3. BIRDS GROWN TO 3.3 KG'

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1 81997 Applied Poultry Science, Inc. OF FEEDING AND FINISHER DIETS FOR BROILERS 3. BIRDS GROWN TO 3.3 KG' CHANGING TIME STARTER, GROWER, E. A. SALEH, S. E. WATKINS, and I!M! WALDROd Poultry Science Department, University of Arkansas, Fayetteville, AR Phone: (501) FAX: (501) Primary Audience: Nutritionists, Production Managers, Researchers DESCRIPTION OF PROBLEM Producers commonly provide various diets throughout the growing cycle of broiler chickens, typically reducing the protein content and increasing the energy content as the bird ages. Because the cost of feed generally declines as the protein content is reduced, the optimum time for changing diets is of economic importance. Due to genetic improvements, the time required to reach market weights has been reduced, leading to shorter durations of feeding various diets [l]. In a recent survey of nutritional management needs of broilers, the Southeastern Poultry and Egg Federation identified the need to determine the optimum time to change diets as a high priority research area [2]. Because broiler chickens are grown to different weights to provide a variety of products to meet consumer demands, the optimum time of changing feeds may vary depending upon 1 Published with the approval of the Director, Arkansas Agricultural Experiment Station, Manuscript No To whom correspondence should be addressed

2 SALEH et al. Research Report 291 the desired fmal weight of the bird. One of the products in great demand by the poultry industry is a bud weighing approximately3.3 kg, used primarily for deboning. At present this body weight can be attained in approximately 56 days, depending upon the sex and strain of bird used. The National Research Council's [3] current nutrient recommendations for broiler chickens are based upon feeding a starter diet for 21 days, followed by a grower diet until 42 days of age, and a finisher diet from 42 to 56 days. In previous work from this station [l, 41, it was observed that straight-run broilers grown to 45 days of age could be changed from starter to grower diets as early as 14 to 17 days of age with no loss in performance. In these studies, the time of changing from starter to grower diet was the only feed management variable imposed. The objective of the present study was to determine the optimum time of changing from starter to grower and from grower to finisher diets for male broilers grown to approximately 3.3 kg. MATERIALS AND METHODS BIRDS AND HOUSING Male broiler chicks of a commercial strain [5] were obtained from a local hatchery. In each of two experiments, day-old chicks were randomly assigned to pens with 60 chicks placed in each of 48 pens (56 ft2) in a steeltruss broiler house of commercial design. The pens were equipped with two tube feeders and an automatic water font. Previously used softwood shavings with a topdressing of fresh shavings were used as litter over concrete floors. House temperature and ventilation were maintained by thermostatically controlled brooder stoves, ventilation fans, and automatic sidewall curtains. Incandescent lamps were used to supplement natural daylight to provide 23 hr of light and 1 hr of darkness. DIETS The starter, grower, and finisher diets were formulated to emulate current industry nutritional practice as reported by a popular agricultural survey [6] at the time the experiments were conducted. Table 1 shows the composition of the diets. Formulation was based upon the crude protein and moisture content of the ingredients actually used in TABLE 1. Composition and calculated nutrient content of diets Yellow corn Soybean meal Poultry by-product Poultry oil ME kcalikg Crude protein, % Calcium, 70 Nonphytate P, % -nine, 70 Lysine, % Methionine, 70 TSAA, 70 I I I I 0.77 I mixing the diets, with adjustments made in amino acid content. AI1 diets contained 5% poultry by-product meal, 60 dton salinomycin [7l as an anticoccidial, and bacitracin methylene disalicylate [8] as a growth promoter. The diets were adequately fortified with vitamins and trace minerals using commercially available premixes. All diets were pelleted with steam, and the starter diets were crumbled. Samples of mixed feeds analyzed for crude protein content were found to be in agreement with the calculated values.

