The Effect of Sex, Dietary Energy, Meat Protein, Ascorbic Acid and Iron on Broiler Skin Collagen T. W. SMITH, JR., J. R. COUCH, R. L. GARRETT 1 and C. R. CREGER Departments of Poultry Science and Biochemistry-Biophysics, Texas Agriculture Experiment Station, Texas A&M University, College Station, Texas 77843 (Received for publication November 17, 1976)
Poultry Science 56:1216-1220, 1977 INTRODUCTION Recently a p r o b l e m has been observed in broiler processing p l a n t s which has been referred t o as t h e "oily b i r d " s y n d r o m e (OBS), and is characterized by broilers with extremely t e n d e r skin ( G a r r e t t , 1 9 7 5 ) . It has been reported t o occur m o r e often in female broilers and those broilers which are nine weeks of age or older ( E d w a r d s et al., 1 9 7 3 ; K u b e n a et al., 1 9 7 4 ) . T h e percentage of b o d y fat has been reported t o increase in older broilers and females as well as birds fed diets with high energy-protein ratios (Donaldson et al., 1 9 5 6 ; Summers et al., 1 9 6 5 ) . These findings indicate t h a t t h e energy m e t a b o l i s m m a y be involved. Garrett n o t e d t h a t O B S w a s often observed w h e n 7.5% or 10% of t h e diet was composed of animal b y - p r o d u c t s or dried bakery p r o d u c t s . Garrett suggested t h a t t h e OBS was caused b y a nutritional imbalance or specific nutrient deficiency, and appears only after high stress factors such as high scalding vat t e m p e r a t u r e s are e n c o u n t e r e d at t h e processing plant. A reduction in t h e structural integrity a n d / o r a m o u n t of t h e connective tissue, of which collagen is t h e major c o m p o n e n t , was suggested
1 Research and Development, Adams Laboratories, Fairfax, VA 22030.
as being t h e possible site of t h e imbalance or deficiency. A r e d u c t i o n in t h e t o t a l and saltinsoluble collagen levels of skin tissue were observed w h e n broilers were fed high energy diets during a period of high environmental t e m p e r a t u r e s (Smith et al., 1976). Collagen is t h e basic p o l y p e p t i d e in connective tissue responsible for t h e structural integrity of all muscle and skin tissues. T h e collagen molecule is c o m p o s e d of t h r e e p o l y p e p t i d e chains held t o g e t h e r in a helical a r r a n g e m e n t by i n t r a m o l e c u l a r b o n d s . After t h e p o l y p e p t i d e chains are formed in ribosomes of t h e fibroblast cells, certain proline and lysine residues m u s t be h y d r o x y l a t e d before t h e f o r m a t i o n of collagen fibers can take place (Prockop, 1 9 7 0 ) . It is n o t k n o w n which steps control collagen synthesis, b u t studies suggest t h a t t h e h y d r o x y l a t i o n of proline and lysine residues is t h e rate limiting step (Popper and Becker, 1975). F e r r o u s ions and ascorbic acid are required for t h e activity of t h e oxygenase e n z y m e which h y d r o x y l a t e s t h e proline residues (Peterkofsky and Udenfriend, 1 9 6 5 ; P r o c k o p and Juva, 1 9 6 5 ) . PROCEDURE Experiment I. Ten male and 10 female broiler t y p e day-old chicks were r a n d o m l y allotted t o each of eight t r e a t m e n t g r o u p s . Each g r o u p was fed a diet which except for t h e
1216
Downloaded from http://ps.oxfordjournals.org/ at Michigan State University on March 22, 2015
ABSTRACT Two studies were conducted to determine if variation of sex, dietary energy, meat protein, ascorbic acid or iron had any effect on collagen metabolism in broilers. In the first experiment day-old broiler type chicks were fed diets which contained 3190 or 3410 kcal. M.E./kg. of diet, 0 or 15% meat and bone meal and 0 or 1 g./kg. ascorbic acid. In the second experiment the day-old broiler chicks were fed diets which had 3190 or 3410 kcal. M.E./kg. of diet and 60 or 260 p.p.m. of iron. At 56 days of age the broilers were weighed, a representative number of birds killed from each group and skin samples collected. The skin samples were analyzed for the degree of collagen cross-linking and the total and insoluble collagen contents. An alteration of energy, meat protein, ascorbic acid or iron in the diet had no effect on collagen formation in the skin of broilers reared in cool environmental temperatures. Female broilers had a significantly higher percentage of insoluble collagen in the skin tissue but the level of total collagen and insoluble collagen was higher in male birds.
