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Broiler Weight Gain and Carcass Composition when Fed Diets Varying in Amino Acid Balance, Dietary Energy, and Protein Level
Broiler Weight Gain and Carcass Composition when Fed Diets Varying in Amino Acid Balance, Dietary Energy, and Protein Level J. D. SUMMERS, D. SPRATT,1 and J. L. ATKINSON Department of Animal and Poultry Science, University of Guelph, Guelph, Ontario, NIG 2W1, Canada
ABSTRACT Three experiments were conducted with broiler chicks where diet composition varied with respect to dietary protein, energy, and essential amino acid (EAA) balance. Birds fed diets varying widely in EAA balance and protein and energy levels performed differently with respect to percentage carcass fat and protein. The absolute carcass protein deposition remained relatively constant between treatments, but body fat content varied depending on level of energy intake. Although abdominal fat content varied with level of dietary protein and energy, these values did not correlate well with total carcass fat deposition. Carcass fat deposition correlated well with dietary energy intake, which in turn appeared to be influenced by birds eating to satisfy their EAA requirement. With diets of similar EAA balance, birds appeared to have similar EAA intakes rather than similar energy intakes. Birds fed diets with similar EAA levels, but varying widely in level of nonessential amino acids, energy, or both consumed similar amounts of feed and deposited similar amounts of carcass protein. The present data suggest that level and balance of EAA can have a significant effect on feed intake, thereby influencing weight gain and carcass composition. {Key words: carcass composition, protein deposition, dietary protein, dietary energy, amino acid balance) 1992 Poultry Science 71:263-273
INTRODUCTION Broiler weight for age continues to improve. However, even greater changes continue in the type of poultry meat products offered to the consumer. Furtherprocessed and cut-up carcasses continue to gain an ever increasing share of the market. The type of carcass demanded by the processor for further processing is one that provides the maximum yield of edible meat. A large amount of work has been reported on protein and energy requirements to maximize weight gain (Proud-
1 Present address: Animal Industry Branch, Ontario Ministry of Agriculture and Food, Guelph, ON, NIG 2W1, Canada.
foot and Hulan, 1978, 1980; Jackson et al., 1982; Roush, 1983; Leeson et ah, 1989). There is also a substantial quantity of work showing the influence of dietary protein and energy levels on the composition of the broiler carcass (Moran et al., 1968; Bartov et al., 1974; Lipstein and Bornstein, 1975; Summers et al, 1988). Although the effect of dietary protein on carcass composition is essentially an amino acid effect, as demonstrated by Carew and Hill (1971) and highlighted by the Israeli workers (Bornstein and Lipstein, 1975a,b; Lipstein and Bornstein, 1975; Lipstein et al, 1975), there are a limited number of reports looking at the influence of amino acid supplementation on increased protein deposition in the carcass. Sibbald and Wolynetz (1986) reported that the lysine requirement for
263
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(Received for publication March 12, 1991)
264
SUMMERS ET AL.
MATERIALS AND METHODS Experiment 1 Commercial male, day-old broiler chicks were randomly distributed to 12 litter floor pens until there were 40 birds per each 1.8 x 2.5 m pen. Three such pens were then placed on each dietary treatment as follows: 1) A control ration, which was a regular commercial corn and soybean meal diet containing 23% protein, but with no methionine or lysine supplementation. This diet, while meeting the National Research Cound l (NRC, 1984) requirement for lysine, only met around 78% of the total sulphur amino a d d requirement. 2) Similar to Diet 1, but protein was reduced to a level where lysine just met requirement levels and methionine was supplemented to requirement. Thus, all EAA were at requirement levels or above. Calculations showed that the sulphur amino a d d s and lysine were actually
only around 95% requirement levels, but for simplicity of discussion they will be referred to as NRC values. 3) Similar to Diet 1, but the protein level was reduced so that lysine was 20% below the level of Diet 2, and methionine was supplemented to a level also 20% lower than Diet 2. 4) The dietary protein level was similar to Diet 1 (23%), but lysine and methionine were supplemented to levels 20% above Diet 2. Thus, Diet 2 just met the requirements for lysine and total sulphur amino a d d s , but Diet 3 provided levels 20% below and Diet 4,20% above requirements for these amino acids. Energy levels were similar for the four dietary treatments and all other EAA (other than methionine and lysine), met NRC (1984) minimum requirement levels. Similar changes to those outlined above were made to the finisher diets. The composition of the diets is shown in Table 1. The experimental diets were fed, in crumble form, from 1 day of age to 3 w k of age at which time pelleted finisher diets were fed. All birds were weighed and feed intake recorded at 3 wk of age. Five birds per replicate, of average weight, were used for the determination of carcass protein and fat content. Similarly, at 6 wk of age body weight and feed intake were recorded and carcass fat and protein were determined on five birds per replicate. The remaining birds were used to measure abdominal fat, which included that surrounding the gizzard and intestines extending within the ischium and surrounding the bursa of Fabricius.
Experiment 2 Male, day-old broilers were randomly distributed to 12 litter floor pens, with 40 birds per each 1.8 x 2.5 m pen. Three such pens were placed on each of the following dietary treatments: 1) identical to the control used in Experiment 1; 2) similar to Diet 2 in protein and methionine and lysine levels in Experiment 1, but with the energy level reduced so that the calorie to protein ratio equalled that of Diet 1 (wheat shorts and alpha floe were added to reduce dietary energy); 3) protein and amino a d d levels were similar to that of Diet 3 in Experiment 1; however, the energy level was reduced with the addition of wheat shorts and
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maximum protein accretion in a bird was higher than that required for maximum weight gain. Summers and Leeson (1985) studied the effed of diets varying in level of protein and amino acid supplementation on yield of edible carcass meat. Although absolute yield differed very little with the diets they employed, those authors demonstrated that essential amino a d d (EAA) supplementation could alter the protein content of the edible meat. Summers et al. (1988) confirmed the above work and suggested that yield of edible protein should be used as a parameter in evaluating EAA requirements. If, as suggested by some workers (Plavnik and Hurwitz, 1985; Calvert et al, 1988), fat deposition is less with birds exhibiting compensatory growth, protein deposition must be greater if birds of the same weight are obtained. This being the case, one might exped, as suggested by Plavnik and Hurwitz (1989), that diets differing in EAA balance may significantly alter the pattern of weight gain during early compensatory growth. Thus, the present study was undertaken to evaluate the performance of broiler chicks fed diets varying widely in methionine and lysine levels (EAA balance), as well as level of dietary energy.
19.0 3,165 .43 29 1.04
60.3 28.75 55 1.25 15 .35 1.49 .5 .25 .11
1 C i„ „ .
62.0 25.75 5.75 1.25 1.5 .35 2.49 .5 .25 .16
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Finisher
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17.8 3,168 .46 .27 .95
2
Provides per kilogram of diet: manganese, 55 mg; zinc, 50 mg; copper, 5 mg; iron, 30 mg; and selenium, .1 mg. ^Calculated from analysis of corn and soybean meal.
2
23.2 3,082 .70 .36 1.38
17.7 3,076 .44 .26 .93
- (%) •
1
72.25 19.25 3.5 1.25 1.5 .35 1.08 .5 .25 .07
m
„
15.5 3,168 .35 .23 .76
3
62.0 25.75 5.5 1.25 1.5 .35 2.34 .5 25 .31 25 18.1 3,161 .61 .27 1.15
4
Provides per kilogram of diet: vitamin A, 8,800 IU; cholecaldferol, 1,600 IU; vitamin E, 11.0 mg; riboflavin, 9.0 mg; biotin, .25 mg; pantothenic add, 11.0 mg; vitamin Bj2,13
51.0 38.75 5.0 1.25 1.5 .35 1.03 .5 25 .33 .04
4 65.0 25.0 3.50 1.25 1.50 .35 2.52 .5 .25 .13
3
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1
20.5 3,076 .56 .32 1.16
23.0 3,072 .37 .36 1.34
Starter
o
C
otil
9
S
n g
3 w
H
1
0
n
8
DIET
• •A..
