THE ESSENTIAL FATTY ACID REQUIREMENTS OF BROILERS 1

Transcription

1 2001 Poultry Science Association, Inc. THE ESSENTIAL FATTY ACID REQUIREMENTS OF BROILERS 1 W. O. ZORNIG, G. M. PESTI 2, and R. I. BAKALLI Department of Poultry Science The University of Georgia Athens, GA Phone: (706) FAX: (706) gpesti@arches.uga.edu Primary Audience: Nutritionists, Researchers SUMMARY Three experiments were conducted to find a basal diet capable of producing an essential fatty acid deficiency. A diet based on soybean meal and fish meal contained only 0.18% linoleic acid yet produced excellent growth, comparable to a corn and soybean meal-based diet with 2.20% linoleic acid. In two other trials, purified diets with 0.39 or 0.40% linoleic acid did not cause linoleic acid deficiencies when fed for 18 or 21 days. Based on these findings and other published results, it is concluded that the linoleic acid requirement of starting broilers is below 0.20% of the diet. Key words: Broilers, essential fatty acids, linoleic acid DESCRIPTION OF PROBLEM The linoleic acid requirement of chickens has been estimated to be 1% of the diet [1, 2], based on liver triene-to-tetraene ratios [2, 3]. While the triene-to-tetraene ratio changes markedly at about 1% of the diet, giving a clear break point [3, 4], it has never been related to any indication of animal performance such as growth, feed efficiency, gross carcass composition, or livability. Thus, there seems to be no justification for using the triene-to-tetraene ratio as an indication of the linoleic acid requirement of commercial broilers. In the studies used to estimate the broilers linoleic acid requirement at 1% [2], several authors added linoleic acid alone or as part of a naturally occurring oil, thus confounding the 2001 J. Appl. Poultry Res. 10:41 45 effects of linoleic acid supplementation with total fat and total calories [5, 6, 7, 8, 9, 10, 11, 12, 13]; others fed only large increments and so couldn t distinguish requirement levels well (e.g., 0.15 vs. 1.5% linoleic acid) [7, 8, 9, 10, 11, 12, 13]. Some trials were conducted with a fat high in linoleic acid replacing one low in linoleic acid, thus holding total fat and total calories constant among treatments [8, 9, 14]: a diet with 2% menhaden oil with 0.076% linoleic acid gave very good growth, equivalent to 2% safflower oil with 1.52% linoleic acid and better than the same diet with 1% safflower oil and 0.76% linoleic acid [8]; a diet with 4% menhaden oil containing 0.06% linoleic acid gave very good growth, equivalent to 4% corn oil with 2.4% linoleic acid [9]; when safflower oil 1 Supported by State and Hatch funds allocated to the Georgia Agricultural Stations of The University of Georgia 2 To whom correspondence should be addressed

2 42 JAPR: Research Report was substituted for olive oil without altering total fat or calories, maximum gains were achieved with 0.16% linoleic acid in one experiment [14]. In trials supporting 1% as the linoleic acid requirement based on the trieneto-tetraene ratio, very near maximum growth rates were achieved with 0.10 to 0.20% linoleic acid [4]. The experiments described herein were conducted to find a basal diet capable of producing an essential fatty acid deficiency, which would indicate the broiler chick s requirement for dietary linoleic acid. MATERIALS AND METHODS Three experiments were conducted with male Ross Ross 208 chicks obtained from a local hatchery [15]. Four pens (Petersime bat- TABLE 1. Composition of the experimental diets tery brooders) of eight chicks each were assigned to each treatment in Experiment 1, two pens of eight chicks each in Experiments 2 and 3. The experimental diets (Table 1) and water were available on an ad libitum basis. Safflower oil (Experiment 1) or corn oil (Experiments 2 and 3) was substituted for coconut oil on a weight:weight basis to achieve different levels of linoleic acid (Tables 2, 3, 4). Additional Solka floc was added when total oil levels were below 2%. At the end of Experiment 1 (21 days) and Experiment 2 (18 days), birds and residual feed were weighed, and three chicks per pen were killed by carbon dioxide asphyxiation. Liver and breast muscle samples were removed for lipid content analysis [16]. Fatty acid profiles of the feed ingredients were determined by gas liquid chromatography [17]. The experimental unit was the pen mean. Data were ana- EXPERIMENT INGREDIENTS 1 1 2, 3 CONTROL (%) Dextrose Ground corn Soybean meal (48% protein) Isolated soybean protein Menhaden meal Poultry by-product meal 3.00 Casein Solka floc Coconut oil Poultry oil 3.15 Limestone Dicalcium phosphate Defluorinated phosphate 0.72 NaCl Magnesium sulfate 0.60 Potassium sulfate 1.00 DL-methionine Choline Cl-70% 0.10 Potassium chloride 0.10 Vitamin premix A Glycine 0.40 Mineral mix B Coban C 0.75 D BMD A Vitamin premix provides the following per kilogram: vitamin A, 5,500 IU from all trans-retinyl acetate, cholecalciferol, 1,100 IU; vitamin E, 11 IU from all rac-α-tocopherol acetate; riboflavin, 4.4 mg; Ca pantothenate, 12 mg; nicotinic acid, 44 mg; choline Cl, 220 mg; vitamin B 12, 6.6 µg; vitamin B 6, 2.2 mg; menadione, 1.1 mg (as MSBC); folic acid, 0.55 mg; d-biotin, 0.11 mg; thiamine, 1.1 mg (as thiamine mononitrate); ethoxyquin, 125 mg. B Trace mineral premix provides the following in milligrams per kilogram of diet: Mn, 60; Zn, 50; Fe, 30; Cu, 5; I, 1.5. C Eli Lilly and Co., Indianapolis, IN D Alpharma, Fort Lee, NJ

