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Research Note: Effects of Monensin Feeding and Withdrawal on Fat Pad Adipocyte Size in Female Broilers1
Research Note: Effects of Monensin Feeding and Withdrawal on Fat Pad Adipocyte Size in Female Broilers 1 M. J. METZLER and W. M. BRITTON2 Department of Poultry Science, University of Georgia, Athens, Georgia 30602 (Received for publication May 12, 1987)
1988 Poultry Science 67:339-340 INTRODUCTION
There are three major sites of fat deposition in chickens: muscle, skin, and abdominal fat pad. Changes in fat deposition are associated mainly with the skin and abdominal fat,pad, with muscle fat being relatively constant (Dansky and Hill, 1952; Essary and Dawson, 1965). The abdominal fat pad in broilers usually comprises 2 to 4% of the total body weight and is a major source of variation in the total fat content of a broiler. Body fat is variable in broilers and is dependent on such factors as diet, sex, age, and breed (Edwards et al., 1973; Edwards and Denman, 1975). Monensin is an anticoccidial drug used in poultry rations that is known to cause growth depression when fed to broiler chickens (Jensen and Bartov, 1980). When monensin is withdrawn from the feed, an increase in feed consumption and weight gain occurs (McDougald and McQuistion, 1980). Metzler et al. (1987) found larger abdominal fat pads in unmedicated female broilers than in those medicated with monensin. When medicated broilers were withdrawn from monensin, there was some indication of an increase in fat pad size but it was dependent on time of withdrawal. The study
'Supported by State and Hatch funds allocated to the Georgia Agricultural Experiment Stations of the University of Georgia. 2 To whom correspondence should be addressed.
described here was conducted to determine the effect of monensin feeding and its withdrawal on abdominal fat pad adipocyte size in broiler females. MATERIALS AND METHODS
Samples for abdominal fat pad adipocyte size determination were obtained from two experiments conducted with broiler females (Metzler et al., 1987). Medication was with 120 ppm monensin, Elanco Products Co., Indianapolis, IN. In Experiment 1 treatments were: a) unmedicated controls, b) medicated controls, c) medicated birds with a 5-day withdrawal period; and d) medicated birds with a 10-day withdrawal period. There were six replications with six birds per treatment. Experiment 1 was conducted in wire-floored batteries over a 49-day period. In Experiment 2, treatments were: a) medicated controls, and b) medicated birds with a 7-day withdrawal period. There were nine replications with 20 birds per treatment. Experiment 2 was conducted in floor pens over a 51-day period. Abdominal fat pads were taken at 49 days of age in Experiment 1 and at 44 and 51 days of age in Experiment 2; fat pad samples from two birds per treatment replication group were used for adipocyte sizing. Using a procedure similar to that of Sjostrom et al. (1971), 1-g samples of adipose tissue were obtained from the fat pad and fixed in 20 mL of 10% neutral buffered formalin for several days. Samples were sliced to a thickness of 10 |xm and photomicrographs
339
Downloaded from http://ps.oxfordjournals.org/ at University of Birmingham on June 8, 2015
ABSTRACT Abdominal fat pad adipocyte size was determined in two experiments to evaluate the effect of monensin feeding and withdrawal on female broilers. In Experiment 1 at 49 days of age mean adipocyte sizes were: 49.2 (jun, unmedicated controls; 50.0 p-m, medicated controls; 55.6 ujn, medicated birds with 5-day withdrawal period; and 55.1 p-m medicated birds with 10-day withdrawal period. In Experiment 2, adipocyte sizes of medicated controls were 62.5 and 63.5 jim at 44 and 51 days, respectively. All medicated birds received 120 ppm dietary monensin. In broilers subjected to drug withdrawal for 7 days, adipocyte size was 60.1 u,m at 44 days and 68.8 (xm at 51 days after the drug withdrawal period. There were no significant differences (P<.05) in adipocyte size among treatments in either experiment. (Key words: abdominal fat pad, adipocyte size, monensin, withdrawal period)
340
METZLER AND BRITTON TABLE 1. Adipocyte sizes from abdominal fat pads of cage-reared (Experiment 1) and floor-reared (Experiement 2) broiler females undergoing monensin medication (120 ppm) and withdrawal
Experiment
1
Medication withdrawal (days)
Unmedicated controls
10
(days) 49 44 51
- (Mm) 1 2: 2
49.2 ± 1.7
50.0 ± 1.6 62.5 ± 2.0 63.5 ± 2.2
55.6 ± 1.9
Values within experiments were not significantly different (P<.05). Each value is a mean ± standard error for 12 birds sampled.
3
Each value is a mean ± standard error for 18 birds sampled.
were obtained using a photomicroscope (Carl Zeiss, Inc., Thornwood, NY) with objective magnification 10X, ocular magnification 10X, and camera reduction .25X. The diameter of 50 cells from each sample was determined. All data were analyzed by analysis of variance using Duncan's multiple-range test for mean separation (Steel and Torrie, 1960).
5 or 7 days were similar in adipocyte size and lipid content to broilers medicated throughout. The data suggest that the normal procedure of 5 to 7 days of monensin withdrawal used by the industry would not cause an increase in fat pad lipid content but extension beyond seven days could cause an increase by increasing adipocyte numbers.
RESULTS AND DISCUSSION
REFERENCES
The influence of monensin medication and withdrawal on adipocyte size from the abdominal fat pad of female broilers is presented in Table 1. There were no significant differences (P< .05) in adipocyte size due to monensin treatment or withdrawal in the two experiments. In previous work with the same birds (Metzler et al., 1987), it was shown that unmedicated broilers had larger fat pads, by weight or as a percent of body weight, than medicated (120 ppm monensin) or broilers medicated and withdrawn from medication 5 or 7 days. Unmedicated broilers also had more lipid per fat pad than medicated broilers. When the withdrawal period was extended to 10 days, fat pad weight and fat pad weight as a percent body weight were intermediate and amount of lipid per fat pad was higher than that of other medicated groups. When the adipocyte size data from this study is combined with the data of Metzler et al. (1987) it appears that broilers fed the unmedicated diet had more adipocytes, as the amount of lipid was greater than in medicated broilers but cell sizes were the same. After 10 days of medication withdrawal as lipid was increasing but cell sizes were the same, the number of adipocytes appeared to be increasing when compared with numbers in birds that were medicated. Broilers withdrawn from medication for
Dansky, L. M , and F. W. Hill, 1952. The influence of dietary energy level on the distribution of fat in various tissues of the growing chicken. Poultry Sci. 31:912. (Abstr.) Edwards, H. M., Jr., and F. Denman, 1975. Carcass composition studies. 2. Influences of breed, sex and diet on gross composition of the carcass and fatty acid composition of the adipose tissue. Poultry Sci. 54:1230-1238. Edwards, H. M., Jr., F. Denman, A. A. Ashour and D. Nugara, 1973. Carcass composition studies. 1. Influence of age, sex and type of dietary fat supplementation on total carcass and fatty acid composition. Poultry Sci. 52:934-948. Essary, E. O., and L. E. Dawson, 1965. Quality of fryer carcasses as related to protein and fat levels in the diet. 1. Fat deposition and moisture pick-up during chilling. Poultry Sci. 44:7-15. Jensen, L. S., and I. Bartov, 1980. Effect of dietary ingredients on monensin toxicity in chicks. Poultry Sci. 59:1818-1823. McDougald, L. R., andT. E. McQuistion, 1980. Compensatory growth in broilers after withdrawal of ionophorous anticoccidial drugs. Poultry Sci. 59:1001-1005. Metzler, M. J., W. M. Britton, and L. R. McDougald, 1987. Effects of monensin feeding and withdrawal time on growth and carcass traits in broilers. Poultry Sci. 66:1451-1458. Sjostrom, L, B. Bjomtorp, and J. Vrana, 1971. Microscopic fat cell measurements on frozen-cut adipose tissue in comparison with automatic determinations of osmiumfixed fat cells. J. Lipid Res. 12:521-530. Steel, R.G.D., and J. H. Torrie, 1960. Principles and Procedures of Statistics. McGraw-Hill Book Co., Inc., New York, NY.
Downloaded from http://ps.oxfordjournals.org/ at University of Birmingham on June 8, 2015
1 2
55.1 ± 1., 60.1 : 2.4 68.8: 2.3
1988 Poultry Science 67:339-340 INTRODUCTION
There are three major sites of fat deposition in chickens: muscle, skin, and abdominal fat pad. Changes in fat deposition are associated mainly with the skin and abdominal fat,pad, with muscle fat being relatively constant (Dansky and Hill, 1952; Essary and Dawson, 1965). The abdominal fat pad in broilers usually comprises 2 to 4% of the total body weight and is a major source of variation in the total fat content of a broiler. Body fat is variable in broilers and is dependent on such factors as diet, sex, age, and breed (Edwards et al., 1973; Edwards and Denman, 1975). Monensin is an anticoccidial drug used in poultry rations that is known to cause growth depression when fed to broiler chickens (Jensen and Bartov, 1980). When monensin is withdrawn from the feed, an increase in feed consumption and weight gain occurs (McDougald and McQuistion, 1980). Metzler et al. (1987) found larger abdominal fat pads in unmedicated female broilers than in those medicated with monensin. When medicated broilers were withdrawn from monensin, there was some indication of an increase in fat pad size but it was dependent on time of withdrawal. The study
'Supported by State and Hatch funds allocated to the Georgia Agricultural Experiment Stations of the University of Georgia. 2 To whom correspondence should be addressed.
described here was conducted to determine the effect of monensin feeding and its withdrawal on abdominal fat pad adipocyte size in broiler females. MATERIALS AND METHODS
Samples for abdominal fat pad adipocyte size determination were obtained from two experiments conducted with broiler females (Metzler et al., 1987). Medication was with 120 ppm monensin, Elanco Products Co., Indianapolis, IN. In Experiment 1 treatments were: a) unmedicated controls, b) medicated controls, c) medicated birds with a 5-day withdrawal period; and d) medicated birds with a 10-day withdrawal period. There were six replications with six birds per treatment. Experiment 1 was conducted in wire-floored batteries over a 49-day period. In Experiment 2, treatments were: a) medicated controls, and b) medicated birds with a 7-day withdrawal period. There were nine replications with 20 birds per treatment. Experiment 2 was conducted in floor pens over a 51-day period. Abdominal fat pads were taken at 49 days of age in Experiment 1 and at 44 and 51 days of age in Experiment 2; fat pad samples from two birds per treatment replication group were used for adipocyte sizing. Using a procedure similar to that of Sjostrom et al. (1971), 1-g samples of adipose tissue were obtained from the fat pad and fixed in 20 mL of 10% neutral buffered formalin for several days. Samples were sliced to a thickness of 10 |xm and photomicrographs
339
Downloaded from http://ps.oxfordjournals.org/ at University of Birmingham on June 8, 2015
ABSTRACT Abdominal fat pad adipocyte size was determined in two experiments to evaluate the effect of monensin feeding and withdrawal on female broilers. In Experiment 1 at 49 days of age mean adipocyte sizes were: 49.2 (jun, unmedicated controls; 50.0 p-m, medicated controls; 55.6 ujn, medicated birds with 5-day withdrawal period; and 55.1 p-m medicated birds with 10-day withdrawal period. In Experiment 2, adipocyte sizes of medicated controls were 62.5 and 63.5 jim at 44 and 51 days, respectively. All medicated birds received 120 ppm dietary monensin. In broilers subjected to drug withdrawal for 7 days, adipocyte size was 60.1 u,m at 44 days and 68.8 (xm at 51 days after the drug withdrawal period. There were no significant differences (P<.05) in adipocyte size among treatments in either experiment. (Key words: abdominal fat pad, adipocyte size, monensin, withdrawal period)
340
METZLER AND BRITTON TABLE 1. Adipocyte sizes from abdominal fat pads of cage-reared (Experiment 1) and floor-reared (Experiement 2) broiler females undergoing monensin medication (120 ppm) and withdrawal
Experiment
1
Medication withdrawal (days)
Unmedicated controls
10
(days) 49 44 51
- (Mm) 1 2: 2
49.2 ± 1.7
50.0 ± 1.6 62.5 ± 2.0 63.5 ± 2.2
55.6 ± 1.9
Values within experiments were not significantly different (P<.05). Each value is a mean ± standard error for 12 birds sampled.
3
Each value is a mean ± standard error for 18 birds sampled.
were obtained using a photomicroscope (Carl Zeiss, Inc., Thornwood, NY) with objective magnification 10X, ocular magnification 10X, and camera reduction .25X. The diameter of 50 cells from each sample was determined. All data were analyzed by analysis of variance using Duncan's multiple-range test for mean separation (Steel and Torrie, 1960).
5 or 7 days were similar in adipocyte size and lipid content to broilers medicated throughout. The data suggest that the normal procedure of 5 to 7 days of monensin withdrawal used by the industry would not cause an increase in fat pad lipid content but extension beyond seven days could cause an increase by increasing adipocyte numbers.
RESULTS AND DISCUSSION
REFERENCES
The influence of monensin medication and withdrawal on adipocyte size from the abdominal fat pad of female broilers is presented in Table 1. There were no significant differences (P< .05) in adipocyte size due to monensin treatment or withdrawal in the two experiments. In previous work with the same birds (Metzler et al., 1987), it was shown that unmedicated broilers had larger fat pads, by weight or as a percent of body weight, than medicated (120 ppm monensin) or broilers medicated and withdrawn from medication 5 or 7 days. Unmedicated broilers also had more lipid per fat pad than medicated broilers. When the withdrawal period was extended to 10 days, fat pad weight and fat pad weight as a percent body weight were intermediate and amount of lipid per fat pad was higher than that of other medicated groups. When the adipocyte size data from this study is combined with the data of Metzler et al. (1987) it appears that broilers fed the unmedicated diet had more adipocytes, as the amount of lipid was greater than in medicated broilers but cell sizes were the same. After 10 days of medication withdrawal as lipid was increasing but cell sizes were the same, the number of adipocytes appeared to be increasing when compared with numbers in birds that were medicated. Broilers withdrawn from medication for
Dansky, L. M , and F. W. Hill, 1952. The influence of dietary energy level on the distribution of fat in various tissues of the growing chicken. Poultry Sci. 31:912. (Abstr.) Edwards, H. M., Jr., and F. Denman, 1975. Carcass composition studies. 2. Influences of breed, sex and diet on gross composition of the carcass and fatty acid composition of the adipose tissue. Poultry Sci. 54:1230-1238. Edwards, H. M., Jr., F. Denman, A. A. Ashour and D. Nugara, 1973. Carcass composition studies. 1. Influence of age, sex and type of dietary fat supplementation on total carcass and fatty acid composition. Poultry Sci. 52:934-948. Essary, E. O., and L. E. Dawson, 1965. Quality of fryer carcasses as related to protein and fat levels in the diet. 1. Fat deposition and moisture pick-up during chilling. Poultry Sci. 44:7-15. Jensen, L. S., and I. Bartov, 1980. Effect of dietary ingredients on monensin toxicity in chicks. Poultry Sci. 59:1818-1823. McDougald, L. R., andT. E. McQuistion, 1980. Compensatory growth in broilers after withdrawal of ionophorous anticoccidial drugs. Poultry Sci. 59:1001-1005. Metzler, M. J., W. M. Britton, and L. R. McDougald, 1987. Effects of monensin feeding and withdrawal time on growth and carcass traits in broilers. Poultry Sci. 66:1451-1458. Sjostrom, L, B. Bjomtorp, and J. Vrana, 1971. Microscopic fat cell measurements on frozen-cut adipose tissue in comparison with automatic determinations of osmiumfixed fat cells. J. Lipid Res. 12:521-530. Steel, R.G.D., and J. H. Torrie, 1960. Principles and Procedures of Statistics. McGraw-Hill Book Co., Inc., New York, NY.
Downloaded from http://ps.oxfordjournals.org/ at University of Birmingham on June 8, 2015
1 2
55.1 ± 1., 60.1 : 2.4 68.8: 2.3