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Converting Male Broilers to Periodic Feeders: Effects on Food Intake, Growth and Body Composition1,2,3,4
C o n v e r t i n g Male Broilers t o Periodic F e e d e r s : Effects o n F o o d I n t a k e , Growth and Body Composition1 >2-3'4 BONITA E. CONARD and WAYNE J. KUENZEL Department of Poultry Science, University of Maryland, College Park, Maryland 20742 (Received for publication September 1, 1977)
INTRODUCTION
Gallus domesticus fowl are "nibblers", consuming food throughout the day. The data of Masic et al. (1974) clearly show that broilers on a 14-hr photoperiod feed each hr throughout the light period with greater feed consumption during the beginning and end of the photoperiod. Some laboratory mammals are likewise "nibblers" by nature and recent studies using growing rats have suggested that converting them to "meal-eaters" (periodic feeders) resulted in equivalent weight gain but greater feed efficiency (Cohn and Joseph, 1960; Leveille and Hanson, 1965). The pattern of food intake throughout the day and its manipulation may be important factors when considering techniques to improve growth rate and lower feed conversion in rapidly growing animals. The purpose of this study was to convert broiler chicks to periodic feeders to determine whether this behavioral manipulation might be
'Scientific Article No. A2356, Contribution No. 5366 of the Maryland Agricultural Experiment Station (Department of Poultry Science). 2 Submitted by B. E. C. in partial fulfillment of M.S. degree, University of Maryland. 3 This study was presented at the 66th Annual Meeting of the Poultry Science Association, Inc., Auburn, Alabama, 1977. 4 Send reprint requests to W. J. Kuenzel. 1978 Poultry Sci 57:719-725
useful in augmenting growth rate and lowering feed conversion in growing broilers. MATERIALS AND METHODS
Animals. Arbor' Acre male chicks (White Rock) were used in all experiments. Photoperiod. Broiler chicks were exposed either to continuous light or to photoperiods of LD14:10or 16:8. Feed and Housing. Chicks were fed a commercial broiler crumble diet calculated to contain 22 percent protein and 3234 kcal/kg metabolizable energy (ME) for Experiments 1 through 3. In Experiment 4 a diet was formulated to contain a slightly higher energy content (3454 kcal/kg ME, 23 percent protein). All chicks were housed in Petersime batteries with raised wire floors. In Experiment 4 chicks were moved to grow-out batteries by week 4 and were raised to 7 weeks of age, at which time broilers reached market weight of 2 kg. Meal-feeding Procedure. Chicks in all studies had food and water available ad lib. throughout the first week. Meal-feeding schedules were initiated at the start of week two. Chicks were allowed unlimited access to an unrestricted amount of feed during equally spaced 2 hr or l'/2 hr feeding periods (meals). Feed consumption was determined at the completion of each meal. Feeders were removed from pens throughout the day to ensure that no feeding occurred between feeding periods. All control
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ABSTRACT Broilers, Gallus domesticus, were converted to "meal-eaters" (periodic feeders), and food intake, growth, and body composition were evaluated. A meal was defined as unlimited access to an unrestricted amount of feed for a 2- or 1 1/2-hr feeding period. Employing a standard broiler starter ration, (3234 kcal/kg metabolizable energy (ME)), 1, 2, and 3 meals per day were found inadequate to support optimal growth and feed conversion. No significant differences were found in body weight, feed conversion or body composition between a 4-meal treatment group and controls fed ad lib. When a high energy ration (3454 kcal/kg ME) was fed to the following treatment groups: 3, 4, 5 meal, and ad lib. controls, the 5-meal group displayed a significantly greater rate of growth and a lower feed conversion. No significant differences were found in body composition or digestive tract measurements among any of the treatment groups. It is suggested that periodic feeding may be a possible technique for use by the broiler industry to further improve growth rate and feed conversion of broilers.
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FIG. 1. Feeding schedules for "meal-eating" treatment groups in Experiments 2, 3, and 4. The photoperiod for Experiments 2 and 3 was LD14:10. The photoperiod for Experiment 4 was LD16:8.
feeding on mean body weight, rate of body weight gain, and mean feed conversion (Snedecor and Cochran, 1967). Experimental Protocol. In Experiment 1 two groups of chicks were raised separately, fed ad lib, and exposed to continuous light or a photoperiod of LD14:10. Each treatment had 6 replications with 8 chicks per replication. In Experiment 2 chicks were assigned to one of three treatments: 1 meal, 3 meals, or ad lib. feeding. Each treatment had 8 replications (pens) with 8 chicks/pen and chicks were raised to 4 weeks of age. Time when meals were administered are shown in Figure 1. Chicks in Experiment 3 were assigned to one of four treatments: 2, 3, 4 meals, or ad lib. feeding. Each treatment had 4 replications with 7 chicks/pen and chicks were raised to 7 weeks of age. A high-energy diet of 3454 kcal/kg ME was fed throughout the study. Time periods throughout the day when meals were administered are shown in Figure 1.
