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Virginiamycin and Laying Hen Performance1,2
Virginiamycin and Laying Hen Performance1'2 R. D. MILES, D. M. JANKY, and R. H. HARMS Poultry Science Department, University of Florida, Gainesville, Florida 32611 (Received for publication December 6, 1983)
INTRODUCTION
MATERIALS AND METHODS
Virginiamycin is an antibiotic produced by a mutant of Streptomyces virginiae and was isolated by De Somer and Van Dijck (1955). It provides selective activity against Gram-positive bacteria, exerts its action in the intestinal tract, and development of resistance is negligible. Virginiamycin is not active against the enterobacteriaceae and is not involved in resistance transfer among these microorganisms (Pantaleon and Chevrier, 1969). Eyssen and De Somer (1963) and Combs and Bossard (1963) reported that virginiamycin stimulated growth of chicks. March et al. (1978) and Miles et al. (1984) reported that virginiamycin stimulated growth and improved feed efficiency in broilers. Supplementing the diets with virginiamycin resulted in a 7.2% increase in the amount of energy metabolized by the chicks consuming the diets (March et al, 1978). Two experiments were conducted in this study to evaluate the effect of adding virginiamycin to laying hen diets.
Experiment 1. This experiment began in October and was designed to measure the egg production, egg quality, feed efficiency, and pigmentation effect of 10 and 20 ppm of virginiamycin in a layer feed with low pigmentation potential. A randomized block design was used with a total of 240 36-week-old Hyline W-36 layers. Hens were individually caged in an open-type house with four dietary treatments in each of 12 blocks. Each block consisted of four side-by-side pens with five hens each. The experiment was conducted for five 28-day periods. Hens were exposed daily to 15 hr of continuous light. All diets were fed on an ad libitum basis; however, water was furnished to hens by a continual flow-through trough system for 15 min every 2 hr from 0600 to 2000 hr. Hens were weighed at the beginning and end of the experiment. Egg production was recorded daily and summarized weekly. Feed consumption was recorded each 14 days and reported for a 28-day period. Egg weight, specific gravity, albumen height, Haugh units, and yolk pigmentation were measured for all eggs laid on Day 21 of each 28-day period. Four diets were formulated from a cornsoybean meal basal diet (Table 1). Three diets were designed to be of low pigmenting potential and were supplemented with 0, 10, and 20 ppm virginiamycin, respectively (Footnote 1, Table 1).
1 Florida Agricultural Experiment Station Journal Series No. 4952. 2 This investigation was conducted with the support of a grant furnished by the SmithKline Beckman Corporation, Animal Health Products Division, Philadelphia, PA 19101.
139
Downloaded from http://ps.oxfordjournals.org/ at New York University on April 11, 2015
ABSTRACT Two experiments were conducted for five 28-day periods each. In Experiments 1 and 2, Hyline W-36 hens, 36 and 26 weeks of age, respectively, were used. Experiment 1 was designed to measure the effect of virginiamycin on hen performance and egg characteristics when supplementing a diet having low pigmentation potential. In Experiment 2, the diet contained 3% added fat with 0, 10, and 20 ppm virginiamycin. In Experiment 1, virginiamycin-supplemented hens showed increased (P<.05) egg production, body weight, and improved feed efficiency. When egg production and feed efficiency were ranked by quartiles within the control and virginiamycin-supplemented groups, virginiamycin was shown to benefit only the poorer producing hens. In Experiment 2, added fat improved feed efficiency; however, the response to virginiamycin, as observed in Experiment 1, did not occur. (Key words: virginiamycin, laying hen, performance, egg characteristics) 1985 Poultry Science 64:139-143
140
MILES ET AL. TABLE 1. Composition of basal diets used in Experiments 1 and 2 Experiment 2
Ingredient
1
t"' \
Calculated nutrient composition 3 Crude protein, % ME 4 ,kcal/kg Calcium, % Phosphorus, total % SAA 4 , total %
^;0;
70.72 18.99
72.64 17.00
8.09 1.20 .40 .50 .10
7.25 2.00 .43 .50 .13 .05
15.39 2889 3.39 .64 .623
.:.