55.0 32.75 5.25 1.25 1.50 .35 2.93 .5 .25 .22
51.0 38.75 5.0 1.25 1.3 .35 1.6 .5 25
Corn Soybean meal (48% CP) Animal-vegetable blend fat Limestone Calcium phosphate Salt (.015% KI) Alpha floe Vitamin mix 1 Mineral mix 2 DL-methionine L-lysine HC1 Calculated analysis Protein, %3 Energy, kcal/kg Methionine^ % Cystine, %3 Lysine, %3
2
1
Ingredients and analysis
TABLE 1. Experimental diets, Experiment 1
ROILER
266
SUMMERS ET AL. TABLE 2. Experimental diets, Experiment 2 Starter
Ingredients and arcilysis
2
Finisher 4
3
3
2
4
(%) 53.54 31.57 1.05 1.24 1.49 .35 .5 .25 6.63 .02 3.36
22.0 17.59 1.0 1.57 1.32 .35 .5 .25 7.07 .18 .04 38.13 10.0
53.91 25.37 7.3 1.84 .77 .35 .5 25
59.35 23.37 1.0 1.49 1.33 .35 .5 25 2.19 .13 .04
.33 .14
10.0
40.1 14.66 1.0 1.56 1.17 .35 .5 25 7.04 .14 .13 23.1 10.0
56.96 29.02 9.92 1.46 1.35 .35 .5 .25 .06 .13
15.6 2,581 .39 .24 .84
19.0 3,422 .44 .29 1.07
5.0 2.24 2.0 20.5 2,738 .53 .31 1.14
17.8 2,364 .44 27 .93
23.0 3,286 .67 .41 1.39
17.8 2,964 .43 29 .97
Provides per kilogram of diet: vitamin A, 8,000 IU; cholecalciferol, 1,600 IU; vitamin E, 11.0 mg; riboflavin, 9.0 mg; biotin, 25 mg; pantothenic acid, 11.0 mg; vitamin B-yx, 13 ug; niacin, 26 mg; choline, 900 mg; vitamin K (menadione sodium bisulfite complex), 1.5 mg; folic acid, 15 mg; santoquin, 125 mg. Provides per kilogram of diet: manganese, 55 mg; zinc, 50 mg; copper, 5 mg; iron, 30 mg; and selenium, .1 mg. 3 Calculated from analysis on individual ingredients.
wheat, so that the calorie to protein ratio equalled that of Diet 1; and 4) the protein level was similar to Diet 4 in Experiment 1, but some animal protein sources were added to the diet and the energy level was approximately 7% higher than Diet 1. There was no particular reason for the addition of some animal protein products or the increase in dietary energy for Treatment 4 except to broaden the ingredient base and increase the energy level of the diet. Finishing diets were reduced in protein level similar to Experiment 1 with energy levels altered similar to that described above. The exception was Diet 4 where protein, methionine, and lysine content remained similar to Diet 1, but energy was increased by approximately 7%, as with the starter diet. Tlie composition of diets for Treatments 2, 3, and 4 is shown in Table 2 (Diets 2,3, and 4). The starter diets were fed as crumbles and the finisher diets as pellets. Birds were kept on the starter diets till 3
wk of age at which time five birds per replicate were used for carcass analysis. The birds were then placed on the finisher diets till 42 days of age. At this time birds were weighed, feed intake recorded, and five birds per replicate used for carcass analysis. All remaining birds were used to measure abdominal fat.
Experiment 3 Male, 7-day-old commercial broiler chicks were randomly distributed 10 birds per pen in battery brooders. Four such pens were placed on each of the following dietary treatments for a 2-wk test period: 1) a 16.5% protein, corn and soybean meal diet with all the EAA at NRC (1984) requirement levels and containing 2,650 kcal of ME/kg of diet; 2) the same protein and amino acid levels as Diet 1 (with corn and soybean meal levels kept constant) but with dietary energy level increased to 2,850 kcal ME/kg
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Corn Soybean meal (48% CP) Animal-vegetable blend fat Limestone Calcium phosphate (20% P) Salt (.015% KI) Vitamin mix 1 Mineral mix 2 Alpha floe DL-methionine L-lysine HC1 Wheat shorts Wheat Meat meal Feather meal Blood meal Calculated analysis Protein, %3 Energy, kcal/kg Methionine, %•* Cystine, %3 Lysine, %3
267
BROILER PERFORMANCE AND DIET COMPOSITION TABLE 3. Experimental diets. Experiment 3 1 Ingredients and analysis V'O)
31.7 21.9 17.7 4.3 1.4 1.82 .32 .5 .25 .51 17.1 2.5
31.7 21.9 235 4.3 1.4 1.82 .32 .5 .25 .51 11.60 2.5
31.7 21.9 28.5 4.3 1.4 1.82 .35 .5 .25 .51 6.27 2.5
16.5 2,653 .72 51 151
16.5 2,853 .72 .21 1.21
16.5 3,051 .72 .21 1.21
*For the 19% protein test diets .5% glycine; 1 5 aspartic add, and 1.5 alanine were added to Diets 1,2, and 3 at the expense of glucose, and for the 23% protein test diets 5,42, and 45% of the above amino adds were added. 2 Provides per kilogram of diet: vitamin A, 8,000 IU; cholecalciferol, 1,600 IU; vitamin E, 11.0 mg; riboflavin, 9.0 mg; biotin, 5 5 mg; pantothenic add, 11.0 mg; vitamin Bj2,13 (ig; niacin, 26 mg; choline, 900 mg; vitamin K (menadione sodium bisulfite complex), 1.5 mg; folic add, 1.5 mg; santoquin, 125 mg. Provides per kilogram of diet: manganese, 55 mg; zinc, 50 mg; copper, 5 mg; iron, 30 mg; and selenium, .1 mg. Percentage of amino add mix: L-lysine H Q , 22.0; L-glydne, 24.0; L-phenylalanine, 7.2; L-arginine HC1,19.2; L-leudne, 6.4; L-threonine, 10.4; L-tryptophan, 3.6; L-isoleudne, 4.8; L-valine, 2.4. Calculated from analysis done on individual ingredients.
TABLE 4. Performance of male broilers fed diets containing various levels of dietary lysine and methionine, Experiment 1
Treatment Protein
Methionine
Lysine
23.0 20.5 17.7 23.2
1 2 3 4 SD
19.0 17.8 15.5 18.1
.37 .56 .44 .70
1.34 1.16 .93 1.38
3,072 3,076 3,076 3,082
(tr^
718* 703* 639 b 720*
3,165 3,165 3,168 3,161
1|||
1.04 .95 .76 1.15
43.9
1 2 3 4 SD
2,005* 2,038* l,841 b 2,016* 52.9 b
Feed:gain
Nb'
17.0 .43 .46 .35 .61
Feed intake
Gain
(kcal/kg)
(%) 1 2 3 4 SD
Metabolizable energy
972 965 948 969 26.0 2,757*b 2,884* 2,733 b 2,778*b 695 3,729 3,849 3,681 3,747 86.8
1.35b 1.37b 1.48* 1.35b .02 2.08 b 2.10 b 2.19* 2.10 b .07 1.86b 1.89b 2.00* 1.86b .02
*' Means in columns within time periods with no common superscripts differ significantly (P<.05).