RESULTS Experiment 1. Continuous Light Versus LD14:10. No significant differences were detected in body weight, total feed consumption, feed conversion, or body composition. Since broilers grown under LD14:10 performed comparably to those raised in continuous light, employing a photoperiod in future studies was justified due to the savings in electrical energy (amounting to 8 to 10 less hours of light per day). Use of a photoperiod also has a potential advantage of entraining endogenous rhythms in birds (Bunning, 1967). Experiment 2. 1 Meal, 3 Meals Versus Ad lib. Feeding. Data are shown in Tables 1 and 2. The 1-meal treatment showed a significant depression in body weight (P<.05), food intake (P<.05), and body fat content (P<.05) and a significant increase in percent moisture (P<.05). No significant differences were detected in body weight or body composition between the 3-meal and ad lib. treatments except percent body fat was lower in the 3-meal group (P<.05). Body weight of the 3-meal treatment group was consistently lower throughout the study. Data obtained for total feed consumption for the experiment showed the 1-meal treatment group consumed approximately 62% less feed than the ad lib. birds. The great distension of the crop at the end of the single meal per day suggested that a physical
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groups had food available ad lib. Body weight was measured at weekly intervals and total food intake calculated/week in order to compute feed conversion/week for all studies. Body Composition Procedure. Birds were sacrificed by cervical dislocation, placed in plastic bags, and frozen. Each frozen bird was cut using a band saw, ground in a Hobart grinder, packed into a plastic bag, and refrozen. Percent fat, moisture, and ash were determined by standard laboratory procedures (AOAC, 1975). Dried fat-free weight (DFFW, ash-free) was determined by difference and is a value very close to the true protein content of carcasses (Donaldson et ai, 1956). Statistical Methods. On the seventh day of each study, chicks were weighed, ranked, and blocked according to body weight. Each treatment group of Experiments 3 and 4 contained 4 blocks and each of the 4 blocks within all treatments had chicks of equivalent body weight. Body weight, feed conversion, body composition, and digestive tract data were analyzed statistically by two-way analysis of variance. Student-Newman-Keuls' multiplerange (SNK) test was used to separate means at the 5% level of significance (Sokal and Rohlf, 1969). Covariance analysis was employed for Experiment 4 to determine the effect of meal-
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TABLE l.—Body weight, food intake, and feed conversion of broilers fed ad libitum or meal-fed starter rations3-
Treatment
Body weight15 (g)
Experiment 2 1 - Meal 3 -Meal Ad libitum
295.1° 573. l c 626.7C
366.5d 805.9C 958.5C
1.63c 1.91c 1.85c
Experiment 3 2 - Meal 3 - Meal 4 - Meal Ad libitum
485.8e 558.9d 607.3 e 612.9C
538.3e 639.2 d 722.0C 73 5.6C
1.56d 1.77c 1.81c 1.82c
Experiment 4 3 - Meal 4 — Meal 5 - Meal Ad libitum
1835. l d 1917.0 cd 2003.3C 1903.6 cd
3507.2d 3644.5d 3816.4C 3727.6C
2.02c 1.97C 1.96c 2.16c
Total food intake/chick (g)
Feed conversion
Age of chicks at termination of study: Experiments 2 and 3, 4 weeks of age; Experiment 4, 7 weeks of age.
limitation of the digestive tract prevented adequate intake of nutrients. In addition, the very low food consumption of the 1-meal treatment group accounted for the significantly lower fat content and higher moisture content of their carcasses (Table 2). Experiment 3. 2, 3, 4 Meals Versus Ad lib. Feeding. Data are shown in Tables 1 and 2. The 2-meal treatment group had significantly lower body weight (P<.05) compared with the other treatments. By week 4, the mean body weight and percent of body fat of the 3-meal treatment group were significantly lower (P<.05) than those of the 4-meal and ad lib. treatment groups. Data of total feed intake showed that the 2-meal and 3-meal birds consumed approximately 27% and 13% less feed, respectively, than ad lib. controls. Experiment 4. High Energy Ration; Meal-fed Versus Ad lib. Feeding. Weekly body weight data are found in Table 3. Note that all treatment groups began the experiment with equal body weights and that controls fed ad lib. showed the greatest body weight gains through week 3. The 5-meal groups then surpassed controls and continued to show greater body weight gains through week 7. Total food intake for the 7-week period and final body weight and body composition data are shown in Tables
1 and 2. No significant differences were found in body weight, feed conversion, or body composition, using ANOVA and the SNK multiple-range test. Significant differences were found in food intake, with both the 5-meal and ad lib. groups consuming more food over the total 7-week study than the 4- and 3-meal groups. Data on body weight and feed conversion for each week of the 7-week study were next subjected to covariance analysis. Covariance analysis was used to determine if any significant differences existed among treatments in the rate of body weight gain and rate of change in feed conversion. In addition, mean body weight and feed conversion were analyzed for the entire study (determined by averaging weekly values from 2 through 7 weeks). Average weight and rate of gain for each treatment group are shown in Table 3. Based upon this analysis, the 5-meal birds showed a greater mean body weight compared to other treatments, yet total feed consumption was not significantly different between the 5-meal broilers and controls fed ad lib. The 5-meal group also displayed a significantly greater rate of gain (P<.05). No significant differences were detected in feed conversion among all treatments. The 5-meal broilers, however, showed a lower feed conversion and lower rate of increase in
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Photoperiod used: Experiments 2 and 3, LD 14.10; Experiment 4, LD 16:8. ME of diet: Experiments 2 and 3, 3234 kcal/kg; Experiment 4, 3454 kcal/kg. Within each column of each experiment, means with at least one like superscript are not significantly different (P<.05).