14.64 2906 3.24 .67 .631
69.15 17.50 3.00 7.25 2.00 .43 .50 .13 .04
14.57 3045 3.24 .67 .626
1
The diets with low pigmenting potential were formulated by replacing 50% yellow corn (w/w) with white corn. The positive control consisted of 100% yellow corn and 0 ppm virginiamycin. 2 For composition of the vitamin-mineral premix see Mileset al. (1981). 3 As-fed diets. "ME = Metabolizable energy; SAA = sulfur amino acids.
Experiment 2. This experiment began in July with 360 26-week-old Hyline W-36 hens. The experimental design was a 2 X 3 factorial that included 0 and 3% added fat and 0, 10, and 20 ppm of virginiamycin. A corn-soybean meal basal diet (Table 1) was used. Each experimental diet was fed to 12 replicate groups of five individually caged hens. Data collection, housing, and management were similar to those in Experiment 1. In both experiments egg yolk pigmentation was evaluated with a Macbeth MC1010S® 3 reflectance colorimeter. A modified computer program of Fry and Damron (1971) was used to convert x, y, and Y readings to dominant wavelength, excitation purity, and luminosity. The data were subjected to analysis of variance and where appropriate, significant differences were determined using multiple range comparisons (Steel and Torrie, 1960).
3 Macbeth®, A division of Kollmorgan Corporation, Little Britain Road, P.O. Box 950, Newburgh, NY 12550.
RESULTS AND DISCUSSION Experiment 1. Supplementation with 10 ppm virginiamycin resulted in increased (P«.05) egg production (Table 2). A doseresponse relationship from 10 to 20 ppm virginiamycin did not occur. Feed efficiency favored virginiamycin (P«.05). Hens fed diets supplemented with virginiamycin gained more weight (P« .05). Hens fed virginiamycin produced smaller eggs. Egg specific gravity was higher (P«.05) for virginiamycin-supplemented hens. No differences in Haugh units or mortality were observed between treatments. Hens fed the adequate pigment diet produced eggs with yolks having a higher (P<.05) dominant wavelength and excitation purity. The increase in excitation purity resulting from virginiamycin supplementation was not significant. Pens within each dietary treatment were ranked by quartile according to egg production and feed efficiency (Table 3). Because there were no differences between the control feeding programs (yellow and white corn) or the virginiamycin feeding programs, the values
Downloaded from http://ps.oxfordjournals.org/ at New York University on April 11, 2015
Corn, ground yellow1 Soybean meal, dehulled (49% protein) Fat (poultry oil) Ground limestone Dicalcium phosphate (22% Ca, 18.5% P) Iodized salt Vitamin premix 2 DL-Methionine (98%) Lysine HC1 (98%)
+ Fat
- Fat
VIRGINIAMYCIN AND LAYER PERFORMANCE
141
TABLE 2. Performance of laying bens and egg characteristics when fed diets with three levels of virginiamycin (Experiment 1) Feeding program Pigment controls Low
Efficacy criteria
Adequate
Virginiamycin lOppm
20ppm
73.97° 95.84* 1.602* 96.9 C 2
73.92b 97.06* 1.594* 98.6 C 1
76.72* 96.66* 1.551 b 152.2* 0
76.18* 94.36* 1.507° 112.8° 0
Egg characteristics Weight, g Specific gravity Albumen height, mm Haugh units
65.79* 1.080* 6.30* 76.29*
65.82* 1.077 b 6.34* 76.65*
63.76° 1.080* 6.28* 76.90*
63.82° 1.081* 6.07* 75.53*
Yolk pigmentation 1 DWL, nm LUM, % EP, %
577.1 b 29.22* 75.07 b
578.7* 27.38° 84.76*
577.1° 29.38* 75.63°
577.1° 29.06* 75.64°
1 DWL = Dominant wavelength, LUM = luminosity, EP = excitation purity. a,b,c Means with different superscripts within a row are significantly different (P*S.05).
