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Influence of Level of Dietary Fat on the Growth of Dwarf Chickens
Influence of Level of Dietary Fat on the Growth of Dwarf Chickens B. C. KENSETT, S. K. HO,' and S. P. TOUCHBURN Department of Animal Science, Macdonald Campus, McGill University, Ste. Anne de Bellevue, Quebec, Canada HO A ICO (Received for publication January 10, 1978)
1980 Poultry Science 59:2065-2070 INTRODUCTION T h e economic feasibility of using chickens with t h e recessive, sex-linked dwarfism gene (dw) for egg p r o d u c t i o n and as broiler breeding h e n s has been a subject of investigation in r e c e n t years (Bernier and Arscott, I 9 6 0 ; French a n d Nordskog, 1 9 6 9 ; Guillaume, 1 9 6 9 ; J a a p and M o h a m m a d i a n , 1 9 6 9 ; Merat, 1 9 6 9 ; Quisenberry, 1 9 7 1 ; Guillaume, 1 9 7 2 ; Mohamm a d i a n and J a a p , 1972). T h e dwarf chicken has advantages over t h e n o n d w a r f ( D w + ) in commercial p o u l t r y breeding. T h e y m a t u r e t o a smaller size, require less r o o m , and c o n s u m e less feed. However, dwarf chickens have been r e p o r t e d t o develop rickets on a diet a d e q u a t e for t h e growth of n o n d w a r f strains (Austic et ah, 1 9 7 7 ) . These a u t h o r s suggested t h a t t h e dwarf birds were m o r e susceptible t o marginal deficiencies of vitamin D a n d calcium a n d / o r p h o s p h o r u s t h a n nondwarf birds. In addition, dwarf chicks exhibit a lipid m e t a b o l i s m different from t h a t of t h e nondwarfs. It has been d e m o n s t r a t e d t h a t t h e y a c c u m u l a t e m o r e carcass lipid as a result of increased lipogenesis a n d / o r decreased energy e x p e n d i t u r e (Guillaume, 1 9 6 9 ; T o u c h b u r n and Blum, 1 9 7 2 ) .
1 Present address: Feeds Section, Plant Products Division, Agriculture Canada, Ottawa, Ontario K1A OC6.
T h e s t u d y r e p o r t e d herein using growth performance, teristics, a n d mineral status m o n i t o r t h e influence of level growth of dwarf a n d nondwarf
was carried o u t physical characof d i e tibia t o of dietary fat o n birds.
MATERIALS AND METHODS A simplified wheat-soybean meal basal diet was formulated t o c o n t a i n a m i n i m u m of fat (Table 1). T w o levels of supplemental fat (corn oil) were a d d e d t o this basal diet so t h a t t h e crude fat levels in t h e three experimental diets were ca. 1, 6, and 1 1 % , respectively. T h e metabolizable energy levels of t h e diets were held isocaloric b y varying die a m o u n t s of sucrose a n d cellulose. Dwarf ( H 3 0 7 ) a n d n o n d w a r f ( H 2 7 1 ) one-day-old female breeder chicks were o b t a i n e d from Peel's P o u l t r y Farm Ltd., Port Perry, O n t a r i o . T h e y were vaccinated against Marek's disease a n d t h r e e replicate groups of 16 birds of each strain were assigned t o one of t h e t h r e e diets. T h e birds were k e p t in t e m p e r a t u r e - c o n t r o l l e d cages with raised wire floors in a r o o m lighted 14 h r per day and h a d free access t o feed and water. Body weight and feed c o n s u m p t i o n were recorded weekly for each group. Half of t h e birds in each g r o u p were killed by exsanguination at 4 weeks of age and t h e o t h e r half at 8 weeks. Both tibia from each chick were dissected o u t , cleaned of adhering tissues, a n d k e p t
2065
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ABSTRACT Two strains of chickens, dwarf (dw) and nondwarf (Dw + ), and three levels of supplemental dietary fat (none, moderate, and high) were included in a 2 X 3 factorial design to study the effect of dietary fat on growth. The lowered tibial ash, calcium, and phosphorus contents at 4 weeks of age and zinc content at both 4 and 8 weeks of age observed in the dwarf birds may reflect a predisposition to bone abnormalities. Improvements in weight gain (0 to 4 weeks) in response to supplemental dietary fat were observed in all birds but were less pronounced in the dwarfs. At 4 weeks of age, the dwarf birds consuming the fat-supplemented diets had mineral contents of their tibia consistently lower than those of their dwarf counterparts fed the basal diet. At 8 weeks of age, there were no differences between strains in bone mineralization, but the 0 to 8 week weight gains were better for both strains fed the diet supplemented with a moderate level of fat. It appears that optimal bone mineralization of dwarfs to 4 weeks of age occurs at a lower level of dietary fat than that for nondwarfs. Beyond 4 weeks of age, a moderate level of supplemental dietary fat yielded optimal weight gains in both strains of birds. (Key words: fat, growth, dwarf, bone, minerals)
2066
KENSETT ET AL. TABLE 1. Composition of the simplified experimental diets Level of supplemental dietary fat
Ingredients*
Protein % Ether extract, % Metabolizable energy, kcal/kg Calcium, % Phosphorus, %
Moderate
1.25 1.50 .25 .73 .27
39.4 36.6 9.9 5.6 4.5 1.25 1.50 .25 .73 .27
21.7 1.2 2950 .86 .63
21.8 6.1 2951 .89 .64
39.4 36.6 20.0
High
39.4 36.6 11.1 8.9 1.25 1.50 .25 .73 .27 22.0 10.5 2951 .94 .66
Contained 5.5 mg bacitracin-40 and .125 g butylated hydroxy toluene per kilogram of complete diet. To provide the following per kilogram of diet: vitamin A, 3500 IU; vitamin D 3 , 820 ICU; dl-alphatocopheryl acetate, 10 IU; vitamin K 3 , 1.5 mg; riboflavin, 4.84 mg; d-calcium pantothenate, 2.2 mg; pyridoxine HC1, 5.5 mg; folic acid, 1.1 mg; vitamin B j 2 , .01 mg; manganese oxide, 161.54 mg; and zinc oxide, 62.5 mg.