BROILER SKIN COLLAGEN
1217
M.E./kg. of diet, whereas diets 2 and 4 contained 3410 kcal. M.E./kg. of diet. Diets 1 and 2 were supplemented with 200 mg./kg. of iron in the form of ferrous sulfate, but diets 3 and 4 remained unsupplemented. Technical grade calcium carbonate and monobasic calcium phosphate were used to replace oyster shell and defluorinated rock phosphate to reduce the iron level to a minimum. The diets not supplemented with ferrous sulfate had a calculated iron level of 60 p.p.m. which is below the level recommended by the N.R.C. At 56 days of age the broilers were weighed and tissue samples taken from eight broilers of each sex in each treatment. The tissue samples were analyzed as in Experiment 1. The mean data for all parameters in each experiment were subjected to the appropriate analysis of variance procedures (Steele and Torrie, 1960) to determine the effects of sex or dietary factors.
Experiment 2. Twelve male and 12 female broiler type day-old chicks were randomly assigned to each of four treatment groups composed of two replicates per treatment. Each treatment group was fed a diet which varied in either energy level and/or ferrous ion concentration. Diets 1 and 3 contained 3190 kcal.
Experiment I. The broilers in these studies were reared during the cooler season of the year in the months of December and January. In this experiment no differences in collagen crosslinking or insoluble collagen content were observed which could be attributed to any of the individual diets (Table 1). Total collagen
RESULTS AND DISCUSSION
TABLE 1.—Total skin collagen, degree of collagen cross-linking, insoluble skin collagen and body weight of broilers fed diets in experiment 1
Treatment'
Diet 1 (3190 kcal. M.E./kg.) Diet 2 (3410 kcal. M.E./kg.) Diet 3 (3190 kcal. M.E./kg., 1 g./kg. ascorbic acid) Diet 4 (3410 kcal. M.E./kg., 1 g./kg. ascorbic acid) Diet 5 (3190 kcal. M.E./kg., 15% meat protein) Diet 6 (3410 kcal. M.E./kg., 15% meat protein) Diet 7 (3190 kcal. M.E./kg., 1 g./kg. ascorbic acid, 15% meat protein) Diet 8 (3410 kcal. M.E./kg., 1 g./kg. ascorbic acid, 15% meat protein)
Total collagen
Collagen X-linking
Insoluble collagen
Body2 weight
(mg./g.)
(%)
(mg./g.)
(g-)
425.0a 453.7a
a
29.1 26.5 a
a
109.6 123.4a
2001 a b 1905 a b
490.6 ab
25.8a
123.7a
1871 a b
539.7b
27.0a
144.4a
1783 a
504.6°
23.9a
117.7a
1905 a b
481.2 ab
26.7 a
120.2a
1855 a
436.5 a
24.0a
103.8a
2064b
431.8a
25.0a
104.1a
1888 ab
'Within each column, means bearing different superscripts are significantly different (P
Poultry Science 56:1216-1220, 1977 INTRODUCTION Recently a p r o b l e m has been observed in broiler processing p l a n t s which has been referred t o as t h e "oily b i r d " s y n d r o m e (OBS), and is characterized by broilers with extremely t e n d e r skin ( G a r r e t t , 1 9 7 5 ) . It has been reported t o occur m o r e often in female broilers and those broilers which are nine weeks of age or older ( E d w a r d s et al., 1 9 7 3 ; K u b e n a et al., 1 9 7 4 ) . T h e percentage of b o d y fat has been reported t o increase in older broilers and females as well as birds fed diets with high energy-protein ratios (Donaldson et al., 1 9 5 6 ; Summers et al., 1 9 6 5 ) . These findings indicate t h a t t h e energy m e t a b o l i s m m a y be involved. Garrett n o t e d t h a t O B S w a s often observed w h e n 7.5% or 10% of t h e diet was composed of animal b y - p r o d u c t s or dried bakery p r o d u c t s . Garrett suggested t h a t t h e OBS was caused b y a nutritional imbalance or specific nutrient deficiency, and appears only after high stress factors such as high scalding vat t e m p e r a t u r e s are e n c o u n t e r e d at t h e processing plant. A reduction in t h e structural integrity a n d / o r a m o u n t of t h e connective tissue, of which collagen is t h e major c o m p o n e n t , was suggested