represent averages for the control and virginiamycin pens. The quartile egg production averages for virginiamycin hens were found to be more uniform than the quartile averages for control pens. Control hens in the first two quartiles performed as well as the virginiamycin hens. However, a measurable increase (P<.05) in egg production favoring virginiamycin occurred in the third and fourth quartile. These data indicate that virginiamycin improved the performance of the poor producing hens while maintaining the production of the best producers. Perhaps virginiamycin is suppressing an
organism to which these hens are susceptible. Ranking by quartile according to feed efficiency indicated that virginiamycin hens performed better than the control hens in all four quartiles. Improved feed efficiency (P«.05), which favored virginiamycin, was observed in the bottom two quartiles. To be able to show a better feed efficiency associated with greater production is even more important than showing better efficiency with equal production or equal efficiency with better production. Experiment 2. There was no difference in egg production among dietary treatments (Table 4). Hens fed 20 ppm virginiamycin in
TABLE 3. Pen performance of hens by quartile when ranked by egg production and feed efficiency (Experiment 1) Production ranked
Feed efficiency ranked
Ranked quartiles
Control
Virginiamycin
Control
Virginiamycin
First Second Third Fourth
78.04* 75.38* 72.65* 69.71*
76.83* 76.79* 76.69° 75.49°
1.495* 1.552* 1.604* 1.742*
1.479* 1.520* 1.537 b 1.579°
a
' Means with different superscripts within a row are significantly different (P<.05).
1
DWL = Dominant wavelength, LUM = luminosity, EP = excitation purity.
Downloaded from http://ps.oxfordjournals.org/ at New York University on April 11, 2015
Egg production, hen-day, % Feed consumption, g/bird/day Feed efficiency, kg feed/doz Body weight gain, g Mortality, total no. dead
1494* 5 1517* 3
578.7b 25.76* 85.33*
59.39b 1.083*
77.87* 88.19* 3.040*
10
0% Fat
1
DWL = Dominant wavelength, LUM = luminosity, EP = excitation purity.
a,b,c Means with different superscripts within a row are significantly different (P<.05).
Hen weight, g Mortality, hens lost
578.7b 25.78* 85.32*
60.97* 1.083*
Egg quality Weight Specific gravity
Yolk pigmentation 1 DWL, nm LUM, % EP, %
81.20* 88.94* 3.015*
Production, egg/hen/day Feed consumption, g/bird/day Feed efficiency, feed/doz eggs
0
1554* 6
578.6b 25.95* 86.21*
59.37b 1.083*
78.54* 87.48 b 3.079*
20
152
57 2 8
6
7 8
TABLE 4. Performance of laying hens and egg characteristics when fed diets containin with three levels ofvirginiamycin (Experiment 2)
d from http://ps.oxfordjournals.org/ at New York University on April 11, 2015
VIRGINIAMYCIN AND LAYER PERFORMANCE
Virginiamycin failed to show t h e benefits observed in t h e first e x p e r i m e n t . T h e explanation for this is n o t clear; however, t h e age of t h e bird and season of t h e year were different. Also, in t h e second e x p e r i m e n t t h e hens were laying at a higher rate. T h e egg p r o d u c t i o n quartile comparison in E x p e r i m e n t 1 m a y help t o explain w h y t h e r e was n o measurable virginiamycin effect. A decrease in egg weight was observed in b o t h e x p e r i m e n t s , indicating t h a t smaller eggs was n o t a p h e n o m e n o n associated with season. Because o p t i m u m egg size is of current interest, this finding m a y be associated with potential benefits.
