J. Appl. Poult. Res.
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J APPL POULT RES 2006. 15:190-197
© 2006 Poultry Science Association
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Research Reports

Effect of Soybean Oil Supplementation to Low Metabolizable Energy Diets on Production Parameters of Broiler Chickens

G. W. Barbour*, M. T. Farran{dagger},1, N. N. Usayran{ddagger}, A. H. Darwish{dagger}, M. G. Uwayjan{dagger} and V. M. Ashkarian{dagger}

* Department of Poultry Science, Lebanese Agricultural Research Institute, Tel Amara, Beqa’a, Lebanon; {dagger} Department of Animal Sciences, Faculty of Agricultural and Food Sciences, American University of Beirut, Beirut 1107-2020, Lebanon; and {ddagger} Department of Animal Production, Faculty of Agricultural Sciences, Lebanese University, Chourane, Beirut 1102-2040, Lebanon

Correspondence: 1 Corresponding author: mf02{at}aub.edu.lb


   SUMMARY
TOP
 SUMMARY
DESCRIPTION OF PROBLEM
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 CONCLUSIONS AND APPLICATIONS
 REFERENCES AND NOTES
 
Two experiments were conducted to study the performance and carcass quality of broilers in response to varying composition of a diet low in ME, through the supplementation of graded levels of soybean oil. In an initial study, isocaloric (2,965 kcal/kg) and isonitrogenous (21.7%) corn-soybean diets were supplemented with 10, 20, or 30 g/kg of soybean oil. In a second experiment, diets containing ME levels of 2,940 and 3,040 kcal/kg were supplemented with soybean oil levels of 20 or 40 g/kg. In both experiments, supplementation of up to 30 or 40 g of oil/kg of diet resulted in increases of 175 and 120 g (P < 0.05) in BW gain and 97 and 91 g (P ≤ 0.06) in ready-to-cook (RTC) carcass weight at 49 d, respectively. There was a linear decrease (P < 0.05) in percentage deposition of abdominal fat pad only in diets containing 2,965 (Experiment 1) or 2,940 (Experiment 2) kcal of ME/kg with no significant changes in RTC carcass and whole breast or pectoralis major muscle yields and RTC carcass composition. Improvements in production parameters can be achieved in broiler chickens fed a low ME diet through the addition of moderate levels of soybean oil.

Key Words: soybean oil • low metabolizable energy diet • performance • broiler


   DESCRIPTION OF PROBLEM
TOP
 SUMMARY
 DESCRIPTION OF PROBLEM
MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 CONCLUSIONS AND APPLICATIONS
 REFERENCES AND NOTES
 
The response of commercial broilers to supplemental dietary fat varies with respect to the type of supplemental fat and its inclusion rate [1, 2, 3]. Griffiths et al. [4] reported that by increasing the proportion of supplemental animal-vegetable blend fat from 0 to 60 g/kg in isocaloric diets (2,963 kcal/kg), feed conversion was improved without any effects on BW, feed intake, abdominal fat, or whole carcass composition. In a subsequent experiment, 30, 60, or 90 g/kg of corn oil added to isocaloric corn-soybean meal diets (2,926 kcal/kg) increased BW in 4-wk-old male broilers compared with those fed equal quantities of diets with no added oil. Those improvements in performance were related to enhanced use of calories beyond what was accounted for in terms of calculated dietary ME, and this was especially true in the case of vegetable oils [5].

Increasing ME from 2,970 to 3,190 kcal/kg had no effect on weight gain or on the proportion of abdominal fat deposited, but there was a reduction in feed intake and improved feed conversion of male broiler chickens fed a corn-soybean meal diet from 4 to 8 wk of age [6]. In more recent studies, linear increases in weight gain and feed efficiency were observed when male broiler chickens were fed corn-wheat-soybean meal diets in which ME was increased from 2,800 to 3,000 kcal/kg through changes in supplemental soybean oil or dietary carbohydrate levels [7].

