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Influence of Nutritional Modification on Skeletal Size of Leghorn and Broiler Breeder Pullets
Influence of Nutritional Modification on Skeletal Size of Leghorn and Broiler Breeder Pullets S. LEESON and J. D. SUMMERS Department of Animal and Poultry Science, University of Guelph, Guelph Ontario, Canada NIG 2W1 (Received for publication August 10, 1983) ABSTRACT Two trials were undertaken to study the effect of nutrient intake on skeletal size in growing pullets. Leghorn chicks at 28 days were smaller in weight and shank and keel length when fed 16% as compared to 22% crude protein. Increasing the energy or mineral-vitamin concentration of the diet had no effect on skeletal parameters. Increased skeletal size of pullets in response to increased diet protein was associated with reduced (P<.01) tibial ash content. In a subsequent trial, broiler breeder pullets were fed, ad libitum, starter diets (0 to 21 days) containing graded levels of protein from 20 to 13%. Reducing protein level had a consistent negative effect on body weight, shank length, and keel length at 21 days. When birds were subsequently fed restricted quantities of a common grower diet, no differences in body weight and skeletal parameters were evident at maturity. It is concluded that although early body weight and skeletal size can be markedly influenced by diet protein level, such effects are subsequently nullified by conventional restricted feeding programs. (Key words: nutrient skeletal size pullets, protein-diet) 1984 Poultry Science 63:1222-1228 INTRODUCTION
Over the last few years the term "frame size" (skeletal dimension) has been used with increasing frequency in describing the physical characteristics of pullets. The two most common measures of frame size are shank length (tarsometatarsus) and keel length. Shank length has been suggested as a criterion for body size (Lemer, 1937) while Jaap (1938) suggests shank length to be a reliable measure of skeletal size. It is realized that although two pullets may be of similar weight, their skeletal dimensions may differ, leading to the suggestion that birds of equal weight may not be similar or uniform. There is little information dealing with skeletal dimension or how it is influenced by nutritional modification. With Leghorn pullets there is interest in early rapid development in order to accommodate early maturity. Lerner (1946) suggests skeletal size to be the limiting factor in increasing body size, hence, the recent interest in trying to increase early skeleton size. The converse may apply with broiler breeder pullets in that adequate mature (20 weeks) weight coupled with small frame size could be advantageous in limiting subsequent growth during the breeding period. Although it is known that a deficiency (Garlich et al., 1982) and an excess (Lee era/., 1980) of certain minerals can influence skeletal
development, such dietary situations invariably lead to abnormal bone growth. Of the major nutrients, protein is most likely to influence frame size, because birds fed diets low in protein or amino acid content will be smaller than contemporaries fed adequate levels of these nutrients (Leeson and Summers, 1979). However, just what changes in bone length, if any, are precipitated by given changes in protein intake are not documented. For this reason trials were undertaken with Leghorn and broiler breeder pullets to observe the effect of major nutrient levels on bone length. MATERIALS AND METHODS
Experiment 1. Day-old male Leghorn chicks were weight-sorted and randomly allocated to cages in a Petersime brooder such that each cage contained 8 chicks of equal mean weight. Corn-soybean meal-fat diets were formulated to provide three nutrient comparisons: 1) 22 vs. 16% crude protein (CP), at 2900 kcal metabolizable energy (ME)/kg; 2) 1 vs. 6% supplemental fat, substituted for alpha floe cellulose, at 15.8% CP; 3) mineral-vitamin premix addition at regular (Summers and Leeson, 1976) vs. double inclusion rate, substituted for alpha floe cellulose, at 15.8% CP and 2900 kcal ME/kg. Each diet was offered to six replicate cage groups for 28 days. At this time birds were weighed and shank and keel length measured
1222
NUTRITION AND PULLET SKELETAL SIZE