REFERENCES Combs, G. F., and E. H. Bossard, 1963. Comparison of growth response of chicks to virginiamycin and other antibiotics. Poultry Sci. 42:681-685. De Somer, P., and P. Van Dijck, 1955. A preliminary report on antibiotic number 899. Antibiot. Chemother. 5:632-639. Eyssen, H., and P. De Somer, 1963. The mode of action of antibiotics in stimulating growth of chicks. J. Exp. Med. 117:127-138. Fry, J. L., and B. L. Damron, 1971. Computer calculation of poultry and egg pigmentation data. Food Technol. 2 5 : 4 4 - 4 5 . March, B. E., R. Soong, and C. MacMillan, 1978. Growth rate, feed conversion and dietary metabolizable energy in response to virginiamycin supplementation of different diets. Poultry Sci. 57:1346-1350. Miles, R. D., A. S. Arafa, R. H. Harms, C. W. Carlson, B. L. Reid, and J. S. Crawford, 1981. Effects of a living nonfreeze-dried Lactobacillus acidophilus culture on performance, egg quality, and gut microflora in commercial layers. Poultry Sci. 60: 993-1004. Miles, R. D., D. M. Janky, and R. H. Harms, 1984. Virginiamycin and broiler performance. Poultry Sci. 63:1218-1221. Pantaleon, J., and L. Chevrier, 1969. L'utilisation des antibiotiques en therapeutique et nutrition envisaged sous Tangle de l'hygiene publique. Can. Med. Vet. 38:271-277. Steel, R.G.D., and J. H. Torrie, 1960. Principles and Procedures of Statistics. McGraw Hill Book Co., New York, NY.
Downloaded from http://ps.oxfordjournals.org/ at New York University on April 11, 2015
t h e 0 a n d 3% added fat t r e a t m e n t s h a d reduced ( P < . 0 5 ) feed c o n s u m p t i o n c o m p a r e d t o t h e 0 and 10 p p m virginiamycin. In diets with 0 and 3% added fat, virginiamycin s u p p l e m e n t a t i o n resulted in reduced egg weight. Hens fed t h e diet with added fat had lower feed c o n s u m p t i o n and improved feed efficiency. Virginiamycin did n o t statistically improve feed efficiency in this diet. Virginiamycin had n o influence on y o l k p i g m e n t a t i o n . Virginiamycin resulted in heavier h e n s ; however, t h e comparisons were n o t statistically significant. Mortality was n o t related t o dietary treatment.
143
INTRODUCTION
MATERIALS AND METHODS
Virginiamycin is an antibiotic produced by a mutant of Streptomyces virginiae and was isolated by De Somer and Van Dijck (1955). It provides selective activity against Gram-positive bacteria, exerts its action in the intestinal tract, and development of resistance is negligible. Virginiamycin is not active against the enterobacteriaceae and is not involved in resistance transfer among these microorganisms (Pantaleon and Chevrier, 1969). Eyssen and De Somer (1963) and Combs and Bossard (1963) reported that virginiamycin stimulated growth of chicks. March et al. (1978) and Miles et al. (1984) reported that virginiamycin stimulated growth and improved feed efficiency in broilers. Supplementing the diets with virginiamycin resulted in a 7.2% increase in the amount of energy metabolized by the chicks consuming the diets (March et al, 1978). Two experiments were conducted in this study to evaluate the effect of adding virginiamycin to laying hen diets.
Experiment 1. This experiment began in October and was designed to measure the egg production, egg quality, feed efficiency, and pigmentation effect of 10 and 20 ppm of virginiamycin in a layer feed with low pigmentation potential. A randomized block design was used with a total of 240 36-week-old Hyline W-36 layers. Hens were individually caged in an open-type house with four dietary treatments in each of 12 blocks. Each block consisted of four side-by-side pens with five hens each. The experiment was conducted for five 28-day periods. Hens were exposed daily to 15 hr of continuous light. All diets were fed on an ad libitum basis; however, water was furnished to hens by a continual flow-through trough system for 15 min every 2 hr from 0600 to 2000 hr. Hens were weighed at the beginning and end of the experiment. Egg production was recorded daily and summarized weekly. Feed consumption was recorded each 14 days and reported for a 28-day period. Egg weight, specific gravity, albumen height, Haugh units, and yolk pigmentation were measured for all eggs laid on Day 21 of each 28-day period. Four diets were formulated from a cornsoybean meal basal diet (Table 1). Three diets were designed to be of low pigmenting potential and were supplemented with 0, 10, and 20 ppm virginiamycin, respectively (Footnote 1, Table 1).