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DISCUSSION Importance of High Energy Ration for Meal-fed Broiler Chicks. Defining a meal as unlimited access to an unrestricted amount of feed during a VA- or 2-hr time period, 1 to 5 meals per day were fed to rapidly growing broiler chicks. Feeding 1 to 3 meals per day was found inadequate to support optimal growth in
broilers. Feeding 4 meals per day was found equivalent but not superior to ad lib. feeding when a standard broiler starter ration (3234 kcal/kg ME, 22% protein) was fed. When a high energy broiler ration (3454 kcal/kg ME, 23% protein) was used, a treatment of 5 meals per day was found superior to ad lib. feeding. Covariance analysis showed that the rate of body weight was significantly greater in the 5-meal group compared to ad lib. controls. Wagstaff (1976) has reported greater body weight gain and lower feed conversion in broilers subjected to controlled feeding and has stressed that high energy diets are essential for success of controlled feeding programs. Our data support his findings that high energy diets are important in controlled feeding of broilers. In addition, body composition analysis of meal-fed birds vs. birds fed ad lib. showed no significant differences in any component analyzed (Table 2). This finding is of importance since in mammalian studies rats converted to "meal-eaters" showed a signficantly higher percent body fat (Cohn and Joseph, 1960). The 5-meal broilers did not show a greater percent body fat compared to controls fed ad lib. (Table 2). Hence, the quality of the carcass does not appear to be adversely affected by the
TABLE 2.—Body composition of broilers fed ad libitum or meal-fed starter rations^
Percent moisture
Percent fat
Percent DFFWC (ash-free)
Percent ash
Experiment 2 1 - Meal 3 - Meal Ad libitum
69.26 d 66.22e 65.59 e
6.02 f 8.87 e 10.25 d
21.60 d 21.89 d 21.42 d
3.36 d 3.01 d 2.74 d
Experiment 3 2 - Meal 3 - Meal 4 — Meal Ad libitum
67.34 d 64.73 d 65.54 d
8.6 5 e 10.50 d 10.88 d
21.42 d 21.94 d 20.6 5 d
2.68 d 2.96 d 3.01 d
Experiment 4 3 - Meal 4 — Meal 5 - Meal Ad libitum
60.70 d 62.51 d 62.70 d 60.82 d
15.10 d 13.73 d 14.09 d 15.31 d
21.43 d 20.83 d 20.3 2 d 21.05 d
2.74 d 2.93 d 2.90 d 2.82 d
Treatment
15
Photoperiod used: Experiments 2 and 3, LD 14:10; Experiment 4, LD 16:8. ME of diet: Experiments 2 and 3, 3234 kcal/kg; Experiment 4, 3454 kcal/kg. Within each column of each experiment, means with at least one like superscript are not significantly different (P<.05). Age of chicks at termination of study: Experiments 2 and 3, 4 weeks of age; Experiment 4, 7 weeks of age. DFFW = dry faHree weight. DFFW (ash-free) is a close estimate of the true protein content of the carcass.
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feed conversion points for the study. Weights and linear measurements of digestive tracts and 15 digestive tract indexes from birds in Experiment 4 were subjected to statistical analysis. No significant differences were found among treatments. Pattern of Food Intake Per Day. The quantity of food consumed during each meal per treatment was computed for Experiments 2 through 4. Mean food intake per bird per meal was then determined on a weekly basis and graphed. Results of Experiment 4 are shown in Figure 2. The largest meal consumed per day was consistently the last meal before initiation of the dark period. This generalization was true for all experiments and did not shift during the development and growth of chicks from 2 through 7 weeks of age.
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TABLE 3.—Weekly body weights and rate of body weight gain of chicks in Experiment 4 Week
Treatment
Body wt (g) a
Part A. Weekly body weights 108.8 108.7 108.7 108.7
4.34 4.24 4.25 4.21
3 - Meal 4 — Meal 5 - Meal Ad libitum
273.0 279.8 290.4 295.4
12.34 7.3 5 7.89 9.80
3 - Meal 4 — Meal 5 -Meal Ad libitum
507.9 519.8 546.9 557.8
17.79 11.96 9.87 17.76
34 5Ad
Meal Meal Meal libitum
798.2 821.2 861.2 855.0
20.82 16.89 16.72 25.80
3 - Meal 4 — Meal 5 -Meal Ad libitum
1139.8 1221.6 1245.1 1209.2
21.64 23.27 21.13 41.89
3 - Meal 4 — Meal 5 - Meal Ad libitum
1475.4 1540.3 1608.0 1568.6
25.95 11.26 24.56 47.57
3 - Meal 4 — Meal 5 - Meal Ad libitum
1835.1 1917.0 2003.3 1903.6
22.04 17.48 33.84 46.96
Grand average body wt (g) b
Rate of gain (g/week)
1005.led 1050.2 f 1092.7 f 1065.l f
315.7 e 332.7 e 346.5 f 3 26.4 e
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Treatment
3 - Meal 4 — Meal 5 - Meal Ad libitum
Part B. Rate of body weight gain c 3 - Meal 4 — Meal 5 - Meal Ad libitum
.99 .99 .99 .99
Mean + SEM. Grand average 7-week body weight for each treatment computed by averaging weekly body weights from 2 through 7 weeks. Covariance analysis used to determine differences in rate of gain in body weight. Within each column, means bearing like superscripts are not significantly different (P<.05).
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FIG. 2. Pattern of food intake of broilers in Experiment 4. Lower case letters indicate meals or time intervals when feed was available to chicks. 3-Meal: a = 7:00-8:30 AM; b = 2:15-3:45 PM; c 9:30-1100 PM; 4-Meal: a = 7:00-8:30 AM; b = 12:00-1:30 PM; C = 4 : 3 0 - 6 : 0 0 PM; d = 9:30-11:00 PM; 5-Meal: a = 7:00-8:30 AM; b = 10:45-12:15 PM; C = 2:15-3:45 PM; d = 5:45-7:15 PM; e = 9:30-11:00 PM.
significantly faster rate of growth in meal-fed broilers. It should be n o t e d , however, t h a t this study included males only. F u t u r e e x p e r i m e n t s should be performed using females to determine if they respond similarly to periodic feeding. Pattern of Food Intake Per Day. In Experim e n t s 2 through 4, involving feeding 2 t o 5 meals per day, t h e largest meal consumed by broilers was consistently t h e last one before t h e start of t h e d a r k period ( E x p e r i m e n t 4 , Fig. 2). These results were o b t a i n e d using either a p h o t o p e riod of L D 1 4 : 1 0 or 1 6 : 8 . Similar feeding patterns were o b t a i n e d by Savory ( 1 9 7 6 ) w h o allowed chicks free access to feed over 12 hr p h o t o p e r i o d s with and w i t h o u t simulated d a w n and dusk periods. All chicks subjected to
In addition, meal-feeding administered on a fixed daily schedule entrains peaks of activity of intestinal enzymes (Stevenson and Fierstein, 1 9 7 6 ) . Therefore, timing each meal relative t o periods of physical activity and to e n d o g e n o u s r h y t h m s of metabolic e n z y m e s and metabolites may be i m p o r t a n t for improved conversion of feed to animal protein.