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Corn Soybean meal (48% CP) Glucose monohydrate Animal-vegetable blend fat Limestone Caldum phosphate (20% P) Iodized salt (.015% KI) Vitamin mix 2 Mineral mix 3 DL-methionine Alpha floe Amino add mix 4 Calculated analysis Protein, %5 ME, kcal/kg Methionine. %5 Cystine, %S Lysine, %5
1 2 3 4 SD
l_c
.43 .46 .35 .61
.37 .56 .44 .70
(%) —
1.04 .95 .76 1.15
1.34 1.16 .93 1.38
Methionine Lysine
.
3,165 3,168 3,168 3,161
3,072 3,076 3,076 3,082
(kcal/kg)
Metabolizable energy
197.5
1,439s 1,447" l,299 b l,425 a
48.1
633 a 631 a 568 b 634 a
(g)
Carcass
Means in columns within ages with no common superscripts differ significantly (P<.05).
19.0 17.8 155 18.1
23.0 20.5 17.7 23.2
1 2 3 4
SD
Protein
Treatment
TABLE 5. Carcass composition, Experiment 1
46.7** 45.9 a 40.9 b 44.0 b 2.4
52.1 a 53.0 a 47.8 b 53.5 a 2.1
Carcass fat
2.2 44.2 b 45.5 b 51.6 a 49.2 a 32
330 a 343 a 285 b 328 a 28.0
38.6 b 37.9 b 43.9 s 37.2 b
324 329 373 377 44.8
9.1
75.0 b 74.0 b 88.8 a 71.9 b
(% DM) (g)
101 104 97 103 8.6
(% DM) (g)
Carcass protein
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38.1c 42.8 b 49.3 a 41 .l 1 *
7.8 9.3 10.1 7.5 3.4
(g>
1.87° 2.05 b 258a l.^1* 0.54
1.09 1.33 1.58 1.06 05
(% BW)
Abdominal fat
£
H
1
g
VI
269
BROILER PERFORMANCE AND DIET COMPOSITION
Statistical Analysis Performance and carcass composition data were analyzed using the General Linear Models procedure (SAS Institute, 1985). After analysis of variance, significantly different parameter means were
separated using Duncan's multiple range test (Duncan, 1955).
RESULTS AND DISCUSSION A significant reduction in weight gain and an increased feed:gain ratio were noted when chicks were fed diets with methionine and lysine values reduced by 20% less than NRC (1984) requirement values for the 3-wk-old birds (Table 4). Feed intake was not significantly different for the various treatments. For the 3- to 6-wk period, feed intake, weight gain, and feed:gain ratio were significantly reduced for birds fed the -20% methionine and lysine diet as compared with the diet formulated to NRC (1984) methionine and lysine requirements. The data for 0 to 6 wk, in general, mirrored that reported above. Weight gain was similar for Treatments 1, 2, and 4, where levels of methionine and lysine met NRC (1984) requirement levels, were 20% over stated requirement, or where lysine met requirement levels but methionine was only about 75% of requirement, respectively. Treatment 3,
TABLE 6. Performance of male broilers fed diets differing in calorie to protein ratio, Experiment 2
Treatment levels
Lysine Protein
Methionine •
.37 .53 .44 .67
1 2 3 4 SD
( % )
1.34 1.14 .93 1.39
—
23.0 20.5 17.8 23.0
Metabolizable energy
Calorie: protein Weight ratio gain
(kcal/kg) 0 to 3 wk 3,072 134 134 2,738 2,364 134 3,286 143
Feed intake (g)
741 a 706 a 619 b 741 a 20.7
Feed: gain
l,054 b l,090 a b l,138 a l,101 a b 34.6
1.42c 1.54b 1.84a 1.49** 0.05
3 to 6 wk 1 2 3 4 SD
.43 .43 .39 .44
1 2 3 4 SD a_c
1.04 .97 .84 1.07
19.0 17.8 15.5 19.0
3,164 2,964 2,581 3,422
167 167 167 180
l,464 a l,421 a b l,386 b 1,469s 27.6
3,063 b 2.09 bc 3,053 b 2.15 b 3,377* 2.44 a 2,937b 2.00 c 82.4 0.05 - 0 to 6 wk 4,116 b 1.87= 2,206a 2,127b 4,143 b 1.95b 2,005° 4,515a 2.25 a 2,210" 4,038 b 1.83c 0.04 33.6 78.6
Means in columns within time periods with no common superscripts differ significantly (P<.05).
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of diet; 3) the same protein level and source as above but with energy level increased to 3,050 kcal M E / k g of diet. Dietary energy levels were altered by the substitution of glucose for alpha floe. Additional dietary treatments resulted by supplementing the above three diets with non-essential amino acids (NEAA) (aspartic, alanine, and glycine) to bring crude protein levels up to 19.5 and 23.9%. Composition of the low-protein diets at the three levels of energy are shown in Table 3. The EAA and NEAA supplements are also shown. The experiment was set u p as a factorial arrangement of treatments with three levels of protein and three levels of dietary energy. At 21 days of age, chick weight and feed intake were recorded and three birds per replicate saved for carcass analysis.
270
SUMMERS ET AL. TABLE 7. Carcass composition of male broilers fed diets varying in calorie to protein ratio (Experiment 2)
Treatment
Protein
Metabolizable energy
(%)
(kcal/kg)
23.0 20.5 17.7 23.0
3,072 2,738 2,364 3,286
Calorie: protein ratio
Carcass composition Protein
Fat
(% DM) (g)
(% DM) (g)
53.7^ 55.6b 59.3a 51.1° 3.13
38.4a 33.6 ab 30.4 b 39.5a
3 wk 134 134 134 143
84.6 86.6 78.5 88.8 8.55
6.1
60.5a 52.6 ab 41.6 b 66.8a 12.7
6 wk 1 2 3 4 SD
19.0 17.8 15.5 19.0
3,164 2,964 2,581 3,422
167 167 167 180
48.8 ab 48.4 ab 49.9a 45.8 b
2.9 a_c
261 253 237 247 25.2
43.7 ab 42.7 b 40.9° 46.4a 3.08
237ab 224 b 195 c 252 s 33.5
Means in columns within ages with no common superscripts differ significantly (P<.05).
with methionine and lysine levels 20% lower than stated requirement values, resulted in a weight depression of around 10%, as compared with the other dietary treatments at 3 and 6 wk of age. Percentage carcass fat was greater and percentage carcass protein lower for birds fed the -20% methionine and lysine at 3 wk of age compared with the other dietary treatments (Table 5). Similar results were noted at 6 wk of age for this group. Interestingly, percentage carcass protein was lower and percentage carcass fat higher for the +20% methionine and lysine diet than lower methionine and lysine diets (Treatments 1 and 2) at 6 wk of age. However, although the absolute quantity of fat deposited in the carcass was higher than Treatments 1 and 2, these differences were not significant. Similar amounts of abdominal fat, both on an absolute basis and as a percentage of live weight for these three treatments, would suggest that the extra fat resulting from the higher levels of methionine and lysine (which amounted to approximately 16%), was deposited in areas other than the abdominal region. Similarly, Summers and Leeson (1985) reported an increase in fat content of breast meat with methionine supplementation to a low-protein diet. The diet low in methionine and lysine (Treatment 3, Table 5) resulted in a significantly higher
level of abdominal fat at 6 wk of age than the diet high in methionine and lysine (Treatment 4). However, the results for carcass fat suggest similar levels for these two treatments. These results suggest that abdominal fat is not necessarily a good indicator of carcass fat deposition.