with a vernier caliper equipped with dial read-out. The left tibia from two sacrificed chicks per cage were cleaned of adhering tissue, dried at 100 C for 24 hr, defatted by Soxhlet ether extraction, and redried at 70 C for 24 hr prior to ashing at 600 C for 12 hr. Experiment 2. Broiler breeder pullets of a commercial strain were fed starter diets varying in protein content from 13 to 20% in increments of 1% (Table 1). These diets were offered ad lib to six replicate groups of 10 caged chicks maintained in a Petersime brooder unit. Body weight and feed intake were recorded weekly. Shank (tarsometatarsal) length was measured at day-of-age and at subsequent 7-day intervals using a vernier caliper as described previously. Because the caudal end of the sternum and the carinal apex are not calcified in the very young bird, it is difficult to obtain an accurate and precise measure of keel length. It was found impossible to obtain any degree of precision until birds were 14 days of age and then only when measurements were taken from the hypocleidum-clavical joint. Thus keel measurements relate to the distance between this hypocleidum-clavical joint and the caudal end of the sternum. This measure was found more repeatable than true keel length due to the keel's indistinct cartilagenous ends. From subsequent dissection studies on 23-week-old birds this measure is found to be about 120% of the true keel length. At 21 days, three replicate groups of 15 birds each were selected at random from across all replicates within the treatment groups previously fed 20, 18, 15, and 13 CP diets and transferred to litter floor pens in a room with controlled ventilation and 8 hr light per day. Of the remaining caged birds, 2 per replicate were starved for 5 hr, sacrificed by cervical dislocation, and their entire feathered carcasses homogenized prior to determination of dry matter, crude protein and ether extractable fat (Association of Official Analytical Chemists, 1975). All floor reared birds were fed a common grower diet (Table 1) at restricted levels commensurate with the breeder's recommendation. Birds were weighed at 49, 77, 105, 13 3, and 161 days, at which time individual measurements of shank and keel length were undertaken. Statistical Analysis. All data were subject to ANOVA (Steel and Torrie, 1980), and where significance occurred, means were separated by the multiple range test (Duncan, 1955).
1223
RESULTS AND DISCUSSION Increasing diet protein from 16 to 22% caused a significant increase in body weight and shank and keel length of Leghorn chicks (Table 2). However, increased bone length was associated with a small yet statistically significant reduction in tibial ash content, suggesting reduced bone integrity. Increasing the energy content of the diet with 6% supplemental fat also resulted in improved growth, although skeletal measurements were unaffected (Table 2). The level of mineral and vitamin supplementation had no effect on body weight or skeletal measurements. The 20% increase in body weight of chicks in response to increased dietary protein was associated with smaller proportional increases in keel length (6.5%) and shank length (4%). If pullets with larger skeletons are to be achieved with higher protein starter diets, then more work needs to be carried out to investigate the commercial significance of the reduced bone mineralization noted here. Weiss et al. (1981) reported osteoporosis in rats fed high-protein diets. Reducing the protein content of the starter diet of broiler breeder pullets resulted in a significant reduction in body weight to 21 days (Table 3). Assuming 17% CP as a standard, higher protein levels had no consistent effect other than birds fed 20% CP being heavier at 14 and 21 days. With one exception, birds fed less than 17% CP had reduced body weights commensurate with reduced dietary protein level. The pattern of effect of dietary protein level on feed intake was the same as that observed for body weight (Table 4). Carcass composition at 21 days revealed a significant increase in fat content and decrease in protein content in response to reduced diet protein level (Table 5). Starter diets used to 3 weeks influenced body weight only up to 77 days of age (Table 3). Differences in body weight were associated with similar trends in both shank and keel length. Starter diet protein from 20 to 17% had no effect on shank length to 21 days (Table 6). Generally, shank length was decreased at 21 days as protein levels declined from 16 to 13%. Differences in shank length due to starter diet protein level were seen only up to 49 days of age, and in fact, after this time, birds from the lower protein treatments had the longest (P>.05) shanks. A similar pattern emerged for keel length (Table 7), although the carry-over effect of starter diet was evident up to 105 days. At 105 days, the keel length of pullets
1
See Leeson and Summers (1981).
