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Age and Dietary Energy Effect on Broiler Abdominal Fat Deposition
Age and Dietary Energy Effect on Broiler Abdominal Fat Deposition J. W. DEATON and B. D. LOTT Agricultural Research Service, US Department of Agriculture, South Central Poultry Research Laboratory, Mississippi State, Mississippi 39762 (Received for publication December 7, 1984)
1985 Poultry Science 64:2161-2164 INTRODUCTION
Mabray and Waldroup (1981) reviewed the literature and noted four general nutritional factors that influence the degree of fatness in broilers: 1) narrowing the calorie-to-protein ratio has generally prevented excessive deposition of body fat; 2) an imbalance of amino acids may cause an increase in body fat; 3) the specific effect of dietary fat on carcass composition; and 4) the effects of dietary energy levels on the degree of fatness of broilers. Deaton et al. (1983) noted that when broilers were fed a 3325 metabolizable energy (ME) kcal/kg diet, male broilers had as much abdominal fat when expressed as a percentage of body weight at 40 days of age as they did at 53 days of age. The objective of this study was to determine when abdominal fat is deposited in relation to age and dietary energy level for male and female broilers. MATERIALS AND METHODS Three trials were conducted. Broiler chicks obtained from a commercial hatchery were placed on pine shavings in pens measuring 1.5 x 3.0 m. Two 38.2-cm diameter tube feeders and a 244-cm linear water space were in each pen. Temperature was not controlled and did fluctuate; however, it was not allowed to decline below 29 C for the 1st week, 27 C for the 2nd week, 24 C for the 3rd week, and 21 C from 4 weeks to the end of the experiment. For the first 3 weeks, all chicks were fed a basal starter diet calculated to contain 22% protein and ME of 3200 kcal/kg. All broilers
were provided with feed and water ad libitum. Feed and body weight data were recorded at 3 weeks of age. Three trials were conducted during the periods of April to June 1983, January to March 1984, and June to August 1984, using commercial broiler chicks. There were four pens of 55 males and 55 females each per dietary treatment for each trial. The diets fed after 3 weeks of age to the end of the experiment consisted of four different dietary energy regimens (Table 1). At 36, 42, 48, and 54 days of age, one pen of males and one pen of females for each trial and for each dietary treatment were sacrificed and the amount of abdominal fat was recorded. The abdominal fat was removed and weighed according to the procedure of Kubena et al. (1974) and reported as a percentage of body weight. All broilers in a pen were sacrificed rather than a sample from each pen. Analyses of variance were conducted for body weight, grams of feed per gram of live weight, and abdominal fat expressed as a percentage of body weight. Abdominal fat data were transformed for analysis using arcsin percentage transformation as described by Steel and Torrie (1960). Significantly different treatment means were separated by the multiple range test of Duncan (1955). RESULTS AND DISCUSSION The mean treatment weight of the male broilers at 21 days of age was 557 g while the mean treatment weight for the female broilers at 21 days of age was 506 g. By 36 days of age,
2161
Downloaded from http://ps.oxfordjournals.org/ at Library, University of Guelph on November 9, 2014
ABSTRACT Three trials were conducted to determine when abdominal fat is deposited in relation to age and dietary energy level for broilers. Results show that the amount of abdominal fat as a percentage of body weight increased as age (36 to 54 days) and dietary energy level (3100 to 3325 metabolizable energy kcal/kg) increased. During the 36 to 54-day period, the weight of the broilers increased 75% for males and 72% for females. During the 36 to 54-day period, abdominal fat expressed as a percentage of body weight increased 23% for males and 38% for females. (Key words: fat, abdominal, broiler, age, weight, dietary energy)
2162
DEATON AND LOTT TABLE 1. Composition of diets Diet number
Ingredient
Calculated analysis Protein, % Metabolizable energy, kcal/kg Lysine, %/Mcal Methionine + cysteine-cystine, %/Mcal Lysine, % Methionine + cysteine-cystine, % Calcium, % Available phosphorus, % Sodium, % Calorie: protein
72.711 18.027 .372 1.079 .808 .408 .250 .155 .100 5.000 1.090
2 70.009 19.209 2.439 1.085 .792 .408 .250 .187 .100 5.000 .521
3 67.336 20.328 4.490 1.091 .775 .409 .250 .219 .100 5.000
4 65.009 20.741 6.363 1.098 .763 .409 .250 .245 .100 5.000
.002 100 18.70 3100 .308 .256 .96 .80 .90 .45 .20 165.8
100 18.70 3175 .308 .256 .98 .81 .90 .45 .20 169.8
100 18.70 3250 .308 .256 1.00 .83 .90 .45 .20 173.8
.022 100 18.70 3325 .308 .256 1.02 .85 .90 .45 .20 177.8
1 The broiler premix furnished the following amounts of other ingredients per kilogram of feed: vitamin A, retinyl acetate form, gelatin coated, 6614 IU; vitamin D 3 , 2205 ICU; vitamin E, DL-alpha tocopherol acetate, 3.31 IU; riboflavin, 4.96 mg; niacin, 27.6 mg; d-pantothenic acid, 8.82 mg; folic acid, 276 Mg; vitamin B 1 2 , 11 Mg; choline chloride, 496 mg; ethoxyquin, 55 mg; menadione dimethylpyrimidinol bisulfite, 1.65 mg; pyridoxine, 1.10 mg; selenium, 10 mg; manganese (oxide form), 55 mg; zinc (oxide form), 50 mg; iodine, 1.25 mg; iron (sulfate form), 40 mg; copper (sulfate form), 4.0 mg. 2
Methionine hydroxy analogue.