Experiment 2 At 3 wk of age, weight gain and feed:gain ratios of the low methionine and lysine, low-energy diet (Treatment 3) were significantly poorer than that of the other dietary treatments (Table 6). A similar response in bird performance is seen for the various dietary treatments from 3 to 6 wk of age and, as with Experiment 1, the overall 0 to 6 wk data show similar treatment responses. Of interest is the weight gain of the birds in Experiment 2, as compared with Experiment 1. At 6 wk of age, birds in Experiment 2 were heavier than those of Experiment 1 (as a ratio to Experiment 1, these weights were 1.10, 1.05, 1.09, and 1.10 for Treatments 1 through 4, respectively. Although protein and EEA levels were similar for treatments in the two experiments, dietary energy levels differed significantly. It appears that weight gain in both experiments was correlated with EAA intake not energy intake. Although the percentage carcass protein varied significantly at 3 w k of age between
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1 2 3 4 SD
271
BROILER PERFORMANCE AND DIET COMPOSITION TABLE 8. Performance of male broilers fed diets varying in level of energy and nonessential amino acids (7 to 21 days of age)
Treatment
Feed intake
Gain -(g)
a-c
Protein
Fat
(g=g)
(% DM) (g)
(% DM) (g)
467 s 442 b 379 c
777* 730 b 702 b
1.66b 1.65b 1.85a
53.5 b 55.8a 56.5 a
104.5a 100.5a 89.1 b
38.6 a 34.7 b 33.0C
75.5 a 62.5 b 52.0C
421 438 429 20.8
724 747 738 38.5
1.73 1.71 1.73 .10
58.4 a 54.6 b 52.8C .62
100.0 98.6 95.7 3.7
33.6C 35.6 b 37.1 a 1.7
57.6C 64.3 b 67.2 a .67
Means in a column within treatments with no common superscripts differ significantly (P<.05).
birds fed the various dietary treatments (Table 7), absolute deposition of protein in the carcasses was similar. However, carcass fat content both on a percentage and on an absolute basis showed major differences between dietary treatments. Similar results were observed with the 6-wk carcass composition data. It is of interest to compare the changes in carcass protein and fat on a percentage basis at 3 and 6 wk of age with the actual deposition of these nutrients. Between 3 and 6 wk of age, percentage carcass protein decreased on the average across all treatments by around 13%, but percentage carcass fat increased by approximately 34%. A similar comparison of deposition of these nutrients at the same ages gave values of a 194% increase for protein and a 313% increase for fat. Such values point out the importance of looking at absolute as well as percentage changes in carcass composition of nutrients, especially when carcass quality studies are being evaluated.
Experiment 3 The protein by energy interaction was not significant. Thus, only the main treatment effects will be discussed. N o significant differences in weight gain, feed intake, or feed:gain ratio were noted for birds fed various dietary protein levels (Table 8). However, these parameters were significantly affected by increased dietary energy levels. As dietary protein level increased, percentage carcass protein was significantly
higher, but the reverse was true for percentage carcass fat. Increasing dietary energy resulted in carcasses with significantly higher percentages of fat and lower percentages of protein. Absolute quantities of carcass protein were similar for the three dietary protein levels and were similar to the absolute quantity of protein found in the carcasses of birds fed various levels of dietary energy with the exception of the low-energy diet. However, significant increases in absolute quantity of carcass fat were noted for those birds fed increased levels of dietary energy. An increased level of dietary protein resulted in carcasses containing less absolute fat. There were marked differences in intake of protein and energy between the various dietary treatments (Table 9). Although feed intake across the main diet treatments varied by approximately 11% (Table 8) protein intake varied by 42% and energy by 27% (Table 9). The NEAA intake varied by approximately 124% for the above comparison, but EAA intake varied by only 10%. These findings substantiate the report of Bedford and Summers (1985), who reported that weight gain and carcass protein appeared to be closely related to total intake of EAA rather than protein or nitrogen intake. The present study suggests that feed intake can be significantly altered by the EAA balance of a diet. This supports the early hypothesis of Lipstein et ah (1975) that birds will "overeat" in an attempt to consume amounts of limiting EAA required for maximum growth. The present data
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Energy, kcal/kg 3,050 2,850 2,650 Protein level, % 23.9 19.5 16.5 SD
Carcass Feed:gain
272
SUMMERS ET AL. TABLE 9. Nutrient intake of male broilers fed diets varying in level of energy and nonessential amino acids Average intake from 7 to 21 days
Treatment
a
NEAA
Energy
(kcal)
155 145 140
2,370 2,081 1,860
13.3 12.5 12.1
11.5 105 10.4
173 146 122
2,111 2,130 2,068
12.5 12.8 12.7
15.0 10.5 6.7
*6'
"""
EAA = essential amino acids; NEAA = nonessential amino acids.
lend further support to the reports of Summers et at (1988) and Parr and Summers (1991) that within certain dietary limits birds produce carcasses of equal lean mass, thus corifirming that birds do eat in an attempt to satisfy their EAA requirements. The present study also confirms the work of Lipstein et al. (1975) that higher energy diets often produce greater weight gain d u e to the fact that increased fat deposition takes place as the bird consumes greater quantities of energy as it attempts to satisfy its EAA requirements. The present study presents evidence that abdominal fat measurements may not be good indicators of total body fat deposition. This substantiates the work of Butterwith (1989), who showed that although broiler neck, thigh, and abdominal fat content remained relatively constant and similar to 30 days of age, abdominal fat content increased markedly after this time. This suggests that the abdominal fat depot areas are in effect a "sink" for excess energy intake and thus could be a poor parameter to measure when studying carcass fat deposition. ACKNOWLEDGMENTS The authors wish to acknowledge the National Research Council, Ottawa, ON, and the Ontario Ministry of Agriculture and Food for financial support. REFERENCES Bartov, I., S. Bomstein, and B. Lipstein, 1974. Effect of calorie to protein ratio on the degree of fatness
in broilers fed on practical diets. Br. Poult. Sci. 15:107-117. Bedford, M. R., and J. D. Summers, 1985. Influence of the ratio of essential to non-essential amino acids on performance and carcass composition of the broiler chick. Br. Poult. Sci. 26:483-491. Bomstein, S., and B. Lipstein, 1975a. The replacement of some of the soybean meal by the first limiting amino adds in practical broiler diets. 1. Value of special supplementation of chick diets with methionine and lysine. Br. Poult. Sci. 16:177-188. Bomstein, S., and B. Lipstein, 1975b. The replacement of some of the soybean meal by the first limiting amino acids in practical broiler diets. 2. Special additions of methionine and lysine as partial substitutes for protein in finisher diets. Br. Poult. Sci. 16:189-200. Butterwith, S. C , 1989. Contribution of lipoprotein lipase activity to the differential growth of three adipose tissue depots in young broiler chickens. Br. Poult. Sci. 30527-933. Calvert, C. C , I. P. McMurtry, R. W. Rosebrough, and N. C. Steele, 1988. Effect of energy level and early feed restriction on rate and composition of gain in broilers. Poultry Sci. 67(Suppl. 1): 61.(Abstr.) Carew, L. B., and F. W. HiU, 1961. Effects of methionine deficiency on the utilization of energy by the chick. J. Nutr. 74:185-190. Duncan, D. B., 1955. Multiple range and multiple F tests. Biometrics 11:1-42. 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: 601-612. Leeson, S., L. J. Caston, and J. D. Summers, 1989. Comparison of feed allocation system in broiler nutrition studies. Nutr. Rep. Int. 39:617-626. Lipstein, B. S., and S. Bomstein, 1975. The replacement of some of the soybean meal by the first limiting amino acids in practical broiler diets. 2. Special additions of methionine and lysine as partial substitutes for protein in finisher diets. Br. Poult. Sci. 16:189-200. Lipstein, B., S. Bomstein, and I. Bartov, 1975. The replacement of some of the soybean meal by the ftet-limiting amino acids in practical broiler
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Energy, kcal/kg 3,050 2,850 2,650 Protein level, % 23.9 19.5 16.5
EAA
Protein
BROILER PERFORMANCE AND DIET COMPOSITION
with different protein and energy levels to males and females of commercial broiler genotypes. Can. J. Anim. Sd. 58:391-398. Proudfoot, F. G., and H. W. Hulan, 1980. Performance of chicken broilers changed from starter to finisher diet different ages. Can. J. Anim. Sd. 60: 799-801. Roush, W. B., 1983. An investigation of protein levels for broiler starter and finisher rations and the time of ration change by response surface methodology. Poultry Sd. 62:110-116. SAS Institute, 1985. SAS® User's Guide: Statistics. Version 5 Edition. SAS Institute Inc., Cary, NC. Sibbald, I. R., and M. S. Wolynetz, 1986. Effects of dietary lysine and feed intake on energy utilization and tissue synthesis by broiler chicks. Poultry Sd. 65:98-105. Summers, J. D., and S. Leeson, 1985. Broiler carcass composition as affected by amino add supplementation. Can. J. Anim. Sd. 65:717-723. Summers, J. D., S. Leeson, and D. Spratt, 1988. Yield and composition of edible meal from male broilers as influenced by dietary protein level and amino add supplementation. Can. J. Anim. Sd. 64241-248.