Crude protein, % Metabolizable energy, kcal/kg
Calculated analysis
Total
Ground corn Ground barley Soybean meal (48%) Animal vegetable fat Dicalcium phosphate (20% P) Limestone Iodized salt Mineral vitamin premix i DL-Methionine L-Lysine Alpha floe cellulose
19.0 2898
.95
.94
100.00
.94
100.00
18.0 2904
100.00
.25 .75 .05
.25 .75 .06
50.00 20.00 23.75 1.00 2.00 1.25
.25 .75 .06
3
50.00 17.25 26.50 1.00 2.00 1.25
2
50.00 14.25 29.50 1.00 2.00 1.25
20.0 2892
1
100.00
.95
.25 .75 .05
50.00 22.75 21.00 1.00 2.00 1.25
100.00
.97
.25 .75 .03
47.00 28.65 18.10 1.00 2.00 1.25
16.0 2900
5
Starter diet
17.0 2911
4
TABLE 1. Percentage diet composition
15
100
47 31 13 1 2 1
2907
6
NUTRITION AND PULLET SKELETAL SIZE
1225
TABLE 2. Effect of major nutrient concentration on body weight and frame measurements of 28-day Leghorn chicks Feed intake
Keel length
**
**
**
**
(%) **
297 248
573 537
6.85 6.43
6.12 5.87
51.7 52.8
*
**
NS1
NS
NS
270 275
574 537
6.65 6.64
5.97 6.01
52.2 52.0
NS
NS
NS
NS
NS
272 272
558 552
6.63 6.56
6.02 5.97
52.0 52.3
Treatment
Body weight
Protein 22% 16%
\&i
Fat supplement 1% 6%
Mineral-vitamin premix Regular inclusion Double inclusion
Shank length
Tibia ash
(0111,1
'Significant difference (P<.05). "Significant difference (P<.01). 1
NS, Nonsignificant (P>.05).
previously fed 13% CP was less ( P < . 0 5 ) t h a n t h a t of birds fed 15, 17, or 20% CP. There were no differences in keel length at 161 days (Table 7). Correlation between b o d y weight and parameters of skeletal dimension declined with age (Table 8). Highly significant correlations are seen where b o d y weight differences were imposed through diet t r e a t m e n t . However, w h e n b o d y weights were equalized after 105
days (Table 3), there appeared t o be n o relationship b e t w e e n b o d y weight and shank and keel lengths (Table 8). T h e present results suggest t h a t starter dietary p r o t e i n level, while influencing early skeletal size, has little effect on m a t u r e b o d y weight or skeletal size of broiler b r e e d e r pullets. Early protein intake does initially influence these p a r a m e t e r s ; however, t h e effects are nullified by 105 days with a conventional
TABLE 3. Effect of starter diet protein level on body weight of broiler breeder pullets with common grower diet from 21 days Crude protein 0 to 21 days
Days of age 7
14
21
49
77
105
133
161
no dd
259 e 256 d e 252de 250 d 236 c 196 b 199 b 173 a
477 e 46lde 476 e 455cd 44 2 c 387 b 382b 337 a
881c
1285 b
1714
2095
2688
875 b c
1280b
1703
2070
2648
843ab
1243ab
1692
2084
2657
**
**
*
1661
2073
2643
NS1
NS
NS
(%) 20 19 18 17 16 15 14 13
(g)
110 109 d 108 d 101 c 98b 92b 86a
**
810
a
1216
*
a
a,b,c,d,e;Means within columns followed by different letters are significantly different (**P<.01; *P<.05). 1
NS, Nonsignificant.
LEESON AND SUMMERS
1226
TABLE 4. Effect of starter diet protein level on feed intake of broiler breeder pullets (g) Feed intake
Crude protein in diet
0 to 7 days
7 to 14 days
14 to 21 days
0 to 21 days
96e 95cde 98de 97de 94.bcd 90bc 89b 83a
237 c 237 c 234 c 239 c 231 c 201b 204 b 181 a
389 c d 380bcd 393cd 389cd 397 d 364 b 373bc 337»
725 c 712 c 725 c 724 c 722 c 655b 667b 601a
**
**
**
**
(%) 20 19 18 17 16 15 14 13
a,b,c,d,e Means within columns followed by different letters are significantly different (**P<.01).
TABLE 5. Carcass composition of broiler breeder pullets at 21 days Crude protein in diet
Dry matter
Crude protein
20 19 18 17 16 15 14 13
33.6 a b 33.2a 3 3.9 a b 34.0 b 34.3 b 35.2 C 35.4 C 35.8 C
50.8 d e 52.3 e 49.5cd 50.2 d e 41.7bc 44 9 ab 44.3 a 43.la
38.9 a b 37.7 a 41.6 C 41.3bc 43.2 C 45.8 d 46.8d 47.3 d
**
**
**
Fat
(% I
' ' ' Means within columns followed by different letters are significantly different (**P<.01).
