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Weight Gain, Carcass Yield, and Composition of Large White Male Turkeys Reared to 28 Weeks of Age on Growing and Finishing Diets with Varying Levels of Dietary Protein
Weight Gain, Carcass Yield, and Composition of Large White Male Turkeys Reared to 28 Weeks of Age on Growing and Finishing Diets with Varying Levels of Dietary Protein J. D. SUMMERS and D. SPRATT Department of Animal and Poultry Science, University of Guelph, Guelph, Ontario, Canada NIG 2W1 (Received for publication April 12, 1989) ABSTRACT Male, Large White turkeys were reared to 28 wk of age on diets that varied in protein level after 16 wk of age. The diet composition had little effect on weight gain and feed utilization for birds evaluated at 20, 24, and 28 wk of age. The yield and composition of carcass parts were also affected very little by the dietary treatment. Body weight gain over time was fairly consistent to 28 wk of age. Feed utilization declined, especially between 24 and 28 wk of age. Age had a significant effect on the meat yield of the carcass parts. The percentage yield of breast meat was markedly increased from 20 to 28 wk of age, while the percentage yield of thigh and drumstick meat was reduced. While the absolute yield of edible protein increased with age, there was a noticeable increase in fat deposition, especially in the breast and thigh meat with birds that were 28 wk old versus 24 wk old. (Key words: turkeys, carcass composition, meat yield, protein level, age) 1990 Poultry Science 69:584-591 INTRODUCTION
Leeson and Summers (1980) presented performance and carcass-composition data for Large White turkeys, reared to 24 wk of age, when fed a common diet. Their data suggested that the males had started to plateau in terms of weight gain and feed utilization between 20 and 24 wk of age. Moran et al. (1983), working with three different strains of Large White turkeys, presented data which suggested that the weight gain for males held up fairly well to 24 wk of age; however, feed utilization began to decrease. In view of the interest in heavy-weight turkeys for further processing, the present study was undertaken in order to compare the performance and carcass-composition data for male turkeys reared to 28 wk of age with the characteristics of birds processed at younger ages. Since the yield of edible protein is the ultimate measure of high-quality animal products, protein yields were compared at various weights', and the efficiency of converting dietary protein into edible carcass protein was estimated. MATERIALS AND METHODS
Twenty (Male, Nicholas) Large White turkeys were randomly assigned to each of eight
floor pens at 2 wk of age. Beginning at 4 wk of age, the diets were changed every 4 wk. However, similar diets were fed to all birds until 16 wk of age, at which time half of the birds remained on a diet of 18% protein until 28 wk of age; the other half were fed diets with a protein level that was reduced every 4 wk. The feeding plan used is presented in Table 1. The diets fed are shown in Table 2. The diet fed from 2 to 4 wk of age was steam-pelleted and coarse-crumbled; the diets fed from 4 to 28 wk of age were steampelleted. Glucose monohydrate was included as a source of energy so that the ratio of corn to soybean meal, although not identical, remained similar as the protein levels decreased, thus assuming similar values for amino-acid composition. At the conclusion of each 4-wk period, all birds were weighed individually; and the feed intake was recorded. At 16 wk of age, 6 poults per treatment were used to determine the percentage of edible meat. The eviscerated carcass weight (less giblets) was measured, then each bird was dissected into carcass portions (breast, leg, thigh, wings). These were weighed, then skinned and deboned. Each part was weighed separately. The remaining carcass portion was deboned; the bones and the meat were weighed. These measurements were repeated
584
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GAIN AND MEAT YIELD OF MALE TURKEYS TABLE 1. Percentage of dietary protein fed to Large White, male turkeys to 28 weeks of age Weeks of age Treatment
2 to 4
4 to 8
8 to 12
12 to 16
16 to 20
20 to 24
24 to 28
1 2
30 30
26 26
22 22
18 18
16 18
14 18
12 18
at 20, 24, and 28 wk of age. The crude-protein content (Kjeldahl x 6.25), moisture, and ether extract were determined in duplicate for each meat sample. Statistical Analysis Analyses of variance (Snedecor and Cochran, 1980), using general linear models (SAS Institute, 1982), were conducted on the data. The design of the experiment was completely randomized for each 4-wk period; also, the overall response to 28 wk of age. RESULTS AND DISCUSSION
No significant differences were noted for any of the parameters measured for the
performance data or for the composition and yield data. Thus, standard errors are given with each mean to demonstrate variability. Little difference in weight gain or feed utilization was noted for the diet with 18% protein, versus the treatment with reduced protein (Table 3), compared with the time values (period or todate). The eviscerated carcass yield paralleled the live body weights, since little difference was noted between the dietary treatments (Table 4). Also, little difference in the percentage yields of the meat was noted with the different age groups beyond 16 wk of age. The yield of breast meat increased with age, reaching approximately 52% of the total carcass meat at 28 wk of age. However, no significant difference in yield between the
TABLE 2. Composition of the experimental diets Weeks of ;age Ingredient (%) Ground yellow corn Soybean meal (48% CP) Animal-vegetable fat blend Glucose monohydrate Calcium phosphate (20% CP) Limestone Iodized salt Vitamin mix1 Mineral mix 2 DL-methionine Robenz Alpha floe Analyses Determined CP, % Calculated ME, kcal per kg Methionine, % Lysine, %
2 to 4
8 to 12
12 to 16
16 to 20
20 to 24
24 to 28
21.4 58.15
31.21 48.08
41.29 38.00
51.42 27.80
49.82 24.43
42.05 21.50
40.05 17.50
6.0 8.41 2.70 1.25 .50 1.00 .50 .30 .05
5.70 8.76 2.70 1.25 .50 1.00 .50 .25 .05
2.00 12.31 2.70 1.25 .50 1.00 .50 .20 .05
2.00 13.31 2.00 1.25 .50 1.00 .50 .17 .05
100.00
100.00
100.00
100.00
3.00 17.74 1.50 1.25 .50 1.00 .50 .16 .05 .05 100.00
5.55 25.00 1.50 1.25 .50 1.00 .50 .15 .05 .95 100.00
5.55 29.00 1.50 1.25 .50 1.00 .50 .15 .05 2.95 100.00
30.0
25.7
22.0
17.9
16.10
14.02
11.93
2,800 .75 1.90
4 to 8
3,004 .65 1.60
2,920 .55 1.30
3,104
3,020 .47 .99
3,205 .43 .88
3,168 .38 .77
.35 .64
'Vitamin mix added (per kilogram of diet): 8,000 IU, vitamin A; 1,600 ICU, vitamin D3; 11.0 mg, vitamin E; 9 mg, riboflavin; 13 jig, vitamin B12; 26.0 mg, niacin; 900 mg, choline chloride; 1.5 mg, vitamin K; 1.5 mg, folic acid; .2 mg, biotin; and 125 mg, ethoxyquin. ^Mineral mix added (per kilogram of diet): 55.0 mg, manganese;. 1 mg, selenium; 50 mg, zinc; 5 mg, copper; and 30 mg,
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SUMMERS AND SPRATT TABLE 3. Performance of Large White, male turkeys to 28 weeks of age (all birds fed similar diets to 16 weeks)1 Weeks 16 to 20
Treatment2
Gain
Feed:gain ratio
Feed intake Crl
Weeks 16 to 20 1 2
2,702 (± 325) 2,634 (± 144)
12,317 (± 482) 11,746 (± 683)
4.71 (± .42) 4.46 (± .11)
Weeks 20 to 24 1 2
3,536 (± 231) 3,712 (± 305)
13,913 (± 606) 13,825 (± 182)
3.95 (± .09) 3.76 (± .36)
Weeks 24 to 28 1 2
2,605 (±311) 2,729 (± 226)
12,763 (± 875) 15,107 (± 94) To date
4.93 (± .25) 5.57 (± .43)
BW Weeks 16 to 20 1 2 Weeks 20 to 24 1 2 Weeks 24 to 28 1 2
Feed:gain ratio
Feed intake _._
f»
(rr/ri
13,895 (± 166) 14,006 (± 225)
39,859 (± 448) 39,474 (± 1016)
2.93 (± .04) 2.88 (± .04)
17,412 (± 146) 17,925 (± 218)
54,043 (± 1424) 53,334 (± 157)
3.16 (± .06) 3.03 (± .03)
20,017 (± 457) 20,654 (± 444)
66,806 (± 229) 68,441 (± 251)
3.39 (± .04) 3.36 (± .06)
*X ± SE. treatment 1 = birds fed diets containing 16,14, and 12% protein, respectively,at 16,20, and 24 wk of age. Treatment 2 = birds kept on a diet of 18% protein from 12 to 28 wk of age.
TABLE 4. Carcass yield at various ages for Large White, male turkeys fed diets with two levels of dietary protein Weeks of age Treatment2
16 3
20
24
28
Eviscerated carcass weight (g), less the giblets 8,737
(± 208)
9,957 10,244
(± 694) (± 550)
13,776 14,139
(± 200) (± 240)
15,849 16,069
(± 451) (±487)
Carcass as a percentage of body weight — 79.3
5,332
(± 1.05)
(± 159)
61.0 (± .58)
77.3 78.3
(± .77)
80.3
(± .42)
(± .57)
79.9
(± 1.51)
—
6,454 6,758
Total carcass meat (g), less skin -^-^—
(± 514) 8,635 (± 145) (± 349) 8,974 (± 145) — Meat as a percentage of the eviscerated carcass 64.6 (± 1.12) 62.7 (± .56) 66.0 (± .68) 63.5 (± .35) ————^—
2,367
(± 66.4)
27.3 (± .63)
(± 162.2)
4,623
(± 103.9)
3,285
(± 148.6)
4,548
(± 89.7)
Bone as a percentage of the eviscerated carcass 33.4 32.2
10,049 10,347 63.4 64.3
(± .22) (± .57) (± 310) (±445) (± .41) (± -93)
Total carcass bone (g) _ _ _ _ _ _
3,296 —
79.3 79.1
(± 1.07) (± .81)
33.6 32.2
(± .61) (± .32)
5,149 5,077 32.5 31.7
(± 145.4) (± 78.4) (± 77) (± .56)
'X ± SE. treatment 1 = birds fed diets containing 16, 14 and 12% protein at 16, 20 and 24 wk of age; Treatment 2 = birds kept on a diet of 18% protein from 12 till 28 wk of age. 3 All birds fed the same 18% protein diet.
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GAIN AND MEAT YIELD OF MALE TURKEYS TABLE 5. Breast yield of Large White, male turkeys finished on two diets with different levels of dietary protein1 Weeks of age Treatment
20
16
24
28
— — Breast meat (g), less skin — — 2,277
(± .59)
2,893 3,068
(± 277.2) (± (± 207.4) 207.4)
4,183 4,470 4,470
(± 82.4) (± 137.4) (± 137.4)
5,201 5,346
(± 137.6) (± 233.0)
Breast meat as a percentage of the total eviscerated carcass ^—— 26.0
(± .86)
42.6
(± .84)
219
(± 14.4)
28.8 (± .91) 30.4 (± .42) 29.8 (± .48) 31.6 (± .76) —— Breast meat as a percentage of total carcass meat 44.6 452. 257 280
(± 1-12) (± -81) (± 51.1) (± 58.6)
32.8 (± -51) 33.2 (± -59) — — —
48.5 (± .88) 49.8 (± 1.01) Breast skin (g) 510 495
51.8 51.7
(± 31.2) (± 40.1)
603 623
(± -75) (± -89) (± 40.2) (± 87.7)
Skin as a percentage of the total breast 7.3
(± .57)
6.8 6.9
(± .94) (± 1.46)
9.6 8.9
(± .59) (± .94)
9.2 9.3
(± -79) (± 1.69)
————• Breast bone (g) ———^^—. 461
15.6 l
(± 21.6)
(± 1.04)
462 495 13.2 13.0
(± 32.1)
571
(± 21.7)
(± 32.2)
602
(± 31.4)
Bone as a percentage of the total breast < (± 1.45) (± .82)
10.8 10.8
(± 52.0) (± 36.6)
746 671 11.3 10.2
(± .40) (± .63)
(± -55) (± .82)
\ ± SE.
•Treatment 1 = birds fed diets containing 16,14, and 12% protein, respectively, at 16,20, and 24 wk of age; Treatment 2 = birds kept ( diet of 18% protein from 12 until 28 wk of age.
