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Relationships between dietary fatty acid composition and either melting point or fatty acid profile of adipose tissue in broilers
Meat Science 64 (2003) 133–140 www.elsevier.com/locate/meatsci
Relationships between dietary fatty acid composition and either melting point or fatty acid profile of adipose tissue in broilers F.J. Bavelaar*, A.C. Beynen Department of Nutrition, Faculty of Veterinary Medicine, University of Utrecht, PO Box 80152, 3508 TD Utrecht, The Netherlands Received 26 October 2001; received in revised form 30 March 2002; accepted 7 June 2002
Abstract Data on the fatty acid composition of the diet and that of the adipose tissue in broilers were collected from the literature. The linear regression between the dietary and the adipose tissue unsaturated to saturated fatty acids ratio (U/S ratio) was calculated because the U/S ratio of adipose tissue fat determines its melting point, which is an indicator of the consistency of poultry fat. For 54 data points from three different experiments, the linear correlation coefficient of the relationship between dietary and adipose tissue U/S ratio was 0.77. The regression equation for linoleic acid in adipose tissue as a function of dietary linoleic acid was calculated. The linoleic acid content of adipose tissue was expressed as weight percentage of total fatty acids. Intake was expressed as either weight percentage of total fatty acids or as energy percentage of total dietary metabolizable energy. The linear correlation coefficients were 0.68 and 0.78 as based on 116 or 91 data points from 15 or 12 different experiments. Significant correlations were also found for a-linolenic acid. The linoleic acid content of adipose tissue was found to be correlated (r=0.87) for 25 data points with that in consumable broiler meat, which may affect serum cholesterol concentrations in humans. With the help of the regression formulas presented it may be possible to formulate broiler diets in relation to consumer health and product quality. # 2002 Elsevier Science Ltd. All rights reserved. Keywords: Broilers; Fatty acids; Diet; Adipose tissue
1. Introduction The quality of poultry meat is a relative notion, but may be determined by its consistency and by its influence on consumer health. The consistency is related to the melting point of the fat component (Hrdinka, Zollitsch, Knaus, & Lettner, 1996), which is associated with its fatty acid composition (Elliot & Bowland, 1969; Hrdinka et al., 1996; Lea, Swoboda, & Gatherum, 1970; Sanz, Flores, & Lopez-Bote, 1999). An increase in the percentage of unsaturated fatty acids causes a decrease in the firmness and an increase in the oiliness of poultry meat (Miller, Shackelford, Hayden, & Reagan, 1990). Increasing the hardness of the tissue fat can be advantageous in the marketing of broiler meat (Valencia, Watkins, Waldroup, & Waldroup, 1993). In man, a high consumption of saturated fatty acids causes high serum cholesterol concentrations, which are associated with an increased risk for coronary heart
disease (Consensus Conference, 1985; Grundy et al., 1982). Beynen (1984) calculated that eating poultry meat instead of red meat and pork can lead to a small decrease in serum cholesterol. The advantageous influence of poultry meat is related to its relatively high content of polyunsaturated fatty acids. The intake of polyunsaturated versus saturated fatty acids causes a lowering of serum cholesterol concentrations (Grundy et al., 1982). Thus, the fatty acid composition of poultry meat can be considered an important determinant of its quality. The objective of this study was to establish relationships between the dietary fatty acid composition and either the melting point or the fatty acid composition of adipose tissue in broilers.
2. Materials and methods 2.1. Data collection
* Corresponding author. Tel.: +31-6-22080045; fax: +31-302534152. E-mail address: [email protected] (F.J. Bavelaar).