frozen (—20 C) until analyzed. Prior to ashing of each tibia, its weight, length, and the width of its epiphyseal plate were measured. The calcium, zinc, manganese, and copper contents were determined by atomic absorption spectrophotometry (Christian and Feldman, 1970) and phosphorus by colorimetry (AOAC, 1970). The data obtained were analyzed as a 2 X 3 factorial design with two strains of birds (dwarf and nondwarf) and three levels of supplemental dietary fat (none, moderate, and high). The two degrees of freedom for supplemental fat were partitioned into single degree of freedom contrasts of fat supplementation vs. no supplementation and moderate vs. high (Steel and Torrie, 1960).
RESULTS AND DISCUSSION
The dwarf birds gained less weight and consumed less feed than the nondwarfs during both 0 to 4 and 0 to 8 week periods (Table 2). As expected, the tibia of the dwarf birds had lower values for the physical characteristics measured (Table 2). In addition to lowered tibial ash, calcium, and phosphorus (at 4 weeks of age), there was a disproportionately lower
(P<.01) level of zinc, at both 4 and 8 weeks of age, in the tibia of the dwarfs in comparison to that of the nondwarfs (Table 3). Zinc is necessary for the structural integrity of bone, possibly through fibrous collagen formation (Fernandez-Madrid et al, 1976). It is possible that this lowered ash and mineral content reflects a predisposition of the dwarfs to bone abnormalities. This would agree with the previously mentioned observations by Austic et al. (1977) of a greater susceptibility to rickets in dwarf birds. Substitution of fat calories for carbohydrate calories in the diet of the nondwarf birds resulted in improved growth (Table 2). This was similar to results previously reported (Yacowitz et al, 1956; Waibel, 1958; Rand et al, 1958; Touchburn and Naber, 1966; Jensen et al, 1970; Touchburn et al, 1970). Birds fed the basal diet with no added fat had significantly lower weight gains during both 0 to 4 and 0 to 8 week periods. The tibias of these birds also tended to be smaller than those of birds fed the fat supplemented diets (Table 2). However, the high level of supplemental dietary fat reduced the tibial content of ash, calcium, and phosphorus of the 4-week-old nondwarf chicks
Downloaded from http://ps.oxfordjournals.org/ at Purdue University Libraries ADMN on May 22, 2015
Ground wheat Soybean meal (44% protein) Sucrose Cellulose Corn oil Ground limestone Dicalcium phosphate Salt (iodized) Vitamins and minerals b DL-methionine
None
6.40 9.33 2.07 1.39
1133 2771 2.46
3.04 6.58 1.56 1.16
411 866 2.11
None
6.49 9.18 . 2.06 1.39
1197 3016 2.52
3.06 6.49 1.61 1.19
429 887 2.07
Moderate
Dwarf
6.03 8.93 2.04 1.38
1132 2707 2.39
3.10 6.57 1.58 1.23
424 864 2.04
High
Width of epiphyseal plate of tibia.
**P<.01.
*P<.05.
4.06 7.20 1.73 1.40
552 1160 2.10
9.80 10.60 2.39 1.71 10.74 10.71 2.45 1.69
10.32 10.66 2.44 1.69
1541 3664 2.38
4.14 7.24 1.73 1.40
548 1110 2.03
Moderate High
Nondwarf
1490 1602 3801 4007 2.50 2.55
3.72 7.13 1.67 1.31
506 1117 2.21
None
T l , fat supplementation vs. no supplementation; T2, moderate vs. high.