In some Middle Eastern and African countries, vegetable oils such as soybean oil ($850/ton), sunflower oil ($900/ton), or cottonseed oil ($400/ton) are the major sources of supplemental fat available for use in poultry rations [8, 9]. The high cost of supplemental energy necessitates the optimization of fat inclusion and calorie levels at concentrations lower than the norm in other parts of the world where vegetable-animal blend fat is considerably less expensive [10]. There is also a trend toward not using animal by-product sources of protein and fat in poultry rations in the Middle East, fueled by concerns about bovine spongiform encephalopathy and its association with rendered animal products [11]. In addition to cost and food safety concerns, there is a demand for low-fat poultry products that can be produced by feeding diets with relatively low ME levels [12, 13]. In commercial formulation of poultry rations, fat or oil supplementation occurs with major adjustments in corn and soybean meal levels [5, 14]. Therefore, the objective of the present study was to evaluate the effect of such dietary changes in linear-formulated corn-soybean meal diets low in ME with and without supplemental oil on performance and carcass quality of broiler chickens.


   MATERIALS AND METHODS
TOP
 SUMMARY
 DESCRIPTION OF PROBLEM
 MATERIALS AND METHODS
RESULTS
 DISCUSSION
 CONCLUSIONS AND APPLICATIONS
 REFERENCES AND NOTES
 
Birds and Management
In Experiment 1, 1,020 one-day-old male Arbor Acres [15] broiler chicks were wing-banded and randomly distributed among 20 floor pens with 51 chicks per pen. In Experiment 2, 900 straight-run, 1-d-old chicks (Avian 43 [15]) were wing-banded and distributed among 18 floor pens with 25 males and 25 females per pen. Pen allocations in both experiments were such that all pens had similar average starting BW. The birds were reared in a conventional poultry house with raised side windows.

Diets and Experimental Design
Isocaloric and isonitrogenous corn-soybean meal diets were formulated to contain 0 or 30 g/kg of soybean oil after adjustments in corn and soybean meal levels (Table 1Go). Diets containing 10 or 20 g/kg of soybean oil were prepared via blending of appropriate proportions of the diets containing 0 and 30 g/kg of soybean oil. The starter diet was fed from d 1 to 21, and contained 21.7% CP and 2,965 kcal of ME/kg on an as-fed basis. In the finisher diet (d 21 to 49), CP and ME were 18.6% and 3,045 kcal/kg, respectively. All other nutrients met or exceeded nutrient requirements of the broiler chicken [16]. There were 5 replicate pens per treatment.


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  		Table 1. Composition of experimental diets
 
In Experiment 2, corn-soybean meal diets containing either 2,940 or 3,040 kcal/kg were formulated, and contained 0, 20, or 40 g/kg of soybean oil. The mixing procedures were similar to those described for Experiment 1 (Table 1Go). Crude protein was 21.4% (d 1 to 21) and 19.2% (d 21 to 49). Treatments with 2 levels of ME (2,940 and 3,040 kcal/kg) and 3 levels of soybean oil (0, 20, and 40 g/kg) were distributed following a complete randomized design, in which each experimental diet was fed to 3 replicate pens. In both experiments feed and water were provided ad libitum with a continuous lighting program.

Measurements and Chemical and Statistical Analysis
Initial BW of chicks, and BW and feed intake at 21 and 49 d of age were determined. At the end of Experiment 1, 5 birds per pen (10% of initial number of birds per pen) with BW representing ±5% average pen BW were selected [17, 18, 19, 20], and kept overnight in cages with drinking water only, before processing. All viscera, abdominal fat, giblets, preen glands, shanks, and heads were manually removed [20]. The weight of ready-to-cook (RTC) carcass and abdominal fat pad was recorded. The carcasses were stored at –22°C for later analysis. After thawing of RTC carcasses for approximately 18 h at ambient temperature, the left pectoralis major and supracoracoideus muscles were removed and weighed. The whole RTC carcass was subsequently ground [21], homogenized [22], and a representative sample was analyzed for moisture, CF, and CP [23].

At the end of Experiment 2, the same procedure was followed with the exception that 4 male and 4 female birds per pen were selected, weighed, and processed. The weight of the pectoralis major muscle was recorded [17] and the left half of the RTC carcass was ground for proximate analysis. Data in both experiments were statistically analyzed [24, 25].