ACKNOWLEDGMENTS T h e a u t h o r s wish to t h a n k Dr. Larry Douglass for his time and very helpful r e c o m m e n d a tions regarding e x p e r i m e n t a l design and statistical testing.
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L D 1 2 : 1 2 p h o t o p e r i o d s c o n s u m e d most of their feed at t h e end of t h e day. In contrast, previous studies on fowl k e p t on 10 to 16 hr days indicated t h a t chickens eat m o s t at t h e beginning of each day (Siegel and Guhl, 1 9 5 6 ; Duncan et al., 1 9 7 0 ) . It is n o t clear why these differences in feeding p a t t e r n s exist in studies reported in t h e literature. However, t h e increased end of day feeding seems adaptive for birds in that it would ensure a full crop and gastrointestinal tract over t h e course of t h e long evening when n o feeding occurs. Use of a Photoperiod Coupled with Controlled Feeding of Broilers. T h e use of a p h o t o p e r i o d coupled with a controlled feeding schedule m a y be a possible t e c h n i q u e for improving growth rate and feed conversion of broilers. Cain and Wilson ( 1 9 7 4 ) have s h o w n that changes b e t w e e n light and darkness as exemplified by p h o t o p e r i o d regimes are one of the m o s t effective cues (or Zeitgebers) for entraining physiological r h y t h m s . In birds, biological r h y t h m s readily entrained by light include b o d y t e m p e r a t u r e , l o c o m o t o r activity, and feeding (Cain and Wilson, 1 9 7 4 ) . Therefore, a p h o t o p e r i o d can entrain feeding patterns which can be m a n i p u l a t e d b y controlled feeding schedules. T h e t y p e of feeding patterns exhibited by t h e meal-fed groups in Experiment 4 (Fig. 2), with the largest meal c o n s u m e d at t h e end of each d a y , m a y partly explain the increased efficiency c o m p a r e d to controls fed ad lib. For example, Halberg and his associates (as reported by R o m s o s and Leveille ( 1 9 7 7 ) ) have d e m o n s t r a t e d t h a t allowing h u m a n beings to eat a 2 0 0 0 kcal meal in t h e m o r n i n g resulted in a greater weight loss t h a n when t h e 2 0 0 0 kcal meal was c o n s u m e d in t h e evening. Eating followed by reduced activity appears t o be i m p o r t a n t for optimizing feed efficiency.
PERIODIC FEEDING OF BROILERS
REFERENCES
in the rat. Can. J. Physiol. 43:857-868. Masic, B., D. Wood-Gush, I. Duncan, C. McCorquodale, and C. Savory, 1974. A comparison of the feeding behaviour of young broiler and layer males. Brit. Poultry Sci. 15:499-505. Romsos, D. R., and G. A. Leveille, 1977. Influence of meal frequency and timing on physical activity and body weights of rats. Proc. Soc. Exp. Biol. Med. 154:457-460. Savory, C. J., 1976. Effects of different lighting regimes on diurnal feeding patterns of the domestic fowl. Brit. Poultry Sci. 17:341-350. Siegel, P. B., and A. M. Guhl, 1956. The measurement of some diurnal rhythms in the activity of White Leghorn cockerels. Poultry Sci. 35:1340—1345. Snedecor, G. W., and W. G. Cochran, 1967. Statistical methods. Iowa State Univ. Press, Ames, IA. Sokal, R. R., and F. J. Rohlf, 1969. Biometry. W. H. Freeman and Co., San Francisco. Stevenson, N. R., and J. S. Fierstein, 1976. Circadian rhythms of intestinal sucrase and glucose transport:cued by time of feeding. Amer. J. Physiol. 230:731-735. Wagstaff, R. K., 1976. The controlled feeding of broilers. Proc. 1976. Maryland Nutr. Conf. for Feed Manuf.: Informal Session.