1 Florida Agricultural Experiment Station Journal Series No. 4952. 2 This investigation was conducted with the support of a grant furnished by the SmithKline Beckman Corporation, Animal Health Products Division, Philadelphia, PA 19101.
139
Downloaded from http://ps.oxfordjournals.org/ at New York University on April 11, 2015
ABSTRACT Two experiments were conducted for five 28-day periods each. In Experiments 1 and 2, Hyline W-36 hens, 36 and 26 weeks of age, respectively, were used. Experiment 1 was designed to measure the effect of virginiamycin on hen performance and egg characteristics when supplementing a diet having low pigmentation potential. In Experiment 2, the diet contained 3% added fat with 0, 10, and 20 ppm virginiamycin. In Experiment 1, virginiamycin-supplemented hens showed increased (P<.05) egg production, body weight, and improved feed efficiency. When egg production and feed efficiency were ranked by quartiles within the control and virginiamycin-supplemented groups, virginiamycin was shown to benefit only the poorer producing hens. In Experiment 2, added fat improved feed efficiency; however, the response to virginiamycin, as observed in Experiment 1, did not occur. (Key words: virginiamycin, laying hen, performance, egg characteristics) 1985 Poultry Science 64:139-143
140
MILES ET AL. TABLE 1. Composition of basal diets used in Experiments 1 and 2 Experiment 2
Ingredient
1
t"' \
Calculated nutrient composition 3 Crude protein, % ME 4 ,kcal/kg Calcium, % Phosphorus, total % SAA 4 , total %
^;0;
70.72 18.99
72.64 17.00
8.09 1.20 .40 .50 .10
7.25 2.00 .43 .50 .13 .05
15.39 2889 3.39 .64 .623
.:.
14.64 2906 3.24 .67 .631
69.15 17.50 3.00 7.25 2.00 .43 .50 .13 .04
14.57 3045 3.24 .67 .626
1
The diets with low pigmenting potential were formulated by replacing 50% yellow corn (w/w) with white corn. The positive control consisted of 100% yellow corn and 0 ppm virginiamycin. 2 For composition of the vitamin-mineral premix see Mileset al. (1981). 3 As-fed diets. "ME = Metabolizable energy; SAA = sulfur amino acids.
Experiment 2. This experiment began in July with 360 26-week-old Hyline W-36 hens. The experimental design was a 2 X 3 factorial that included 0 and 3% added fat and 0, 10, and 20 ppm of virginiamycin. A corn-soybean meal basal diet (Table 1) was used. Each experimental diet was fed to 12 replicate groups of five individually caged hens. Data collection, housing, and management were similar to those in Experiment 1. In both experiments egg yolk pigmentation was evaluated with a Macbeth MC1010S® 3 reflectance colorimeter. A modified computer program of Fry and Damron (1971) was used to convert x, y, and Y readings to dominant wavelength, excitation purity, and luminosity. The data were subjected to analysis of variance and where appropriate, significant differences were determined using multiple range comparisons (Steel and Torrie, 1960).