1 Research and Development, Adams Laboratories, Fairfax, VA 22030.
as being t h e possible site of t h e imbalance or deficiency. A r e d u c t i o n in t h e t o t a l and saltinsoluble collagen levels of skin tissue were observed w h e n broilers were fed high energy diets during a period of high environmental t e m p e r a t u r e s (Smith et al., 1976). Collagen is t h e basic p o l y p e p t i d e in connective tissue responsible for t h e structural integrity of all muscle and skin tissues. T h e collagen molecule is c o m p o s e d of t h r e e p o l y p e p t i d e chains held t o g e t h e r in a helical a r r a n g e m e n t by i n t r a m o l e c u l a r b o n d s . After t h e p o l y p e p t i d e chains are formed in ribosomes of t h e fibroblast cells, certain proline and lysine residues m u s t be h y d r o x y l a t e d before t h e f o r m a t i o n of collagen fibers can take place (Prockop, 1 9 7 0 ) . It is n o t k n o w n which steps control collagen synthesis, b u t studies suggest t h a t t h e h y d r o x y l a t i o n of proline and lysine residues is t h e rate limiting step (Popper and Becker, 1975). F e r r o u s ions and ascorbic acid are required for t h e activity of t h e oxygenase e n z y m e which h y d r o x y l a t e s t h e proline residues (Peterkofsky and Udenfriend, 1 9 6 5 ; P r o c k o p and Juva, 1 9 6 5 ) . PROCEDURE Experiment I. Ten male and 10 female broiler t y p e day-old chicks were r a n d o m l y allotted t o each of eight t r e a t m e n t g r o u p s . Each g r o u p was fed a diet which except for t h e
1216
Downloaded from http://ps.oxfordjournals.org/ at Michigan State University on March 22, 2015
ABSTRACT Two studies were conducted to determine if variation of sex, dietary energy, meat protein, ascorbic acid or iron had any effect on collagen metabolism in broilers. In the first experiment day-old broiler type chicks were fed diets which contained 3190 or 3410 kcal. M.E./kg. of diet, 0 or 15% meat and bone meal and 0 or 1 g./kg. ascorbic acid. In the second experiment the day-old broiler chicks were fed diets which had 3190 or 3410 kcal. M.E./kg. of diet and 60 or 260 p.p.m. of iron. At 56 days of age the broilers were weighed, a representative number of birds killed from each group and skin samples collected. The skin samples were analyzed for the degree of collagen cross-linking and the total and insoluble collagen contents. An alteration of energy, meat protein, ascorbic acid or iron in the diet had no effect on collagen formation in the skin of broilers reared in cool environmental temperatures. Female broilers had a significantly higher percentage of insoluble collagen in the skin tissue but the level of total collagen and insoluble collagen was higher in male birds.
BROILER SKIN COLLAGEN
1217
M.E./kg. of diet, whereas diets 2 and 4 contained 3410 kcal. M.E./kg. of diet. Diets 1 and 2 were supplemented with 200 mg./kg. of iron in the form of ferrous sulfate, but diets 3 and 4 remained unsupplemented. Technical grade calcium carbonate and monobasic calcium phosphate were used to replace oyster shell and defluorinated rock phosphate to reduce the iron level to a minimum. The diets not supplemented with ferrous sulfate had a calculated iron level of 60 p.p.m. which is below the level recommended by the N.R.C. At 56 days of age the broilers were weighed and tissue samples taken from eight broilers of each sex in each treatment. The tissue samples were analyzed as in Experiment 1. The mean data for all parameters in each experiment were subjected to the appropriate analysis of variance procedures (Steele and Torrie, 1960) to determine the effects of sex or dietary factors.
Experiment 2. Twelve male and 12 female broiler type day-old chicks were randomly assigned to each of four treatment groups composed of two replicates per treatment. Each treatment group was fed a diet which varied in either energy level and/or ferrous ion concentration. Diets 1 and 3 contained 3190 kcal.
Experiment I. The broilers in these studies were reared during the cooler season of the year in the months of December and January. In this experiment no differences in collagen crosslinking or insoluble collagen content were observed which could be attributed to any of the individual diets (Table 1). Total collagen
RESULTS AND DISCUSSION
TABLE 1.—Total skin collagen, degree of collagen cross-linking, insoluble skin collagen and body weight of broilers fed diets in experiment 1
Treatment'
Diet 1 (3190 kcal. M.E./kg.) Diet 2 (3410 kcal. M.E./kg.) Diet 3 (3190 kcal. M.E./kg., 1 g./kg. ascorbic acid) Diet 4 (3410 kcal. M.E./kg., 1 g./kg. ascorbic acid) Diet 5 (3190 kcal. M.E./kg., 15% meat protein) Diet 6 (3410 kcal. M.E./kg., 15% meat protein) Diet 7 (3190 kcal. M.E./kg., 1 g./kg. ascorbic acid, 15% meat protein) Diet 8 (3410 kcal. M.E./kg., 1 g./kg. ascorbic acid, 15% meat protein)
Total collagen
Collagen X-linking
Insoluble collagen
Body2 weight
(mg./g.)
(%)
(mg./g.)
(g-)
425.0a 453.7a
a
29.1 26.5 a
a
109.6 123.4a
2001 a b 1905 a b
490.6 ab
25.8a
123.7a
1871 a b
539.7b
27.0a
144.4a
1783 a
504.6°
23.9a
117.7a
1905 a b
481.2 ab
26.7 a
120.2a
1855 a
436.5 a
24.0a
103.8a
2064b
431.8a
25.0a
104.1a
1888 ab
'Within each column, means bearing different superscripts are significantly different (P