restricted feeding program. Unlike the situation with Leghorn chicks (Table 2), proportional differences seen for the broiler pullets, with extremes of protein intake, are comparable for body weight (17%) shank length (14%) and keel length (21%) at 21 days. The present results confirm that offering breeder pullets very low protein diets will aid in retarding growth. Concern exists that such growth is associated with increased (P<.01) fat deposition (Table 5), although it is expected that the subsequent prolonged period of restricted feeding would nullify this balance. There seems little scope for influencing skeletal dimensions through modification of grower diets, since the normally severe physical feed restriction at this time allows little freedom in
TABLE 6. Shank length of broiler breeder pullets Crude 'protein :er diet, Oto 21. days
1
7
14
21
,
(%) 20 19 18 17 16 15 14 13
Days of age 49
2.89 2.82 2.92 2.92 2.88 2.92 2.92 2.92 NS 1
c
77
105
133
161
s
3.73 3.67 c 3.71 c 3.69 c 3.60 b 3.55 b 3.54 a b 3.48 a
5.31 d 5.26 d 5.26 d 5.23 c d 5.14 c 4.84 b 4.85 b 4.66 a
6.69 d 6.64 d 6.66 d 6.60 c d 6.52 c 6.14 b 6.15 b 5.83 d
8.70 c
10.37
11.21
11.33
11.32
8.80 c
10.58
11.34
11.46
11.46
8.58°
10.40
11.36
11.44
11.41
a
**
**
**
**
10.25 NS
11.22 NS
11.44 NS
11.42 NS
8.45
' ' ' Means within columns followed by different letters are significantly different (**P<.01). 1
NS, Nonsignificant.
NUTRITION AND PULLET SKELETAL SIZE
1227
TABLE 7. Keel length of broiler breeder pullets Crude protein :er diet, Oto 21. days
Days of age 21
14
77
49
105
183
161
,
(%) e
20 19 18 17 16 15 14 13
e
c
(cm) 12.81 c
14.43 b
15.29
15.81
10.43 c
12.77 c
14.49 b
15.42
15.91
b
b
14.39 b
15.28
16.01
6.55 6.50de 6.42 d e 6.34 d 6.15 c 5.62 b 5.59 b 5.25 a
8.12 8.08 d e 7.91 d 8.01de 7.95 d e 7.16 b 7.34 c 6.71 a
10.32
**
**
**
10.05
9.77a
12.52
12.27 a
14.06 a
15.13
15.75
**
*
NS'
NS
a,b,c,d,e Means within columns followed by different letters are significantly different (**P<.01; *P<.05). ' NS, Nonsignificant.
TABLE 8. Correlations between body weight and frame size parameter for different ages of a broiler breeder pullet population fed graded levels of dietary protein from 0 to 21 days Pullet
Body weight: shank length R
Significance
.162 .925 .973 .980 .844 .608 .109 .346 .391
NS
Body weight: keel length
Shank length:keel length
R
Significance
R
Significance
.959 .939 .909 .855 .628 .326 399
** ** ** ** *
,952 .958 .950 .611 .563 .290 .352
** ** ** *
(days) 1 7 14 21 49 77 105 133 161
** ** ** ** * NS NS NS
NS NS
NS NS NS
'NS, Nonsignificant. * Significant:, P-C05. **P<.01.
reducing n u t r i e n t i n t a k e . It seems unlikely t h a t skeletal size can be m a r k e d l y influenced b y n u t r i t i o n w i t h o u t affecting b o d y size due to genetic correlation (Jull and Glazener, 1 9 4 6 ; Nestor, 1 9 7 1 ) ; however, if such action is to be tried, diet modification for greater t h a n 3 weeks seems essential. In this respect, prolonged use of low protein starter diets w i t h o u t recourse t o physical restriction, as proposed by Leeson and S u m m e r s ( 1 9 8 1 ) , m a y be beneficial. ACKNOWLEDGMENTS This work was s u p p o r t e d b y t h e Ontario Ministry of Agriculture and F o o d , Natural
Science and Engineering Research Council of Canada and H u b b a r d F a r m s , Walpole, NH.
REFERENCES Association of Official Analytical Chemists, 1975. Official Methods of Analysis. Assoc. Offic. Anal. Chem., Washington, DC. Duncan, B. B., 1955. Multiple range and multiple F tests. Biometrics 11:1—42. Garlich, J., C. Morris, and J. Brake, 1982. External bone volume, ash and fat-free dry weight of femurs of laying hens fed diets deficient or adequate in phosphorus. Poultry Sci. 61:1003 — 1006. Jaap, R. G., 1938. Breeding for body shape in chick-
1228
LEESON AND SUMMERS
ens. US Egg Poult. Mag. 4 4 : 4 8 8 - 5 0 3 . Jull, M. A., and E. W. Glazener, 1946. Rate of growth in progeny to ten weeks in relation to shank length of parents. Poultry Sci. 2 5 : 2 5 6 - 2 6 1 . Leeson, S., and J. D. Summers, 1979. Step-up protein diets for growing pullets. Poultry Sci. 58:681 — 686. Leeson, S., and J. D. Summers, 1981. Dietary selfselection and use of reverse-protein diets for developing broiler breeder pullets. Poultry Sci. 60:168-171. Lee, S. R., W. M. Britton, and G. N. Rowland, 190. Magnesium toxicity: Bone lesions. Poultry Sci. 59:2403-2411. Lerner, I. M., 1937. Shank length as a criterion of inherent size. Poultry Sci. 16:213—215.
Lerner, I. M., 1946. The effect of selection for shank length on sexual maturity and early egg weight in SCWL pullets. Poultry Sci. 25:204-209. Nestor, K. E., 1971. Genetics of growth and reproduction in the turkey. 4. Strain crossing for improvement of growth and reproduction. Poultry Sci. 50:1683-1689. Steel, R.G.D., and J. H. Torrie, 1980. Principles and Procedures of Statistics. A Biometrical Approach. 2nd ed. McGraw-Hill Book Co., New York, NY. Summers, J. D., and S. Leeson, 1976. Poultry Nutrition Handbook. Ont. Ministry Agric. Food., Toronto. Weiss, R. E., A. Gorn, S. Dux, and M. E. Nimni, 1981. Influence of high protein diets on cartilage and bond formation in rats. J. Nutr. 111:804—816.
Over the last few years the term "frame size" (skeletal dimension) has been used with increasing frequency in describing the physical characteristics of pullets. The two most common measures of frame size are shank length (tarsometatarsus) and keel length. Shank length has been suggested as a criterion for body size (Lemer, 1937) while Jaap (1938) suggests shank length to be a reliable measure of skeletal size. It is realized that although two pullets may be of similar weight, their skeletal dimensions may differ, leading to the suggestion that birds of equal weight may not be similar or uniform. There is little information dealing with skeletal dimension or how it is influenced by nutritional modification. With Leghorn pullets there is interest in early rapid development in order to accommodate early maturity. Lerner (1946) suggests skeletal size to be the limiting factor in increasing body size, hence, the recent interest in trying to increase early skeleton size. The converse may apply with broiler breeder pullets in that adequate mature (20 weeks) weight coupled with small frame size could be advantageous in limiting subsequent growth during the breeding period. Although it is known that a deficiency (Garlich et al., 1982) and an excess (Lee era/., 1980) of certain minerals can influence skeletal
development, such dietary situations invariably lead to abnormal bone growth. Of the major nutrients, protein is most likely to influence frame size, because birds fed diets low in protein or amino acid content will be smaller than contemporaries fed adequate levels of these nutrients (Leeson and Summers, 1979). However, just what changes in bone length, if any, are precipitated by given changes in protein intake are not documented. For this reason trials were undertaken with Leghorn and broiler breeder pullets to observe the effect of major nutrient levels on bone length. MATERIALS AND METHODS
Experiment 1. Day-old male Leghorn chicks were weight-sorted and randomly allocated to cages in a Petersime brooder such that each cage contained 8 chicks of equal mean weight. Corn-soybean meal-fat diets were formulated to provide three nutrient comparisons: 1) 22 vs. 16% crude protein (CP), at 2900 kcal metabolizable energy (ME)/kg; 2) 1 vs. 6% supplemental fat, substituted for alpha floe cellulose, at 15.8% CP; 3) mineral-vitamin premix addition at regular (Summers and Leeson, 1976) vs. double inclusion rate, substituted for alpha floe cellulose, at 15.8% CP and 2900 kcal ME/kg. Each diet was offered to six replicate cage groups for 28 days. At this time birds were weighed and shank and keel length measured
1222
NUTRITION AND PULLET SKELETAL SIZE
with a vernier caliper equipped with dial read-out. The left tibia from two sacrificed chicks per cage were cleaned of adhering tissue, dried at 100 C for 24 hr, defatted by Soxhlet ether extraction, and redried at 70 C for 24 hr prior to ashing at 600 C for 12 hr. Experiment 2. Broiler breeder pullets of a commercial strain were fed starter diets varying in protein content from 13 to 20% in increments of 1% (Table 1). These diets were offered ad lib to six replicate groups of 10 caged chicks maintained in a Petersime brooder unit. Body weight and feed intake were recorded weekly. Shank (tarsometatarsal) length was measured at day-of-age and at subsequent 7-day intervals using a vernier caliper as described previously. Because the caudal end of the sternum and the carinal apex are not calcified in the very young bird, it is difficult to obtain an accurate and precise measure of keel length. It was found impossible to obtain any degree of precision until birds were 14 days of age and then only when measurements were taken from the hypocleidum-clavical joint. Thus keel measurements relate to the distance between this hypocleidum-clavical joint and the caudal end of the sternum. This measure was found more repeatable than true keel length due to the keel's indistinct cartilagenous ends. From subsequent dissection studies on 23-week-old birds this measure is found to be about 120% of the true keel length. At 21 days, three replicate groups of 15 birds each were selected at random from across all replicates within the treatment groups previously fed 20, 18, 15, and 13 CP diets and transferred to litter floor pens in a room with controlled ventilation and 8 hr light per day. Of the remaining caged birds, 2 per replicate were starved for 5 hr, sacrificed by cervical dislocation, and their entire feathered carcasses homogenized prior to determination of dry matter, crude protein and ether extractable fat (Association of Official Analytical Chemists, 1975). All floor reared birds were fed a common grower diet (Table 1) at restricted levels commensurate with the breeder's recommendation. Birds were weighed at 49, 77, 105, 13 3, and 161 days, at which time individual measurements of shank and keel length were undertaken. Statistical Analysis. All data were subject to ANOVA (Steel and Torrie, 1980), and where significance occurred, means were separated by the multiple range test (Duncan, 1955).
1223
RESULTS AND DISCUSSION Increasing diet protein from 16 to 22% caused a significant increase in body weight and shank and keel length of Leghorn chicks (Table 2). However, increased bone length was associated with a small yet statistically significant reduction in tibial ash content, suggesting reduced bone integrity. Increasing the energy content of the diet with 6% supplemental fat also resulted in improved growth, although skeletal measurements were unaffected (Table 2). The level of mineral and vitamin supplementation had no effect on body weight or skeletal measurements. The 20% increase in body weight of chicks in response to increased dietary protein was associated with smaller proportional increases in keel length (6.5%) and shank length (4%). If pullets with larger skeletons are to be achieved with higher protein starter diets, then more work needs to be carried out to investigate the commercial significance of the reduced bone mineralization noted here. Weiss et al. (1981) reported osteoporosis in rats fed high-protein diets. Reducing the protein content of the starter diet of broiler breeder pullets resulted in a significant reduction in body weight to 21 days (Table 3). Assuming 17% CP as a standard, higher protein levels had no consistent effect other than birds fed 20% CP being heavier at 14 and 21 days. With one exception, birds fed less than 17% CP had reduced body weights commensurate with reduced dietary protein level. The pattern of effect of dietary protein level on feed intake was the same as that observed for body weight (Table 4). Carcass composition at 21 days revealed a significant increase in fat content and decrease in protein content in response to reduced diet protein level (Table 5). Starter diets used to 3 weeks influenced body weight only up to 77 days of age (Table 3). Differences in body weight were associated with similar trends in both shank and keel length. Starter diet protein from 20 to 17% had no effect on shank length to 21 days (Table 6). Generally, shank length was decreased at 21 days as protein levels declined from 16 to 13%. Differences in shank length due to starter diet protein level were seen only up to 49 days of age, and in fact, after this time, birds from the lower protein treatments had the longest (P>.05) shanks. A similar pattern emerged for keel length (Table 7), although the carry-over effect of starter diet was evident up to 105 days. At 105 days, the keel length of pullets
1
See Leeson and Summers (1981).