3 Macbeth®, A division of Kollmorgan Corporation, Little Britain Road, P.O. Box 950, Newburgh, NY 12550.
RESULTS AND DISCUSSION Experiment 1. Supplementation with 10 ppm virginiamycin resulted in increased (P«.05) egg production (Table 2). A doseresponse relationship from 10 to 20 ppm virginiamycin did not occur. Feed efficiency favored virginiamycin (P«.05). Hens fed diets supplemented with virginiamycin gained more weight (P« .05). Hens fed virginiamycin produced smaller eggs. Egg specific gravity was higher (P«.05) for virginiamycin-supplemented hens. No differences in Haugh units or mortality were observed between treatments. Hens fed the adequate pigment diet produced eggs with yolks having a higher (P<.05) dominant wavelength and excitation purity. The increase in excitation purity resulting from virginiamycin supplementation was not significant. Pens within each dietary treatment were ranked by quartile according to egg production and feed efficiency (Table 3). Because there were no differences between the control feeding programs (yellow and white corn) or the virginiamycin feeding programs, the values
Downloaded from http://ps.oxfordjournals.org/ at New York University on April 11, 2015
Corn, ground yellow1 Soybean meal, dehulled (49% protein) Fat (poultry oil) Ground limestone Dicalcium phosphate (22% Ca, 18.5% P) Iodized salt Vitamin premix 2 DL-Methionine (98%) Lysine HC1 (98%)
+ Fat
- Fat
VIRGINIAMYCIN AND LAYER PERFORMANCE
141
TABLE 2. Performance of laying bens and egg characteristics when fed diets with three levels of virginiamycin (Experiment 1) Feeding program Pigment controls Low
Efficacy criteria
Adequate
Virginiamycin lOppm
20ppm
73.97° 95.84* 1.602* 96.9 C 2
73.92b 97.06* 1.594* 98.6 C 1
76.72* 96.66* 1.551 b 152.2* 0
76.18* 94.36* 1.507° 112.8° 0
Egg characteristics Weight, g Specific gravity Albumen height, mm Haugh units
65.79* 1.080* 6.30* 76.29*
65.82* 1.077 b 6.34* 76.65*
63.76° 1.080* 6.28* 76.90*
63.82° 1.081* 6.07* 75.53*
Yolk pigmentation 1 DWL, nm LUM, % EP, %
577.1 b 29.22* 75.07 b
578.7* 27.38° 84.76*
577.1° 29.38* 75.63°
577.1° 29.06* 75.64°
1 DWL = Dominant wavelength, LUM = luminosity, EP = excitation purity. a,b,c Means with different superscripts within a row are significantly different (P*S.05).
represent averages for the control and virginiamycin pens. The quartile egg production averages for virginiamycin hens were found to be more uniform than the quartile averages for control pens. Control hens in the first two quartiles performed as well as the virginiamycin hens. However, a measurable increase (P<.05) in egg production favoring virginiamycin occurred in the third and fourth quartile. These data indicate that virginiamycin improved the performance of the poor producing hens while maintaining the production of the best producers. Perhaps virginiamycin is suppressing an
organism to which these hens are susceptible. Ranking by quartile according to feed efficiency indicated that virginiamycin hens performed better than the control hens in all four quartiles. Improved feed efficiency (P«.05), which favored virginiamycin, was observed in the bottom two quartiles. To be able to show a better feed efficiency associated with greater production is even more important than showing better efficiency with equal production or equal efficiency with better production. Experiment 2. There was no difference in egg production among dietary treatments (Table 4). Hens fed 20 ppm virginiamycin in
TABLE 3. Pen performance of hens by quartile when ranked by egg production and feed efficiency (Experiment 1) Production ranked
Feed efficiency ranked
Ranked quartiles
Control
Virginiamycin
Control
Virginiamycin
First Second Third Fourth
78.04* 75.38* 72.65* 69.71*
76.83* 76.79* 76.69° 75.49°
1.495* 1.552* 1.604* 1.742*
1.479* 1.520* 1.537 b 1.579°
a
' Means with different superscripts within a row are significantly different (P<.05).
1
DWL = Dominant wavelength, LUM = luminosity, EP = excitation purity.
Downloaded from http://ps.oxfordjournals.org/ at New York University on April 11, 2015
Egg production, hen-day, % Feed consumption, g/bird/day Feed efficiency, kg feed/doz Body weight gain, g Mortality, total no. dead
1494* 5 1517* 3
578.7b 25.76* 85.33*
59.39b 1.083*
77.87* 88.19* 3.040*
10
0% Fat
1
DWL = Dominant wavelength, LUM = luminosity, EP = excitation purity.
a,b,c Means with different superscripts within a row are significantly different (P<.05).
