed diets of lower energy content, even though feed intake was increased as seen in the current study. Summers and Leeson (1984) showed a comparable effect on energy intake when broilers were fed diets over the range 2,700 to 3,300 kcal ME/kg. Although energy intake was reduced in response to the reduced energy level of the diet, and although this reduction in energy intake was associated with no change in body weight, the birds fed lower energy diets were much more efficient in
TABLE 8. Effect of dilution of energy and protein in the finisher diet on feed intake and feed efficiency in broilers, Experiment 2 Diet treatment Percentage dilution
(%)
ME
(kcal/kg) 0 3,210 10 2,890 20 2,570 30 2,250 40 1,925 50 1,605 Regression analysis CV
Energy intake
Feed intake CP
35 to 49 d
35 to 49 d
35 to 42 d
42 to 49 d
1,299 1,445 1,517 1,844 2,201 2,610
2,583 2,763 2,904 3,273 3,673 4,295
(Meal) 8,299 7,991 7,466 7,361 7,082 6,902
2.22 2.42 2.72 3.24 4.04 4.63
O-r-1 \b-bl 2.48 2.64 2.73 2.85 2.96 3.89
**
**
»»
35 to 42 d
42 to 49 d
1,284 1,318 1,387 1,429 1,472 1,685
**
(~
(%) 18.0 16.2 14.4 12.6 10.8 9.0
R2
'Significant linear effect (P < 0.01).
IV.\rA\
V6i Dira; •
6.6 0.65
Feed intake :body weight gain
8.1 0.91
6.2 0.90
4.2 0.72
35 to 49 d 2.34 2.49 2.72 2.99 3.31 4.01
**
**
**
22.3 0.60
11.1 0.60
7.9 0.85
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whereas from 42 to 49 d, there was a dramatic 100% increase in intake (Table 8). However even this degree of feed intake adjustment was not adequate to maintain energy intake (Table 8). Diet energy and protein dilution resulted in a significant increase in feed intake:body weight gain (P < 0.01). At both 42 and 49 d of age, there was a linear decrease in weight of the carcass, breast meat, and abdominal fat pad (Table 9). Breast weight as a proportion of carcass weight was not affected (P > 0.05) although diet dilution did result in proportionally less abdominal fat at 42 d (P < 0.05).
BROILER DIET
ENERGY DILUTION
527
diet on carcass characteristics of broilers, Experiment 2
TABLE 9. Effect of dilution of energy and protein in the Diet treatment Percentage dilution
ME
CP
(%) (kcal/kg)(%) 0 3,210 18.0 10 2,890 16.2 20 2,570 14.4 30 2,250 12.6 40 1,925 10.8 50 1,605 9.0 Regression analysis CV R2
Breast weight
Carcass weight 42 d 49 d (g) (% LW)i 1,775 73.3 1,719 72.6 1,678 72.3 1,654 73.1 1,588 73.2 1,540 69.7 ** NS 2.4 3.1 0.80 0.12
(g) (% LW)1 2,184 74.1 2,107 72.1 2,063 71.6 2,088 71.4 2,073 71.2 2,038 70.5 ** ** 2.5 1.7 0.39 0.44
42 d (g) 326 320 305 305 295 285
(% C W ) 2 18.3 18.6 18.1 18.4 18.5 18.5
NS 3.5 1.8 0.63 0.02
Abdominal fat weight
49 d
(g) 418 404 400 402 390 378 * 4.2
(% CW) 19.1 19.1 19.4 19.3 18.8 18.6
NS 3.5
0.34 0.08
42 d
(g) 53 52 49 46 45 42 * 7.1
49 d
(% CW) (g) (% L 3.1 69 3.0 74 3.5 3.0 68 3.3 2.9 64 3.1 2.8 67 3.2 2.8 60 2.9 2.7 * * NS 10.3 10.3 7.3
0.59 0.19
0.21 0.10
"Significant linear effect (P < 0.05). "Significant linear effect (P < 0.01). ^iveweight. 2 Carcass weight.