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Association of Official Agricultural Chemists, 1975. Official methods of analysis. 12th ed. Washington, DC. Bunning, E., 1967. The physiological clock. SpringerVerlag, Inc. New York, NY. Cain, J. R., and W. O. Wilson, 1974. The influence of specific environmental parameters on the circadian rhythms of chickens. Poultry Sci. 53:1438—1447. Cohn, C , and D. Joseph, 1960. Role of rate of ingestion of diet on regulation of intermediary metabolism ("meal-eating" vs. "nibbling"). Metabolism 9:492-500. Donaldson, W. E., G. F. Combs, and G. L. Romoser, 1956. Studies on the energy levels in poultry rations. I. The effect of calorie-protein ratio of the ration on growth, nutrient utilization and body composition of c h i c k s . P o u l t r y Sci. 35:1100-1105. Duncan, I. J., A. R. Home, B. O. Hughes, and D. G. Wood-Gush, 1970. The pattern of food intake in female Brown Leghorn fowls as recorded in a Skinner box. Anim. Behav. 18:245-255. Leveille, G. A., and R. W. Hanson. 1965. Influence of periodicity of eating on adipose tissue metabolism
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INTRODUCTION
Gallus domesticus fowl are "nibblers", consuming food throughout the day. The data of Masic et al. (1974) clearly show that broilers on a 14-hr photoperiod feed each hr throughout the light period with greater feed consumption during the beginning and end of the photoperiod. Some laboratory mammals are likewise "nibblers" by nature and recent studies using growing rats have suggested that converting them to "meal-eaters" (periodic feeders) resulted in equivalent weight gain but greater feed efficiency (Cohn and Joseph, 1960; Leveille and Hanson, 1965). The pattern of food intake throughout the day and its manipulation may be important factors when considering techniques to improve growth rate and lower feed conversion in rapidly growing animals. The purpose of this study was to convert broiler chicks to periodic feeders to determine whether this behavioral manipulation might be
'Scientific Article No. A2356, Contribution No. 5366 of the Maryland Agricultural Experiment Station (Department of Poultry Science). 2 Submitted by B. E. C. in partial fulfillment of M.S. degree, University of Maryland. 3 This study was presented at the 66th Annual Meeting of the Poultry Science Association, Inc., Auburn, Alabama, 1977. 4 Send reprint requests to W. J. Kuenzel. 1978 Poultry Sci 57:719-725
useful in augmenting growth rate and lowering feed conversion in growing broilers. MATERIALS AND METHODS
Animals. Arbor' Acre male chicks (White Rock) were used in all experiments. Photoperiod. Broiler chicks were exposed either to continuous light or to photoperiods of LD14:10or 16:8. Feed and Housing. Chicks were fed a commercial broiler crumble diet calculated to contain 22 percent protein and 3234 kcal/kg metabolizable energy (ME) for Experiments 1 through 3. In Experiment 4 a diet was formulated to contain a slightly higher energy content (3454 kcal/kg ME, 23 percent protein). All chicks were housed in Petersime batteries with raised wire floors. In Experiment 4 chicks were moved to grow-out batteries by week 4 and were raised to 7 weeks of age, at which time broilers reached market weight of 2 kg. Meal-feeding Procedure. Chicks in all studies had food and water available ad lib. throughout the first week. Meal-feeding schedules were initiated at the start of week two. Chicks were allowed unlimited access to an unrestricted amount of feed during equally spaced 2 hr or l'/2 hr feeding periods (meals). Feed consumption was determined at the completion of each meal. Feeders were removed from pens throughout the day to ensure that no feeding occurred between feeding periods. All control
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ABSTRACT Broilers, Gallus domesticus, were converted to "meal-eaters" (periodic feeders), and food intake, growth, and body composition were evaluated. A meal was defined as unlimited access to an unrestricted amount of feed for a 2- or 1 1/2-hr feeding period. Employing a standard broiler starter ration, (3234 kcal/kg metabolizable energy (ME)), 1, 2, and 3 meals per day were found inadequate to support optimal growth and feed conversion. No significant differences were found in body weight, feed conversion or body composition between a 4-meal treatment group and controls fed ad lib. When a high energy ration (3454 kcal/kg ME) was fed to the following treatment groups: 3, 4, 5 meal, and ad lib. controls, the 5-meal group displayed a significantly greater rate of growth and a lower feed conversion. No significant differences were found in body composition or digestive tract measurements among any of the treatment groups. It is suggested that periodic feeding may be a possible technique for use by the broiler industry to further improve growth rate and feed conversion of broilers.
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FIG. 1. Feeding schedules for "meal-eating" treatment groups in Experiments 2, 3, and 4. The photoperiod for Experiments 2 and 3 was LD14:10. The photoperiod for Experiment 4 was LD16:8.
feeding on mean body weight, rate of body weight gain, and mean feed conversion (Snedecor and Cochran, 1967). Experimental Protocol. In Experiment 1 two groups of chicks were raised separately, fed ad lib, and exposed to continuous light or a photoperiod of LD14:10. Each treatment had 6 replications with 8 chicks per replication. In Experiment 2 chicks were assigned to one of three treatments: 1 meal, 3 meals, or ad lib. feeding. Each treatment had 8 replications (pens) with 8 chicks/pen and chicks were raised to 4 weeks of age. Time when meals were administered are shown in Figure 1. Chicks in Experiment 3 were assigned to one of four treatments: 2, 3, 4 meals, or ad lib. feeding. Each treatment had 4 replications with 7 chicks/pen and chicks were raised to 7 weeks of age. A high-energy diet of 3454 kcal/kg ME was fed throughout the study. Time periods throughout the day when meals were administered are shown in Figure 1.