Crude protein, % Metabolizable energy, kcal/kg
Calculated analysis
Total
Ground corn Ground barley Soybean meal (48%) Animal vegetable fat Dicalcium phosphate (20% P) Limestone Iodized salt Mineral vitamin premix i DL-Methionine L-Lysine Alpha floe cellulose
19.0 2898
.95
.94
100.00
.94
100.00
18.0 2904
100.00
.25 .75 .05
.25 .75 .06
50.00 20.00 23.75 1.00 2.00 1.25
.25 .75 .06
3
50.00 17.25 26.50 1.00 2.00 1.25
2
50.00 14.25 29.50 1.00 2.00 1.25
20.0 2892
1
100.00
.95
.25 .75 .05
50.00 22.75 21.00 1.00 2.00 1.25
100.00
.97
.25 .75 .03
47.00 28.65 18.10 1.00 2.00 1.25
16.0 2900
5
Starter diet
17.0 2911
4
TABLE 1. Percentage diet composition
15
100
47 31 13 1 2 1
2907
6
NUTRITION AND PULLET SKELETAL SIZE
1225
TABLE 2. Effect of major nutrient concentration on body weight and frame measurements of 28-day Leghorn chicks Feed intake
Keel length
**
**
**
**
(%) **
297 248
573 537
6.85 6.43
6.12 5.87
51.7 52.8
*
**
NS1
NS
NS
270 275
574 537
6.65 6.64
5.97 6.01
52.2 52.0
NS
NS
NS
NS
NS
272 272
558 552
6.63 6.56
6.02 5.97
52.0 52.3
Treatment
Body weight
Protein 22% 16%
\&i
Fat supplement 1% 6%
Mineral-vitamin premix Regular inclusion Double inclusion
Shank length
Tibia ash
(0111,1
'Significant difference (P<.05). "Significant difference (P<.01). 1
NS, Nonsignificant (P>.05).
previously fed 13% CP was less ( P < . 0 5 ) t h a n t h a t of birds fed 15, 17, or 20% CP. There were no differences in keel length at 161 days (Table 7). Correlation between b o d y weight and parameters of skeletal dimension declined with age (Table 8). Highly significant correlations are seen where b o d y weight differences were imposed through diet t r e a t m e n t . However, w h e n b o d y weights were equalized after 105
days (Table 3), there appeared t o be n o relationship b e t w e e n b o d y weight and shank and keel lengths (Table 8). T h e present results suggest t h a t starter dietary p r o t e i n level, while influencing early skeletal size, has little effect on m a t u r e b o d y weight or skeletal size of broiler b r e e d e r pullets. Early protein intake does initially influence these p a r a m e t e r s ; however, t h e effects are nullified by 105 days with a conventional
TABLE 3. Effect of starter diet protein level on body weight of broiler breeder pullets with common grower diet from 21 days Crude protein 0 to 21 days
Days of age 7
14
21
49
77
105
133
161
no dd
259 e 256 d e 252de 250 d 236 c 196 b 199 b 173 a
477 e 46lde 476 e 455cd 44 2 c 387 b 382b 337 a
881c
1285 b
1714
2095
2688
875 b c
1280b
1703
2070
2648
843ab
1243ab
1692
2084
2657
**
**
*
1661
2073
2643
NS1
NS
NS
(%) 20 19 18 17 16 15 14 13
(g)
110 109 d 108 d 101 c 98b 92b 86a
**
810
a
1216
*
a
a,b,c,d,e;Means within columns followed by different letters are significantly different (**P<.01; *P<.05). 1
NS, Nonsignificant.
LEESON AND SUMMERS
1226
TABLE 4. Effect of starter diet protein level on feed intake of broiler breeder pullets (g) Feed intake
Crude protein in diet
0 to 7 days
7 to 14 days
14 to 21 days
0 to 21 days
96e 95cde 98de 97de 94.bcd 90bc 89b 83a
237 c 237 c 234 c 239 c 231 c 201b 204 b 181 a
389 c d 380bcd 393cd 389cd 397 d 364 b 373bc 337»
725 c 712 c 725 c 724 c 722 c 655b 667b 601a
**
**
**
**
(%) 20 19 18 17 16 15 14 13
a,b,c,d,e Means within columns followed by different letters are significantly different (**P<.01).