TABLE 6. Thigh level of Large White, male turkeys finished on diets with two levels of dietary protein Weeks of age Treatment2
16
20
24
28
— - — — — — ^ — — ^ — — — Thigh meat (g), less skin 1,056 (± 25.4) 1,299 (± 102) 1,630 (± 66.3) 1,317 (± 45.8) 1,584 (± 35.4)
^
— 1,797 1,861
— (± 66.7) (± 72.6)
' Thigh meat as a percentage of total eviscerated carcass • 12.1
(± .3)
19.8
(± .53)
20.2 19.6
(± .32) (±.44)
81.3
(± 3.9)
91.0 725
(± 12.0) (± 5.95)
6.2
(± .33)
5.8 4.6
146.4
(± 4.4)
11.2
(± .42)
13.0 12.9
(± .24) (± .30)
11.8 11.2
11.4 11.6
(±.40) (±.24)
(±.57) (± -17)
17.9 18.0
(± .63) (± -32)
(± 14.8) (± 7.75)
152.5 158.3
(± 9.8) (± 11-9)
(± .43) (± .09)
^— Thigh meat as a percentage of total carcass meat — 18.9 17.6 • Thigh skin (g) • 150.0 145.0
Skin as a percentage of the total thigh <
151 165
(± -73) (±.28) (± 4.57) (± 5.57)
7.8 (± -93) (± .48) 7.6 Thigh bone (g) • 163 170
(± 4.94) (± 6.19)
7.2 7.3
172 180
(± -81) (± -89) (± 4.94) (± 8.85)
Bone as a percentage of the total thigh • 10.0 10.6
(± .71) (± .47)
8.4 8.9
(± .20) (± .22)
8.0 8.2
(± .23) (± .26)
'X ± SE. "Treatment 1 = birds fed diets containing 16,14, and 12% protein, respectively, at 16,20, and 24 wk of age; Treatment 2 = birds kept on a diet of 18% protein from 12 until 28 wk of age.
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SUMMERS AND SPRATT TABLE 7. Drumstick yield of Large White, male turkeys finished on diets with two dietary protein levels. Weeks of age
Treatment
20
16
24
28
Drumstick meat (g), less skin 1 2
804
877 (± 65.6) 1,146 (± 30.7) 1,299 932 (± 48.8) 1,154 (± 35.2) 1,271 Drumstick meat as a percentage of the total eviscerated carcass 9.2 (± .34) 8.8 (± .26) 8.3 (± .17) 8.2 9.1 (± .34) 8.2 (± .17) 7.9 Drumstick meat as a percentage of the carcass meat 15.2 (± .58) 13.7 (± .46) 13.3 (± .22) 12.9 13.8 (± .44) 12.9 (± .32) 12.2 Drumstick skin (g) 79.4 (± 3.16) 89.3 (± 8.8) 144.2 (± 12.5) 145.0 90.5 (± 12.8) 139.2 (± 12.0) 158.3 Skin as a percentage of the total drumstick 7.3 (± .45) 7.3 (± .87) 9.3 (±1.06) 8.3 6.8 (± 1.10) 8.8 (± .96) 9.2 — ^ — — — — — — — — — — Drumstick bone (g) 229 (± 7.4) 257.8 (± 4.2) 270.8 (± 6.2) 319.2 277.2 (± 4.9) 288.3 (±15.0) 304.2 Bone as a percentage of the total drumstick 21.5 (± .73) 21.3 (± 1.3) 17.5 (± .5) 18.1 21.4 (± .92) 18.2 (±.64) 17.7
1 2 1 2 1 2 1 2 1 2 1 2
(± 20.4)
(± 72.2) (± 92.9) (± .28) (± .24) (± .39) (± .42) (± 5.0) (± 11.9) (± .66) (± 1.0) (± 9.61) (± 8.3) (± .37) (± .66)
'X ± SE. treatment 1 = birds fed diets containing 16,14, and 12% protein, respectively, at 16,20, and 24 wk of age; Treatment 2 = birds kept on a diet of 18% protein from 12 to 28 wk of age.
TABLE 8. Wing yield of Large White, male turkeys finished on diets with two levels of dietary protein Weeks of age Treatment2
16
20
24
28
Wing meat (g), including skin 1 2
629
(± 12.8)
1 2
7.2 (± .07)
1 2
11.8 (± .15)
1 2
39.6 (± 9.9)
1 2
38.6 (± .96) l
803 (± 55.5) 1,123 (± 27.8) 1,103 799 (± 20.6) 1,168 (± 41.6) 1,168 Wing meat as a percentage of the eviscerated carcass 8.1 (± .43) 8.2 (± .18) 6.9 7.9 (± .39) 8.3 (± .37) 7.3 Wing meat as a percentage of the carcass meat 12.6 (± .68) 13.0 (± .21) 10.9 11.9 (± .52) 13.0 (± .59) 11.3 Wing bone (g) 401 (± 11.7) 412 (± 13.8) 478 440 (± 13.8) 460 (± 16.4) 509 Bone as a percentage of total wing 33.5 (± 1.72) 26.8 (± .62) 30.2 35.2 (± 1.02) 28.3 (± .70) 30.5
(± 63.9) (± 47.2) (± .21) (± .22) (± .32) (± .33) (± 20.8) (± 8.31) (± 1.15) (± .72)
X ± SE. treatment 1 = birds fed diets containing 16,14, and 12% protein, respectively, at 16,20, and 24 wk of age; Treatment 2 = birds kept on a diet of 18% protein from 12 until 28 wk of age.
GAIN AND MEAT YIELD OF MALE TURKEYS
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TABLE 9. Composition of the breast meat, less skin1 Weeks of age Treatment2
16
20
1 2
93.4 (± .37)
92.4 94.2
1 2
6.3 (± .44)
6.0 6.1
1 2
547
1 2
(± 34.9)
37.7 (± 4.7)
24 Protein (percentage of dry weight) (± 2.45) 89.9 (± 1.70) (± .67) 89.5 (± 3.70) • Fat (percentage of dry weight) (± .45) 9.5 (± 1.81) (± .34) 9.2 (± 3.79) • Total protein (g) (± 58.7) 980 (± 25.1) (± 46.6) 1,049 (± 46.3) • Total fat (g) (± 6.3) 97 (± 13.1) (± 7.2) 111 (± 19.9)
688 735 45 49
28 87.3 (± 2.7) 88.1 (± 3.52) 11.1 (± 2.90) 11.1 (± 3.3) 1,199 1,221
(± 37.2) (± 53.6)
131 141
(± 15.1) (± 20.9)
l
X ± SE. ^Treatment 1 = birds fed diets containing 16,14, and 12% protein, respectively, at 16,20, and 24 wk of age; Treatment 2 = birds kept on a diet of 18% from 12 until 28 weeks of age.
