Effects of Ratios of Essential Amino Acids to Nonessential Amino Acids in Low Protein Diet on Nitrogen Excretion and Fat Deposition of Broiler Chicks

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1 Effects of Ratios of Essential Amino Acids to Nonessential Amino Acids in Low Protein Diet on Nitrogen Excretion and Fat Deposition of Broiler Chicks Makoto YAMAZAKI, Hitoshi MURAKAMI and Masaaki TAKEMASA National Institute of Animal Industry, Tsukuba Norin Kenkyu Danchi P. O. Box 5, Ibaraki-ken Two experiments were conducted to determine whether the ratios of essential amino acids (EAA) to non-essential amino acids (NEAA) in low protein diets affects the performance, nitrogen excretion and abdominal fat deposition of broiler chicks. Low crude protein (19% CP) diets with different ratios of EAA/NEAA (E/N) (0.85, 1.03 and 1.17 in experiment 1, 0.76, 0.99 and 1.29 in experiment 2), and control diets (0.96 in experiment 1, 1.04 in experiment 2, E/N ratio in 21% CP) were fed to 7-day-old chicks for 14 days. Body weight gain and feed efficiency of chicks fed the 1.17 (experiment 1), 0.99 and 1.29 E/N (experiment 2) diets were the same as those of chicks on the control diets. Excreted nitrogen expressed as percentages of nitrogen intake was lower for chicks fed higher E/N diets compared to the control diets in both experiments, and decrease with increasing E/N in experiment 2. Abdominal fat weight increased with feeding 19% CP diets, but in experiment 2, 0.99 and 1.29 E/N diet chicks showed essentially the same abdominal fat deposition as those on the control diet. It follows from the present results that 1.29 E/N ratios in 19% CP diets reduce nitrogen excretion (g/4 days) by 20% without lowering performance compared to the control diet, and prevents excess fat deposition by lowering dietary CP. (Jpn. Poult. Sci., 35:19-26, 1998) Key words: broilers, environment, essential amino acids, fat deposition, nitrogen excretion Introduction With the public becoming increasingly aware of the environment and factors affecting it, serious attention is being directed to eliminating, reducing, or controlling potential pollutants. It is thus essential to convert poultry excreta into a fertilizer nitrogen source, and to reduce the excreta from chickens through dietary techniques. Recently, much works have been conducted to reduce the dietary protein levels of poultry diets, by the use of several synthetic amino acids which are available commercially. PARR and SUMMERS (1991) fed a low protein, corn-soybean meal diet supplemented with crystalline amino acids to 7-day-old broilers for 2 weeks. Equivalent growth was achieved using EAA in a low protein diet, compared with conventional starter diets. It has previously been shown that crude protein (CP) in broiler diets can be reduced from 21 to 19% without lowering performance by the supplementation of crystalline amino acids during 1 to 3-weeks of age, while also Received March 17, 1997 Accepted July 25, 1997

2 20 Jpn. Poult. Sci., 35 (1) reducing nitrogen excretion by about 15% (YAMAZAKI et al. 1996). However, lowering dietary CP may lead to greater abdominal fat weight. Excess fat deposition in poultry is a serious problem in the poultry industry. The degree of fatness of broilers is influenced by nutritional and non-nutritional factors, and particularly the calorie to protein ratio. Decreasing this ratio generally prevents excessive deposition of fat (FRAPS, 1943, JACKSON et al. 1982). BEDFORD and SUMMERS (1985) noted that the proportion of carcass fat was decreased with an increase in EAA in the dietary protein, in 1 to 3-week-old broilers. This study was conducted to determine whether the ratio of EAA to NEAA in a low protein diet would have an effect on nitrogen excretion and abdominal fat deposition in broiler chicks. Materials and Methods Day-old male broiler chicks (Abor Acres) obtained from a local hatchery were used in two experiments. The chicks were housed in electrically heated battery cages and had free access to water and a commercial starter diet for 7 days. They were then divided into four groups according to body weight, each of which contained five replicates of two chicks. Experimental diets were fed from 7 to 21 days of age. All diets consisted mainly of corn and soybean meal and were isocaloric (3.1 kcal per g). In experiment 1, the ratios of E/N were 0.85, 1.03 and 1.17 in the 19% CF diet, and 0.96 in the 21% CP diet (Table 1). To the 0.85, 1.03 and 1.17 E/N diets, EAA were supplied at 85,100 and 108% of recommendations, and the 21% CP diet was EAA at the levels recommended by the Japanese Feeding Standard (JFS (1992)). In the 19% CP diets, L-glutamic acid in the 0.85 E/N diet was replaced by synthetic EAA to meet 100% or 108% of recommendations. In experiment 2, diet formulations were almost the same as in experiment 1, except for the 19% CP diets, which had more varied corn to soybean meal ratios to make wider E/N ratio. The 0.76, 0.99 and 1.29 E/N ratio diets were supplied all EAA at 80,100 and 120% of the recommendations of the JFS (1992). Lighting was provided 24 hours per day, and temperature was maintained between 25 and 28 Ž. The birds and feed remaining in each tray were weighed at 21 days of age to determine body weight gain and feed consumption during the experiments. Six birds were selected from each group to determine abdominal fat weight. From 14 to 18 days of age a nitrogen balance trial was conducted by the total collection procedure. Excreta were collected for 4 days, dried in an oven at 55 Ž and ground. Nitrogen content was measured by the macro Kjeldahl method. Data were analyzed using the General Linear Models procedure of SAS(R) with Duncan's multiple range test (SAS Institute, 1988). Results Experiment 1. Table 2 shows the performance of chicks in experiment 1. Body weight gain and feed efficiency of chicks fed the 1.17 E/N diet were similar to those of chicks fed the

3 1) YAMAZAKI et al.: Dietary Amino Acids and Nitrogen Excretion 21 Table 1. Composition of experimental diets (%) 1) See YAMAZAKI et al. (1996). 2) Minimum specification of amino acid as a percent of the requirements as listed by Japanese Feeding Standard for Poultry of broiler chicks from 0 to 3 weeks of age (1992). Table 2. Effect of dietary E/N ratio on performance of male broiler chicks from 7 to 21 days of age (Experiment 1)1) : Each treatment consists of 5 replicates of 2 birds per pen. a-c): Means within the same rows with no common superscript are significantly different (p <.05).

4 22 Jpn. Poult. Sci., 35 (1) control diet. The highest E/N diet was found to be superior to the lowest E/N diet for body weight gain and feed efficiency. The 19% CP diets significantly increased abdominal fat weight compared to the control diet (Table 3). Chicks fed the 1.17 E/N and control diets consumed more nitrogen than those fed the 1.03 diet (Table 4). The 19% CP diets resulted in significantly less nitrogen excretion (g/4 days) than the control diet. Excreted nitrogen expressed as percentages of nitrogen intake was significantly lower for the 1.03 and 1.17 E/N diets than for the other diets. Experiment 2. Statistical analysis indicated that increasing dietary E/N from 0.76 to 1.29 brought about a significant increase in body weight gain and feed efficiency (Table 5). Abdominal fat weight for the 0.99 and 1.29 E/N and control diets were basically the same (Table 3). Chicks on the 1.29 E/N diet retained more nitrogen than those fed the 0.76 Table 3. Effect of dietary E/N ratio on abdominal fat deposition of male broiler chicks 1) 1): At 21 days of age. Each treatment consists of 6 birds. a,b): Means within the same rows with no common superscript are significantly different (p<.05). Table 4. Effect of dietary E/N ratio on nitrogen balance of male broiler chicks from 14 to 18 days of age (Experiment 1)1) 1): Mean of 5 replicates. Means within the same rows with no common superscript are significantly different (p<.05). 2): Nitrogen excreted as percentages of nitrogen intake.

5 1) YAMAZAKI et al.: Dietary Amino Acids and Nitrogen Excretion 23 Table 5. Effect of dietary E/N ratio on performance of male broiler chicks from 7 to 21 days of age (Experiment 2)1) : Each treatment consists of 5 replicates of 2 birds per pen. a,b): Means within the same rows with no common superscript (p<.05). are significantl y different Table 6. Effect of dietary E/N ratio on nitrogen 18 days of age (Experiment 2)1) balance of male broiler chicks from 14 to 1): Mean of 5 replicates. Means within the same rows with no common superscript are significantly different (p<.05). 2): Nitrogen excreted as percentages of nitrogen intake. and 0.99 E/N diets (Table 6). Chicks fed the 1.29 E/N diet excreted approximately 21% less nitrogen (g/4 days) than those on the control diet. Excreted nitrogen expressed as percentages of nitrogen intake for the 1.29 E/N diet was significantly lower than that of the control diet. Discussion Compared to the control diet, the performance on the low protein diets supplemented with synthetic EAA to meet (0.99 E/N diet in experiment 2) or exceed (1.17 E/N diet in experiment 1, and 1.29 E/N diet in experiment 2) the JFS (1992) appeared to be the same in both experiments. Thus, in agreement with YAMAZAKI et al. (1996), dietary CP could be reduced from 21 to 19% without reducing performance. WALDROUP et al. (1976) suggested that broilers might be reared effectively on the diets formulated to meet EAA needs, without compromising protein specifications, provided suitable feedstuffs were used. Supplementing the low E/N diet with EAA resulted in a significantly better body weight gain and feed efficiency, the same as that observed on the 21% CP diet, in both experiments. BEDFORD and SUMMERS (1985) suggested that dietary E/N ratio had a significant quadratic effect on body weight gain and food utilization, and that the optimum was achieved at a 1.22 E/N ratio. In the growing rat, MATSUNO et al. (1976) indicated that feeding a 1.22 E/N ratio diet resulted in a maximum body weight gain.

6 24 Jpn. Poult. Sci., 35 (1) However, in both reports, they also noted that a further increment in E/N ratio resulted in a reduction in performance, in broiler and rat, respectively. Thus, all the evidences suggest that optimum performance may be achieved by feeding a 1.2 to 1.3 E/N diet which provides about 120% of the amino acid requirement. Chicks fed the highest E/N diets excreted about 20% less nitrogen (g/4 days) than those fed 21% CP diets in both experiments. This might be due to increased nitrogen utilization and retention on the higher E/N diet. This is not surprising, since the higher E/N diets contained a 'better balanced' EAA than the 21% CP diets. In the low E/N diets, there is not only a deficiency of EAA but an excess of NEAA. The only outlet for the excess NEAA is deamination and excretion. Furthermore, in growing rats, excreted nitrogen as a percentage of nitrogen intake was minimum on the 1.22 E/ N diet (MATSUNO et al. 1976). The effect of the E/N ratio on the nitrogen excretion of broilers at various growing stages is not clear. This will be investigated in subsequent experiments. In both experiments, abdominal fat content in chicks fed the lower E/N diets was significantly higher than that in chicks fed the control diet. And in experiment 2, there was no significant difference between chicks fed the higher E/N diets and the chicks fed the control diet. Thus, feeding higher E/N diets tend to reduce abdominal fat deposition. This is consistent with the findings of BEDFORD and SUMMERS (1985), who found that carcass fat decreased with an increase in EAA in dietary protein in male broilers from 1 to 3 weeks of age. They maintained that the E/N ratio might influence the allocation of energy to carcass protein and fat, because energy was consumed for body protein instead of fat synthesis. Thus, chicks fed the highest E/N diets showed a better performance in both experiments. In the previous studies, an increase in dietary sulfur containing amino acids (HUYGHEBAERT and PACK, 1996), lysine and arginine (LECLERCQ et al. 1994) from deficiency to requirement level was found to lessen fat deposition in broiler chicks. MENDONCA and JENSEN (1989) showed that dietary methionine excess reduced fat deposition when chicks received a diet containing relatively low protein, but not when they were fed a high protein diet in broilers. Certain amino acids may have potential to reduce body fat deposition, and EAA requirements for minimum abdominal fat deposition in a 19% CP diet may be higher than in that of a 21% CP diet. In conclusion, 1.29 E/N in 19% CP diets clearly reduces nitrogen excretion (g/4 days) by 20% without affecting performance compared to the control diet, and prevents excess fat deposition caused by lessening dietary CP. Acknowledgments This study was presented at the XX World's Poultry Congress in New Delhi, India on September 1996 with the financial support of the Japan Poultry Science Association. References Agriculture, Forestry and Fisheries Research Council Secretariat (1992) Japanese Feeding Standard for Poultry. Central Association of Livestock Industry. Tokyo.

7 YAMAZAKI et al.: Dietary Amino Acids and Nitrogen Excretion 25 BEDFORD, M. R. and J. D. SUMMERS (1985) Influence of the ratio of essential to non essential amino acids on performance and carcass composition of the broiler chick. British Poultry Science, 26: FRAPS, G. S. (1943) Relation of the protein, fat, and energy of the ration to the composition of chickens. Poultry Science, 22: HUYGHEBAERT, G. and M. PACK (1996) Effects of dietary protein content, addition of nonessential amino acids and dietary methionine to cysteine balance on responses to dietary sulphurcontaining amino acids in broilers. British Poultry Science, 37: JACKSON, S., J. D. SUMMERS and S. LEESON (1982) Effect of dietary protein and energy on broiler carcass composition and efficiency of nutrient utilization. Poultry Science, 61: LECLERCQ, B., A. M. CHAGNEAU, T. COCHARD and J. KHOURY (1994) Comparative responses of genetically lean and fat chickens to lysine, arginine and non-essential amino acid supply. I. Growth and body composition. British Poultry Science, 35: MATSUNO, N., M. YAMAGUCHI, R. SAIKI and E. TAMURA (1976) Body weight change and nitrogen efficiencies in growing and adult rats fed diets containing various proportions of essential amino acids to total amino acids. Journal of Nutritional Science and Vitaminology. 22: MENDONCA, C. X. and L. S. JENSEN (1989) Influence of protein concentration on the sulphur-containing amino acid requirement of broiler chickens. British Poultry Science. 30: PARR, J. F. and J. D. SUMMERS (1991) The effect of minimizing amino acid excesses in broiler diets. Poultry Science, 70: SAS Institute (1988) SAS/STATTM User's guide, Release 6.03 Edition. SAS Institute Inc., Cary, NC. U. S. A. WALDROUP, P. W., R. J. MITCHELL, J. R. PAYNE and K. R. HAZEN (1976) Performance of chicks fed diets formulated to minimize excess levels of essential amino acids. Poultry Science, 55: YAMAZAKI, M., H. MURAKAMI, M. YAMAZAKI, and M. TAKEMASA (1996) Reduction of nitrogen excreted from broiler chicks by feeding low-protein, amino acid supplemented diets. Japanese Poultry Science, 33:

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