TABLE 5. Carcass composition of broiler breeder pullets at 21 days Crude protein in diet
Dry matter
Crude protein
20 19 18 17 16 15 14 13
33.6 a b 33.2a 3 3.9 a b 34.0 b 34.3 b 35.2 C 35.4 C 35.8 C
50.8 d e 52.3 e 49.5cd 50.2 d e 41.7bc 44 9 ab 44.3 a 43.la
38.9 a b 37.7 a 41.6 C 41.3bc 43.2 C 45.8 d 46.8d 47.3 d
**
**
**
Fat
(% I
' ' ' Means within columns followed by different letters are significantly different (**P<.01).
restricted feeding program. Unlike the situation with Leghorn chicks (Table 2), proportional differences seen for the broiler pullets, with extremes of protein intake, are comparable for body weight (17%) shank length (14%) and keel length (21%) at 21 days. The present results confirm that offering breeder pullets very low protein diets will aid in retarding growth. Concern exists that such growth is associated with increased (P<.01) fat deposition (Table 5), although it is expected that the subsequent prolonged period of restricted feeding would nullify this balance. There seems little scope for influencing skeletal dimensions through modification of grower diets, since the normally severe physical feed restriction at this time allows little freedom in
TABLE 6. Shank length of broiler breeder pullets Crude 'protein :er diet, Oto 21. days
1
7
14
21
,
(%) 20 19 18 17 16 15 14 13
Days of age 49
2.89 2.82 2.92 2.92 2.88 2.92 2.92 2.92 NS 1
c
77
105
133
161
s
3.73 3.67 c 3.71 c 3.69 c 3.60 b 3.55 b 3.54 a b 3.48 a
5.31 d 5.26 d 5.26 d 5.23 c d 5.14 c 4.84 b 4.85 b 4.66 a
6.69 d 6.64 d 6.66 d 6.60 c d 6.52 c 6.14 b 6.15 b 5.83 d
8.70 c
10.37
11.21
11.33
11.32
8.80 c
10.58
11.34
11.46
11.46
8.58°
10.40
11.36
11.44
11.41
a
**
**
**
**
10.25 NS
11.22 NS
11.44 NS
11.42 NS
8.45
' ' ' Means within columns followed by different letters are significantly different (**P<.01). 1
NS, Nonsignificant.
NUTRITION AND PULLET SKELETAL SIZE
1227
TABLE 7. Keel length of broiler breeder pullets Crude protein :er diet, Oto 21. days
Days of age 21
14
77
49
105
183
161
,
(%) e
20 19 18 17 16 15 14 13
e
c
(cm) 12.81 c
14.43 b
15.29
15.81
10.43 c
12.77 c
14.49 b
15.42
15.91
b
b
14.39 b
15.28
16.01
6.55 6.50de 6.42 d e 6.34 d 6.15 c 5.62 b 5.59 b 5.25 a
8.12 8.08 d e 7.91 d 8.01de 7.95 d e 7.16 b 7.34 c 6.71 a
10.32
**
**
**
10.05
9.77a
12.52
12.27 a
14.06 a
15.13
15.75
**
*
NS'
NS
a,b,c,d,e Means within columns followed by different letters are significantly different (**P<.01; *P<.05). ' NS, Nonsignificant.
TABLE 8. Correlations between body weight and frame size parameter for different ages of a broiler breeder pullet population fed graded levels of dietary protein from 0 to 21 days Pullet
Body weight: shank length R
Significance
.162 .925 .973 .980 .844 .608 .109 .346 .391
NS
Body weight: keel length
Shank length:keel length
R
Significance
R
Significance
.959 .939 .909 .855 .628 .326 399
** ** ** ** *
,952 .958 .950 .611 .563 .290 .352
** ** ** *
(days) 1 7 14 21 49 77 105 133 161
** ** ** ** * NS NS NS
NS NS
NS NS NS
'NS, Nonsignificant. * Significant:, P-C05. **P<.01.
reducing n u t r i e n t i n t a k e . It seems unlikely t h a t skeletal size can be m a r k e d l y influenced b y n u t r i t i o n w i t h o u t affecting b o d y size due to genetic correlation (Jull and Glazener, 1 9 4 6 ; Nestor, 1 9 7 1 ) ; however, if such action is to be tried, diet modification for greater t h a n 3 weeks seems essential. In this respect, prolonged use of low protein starter diets w i t h o u t recourse t o physical restriction, as proposed by Leeson and S u m m e r s ( 1 9 8 1 ) , m a y be beneficial. ACKNOWLEDGMENTS This work was s u p p o r t e d b y t h e Ontario Ministry of Agriculture and F o o d , Natural
Science and Engineering Research Council of Canada and H u b b a r d F a r m s , Walpole, NH.
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