dietary treatments was noted (Table 5). Skin as a percentage of breast weight increased with age, while the percentage of bone decreased, The dietary treatment had little effect on the yield of thigh, drumstick, or wing meat or on the bone yields (Tables 6, 7, and 8). However, small differences were noted between the various age groups. The composition of the breast, thigh, and drumstick meat was influenced very little by
the dietary treatments (Tables 9, 10, and 11). However, composition differences were noted among the various age groups. An increase in fat deposition was particularly noticeable for breast and thigh meat at 24 and 28 wk of age. The efficiency of converting dietary protein into edible carcass protein was estimated (Table 12). Although the values shown were calculated from limited and variable data, they demonstrate that with the low-protein diets, the
TABLE 10. Composition of the thigh meat, less skin Weeks of age Treatment
2
16
20
1 2
76.7 (± 2.01)
79.9 76.2
1 2
20.4 (± 1.74)
18.3 22.0
1 2
205
(± 8.06)
264 253
1 2
56
(± 3.26)
60 74
:
28
24 Protein (percentage of dry weight) (± 1.95) 69.2 (± 3.07) (± 3.10) 70.4 (± 5.5) • Fat (percentage of dry weight) (± 2.79) 30.0 (± 3.99) (± 2.98) 27.8 (± 4.82) • Total protein (g) (± 21.0) 324 (± 14.07) (± 17.6) 316 (± 12.25) (± 9.22) (± 12.2)
Total fat (g) 142 (± 20.2) 132 (± 29.4)
67.8 (± 3.54) 67.8 (± 4.2) 33.1 (± 2.8) 30.9 (± 4.8) 345 364
(± 11.8) (± 20.2)
172 170
(± 20.7) (± 31.3)
X ± SE. treatment 1 = birds fed diets containing 16,14, and 12% protein, respectively, at 16,20, and 24 wk of age; Treatment 2 = birds kept on a diet of 18% protein from 12 until 28 wk of age.
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SUMMERS AND SPRATT TABLE 11. Composition of the drumstick meat, less skin Weeks of age
Treatment2
20
16
24
28
1 2
77.7 (± 1.24)
74.8 (± 2.79) 74.8 (± 4.0)
71.9 (± 3.5) 75.2 (± 2.6)
74.1 (± 1.70) 72.7 (± 2.43)
1 2
19.7 (± 0.85)
24.4 (± 2.98) 24.0 (± 4.10)
24.7 (± 2.04) 23.4 (± 3.3)
25.1 (± 1.68) 26.3 (± 2.75)
1 2
149
(± 3.54)
184 169
(± 16.7) (± 19.2)
216 232
(± 4.66) (± 9.2)
249 246
(± 13.1) (± 17.0)
1 2
38
(± 2.12)
53 52
(± 7.3) (± 9.2)
75 72
(± 8.44) (± 10.8)
86 89
(± 9.51) (± 11.4)
*X ± SE. treatment 1 = birds fed diets containing 16,14, and 12% protein, respectively, at 16,20, and 24 wk of age; Treatment 2 = birds kept on a diet of 18% protein from 12 until 28 wk of age.
TABLE 12.. Edible carcass protein as a percentage of dietary protein intake Weeks of age 1 2
2 to 16
16 to 20
20 to 24
24 to 28
15.3
12.3 12.3 12.1
19.4 19.4 17.7
17.9
2 to 20
2 to 24
2 to 28
14.6 UA
15.6 15£
15.9 13_8
Weeks of age 1 2
Includes only the protein from the breast, thigh, and drumstick meat (which from previous tables makes up over 80% of the total carcass meat). treatment 1 = birds fed diets containing 16,14, and 12% protein, respectively, at 16,20, and 24 wk of age; Treatment 2 = birds kept on a diet of 18% protein from 12 until 28 wk of age.
turkey maintains a fairly efficient utilization of protein even up to 28 wk of age. However, for the higher-protein diets, the efficiency of protein utilization declined after 20 wk of age
and was markedly reduced from 24 to 28 wk of age. The absolute intake of protein for the 24- to 28-wk period was almost twice as high (2,719 versus 1,532 g) for the high-protein diet
TABLE 13. Yield of the breast, thigh, and drumstick meat (less skin) at 20 and 28 weeks of age, average of the two dietary treatments Weeks of age
Carcass weight
Carcass meat
Breast meat
Thigh meat
28
15,959
10,198
(g) — — — — — — — — — 5,274 1,829 1,285
63.9
20
10,100
6,606
2,981
65.4
1,308
Drumstick meat
905
Carcass
Percentage of meat yield Breast Thigh Drumstick (Percentage of carcass weight) • 51.8 18.0 12.6
44.9
19.9
13.8
GAIN AND MEAT YIELD OF MALE TURKEYS
versus the low-protein diet. As is obvious from the performance and carcass data, the increased protein intake did very little to enhance the value of the carcass produced. Since further processing is of increasing importance, especially with heavy-weight toms, the meat yield from 20- and 28-wk-old birds was compared. Table 13 shows the difference in absolute carcass meat yield for the two age groups, when averaged across dietary treatments. The meat yield for breast, thigh, and drumstick meat made up approximately 78% of the total carcass meat at 20 wk of age, increasing to around 82% at 28 wk of age. Also shown is the percentage yield of the various carcass portions. The total meat yield from the carcasses decreased slightly from 20 to 28 wk of age (63.9% versus 65.4%). The percentage of breast meat showed a marked increase (7%) from 20 to 28 wk of age, while yield of thigh and drumstick meat decreased as a percentage of the total meat yield for the same period. Looking at the various portions for the increased yield of meat between 20 and 28 wk of age, 63.8% of this increased yield was breast meat; the yield of thigh meat was 14.5% and that of drumstick meat was 10.6%. Although the increased yield of breast meat between 20 and 28 wk may substantially increase the value of the carcass, that has to be weighed against the extra feed consumed during the period as well as the increased overhead costs and higher mortality. Approximately 70% more feed was consumed between 20 and 28 wk, producing only 46% more BW (Table 3). However, this 46% increase in BW resulted in a meat yield that was 65% higher
591
and obviously was greater than 65% in terms of the edible protein yield. The present study yielded data showing increased yields for various carcass parts as the age of turkeys increased. However, these data must be evaluated in a particular situation in order to judge the economics of keeping male turkeys to heavier processing weights. Blair et al. (1989 a,b) studied similar parameters with three strains of turkeys. Many of their findings were similar to those reported from the present experiment. ACKNOWLEDGMENTS
The authors wish to acknowledge the financial support of the Ministry of Agriculture and Food and the Natural Sciences and Engineering Research Council of Canada. REFERENCES Blair, M. E., L. M. Potter, and R. M. Hulet, 1989a. Effects of dietary protein and added fat on turkey varying in strain, sex and age. 1. Live characteristics. Poultry Sci. 68:278-286. Blair, M. E., L. M. Potter, and R. M. Hulet, 1989b. Effects of dietary protein and added fat on turkeys varying in strain, sex and age. 2. Carcass characteristics. Poultry Sci. 68:287-296. Leeson, S., and J. D. Summers, 1980. Production and carcass characteristics of the large white turkey. Poultry Sci. 59:1237-1245. Moran, E. T., Jr., L. M. Poste, P. R. Ferket, and V. Agar, 1984. Response of large torn turkeys differing in growth characteristics to divergent feeding systems: Performance, carcass quality and sensory evaluation. Poultry Sci. 63:1778-1792. SAS Institute, 1982. SAS User's Guide Statistics, SAS Inst. Inc., Cary, NC. Snedecor, G. W., and W. G. Cochran, 1980. Statistical Methods. 7th Ed. The Iowa State University Press, Ames, IA.