3 292 CHANGING FEED FOR BROILERS The same diet composition was used in both experiments. EXPERIMENTAL TREATMENTS Birds in both experiments were fed for 56 days to reach a projected weight of approximately 3.3 kg. The first experiment employed 12 treatments administered in a 3 x 4 factorial arrangement, with three starter diet feeding times (0 to 7,O to 14, and 0 to 21 days) and four finisher diet feeding times (21 to 56,B to 56, 35 to 56, and 42 to 56 days). Grower diet was fed at varying times depending upon the termination of starter diet and the initiation of finisher diet. Four pens of birds received each dietary treatment. In the second experiment, there were also 12 treatments consisting of a 3 x 4 factorial arrangement, with three starter feeding times (0 to 7, 0 to 14, and 0 to 21 days) and four f~her diet feeding times (35 to 56,42 to 56, 49 to 56 days, or none). Grower diet was fed at varying times depending upon the termination of starter diet and the initiation of finisher diet. Four pens of birds received each dietary treatment. MEASUREMENTS For both trials pen body weights were determined at 56 days. Feed consumption during each feeding period was measured. Mortality was checked twice daily; buds that died were weighed and the weight used for calculating the feed conversion ratio (FCR; g feed/g gain). The calorie conversion ratio (CCR; ME kcavkg gain) was calculated by multiplying the consumption of starter, grower, and finisher diets by their respective caloric contents and dividing by the sum of the weight of live and dead birds. At 56 days, five birds per pen were randomly selected from birds marked at 1 day, weighed, wingbanded, subjected to 12-hr feed withdrawal, and processed in the University of Arkansas pilot processing plant with manual evisceration to determine dressing percentage, abdominal fat, and parts yield [9]. Data were analyzed as described [lo, 111. The same starter feeding periods were used in both experiments; therefore data reflecting the effects of starter feeding times in both studies were combined for statistical analysis. Because there were only two common finisher feeding times for the two experiments, no attempts were made to com- bine data on finisher feeding times from the two experiments. All statements of statistical sigdicance are based upon probability RESULTS AND DISCUSSION EXPERIMENT 1 The effects of changing the times of feeding the starter, grower, and finisher diets on the live performance and carcass characteristics of male broilers grown to 56 days of age to attain a live weight of approximately 3.3 kg are shown in Table 2. Only main effects are presented, as there were no si@icant interactions between time of feeding starter and time of feeding finisher diets. The time of feeding starter diet had no significant effect on body weight or mortality. Increasing the duration of feeding starter diet significantly increased FCR: for each additional day, FCR increased by Since the grower and finisher diets had a higher energy value than the starter diet, this increase in FCR was expected as birds fed starter diet for a longer time would have consumed a greater percentage of the lowerenergy starter diet. However, time of feeding starter diet did not si&icantly affect CCR, indicating that the chickens were able to effectively utilize calories regardless of the diet providing them. The time of feeding starter diet had little influence on carcass parameters. Increasing the duration of feeding starter diet significantly reduced leg quarter yield as a percentage of the carcass: each additional day of feeding starter diet resulted in a decrease of 0.04% in leg quarter yield. There was no significant effect of time of starter diet on dressing percentage, abdominal fat, breast meat, or wings. The time of initiating fmisher diet had a si@icant effect on several live production and carcass quality parameters. Body weight was significantly depressed with earlier initiation of finisher diet: each additional day of feeding finisher diet decreased body weight by 3.5 g. Both FCR and CCR were sigolficantly influenced by the time of feeding finisher diets: FCR was increased by and CCR was increased by 5.8 for each additional day of feeding finisher diet. Mortality, dressing percentage, breast meat, leg quarters, and wings were not significantly affected by the time of initiating finisher diet. Abdominal fat content fell significantly as the time that birds were maintained on finisher

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5 294 CHANGING FEED FOR BROILERS diets diminished: each additional day of feeding finisher diet increased abdominal fat by o,q29%. The finisher diet was higher in energy than the starter or grower diet, but its amino acid content was probably insufficient to support adequate utilization of its higher caloric content for birds receiving it at earlier ages, resulting in the increased deposition of abdominal fat. The NRC [3] nutrient recommendations for finisher diets are based on initiation at 42 days, and although the diets used in the present study are not based directly on NRC recommendations they do not differ markedly. EWERIMENT 2 The effects of changing the times of feeding starter, grower, and finisher diets on live performance and carcass characteristics of male broilers grown to 56 days to attain a live weight of approximately 3.3 kg are shown in Table 3. Only main effects are presented, as there were no significant interactions between time of feeding starter and time of feeding finisher diets. The time of feeding starter diet had no significant effect on body weight, FCR, CCR, mortality, dressing percentage, abdominal fat, leg quarters, or wing yield. Breast meat yield was significantly depressed by increasing the duration of feeding starter diet: each additional day resulted in a 0.04% reduction in breast meat yield. In contrast, our first study found no reduction in breast meat yield associated with time of feeding starter diet. As in Experiment 1, body weight was significantly influenced by the time of initiating finisher diet: each additional day of feeding finisher diet decreased body weight by 5 g. However, time of feeding finisher diet did not significantly affect FCR, CCR, or mortality. Dressing percentage, abdominal fat content, leg quarter yield, and wing yield were not significantly influenced by the time of feeding finisher diet. Duration of feeding finisher diet had a significant effect on breast yield: each additional day of finisher diet reduced breast meat yield by 0.037%. COMBINED TRIALS Table 4 shows the overall effects of the times of feeding starter diet in the two experiments. The time of feeding starter diet did not significantly affect 56-day body weight, CCR, mortality, dressing percentage, abdominal fat, breast meat yield, or wing yield. The FCR and leg quarter yield were significantly affected by duration of feeding starter diet: each day increase in feeding starter diet increased FCR by and reduced leg quarter yield by 0.028%. The time of changing from starter feed influenced the quantities of starter and grower feed consumed, with little effect on quantity of finisher feed consumed (Table 5). Birds fed starter diet for the ftrst 7, 14, or 21 days consumed an average of 129, 457, or 1,006 g of starter diet, respectively. This constituted approximately1.84,6.56, or 14.31% of the total feed consumed for the three age periods, respectively. Previous studies on the optimum time to change diets for broilers generally considered only changes between two diets, Le., between starter and grower diet [l, 4, 121, starter and finisher diet [13, 14, 15, 161, or grower and finisher diet [17]. Few studies consider variable times of feeding starter, grower, and finisher diets in the same feeding program. From the present study, it appears that for male broilers grown to achieve a target weight of approximately 3.3 kg, feeding the starter diet for no more than 7 days yields maximum live performance and carcass characteristics. Additionally, finisher diets should not be fed earlier than 42 days of age. These conclusions, however, apply only to diets formulated to meet current industry standards. Diets of lower nutrient quality may require commensurate adjustments in feeding times. However, in previous reports from our laboratory [l, 41 using diets formulated to provide 100,110, or 120% of suggested amino acid levels, there were no significant interactions of amino acid levels and time of changing starter diets for broilers grown to 45 days. Under almost any pricing situation, the cost of feed decreases from starter to grower to finisher feeds. Therefore, minimizing the times of feeding starter feeds without sacrificing productivity should enhance profitability. Data obtained in the present study indicate that feeding starter feed to 7, 14, or 21 days would require approximately 60, 214, or 470 tons of starter feed per one million 3.3 kg birds produced, respectively, with commensurate adjustments in the amount of grower feed.

