Broiler Response to Diet Energy

Broiler Response to Diet Energy S. LEESON, L. CASTON, and J. D. SUMMERS Department of Animal and Poultry Science, University of Guelph, Guelph, Ontario, Canada, NIG 2W1 ABSTRACT Male broiler chickens were fed cornsoybean s providing,, or kcal ME/kg. In all experiments, each treatment was tested with three replicate groups of 30 birds grown to 49 d of age. In Experiment 1, birds consumed the various s ad libitum whereas in Experiment 2, all birds received identical and restricted quantities of feed so as to ensure variable intakes of energy. In a third experiment, after 7 d of age, broilers had access to feed in two feeders that contained only the highest level of energy, or the kcal ME/kg in combination with one of the other s previously described. Providing s of to kcal ME/kg for ad libitum consumption had no effect on growth rate (P > ) and energy intake was constant; however, reducing the energy level of the did result in reduced carcass fatness (P < 0.01). When feed intake was controlled in Experiment 2, there was reduced growth (P < 0.01) rate as energy level of the was reduced. This reduced growth was associated with dramatic reduction in carcass fatness (P < 0.01), although breast meat yield was not affected. When broilers were offered a choice of s, they showed remarkably precise control of intake, such that energy intake was again constant across all treatments. However, even though energy intake was constant, broilers consuming the choice s involving the lower energy content s tended to have less carcass fat. It is concluded that the broiler still possesses a good ability to control its feed intake based on desire to normalize energy intake. As energy intake is decreased, or there is increased protein intake, the bird deposits less carcass fat. (Key words: broiler,, energy) 1996 Poultry Science 75:529-535 INTRODUCTION Broiler chickens have traditionally been fed relatively high-energy s, because, in addition to promoting efficient feed utilization, it is also assumed that this type of maximizes growth rate (Leeson and Summers, 1991). More recently, lower-energy content s have been tried in an attempt to resolve such problems as ascites (Leeson et al., 1995), and it is now realized that overall growth rate is little affected. The broiler chicken may, therefore, adapt to s of low energy content, and simply eat more feed in an attempt to maintain energy intake, much the same as does the Leghorn bird (Payne, 1967). Contrary to popular belief, the broiler chicken may not be eating to meet needs of physical satiety, although undoubtedly the bird's voracious appetite does play some role in influencing both feed and energy intake. Control over energy intake is important not only because it affects growth rate, but also because it has a potentially negative effect on carcass characteristics Qackson et al., 1982). However, there are few recent data Received for publication August 7, 1995. Accepted for publication November 29, 1995. available on the broiler's response to energy level and energy intake, to which those effects are not confounded by intake of other nutrients in the. A series of experiments were conducted to note the response of male broilers to situations of variable energy level, to conditions of variable energy intake, and to situations of self-selection involving choice based on ary energy concentration. Experiment 1 MATERIALS AND METHODS Three hundred and sixty 1-d-old male broiler chickens of a commercial strain were wing-banded, weighed, and allocated at random to one of four treatment groups. Each treatment group of 30 birds was replicated three times and housed in floor pens measuring 2. x 1.83 m. Temperature was maintained at 32.5 C for 5 d and gradually reduced in keeping with usual brooding practice. Four s were formulated to provide a similar nutrient profile with the exception of variable energy level (Table 1). Diets 1 through 4 were formulated to provide,, and kcal ME/kg, respectively, and birds in Treatments 1 through 4 were fed these s in that 529