Leeson and Summers (1980) presented performance and carcass-composition data for Large White turkeys, reared to 24 wk of age, when fed a common diet. Their data suggested that the males had started to plateau in terms of weight gain and feed utilization between 20 and 24 wk of age. Moran et al. (1983), working with three different strains of Large White turkeys, presented data which suggested that the weight gain for males held up fairly well to 24 wk of age; however, feed utilization began to decrease. In view of the interest in heavy-weight turkeys for further processing, the present study was undertaken in order to compare the performance and carcass-composition data for male turkeys reared to 28 wk of age with the characteristics of birds processed at younger ages. Since the yield of edible protein is the ultimate measure of high-quality animal products, protein yields were compared at various weights', and the efficiency of converting dietary protein into edible carcass protein was estimated. MATERIALS AND METHODS
Twenty (Male, Nicholas) Large White turkeys were randomly assigned to each of eight
floor pens at 2 wk of age. Beginning at 4 wk of age, the diets were changed every 4 wk. However, similar diets were fed to all birds until 16 wk of age, at which time half of the birds remained on a diet of 18% protein until 28 wk of age; the other half were fed diets with a protein level that was reduced every 4 wk. The feeding plan used is presented in Table 1. The diets fed are shown in Table 2. The diet fed from 2 to 4 wk of age was steam-pelleted and coarse-crumbled; the diets fed from 4 to 28 wk of age were steampelleted. Glucose monohydrate was included as a source of energy so that the ratio of corn to soybean meal, although not identical, remained similar as the protein levels decreased, thus assuming similar values for amino-acid composition. At the conclusion of each 4-wk period, all birds were weighed individually; and the feed intake was recorded. At 16 wk of age, 6 poults per treatment were used to determine the percentage of edible meat. The eviscerated carcass weight (less giblets) was measured, then each bird was dissected into carcass portions (breast, leg, thigh, wings). These were weighed, then skinned and deboned. Each part was weighed separately. The remaining carcass portion was deboned; the bones and the meat were weighed. These measurements were repeated
584
585
GAIN AND MEAT YIELD OF MALE TURKEYS TABLE 1. Percentage of dietary protein fed to Large White, male turkeys to 28 weeks of age Weeks of age Treatment
2 to 4
4 to 8
8 to 12
12 to 16
16 to 20
20 to 24
24 to 28
1 2
30 30
26 26
22 22
18 18
16 18
14 18
12 18
at 20, 24, and 28 wk of age. The crude-protein content (Kjeldahl x 6.25), moisture, and ether extract were determined in duplicate for each meat sample. Statistical Analysis Analyses of variance (Snedecor and Cochran, 1980), using general linear models (SAS Institute, 1982), were conducted on the data. The design of the experiment was completely randomized for each 4-wk period; also, the overall response to 28 wk of age. RESULTS AND DISCUSSION
No significant differences were noted for any of the parameters measured for the
performance data or for the composition and yield data. Thus, standard errors are given with each mean to demonstrate variability. Little difference in weight gain or feed utilization was noted for the diet with 18% protein, versus the treatment with reduced protein (Table 3), compared with the time values (period or todate). The eviscerated carcass yield paralleled the live body weights, since little difference was noted between the dietary treatments (Table 4). Also, little difference in the percentage yields of the meat was noted with the different age groups beyond 16 wk of age. The yield of breast meat increased with age, reaching approximately 52% of the total carcass meat at 28 wk of age. However, no significant difference in yield between the
TABLE 2. Composition of the experimental diets Weeks of ;age Ingredient (%) Ground yellow corn Soybean meal (48% CP) Animal-vegetable fat blend Glucose monohydrate Calcium phosphate (20% CP) Limestone Iodized salt Vitamin mix1 Mineral mix 2 DL-methionine Robenz Alpha floe Analyses Determined CP, % Calculated ME, kcal per kg Methionine, % Lysine, %
2 to 4
8 to 12
12 to 16
16 to 20
20 to 24
24 to 28
21.4 58.15
31.21 48.08
41.29 38.00
51.42 27.80
49.82 24.43
42.05 21.50
40.05 17.50
6.0 8.41 2.70 1.25 .50 1.00 .50 .30 .05
5.70 8.76 2.70 1.25 .50 1.00 .50 .25 .05
2.00 12.31 2.70 1.25 .50 1.00 .50 .20 .05
2.00 13.31 2.00 1.25 .50 1.00 .50 .17 .05
100.00
100.00
100.00
100.00
3.00 17.74 1.50 1.25 .50 1.00 .50 .16 .05 .05 100.00
5.55 25.00 1.50 1.25 .50 1.00 .50 .15 .05 .95 100.00
5.55 29.00 1.50 1.25 .50 1.00 .50 .15 .05 2.95 100.00
30.0
25.7
22.0
17.9
16.10
14.02
11.93
2,800 .75 1.90
4 to 8
3,004 .65 1.60
2,920 .55 1.30
3,104
3,020 .47 .99
3,205 .43 .88
3,168 .38 .77
.35 .64
'Vitamin mix added (per kilogram of diet): 8,000 IU, vitamin A; 1,600 ICU, vitamin D3; 11.0 mg, vitamin E; 9 mg, riboflavin; 13 jig, vitamin B12; 26.0 mg, niacin; 900 mg, choline chloride; 1.5 mg, vitamin K; 1.5 mg, folic acid; .2 mg, biotin; and 125 mg, ethoxyquin. ^Mineral mix added (per kilogram of diet): 55.0 mg, manganese;. 1 mg, selenium; 50 mg, zinc; 5 mg, copper; and 30 mg,
586
SUMMERS AND SPRATT TABLE 3. Performance of Large White, male turkeys to 28 weeks of age (all birds fed similar diets to 16 weeks)1 Weeks 16 to 20
Treatment2
Gain
Feed:gain ratio
Feed intake Crl
Weeks 16 to 20 1 2
2,702 (± 325) 2,634 (± 144)
12,317 (± 482) 11,746 (± 683)
4.71 (± .42) 4.46 (± .11)
Weeks 20 to 24 1 2
3,536 (± 231) 3,712 (± 305)
13,913 (± 606) 13,825 (± 182)
3.95 (± .09) 3.76 (± .36)
Weeks 24 to 28 1 2
2,605 (±311) 2,729 (± 226)
12,763 (± 875) 15,107 (± 94) To date
4.93 (± .25) 5.57 (± .43)
BW Weeks 16 to 20 1 2 Weeks 20 to 24 1 2 Weeks 24 to 28 1 2
Feed:gain ratio
Feed intake _._
f»
(rr/ri
13,895 (± 166) 14,006 (± 225)
39,859 (± 448) 39,474 (± 1016)
2.93 (± .04) 2.88 (± .04)
17,412 (± 146) 17,925 (± 218)
54,043 (± 1424) 53,334 (± 157)
3.16 (± .06) 3.03 (± .03)
20,017 (± 457) 20,654 (± 444)
66,806 (± 229) 68,441 (± 251)
3.39 (± .04) 3.36 (± .06)
*X ± SE. treatment 1 = birds fed diets containing 16,14, and 12% protein, respectively,at 16,20, and 24 wk of age. Treatment 2 = birds kept on a diet of 18% protein from 12 to 28 wk of age.