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diets. 3. Effects of protein concentrations and amino acid supplementations in broiler finisher diets on fat deposition in the carcass. Br. Poult. Sd. 16:627-635. Moran, E. T., Jr., J. D. Summers, and H. L. Qrr, 1968. Back fat, qualitative measure of broiler carcass finish: technique, correlation with grade and effect of dietary caloric density. Food Technol. Champaign 22599-1002. National Research Council, 1984. Nutrient Requirements of Poultry. 8th rev. ed. National Academy Press, Washington, DC. Parr, J. F., and J. D. Summers, 1991. The effect of minimizing amino add excesses in broiler diets. Poultry Sd. 70:1540-1549. Plavnik, I., and S. Hurwitz, 1985. The performance of broiler chicks during and following a severe feed restriction at an early age. Poultry Sd. 64: 348-355. Plavnik, I., and S. Hurwitz, 1989. Effect of dietary protein, energy and feed pelleting on the response of chicks to early feed restriction. Poultry Sd. 68:1118-1125. Proudfoot, F. G., and H. W. Hulan, 1978. The interrelated effects of feeding diet combinations
273
ABSTRACT Three experiments were conducted with broiler chicks where diet composition varied with respect to dietary protein, energy, and essential amino acid (EAA) balance. Birds fed diets varying widely in EAA balance and protein and energy levels performed differently with respect to percentage carcass fat and protein. The absolute carcass protein deposition remained relatively constant between treatments, but body fat content varied depending on level of energy intake. Although abdominal fat content varied with level of dietary protein and energy, these values did not correlate well with total carcass fat deposition. Carcass fat deposition correlated well with dietary energy intake, which in turn appeared to be influenced by birds eating to satisfy their EAA requirement. With diets of similar EAA balance, birds appeared to have similar EAA intakes rather than similar energy intakes. Birds fed diets with similar EAA levels, but varying widely in level of nonessential amino acids, energy, or both consumed similar amounts of feed and deposited similar amounts of carcass protein. The present data suggest that level and balance of EAA can have a significant effect on feed intake, thereby influencing weight gain and carcass composition. {Key words: carcass composition, protein deposition, dietary protein, dietary energy, amino acid balance) 1992 Poultry Science 71:263-273
INTRODUCTION Broiler weight for age continues to improve. However, even greater changes continue in the type of poultry meat products offered to the consumer. Furtherprocessed and cut-up carcasses continue to gain an ever increasing share of the market. The type of carcass demanded by the processor for further processing is one that provides the maximum yield of edible meat. A large amount of work has been reported on protein and energy requirements to maximize weight gain (Proud-
1 Present address: Animal Industry Branch, Ontario Ministry of Agriculture and Food, Guelph, ON, NIG 2W1, Canada.
foot and Hulan, 1978, 1980; Jackson et al., 1982; Roush, 1983; Leeson et ah, 1989). There is also a substantial quantity of work showing the influence of dietary protein and energy levels on the composition of the broiler carcass (Moran et al., 1968; Bartov et al., 1974; Lipstein and Bornstein, 1975; Summers et al, 1988). Although the effect of dietary protein on carcass composition is essentially an amino acid effect, as demonstrated by Carew and Hill (1971) and highlighted by the Israeli workers (Bornstein and Lipstein, 1975a,b; Lipstein and Bornstein, 1975; Lipstein et al, 1975), there are a limited number of reports looking at the influence of amino acid supplementation on increased protein deposition in the carcass. Sibbald and Wolynetz (1986) reported that the lysine requirement for
263
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(Received for publication March 12, 1991)
264
SUMMERS ET AL.
MATERIALS AND METHODS Experiment 1 Commercial male, day-old broiler chicks were randomly distributed to 12 litter floor pens until there were 40 birds per each 1.8 x 2.5 m pen. Three such pens were then placed on each dietary treatment as follows: 1) A control ration, which was a regular commercial corn and soybean meal diet containing 23% protein, but with no methionine or lysine supplementation. This diet, while meeting the National Research Cound l (NRC, 1984) requirement for lysine, only met around 78% of the total sulphur amino a d d requirement. 2) Similar to Diet 1, but protein was reduced to a level where lysine just met requirement levels and methionine was supplemented to requirement. Thus, all EAA were at requirement levels or above. Calculations showed that the sulphur amino a d d s and lysine were actually
only around 95% requirement levels, but for simplicity of discussion they will be referred to as NRC values. 3) Similar to Diet 1, but the protein level was reduced so that lysine was 20% below the level of Diet 2, and methionine was supplemented to a level also 20% lower than Diet 2. 4) The dietary protein level was similar to Diet 1 (23%), but lysine and methionine were supplemented to levels 20% above Diet 2. Thus, Diet 2 just met the requirements for lysine and total sulphur amino a d d s , but Diet 3 provided levels 20% below and Diet 4,20% above requirements for these amino acids. Energy levels were similar for the four dietary treatments and all other EAA (other than methionine and lysine), met NRC (1984) minimum requirement levels. Similar changes to those outlined above were made to the finisher diets. The composition of the diets is shown in Table 1. The experimental diets were fed, in crumble form, from 1 day of age to 3 w k of age at which time pelleted finisher diets were fed. All birds were weighed and feed intake recorded at 3 wk of age. Five birds per replicate, of average weight, were used for the determination of carcass protein and fat content. Similarly, at 6 wk of age body weight and feed intake were recorded and carcass fat and protein were determined on five birds per replicate. The remaining birds were used to measure abdominal fat, which included that surrounding the gizzard and intestines extending within the ischium and surrounding the bursa of Fabricius.
Experiment 2 Male, day-old broilers were randomly distributed to 12 litter floor pens, with 40 birds per each 1.8 x 2.5 m pen. Three such pens were placed on each of the following dietary treatments: 1) identical to the control used in Experiment 1; 2) similar to Diet 2 in protein and methionine and lysine levels in Experiment 1, but with the energy level reduced so that the calorie to protein ratio equalled that of Diet 1 (wheat shorts and alpha floe were added to reduce dietary energy); 3) protein and amino a d d levels were similar to that of Diet 3 in Experiment 1; however, the energy level was reduced with the addition of wheat shorts and
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maximum protein accretion in a bird was higher than that required for maximum weight gain. Summers and Leeson (1985) studied the effed of diets varying in level of protein and amino acid supplementation on yield of edible carcass meat. Although absolute yield differed very little with the diets they employed, those authors demonstrated that essential amino a d d (EAA) supplementation could alter the protein content of the edible meat. Summers et al. (1988) confirmed the above work and suggested that yield of edible protein should be used as a parameter in evaluating EAA requirements. If, as suggested by some workers (Plavnik and Hurwitz, 1985; Calvert et al, 1988), fat deposition is less with birds exhibiting compensatory growth, protein deposition must be greater if birds of the same weight are obtained. This being the case, one might exped, as suggested by Plavnik and Hurwitz (1989), that diets differing in EAA balance may significantly alter the pattern of weight gain during early compensatory growth. Thus, the present study was undertaken to evaluate the performance of broiler chicks fed diets varying widely in methionine and lysine levels (EAA balance), as well as level of dietary energy.