530 LEESON ET AL. Ingredient and analysis Corn Soybean meal, 48% CP Animal-vegetable fat Dicalcium phosphate (20% P) Limestone Vitamin-mineral premix 1 Salt, 0.015% KI DL-methionine Coban Stafac Sand Oat hulls Calculated analysis Crude protein Energy, kcal ME/kg Methionine Lysine Calcium Available phosphorus TABLE 1. Percentage composition 1 8.65 2 6.15 1.25 1.25 Diet 3 3.65 2.50 2.50 4 1.15 3.75 3.75 iprovided per kilogram of ; vitamin A, 8,000 IU (retinyl palmitate); cholecalciferol, 40 /ig; vitamin E, 11IU (dl-a-tocopheryl acetate); riboflavin, 9.0 mg; biotin, 0.25 mg; pantothenic acid, 11.0 mg; vitamin B 12,13 mg; niacin, 26 mg; choline, 900 mg; vitamin K, 1.5 mg; folic acid, 1.5 mg; ethoxyquin, 125 mg; manganese, 55 mg; zinc, 50 mg; copper, 5 mg; iron, 30 mg; and selenium, 0.1 mg. order. These four s were fed throughout the entire trial to 49 d of age and birds were at all times allowed free access to feed and water. All birds were weighed individually at 25 and 49 d of age and feed intake was measured over these times. At 50 d of age, 15 birds were randomly selected from each pen for processing at the University's plant. After processing, the abdominal fat pad was removed and weighed (Griffiths et ah, 1977). Remaining carcasses were chilled in water at 4 C for 1 h then weighed and the breast meat on both left and right side of the carcass, consisting of the Pectoralis and Supracoracoideus muscles, was removed and weighed. Experiment 2 Three hundred and sixty commercial strain male broiler chickens were wing-banded, weighed, allocated, Days of age 1 to 4 5 6 7 9 10 11 12 13 14 15 to 48 TABLE 2. Feeding schedule for Experiment 2 Consumption (g/bird/d) ad libitum 25 27 29 31 35 37 39 45 47 +4 g and brooded in the same manner as those in Experiment 1. The same four s as used in Experiment 1 (Table 1) were used, although in this study all birds were fed identical daily quantities of feed as shown in Table 2. Birds were allowed free choice feed to 4 d and thereafter the restricted quantities. Birds were weighed and feed intake measured as described in Experiment 1. Birds were processed at 50 d of age, and carcass measurements taken as described previously. Experiment 3 Three hundred and sixty commercial strain male broiler chickens were wing-banded, weighed, allocated and brooded in the same manner as those in Experiment 1. The same four s were again used, although in this study treatments involved a selection of s from two feeders within each pen. Birds in Treatment 1 received two feeders of Diet 1 (Table 1) so that birds would be consuming only s with an energy level of kcal ME/kg. Birds in Treatment 2 were able to select from one feeder of Diet 1 ( kcal ME/kg) and one feeder of Diet 2 ( kcal ME/kg). Birds in Treatment 3 received one feeder of Diet 1 ( kcal ME/kg) and one feeder of Diet 3 ( kcal ME/kg), whereas in Treatment 4, birds received one feeder of Diet 1 ( kcal ME/kg) and one feeder of Diet 4 ( kcal ME/kg). All birds received only Diet 1 (Table 1) in one feeder to 7 d of age. After this time, birds were allowed free access to the feeder of their choice. Birds were weighed and feed intake measured as in Experiment 1. Fifteen birds per pen were processed at 50 d of age and carcass, abdominal fat pad and breast measured as described in Experiment 1.

BROILER DIET ENERGY TABLE 3. Performance of broilers fed s of variable energy content, Experiment 1 531 Body wei ght Body gain Feed intake Initial 49 d 0 to 0 to Linear regression R2 CV 42 0.01 2. 0.9 1,025 1,039 977 989 0.31 2.98 30.1 2,812 2,780 2,740 2,752 0.27 1.58 43.8 M (b> 984 997 936 948 0.32 3.06 29.5 1,788 1,7 1,763 1,763 0.02 2.61 46.0 2,772 2,738 2,699 2,711 0.27 1.60 43.7 1,468 1,481 1,497 1,658 0.60 3.82 58.3 (i* 'hirdl 3,003 3,620 3,709 3,927 * 0.48 10.2 365 4,471 5,101 5,206 5,585 0.57 7.17 365 P <. Statistical Analysis Experiment 1. Performance data, as body, feed intake, feed utilization, carcass characteristics and calculated data as protein and energy intake were analyzed by a simple linear regression model of one independent variable (level of energy). Experiment 2. The response variables body, feed utilization, carcass characteristics, and protein and energy intake were analyzed by a one-way analysis of variance for level of energy in the. Those response variables resulting in a significant F test were further analyzed using Duncan's multiple range test (Duncan, 1955). Experiment 3. The response variables body, feed intake, feed utilization, carcass characteristics, and protein and energy intake were analyzed by a one-way analysis of variance. For each treatment, feed intake was also calculated separately for the