TABLE 4. Carcass yield at various ages for Large White, male turkeys fed diets with two levels of dietary protein Weeks of age Treatment2
16 3
20
24
28
Eviscerated carcass weight (g), less the giblets 8,737
(± 208)
9,957 10,244
(± 694) (± 550)
13,776 14,139
(± 200) (± 240)
15,849 16,069
(± 451) (±487)
Carcass as a percentage of body weight — 79.3
5,332
(± 1.05)
(± 159)
61.0 (± .58)
77.3 78.3
(± .77)
80.3
(± .42)
(± .57)
79.9
(± 1.51)
—
6,454 6,758
Total carcass meat (g), less skin -^-^—
(± 514) 8,635 (± 145) (± 349) 8,974 (± 145) — Meat as a percentage of the eviscerated carcass 64.6 (± 1.12) 62.7 (± .56) 66.0 (± .68) 63.5 (± .35) ————^—
2,367
(± 66.4)
27.3 (± .63)
(± 162.2)
4,623
(± 103.9)
3,285
(± 148.6)
4,548
(± 89.7)
Bone as a percentage of the eviscerated carcass 33.4 32.2
10,049 10,347 63.4 64.3
(± .22) (± .57) (± 310) (±445) (± .41) (± -93)
Total carcass bone (g) _ _ _ _ _ _
3,296 —
79.3 79.1
(± 1.07) (± .81)
33.6 32.2
(± .61) (± .32)
5,149 5,077 32.5 31.7
(± 145.4) (± 78.4) (± 77) (± .56)
'X ± SE. treatment 1 = birds fed diets containing 16, 14 and 12% protein at 16, 20 and 24 wk of age; Treatment 2 = birds kept on a diet of 18% protein from 12 till 28 wk of age. 3 All birds fed the same 18% protein diet.
587
GAIN AND MEAT YIELD OF MALE TURKEYS TABLE 5. Breast yield of Large White, male turkeys finished on two diets with different levels of dietary protein1 Weeks of age Treatment
20
16
24
28
— — Breast meat (g), less skin — — 2,277
(± .59)
2,893 3,068
(± 277.2) (± (± 207.4) 207.4)
4,183 4,470 4,470
(± 82.4) (± 137.4) (± 137.4)
5,201 5,346
(± 137.6) (± 233.0)
Breast meat as a percentage of the total eviscerated carcass ^—— 26.0
(± .86)
42.6
(± .84)
219
(± 14.4)
28.8 (± .91) 30.4 (± .42) 29.8 (± .48) 31.6 (± .76) —— Breast meat as a percentage of total carcass meat 44.6 452. 257 280
(± 1-12) (± -81) (± 51.1) (± 58.6)
32.8 (± -51) 33.2 (± -59) — — —
48.5 (± .88) 49.8 (± 1.01) Breast skin (g) 510 495
51.8 51.7
(± 31.2) (± 40.1)
603 623
(± -75) (± -89) (± 40.2) (± 87.7)
Skin as a percentage of the total breast 7.3
(± .57)
6.8 6.9
(± .94) (± 1.46)
9.6 8.9
(± .59) (± .94)
9.2 9.3
(± -79) (± 1.69)
————• Breast bone (g) ———^^—. 461
15.6 l
(± 21.6)
(± 1.04)
462 495 13.2 13.0
(± 32.1)
571
(± 21.7)
(± 32.2)
602
(± 31.4)
Bone as a percentage of the total breast < (± 1.45) (± .82)
10.8 10.8
(± 52.0) (± 36.6)
746 671 11.3 10.2
(± .40) (± .63)
(± -55) (± .82)
\ ± SE.
•Treatment 1 = birds fed diets containing 16,14, and 12% protein, respectively, at 16,20, and 24 wk of age; Treatment 2 = birds kept ( diet of 18% protein from 12 until 28 wk of age.
TABLE 6. Thigh level of Large White, male turkeys finished on diets with two levels of dietary protein Weeks of age Treatment2
16
20
24
28
— - — — — — ^ — — ^ — — — Thigh meat (g), less skin 1,056 (± 25.4) 1,299 (± 102) 1,630 (± 66.3) 1,317 (± 45.8) 1,584 (± 35.4)
^
— 1,797 1,861
— (± 66.7) (± 72.6)
' Thigh meat as a percentage of total eviscerated carcass • 12.1
(± .3)
19.8
(± .53)
20.2 19.6
(± .32) (±.44)
81.3
(± 3.9)
91.0 725
(± 12.0) (± 5.95)
6.2
(± .33)
5.8 4.6
146.4
(± 4.4)
11.2
(± .42)
13.0 12.9
(± .24) (± .30)
11.8 11.2
11.4 11.6
(±.40) (±.24)
(±.57) (± -17)
17.9 18.0
(± .63) (± -32)
(± 14.8) (± 7.75)
152.5 158.3
(± 9.8) (± 11-9)
(± .43) (± .09)
^— Thigh meat as a percentage of total carcass meat — 18.9 17.6 • Thigh skin (g) • 150.0 145.0
Skin as a percentage of the total thigh <
151 165
(± -73) (±.28) (± 4.57) (± 5.57)
7.8 (± -93) (± .48) 7.6 Thigh bone (g) • 163 170
(± 4.94) (± 6.19)
7.2 7.3
172 180
(± -81) (± -89) (± 4.94) (± 8.85)
Bone as a percentage of the total thigh • 10.0 10.6
(± .71) (± .47)
8.4 8.9
(± .20) (± .22)
8.0 8.2
(± .23) (± .26)
'X ± SE. "Treatment 1 = birds fed diets containing 16,14, and 12% protein, respectively, at 16,20, and 24 wk of age; Treatment 2 = birds kept on a diet of 18% protein from 12 until 28 wk of age.