19.0 3,165 .43 29 1.04
60.3 28.75 55 1.25 15 .35 1.49 .5 .25 .11
1 C i„ „ .
62.0 25.75 5.75 1.25 1.5 .35 2.49 .5 .25 .16
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17.8 3,168 .46 .27 .95
2
Provides per kilogram of diet: manganese, 55 mg; zinc, 50 mg; copper, 5 mg; iron, 30 mg; and selenium, .1 mg. ^Calculated from analysis of corn and soybean meal.
2
23.2 3,082 .70 .36 1.38
17.7 3,076 .44 .26 .93
- (%) •
1
72.25 19.25 3.5 1.25 1.5 .35 1.08 .5 .25 .07
m
„
15.5 3,168 .35 .23 .76
3
62.0 25.75 5.5 1.25 1.5 .35 2.34 .5 25 .31 25 18.1 3,161 .61 .27 1.15
4
Provides per kilogram of diet: vitamin A, 8,800 IU; cholecaldferol, 1,600 IU; vitamin E, 11.0 mg; riboflavin, 9.0 mg; biotin, .25 mg; pantothenic add, 11.0 mg; vitamin Bj2,13
51.0 38.75 5.0 1.25 1.5 .35 1.03 .5 25 .33 .04
4 65.0 25.0 3.50 1.25 1.50 .35 2.52 .5 .25 .13
3
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1
20.5 3,076 .56 .32 1.16
23.0 3,072 .37 .36 1.34
Starter
o
C
otil
9
S
n g
3 w
H
1
0
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8
DIET
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55.0 32.75 5.25 1.25 1.50 .35 2.93 .5 .25 .22
51.0 38.75 5.0 1.25 1.3 .35 1.6 .5 25
Corn Soybean meal (48% CP) Animal-vegetable blend fat Limestone Calcium phosphate Salt (.015% KI) Alpha floe Vitamin mix 1 Mineral mix 2 DL-methionine L-lysine HC1 Calculated analysis Protein, %3 Energy, kcal/kg Methionine^ % Cystine, %3 Lysine, %3
2
1
Ingredients and analysis
TABLE 1. Experimental diets, Experiment 1
ROILER
266
SUMMERS ET AL. TABLE 2. Experimental diets, Experiment 2 Starter
Ingredients and arcilysis
2
Finisher 4
3
3
2
4
(%) 53.54 31.57 1.05 1.24 1.49 .35 .5 .25 6.63 .02 3.36
22.0 17.59 1.0 1.57 1.32 .35 .5 .25 7.07 .18 .04 38.13 10.0
53.91 25.37 7.3 1.84 .77 .35 .5 25
59.35 23.37 1.0 1.49 1.33 .35 .5 25 2.19 .13 .04
.33 .14
10.0
40.1 14.66 1.0 1.56 1.17 .35 .5 25 7.04 .14 .13 23.1 10.0
56.96 29.02 9.92 1.46 1.35 .35 .5 .25 .06 .13
15.6 2,581 .39 .24 .84
19.0 3,422 .44 .29 1.07
5.0 2.24 2.0 20.5 2,738 .53 .31 1.14
17.8 2,364 .44 27 .93
23.0 3,286 .67 .41 1.39
17.8 2,964 .43 29 .97
Provides per kilogram of diet: vitamin A, 8,000 IU; cholecalciferol, 1,600 IU; vitamin E, 11.0 mg; riboflavin, 9.0 mg; biotin, 25 mg; pantothenic acid, 11.0 mg; vitamin B-yx, 13 ug; niacin, 26 mg; choline, 900 mg; vitamin K (menadione sodium bisulfite complex), 1.5 mg; folic acid, 15 mg; santoquin, 125 mg. Provides per kilogram of diet: manganese, 55 mg; zinc, 50 mg; copper, 5 mg; iron, 30 mg; and selenium, .1 mg. 3 Calculated from analysis on individual ingredients.
wheat, so that the calorie to protein ratio equalled that of Diet 1; and 4) the protein level was similar to Diet 4 in Experiment 1, but some animal protein sources were added to the diet and the energy level was approximately 7% higher than Diet 1. There was no particular reason for the addition of some animal protein products or the increase in dietary energy for Treatment 4 except to broaden the ingredient base and increase the energy level of the diet. Finishing diets were reduced in protein level similar to Experiment 1 with energy levels altered similar to that described above. The exception was Diet 4 where protein, methionine, and lysine content remained similar to Diet 1, but energy was increased by approximately 7%, as with the starter diet. Tlie composition of diets for Treatments 2, 3, and 4 is shown in Table 2 (Diets 2,3, and 4). The starter diets were fed as crumbles and the finisher diets as pellets. Birds were kept on the starter diets till 3
wk of age at which time five birds per replicate were used for carcass analysis. The birds were then placed on the finisher diets till 42 days of age. At this time birds were weighed, feed intake recorded, and five birds per replicate used for carcass analysis. All remaining birds were used to measure abdominal fat.
Experiment 3 Male, 7-day-old commercial broiler chicks were randomly distributed 10 birds per pen in battery brooders. Four such pens were placed on each of the following dietary treatments for a 2-wk test period: 1) a 16.5% protein, corn and soybean meal diet with all the EAA at NRC (1984) requirement levels and containing 2,650 kcal of ME/kg of diet; 2) the same protein and amino acid levels as Diet 1 (with corn and soybean meal levels kept constant) but with dietary energy level increased to 2,850 kcal ME/kg
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Corn Soybean meal (48% CP) Animal-vegetable blend fat Limestone Calcium phosphate (20% P) Salt (.015% KI) Vitamin mix 1 Mineral mix 2 Alpha floe DL-methionine L-lysine HC1 Wheat shorts Wheat Meat meal Feather meal Blood meal Calculated analysis Protein, %3 Energy, kcal/kg Methionine, %•* Cystine, %3 Lysine, %3
267
BROILER PERFORMANCE AND DIET COMPOSITION TABLE 3. Experimental diets. Experiment 3 1 Ingredients and analysis V'O)
31.7 21.9 17.7 4.3 1.4 1.82 .32 .5 .25 .51 17.1 2.5
31.7 21.9 235 4.3 1.4 1.82 .32 .5 .25 .51 11.60 2.5
31.7 21.9 28.5 4.3 1.4 1.82 .35 .5 .25 .51 6.27 2.5
16.5 2,653 .72 51 151
16.5 2,853 .72 .21 1.21
16.5 3,051 .72 .21 1.21
*For the 19% protein test diets .5% glycine; 1 5 aspartic add, and 1.5 alanine were added to Diets 1,2, and 3 at the expense of glucose, and for the 23% protein test diets 5,42, and 45% of the above amino adds were added. 2 Provides per kilogram of diet: vitamin A, 8,000 IU; cholecalciferol, 1,600 IU; vitamin E, 11.0 mg; riboflavin, 9.0 mg; biotin, 5 5 mg; pantothenic add, 11.0 mg; vitamin Bj2,13 (ig; niacin, 26 mg; choline, 900 mg; vitamin K (menadione sodium bisulfite complex), 1.5 mg; folic add, 1.5 mg; santoquin, 125 mg. Provides per kilogram of diet: manganese, 55 mg; zinc, 50 mg; copper, 5 mg; iron, 30 mg; and selenium, .1 mg. Percentage of amino add mix: L-lysine H Q , 22.0; L-glydne, 24.0; L-phenylalanine, 7.2; L-arginine HC1,19.2; L-leudne, 6.4; L-threonine, 10.4; L-tryptophan, 3.6; L-isoleudne, 4.8; L-valine, 2.4. Calculated from analysis done on individual ingredients.