two feeders in each pen. These data were examined in terms of grams of feed consumed and percent (proportion) of total feed intake between 7 and and 25 and 49 d. Proportional data was arc sine transformed for analysis, but presented in tables as percentages. Experiment 1 RESULTS Body and body gain were unaffected by level of energy in the (Table 3). As energy level decreased so feed intake increased linearly (Table 3, P < 0.01). Feed intake to body gain data shows that birds offered s of lower energy responded by being significantly less efficient in terms of feed utilization between 0 to 25, 25 to 49, and (P < 0.01, Table 3). Total energy intake and energy consumed per kilogram of live body demonstrate that, although feed intake increased linearly with decreasing energy, birds in all treatment groups consumed essentially the same amount of energy during the trial (P >, Table 4). On the other hand, because protein levels of all s remained constant, total protein intake and grams of protein consumed per kilogram of live body increased significantly with decreasing energy level (P < 0.01, Table 3). Weight of carcasses, breast meat yield, and breast meat as a percentage of carcass were unaffected by energy level (P >, Table 5). Absolute and proportional of the abdominal fat pad decreased linearly with a decrease in energy level (P < 0.01, Table 5). Experiment 2 All birds received similar restricted quantities of feed, and so a range of energy intakes was imposed. At of age, birds fed s with or kcal/kg were smaller than those receiving the higher energy s (Table 6). At 49 d of age this trend became more pronounced in that birds fed kcal ME/kg were significantly lighter than birds in all other treatment groups (P < 0.01). Although birds fed kcal ME/kg were significantly heavier than birds fed kcal ME/kg, they were not significantly heavier than those birds fed either or kcal ME/kg (P > ). Feed efficiency over the experimental period of shows that birds fed energy levels of and kcal ME/kg were most efficient, followed by those birds fed kcal ME/kg, whereas birds fed the at kcal ME/kg were least efficient (P < 0.01). Carcass was affected by treatment in that birds fed an energy level of kcal ME/kg had significantly heavier carcasses than birds in all other treatment groups (P < 0.01, Table 7). Birds fed an energy level of kcal ME/kg had the smallest carcasses. Decreasing ary energy level resulted in a significant decrease in the size of the abdominal fat pad (P < 0.01) and this decrease was also reflected in abdominal fat pad as a percentage of carcass (P < 0.01). Breast meat yield and breast meat as a percentage of carcass were unaffected by level of energy in the (P >, Table 7). Experiment 3 Table 8 shows that the responses of body, body gain, feed intake, and feed intake:body

532 LEESON ET AL. TABLE 4. Feed and nutrient intake of broilers fed s of variable energy content, Experiment 1 0 to 49 d 0 to 49 d 0 to Feed intakerbody wei ght gain 25 to 49 d Total protein intake Protein/kg body Total energy intake Energy/kg body Linear regression R2 CV 1.49 1.49 1.60 1.75 0.77 3.69 0.06 1.68 2.08 2.10 2.23 0.51 10.0 0.20 1.61 1.86 1.93 2.06 4* 0.63 7.02 0.13 939 1,071 1,093 1,173 0.57 7.17 76.7 -(g) 339 391 405 433 4* 0.63 7.02 27.5 14,755 15,812 15,099 15,079 0.01 7.92 1,202 (kcal) 5,325 5,775 5,594 5,563 0.02 7.81 435 TABLE 5. Carcass characteristics of broilers fed s of variable energy content, Experiment 1 Carcass Breast meat carcass Deboned breast carcass Linear regression R2 CV 2,029 2,007 1,980 1,978 0.31 1.65 32.9 62.8 61.2 47.3 38.0 * * 0.87 7.83 4.10 366 367 364 361 0.06 2.20 8.03 3.10 3.05 2.39 1.93 0.84 8.61 18.0 18.3 18.4 18.2 0.11 1.46 0.27 TABLE 6. Performance of broilers fed fixed quantities of feed, Experiment 2 Initial 43 43 0.85 Body 825* 818 a 790 b 764b 13.5 4* 49 d 2,558* 2,599 a 2,439 b 2,303= 69.7 0 to (r-\ (& 782* 775 a 745b 72ib 13.7 a_c Column means with no common superscript differ significantly (P < ). *P <. Body l,733 a l,780 a 1,649* l,538 b 71.9 * gain 2,515 ab 2,555 a 2,395 b 2,259= 69.7 Feed intake:body gain (p-cr) yg-g) 1.84= 1.82= 1.94 b 2.05 a TABLE 7. Carcass characteristics of birds fed fixed quantities of feed, Experiment 2 Carcass l,806 a l,728 b l,674 b = 1,625= 34.8 53.7 a.5 b 31.0= 18.5* 1 3.15 Breast meat 326 319 311 304 11.6 a_d Column means with no common superscript differ significantly (P < ). carcass 2.97 a 2.58 b 1.85= 1.14<l 0.19 Deboned breast carcass 18.0 18.5 18.6 18.7 0.36