588
SUMMERS AND SPRATT TABLE 7. Drumstick yield of Large White, male turkeys finished on diets with two dietary protein levels. Weeks of age
Treatment
20
16
24
28
Drumstick meat (g), less skin 1 2
804
877 (± 65.6) 1,146 (± 30.7) 1,299 932 (± 48.8) 1,154 (± 35.2) 1,271 Drumstick meat as a percentage of the total eviscerated carcass 9.2 (± .34) 8.8 (± .26) 8.3 (± .17) 8.2 9.1 (± .34) 8.2 (± .17) 7.9 Drumstick meat as a percentage of the carcass meat 15.2 (± .58) 13.7 (± .46) 13.3 (± .22) 12.9 13.8 (± .44) 12.9 (± .32) 12.2 Drumstick skin (g) 79.4 (± 3.16) 89.3 (± 8.8) 144.2 (± 12.5) 145.0 90.5 (± 12.8) 139.2 (± 12.0) 158.3 Skin as a percentage of the total drumstick 7.3 (± .45) 7.3 (± .87) 9.3 (±1.06) 8.3 6.8 (± 1.10) 8.8 (± .96) 9.2 — ^ — — — — — — — — — — Drumstick bone (g) 229 (± 7.4) 257.8 (± 4.2) 270.8 (± 6.2) 319.2 277.2 (± 4.9) 288.3 (±15.0) 304.2 Bone as a percentage of the total drumstick 21.5 (± .73) 21.3 (± 1.3) 17.5 (± .5) 18.1 21.4 (± .92) 18.2 (±.64) 17.7
1 2 1 2 1 2 1 2 1 2 1 2
(± 20.4)
(± 72.2) (± 92.9) (± .28) (± .24) (± .39) (± .42) (± 5.0) (± 11.9) (± .66) (± 1.0) (± 9.61) (± 8.3) (± .37) (± .66)
'X ± SE. treatment 1 = birds fed diets containing 16,14, and 12% protein, respectively, at 16,20, and 24 wk of age; Treatment 2 = birds kept on a diet of 18% protein from 12 to 28 wk of age.
TABLE 8. Wing yield of Large White, male turkeys finished on diets with two levels of dietary protein Weeks of age Treatment2
16
20
24
28
Wing meat (g), including skin 1 2
629
(± 12.8)
1 2
7.2 (± .07)
1 2
11.8 (± .15)
1 2
39.6 (± 9.9)
1 2
38.6 (± .96) l
803 (± 55.5) 1,123 (± 27.8) 1,103 799 (± 20.6) 1,168 (± 41.6) 1,168 Wing meat as a percentage of the eviscerated carcass 8.1 (± .43) 8.2 (± .18) 6.9 7.9 (± .39) 8.3 (± .37) 7.3 Wing meat as a percentage of the carcass meat 12.6 (± .68) 13.0 (± .21) 10.9 11.9 (± .52) 13.0 (± .59) 11.3 Wing bone (g) 401 (± 11.7) 412 (± 13.8) 478 440 (± 13.8) 460 (± 16.4) 509 Bone as a percentage of total wing 33.5 (± 1.72) 26.8 (± .62) 30.2 35.2 (± 1.02) 28.3 (± .70) 30.5
(± 63.9) (± 47.2) (± .21) (± .22) (± .32) (± .33) (± 20.8) (± 8.31) (± 1.15) (± .72)
X ± SE. treatment 1 = birds fed diets containing 16,14, and 12% protein, respectively, at 16,20, and 24 wk of age; Treatment 2 = birds kept on a diet of 18% protein from 12 until 28 wk of age.
GAIN AND MEAT YIELD OF MALE TURKEYS
589
TABLE 9. Composition of the breast meat, less skin1 Weeks of age Treatment2
16
20
1 2
93.4 (± .37)
92.4 94.2
1 2
6.3 (± .44)
6.0 6.1
1 2
547
1 2
(± 34.9)
37.7 (± 4.7)
24 Protein (percentage of dry weight) (± 2.45) 89.9 (± 1.70) (± .67) 89.5 (± 3.70) • Fat (percentage of dry weight) (± .45) 9.5 (± 1.81) (± .34) 9.2 (± 3.79) • Total protein (g) (± 58.7) 980 (± 25.1) (± 46.6) 1,049 (± 46.3) • Total fat (g) (± 6.3) 97 (± 13.1) (± 7.2) 111 (± 19.9)
688 735 45 49
28 87.3 (± 2.7) 88.1 (± 3.52) 11.1 (± 2.90) 11.1 (± 3.3) 1,199 1,221
(± 37.2) (± 53.6)
131 141
(± 15.1) (± 20.9)
l
X ± SE. ^Treatment 1 = birds fed diets containing 16,14, and 12% protein, respectively, at 16,20, and 24 wk of age; Treatment 2 = birds kept on a diet of 18% from 12 until 28 weeks of age.
dietary treatments was noted (Table 5). Skin as a percentage of breast weight increased with age, while the percentage of bone decreased, The dietary treatment had little effect on the yield of thigh, drumstick, or wing meat or on the bone yields (Tables 6, 7, and 8). However, small differences were noted between the various age groups. The composition of the breast, thigh, and drumstick meat was influenced very little by
the dietary treatments (Tables 9, 10, and 11). However, composition differences were noted among the various age groups. An increase in fat deposition was particularly noticeable for breast and thigh meat at 24 and 28 wk of age. The efficiency of converting dietary protein into edible carcass protein was estimated (Table 12). Although the values shown were calculated from limited and variable data, they demonstrate that with the low-protein diets, the
TABLE 10. Composition of the thigh meat, less skin Weeks of age Treatment
2
16
20
1 2
76.7 (± 2.01)
79.9 76.2
1 2
20.4 (± 1.74)
18.3 22.0
1 2
205
(± 8.06)
264 253
1 2
56
(± 3.26)
60 74
:
28
24 Protein (percentage of dry weight) (± 1.95) 69.2 (± 3.07) (± 3.10) 70.4 (± 5.5) • Fat (percentage of dry weight) (± 2.79) 30.0 (± 3.99) (± 2.98) 27.8 (± 4.82) • Total protein (g) (± 21.0) 324 (± 14.07) (± 17.6) 316 (± 12.25) (± 9.22) (± 12.2)
Total fat (g) 142 (± 20.2) 132 (± 29.4)
67.8 (± 3.54) 67.8 (± 4.2) 33.1 (± 2.8) 30.9 (± 4.8) 345 364
(± 11.8) (± 20.2)
172 170
(± 20.7) (± 31.3)
X ± SE. treatment 1 = birds fed diets containing 16,14, and 12% protein, respectively, at 16,20, and 24 wk of age; Treatment 2 = birds kept on a diet of 18% protein from 12 until 28 wk of age.