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7 296 JAPR CHANGING FEED FOR BROILERS TABLE 5. Effect of changing time of feeding starter diets on consumption of different types of feed by male broilers grown to 56 days of age (mean of two experiments) CONCLUSIONS AND APPLICATIONS The optimum duration for feeding starter diet to birds grown to a target weight of approximately 3.3 kg appears to be no more than 7 days. The time of initiation of the finisher diet has a profound effect on live performance and carcass composition, Inclusion of the finisher diet earlier than 42 days resulted in a reduction in body weight, a deterioration in feed conversion and calorie utilization, an increase in abdominal fat, and a reduction in breast meat yield. Given typical cost differences among starter, grower, and finisher diets, the economic impact of changing diets at earlier ages may be considerable. These recommendations may not apply to diets of different nutrient content. 1. Walkins, S.E., kl Waldroup, andp.w. Waldroup, Effect of dietaryamino acid level on time of change from starter to grower diets for broiler chickens. J. Appl. Poultry R~s Beard, C.W., Southeastern Poultry & Egg Association industry survey-based research needs rioritized within each major category. Southeastern Foultry & Egg Association, Tucker, GA Personal communication.

8 SALEH et ai. Research Report National Research Council, Nutrient Requirements of Poultry. 9th Rev. Edition. Natl. Acad. Press, Washington, DC. 4. Waldroup, P.W., S.E Watkins, J.T. Skinner, M.H. Adam and kl Waldroup, Effect of dietaryamino acid level on response to time of change from starter to grower diets for broiler chickens. J. Appl. Poultry Res. 1: Ross 308, Ross Breeders, Elkmont, AL Agrimetrics Associates, Inc., Richmond, VA Bio-Cox, Agri-Bio Corp., Box 897, Gainesville, GA BMD, ALPharma, One Executive Drive, Ft. Lee, NJ Izat, A.L, M. Colberg, M.A. Reiber, M.H. Adams, J.T. Skinner, M.C. Cabel, H.L Stilborn, and P.W. Waldroup, Effects of different anticoccidials on performance, processing characteristics, and parts yield of broiler chickens. Poultry Sci Data were initially subjected to analysis of variance using a factorial arrangement of time of feeding starter diet, time of commencingfinisherdiet,and the interaction of time of feeding starter diet and finisher diet as variables. The General Linear Models procedure of the SAS Institute [ll] was utilized in theanalysis. Afterascertaining that no si ificant (PS.05) interactions existed between time of Eding starter diet and time of commencing finisher diet, the main effects of starter diet time and finisher diet time were subjected to regression analysis that tested linear and quadratic models for starter feeding time and linear, quadratic, and cubic models for finisher feeding time. Regression analysis was performed using PROC REG of the SAS Institute. Percentage data were transformed to arc sine and mortalitydata to square root for analysis. Data are presented in the table as natural numbers. 11. SAS Inslitute, SAS User s Guide: Statistics. SAS Institute, Cary, NC. 12. Yule, WJ., Optimum change to finisher diet and most efficient marketing age of sex separated broilers. Nutr. Rep. Intl. 14: Powell, T.S. and M.H. Gehle, Effect of different feeding regimes on performance of color sexed broilers, sexes reared separate. Nutr. Rep. Intl Gchle, M.H., T.S. Powell, and LG. Arends, Effect of different feeding regimes on performance of broiler chickens reared sexes separate or combined. Poultry Sci. 53: Proudfoot, F.G. and H.W. Hulan, Performanceof chicken broilers changed from starter to finisher diets at different ages. Can. J. Anim. Sci Roush, W.B., An investigation of protein levels for broiler starter and finisher rations and time of ration change by response surface methodology. Poult~y Sci Diambra, O.H. and M.G. McCartney, Performance of male broilers changed from starter to finisher diets at different ages. Poultry Sci. 64: