Re-evaluation of the isoleucine requirement of the commercial layer

Re-Evaluation of the Isoleucine Requirement of the Commercial Layer1 M. Shivazad,2 R. H. Harms,3 G. B. Russell, D. E. Faria,4 and R. S. Antar Department of Animal Sciences, University of Florida, Gainesville, Florida 32611 ABSTRACT An experiment was conducted with HyLine W36 hens to re-evaluate their Ile requirements from a corn-soybean meal diet. Eight experimental diets were fed with Ile levels of 0.60, 0.57, 0.54, 0.51, 0.48, 0.45, 0.42, and 0.39%. Supplemental amino acids (AA) were added to ensure that Ile was the first-limiting AA. Increasing levels of Ile above 0.51% significantly increased egg production (EP), egg weight (EW), and egg mass (EM).

Egg production, EW, and EM decreased each time the Ile content of the diet was decreased. Feed consumption (FC) and energy intake were not significantly decreased until the diet contained 0.45% Ile, and, at this time, BW was significantly reduced. Broken-line regression indicated a daily Ile requirement of 449.8, 497.0, and 469.0 mg/d for EP, EW, and EM, respectively, which indicated a requirement of 9.30 mg Ile/g EM.

2002 Poultry Science 81:1869–1872

INTRODUCTION Supplemental Met is routinely used in layer feeds, resulting in a lower dietary protein content. The use of supplemental Met results in a reduction of feed cost and a reduction in feed consumption (FC), as dietary energy increases. Some supplemental Lys is used when there is a large price spread between grain and soybean meal. Feed grade Trp, Thr, and Ile are available; however, essentially none are used in layer feeds. There is interests in the use of these amino acids (AA), as they are beneficial to the environment (i.e., nitrogen output from livestock and poultry are reduced). In addition, the production of pure AA is increasing (Muirhead, 2002). Isoleucine is one of the six deficient AA in corn-soybean meal diets. Recent suggestions for the Ile requirement have been variable. The NRC has increased its Ile recommendation for commercial layers from 0.5% of the diet (NRC, 1971) to 650 mg/d per hen (NRC, 1994). Harms and Russell (2000a) recently suggested a daily requirement of Ile at 601 mg/ d, which is slightly lower than the two most recently published requirements (Gous et al., 1987; Coon and

2002 Poultry Science Association, Inc. Received for publication March 7, 2002. Accepted for publication July 23, 2002. 1 This research was supported by the Florida Agricultural Experiment Station and a gift from Novus International, #20 Research Park Drive, St. Charles, MO 63304 and approved for publication as Journal Series No. 08690. 2 Visiting Professor, University of Tehran, Tehran, Iran. 3 To whom correspondence should be addressed: harms@ animal.ufl.edu. 4 Visiting Professor, Universidade de Sao Paulo (USP), Pirassununga, Brazil.

Zhang, 1999). Harms (unpublished data) formulated one diet for each of the six critical AA that were predicted to support approximately 95% performance of the hen. He found the Ile requirement to be 8.95 mg/g of egg content (EC) or 492 mg/d per hen. This daily requirement was considerably less than 650 to 700 mg suggested by Gous et al. (1987) or 579 mg of digestible Ile suggested by Coon and Zhang (1999). There is considerable interest in using more AA in poultry feeds. Therefore, the present experiment was conducted to re-evaluate the Ile requirement of the commercial layer.

MATERIALS AND METHODS Hy-Line W36 hens, 35 wk of age, were used in this experiment; average EP at this time was 90.8%. The hens were housed one bird per cage (25.6 × 46.2 cm) in a windowless, fan-ventilated house. The temperature of the house was not allowed to fall below 26.7 C. Therefore, the temperature was almost constant because the experiment was conducted in late October through late December. The temperature was controlled to achieve a uniform feed intake at a level at which an Ile deficiency could be produced. The photoperiod was 16 h/d. Eight experimental diets were used (Table 1). Diet 1 contained 0.60% Ile and other AA above the level required by the hen. Diet 2 contained 0.57% Ile (95% of Diet 1), and all other AA were maintained at 100% of Diet 1. Diet 3 contained 0.54% Ile (90% of Diet 1), and the other AA

Abbreviation Key: AA = amino acids; EC = egg content; EP = egg production; EM = egg mass; EW = egg weight; FC = feed consumption.