3
Coccidiostat containing monensin.
4
Mention of a trade name, proprietary product, or specific equipment does not constitute a guarantee or warranty by the US Department of Agriculture and does not imply its approval t o the exclusion of other products that may be suitable. 5
Blended animal protein supplement.
both male and female broilers fed the 3325 ME kcal/kg diet weighed significantly more and contained significantly more abdominal fat than the group fed the 3100 ME kcal/kg diet (Table 2). This dietary energy difference (3100 vs 3325 ME kcal/kg) required only 15 days (21 to 36 days of age) to show a measured difference in abdominal fat deposition. By 42 days of age, the females fed the 3175 ME kcal/kg diet contained significantly less abdominal fat than females fed the 3325 ME kcal/kg diet even though the body weight did not differ significantly (Table 2). At 48 days of age, which is a normal marketing age, males and females fed the 3325 ME
kcal/kg diet weighed significantly more and contained significantly more abdominal fat than broilers receiving the 3175 and 3100 ME kcal/kg diets (Table 2). At 54 days of age, males fed the 3250 and 3325 ME kcal/kg diets weighed significantly more than males fed the 3175 and 3100 ME kcal/kg diets. At 54 days of age, females fed the 3325 ME kcal/kg diet weighed significantly more than females fed the 3175 and 3100 ME kcal/kg diets. At 54 days of age, males fed the 3325 ME kcal/kg diet contained significantly more abdominal fat than males fed the 3175 and 3100 ME kcal/kg diets while females fed the 3325 and 3250 ME kcal/kg diets contained significantly more
Downloaded from http://ps.oxfordjournals.org/ at Library, University of Guelph on November 9, 2014
Yellow corn Soybean meal, 48.5% protein Animal fat, 7716 kcal/kg Dicalcium phosphate, 22% Ca, 18.5% P Limestone Salt Broiler trace element premix' MHA - Ca, 93%2 Coban (45 g/ton) 3 4 Pro-pak, 62% protein 5 Corn gluten meal, 61% protein L-Lysine-HCl Total
1
ABDOMINAL FAT DEPOSITION
2163
TABLE 2. The effect of dietary energy level and broiler age on abdominal fat deposition (three trials) Female
Male Abdominal fat
Feed/live weight
Body weight
Abdominal fat
Feed/live weight
(g) 1285 a 1667 c 1978 e 2231h
(%) 2.04bcde 2.15def
(g/g) 1.76d 1.83ff 1.97'J 2.10k
1093 a 1416 c 1676 e 19228
(%)
36 42 48 54
1.87 a 2.10 b c 2.30 c d 2.56 ef 8
(g/g) 1.78 cd 1.87 e 2.038 h 2.18J
3175
36 42 48 54
1282 a 1674 c 2029 f 2240 h
1.84 ab 2.01bcde 2.22 e f 8 2.23 ef g
1.72 bc 1.80e 1.91 h 2.07 k
1157 b 1452C d 1666 e 19348
2.13bc 2.25bcd 2.58 e f 8 2.73% h
1.76 b c 1.85 e 2.008 2.12'
3250
36 42 48 54
1294 a 1696 c d 2026 f 2355'
1 97bcd 2.15def 2.37%h 2.438 h
1.69 ab 1.76d 1.878 2.00J
1124 a b 1465cd 1756 f 19588"
2.07 a b 2.38 d e 277ghi 2.98'J
1.7 3 a b 1.80 d 1.96 f 2.10'
2.26bcd 2.54<* 2.85 b ' 3.20J
1.70 a 1.79 c d 1.93 f 2.05 h
(kcal/kg) 3100
3325
Age (days)
36 42 48 54
1371° 1731 d 2096& 2347'
1.73 a ! ggabc
cde
2.07 2.23 ef g 2.53 h 2.58 h
b
a
1172 1478 d 1768 f 1996 h
1.66 1.74 cd 1.86fS 1.95'
a For each category within each sex differing letters denote significant difference at the P<.05 level of probability. Body weight was equated at 21 days of age for each sex and each dietary treatment.