TABLE 4. Performance of male broilers fed diets containing various levels of dietary lysine and methionine, Experiment 1
Treatment Protein
Methionine
Lysine
23.0 20.5 17.7 23.2
1 2 3 4 SD
19.0 17.8 15.5 18.1
.37 .56 .44 .70
1.34 1.16 .93 1.38
3,072 3,076 3,076 3,082
(tr^
718* 703* 639 b 720*
3,165 3,165 3,168 3,161
1|||
1.04 .95 .76 1.15
43.9
1 2 3 4 SD
2,005* 2,038* l,841 b 2,016* 52.9 b
Feed:gain
Nb'
17.0 .43 .46 .35 .61
Feed intake
Gain
(kcal/kg)
(%) 1 2 3 4 SD
Metabolizable energy
972 965 948 969 26.0 2,757*b 2,884* 2,733 b 2,778*b 695 3,729 3,849 3,681 3,747 86.8
1.35b 1.37b 1.48* 1.35b .02 2.08 b 2.10 b 2.19* 2.10 b .07 1.86b 1.89b 2.00* 1.86b .02
*' Means in columns within time periods with no common superscripts differ significantly (P<.05).
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Corn Soybean meal (48% CP) Glucose monohydrate Animal-vegetable blend fat Limestone Caldum phosphate (20% P) Iodized salt (.015% KI) Vitamin mix 2 Mineral mix 3 DL-methionine Alpha floe Amino add mix 4 Calculated analysis Protein, %5 ME, kcal/kg Methionine. %5 Cystine, %S Lysine, %5
1 2 3 4 SD
l_c
.43 .46 .35 .61
.37 .56 .44 .70
(%) —
1.04 .95 .76 1.15
1.34 1.16 .93 1.38
Methionine Lysine
.
3,165 3,168 3,168 3,161
3,072 3,076 3,076 3,082
(kcal/kg)
Metabolizable energy
197.5
1,439s 1,447" l,299 b l,425 a
48.1
633 a 631 a 568 b 634 a
(g)
Carcass
Means in columns within ages with no common superscripts differ significantly (P<.05).
19.0 17.8 155 18.1
23.0 20.5 17.7 23.2
1 2 3 4
SD
Protein
Treatment
TABLE 5. Carcass composition, Experiment 1
46.7** 45.9 a 40.9 b 44.0 b 2.4
52.1 a 53.0 a 47.8 b 53.5 a 2.1
Carcass fat
2.2 44.2 b 45.5 b 51.6 a 49.2 a 32
330 a 343 a 285 b 328 a 28.0
38.6 b 37.9 b 43.9 s 37.2 b
324 329 373 377 44.8
9.1
75.0 b 74.0 b 88.8 a 71.9 b
(% DM) (g)
101 104 97 103 8.6
(% DM) (g)
Carcass protein
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38.1c 42.8 b 49.3 a 41 .l 1 *
7.8 9.3 10.1 7.5 3.4
(g>
1.87° 2.05 b 258a l.^1* 0.54
1.09 1.33 1.58 1.06 05
(% BW)
Abdominal fat
£
H
1
g
VI
269
BROILER PERFORMANCE AND DIET COMPOSITION
Statistical Analysis Performance and carcass composition data were analyzed using the General Linear Models procedure (SAS Institute, 1985). After analysis of variance, significantly different parameter means were
separated using Duncan's multiple range test (Duncan, 1955).
RESULTS AND DISCUSSION A significant reduction in weight gain and an increased feed:gain ratio were noted when chicks were fed diets with methionine and lysine values reduced by 20% less than NRC (1984) requirement values for the 3-wk-old birds (Table 4). Feed intake was not significantly different for the various treatments. For the 3- to 6-wk period, feed intake, weight gain, and feed:gain ratio were significantly reduced for birds fed the -20% methionine and lysine diet as compared with the diet formulated to NRC (1984) methionine and lysine requirements. The data for 0 to 6 wk, in general, mirrored that reported above. Weight gain was similar for Treatments 1, 2, and 4, where levels of methionine and lysine met NRC (1984) requirement levels, were 20% over stated requirement, or where lysine met requirement levels but methionine was only about 75% of requirement, respectively. Treatment 3,
TABLE 6. Performance of male broilers fed diets differing in calorie to protein ratio, Experiment 2
Treatment levels
Lysine Protein
Methionine •
.37 .53 .44 .67
1 2 3 4 SD
( % )
1.34 1.14 .93 1.39
—
23.0 20.5 17.8 23.0
Metabolizable energy
Calorie: protein Weight ratio gain
(kcal/kg) 0 to 3 wk 3,072 134 134 2,738 2,364 134 3,286 143
Feed intake (g)
741 a 706 a 619 b 741 a 20.7
Feed: gain
l,054 b l,090 a b l,138 a l,101 a b 34.6
1.42c 1.54b 1.84a 1.49** 0.05
3 to 6 wk 1 2 3 4 SD
.43 .43 .39 .44
1 2 3 4 SD a_c
1.04 .97 .84 1.07
19.0 17.8 15.5 19.0
3,164 2,964 2,581 3,422
167 167 167 180
l,464 a l,421 a b l,386 b 1,469s 27.6
3,063 b 2.09 bc 3,053 b 2.15 b 3,377* 2.44 a 2,937b 2.00 c 82.4 0.05 - 0 to 6 wk 4,116 b 1.87= 2,206a 2,127b 4,143 b 1.95b 2,005° 4,515a 2.25 a 2,210" 4,038 b 1.83c 0.04 33.6 78.6
Means in columns within time periods with no common superscripts differ significantly (P<.05).
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of diet; 3) the same protein level and source as above but with energy level increased to 3,050 kcal M E / k g of diet. Dietary energy levels were altered by the substitution of glucose for alpha floe. Additional dietary treatments resulted by supplementing the above three diets with non-essential amino acids (NEAA) (aspartic, alanine, and glycine) to bring crude protein levels up to 19.5 and 23.9%. Composition of the low-protein diets at the three levels of energy are shown in Table 3. The EAA and NEAA supplements are also shown. The experiment was set u p as a factorial arrangement of treatments with three levels of protein and three levels of dietary energy. At 21 days of age, chick weight and feed intake were recorded and three birds per replicate saved for carcass analysis.