In both experiments, broilers were slow in adapting to diet dilution. In the first 7 d of study, growth rate declined because birds ate less protein or energy. Compensation is seen in body weight gain from 42 to 49 d, although such effects were significant (P < 0.05) in only one study. Savory and Gentle (1976a), in studying the feeding pattern of quail fed diets diluted with 20% fiber, showed that "normalization" of energy intake took some 8 to 10 d. In this study with quail, birds were able to normalize their nutrient intake, although growth rate was not maintained. Data from Savory and Gentle
(1976a) suggest that diet dilution with fiber in some way influenced energy partitioning. It is possible that dilution of diets with fiber alters diet digestibility or influences retained energy directed to growth. Savory and Gentle (1976b) measured ME of their diluted quail diets and showed that the reduction in ME was as expected in relation to fiber inclusion. This result suggests that fiber yer se had no effect on utilization of other feed components. Hakansson (1978) also suggested that sudden changes in diet energy had no unexpected effect on diet ME, and that there was virtually no lag time in such adjustment. Fiber per se may also influence rate of feed passage through the digestive tract, and this has previously been discussed in relation to influencing digestibility or absorption of nutrients. For example, Sibbald (1979) suggests that with the force-feeding technique, increased feed intake causes increased rate of passage of excreta. However, it must be remembered that these levels of intake used in the TME bioassay are at or near maintenance, whereas the intakes discussed in the current work are at the extreme of maximum physical feed intake. Tuckey et al. (1958) also suggest that dilution of a diet with fiber (oat hulls) has no effect on rate of passage of digesta. Washburn (1991) showed no relationship between rate of feed passage and feed efficiency in broilers. Reduced growth rate with diluted diets more likely relates to differential partitioning of retained energy. Broilers fed diluted diets consume much more feed and this means that birds must expend more energy in eating and in travelling to feeders. Working with laying hens van Kampen (1976) suggested that the physical act of eating represented about 3% of daily heat production. Because the broiler chicken normally eats proportionally more feed than does the Leghorn, this value is expected to be higher for broilers, and particularly so when feed intake is increased even further by diet dilution. These data suggest that broiler chickens are not eating to near physical capacity, and that when confronted
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converting energy to body weight gain. For example, birds fed at 3,200 kcal/kg needed some 7.1 Mcal/kg gain, whereas for birds fed 1,950 kcal/kg, the efficiency was increased to just 5.9 Mcal/kg. At the same time, however, as energy efficiency was increasing, there was reduction in efficiency of protein used per unit of weight gain. Because there was no major dilution of protein or amino acids in Experiment 1, it is perhaps not too surprising that neither growth rate nor breast weight were affected by diet dilution. Thus, when energy level was reduced, birds would consume much more protein because feed intake was increased. In Experiment 2, when both energy and protein were diluted, birds were not able to maintain constant intakes of either energy or protein. Under these dietary conditions, there was no significant effect on 49-d body weight, because again there was an apparent adaptation to these diluted diets from 42 to 49 d. However, the more sensitive variable of carcass weight and breast weight did show a significant linear decrease in response to diet dilution. The older broiler chicken, therefore, seems more sensitive to protein and amino acid intake than it does to energy intake alone. In both studies there was a decline in the quantity of abdominal fat as diet energy intake was voluntarily reduced. Jackson et al. (1982) and Summers and Leeson (1984) showed similar results for broilers fed a more narrow range of diet energy levels.
528
LEESON ET AL.
with diluted diets they are still capable of adaptation. Reducing the energy level of the finisher diet may have some application for older broilers, although the situation is confounded with a lag period of adaptation to physical intake, during which time feed and energy intake are inadequate and so there is reduced growth rate. Low energy finisher diets will reduce carcass fat content, although the overall picture of energy partitioning for growth vs maintenance needs more careful study.
ACKNOWLEDGMENT This work was supported by the Ontario Ministry of Agriculture, Food and Rural Affairs contract with the University of Guelph.
Cochran, W. G., and G. M. Cox, 1957. Experimental Design. 2nd ed. John Wiley and Sons, New York, NY. Griffiths, L., S. Leeson, and J. D. Summers, 1977. Fat deposition in broilers: Effect of dietary energy to protein balance and early life caloric restriction on productive performance and abdominal fat pad size. Poultry Sci. 56:638-646. Hakansson, J., 1978. Effect of feed energy level on growth and development of the digestive tract of chicks. Sveriges Lantbruksuniversitet. Report 44.
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REFERENCES
Jackson, S., J. D. Summers, and S. Leeson, 1982. The response of male broilers to varying levels of dietary protein and energy. Nutr. Rep. Int. 25:601-606. Leeson, S., J. D. Summers, and L. J. Caston, 1992. Response of broilers to feed restriction or diet dilution in the finisher period. Poultry Sci. 71:2056-2064. Perrault, N., and S. Leeson, 1992. Age-related carcass composition changes in male broiler chickens. Can. J. Anim. Sci. 72: 919-929. SAS Institute, 1990. SAS/STAT® User's Guide. Vol. 2. Version 6. 4th ed. SAS Institute Inc., Cary, NC. Savory, C. J., and M. J. Gentle, 1976a. Effects of dietary dilution with fibre on the food intake and gut dimensions of Japanese quail. Br. Poult. Sci. 17:561-570. Savory, C. J., and M. J. Gentle, 1976. Changes in food intake and gut size in Japanese quail in response to manipulation of dietary fibre content. Br. Poult. Sci. 17:571-580. Sibbald, I. R., 1979. Passage of feed through the adult rooster. Poultry Sci. 58:446^59. Summers, J. D., and S. Leeson, 1984. Influence of dietary protein and energy level on broiler performance and carcass composition. Nutr. Rep. Int. 29:757-767. Tuckey, R., B. E. March, and J. Biely, 1958. Diet and rate of food passage in the gravious chick. Poultry Sci. 37: 786-792. van Kampen, M., 1976. Activity and energy expenditure in laying hens; the energy cost of eating and posture. J. Agric. Sci. Camb. 87:85-88. Washburn, K. W., 1991. Efficiency of feed utilization and rate of feed passage through the digestive system. Poultry Sci. 70:447-452.