abdominal fat than females fed the 3175 and 3100 ME kcal/kg diets (Table 2). In general, for both male and female broilers, as dietary energy increased, percent abdominal fat increased (Fig. 1). These data are in agreement with those published by Kubena et al. (1974) and Deaton et al. (1983). Feed conversion ratio (feed/live weight) increased with age and weight but decreased as dietary energy level increased (Table 2). As age increased, the amount of abdominal fat increased when expressed as a percentage of body weight (Fig. 2). Within each diet and for both sexes, the amount of abdominal fat expressed as a percentage of body weight was significantly less at 36 days of age than at 48 and 54 days of age (Table 2). The male broilers from 36 to 54 days of age had a 75% weight increase. The abdominal fat expressed as a percentage of body weight increase was 23% for all male broilers from 36 to 54 days of age. For all female broilers the weight increase from 36 to 54 days of age was 72% with an abdominal fat expressed as a percentage of body weight increase of 38%. Deaton et al. (1983) noted
that growth rate and abdominal fat deposition ratio did not change for males fed a 3325 ME kcal/kg diet from 40 to 53 days of age. These data (Deaton et al., 1983), which were collected in a controlled constant temperature environment, showed that on a percentage of body weight basis, there was as much abdominal fat
u.
3100
3175
3250
3325
ME/KG
FIG. 1. Effect of dietary energy level on percent abdominal fat for each sex.
Downloaded from http://ps.oxfordjournals.org/ at Library, University of Guelph on November 9, 2014
Body weight
Dietary energy
2164 2.9
DEATON AND LOTT .
2.7 _
i-
"
-
2.3
.
S.I
.
< u. iS
I
I
l_
36
42
48
54
AGE, DAYS
FIG. 2. Effect of age on percent abdominal fat for each sex.
for a 1580-g broiler as there was for a 2300-g broiler. The data in Table 2 that were collected under a fluctuating temperature regimen do not show a constant ratio for body weight gain and fat deposition. Rather, for both males and females, within each dietary regimen, the broilers at 36 days of age had significantly less abdominal fat than broilers at age 48 and 54 days of age. For male broilers from 48 to 54 days of age, abdominal fat deposition percent did not change significantly (Table 2). However, the female broilers fed diets 1 and 4 (Table 1) deposited significantly more abdominal fat during the six day period from 48 to 54
REFERENCES Deaton, J. W., J. L. McNaughton, and B. D. Lott, 1983. The effect of dietary energy level and broiler body weight on abdominal fat. Poultry Sci. 62:2394-2397. Duncan, D. B., 1955. Multiple range and multiple F tests. Biometrics 11:1—42. Kubena, L. F., T. C. Chen, J. W. Deaton, and F. N. Reece, 1974. Factors influencing the quantity of abdominal fat in broilers. 3. Dietary energy levels. Poultry Sci. 53:974-978. Mabray, C. J., and P. W. Waldroup, 1981. The influence of dietary energy and amino levels on abdominal fat pad development of the broiler chicken. Poultry Sci. 60:151-159. Steel, R.G.D., and J. H. Torrie, 1960. Principles and Procedures of Statistics. McGraw-Hill Book Company, New York, NY. Summers, J. D., and S. Leeson, 1979. Composition of poultry meat as affected by nutritional factors. Poultry Sci. 58:536-542.
Downloaded from http://ps.oxfordjournals.org/ at Library, University of Guelph on November 9, 2014
1.9 L-"'^
days of age (Table 2). Summers and Leeson (1979) noted that fat deposition results when birds are fed energy in excess of normal metabolic needs. The equations for the best fit functional relationships for the data depicted in Figures 1 and 2 are as follows: Figure 1 female, Y = - 4 . 6 4 + .00221X; Figure 1 male, Y = - 3 . 6 3 + .0018X; Figure 2 female, Y = .465 + .0447X; and Figure 2 male, Y = 13.69 - .8775X + .02111IX 2 - .000162X 3 . The results from this study indicate that age and dietary energy level affect deposition of abdominal fat for broilers.