3 ZORNIG ET AL.: EFA FOR BROILERS 43 TABLE 2. Influence of level of dietary linoleic acid on growth, hatching to 21 days, feed conversion, mortality, and fat percentage of broiler chickens (Experiment 1) A FEED FAT (%) LINOLEIC WEIGHT CONVERSION MORTALITY BREAST BASAL DIET ACID (%) GAIN (g) (g/g) (%) LIVER MUSCLE Soy/casein ± 23 b 2.47 ± 0.26 a 6.3 ± ± ± 0.13 Soy/casein ± 19 b 2.05 ± 0.10 b 0.0 ± ± ± 0.07 Soy/fish meal ± 3 a 1.49 ± 0.02 c 3.1 ± ± ± 0.18 Soy/fish meal ± 16 a 1.47 ± 0.02 c 0.0 ± ± ± 0.17 Control ± 39 a 1.54 ± 0.04 c 0.0 ± ± ± 0.17 (corn + SBM) A Values represent the mean ± standard error of four pens per diet (8 birds per pen). a c Means within a column with no common superscript differ significantly (p 0.05). lyzed by one-way analysis of variance, and significant treatment effects were separated using Duncan s New Multiple Range Test [18]. RESULTS AND DISCUSSION Chicks fed the soybean meal, fish meal, and coconut oil diet with only 0.18% linoleic acid grew very well and had excellent feed conversion ratios in comparison to those fed diets supplemented with linoleic acid from safflower oil or the corn and soybean meal-based control diet (Table 2). Similarly, adding linoleic acid to the soybean meal, casein, and coconut oil diet was without beneficial effect except for feed efficiency. This indicates that the chicks requirement is above 0.15% with that purified basal diet, although how far above isn t known. Adding linoleic acid by substituting safflower oil for coconut oil was also without significant effect on mortality or the fat content of the liver or breast muscles. Very similar results were obtained in Experiments 2 and 3 (Tables 3 and 4). Unfortunately, we determined only after the experiments were conducted that the isolated soybean meal we received was manufactured to be used in infant formulas (had added lecithin) and contained 4.5% lipids and 1.55% linoleic acid. Nonetheless, the diets in Experiments 2 and 3 should have been deficient in linoleic acid. These experiments add evidence that the requirement is much lower than 1% of the diet [1, 2]. The results of Experiment 3 demonstrate how results of experiments for determining response to linoleic acid can be confusing. The response to adding corn oil (2% vs. 0.5%) could be interpreted as a response to linoleic acid. However, the observation that substituting 0.5% corn oil for 0.5% coconut oil was without TABLE 3. Influence of level of dietary linoleic acid on growth, hatching to 21 days, feed conversion, and mortality of broiler chickens (Experiment 2) A DIETARY FAT (%) SOURCE OF WEIGHT FEED LINOLEIC LINOLEIC GAIN CONVERSION MORTALITY BREAST ACID ACID (%) (g) (g/g) (%) LIVER MUSCLE 1% coconut oil ± 4 b 1.49 ± ± 0.0 a 4.92 ± 0.33 b 1.13 ± % coconut oil ± 37 b 1.53 ± ± 0.0 b 4.33 ± 0.26 b 1.31 ± % corn oil ± 14 b 1.45 ± ± 6.3 ab 7.56 ± 0.71 a 1.42 ± % corn oil ± 14 b 1.53 ± ± 0.0 a 6.58 ± 0.23 a 1.19 ± 0.19 Control ± 28 a 1.35 ± ± 0.0 b 4.91 ± 0.08 a 1.17 ± 0.02 (corn + SBM) A Values represent the mean ± standard error of two pens per diet (8 birds per pen). a,b Means within a column with no common superscript differ significantly (p 0.05).