gain and the calculated values of energy intake and protein intake throughout the trial were unaffected (P > ) by self-selection based on energy content. Table 9 provides a breakdown of the intakes of individually selected s. As the level of energy in the experimental test decreased in Diets 2 through 4, so the amount of high-energy basal consumed by birds in Treatments 2 through 4 increased (P < 0.01). Therefore, as the energy level of the test decreased, birds voluntarily consumed less of this feed (Table 9). The proportion of the various s consumed remained remarkably stable over time. Thus, as the energy level of the choice test decreased from to and then to kcal/kg the proportion of these s eaten was about 45, 33, and 27%, respectively (Table 9). There was no consistent effect of selection on carcass (Table 10). Birds fed and kcal/ kg s produced smaller carcasses than birds fed or kcal/kg as the test choice. Weight of abdominal fat pad was significantly heavier (P < 0.01) in those birds fed only kcal ME/kg (Treatment 1), whereas birds fed the lowest energy s as choice had the smallest fatpads. Deboned breast was not affected by treatment (Table 10). DISCUSSION The broiler chicken seems somewhat immune to the effects of variable energy level on general growth and development. Contrary to the observations of Newcombe and Summers (1984), results from the current study suggest that the broiler is not normally eating to physical capacity, and have a remarkable ability to control energy intake when offered s of varying energy content. The pattern of energy intake seen in Experiment 1 and 3 suggest the broiler to be adjusting its feed intake, in response to energy needs, with the same classical precision as seen in Leghorn birds (Payne, 1967). Because s used in Experiment 1 differed only in energy content, then growth, and especially carcass characteristics, are confounded with intakes of protein and amino acids. With the lower energy s, therefore, because feed intake is elevated, there is a concomitant increase in crude protein intake, and this situation is known to reduce carcass fat deposition (Jackson et al., 1982). The effect of elevated protein intake on reducing carcass fatness must be a dominant factor, because these birds in fact consumed slightly more energy, and this itself is expected to result in increased, rather than decreased carcass fatness. Results from the second experiment clearly show the significance of energy intake on growth and development of the modern broiler chicken. As energy intake was controlled, then there was a direct negative effect on growth rate, even though the intake of all other nutrients was not changed across treatments. With reduced energy intake there was a dramatic effect on carcass fatness in the 49-d male broiler (Table 7), showing that, although fatness is affected by protein BROILER DIET ENERGY

534 LEESON ET AL. TABLE 9. Details of feed intake of broilers allowed self-selection of energy, Experiment 3 Diet choice 0 to 7 d 7 to (g/bird) (%) (g/bird) (%) (g/bird) (%) (g/bird) (%) + + + + ± 116 1 118 122 3.15 1,5* 672d 802= 945b 56.7 100= 53.0a 65.3= 73.6 b 3.70 0= 595* 426b 340b 47.4 0d 47.0" 34.7b 26.5= 3.70 3,355" 2,000= 2,240b= 2,678b 275.4 100* 56.6= 66.8b 73.5b 4.49 0= 1,531 l,105 b 953b 130.8 0= 43.4* 33.2 b 26.5b 4.48 a_d Column mean with no common superscript differ significantly (P < ). intake (Table 5), the most meaningful changes to fat deposition are controlled by energy intake. With a feed-energy choice situation broilers showed precision in their ability to control energy intake. A priori, we assumed that as the energy level of the test was reduced, then energy intake would also be reduced. The broiler seemed to combat this reduction in energy level by choosing less of the test as its energy level was reduced. Shariatmadari and Forbes (1993) have also shown the broiler chicken to make appropriate choices of s varying in protein content. Choice-feeding of broilers is not a new concept and has been tried with some success using whole-grains as the "choice" (Leeson and Caston, 1993). However there are few reports of choice-feeding involving only energy level as the choice, in which selection is not confounded by differences in