270
SUMMERS ET AL. TABLE 7. Carcass composition of male broilers fed diets varying in calorie to protein ratio (Experiment 2)
Treatment
Protein
Metabolizable energy
(%)
(kcal/kg)
23.0 20.5 17.7 23.0
3,072 2,738 2,364 3,286
Calorie: protein ratio
Carcass composition Protein
Fat
(% DM) (g)
(% DM) (g)
53.7^ 55.6b 59.3a 51.1° 3.13
38.4a 33.6 ab 30.4 b 39.5a
3 wk 134 134 134 143
84.6 86.6 78.5 88.8 8.55
6.1
60.5a 52.6 ab 41.6 b 66.8a 12.7
6 wk 1 2 3 4 SD
19.0 17.8 15.5 19.0
3,164 2,964 2,581 3,422
167 167 167 180
48.8 ab 48.4 ab 49.9a 45.8 b
2.9 a_c
261 253 237 247 25.2
43.7 ab 42.7 b 40.9° 46.4a 3.08
237ab 224 b 195 c 252 s 33.5
Means in columns within ages with no common superscripts differ significantly (P<.05).
with methionine and lysine levels 20% lower than stated requirement values, resulted in a weight depression of around 10%, as compared with the other dietary treatments at 3 and 6 wk of age. Percentage carcass fat was greater and percentage carcass protein lower for birds fed the -20% methionine and lysine at 3 wk of age compared with the other dietary treatments (Table 5). Similar results were noted at 6 wk of age for this group. Interestingly, percentage carcass protein was lower and percentage carcass fat higher for the +20% methionine and lysine diet than lower methionine and lysine diets (Treatments 1 and 2) at 6 wk of age. However, although the absolute quantity of fat deposited in the carcass was higher than Treatments 1 and 2, these differences were not significant. Similar amounts of abdominal fat, both on an absolute basis and as a percentage of live weight for these three treatments, would suggest that the extra fat resulting from the higher levels of methionine and lysine (which amounted to approximately 16%), was deposited in areas other than the abdominal region. Similarly, Summers and Leeson (1985) reported an increase in fat content of breast meat with methionine supplementation to a low-protein diet. The diet low in methionine and lysine (Treatment 3, Table 5) resulted in a significantly higher
level of abdominal fat at 6 wk of age than the diet high in methionine and lysine (Treatment 4). However, the results for carcass fat suggest similar levels for these two treatments. These results suggest that abdominal fat is not necessarily a good indicator of carcass fat deposition.
Experiment 2 At 3 wk of age, weight gain and feed:gain ratios of the low methionine and lysine, low-energy diet (Treatment 3) were significantly poorer than that of the other dietary treatments (Table 6). A similar response in bird performance is seen for the various dietary treatments from 3 to 6 wk of age and, as with Experiment 1, the overall 0 to 6 wk data show similar treatment responses. Of interest is the weight gain of the birds in Experiment 2, as compared with Experiment 1. At 6 wk of age, birds in Experiment 2 were heavier than those of Experiment 1 (as a ratio to Experiment 1, these weights were 1.10, 1.05, 1.09, and 1.10 for Treatments 1 through 4, respectively. Although protein and EEA levels were similar for treatments in the two experiments, dietary energy levels differed significantly. It appears that weight gain in both experiments was correlated with EAA intake not energy intake. Although the percentage carcass protein varied significantly at 3 w k of age between
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1 2 3 4 SD
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BROILER PERFORMANCE AND DIET COMPOSITION TABLE 8. Performance of male broilers fed diets varying in level of energy and nonessential amino acids (7 to 21 days of age)
Treatment
Feed intake
Gain -(g)
a-c
Protein
Fat
(g=g)
(% DM) (g)
(% DM) (g)
467 s 442 b 379 c
777* 730 b 702 b
1.66b 1.65b 1.85a
53.5 b 55.8a 56.5 a
104.5a 100.5a 89.1 b
38.6 a 34.7 b 33.0C
75.5 a 62.5 b 52.0C
421 438 429 20.8
724 747 738 38.5
1.73 1.71 1.73 .10
58.4 a 54.6 b 52.8C .62
100.0 98.6 95.7 3.7
33.6C 35.6 b 37.1 a 1.7
57.6C 64.3 b 67.2 a .67
Means in a column within treatments with no common superscripts differ significantly (P<.05).
birds fed the various dietary treatments (Table 7), absolute deposition of protein in the carcasses was similar. However, carcass fat content both on a percentage and on an absolute basis showed major differences between dietary treatments. Similar results were observed with the 6-wk carcass composition data. It is of interest to compare the changes in carcass protein and fat on a percentage basis at 3 and 6 wk of age with the actual deposition of these nutrients. Between 3 and 6 wk of age, percentage carcass protein decreased on the average across all treatments by around 13%, but percentage carcass fat increased by approximately 34%. A similar comparison of deposition of these nutrients at the same ages gave values of a 194% increase for protein and a 313% increase for fat. Such values point out the importance of looking at absolute as well as percentage changes in carcass composition of nutrients, especially when carcass quality studies are being evaluated.
Experiment 3 The protein by energy interaction was not significant. Thus, only the main treatment effects will be discussed. N o significant differences in weight gain, feed intake, or feed:gain ratio were noted for birds fed various dietary protein levels (Table 8). However, these parameters were significantly affected by increased dietary energy levels. As dietary protein level increased, percentage carcass protein was significantly
higher, but the reverse was true for percentage carcass fat. Increasing dietary energy resulted in carcasses with significantly higher percentages of fat and lower percentages of protein. Absolute quantities of carcass protein were similar for the three dietary protein levels and were similar to the absolute quantity of protein found in the carcasses of birds fed various levels of dietary energy with the exception of the low-energy diet. However, significant increases in absolute quantity of carcass fat were noted for those birds fed increased levels of dietary energy. An increased level of dietary protein resulted in carcasses containing less absolute fat. There were marked differences in intake of protein and energy between the various dietary treatments (Table 9). Although feed intake across the main diet treatments varied by approximately 11% (Table 8) protein intake varied by 42% and energy by 27% (Table 9). The NEAA intake varied by approximately 124% for the above comparison, but EAA intake varied by only 10%. These findings substantiate the report of Bedford and Summers (1985), who reported that weight gain and carcass protein appeared to be closely related to total intake of EAA rather than protein or nitrogen intake. The present study suggests that feed intake can be significantly altered by the EAA balance of a diet. This supports the early hypothesis of Lipstein et ah (1975) that birds will "overeat" in an attempt to consume amounts of limiting EAA required for maximum growth. The present data
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Energy, kcal/kg 3,050 2,850 2,650 Protein level, % 23.9 19.5 16.5 SD
Carcass Feed:gain
272
SUMMERS ET AL. TABLE 9. Nutrient intake of male broilers fed diets varying in level of energy and nonessential amino acids Average intake from 7 to 21 days
Treatment
a
NEAA
Energy
(kcal)
155 145 140
2,370 2,081 1,860
13.3 12.5 12.1
11.5 105 10.4
173 146 122
2,111 2,130 2,068
12.5 12.8 12.7
15.0 10.5 6.7
*6'
"""
EAA = essential amino acids; NEAA = nonessential amino acids.
lend further support to the reports of Summers et at (1988) and Parr and Summers (1991) that within certain dietary limits birds produce carcasses of equal lean mass, thus corifirming that birds do eat in an attempt to satisfy their EAA requirements. The present study also confirms the work of Lipstein et al. (1975) that higher energy diets often produce greater weight gain d u e to the fact that increased fat deposition takes place as the bird consumes greater quantities of energy as it attempts to satisfy its EAA requirements. The present study presents evidence that abdominal fat measurements may not be good indicators of total body fat deposition. This substantiates the work of Butterwith (1989), who showed that although broiler neck, thigh, and abdominal fat content remained relatively constant and similar to 30 days of age, abdominal fat content increased markedly after this time. This suggests that the abdominal fat depot areas are in effect a "sink" for excess energy intake and thus could be a poor parameter to measure when studying carcass fat deposition. ACKNOWLEDGMENTS The authors wish to acknowledge the National Research Council, Ottawa, ON, and the Ontario Ministry of Agriculture and Food for financial support. REFERENCES Bartov, I., S. Bomstein, and B. Lipstein, 1974. Effect of calorie to protein ratio on the degree of fatness
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Energy, kcal/kg 3,050 2,850 2,650 Protein level, % 23.9 19.5 16.5
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BROILER PERFORMANCE AND DIET COMPOSITION
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