Weight of tibia (g) Length of tibia (cm) Width 0 proximal end (cm) Width 0 distal end (cm)
8 weeks old
Overall gain (g/chick) Feed consumption (g/chick) Feed/gain
0 to 8 weeks
Weight of tibia (g) Length of tibia (cm) Width 0 proximal end (cm) Width 0 distal end (cm)
4 weeks old
Overall gain (g/chick) Feed consumption (g/chick) Feed/gain
0 to 4 weeks
Supplemental dietary fat
Strain
.27 .10 .03 .02
32.2 92.2 .09
.15 .06 .03 .02
11.5 44.4 .08
SE
TABLE 2. Influence of level of dietary fat on growth performance and physical characteristics of the tib
m http://ps.oxfordjournals.org/ at Purdue University Libraries ADMN on May 22, 2015
7.66 8.69
321
55.1 19.9 10.1
6.94 11.49
364
57.4 21.6 10.0
8.22 10.73
9.8 325
9.4 325
5.99 9.64
55.9 20.5
53.9 20.0
6.28 10.78
9.4 353
9.7 368
5.76 10.14
53.0 18.5
55.9 19.2
7.35 11.86
357
**P<.01.
*P<.05.
6.59 9.30
9.9 383
9.9 372 7.62 13.18
56.6 20.9
12.68
6.74
9.9 415
56.5 18.6
High
56.1 19.8
11.92
12.37
58.1 21.1 10.1
6.41
443
58.8 22.5 10.2
9.41
434
58.4 22.6 10.6
' T l , fat supplementation vs. no supplementation; T2, moderate vs. high.
Ash (%) Calcium (%, dry matter) Phosphorus (%, dry matter) Zinc (ppm, ash) Copper (ppm, ash) Manganese (ppm, ash)
8 weeks old
Ash (%) Calcium (%, dry matter) Phosphorus (%, dry matter) Zinc (ppm, ash) Copper (ppm, ash) Manganese (ppm, ash)
4 weeks old
Moderate
None
Supplemental dietary fat
High
Moderate
None
Non-dwarf
Dwarf
Strain
10.46 1.326 1.226
.82 .27
1.52
1.006
20.54 1.135
.91 .55 .24
SE
2
28
2
11 12 7 16 1 3
St
TABLE 3. Ash and mineral content of the tibia of dwarf and nondwarf chi
m http://ps.oxfordjournals.org/ at Purdue University Libraries ADMN on May 22, 2015
DIETARY FAT AND GROWTH
T h e overall weight of t h e dwarf birds was less responsive t o supplemental dietary fat (Table 2). T h e r e was a significant difference ( P < . 0 5 ) b e t w e e n strains when fat s u p p l e m e n t a tion was c o m p a r e d with n o s u p p l e m e n t a t i o n . T h e average p e r c e n t increases in 0 t o 4 week weight gain due t o fat s u p p l e m e n t a t i o n in dwarf and n o n d w a r f chicks were 3.4% and 11.2%, respectively. This smaller increase in b o d y weight was p r o b a b l y due t o t h e supplemental dietary fat being m o r e efficiently conserved by t h e dwarf birds as d e p o t fat instead of being utilized for g r o w t h . T h e physical characteristics of t h e tibia of the dwarf birds were t h e same regardless of the level of s u p p l e m e n t a l dietary fat (Table 3). T h e biologically significant finding is t h a t t h e mineral status of t h e tibia of t h e 4-week-old dwarf birds fed t h e basal diet was consistently higher t h a n t h a t of those receiving t h e fats u p p l e m e n t e d diets. T h e dwarf birds r e s p o n d e d to each higher level of dietary fat with a corresponding decrease in tibial mineral, typically calcium (Table 3), whereas t h e n o n d w a r f s only showed a decrease at t h e high level of supplem e n t a l fat. Because of their p u r p o r t e d predisposition t o b o n e abnormalities as discussed above, it w o u l d appear t h a t lower levels of dietary fat or p e r h a p s mineral s u p p l e m e n t a t i o n would be m o r e desirable for b o n e mineralization in dwarf chicks u p t o 4 weeks of age. However, because of t h e c o m p l e x i t y of mineral n u t r i t i o n , a practical mineral s u p p l e m e n t a t i o n program (i.e., level and kind of mineral elements used) t o achieve optimal b o n e mineralization in dwarf birds c a n n o t be arrived a t w i t h o u t further studies. At 8 weeks of age, however, these differences in degree of mineralization b e t w e e n t h e t w o
strains of birds became negligible. Even t h e margin of difference between t h e t w o strains in t h e c o n t e n t of tibial zinc was n a r r o w e d : 6 9 a n d 4 7 p p m at 4 and 8 weeks, respectively. It is likely t h a t t h e dwarf birds are slower in t h e calcification process during t h e very active growing period b u t eventually d o catch u p t o t h a t of t h e nondwarfs. Beyond this period, b o t h dwarf and n o n d w a r f chicks should perhaps be fed diets containing a m o d e r a t e a m o u n t of supplemental dietary fat. This is s u p p o r t e d by the fact t h a t when t h e entire 8-week p e r i o d was taken into consideration, the diet with t h e m o d e r a t e level of fat resulted in t h e best weight gain for b o t h dwarf and n o n d w a r f birds (Table 2). T h u s , t h e same feeding program c a n n o t be used for b o t h nondwarf and dwarf birds. It would appear t h a t one of the a t t r i b u t e s of a nutritionally efficacious diet for use during t h e active growing phase of birds with t h e recessive, sex-linked dwarfism gene should be a level of supplemental dietary fat lower t h a n those c o m m o n l y used in diets for n o n d w a r f birds. ACKNOWLEDGMENTS T h e a u t h o r s wish to express their appreciation t o Dr. B. W. K e n n e d y for assistance in statistical analyses and i n t e r p r e t a t i o n and t o t h e National Research Council of Canada and t h e Quebec D e p a r t m e n t of E d u c a t i o n for financial s u p p o r t .