4 44 JAPR: Research Report TABLE 4. Influence of level of dietary linoleic acid on growth, hatching to 21 days, feed conversion, and mortality of broiler chickens (Experiment 3) A DIETARY FEED SOURCE OF LINOLEIC WEIGHT CONVERSION MORTALITY LINOLEIC ACID ACID (%) GAIN (g) (g/g) (%) 0.5% coconut oil ± 9 b 1.45 ± 0.00 b 0.0 ± % coconut oil ± 20 b 1.32 ± 0.01 c 6.3 ± % corn oil ± 23 b 1.45 ± 0.02 b 6.3 ± 6.3 2% corn oil ± 18 b 1.36 ± 0.04 bc 0.0 ± 0.0 Control (corn + SBM) ± 12 a 1.59 ± 0.05 a 6.3 ± 6.3 A Values represent the mean ± standard error of two pens per diet (8 birds per pen). a,b Means within a column with no common superscript differ significantly (p 0.05). significant effect makes it clear that the improvement is due to fat level, not linoleic acid level. The original goal of this research-developing a diet to produce essential fatty acid deficiency in modern broiler chickens was not met. The requirement is much too low to produce a deficiency disease when using practical ingredients. It is important to recognize that the broiler s linoleic acid requirement really is very low (perhaps <0.20%). Recognizing that linoleic acid is not a problem in practical diet formulation will enable nutritionists to focus on dietary fat and energy levels, which are important. Various approaches can be taken when determining the broiler s linoleic acid requirements. When only a natural source of linoleic acid is fed, like corn oil or purified linoleate, fat and energy levels may be confounded with linoleic acid level; when fats high and low in linoleic acid are blended, the levels of other fatty acids also must change. The first approach results in higher linoleic acid requirements, near 1% of the diet. The second approach results in much lower requirements, less than 0.20% of the diet. Experiments 1, 2, 3 and others [8, 9, 14, 19] support the hypothesis that the linoleic acid requirement for the growth and feed conversion of broiler chicks is considerably below 1% of the diet. Clearly metabolic changes and tissue composition changes occur when less than 1% linoleic acid is fed [2, 3, 4, 5], as do changes in percentage liver fat, as observed in Experiment 2. However, the economically important parameters, body weight gain and feed conversion, are not affected unless dietary linoleic acid levels are below 0.2% of the diet. Any special circumstances that cause the linoleic acid requirement to be above even 0.2% of the diet for growth are not known. There is evidence that linoleic acid reserves in the chick can be important [11, 12] and affect growth rates, but those effects have never been measured. Given a practical diet with adequate linoleic acid, chicks fed as little as 0.01% linoleic acid and 2% methyl oleate performed as well as those fed 2% methyl linoleate [11]. CONCLUSIONS AND APPLICATIONS 1. Neither a review of the literature nor the experiments presented here support the hypothesis that chicks linoleic acid requirement for maximum performance is near 1% of the diet. 2. Studies from the 1960s and Experiment 1 show that excellent growth rates and feed conversion ratios can be achieved with 0.20% dietary linoleic acid if the diets contain adequate levels of total lipids and energy.

5 ZORNIG ET AL.: EFA FOR BROILERS 45 REFERENCES AND NOTES 1. National Research Council Nutrient requirements of poultry. 9th Rev. Edition. National Acadademy Press, Washington, DC. 2. Balnave, D Essential fatty acids in poultry nutrition. World s Poultry Sci. J. 26: Holman, R.T The ratio of trienoic:tetraenoic acids in tissue lipids as a measure of essential fatty acid requirement. J. Nutr. 70: Hill, E.G Effect of dietary linoleate on chick liver fatty acids: Dietary linoleate requirement. J. Nutrition 89: Ross, E., and L. Adamson Observations on the requirements of young chicks for dietary fat. J. Nutrition 74: Marion, J.E., H.M. Edwards, Jr., and J.C. Driggers Influence of diet on serum cholesterol in the chick. J. Nutrition 74: Machlin, L.J., and R.S. Gordon Effect of dietary fatty acids and cholesterol on growth and fatty acid composition of the chicken. J. Nutrition 75: Edwards, H.M., Jr., J.E. Marion, and J.C. Driggers Studies on fat and fatty acid requirements of poultry. Pages in: XIIth World s Poultry Congress Proceedings, Sydney, Australia. 9. Edwards, H.M., Jr., and J.E. Marion Influence of dietary menhaden oil on growth rate and tissue fatty acids of the chick. J. Nutr. 81: Hill, E.G., C.L. Silbernick, and E. McMeans Dietary linoleate and methionine in chicks. Poultry Sci. 46: Edwards, H.M., Jr Studies of essential fatty acid deficiency of the growing domestic cock. Poultry Sci. 46: Hopkins, D.T., and M.C. Nesheim The linoleic acid requirement of chicks. Poultry Sci. 46: Machlin, L.J., and R.S. Gordon, The requirement of the chicken for certain unsaturated fatty acids. Poultry Sci. 39:1271 (Abstr.). 14. Bieri, J.G., and E.L. Prival Linoleic acid requirement of the chick. J. Nutrition 90: Seaboard Farms, Athens, GA Folch, J., M. Lees, and G.H.S. Stanley A simple method for the isolation and purification of total lipids from animal tissues. J. Biol. Chem. 226: Nugara, D., and H.M. Edwards, Jr Changes in fatty acid composition of cockerel testes due to age and fat deficiency. J. Nutr. 100: SAS Institute SAS Users Guide: Statistics. Version Five Edition. SAS Institute, Inc., Cary, NC.