The literature used was collected with the help of Medline (keywords: broiler(s) and fatty acid composition) and
0309-1740/03/$ - see front matter # 2002 Elsevier Science Ltd. All rights reserved. PII: S0309-1740(02)00167-5
134
F.J. Bavelaar, A.C. Beynen / Meat Science 64 (2003) 133–140
through references given by the literature found. The data used (Table 1) were restricted to broilers and the fatty acid composition of their diet and adipose tissue. The ratio of unsaturated to saturated fatty acids (U/S ratio), the dietary metabolizable energy (ME), and the dietary levels of linoleic (C18:2 n-6) and a-linolenic acid (C18:3 n-3) were calculated as follows. The unsaturated fraction (U) was the sum of C16:1, C18:1, C18:2 and C18:3, and the saturated fraction (S) that of C14:0, C16:0 and C18:0. To enhance comparability of the diets used in the various studies, the ME contents were calculated using the reported ingredient composition of the diets. The ME of the individual feedstuffs was calculated with the following formula (CVB, 1999). ME ingredient ¼ ½ððGE-CP DC-CP 5:2Þ CPÞ þðGE-CFDC-CFCFÞ þ ðGE-CHO DC-CHO CHOÞ=1000 where ME=metabolizable energy (MJ/kg), GE=gross energy (kJ/g), DC=digestibility coefficient (%/100), CP=crude protein (g/kg), CF=crude fat (g/kg) and CHO=carbohydrates (g/kg). The GE contents of CP, CF and CHO were taken to be 23.8, 39 and 17 kJ/g, respectively. The amount of linoleic and a-linolenic acid in the diet or the adipose tissue is expressed as weight percentage of total fatty acids (TFA). The amount of the two fatty acids in the diet is also given as energy percentage of total dietary ME (TME). For the fatty acids the ME content of crude fat was assumed. The data used for the ME calculations were taken from the Dutch Feedstuff Table 1999 (CVB) and the USDA nutrient database (www.nal.usda.gov/fnic/foodcomp). When the relative percentage of fatty acids in the whole diet was not given
in the published articles, but rather their absolute amounts, it was assumed that the fat contained 95% of its weight in the form of fatty acids. In the articles of Valencia et al. (1993), Waldroup and Adams (1995) and Yau, Denton, Bailey, & Sams (1991), the amounts of dietary linoleic and a-linolenic acid had not been given and therefore they were calculated on the basis of the fatty acid composition of the diet ingredients (CVB, USDA). 2.2. Statistical analysis The linear regression equations were calculated with the following statistical model. Y=a+bX, where Y=adipose tissue fatty acid (weight% TFA) and X=dietary fatty acid (weight % TFA or % TME). The calculations have been made with the statistical computer programme SPSS. Group mean values for adipose tissue fatty acids were used as they reflect the best estimate of diet-induced values. No corrections were made for the number of animals represented by each value.
3. Results and discussion The available data on fatty acid composition of the diet and that of consumable broiler meat were used to construct Figs. 1 and 2. It is clear that the fatty acid composition of the meat correlates well with that of the adipose tissue. Including the point on the right end of the scale, the linear correlation coefficients were 0.87 for linoleic acid and 0.98 for a-linolenic acid. Excluding the outlying points, the linear correlation coefficients were 0.65 and 0.95, respectively. Thus, the fatty acid composition of adipose tissue is an index of that of meat,
Table 1 Characteristics of the literature data used Author
Number of dietary treatments
Number of animals examined per treatment
Duration of treatment (days)
Age at slaughter (days)
Sex
Ajuyah et al., 1991 Hrdinka et al., 1996 Hulan et al., 1983, 1988 Kirchgessner et al., 1993 Pinchasov and Nir, 1992 Roth et al., 1993 Sanz, 2000 Sanz et al., 1999 Scaife et al., 1994 Sijben et al., 2002 Sklan and Ayal, 1989 Valencia et al., 1993 Veen and Stappers, 1975 Waldroup and Adams, 1995 Yau et al., 1991 Zollitsch et al., 1992
9 4 7 6 5 3 2 3 10 12 4 24 4 19 3 4
15 16 6 14 18 26 30 8 M, 8 F 6 12 10 8 5 40 13 16
42 42 49 42 19 35 28 31 35 63 28 42 49 42 49 41
42 42 49 42 40 35 49 52 54 63 49 42 49 42 49 41
M M/F M/F M/F M M/F F M, F F F M/F M M M M M/F
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Fig. 1. The relationship between the amount of linoleic acid in adipose tissue and that in breast muscle of broilers.
Fig. 2. The relationship between the amount of a-linolenic acid in adipose tissue and that in breast muscle of broilers. Table 2 The regression formulas for the relation between dietary and adipose tissue fatty acids and that between dietary fatty acids and slippoint of adipose tissue fat Y
X
Slippoint ( C) Adipose U/S ratio Adipose C18:2 (% TFA) Adipose C18:2 (% TFA) Adipose C18:3 (% TFA) Adipose C18:3 (% TFA)
Dietary U/S ratio Dietary U/S ratio Dietary C18:2 (% TFA) Dietary C18:2 (% TME) Dietary C18:3 (% TFA) Dietary C18:3 (% TME)
Number Data points
Experiments
15 54 116 91 112 91
4 3 15 12 13 10
R2
Intercept SE/P-value
Slope SE/P-value
0.61 0.60 0.47 0.61 0.94 0.91
33.25 2.24/P <0.000 1.18 0.18/P <0.000 1.99 2.36/P=0.402 5.84 1.38/P <0.000 0.46 0.06/P <0.000 0.66 0.09/P <0.000
2.75 0.62/P=0.001 0.40 0.05/P<0.000 0.65 0.07/P<0.000 2.31 0.20/P<0.000 0.46 0.01/P<0.000 2.15 0.07/P<0.000
U/S ratio=ratio of unsaturated to saturated fatty acids; TFA=total fatty acids; TME=total metabolizable energy.
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which influences consumer health rather than the composition of adipose tissue. Animal fat consists of a mixture of triglycerides so that it softens or hardens over a wide temperature
range. There is no true melting point, and instead slippoint is usually used. The slippoint is defined as the temperature at which the fat is sufficiently soft to flow into a capillary tube (Enser, 1984). There was a negative
Fig. 3. The relationship between dietary U/S ratio and slippoint of adipose tissue fat.
Fig 4. The relationship between dietary and adipose tissue U/S ratio in broilers.
F.J. Bavelaar, A.C. Beynen / Meat Science 64 (2003) 133–140
linear correlation (r=0.78, Table 2) between the slippoint and the dietary U/S ratio (Fig. 3). The adipose U/ S ratio was strongly influenced by the dietary U/S ratio (Fig. 4), the linear correlation coefficient being 0.77 (Table 2). Thus, the dietary U/S ratio determines the adipose U/S ratio that, in turn, determines the slippoint.
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For 116 data points from 15 different studies, the relationship between dietary and adipose tissue linoleic acid (Fig. 5) had a linear correlation coefficient of 0.69 (Table 2). The correlation coefficient within single studies was about 0.90 (Hrdinka et al., 1996; Sanz, 2000; Scaife, Moyo, Galbraith, Michie, & Campbell, 1994).
Fig. 5. The relationship between the relative percentages of dietary and adipose tissue linoleic acid in broilers.
Fig. 6. The relationship between the energy percentage of dietary linoleic acid and its weight percentage in adipose tissue of broilers.
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High correlations have also been found in other animal species and humans. Beynen, Hermus, and Hautvast (1980) collected information from seven different experiments with human subjects and calculated a correlation coefficient of 0.80. Van Niel and Beynen (1997) found a correlation coefficient of 0.99 in kittens. Lin, Connor, and Spenler (1993) calculated a value of 0.99 in rabbits, and Veen (1972) reported a correlation coefficient of 0.90 for
the relationship of dietary and adipose tissue linoleic acid in veal calves. The correlations for other animal species and those for broilers within studies are stronger than that found in this study. We used data from 15 different experiments, which leads to an increase in the variation and therefore a decrease in the correlation coefficient. The relationship between the dietary and the adipose tissue linoleic acid content is expected to be influenced
Fig. 7. The relationship between the relative percentages of dietary and adipose tissue a-linolenic acid in broilers.
Fig. 8. The relationship between the energy percentage of dietary a-linolenic acid and its weight percentage in adipose tissue of broilers.
F.J. Bavelaar, A.C. Beynen / Meat Science 64 (2003) 133–140
by fat intake. At low intakes of fat, the dietary linoleic acid will be relatively more diluted by de novo synthesized fatty acids than at high intakes (Beynen et al., 1980). To take into account the phenomenon of dilution, we also calculated dietary linoleic acid as energy percentage of ME. For the relationship (Fig. 6) between the energy percentage of linoleic acid and its weight percentage in adipose tissue a linear correlation coefficient of 0.78 was calculated (Table 2). The stronger correlation for dietary linoleic acid expressed as energy percentage instead as percentage of total dietary fatty acids supports the idea that incorporation of linoleic acid into adipose tissue is affected by de novo synthesis of fatty acids. For a-linolenic acid the correlation coefficients of the relationships (Figs. 7 and 8) between intake and adipose tissue content appeared to be independent of the unit of intake (Table 2). However, the correlations were strongly influenced by the two extreme values on the right side of the scale. The slope of the regression line for dietary linoleic acid as weight percentage and adipose tissue linoleic acid was 0.65 (Table 2). Within studies, Hrdinka et al. (1996) found a slope of 0.74 in broilers, Katan et al. (1986) reported values in men ranging from 0.9 to 1.2, Veen (1972) published data for veal calves yielding a regression coefficient of 1.0, and Van Niel et al. (1997) found a slope of 0.87 in cats. Thus, ingested linoleic acid is efficiently incorporated into adipose tissue of various monogastric species. The slope for a-linolenic acid as weight percentage of total dietary fatty acids was less steep than that for linoleic acid (Table 2), indicating that linoleic acid is more efficiently stored in adipose tissue. In conclusion, the fatty acid composition and slippoint of adipose tissue fat are strongly determined by the qualitative fatty acid intake. The regression formulas presented here can be used to formulate diets to modify broiler meat with regard to consumer health and product quality.
References Ajuhay, A. O., Lee, K. H., Hardin, R. T., & Sim, J. S. (1991). Changes in the yield and in the fatty acid composition of whole carcass and selected meat portions of broiler chickens fed full-fat oil seeds. Poultry Science, 70, 2304–2314. Beynen, A. C. (1984). Rabbit: a source of healthful meat? Journal of Applied Rabbit Research, 7, 133–134. Beynen, A. C., Hermus, R. J. J., & Hautvast, J. G. A. J. (1980). A mathematical relationship between the fatty acid composition of the diet and that of the adipose tissue in man. American Journal of Clinical Nutrition, 33, 81–85. Consensus Conference. (1985). Lowering blood cholesterol to prevent heart disease. JAMA,253, 2080–2086. CVB. (1999). Veevoedertabel. Lelystad: Centraal Veevoeder Bureau. Elliot, J. I., & Bowland, J. P. (1969). Correlation of melting point with the sum of the unsaturated fatty acids in samples of porcine depot fat. Canadian Journal of Animal Science, 49, 397–398.
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Enser, M. (1984). The chemistry, biochemistry and nutritional importance of animal fats. In Wiseman (Ed.), Fats in animal nutrition, pp. 23–49. Grundy, S. M., Bilheimer, D., Blackburn, H., Brown, W. V., Kwiterovich, P. O., Mattson, F., Schonfeld, G., & Weidman, W. H. (1982). Rationale of the Diet-Heart Statement of the American Heart Association: report of the nutrition committee. Circulation, 65, 839 A-851A. Hrdinka, C., Zollitsch, W., Knaus, W., & Lettner, F. (1996). Effects of dietary fatty acid pattern on melting point and composition of adipose tissue and intramuscular fat of broiler. Poultry Science, 75, 208–215. Hulan, H. W., Ackman, R. G., Ratnayake, W. N., & Proudfood, F. G. (1988). Omega-3 fatty acid levels and performance of broiler chickens fed redfish meal or redfish oil. Canadian Journal of Animal Science, 68, 533–547. Hulan, H. W., Proudfood, F. G., & Nash, D. M. (1983). The effects of different fat sources on general performance and carcass fatty acid composition of broiler chickens. Poultry Science, 63, 324–332. Katan, M. B., Van Staveren, W. A., Deurenberg, P., Barendse-Van Leeuwen, J., Germing-Nouwen, C., Soffers, A., Berkel, J., & Beynen, A. C. (1986). Linoleic and trans-unsaturated fatty acid content of adipose tissue biopsies as objective indicators of the dietary habits of individuals. Progress in Lipid Research, 25, 193–195. Kirchgessner, M., Ristic, M., Kreuzer, M., & Roth, F. X. (1993). Einsatz von Fetten mit hohen Anteil an freien Fettsa¨uren in der Broilermast. Arch. Geflu¨gelk, 57, 265–274. Lea, C. H., Swoboda, P. A. T., & Gatherum, D. P. (1970). A chemical study of soft fat in cross-bred pigs. Journal of Agricultural Science, 74, 279–289. Lin, D. S., Connor, W. E., & Spenler, C. W. (1993). Are dietary saturated, monounsaturated and polyunsaturated fatty acids deposited to the same extent in adipose tissue of rabbit? . American Journal of Clinical Nutrition, 58, 174–179. Miller, M. F., Shackelford, S. D., Hayden, K. D., & Reagan, J. O. (1990). Determination of the alteration in fatty acid profiles, sensory characteristics and carcass traits of swine fed elevated levels of monounsatureated fats in the diet. Journal of Animal Science, 68, 1624–1631. Pinchasov, Y., & Nir, I. (1992). Effect of dieraty polyunsaturated fatty acid composition in broiler chickens. Poultry Science, 71, 1504– 1512. Roth, F. X., Ristic, M., Kreuzer, M., & Kirchgessner, M. (1993). Einsatz von Fetten mit hohen Anteilen an freien Fettsa¨uren in der Broilermast. Arch. Geflu¨gelk, 57, 256–264. Sanz, M. (2000). Effect of dietary fat saturation on the quantity and quality of fat in broiler chickens. Universidad Politecnica de Madrid, pp. 217–238. Sanz, M., Flores, A., & Lopez-Bote, C. J. (1999). Effect of fatty acid saturation in broiler diets on abdominal fat and breast muscle fatty acid composition and susceptibility to lipid oxidation. Poultry Science, 78, 378–382. Scaife, J. R., Moyo, J., Galbraith, H., Michie, W., & Campbell, V. (1994). Effect of different supplemental fats and oils on the fatty acid composition and growth of female broilers. Br. Poultry Science, 35, 107–118. Sijben, J. W. C., Schrama, J. W., Nieuwland, M. G. B., Hovenier, R., Beynen, A. C., Verstegen, M. W. A., & Parmentier, H. K. (2002). Interaction of dietary polyunsaturated fatty acids and vitamin E with regard to vitamin E status, fat composition and antibody responsiveness in layer hens. Br. Poultry Science 43, 297–305. Sklan, D., & Ayal, A. (1989). Effect of saturated fat on growth, body fat composition and carcass quality in chicks. Br. Poultry Science, 30, 407–411. Valencia, M. E., Watkins, S. E., Waldroup, A. L., & Waldroup, P. W. (1993). Utilization of crude and refined palm and palm kernel oils in broiler diets. Poultry Science, 72, 2200–2215.
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Van Niel, M. H. F. a. B., & Beynen, A. C. (1997). The intake of polyunsaturated fatty acids by cats is reflected in their adipose tissue. Vetinery Quarterly, 19, 150–153. Veen, W. A. G. (1972). Animal and vegetable fats in milk replacers for veal calves. Z. Tierphysiol. Tierernarh. und Futtermittelkunde, 30, 1–19. Veen, W. A. G., & Stappers, H. P. (1975). Der einfluss verschiedener fette in futtermitteln auf die zusammensetzung und den geschmack des fleisches van slachtgefluegel. Fleischwirtssch, 55, 1098–1101.
Waldroup, P. W., & Adams, H. (1995). Utilization of hydrolyzed sucrose polyester (olestra) in broiler diets. Poultry Science, 74, 957– 967. Yau, J. C., Denton, J. H., Bailey, C. A., & Sams, A. R. (1991). Customizing the fatty acid content of broiler tissues. Poultry Science, 70, 167–172. Zollitsch, W., Wetscherek, W., & Lettner, F. (1992). Einsatz von Rapso¨l im Hu¨hnermastfutter. Arch. Geflu¨gelk, 56, 182–186.
Relationships between dietary fatty acid composition and either melting point or fatty acid profile of adipose tissue in broilers F.J. Bavelaar*, A.C. Beynen Department of Nutrition, Faculty of Veterinary Medicine, University of Utrecht, PO Box 80152, 3508 TD Utrecht, The Netherlands Received 26 October 2001; received in revised form 30 March 2002; accepted 7 June 2002
Abstract Data on the fatty acid composition of the diet and that of the adipose tissue in broilers were collected from the literature. The linear regression between the dietary and the adipose tissue unsaturated to saturated fatty acids ratio (U/S ratio) was calculated because the U/S ratio of adipose tissue fat determines its melting point, which is an indicator of the consistency of poultry fat. For 54 data points from three different experiments, the linear correlation coefficient of the relationship between dietary and adipose tissue U/S ratio was 0.77. The regression equation for linoleic acid in adipose tissue as a function of dietary linoleic acid was calculated. The linoleic acid content of adipose tissue was expressed as weight percentage of total fatty acids. Intake was expressed as either weight percentage of total fatty acids or as energy percentage of total dietary metabolizable energy. The linear correlation coefficients were 0.68 and 0.78 as based on 116 or 91 data points from 15 or 12 different experiments. Significant correlations were also found for a-linolenic acid. The linoleic acid content of adipose tissue was found to be correlated (r=0.87) for 25 data points with that in consumable broiler meat, which may affect serum cholesterol concentrations in humans. With the help of the regression formulas presented it may be possible to formulate broiler diets in relation to consumer health and product quality. # 2002 Elsevier Science Ltd. All rights reserved. Keywords: Broilers; Fatty acids; Diet; Adipose tissue
1. Introduction The quality of poultry meat is a relative notion, but may be determined by its consistency and by its influence on consumer health. The consistency is related to the melting point of the fat component (Hrdinka, Zollitsch, Knaus, & Lettner, 1996), which is associated with its fatty acid composition (Elliot & Bowland, 1969; Hrdinka et al., 1996; Lea, Swoboda, & Gatherum, 1970; Sanz, Flores, & Lopez-Bote, 1999). An increase in the percentage of unsaturated fatty acids causes a decrease in the firmness and an increase in the oiliness of poultry meat (Miller, Shackelford, Hayden, & Reagan, 1990). Increasing the hardness of the tissue fat can be advantageous in the marketing of broiler meat (Valencia, Watkins, Waldroup, & Waldroup, 1993). In man, a high consumption of saturated fatty acids causes high serum cholesterol concentrations, which are associated with an increased risk for coronary heart
disease (Consensus Conference, 1985; Grundy et al., 1982). Beynen (1984) calculated that eating poultry meat instead of red meat and pork can lead to a small decrease in serum cholesterol. The advantageous influence of poultry meat is related to its relatively high content of polyunsaturated fatty acids. The intake of polyunsaturated versus saturated fatty acids causes a lowering of serum cholesterol concentrations (Grundy et al., 1982). Thus, the fatty acid composition of poultry meat can be considered an important determinant of its quality. The objective of this study was to establish relationships between the dietary fatty acid composition and either the melting point or the fatty acid composition of adipose tissue in broilers.
2. Materials and methods 2.1. Data collection
* Corresponding author. Tel.: +31-6-22080045; fax: +31-302534152. E-mail address: [email protected] (F.J. Bavelaar).
The literature used was collected with the help of Medline (keywords: broiler(s) and fatty acid composition) and
0309-1740/03/$ - see front matter # 2002 Elsevier Science Ltd. All rights reserved. PII: S0309-1740(02)00167-5
134
F.J. Bavelaar, A.C. Beynen / Meat Science 64 (2003) 133–140
through references given by the literature found. The data used (Table 1) were restricted to broilers and the fatty acid composition of their diet and adipose tissue. The ratio of unsaturated to saturated fatty acids (U/S ratio), the dietary metabolizable energy (ME), and the dietary levels of linoleic (C18:2 n-6) and a-linolenic acid (C18:3 n-3) were calculated as follows. The unsaturated fraction (U) was the sum of C16:1, C18:1, C18:2 and C18:3, and the saturated fraction (S) that of C14:0, C16:0 and C18:0. To enhance comparability of the diets used in the various studies, the ME contents were calculated using the reported ingredient composition of the diets. The ME of the individual feedstuffs was calculated with the following formula (CVB, 1999). ME ingredient ¼ ½ððGE-CP DC-CP 5:2Þ CPÞ þðGE-CFDC-CFCFÞ þ ðGE-CHO DC-CHO CHOÞ=1000 where ME=metabolizable energy (MJ/kg), GE=gross energy (kJ/g), DC=digestibility coefficient (%/100), CP=crude protein (g/kg), CF=crude fat (g/kg) and CHO=carbohydrates (g/kg). The GE contents of CP, CF and CHO were taken to be 23.8, 39 and 17 kJ/g, respectively. The amount of linoleic and a-linolenic acid in the diet or the adipose tissue is expressed as weight percentage of total fatty acids (TFA). The amount of the two fatty acids in the diet is also given as energy percentage of total dietary ME (TME). For the fatty acids the ME content of crude fat was assumed. The data used for the ME calculations were taken from the Dutch Feedstuff Table 1999 (CVB) and the USDA nutrient database (www.nal.usda.gov/fnic/foodcomp). When the relative percentage of fatty acids in the whole diet was not given
in the published articles, but rather their absolute amounts, it was assumed that the fat contained 95% of its weight in the form of fatty acids. In the articles of Valencia et al. (1993), Waldroup and Adams (1995) and Yau, Denton, Bailey, & Sams (1991), the amounts of dietary linoleic and a-linolenic acid had not been given and therefore they were calculated on the basis of the fatty acid composition of the diet ingredients (CVB, USDA). 2.2. Statistical analysis The linear regression equations were calculated with the following statistical model. Y=a+bX, where Y=adipose tissue fatty acid (weight% TFA) and X=dietary fatty acid (weight % TFA or % TME). The calculations have been made with the statistical computer programme SPSS. Group mean values for adipose tissue fatty acids were used as they reflect the best estimate of diet-induced values. No corrections were made for the number of animals represented by each value.
3. Results and discussion The available data on fatty acid composition of the diet and that of consumable broiler meat were used to construct Figs. 1 and 2. It is clear that the fatty acid composition of the meat correlates well with that of the adipose tissue. Including the point on the right end of the scale, the linear correlation coefficients were 0.87 for linoleic acid and 0.98 for a-linolenic acid. Excluding the outlying points, the linear correlation coefficients were 0.65 and 0.95, respectively. Thus, the fatty acid composition of adipose tissue is an index of that of meat,
Table 1 Characteristics of the literature data used Author
Number of dietary treatments
Number of animals examined per treatment
Duration of treatment (days)
Age at slaughter (days)
Sex
Ajuyah et al., 1991 Hrdinka et al., 1996 Hulan et al., 1983, 1988 Kirchgessner et al., 1993 Pinchasov and Nir, 1992 Roth et al., 1993 Sanz, 2000 Sanz et al., 1999 Scaife et al., 1994 Sijben et al., 2002 Sklan and Ayal, 1989 Valencia et al., 1993 Veen and Stappers, 1975 Waldroup and Adams, 1995 Yau et al., 1991 Zollitsch et al., 1992
9 4 7 6 5 3 2 3 10 12 4 24 4 19 3 4
15 16 6 14 18 26 30 8 M, 8 F 6 12 10 8 5 40 13 16
42 42 49 42 19 35 28 31 35 63 28 42 49 42 49 41
42 42 49 42 40 35 49 52 54 63 49 42 49 42 49 41
M M/F M/F M/F M M/F F M, F F F M/F M M M M M/F
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F.J. Bavelaar, A.C. Beynen / Meat Science 64 (2003) 133–140
Fig. 1. The relationship between the amount of linoleic acid in adipose tissue and that in breast muscle of broilers.
Fig. 2. The relationship between the amount of a-linolenic acid in adipose tissue and that in breast muscle of broilers. Table 2 The regression formulas for the relation between dietary and adipose tissue fatty acids and that between dietary fatty acids and slippoint of adipose tissue fat Y
X
Slippoint ( C) Adipose U/S ratio Adipose C18:2 (% TFA) Adipose C18:2 (% TFA) Adipose C18:3 (% TFA) Adipose C18:3 (% TFA)
Dietary U/S ratio Dietary U/S ratio Dietary C18:2 (% TFA) Dietary C18:2 (% TME) Dietary C18:3 (% TFA) Dietary C18:3 (% TME)
Number Data points
Experiments
15 54 116 91 112 91
4 3 15 12 13 10
R2
Intercept SE/P-value
Slope SE/P-value
0.61 0.60 0.47 0.61 0.94 0.91
33.25 2.24/P <0.000 1.18 0.18/P <0.000 1.99 2.36/P=0.402 5.84 1.38/P <0.000 0.46 0.06/P <0.000 0.66 0.09/P <0.000
2.75 0.62/P=0.001 0.40 0.05/P<0.000 0.65 0.07/P<0.000 2.31 0.20/P<0.000 0.46 0.01/P<0.000 2.15 0.07/P<0.000
U/S ratio=ratio of unsaturated to saturated fatty acids; TFA=total fatty acids; TME=total metabolizable energy.
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F.J. Bavelaar, A.C. Beynen / Meat Science 64 (2003) 133–140
which influences consumer health rather than the composition of adipose tissue. Animal fat consists of a mixture of triglycerides so that it softens or hardens over a wide temperature
range. There is no true melting point, and instead slippoint is usually used. The slippoint is defined as the temperature at which the fat is sufficiently soft to flow into a capillary tube (Enser, 1984). There was a negative
Fig. 3. The relationship between dietary U/S ratio and slippoint of adipose tissue fat.
Fig 4. The relationship between dietary and adipose tissue U/S ratio in broilers.
F.J. Bavelaar, A.C. Beynen / Meat Science 64 (2003) 133–140
linear correlation (r=0.78, Table 2) between the slippoint and the dietary U/S ratio (Fig. 3). The adipose U/ S ratio was strongly influenced by the dietary U/S ratio (Fig. 4), the linear correlation coefficient being 0.77 (Table 2). Thus, the dietary U/S ratio determines the adipose U/S ratio that, in turn, determines the slippoint.
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For 116 data points from 15 different studies, the relationship between dietary and adipose tissue linoleic acid (Fig. 5) had a linear correlation coefficient of 0.69 (Table 2). The correlation coefficient within single studies was about 0.90 (Hrdinka et al., 1996; Sanz, 2000; Scaife, Moyo, Galbraith, Michie, & Campbell, 1994).
Fig. 5. The relationship between the relative percentages of dietary and adipose tissue linoleic acid in broilers.
Fig. 6. The relationship between the energy percentage of dietary linoleic acid and its weight percentage in adipose tissue of broilers.
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High correlations have also been found in other animal species and humans. Beynen, Hermus, and Hautvast (1980) collected information from seven different experiments with human subjects and calculated a correlation coefficient of 0.80. Van Niel and Beynen (1997) found a correlation coefficient of 0.99 in kittens. Lin, Connor, and Spenler (1993) calculated a value of 0.99 in rabbits, and Veen (1972) reported a correlation coefficient of 0.90 for
the relationship of dietary and adipose tissue linoleic acid in veal calves. The correlations for other animal species and those for broilers within studies are stronger than that found in this study. We used data from 15 different experiments, which leads to an increase in the variation and therefore a decrease in the correlation coefficient. The relationship between the dietary and the adipose tissue linoleic acid content is expected to be influenced
Fig. 7. The relationship between the relative percentages of dietary and adipose tissue a-linolenic acid in broilers.
Fig. 8. The relationship between the energy percentage of dietary a-linolenic acid and its weight percentage in adipose tissue of broilers.
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by fat intake. At low intakes of fat, the dietary linoleic acid will be relatively more diluted by de novo synthesized fatty acids than at high intakes (Beynen et al., 1980). To take into account the phenomenon of dilution, we also calculated dietary linoleic acid as energy percentage of ME. For the relationship (Fig. 6) between the energy percentage of linoleic acid and its weight percentage in adipose tissue a linear correlation coefficient of 0.78 was calculated (Table 2). The stronger correlation for dietary linoleic acid expressed as energy percentage instead as percentage of total dietary fatty acids supports the idea that incorporation of linoleic acid into adipose tissue is affected by de novo synthesis of fatty acids. For a-linolenic acid the correlation coefficients of the relationships (Figs. 7 and 8) between intake and adipose tissue content appeared to be independent of the unit of intake (Table 2). However, the correlations were strongly influenced by the two extreme values on the right side of the scale. The slope of the regression line for dietary linoleic acid as weight percentage and adipose tissue linoleic acid was 0.65 (Table 2). Within studies, Hrdinka et al. (1996) found a slope of 0.74 in broilers, Katan et al. (1986) reported values in men ranging from 0.9 to 1.2, Veen (1972) published data for veal calves yielding a regression coefficient of 1.0, and Van Niel et al. (1997) found a slope of 0.87 in cats. Thus, ingested linoleic acid is efficiently incorporated into adipose tissue of various monogastric species. The slope for a-linolenic acid as weight percentage of total dietary fatty acids was less steep than that for linoleic acid (Table 2), indicating that linoleic acid is more efficiently stored in adipose tissue. In conclusion, the fatty acid composition and slippoint of adipose tissue fat are strongly determined by the qualitative fatty acid intake. The regression formulas presented here can be used to formulate diets to modify broiler meat with regard to consumer health and product quality.
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