REFERENCES Association of Official Analytical Chemists, 1970. Official methods of analysis. 11th ed. AOAC, Washington, DC. Austic, R. E., D. J. Baker, and R. K. Cole, 1977. Susceptibility of a dwarf strain of chickens to rickets. Poultry Sci. 56:285-291. Bernier, P. E., and G. H. Arscott, 1960. Relative efficiency of sex-linked dwarf layers and their normal sisters. Poultry Sci. 39:1234-1235. Christian, G. D., and F. J. Feldman, 1970. Atomic absorption spectroscopy. Applications in agriculture, biology and medicine. Wiley-Interscience, Toronto, Ontario. Fernandez-Madrid, F., A. S. Prasad, and D. Oberleas, 1976. Zinc in collagen metabolism. Pages 257—267 in Trace elements in human health and disease. Vol. I. Zinc and copper, A. S. Prasad and D. Oberleas, ed. Academic Press, New York, NY. French, H. L., and A. W. Nordskog, 1969. Effects of the sex-linked dwarf gene on performance of large and small Leghorn crosses. Poultry Sci. 48:1809. (Abstr.) Griffith, F. D., R. B. Grainger, and John J. Begin,
Downloaded from http://ps.oxfordjournals.org/ at Purdue University Libraries ADMN on May 22, 2015
(Table 3). Griffith et al. ( 1 9 6 1 ) reported a similar finding in t h e b o n e ash c o n t e n t . T h e a p p a r e n t calcium digestibilities of t h e diets used by these a u t h o r s , having dietary fat-cellulose levels similar t o t h o s e in t h e three diets (none, m o d e r a t e , high) (Table 1) used in t h e present s t u d y were 6 4 . 6 3 , 6 1 . 5 4 , and 39.66%, respectively. On t h e basis of their work, t h e presently observed changes in tibial mineral c o n t e n t could be a t t r i b u t a b l e t o a reduction in the calcium availability in t h e high fat diet. In view of these findings, it is possible t h a t t h e generally accepted ( S u m m e r s and Leeson, 1978) practice of including m o d e r a t e levels of fat in p o u l t r y diets results in optimal growth and b o n e mineralization.
2069
2070
KENSETT ET AL. Dietary fat in the nutrition of the growing chick. Poultry Sci. 37:1075-1085. Steel, R.G.D., and J. H. Torrie, 1960. Principles and procedures of statistics. McGraw-Hill Book Co., Inc. New York, NY. Summers, J. D., and S. Leeson, 1978. Poultry nutrition handbook. Agdex 450/50. Ontario Min. Agr. Food, Toronto, Ontario. Touchburn, S. P., and J. C. Blum, 1972. Effects of the genes for dwarfism (dw) and naked neck (Na) on chick growth and lipid metabolism. Ann. Ge"net. Sel Anim. 4:311-316. Touchburn, S. P., K. I. Brown, and M. Topscher, 1970. The effect of light intensity and dietary fat on the growth performance of turkeys. Pages 9 9 - 1 0 5 in Proc. 14th. World's Poultry Congr., Madrid, Spain. Touchburn, S. P., and E. C. Naber, 1966. The energy value of fats for growing turkeys. Pages 190—195 in Proc. 13th World's Poultry Congress, Kiev, USSR. Waibel, P. E., 1958. Effectiveness of unknown growth factors, antibiotics and animal fat in turkey poult rations. Poultry Sci. 37:1144-1149. Yacowitz, H., R. D. Carter, J. Wyne, and M. G. McCartney, 1956. Effects of varying protein and fat levels in a finishing ration for turkey broilers. Poultry Sci. 35:227-229.