590
SUMMERS AND SPRATT TABLE 11. Composition of the drumstick meat, less skin Weeks of age
Treatment2
20
16
24
28
1 2
77.7 (± 1.24)
74.8 (± 2.79) 74.8 (± 4.0)
71.9 (± 3.5) 75.2 (± 2.6)
74.1 (± 1.70) 72.7 (± 2.43)
1 2
19.7 (± 0.85)
24.4 (± 2.98) 24.0 (± 4.10)
24.7 (± 2.04) 23.4 (± 3.3)
25.1 (± 1.68) 26.3 (± 2.75)
1 2
149
(± 3.54)
184 169
(± 16.7) (± 19.2)
216 232
(± 4.66) (± 9.2)
249 246
(± 13.1) (± 17.0)
1 2
38
(± 2.12)
53 52
(± 7.3) (± 9.2)
75 72
(± 8.44) (± 10.8)
86 89
(± 9.51) (± 11.4)
*X ± SE. treatment 1 = birds fed diets containing 16,14, and 12% protein, respectively, at 16,20, and 24 wk of age; Treatment 2 = birds kept on a diet of 18% protein from 12 until 28 wk of age.
TABLE 12.. Edible carcass protein as a percentage of dietary protein intake Weeks of age 1 2
2 to 16
16 to 20
20 to 24
24 to 28
15.3
12.3 12.3 12.1
19.4 19.4 17.7
17.9
2 to 20
2 to 24
2 to 28
14.6 UA
15.6 15£
15.9 13_8
Weeks of age 1 2
Includes only the protein from the breast, thigh, and drumstick meat (which from previous tables makes up over 80% of the total carcass meat). treatment 1 = birds fed diets containing 16,14, and 12% protein, respectively, at 16,20, and 24 wk of age; Treatment 2 = birds kept on a diet of 18% protein from 12 until 28 wk of age.
turkey maintains a fairly efficient utilization of protein even up to 28 wk of age. However, for the higher-protein diets, the efficiency of protein utilization declined after 20 wk of age
and was markedly reduced from 24 to 28 wk of age. The absolute intake of protein for the 24- to 28-wk period was almost twice as high (2,719 versus 1,532 g) for the high-protein diet
TABLE 13. Yield of the breast, thigh, and drumstick meat (less skin) at 20 and 28 weeks of age, average of the two dietary treatments Weeks of age
Carcass weight
Carcass meat
Breast meat
Thigh meat
28
15,959
10,198
(g) — — — — — — — — — 5,274 1,829 1,285
63.9
20
10,100
6,606
2,981
65.4
1,308
Drumstick meat
905
Carcass
Percentage of meat yield Breast Thigh Drumstick (Percentage of carcass weight) • 51.8 18.0 12.6
44.9
19.9
13.8
GAIN AND MEAT YIELD OF MALE TURKEYS
versus the low-protein diet. As is obvious from the performance and carcass data, the increased protein intake did very little to enhance the value of the carcass produced. Since further processing is of increasing importance, especially with heavy-weight toms, the meat yield from 20- and 28-wk-old birds was compared. Table 13 shows the difference in absolute carcass meat yield for the two age groups, when averaged across dietary treatments. The meat yield for breast, thigh, and drumstick meat made up approximately 78% of the total carcass meat at 20 wk of age, increasing to around 82% at 28 wk of age. Also shown is the percentage yield of the various carcass portions. The total meat yield from the carcasses decreased slightly from 20 to 28 wk of age (63.9% versus 65.4%). The percentage of breast meat showed a marked increase (7%) from 20 to 28 wk of age, while yield of thigh and drumstick meat decreased as a percentage of the total meat yield for the same period. Looking at the various portions for the increased yield of meat between 20 and 28 wk of age, 63.8% of this increased yield was breast meat; the yield of thigh meat was 14.5% and that of drumstick meat was 10.6%. Although the increased yield of breast meat between 20 and 28 wk may substantially increase the value of the carcass, that has to be weighed against the extra feed consumed during the period as well as the increased overhead costs and higher mortality. Approximately 70% more feed was consumed between 20 and 28 wk, producing only 46% more BW (Table 3). However, this 46% increase in BW resulted in a meat yield that was 65% higher
591
and obviously was greater than 65% in terms of the edible protein yield. The present study yielded data showing increased yields for various carcass parts as the age of turkeys increased. However, these data must be evaluated in a particular situation in order to judge the economics of keeping male turkeys to heavier processing weights. Blair et al. (1989 a,b) studied similar parameters with three strains of turkeys. Many of their findings were similar to those reported from the present experiment. ACKNOWLEDGMENTS
The authors wish to acknowledge the financial support of the Ministry of Agriculture and Food and the Natural Sciences and Engineering Research Council of Canada. REFERENCES Blair, M. E., L. M. Potter, and R. M. Hulet, 1989a. Effects of dietary protein and added fat on turkey varying in strain, sex and age. 1. Live characteristics. Poultry Sci. 68:278-286. Blair, M. E., L. M. Potter, and R. M. Hulet, 1989b. Effects of dietary protein and added fat on turkeys varying in strain, sex and age. 2. Carcass characteristics. Poultry Sci. 68:287-296. Leeson, S., and J. D. Summers, 1980. Production and carcass characteristics of the large white turkey. Poultry Sci. 59:1237-1245. Moran, E. T., Jr., L. M. Poste, P. R. Ferket, and V. Agar, 1984. Response of large torn turkeys differing in growth characteristics to divergent feeding systems: Performance, carcass quality and sensory evaluation. Poultry Sci. 63:1778-1792. SAS Institute, 1982. SAS User's Guide Statistics, SAS Inst. Inc., Cary, NC. Snedecor, G. W., and W. G. Cochran, 1980. Statistical Methods. 7th Ed. The Iowa State University Press, Ames, IA.