Hen weight, g Mortality, hens lost
578.7b 25.78* 85.32*
60.97* 1.083*
Egg quality Weight Specific gravity
Yolk pigmentation 1 DWL, nm LUM, % EP, %
81.20* 88.94* 3.015*
Production, egg/hen/day Feed consumption, g/bird/day Feed efficiency, feed/doz eggs
0
1554* 6
578.6b 25.95* 86.21*
59.37b 1.083*
78.54* 87.48 b 3.079*
20
152
57 2 8
6
7 8
TABLE 4. Performance of laying hens and egg characteristics when fed diets containin with three levels ofvirginiamycin (Experiment 2)
d from http://ps.oxfordjournals.org/ at New York University on April 11, 2015
VIRGINIAMYCIN AND LAYER PERFORMANCE
Virginiamycin failed to show t h e benefits observed in t h e first e x p e r i m e n t . T h e explanation for this is n o t clear; however, t h e age of t h e bird and season of t h e year were different. Also, in t h e second e x p e r i m e n t t h e hens were laying at a higher rate. T h e egg p r o d u c t i o n quartile comparison in E x p e r i m e n t 1 m a y help t o explain w h y t h e r e was n o measurable virginiamycin effect. A decrease in egg weight was observed in b o t h e x p e r i m e n t s , indicating t h a t smaller eggs was n o t a p h e n o m e n o n associated with season. Because o p t i m u m egg size is of current interest, this finding m a y be associated with potential benefits.
REFERENCES Combs, G. F., and E. H. Bossard, 1963. Comparison of growth response of chicks to virginiamycin and other antibiotics. Poultry Sci. 42:681-685. De Somer, P., and P. Van Dijck, 1955. A preliminary report on antibiotic number 899. Antibiot. Chemother. 5:632-639. Eyssen, H., and P. De Somer, 1963. The mode of action of antibiotics in stimulating growth of chicks. J. Exp. Med. 117:127-138. Fry, J. L., and B. L. Damron, 1971. Computer calculation of poultry and egg pigmentation data. Food Technol. 2 5 : 4 4 - 4 5 . March, B. E., R. Soong, and C. MacMillan, 1978. Growth rate, feed conversion and dietary metabolizable energy in response to virginiamycin supplementation of different diets. Poultry Sci. 57:1346-1350. Miles, R. D., A. S. Arafa, R. H. Harms, C. W. Carlson, B. L. Reid, and J. S. Crawford, 1981. Effects of a living nonfreeze-dried Lactobacillus acidophilus culture on performance, egg quality, and gut microflora in commercial layers. Poultry Sci. 60: 993-1004. Miles, R. D., D. M. Janky, and R. H. Harms, 1984. Virginiamycin and broiler performance. Poultry Sci. 63:1218-1221. Pantaleon, J., and L. Chevrier, 1969. L'utilisation des antibiotiques en therapeutique et nutrition envisaged sous Tangle de l'hygiene publique. Can. Med. Vet. 38:271-277. Steel, R.G.D., and J. H. Torrie, 1960. Principles and Procedures of Statistics. McGraw Hill Book Co., New York, NY.
Downloaded from http://ps.oxfordjournals.org/ at New York University on April 11, 2015
t h e 0 a n d 3% added fat t r e a t m e n t s h a d reduced ( P < . 0 5 ) feed c o n s u m p t i o n c o m p a r e d t o t h e 0 and 10 p p m virginiamycin. In diets with 0 and 3% added fat, virginiamycin s u p p l e m e n t a t i o n resulted in reduced egg weight. Hens fed t h e diet with added fat had lower feed c o n s u m p t i o n and improved feed efficiency. Virginiamycin did n o t statistically improve feed efficiency in this diet. Virginiamycin had n o influence on y o l k p i g m e n t a t i o n . Virginiamycin resulted in heavier h e n s ; however, t h e comparisons were n o t statistically significant. Mortality was n o t related t o dietary treatment.
143