Downloaded from http://ps.oxfordjournals.org/ at Purdue University Libraries ADMN on May 22, 2015
1961. The effect of dietary fat and cellulose on apparent calcium digestibility in growing chickens. Poultry Sci. 40:1492-1497. Guillaume, J., 1969. Conse'quences de l'introduction du gene de nanismedtu sur l'utilisation alimentaire chez le poussin femelle. Ann. Biol. Anim. Bioch. Biophys. 9:369-378. Guillaume, J., 1972. Donnees comple'mentaires sur les besoins nutritionnels de la reproductrice naine Vedette I.N.R.A. JV15. Ann. Gene't. Sel. Anim. 4:281-295. Jaap, R. G., and M. Mohammadian, 1969. Sex-linked dwarfism and egg production of broiler dams. Poultry Sci. 48:344-346. Jensen, L. S., G. W. Schumaier, and J. D. Latshaw, 1970. "Extra caloric" effect of dietary fat for developing turkeys as influenced by calorie-protein ratio. Poultry Sci. 49:1697-1704. Me'rat, P., 1969. Etude d'un gene de nanisme lie' au sexe chez la poule. Ann. Genet. Sel. Anim. 1:19-26. Mohammadian, M., and R. G. Jaap, 1972. Effect of the sex-linked dwarfing gene on body growth of chickens. Poultry Sci. 51:1701-1707. Quisenberry, J. H., 1971. Symposium on the dwarf (dw) gene in chickens. World's Poultry Sci. J. 27:276-292. Rand, N. T., H. M. Scott, and F. A. Kummerow, 1958.
1980 Poultry Science 59:2065-2070 INTRODUCTION T h e economic feasibility of using chickens with t h e recessive, sex-linked dwarfism gene (dw) for egg p r o d u c t i o n and as broiler breeding h e n s has been a subject of investigation in r e c e n t years (Bernier and Arscott, I 9 6 0 ; French a n d Nordskog, 1 9 6 9 ; Guillaume, 1 9 6 9 ; J a a p and M o h a m m a d i a n , 1 9 6 9 ; Merat, 1 9 6 9 ; Quisenberry, 1 9 7 1 ; Guillaume, 1 9 7 2 ; Mohamm a d i a n and J a a p , 1972). T h e dwarf chicken has advantages over t h e n o n d w a r f ( D w + ) in commercial p o u l t r y breeding. T h e y m a t u r e t o a smaller size, require less r o o m , and c o n s u m e less feed. However, dwarf chickens have been r e p o r t e d t o develop rickets on a diet a d e q u a t e for t h e growth of n o n d w a r f strains (Austic et ah, 1 9 7 7 ) . These a u t h o r s suggested t h a t t h e dwarf birds were m o r e susceptible t o marginal deficiencies of vitamin D a n d calcium a n d / o r p h o s p h o r u s t h a n nondwarf birds. In addition, dwarf chicks exhibit a lipid m e t a b o l i s m different from t h a t of t h e nondwarfs. It has been d e m o n s t r a t e d t h a t t h e y a c c u m u l a t e m o r e carcass lipid as a result of increased lipogenesis a n d / o r decreased energy e x p e n d i t u r e (Guillaume, 1 9 6 9 ; T o u c h b u r n and Blum, 1 9 7 2 ) .
1 Present address: Feeds Section, Plant Products Division, Agriculture Canada, Ottawa, Ontario K1A OC6.
T h e s t u d y r e p o r t e d herein using growth performance, teristics, a n d mineral status m o n i t o r t h e influence of level growth of dwarf a n d nondwarf
was carried o u t physical characof d i e tibia t o of dietary fat o n birds.
MATERIALS AND METHODS A simplified wheat-soybean meal basal diet was formulated t o c o n t a i n a m i n i m u m of fat (Table 1). T w o levels of supplemental fat (corn oil) were a d d e d t o this basal diet so t h a t t h e crude fat levels in t h e three experimental diets were ca. 1, 6, and 1 1 % , respectively. T h e metabolizable energy levels of t h e diets were held isocaloric b y varying die a m o u n t s of sucrose a n d cellulose. Dwarf ( H 3 0 7 ) a n d n o n d w a r f ( H 2 7 1 ) one-day-old female breeder chicks were o b t a i n e d from Peel's P o u l t r y Farm Ltd., Port Perry, O n t a r i o . T h e y were vaccinated against Marek's disease a n d t h r e e replicate groups of 16 birds of each strain were assigned t o one of t h e t h r e e diets. T h e birds were k e p t in t e m p e r a t u r e - c o n t r o l l e d cages with raised wire floors in a r o o m lighted 14 h r per day and h a d free access t o feed and water. Body weight and feed c o n s u m p t i o n were recorded weekly for each group. Half of t h e birds in each g r o u p were killed by exsanguination at 4 weeks of age and t h e o t h e r half at 8 weeks. Both tibia from each chick were dissected o u t , cleaned of adhering tissues, a n d k e p t
2065
Downloaded from http://ps.oxfordjournals.org/ at Purdue University Libraries ADMN on May 22, 2015
ABSTRACT Two strains of chickens, dwarf (dw) and nondwarf (Dw + ), and three levels of supplemental dietary fat (none, moderate, and high) were included in a 2 X 3 factorial design to study the effect of dietary fat on growth. The lowered tibial ash, calcium, and phosphorus contents at 4 weeks of age and zinc content at both 4 and 8 weeks of age observed in the dwarf birds may reflect a predisposition to bone abnormalities. Improvements in weight gain (0 to 4 weeks) in response to supplemental dietary fat were observed in all birds but were less pronounced in the dwarfs. At 4 weeks of age, the dwarf birds consuming the fat-supplemented diets had mineral contents of their tibia consistently lower than those of their dwarf counterparts fed the basal diet. At 8 weeks of age, there were no differences between strains in bone mineralization, but the 0 to 8 week weight gains were better for both strains fed the diet supplemented with a moderate level of fat. It appears that optimal bone mineralization of dwarfs to 4 weeks of age occurs at a lower level of dietary fat than that for nondwarfs. Beyond 4 weeks of age, a moderate level of supplemental dietary fat yielded optimal weight gains in both strains of birds. (Key words: fat, growth, dwarf, bone, minerals)
2066
KENSETT ET AL. TABLE 1. Composition of the simplified experimental diets Level of supplemental dietary fat
Ingredients*
Protein % Ether extract, % Metabolizable energy, kcal/kg Calcium, % Phosphorus, %
Moderate
1.25 1.50 .25 .73 .27
39.4 36.6 9.9 5.6 4.5 1.25 1.50 .25 .73 .27
21.7 1.2 2950 .86 .63
21.8 6.1 2951 .89 .64
39.4 36.6 20.0
High
39.4 36.6 11.1 8.9 1.25 1.50 .25 .73 .27 22.0 10.5 2951 .94 .66
Contained 5.5 mg bacitracin-40 and .125 g butylated hydroxy toluene per kilogram of complete diet. To provide the following per kilogram of diet: vitamin A, 3500 IU; vitamin D 3 , 820 ICU; dl-alphatocopheryl acetate, 10 IU; vitamin K 3 , 1.5 mg; riboflavin, 4.84 mg; d-calcium pantothenate, 2.2 mg; pyridoxine HC1, 5.5 mg; folic acid, 1.1 mg; vitamin B j 2 , .01 mg; manganese oxide, 161.54 mg; and zinc oxide, 62.5 mg.
frozen (—20 C) until analyzed. Prior to ashing of each tibia, its weight, length, and the width of its epiphyseal plate were measured. The calcium, zinc, manganese, and copper contents were determined by atomic absorption spectrophotometry (Christian and Feldman, 1970) and phosphorus by colorimetry (AOAC, 1970). The data obtained were analyzed as a 2 X 3 factorial design with two strains of birds (dwarf and nondwarf) and three levels of supplemental dietary fat (none, moderate, and high). The two degrees of freedom for supplemental fat were partitioned into single degree of freedom contrasts of fat supplementation vs. no supplementation and moderate vs. high (Steel and Torrie, 1960).
RESULTS AND DISCUSSION
The dwarf birds gained less weight and consumed less feed than the nondwarfs during both 0 to 4 and 0 to 8 week periods (Table 2). As expected, the tibia of the dwarf birds had lower values for the physical characteristics measured (Table 2). In addition to lowered tibial ash, calcium, and phosphorus (at 4 weeks of age), there was a disproportionately lower
(P<.01) level of zinc, at both 4 and 8 weeks of age, in the tibia of the dwarfs in comparison to that of the nondwarfs (Table 3). Zinc is necessary for the structural integrity of bone, possibly through fibrous collagen formation (Fernandez-Madrid et al, 1976). It is possible that this lowered ash and mineral content reflects a predisposition of the dwarfs to bone abnormalities. This would agree with the previously mentioned observations by Austic et al. (1977) of a greater susceptibility to rickets in dwarf birds. Substitution of fat calories for carbohydrate calories in the diet of the nondwarf birds resulted in improved growth (Table 2). This was similar to results previously reported (Yacowitz et al, 1956; Waibel, 1958; Rand et al, 1958; Touchburn and Naber, 1966; Jensen et al, 1970; Touchburn et al, 1970). Birds fed the basal diet with no added fat had significantly lower weight gains during both 0 to 4 and 0 to 8 week periods. The tibias of these birds also tended to be smaller than those of birds fed the fat supplemented diets (Table 2). However, the high level of supplemental dietary fat reduced the tibial content of ash, calcium, and phosphorus of the 4-week-old nondwarf chicks
Downloaded from http://ps.oxfordjournals.org/ at Purdue University Libraries ADMN on May 22, 2015
Ground wheat Soybean meal (44% protein) Sucrose Cellulose Corn oil Ground limestone Dicalcium phosphate Salt (iodized) Vitamins and minerals b DL-methionine
None
6.40 9.33 2.07 1.39
1133 2771 2.46
3.04 6.58 1.56 1.16
411 866 2.11
None
6.49 9.18 . 2.06 1.39
1197 3016 2.52
3.06 6.49 1.61 1.19
429 887 2.07
Moderate
Dwarf
6.03 8.93 2.04 1.38
1132 2707 2.39
3.10 6.57 1.58 1.23
424 864 2.04
High
Width of epiphyseal plate of tibia.
**P<.01.
*P<.05.
4.06 7.20 1.73 1.40
552 1160 2.10
9.80 10.60 2.39 1.71 10.74 10.71 2.45 1.69
10.32 10.66 2.44 1.69
1541 3664 2.38
4.14 7.24 1.73 1.40
548 1110 2.03
Moderate High
Nondwarf
1490 1602 3801 4007 2.50 2.55
3.72 7.13 1.67 1.31
506 1117 2.21
None
T l , fat supplementation vs. no supplementation; T2, moderate vs. high.
Weight of tibia (g) Length of tibia (cm) Width 0 proximal end (cm) Width 0 distal end (cm)
8 weeks old
Overall gain (g/chick) Feed consumption (g/chick) Feed/gain
0 to 8 weeks
Weight of tibia (g) Length of tibia (cm) Width 0 proximal end (cm) Width 0 distal end (cm)
4 weeks old
Overall gain (g/chick) Feed consumption (g/chick) Feed/gain
0 to 4 weeks
Supplemental dietary fat
Strain
.27 .10 .03 .02
32.2 92.2 .09
.15 .06 .03 .02
11.5 44.4 .08
SE
TABLE 2. Influence of level of dietary fat on growth performance and physical characteristics of the tib
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7.66 8.69
321
55.1 19.9 10.1
6.94 11.49
364
57.4 21.6 10.0
8.22 10.73
9.8 325
9.4 325
5.99 9.64
55.9 20.5
53.9 20.0
6.28 10.78
9.4 353
9.7 368
5.76 10.14
53.0 18.5
55.9 19.2
7.35 11.86
357
**P<.01.
*P<.05.
6.59 9.30
9.9 383
9.9 372 7.62 13.18
56.6 20.9
12.68
6.74
9.9 415
56.5 18.6
High
56.1 19.8
11.92
12.37
58.1 21.1 10.1
6.41
443
58.8 22.5 10.2
9.41
434
58.4 22.6 10.6
' T l , fat supplementation vs. no supplementation; T2, moderate vs. high.
Ash (%) Calcium (%, dry matter) Phosphorus (%, dry matter) Zinc (ppm, ash) Copper (ppm, ash) Manganese (ppm, ash)
8 weeks old
Ash (%) Calcium (%, dry matter) Phosphorus (%, dry matter) Zinc (ppm, ash) Copper (ppm, ash) Manganese (ppm, ash)
4 weeks old
Moderate
None
Supplemental dietary fat
High
Moderate
None
Non-dwarf
Dwarf
Strain
10.46 1.326 1.226
.82 .27
1.52
1.006
20.54 1.135
.91 .55 .24
SE
2
28
2
11 12 7 16 1 3
St
TABLE 3. Ash and mineral content of the tibia of dwarf and nondwarf chi
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DIETARY FAT AND GROWTH
T h e overall weight of t h e dwarf birds was less responsive t o supplemental dietary fat (Table 2). T h e r e was a significant difference ( P < . 0 5 ) b e t w e e n strains when fat s u p p l e m e n t a tion was c o m p a r e d with n o s u p p l e m e n t a t i o n . T h e average p e r c e n t increases in 0 t o 4 week weight gain due t o fat s u p p l e m e n t a t i o n in dwarf and n o n d w a r f chicks were 3.4% and 11.2%, respectively. This smaller increase in b o d y weight was p r o b a b l y due t o t h e supplemental dietary fat being m o r e efficiently conserved by t h e dwarf birds as d e p o t fat instead of being utilized for g r o w t h . T h e physical characteristics of t h e tibia of the dwarf birds were t h e same regardless of the level of s u p p l e m e n t a l dietary fat (Table 3). T h e biologically significant finding is t h a t t h e mineral status of t h e tibia of t h e 4-week-old dwarf birds fed t h e basal diet was consistently higher t h a n t h a t of those receiving t h e fats u p p l e m e n t e d diets. T h e dwarf birds r e s p o n d e d to each higher level of dietary fat with a corresponding decrease in tibial mineral, typically calcium (Table 3), whereas t h e n o n d w a r f s only showed a decrease at t h e high level of supplem e n t a l fat. Because of their p u r p o r t e d predisposition t o b o n e abnormalities as discussed above, it w o u l d appear t h a t lower levels of dietary fat or p e r h a p s mineral s u p p l e m e n t a t i o n would be m o r e desirable for b o n e mineralization in dwarf chicks u p t o 4 weeks of age. However, because of t h e c o m p l e x i t y of mineral n u t r i t i o n , a practical mineral s u p p l e m e n t a t i o n program (i.e., level and kind of mineral elements used) t o achieve optimal b o n e mineralization in dwarf birds c a n n o t be arrived a t w i t h o u t further studies. At 8 weeks of age, however, these differences in degree of mineralization b e t w e e n t h e t w o
strains of birds became negligible. Even t h e margin of difference between t h e t w o strains in t h e c o n t e n t of tibial zinc was n a r r o w e d : 6 9 a n d 4 7 p p m at 4 and 8 weeks, respectively. It is likely t h a t t h e dwarf birds are slower in t h e calcification process during t h e very active growing period b u t eventually d o catch u p t o t h a t of t h e nondwarfs. Beyond this period, b o t h dwarf and n o n d w a r f chicks should perhaps be fed diets containing a m o d e r a t e a m o u n t of supplemental dietary fat. This is s u p p o r t e d by the fact t h a t when t h e entire 8-week p e r i o d was taken into consideration, the diet with t h e m o d e r a t e level of fat resulted in t h e best weight gain for b o t h dwarf and n o n d w a r f birds (Table 2). T h u s , t h e same feeding program c a n n o t be used for b o t h nondwarf and dwarf birds. It would appear t h a t one of the a t t r i b u t e s of a nutritionally efficacious diet for use during t h e active growing phase of birds with t h e recessive, sex-linked dwarfism gene should be a level of supplemental dietary fat lower t h a n those c o m m o n l y used in diets for n o n d w a r f birds. ACKNOWLEDGMENTS T h e a u t h o r s wish to express their appreciation t o Dr. B. W. K e n n e d y for assistance in statistical analyses and i n t e r p r e t a t i o n and t o t h e National Research Council of Canada and t h e Quebec D e p a r t m e n t of E d u c a t i o n for financial s u p p o r t .
REFERENCES Association of Official Analytical Chemists, 1970. Official methods of analysis. 11th ed. AOAC, Washington, DC. Austic, R. E., D. J. Baker, and R. K. Cole, 1977. Susceptibility of a dwarf strain of chickens to rickets. Poultry Sci. 56:285-291. Bernier, P. E., and G. H. Arscott, 1960. Relative efficiency of sex-linked dwarf layers and their normal sisters. Poultry Sci. 39:1234-1235. Christian, G. D., and F. J. Feldman, 1970. Atomic absorption spectroscopy. Applications in agriculture, biology and medicine. Wiley-Interscience, Toronto, Ontario. Fernandez-Madrid, F., A. S. Prasad, and D. Oberleas, 1976. Zinc in collagen metabolism. Pages 257—267 in Trace elements in human health and disease. Vol. I. Zinc and copper, A. S. Prasad and D. Oberleas, ed. Academic Press, New York, NY. French, H. L., and A. W. Nordskog, 1969. Effects of the sex-linked dwarf gene on performance of large and small Leghorn crosses. Poultry Sci. 48:1809. (Abstr.) Griffith, F. D., R. B. Grainger, and John J. Begin,
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(Table 3). Griffith et al. ( 1 9 6 1 ) reported a similar finding in t h e b o n e ash c o n t e n t . T h e a p p a r e n t calcium digestibilities of t h e diets used by these a u t h o r s , having dietary fat-cellulose levels similar t o t h o s e in t h e three diets (none, m o d e r a t e , high) (Table 1) used in t h e present s t u d y were 6 4 . 6 3 , 6 1 . 5 4 , and 39.66%, respectively. On t h e basis of their work, t h e presently observed changes in tibial mineral c o n t e n t could be a t t r i b u t a b l e t o a reduction in the calcium availability in t h e high fat diet. In view of these findings, it is possible t h a t t h e generally accepted ( S u m m e r s and Leeson, 1978) practice of including m o d e r a t e levels of fat in p o u l t r y diets results in optimal growth and b o n e mineralization.
2069
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1961. The effect of dietary fat and cellulose on apparent calcium digestibility in growing chickens. Poultry Sci. 40:1492-1497. Guillaume, J., 1969. Conse'quences de l'introduction du gene de nanismedtu sur l'utilisation alimentaire chez le poussin femelle. Ann. Biol. Anim. Bioch. Biophys. 9:369-378. Guillaume, J., 1972. Donnees comple'mentaires sur les besoins nutritionnels de la reproductrice naine Vedette I.N.R.A. JV15. Ann. Gene't. Sel. Anim. 4:281-295. Jaap, R. G., and M. Mohammadian, 1969. Sex-linked dwarfism and egg production of broiler dams. Poultry Sci. 48:344-346. Jensen, L. S., G. W. Schumaier, and J. D. Latshaw, 1970. "Extra caloric" effect of dietary fat for developing turkeys as influenced by calorie-protein ratio. Poultry Sci. 49:1697-1704. Me'rat, P., 1969. Etude d'un gene de nanisme lie' au sexe chez la poule. Ann. Genet. Sel. Anim. 1:19-26. Mohammadian, M., and R. G. Jaap, 1972. Effect of the sex-linked dwarfing gene on body growth of chickens. Poultry Sci. 51:1701-1707. Quisenberry, J. H., 1971. Symposium on the dwarf (dw) gene in chickens. World's Poultry Sci. J. 27:276-292. Rand, N. T., H. M. Scott, and F. A. Kummerow, 1958.