   RESULTS
TOP
 SUMMARY
 DESCRIPTION OF PROBLEM
 MATERIALS AND METHODS
 RESULTS
DISCUSSION
 CONCLUSIONS AND APPLICATIONS
 REFERENCES AND NOTES
 
The addition of 30 g/kg of soybean oil to a diet with 2,965 kcal of ME/kg and no added oil in the first experiment resulted in a decrease of 89 g/kg in corn and an increase of 15 g/kg in soybean meal (Table 1Go). Growth, carcass yield, and carcass composition data from male broilers reared in Experiment 1 are presented in Table 2Go. The addition of 20 or 30 g/kg of soybean oil improved feed efficiency without affecting weight gain during the starter period (P < 0.05). Cumulative weight gain was also improved (P < 0.05) through the addition of oil at 20 or 30 g/kg. An inclusion rate of 30 g/kg of soybean oil was required to improve feed efficiency from 1 to 49 d of age (P < 0.05). The absolute weight of the RTC carcass, but not carcass yield, increased with increasing dietary oil levels up to 30 g/kg (P ≤ 0.06). It is worth mentioning that the improvement in RTC carcass weight was achieved with the lowest level of oil supplementation. The linear improvement in RTC carcass weight in response to dietary oil supplementation was accompanied by a linear decrease in the relative weight of the abdominal fat pad (P ≤ 0.05) without affecting relative breast muscle weight or RTC carcass composition.


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  		Table 2. Performance and carcass quality of Arbor Acres male broilers raised to 49 d of age in response to varying levels of soybean oil in a diet low in ME
 
In Experiment 2, the supplementation of 40 g/kg of soybean oil in diets containing 2,940 or 3,040 kcal/kg and no added oil resulted in a decrease of 120 g/kg of corn and an increase of 21 g of soybean meal/kg of diet (Table 1Go). Live performance and carcass parameters of broiler chickens fed a corn-soybean meal diet with 2,940 or 3,040 kcal/kg and graded levels of added oil are shown in Table 3Go. The addition of 20 g/kg of soybean oil to a starter diet with either 2,940 or 3,040 kcal/kg resulted in a linear increase (P ≤ 0.05 and P ≤ 0.09, respectively) in weight gain. Although birds fed the diet with 2,940 kcal/kg and 40 g/kg of soybean oil did not respond to oil supplementation during the starter period, their cumulative growth linearly improved (P < 0.05) at market age. The linear improvement in BW of starter birds on the higher energy diet (3,040 kcal/kg) with 40 g/kg of added soybean oil was maintained throughout the experiment (P < 0.05). No improvement in feed efficiency was observed in response to the addition of soybean oil to the 2,940 or 3,040 kcal/kg diets during the whole experimental period.


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  		Table 3. Performance and carcass quality of Avian 43 straight-run broilers raised to 49 d of age in response to graded levels of soybean oil supplementation in diets containing 2,940 or 3,040 kcal/kg
 
Weight of RTC carcass was increased in response to adding 40 g/kg of soybean oil to the diets with 2,940 and 3,040 kcal/kg (P < 0.05 and P ≤ 0.06, respectively). A concomitant decrease in abdominal fat pad relative size in response to 40 g/kg of soybean oil supplementation was only observed for birds consuming the 2,940 kcal/kg diet (P ≤ 0.05). The relative size of the abdominal fat pad in birds fed the 3,040 kcal/kg and no added oil diet was numerically higher than that in birds on the diets with supplemental oil. Ready-to-cook carcass yield, pectoralis major muscle percentage weight, and RTC carcass composition were not affected by oil addition for the 2 ME diets.


   DISCUSSION
TOP
 SUMMARY
 DESCRIPTION OF PROBLEM
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
CONCLUSIONS AND APPLICATIONS
 REFERENCES AND NOTES
 
Within the realm of poultry nutrition research, there may be numerous factors within a given experiment that can influence carcass composition, particularly carcass fat. The interpretation of a given set of results can be further compromised in the presence of genotype by diet interactions, particularly where genotypes have been developed for expression of distinct carcass characteristics. Keren-Zvi et al. [2], for example, reported that carcass fat deposition was reduced by soybean oil supplementation (0 vs. 46.5 g/kg) in a broiler line selected for increased abdominal fat deposition, whereas there were no dietary effects in the low abdominal fat line. All other performance measurements were similar in both lines. Within commercial genotypes, there are also genotype by diet interactive effects on growth and development. Farran et al. [20] reported that under a plan of management and nutrition common to the Middle East, Arbor Acres broilers were heavier and had improved feed use compared with Hybro N strain broilers.