1985 Poultry Science 64:2161-2164 INTRODUCTION
Mabray and Waldroup (1981) reviewed the literature and noted four general nutritional factors that influence the degree of fatness in broilers: 1) narrowing the calorie-to-protein ratio has generally prevented excessive deposition of body fat; 2) an imbalance of amino acids may cause an increase in body fat; 3) the specific effect of dietary fat on carcass composition; and 4) the effects of dietary energy levels on the degree of fatness of broilers. Deaton et al. (1983) noted that when broilers were fed a 3325 metabolizable energy (ME) kcal/kg diet, male broilers had as much abdominal fat when expressed as a percentage of body weight at 40 days of age as they did at 53 days of age. The objective of this study was to determine when abdominal fat is deposited in relation to age and dietary energy level for male and female broilers. MATERIALS AND METHODS Three trials were conducted. Broiler chicks obtained from a commercial hatchery were placed on pine shavings in pens measuring 1.5 x 3.0 m. Two 38.2-cm diameter tube feeders and a 244-cm linear water space were in each pen. Temperature was not controlled and did fluctuate; however, it was not allowed to decline below 29 C for the 1st week, 27 C for the 2nd week, 24 C for the 3rd week, and 21 C from 4 weeks to the end of the experiment. For the first 3 weeks, all chicks were fed a basal starter diet calculated to contain 22% protein and ME of 3200 kcal/kg. All broilers
were provided with feed and water ad libitum. Feed and body weight data were recorded at 3 weeks of age. Three trials were conducted during the periods of April to June 1983, January to March 1984, and June to August 1984, using commercial broiler chicks. There were four pens of 55 males and 55 females each per dietary treatment for each trial. The diets fed after 3 weeks of age to the end of the experiment consisted of four different dietary energy regimens (Table 1). At 36, 42, 48, and 54 days of age, one pen of males and one pen of females for each trial and for each dietary treatment were sacrificed and the amount of abdominal fat was recorded. The abdominal fat was removed and weighed according to the procedure of Kubena et al. (1974) and reported as a percentage of body weight. All broilers in a pen were sacrificed rather than a sample from each pen. Analyses of variance were conducted for body weight, grams of feed per gram of live weight, and abdominal fat expressed as a percentage of body weight. Abdominal fat data were transformed for analysis using arcsin percentage transformation as described by Steel and Torrie (1960). Significantly different treatment means were separated by the multiple range test of Duncan (1955). RESULTS AND DISCUSSION The mean treatment weight of the male broilers at 21 days of age was 557 g while the mean treatment weight for the female broilers at 21 days of age was 506 g. By 36 days of age,
2161
Downloaded from http://ps.oxfordjournals.org/ at Library, University of Guelph on November 9, 2014
ABSTRACT Three trials were conducted to determine when abdominal fat is deposited in relation to age and dietary energy level for broilers. Results show that the amount of abdominal fat as a percentage of body weight increased as age (36 to 54 days) and dietary energy level (3100 to 3325 metabolizable energy kcal/kg) increased. During the 36 to 54-day period, the weight of the broilers increased 75% for males and 72% for females. During the 36 to 54-day period, abdominal fat expressed as a percentage of body weight increased 23% for males and 38% for females. (Key words: fat, abdominal, broiler, age, weight, dietary energy)
2162
DEATON AND LOTT TABLE 1. Composition of diets Diet number
Ingredient
Calculated analysis Protein, % Metabolizable energy, kcal/kg Lysine, %/Mcal Methionine + cysteine-cystine, %/Mcal Lysine, % Methionine + cysteine-cystine, % Calcium, % Available phosphorus, % Sodium, % Calorie: protein
72.711 18.027 .372 1.079 .808 .408 .250 .155 .100 5.000 1.090
2 70.009 19.209 2.439 1.085 .792 .408 .250 .187 .100 5.000 .521
3 67.336 20.328 4.490 1.091 .775 .409 .250 .219 .100 5.000
4 65.009 20.741 6.363 1.098 .763 .409 .250 .245 .100 5.000
.002 100 18.70 3100 .308 .256 .96 .80 .90 .45 .20 165.8
100 18.70 3175 .308 .256 .98 .81 .90 .45 .20 169.8
100 18.70 3250 .308 .256 1.00 .83 .90 .45 .20 173.8
.022 100 18.70 3325 .308 .256 1.02 .85 .90 .45 .20 177.8
1 The broiler premix furnished the following amounts of other ingredients per kilogram of feed: vitamin A, retinyl acetate form, gelatin coated, 6614 IU; vitamin D 3 , 2205 ICU; vitamin E, DL-alpha tocopherol acetate, 3.31 IU; riboflavin, 4.96 mg; niacin, 27.6 mg; d-pantothenic acid, 8.82 mg; folic acid, 276 Mg; vitamin B 1 2 , 11 Mg; choline chloride, 496 mg; ethoxyquin, 55 mg; menadione dimethylpyrimidinol bisulfite, 1.65 mg; pyridoxine, 1.10 mg; selenium, 10 mg; manganese (oxide form), 55 mg; zinc (oxide form), 50 mg; iodine, 1.25 mg; iron (sulfate form), 40 mg; copper (sulfate form), 4.0 mg. 2
Methionine hydroxy analogue.
3
Coccidiostat containing monensin.
4
Mention of a trade name, proprietary product, or specific equipment does not constitute a guarantee or warranty by the US Department of Agriculture and does not imply its approval t o the exclusion of other products that may be suitable. 5
Blended animal protein supplement.
both male and female broilers fed the 3325 ME kcal/kg diet weighed significantly more and contained significantly more abdominal fat than the group fed the 3100 ME kcal/kg diet (Table 2). This dietary energy difference (3100 vs 3325 ME kcal/kg) required only 15 days (21 to 36 days of age) to show a measured difference in abdominal fat deposition. By 42 days of age, the females fed the 3175 ME kcal/kg diet contained significantly less abdominal fat than females fed the 3325 ME kcal/kg diet even though the body weight did not differ significantly (Table 2). At 48 days of age, which is a normal marketing age, males and females fed the 3325 ME
kcal/kg diet weighed significantly more and contained significantly more abdominal fat than broilers receiving the 3175 and 3100 ME kcal/kg diets (Table 2). At 54 days of age, males fed the 3250 and 3325 ME kcal/kg diets weighed significantly more than males fed the 3175 and 3100 ME kcal/kg diets. At 54 days of age, females fed the 3325 ME kcal/kg diet weighed significantly more than females fed the 3175 and 3100 ME kcal/kg diets. At 54 days of age, males fed the 3325 ME kcal/kg diet contained significantly more abdominal fat than males fed the 3175 and 3100 ME kcal/kg diets while females fed the 3325 and 3250 ME kcal/kg diets contained significantly more
Downloaded from http://ps.oxfordjournals.org/ at Library, University of Guelph on November 9, 2014
Yellow corn Soybean meal, 48.5% protein Animal fat, 7716 kcal/kg Dicalcium phosphate, 22% Ca, 18.5% P Limestone Salt Broiler trace element premix' MHA - Ca, 93%2 Coban (45 g/ton) 3 4 Pro-pak, 62% protein 5 Corn gluten meal, 61% protein L-Lysine-HCl Total
1
ABDOMINAL FAT DEPOSITION
2163
TABLE 2. The effect of dietary energy level and broiler age on abdominal fat deposition (three trials) Female
Male Abdominal fat
Feed/live weight
Body weight
Abdominal fat
Feed/live weight
(g) 1285 a 1667 c 1978 e 2231h
(%) 2.04bcde 2.15def
(g/g) 1.76d 1.83ff 1.97'J 2.10k
(%)
36 42 48 54
1.87 a 2.10 b c 2.30 c d 2.56 ef 8
(g/g) 1.78 cd 1.87 e 2.038 h 2.18J
3175
36 42 48 54
1282 a 1674 c 2029 f 2240 h
1.84 ab 2.01bcde 2.22 e f 8 2.23 ef g
1.72 bc 1.80e 1.91 h 2.07 k
1157 b 1452C d 1666 e 19348
2.13bc 2.25bcd 2.58 e f 8 2.73% h
1.76 b c 1.85 e 2.008 2.12'
3250
36 42 48 54
1294 a 1696 c d 2026 f 2355'
1 97bcd 2.15def 2.37%h 2.438 h
1.69 ab 1.76d 1.878 2.00J
1124 a b 1465cd 1756 f 19588"
2.07 a b 2.38 d e 277ghi 2.98'J
1.7 3 a b 1.80 d 1.96 f 2.10'
2.26bcd 2.54<* 2.85 b ' 3.20J
1.70 a 1.79 c d 1.93 f 2.05 h
(kcal/kg) 3100
3325
Age (days)
36 42 48 54
1371° 1731 d 2096& 2347'
1.73 a ! ggabc
cde
2.07 2.23 ef g 2.53 h 2.58 h
b
a
1172 1478 d 1768 f 1996 h
1.66 1.74 cd 1.86fS 1.95'
a For each category within each sex differing letters denote significant difference at the P<.05 level of probability. Body weight was equated at 21 days of age for each sex and each dietary treatment.