texture as occurs with cereal feeding (Rose et al, 1986). Broilers do not seem to grow as fast when choice is based on s very different in nutrient profile, as occurs with cereal feeding (Cowan and Mitchie, 1978; Sinurat and Balnave, 1986). Although the s used in Experiment 3 are described as differing in energy content, it is realized that such differences were accomplished by changing the supplemental fat content of the, and that this may influence feeding behavior. When using isoenergetic s varying in fat content, Dale and Fuller (1978) showed a marked preference by broilers for high fat content s. In the present experiment, fat content of the s may therefore have been a contributing factor to differential intake of the various s. It would be worthwhile, but very difficult, to offer broilers a choice situation of s varying in energy content but where fat level was kept constant. In this context it would be interesting to try some of the new fat analogues destined for the human food industry. Another interesting factor in the results from Experiment 3 was the reduction in carcass fatness observed with choice-feeding involving the lower energy s, even when overall energy intake was not changed. If these results are real then perhaps the timing of energy intake throughout the day, as well as total daily energy intake, may play some role in fat deposition. It would be useful to study the hourly pattern of feed intake in such energy-level choice feeding situations. Results from this series of experiments show the significance of energy intake for the optimum growth and development of the broiler chicken. The modern broiler still seems to have an innate ability to control its energy intake, and this factor should be considered in developing feeding programs and in specifying various ary nutrient concentrations relative to energy. TABLE 10. Carcass characteristics at 49 d of broilers allowed self-selection of energy, Experiment 3 Diet choice ± Carcass 2,052*b 2,090* 2,010b 2,110* + 36.9 Abdominal fat pad (g)- 69.4* 61.4b 55.8= 55.6= 2.23 Breast 397 404 402 2 19.9 a_c Column means with no common superscript differ significantly (P < ). *P <. carcass 3.38* 2.94b 2.78b= 2.63= 0.09 Breast carcass 19.3 19.3 20.0 19.5 1.0

ACKNOWLEDGMENTS This work was conducted under contract with the Ontario Ministry of Agriculture, Food and Rural Affairs, Toronto, ON, Canada. REFERENCES Cowan, P. J., and W. Mitchie, 1978. Choice feeding of the male and female broiler. Br. Poult. Sci. 19:149-152. Dale, N. M., and H. L. Fuller, 1978. Effect of ambient temperature and ary fat on feed preference of broilers. Poultry Sci. 57:1635-1640. Duncan, D. B., 1955. Multiple range and multiple F tests. Biometrics 11:1-42. Griffiths, L., S. Leeson, and J. D. Summers, 1977. Fat deposition in broilers: Influence of system of energy evaluation and level of various fat sources on productive performance, carcass composition and abdominal fat pad size. Poultry Sci. 56:1018-1026. Jackson, S., J. D. Summers, and S. Leeson, 1982. The response of male broilers to varying levels of ary protein and energy. Nutr. Rep. Int. 25:601-612. BROILER DIET ENERGY 535 Leeson, S., and J. D. Summers, 1991. Broiler specifications Page 151 in: Commercial Poultry Nutrition. University Books, Guelph, ON, Canada. Leeson, S., and L. J. Caston, 1993. Production and carcass yield of broilers using free-choice cereal feeding. J. Appl. Poult. Res. 2:253-258. Leeson, S., G. Diaz, and J. D. Summers, 1995. Ascites. Pages 43- in: Poultry Metabolic Disorders and Mycotoxins. University Books, Guelph, ON, Canada. Newcombe, M., and J. D. Summers, 1984. Effect of previous on feed intake and body gain of broiler and Leghorn chicks. Poultry Sci. 63:1237-1242. Payne, C. G., 1967. Layer response to energy. Pages 40-54 in: Environmental Control of Poultry Production. T. C. Carter, ed. Longmans, London, UK. Rose, S. P., A. Burnett, and R. A. Elmaseed, 1986. Factors affecting the selection of choice-fed broilers. Br. Poult. Sci. 27:5-224. Shariatmadari, F., and J. M. Forbes, 1993. Growth and food intake responses to s of different protein contents and a choice between s containing two concentrations of protein in broiler and layer strains of chicken. Br. Poult. Sci. 34:959-970. Sinurat, A. P., and D. Balnave, 1986. Free-choice feeding of broilers at high temperatures. Br. Poult. Sci. 27:584.