Due to the high cost of dietary energy (kcal) in the Middle East, it is important to continually evaluate the source as well as the level of energy in practical type diets. In both experiments reported herein, there were linear increases in BW with each increment of soybean oil inclusion and there was a similar response in feed efficiency in Experiment 1. The feed efficiency response observed in the first experiment may have been an indirect result of enhanced growth rate to achieve a standard market BW set by the genetic makeup of the strains used in both experiments (Tables 2Go and 3Go). The clearly defined benefit observed in Experiment 1 may also have been a result of the simple experimental design, which became more complex in the second experiment due to changes in ME and composition of diets similar in soybean oil content.

In both studies, the increased RTC carcass weight resulting from oil supplementation followed closely the increased BW associated with these treatments. The increased abdominal fat and decreased or unchanged feed efficiency associated with zero supplemental oil and lack of any treatment effects on RTC carcass yield and composition in both experiments suggest that these birds are channeling their excess calories into less energetically efficient abdominal (carcass) fat rather than more efficient carcass protein. The role of linoleic acid in affecting energy efficiency may be excluded because adequate amounts of that essential fatty acid were already present in the basal diets that had no added oil (Table 1Go). The fact that the treatment differences were more evident at 49 vs. 21 d of age suggests that supplementing the diets with soybean oil may be more cost effective over the latter half of the growing period because of increased digestibility of fat [1] and improved use of dietary ME [3]. This period corresponds with the period during which feed intake is greater and the bird has the opportunity to benefit from the "extra-caloric" value of supplemental fat [3, 5, 26].


   CONCLUSIONS AND APPLICATIONS
TOP
 SUMMARY
 DESCRIPTION OF PROBLEM
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 CONCLUSIONS AND APPLICATIONS
REFERENCES AND NOTES
 

  1. Feeding low ME vegetable rations (2,950 to 3,050 kcal/kg) containing 30 or 40g/kg of soybean oil significantly improved BW gain of broilers at market age with inconsistent changes in feed use.
  2. Oil supplementation increased RTC carcass weight and concomitantly reduced abdominal fat pad percentage weight.
  3. Supplemental oil had no effect on breast muscle yield and RTC carcass moisture, protein, and fat percentages.
  4. The inclusion of oil was found to be more effective during the finisher period.


   ACKNOWLEDGMENTS
 
This research was partially funded by the Lebanese National Council for Scientific Research, Lebanon. The authors wish to thank M. S. Lilburn, The Ohio State University, OARDC (Wooster, OH) for his efforts in reviewing and suggesting improvements on the manuscript and M. A. Afram, Director, Lebanese Agricultural Research Institute (Beqa’a, Lebanon) for supporting the research work.


   REFERENCES AND NOTES
TOP
 SUMMARY
 DESCRIPTION OF PROBLEM
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 CONCLUSIONS AND APPLICATIONS
 REFERENCES AND NOTES
 