abdominal fat than females fed the 3175 and 3100 ME kcal/kg diets (Table 2). In general, for both male and female broilers, as dietary energy increased, percent abdominal fat increased (Fig. 1). These data are in agreement with those published by Kubena et al. (1974) and Deaton et al. (1983). Feed conversion ratio (feed/live weight) increased with age and weight but decreased as dietary energy level increased (Table 2). As age increased, the amount of abdominal fat increased when expressed as a percentage of body weight (Fig. 2). Within each diet and for both sexes, the amount of abdominal fat expressed as a percentage of body weight was significantly less at 36 days of age than at 48 and 54 days of age (Table 2). The male broilers from 36 to 54 days of age had a 75% weight increase. The abdominal fat expressed as a percentage of body weight increase was 23% for all male broilers from 36 to 54 days of age. For all female broilers the weight increase from 36 to 54 days of age was 72% with an abdominal fat expressed as a percentage of body weight increase of 38%. Deaton et al. (1983) noted
that growth rate and abdominal fat deposition ratio did not change for males fed a 3325 ME kcal/kg diet from 40 to 53 days of age. These data (Deaton et al., 1983), which were collected in a controlled constant temperature environment, showed that on a percentage of body weight basis, there was as much abdominal fat
u.
3100
3175
3250
3325
ME/KG
FIG. 1. Effect of dietary energy level on percent abdominal fat for each sex.
Downloaded from http://ps.oxfordjournals.org/ at Library, University of Guelph on November 9, 2014
Body weight
Dietary energy
2164 2.9
DEATON AND LOTT .
2.7 _
i-
"
-
2.3
.
S.I
.
< u. iS
I
I
l_
36
42
48
54
AGE, DAYS
FIG. 2. Effect of age on percent abdominal fat for each sex.
for a 1580-g broiler as there was for a 2300-g broiler. The data in Table 2 that were collected under a fluctuating temperature regimen do not show a constant ratio for body weight gain and fat deposition. Rather, for both males and females, within each dietary regimen, the broilers at 36 days of age had significantly less abdominal fat than broilers at age 48 and 54 days of age. For male broilers from 48 to 54 days of age, abdominal fat deposition percent did not change significantly (Table 2). However, the female broilers fed diets 1 and 4 (Table 1) deposited significantly more abdominal fat during the six day period from 48 to 54
REFERENCES Deaton, J. W., J. L. McNaughton, and B. D. Lott, 1983. The effect of dietary energy level and broiler body weight on abdominal fat. Poultry Sci. 62:2394-2397. Duncan, D. B., 1955. Multiple range and multiple F tests. Biometrics 11:1—42. Kubena, L. F., T. C. Chen, J. W. Deaton, and F. N. Reece, 1974. Factors influencing the quantity of abdominal fat in broilers. 3. Dietary energy levels. Poultry Sci. 53:974-978. Mabray, C. J., and P. W. Waldroup, 1981. The influence of dietary energy and amino levels on abdominal fat pad development of the broiler chicken. Poultry Sci. 60:151-159. Steel, R.G.D., and J. H. Torrie, 1960. Principles and Procedures of Statistics. McGraw-Hill Book Company, New York, NY. Summers, J. D., and S. Leeson, 1979. Composition of poultry meat as affected by nutritional factors. Poultry Sci. 58:536-542.
Downloaded from http://ps.oxfordjournals.org/ at Library, University of Guelph on November 9, 2014
1.9 L-"'^
days of age (Table 2). Summers and Leeson (1979) noted that fat deposition results when birds are fed energy in excess of normal metabolic needs. The equations for the best fit functional relationships for the data depicted in Figures 1 and 2 are as follows: Figure 1 female, Y = - 4 . 6 4 + .00221X; Figure 1 male, Y = - 3 . 6 3 + .0018X; Figure 2 female, Y = .465 + .0447X; and Figure 2 male, Y = 13.69 - .8775X + .02111IX 2 - .000162X 3 . The results from this study indicate that age and dietary energy level affect deposition of abdominal fat for broilers.