RESULTS Experiment 1. Continuous Light Versus LD14:10. No significant differences were detected in body weight, total feed consumption, feed conversion, or body composition. Since broilers grown under LD14:10 performed comparably to those raised in continuous light, employing a photoperiod in future studies was justified due to the savings in electrical energy (amounting to 8 to 10 less hours of light per day). Use of a photoperiod also has a potential advantage of entraining endogenous rhythms in birds (Bunning, 1967). Experiment 2. 1 Meal, 3 Meals Versus Ad lib. Feeding. Data are shown in Tables 1 and 2. The 1-meal treatment showed a significant depression in body weight (P<.05), food intake (P<.05), and body fat content (P<.05) and a significant increase in percent moisture (P<.05). No significant differences were detected in body weight or body composition between the 3-meal and ad lib. treatments except percent body fat was lower in the 3-meal group (P<.05). Body weight of the 3-meal treatment group was consistently lower throughout the study. Data obtained for total feed consumption for the experiment showed the 1-meal treatment group consumed approximately 62% less feed than the ad lib. birds. The great distension of the crop at the end of the single meal per day suggested that a physical
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groups had food available ad lib. Body weight was measured at weekly intervals and total food intake calculated/week in order to compute feed conversion/week for all studies. Body Composition Procedure. Birds were sacrificed by cervical dislocation, placed in plastic bags, and frozen. Each frozen bird was cut using a band saw, ground in a Hobart grinder, packed into a plastic bag, and refrozen. Percent fat, moisture, and ash were determined by standard laboratory procedures (AOAC, 1975). Dried fat-free weight (DFFW, ash-free) was determined by difference and is a value very close to the true protein content of carcasses (Donaldson et ai, 1956). Statistical Methods. On the seventh day of each study, chicks were weighed, ranked, and blocked according to body weight. Each treatment group of Experiments 3 and 4 contained 4 blocks and each of the 4 blocks within all treatments had chicks of equivalent body weight. Body weight, feed conversion, body composition, and digestive tract data were analyzed statistically by two-way analysis of variance. Student-Newman-Keuls' multiplerange (SNK) test was used to separate means at the 5% level of significance (Sokal and Rohlf, 1969). Covariance analysis was employed for Experiment 4 to determine the effect of meal-
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TABLE l.—Body weight, food intake, and feed conversion of broilers fed ad libitum or meal-fed starter rations3-
Treatment
Body weight15 (g)
Experiment 2 1 - Meal 3 -Meal Ad libitum
295.1° 573. l c 626.7C
366.5d 805.9C 958.5C
1.63c 1.91c 1.85c
Experiment 3 2 - Meal 3 - Meal 4 - Meal Ad libitum
485.8e 558.9d 607.3 e 612.9C
538.3e 639.2 d 722.0C 73 5.6C
1.56d 1.77c 1.81c 1.82c
Experiment 4 3 - Meal 4 — Meal 5 - Meal Ad libitum
1835. l d 1917.0 cd 2003.3C 1903.6 cd
3507.2d 3644.5d 3816.4C 3727.6C
2.02c 1.97C 1.96c 2.16c
Total food intake/chick (g)
Feed conversion
Age of chicks at termination of study: Experiments 2 and 3, 4 weeks of age; Experiment 4, 7 weeks of age.
limitation of the digestive tract prevented adequate intake of nutrients. In addition, the very low food consumption of the 1-meal treatment group accounted for the significantly lower fat content and higher moisture content of their carcasses (Table 2). Experiment 3. 2, 3, 4 Meals Versus Ad lib. Feeding. Data are shown in Tables 1 and 2. The 2-meal treatment group had significantly lower body weight (P<.05) compared with the other treatments. By week 4, the mean body weight and percent of body fat of the 3-meal treatment group were significantly lower (P<.05) than those of the 4-meal and ad lib. treatment groups. Data of total feed intake showed that the 2-meal and 3-meal birds consumed approximately 27% and 13% less feed, respectively, than ad lib. controls. Experiment 4. High Energy Ration; Meal-fed Versus Ad lib. Feeding. Weekly body weight data are found in Table 3. Note that all treatment groups began the experiment with equal body weights and that controls fed ad lib. showed the greatest body weight gains through week 3. The 5-meal groups then surpassed controls and continued to show greater body weight gains through week 7. Total food intake for the 7-week period and final body weight and body composition data are shown in Tables
1 and 2. No significant differences were found in body weight, feed conversion, or body composition, using ANOVA and the SNK multiple-range test. Significant differences were found in food intake, with both the 5-meal and ad lib. groups consuming more food over the total 7-week study than the 4- and 3-meal groups. Data on body weight and feed conversion for each week of the 7-week study were next subjected to covariance analysis. Covariance analysis was used to determine if any significant differences existed among treatments in the rate of body weight gain and rate of change in feed conversion. In addition, mean body weight and feed conversion were analyzed for the entire study (determined by averaging weekly values from 2 through 7 weeks). Average weight and rate of gain for each treatment group are shown in Table 3. Based upon this analysis, the 5-meal birds showed a greater mean body weight compared to other treatments, yet total feed consumption was not significantly different between the 5-meal broilers and controls fed ad lib. The 5-meal group also displayed a significantly greater rate of gain (P<.05). No significant differences were detected in feed conversion among all treatments. The 5-meal broilers, however, showed a lower feed conversion and lower rate of increase in
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Photoperiod used: Experiments 2 and 3, LD 14.10; Experiment 4, LD 16:8. ME of diet: Experiments 2 and 3, 3234 kcal/kg; Experiment 4, 3454 kcal/kg. Within each column of each experiment, means with at least one like superscript are not significantly different (P<.05).
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722
DISCUSSION Importance of High Energy Ration for Meal-fed Broiler Chicks. Defining a meal as unlimited access to an unrestricted amount of feed during a VA- or 2-hr time period, 1 to 5 meals per day were fed to rapidly growing broiler chicks. Feeding 1 to 3 meals per day was found inadequate to support optimal growth in
broilers. Feeding 4 meals per day was found equivalent but not superior to ad lib. feeding when a standard broiler starter ration (3234 kcal/kg ME, 22% protein) was fed. When a high energy broiler ration (3454 kcal/kg ME, 23% protein) was used, a treatment of 5 meals per day was found superior to ad lib. feeding. Covariance analysis showed that the rate of body weight was significantly greater in the 5-meal group compared to ad lib. controls. Wagstaff (1976) has reported greater body weight gain and lower feed conversion in broilers subjected to controlled feeding and has stressed that high energy diets are essential for success of controlled feeding programs. Our data support his findings that high energy diets are important in controlled feeding of broilers. In addition, body composition analysis of meal-fed birds vs. birds fed ad lib. showed no significant differences in any component analyzed (Table 2). This finding is of importance since in mammalian studies rats converted to "meal-eaters" showed a signficantly higher percent body fat (Cohn and Joseph, 1960). The 5-meal broilers did not show a greater percent body fat compared to controls fed ad lib. (Table 2). Hence, the quality of the carcass does not appear to be adversely affected by the
TABLE 2.—Body composition of broilers fed ad libitum or meal-fed starter rations^
Percent moisture
Percent fat
Percent DFFWC (ash-free)
Percent ash
Experiment 2 1 - Meal 3 - Meal Ad libitum
69.26 d 66.22e 65.59 e
6.02 f 8.87 e 10.25 d
21.60 d 21.89 d 21.42 d
3.36 d 3.01 d 2.74 d
Experiment 3 2 - Meal 3 - Meal 4 — Meal Ad libitum
67.34 d 64.73 d 65.54 d
8.6 5 e 10.50 d 10.88 d
21.42 d 21.94 d 20.6 5 d
2.68 d 2.96 d 3.01 d
Experiment 4 3 - Meal 4 — Meal 5 - Meal Ad libitum
60.70 d 62.51 d 62.70 d 60.82 d
15.10 d 13.73 d 14.09 d 15.31 d
21.43 d 20.83 d 20.3 2 d 21.05 d
2.74 d 2.93 d 2.90 d 2.82 d
Treatment
15
Photoperiod used: Experiments 2 and 3, LD 14:10; Experiment 4, LD 16:8. ME of diet: Experiments 2 and 3, 3234 kcal/kg; Experiment 4, 3454 kcal/kg. Within each column of each experiment, means with at least one like superscript are not significantly different (P<.05). Age of chicks at termination of study: Experiments 2 and 3, 4 weeks of age; Experiment 4, 7 weeks of age. DFFW = dry faHree weight. DFFW (ash-free) is a close estimate of the true protein content of the carcass.
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feed conversion points for the study. Weights and linear measurements of digestive tracts and 15 digestive tract indexes from birds in Experiment 4 were subjected to statistical analysis. No significant differences were found among treatments. Pattern of Food Intake Per Day. The quantity of food consumed during each meal per treatment was computed for Experiments 2 through 4. Mean food intake per bird per meal was then determined on a weekly basis and graphed. Results of Experiment 4 are shown in Figure 2. The largest meal consumed per day was consistently the last meal before initiation of the dark period. This generalization was true for all experiments and did not shift during the development and growth of chicks from 2 through 7 weeks of age.
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TABLE 3.—Weekly body weights and rate of body weight gain of chicks in Experiment 4 Week
Treatment
Body wt (g) a
Part A. Weekly body weights 108.8 108.7 108.7 108.7
4.34 4.24 4.25 4.21
3 - Meal 4 — Meal 5 - Meal Ad libitum
273.0 279.8 290.4 295.4
12.34 7.3 5 7.89 9.80
3 - Meal 4 — Meal 5 -Meal Ad libitum
507.9 519.8 546.9 557.8
17.79 11.96 9.87 17.76
34 5Ad
Meal Meal Meal libitum
798.2 821.2 861.2 855.0
20.82 16.89 16.72 25.80
3 - Meal 4 — Meal 5 -Meal Ad libitum
1139.8 1221.6 1245.1 1209.2
21.64 23.27 21.13 41.89
3 - Meal 4 — Meal 5 - Meal Ad libitum
1475.4 1540.3 1608.0 1568.6
25.95 11.26 24.56 47.57
3 - Meal 4 — Meal 5 - Meal Ad libitum
1835.1 1917.0 2003.3 1903.6
22.04 17.48 33.84 46.96
Grand average body wt (g) b
Rate of gain (g/week)
1005.led 1050.2 f 1092.7 f 1065.l f
315.7 e 332.7 e 346.5 f 3 26.4 e
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Treatment
3 - Meal 4 — Meal 5 - Meal Ad libitum
Part B. Rate of body weight gain c 3 - Meal 4 — Meal 5 - Meal Ad libitum
.99 .99 .99 .99
Mean + SEM. Grand average 7-week body weight for each treatment computed by averaging weekly body weights from 2 through 7 weeks. Covariance analysis used to determine differences in rate of gain in body weight. Within each column, means bearing like superscripts are not significantly different (P<.05).
724
CONARD AND KUENZEL
ate
I I
iii U <
30
cc
a b e d
•
30
<
CC 0 2° a b c a e
mil
iiiiliiil WEEKS
FIG. 2. Pattern of food intake of broilers in Experiment 4. Lower case letters indicate meals or time intervals when feed was available to chicks. 3-Meal: a = 7:00-8:30 AM; b = 2:15-3:45 PM; c 9:30-1100 PM; 4-Meal: a = 7:00-8:30 AM; b = 12:00-1:30 PM; C = 4 : 3 0 - 6 : 0 0 PM; d = 9:30-11:00 PM; 5-Meal: a = 7:00-8:30 AM; b = 10:45-12:15 PM; C = 2:15-3:45 PM; d = 5:45-7:15 PM; e = 9:30-11:00 PM.
significantly faster rate of growth in meal-fed broilers. It should be n o t e d , however, t h a t this study included males only. F u t u r e e x p e r i m e n t s should be performed using females to determine if they respond similarly to periodic feeding. Pattern of Food Intake Per Day. In Experim e n t s 2 through 4, involving feeding 2 t o 5 meals per day, t h e largest meal consumed by broilers was consistently t h e last one before t h e start of t h e d a r k period ( E x p e r i m e n t 4 , Fig. 2). These results were o b t a i n e d using either a p h o t o p e riod of L D 1 4 : 1 0 or 1 6 : 8 . Similar feeding patterns were o b t a i n e d by Savory ( 1 9 7 6 ) w h o allowed chicks free access to feed over 12 hr p h o t o p e r i o d s with and w i t h o u t simulated d a w n and dusk periods. All chicks subjected to
In addition, meal-feeding administered on a fixed daily schedule entrains peaks of activity of intestinal enzymes (Stevenson and Fierstein, 1 9 7 6 ) . Therefore, timing each meal relative t o periods of physical activity and to e n d o g e n o u s r h y t h m s of metabolic e n z y m e s and metabolites may be i m p o r t a n t for improved conversion of feed to animal protein.
ACKNOWLEDGMENTS T h e a u t h o r s wish to t h a n k Dr. Larry Douglass for his time and very helpful r e c o m m e n d a tions regarding e x p e r i m e n t a l design and statistical testing.
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W
•
ml llll
CD
L D 1 2 : 1 2 p h o t o p e r i o d s c o n s u m e d most of their feed at t h e end of t h e day. In contrast, previous studies on fowl k e p t on 10 to 16 hr days indicated t h a t chickens eat m o s t at t h e beginning of each day (Siegel and Guhl, 1 9 5 6 ; Duncan et al., 1 9 7 0 ) . It is n o t clear why these differences in feeding p a t t e r n s exist in studies reported in t h e literature. However, t h e increased end of day feeding seems adaptive for birds in that it would ensure a full crop and gastrointestinal tract over t h e course of t h e long evening when n o feeding occurs. Use of a Photoperiod Coupled with Controlled Feeding of Broilers. T h e use of a p h o t o p e r i o d coupled with a controlled feeding schedule m a y be a possible t e c h n i q u e for improving growth rate and feed conversion of broilers. Cain and Wilson ( 1 9 7 4 ) have s h o w n that changes b e t w e e n light and darkness as exemplified by p h o t o p e r i o d regimes are one of the m o s t effective cues (or Zeitgebers) for entraining physiological r h y t h m s . In birds, biological r h y t h m s readily entrained by light include b o d y t e m p e r a t u r e , l o c o m o t o r activity, and feeding (Cain and Wilson, 1 9 7 4 ) . Therefore, a p h o t o p e r i o d can entrain feeding patterns which can be m a n i p u l a t e d b y controlled feeding schedules. T h e t y p e of feeding patterns exhibited by t h e meal-fed groups in Experiment 4 (Fig. 2), with the largest meal c o n s u m e d at t h e end of each d a y , m a y partly explain the increased efficiency c o m p a r e d to controls fed ad lib. For example, Halberg and his associates (as reported by R o m s o s and Leveille ( 1 9 7 7 ) ) have d e m o n s t r a t e d t h a t allowing h u m a n beings to eat a 2 0 0 0 kcal meal in t h e m o r n i n g resulted in a greater weight loss t h a n when t h e 2 0 0 0 kcal meal was c o n s u m e d in t h e evening. Eating followed by reduced activity appears t o be i m p o r t a n t for optimizing feed efficiency.
PERIODIC FEEDING OF BROILERS
REFERENCES
in the rat. Can. J. Physiol. 43:857-868. Masic, B., D. Wood-Gush, I. Duncan, C. McCorquodale, and C. Savory, 1974. A comparison of the feeding behaviour of young broiler and layer males. Brit. Poultry Sci. 15:499-505. Romsos, D. R., and G. A. Leveille, 1977. Influence of meal frequency and timing on physical activity and body weights of rats. Proc. Soc. Exp. Biol. Med. 154:457-460. Savory, C. J., 1976. Effects of different lighting regimes on diurnal feeding patterns of the domestic fowl. Brit. Poultry Sci. 17:341-350. Siegel, P. B., and A. M. Guhl, 1956. The measurement of some diurnal rhythms in the activity of White Leghorn cockerels. Poultry Sci. 35:1340—1345. Snedecor, G. W., and W. G. Cochran, 1967. Statistical methods. Iowa State Univ. Press, Ames, IA. Sokal, R. R., and F. J. Rohlf, 1969. Biometry. W. H. Freeman and Co., San Francisco. Stevenson, N. R., and J. S. Fierstein, 1976. Circadian rhythms of intestinal sucrase and glucose transport:cued by time of feeding. Amer. J. Physiol. 230:731-735. Wagstaff, R. K., 1976. The controlled feeding of broilers. Proc. 1976. Maryland Nutr. Conf. for Feed Manuf.: Informal Session.
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Association of Official Agricultural Chemists, 1975. Official methods of analysis. 12th ed. Washington, DC. Bunning, E., 1967. The physiological clock. SpringerVerlag, Inc. New York, NY. Cain, J. R., and W. O. Wilson, 1974. The influence of specific environmental parameters on the circadian rhythms of chickens. Poultry Sci. 53:1438—1447. Cohn, C , and D. Joseph, 1960. Role of rate of ingestion of diet on regulation of intermediary metabolism ("meal-eating" vs. "nibbling"). Metabolism 9:492-500. Donaldson, W. E., G. F. Combs, and G. L. Romoser, 1956. Studies on the energy levels in poultry rations. I. The effect of calorie-protein ratio of the ration on growth, nutrient utilization and body composition of c h i c k s . P o u l t r y Sci. 35:1100-1105. Duncan, I. J., A. R. Home, B. O. Hughes, and D. G. Wood-Gush, 1970. The pattern of food intake in female Brown Leghorn fowls as recorded in a Skinner box. Anim. Behav. 18:245-255. Leveille, G. A., and R. W. Hanson. 1965. Influence of periodicity of eating on adipose tissue metabolism
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