  1. Wiseman, J., and F. Salvador. 1989. Influence of age, chemical composition and rate of inclusion on the apparent metabolisable energy of fats fed to broiler chicks. Br. Poult. Sci. 30:653–662.[ISI][Medline]
  2. Keren-Zvi, S., I. Nir, Z. Nitsan, and A. Cahaner. 1990. Effect of dietary concentration of fat and energy on fat deposition in broilers divergently selected for high or low abdominal adipose tissue. Br. Poult. Sci. 31:507–516.[ISI][Medline]
  3. Nitsan, Z., A. Dvorin, Z. Zoref, and S. Mokady. 1997. Effect of added soyabean oil and dietary energy on metabolizable and net energy of broiler diets. Br. Poult. Sci. 38:101–106.[ISI][Medline]
  4. Griffiths, L., S. Leeson, and J. D. Summers. 1977. Influence of energy system and level of various fat sources on performance and carcass composition of broilers. Poult. Sci. 56:1018–1026
  5. Pesti, G. M., R. I. Bakalli, M. Qiao, and K. G. Sterling. 2002. A comparison of eight grades of fat as broiler feed ingredients. Poult. Sci. 81:382–390.[Abstract/Free Full Text]
  6. Griffiths, L., S. Leeson, and J. D. Summers. 1977. Fat deposition in broilers: Effect of dietary energy to protein balance, and early life caloric restriction on productive performance and abdominal fat pad size. Poult. Sci. 56:638–646.
  7. Plavnik, I., E. Wax, D. Sklan, I. Bartov, and S. Hurwitz. 1997. The response of broiler chickens and turkey poults to dietary energy supplied either by fat or carbohydrates. Poult. Sci. 76:1000–1005.[Abstract/Free Full Text]
  8. Freiji, S. G. 2003. Poultry Producers Syndicate, Beirut, Lebanon. Personal communication.
  9. Subuh, A. M. 2003. Syrian College of Veterinary Medicine, Hama, Syria. Personal communication.
  10. Ingredient Market. 2002. Feedstuffs 74:20.
  11. Elliott, I. 2000. EU starts costly ban on meat and bone meal. Feedstuffs 72 (51):1, 23.
  12. Leeson, S., and J. D. Summers. 1997. Page 2 in Commercial Poultry Nutrition. 2nd ed. University Books, Guelph, ON, Canada.
  13. Dvorin, A., Z. Zoref, S. Mokady, and Z. Nitsan. 1998. Nutritional aspects of hydrogenated and regular soybean oil added to diets of broiler chickens. Poult. Sci. 77:820–825.[Abstract/Free Full Text]
  14. Deaton, J. W., J. L. McNaughton, F. N. Reece, and B. D. Lott. 1981. Abdominal fat of broilers as influenced by dietary level of animal fat. Poult. Sci. 60:1250–1253.
  15. Tanmia Agricultural Development Co. Sal, Beirut, Lebanon.
  16. National Research Council. 1994. Nutrient Requirements of Poultry. 9th rev. ed. Natl. Acad. Press, Washington, DC.
  17. Lehmann, D., M. Pack, and H. Jeroch. 1997. Effect of dietary threonine in starting, growing, and finishing turkey toms. Poult. Sci. 76:696–702.[Abstract/Free Full Text]
  18. Peebles, E. D., J. D. Brake, and M. A. Latour. 1997. Broiler performance, yield, and bone characteristics as affected by starter diet fat level. J. Appl. Poult. Res. 6:325–330.[Abstract/Free Full Text]
  19. Bartov, I., and I. Plavnik. 1998. Moderate excess of dietary protein increases breast meat yield of broiler chicks. Poult. Sci. 77:680–688.[Abstract/Free Full Text]
  20. Farran, M. T., R. F. Khalil, M. G. Uwayjan, V. M. Ashkarian, and R. N. Hajj. 2000. Performance and carcass quality of commercial broiler strains. J. Appl. Poult. Res. 9:252–257.[Abstract/Free Full Text]
  21. Hobart Model 84145 meat grinder, Hobart Corp., Troy, OH.
  22. Model 320, Model Depose grinder, Moulinex, Moulinette, Ecully Cedex, France.
  23. AOAC. 1990. Official Methods of Analysis. 15th ed. Association of Official Analytical Chemists, Arlington, VA.
  24. SAS User’s Guide. 1992. Version 5 ed. SAS Inst. Inc., Cary, NC.
  25. In both experiments a complete randomized design was used. In Experiment 1 the statistical model to test the effect of soybean oil supplementation on performance and carcass quality was: Yij = µ + Oi + Eij, where Yij = observed value for the jth replicate of the ith level of oil, µ = grand mean, Oi = fixed effect of oil for its ith level, and Eij = random error associated with Yij experimental unit. The statistical model used in experiment 2 was: Yijk = µ + Mi + Oj + MiOj + Eijk, where Yijk = observed value for the kth replicate of the ith level of ME and the jth level of oil, µ = grand mean, Mi = fixed effect of ME for its ith level, Oj = fixed effect of oil for its jth level, MiOj = interaction effect for the ith level of ME and the jth level of oil, and Eijk = random error associated with Yijk experimental unit. The interaction term between ME and oil was dropped from the model when found not significant and the orthogonal contrast of GLM procedure was used in both experiments to determine significant linear or quadratic relationships between zero and the incremental oil level, at P ≤ 0.05. When significant linear or quadratic effects were identified, the highest oil dietary treatment was deleted and orthogonal contrast run on the zero and the remaining oil diets.
  26. Rand, N. T., H. M. Scott, and F. A. Kummerow. 1958. Dietary fat in the nutrition of the growing chick. Poult. Sci. 37:1075–1085.




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