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(Key words: commercial layer, isoleucine, egg production, egg mass)

72.13 17.80 7.51 1.28 0.38 0.25 0.25 0.11 0.18 0.03 0.04 0.04 13.656 0.340 0.820 0.190 0.513 0.699 0.570 2,866

70.08 19.29 7.52 1.26 0.38 0.25 0.25 0.11 0.13 — — —

14.163 0.340 0.820 0.190 0.507 0.684 0.600 2,852

2 0.57% Ile

13.026 0.323 0.779 0.181 0.487 0.664 0.540 2,879

73.63 16.29 7.50 1.31 0.38 0.25 0.25 0.10 0.18 0.03 0.04 0.03

3 0.54% Ile

12.394 0.306 0.738 0.171 0.461 0.629 0.510 2,892

75.13 14.78 7.50 1.34 0.38 0.25 0.25 0.10 0.18 0.02 0.04 0.03

4 0.51% Ile (%)

11.765 0.289 0.697 0.162 0.436 0.594 0.480 2,904

76.64 13.28 7.49 1.37 0.38 0.25 0.25 0.09 0.18 0.02 0.03 0.03

5 0.48% Ile

2

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7 0.42% Ile

79.64 10.26 7.48 1.42 0.38 0.25 0.25 0.07 0.18 0.01 0.02 0.03 10.502 0.255 0.615 0.143 0.384 0.524 0.420 2,930

6 0.45% Ile

78.14 11.77 7.49 1.40 0.38 0.25 0.25 0.08 0.18 0.02 0.03 0.03 11.133 0.272 0.656 0.152 0.410 0.559 0.450 2,918

9.872 0.238 0.574 0.133 0.359 0.489 0.390 2,943

81.15 8.76 7.47 1.45 0.38 0.25 0.25 0.06 0.18 0.01 0.02 0.03

8 0.39% Ile

Contains 18.5% P and 21% Ca. Supplies per kilogram of diet: biotin, 0.2 mg; cholecalciferol, 2,200 IU; choline, 500 mg; ethoxyquin, 65 mg; folic acid, 1 mg; niacin, 60 mg; pantothenic acid, 15 mg; pyridoxine, 5 mg; riboflavin, 5 mg; thiamin, 3 mg; vitamin A, 8,000 IU; vitamin B12, 0.02 mg; vitamin E, 20 IU; and vitamin K, 2 mg. 3 Supplies per kilogram of diet: copper, 10 mg; iodine, 2 mg; iron, 60 mg; manganese, 90 mg; selenium, 0.2 mg; and zinc, 80 mg.

1

Ingredient Yellow corn Soybean meal (48%) Limestone Dicalcium Phosphate1 Common salt Vitamin mix2 Mineral mix3 DL-Met (98.5%) L-Lys-HCl (98.5%) L-Thr (98.5%) L-Val (98.5%) L-Trp (98.5%) Calculated Analysis (%) Protein Met Lys Trp Thr Val Ile Energy (Kcal ME/kg)

1 0.60% Ile

Diet

TABLE 1. Composition of diets

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ISOLEUCINE REQUIREMENT OF COMMERCIAL LAYERS

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were held at 95% of Diet 2. Diet 4 contained 0.51% Ile (85% of Diet 1), and all other AA were adjusted to 90% of Diet 2. Diet 5 contained 0.48% Ile (80% of Diet 1), and the levels of other AA were held at 85% of Diet 2. Diet 6 contained 0.45% Ile (75% of Diet 1), and all other AA were held at 80% of Diet 2. Diet 7 contained 0.42% Ile (70% of Diet 1), and the levels of other AA were held at 75% of Diet 2. Diet 8 contained 0.39% Ile (65% of Diet 1), and all other AA were held at 70% of Diet 2. The diets were not kept isocaloric; this is not a problem, as results were to analyze Ile intake. Also, the procedure of allowing energy to increase when protein and AA decrease is the program that would be used by a commercial poultry producer. These procedures of reducing other AA as Ile was reduced eliminated a large excess of the other AA, but the diets still contained an adequate amount of other AA. Eight replicates of five hens were fed each diet. The Ile in all diets was furnished by corn and soybean meal. Amino acid analyses were determined for corn and soybean meal and were the basis for dietary calculated values for diets. Egg production was recorded for individual hens, but was analyzed on a replicate basis. Feed consumption was measured biweekly, and orts were replaced with fresh feed at that time. One egg from each hen was weighed weekly. Egg mass was calculated by multiplying percentage EP by EW for each replicate. The hens were individually weighed at the beginning and end of the experiment, and weight change was calculated. The daily intake of Ile and energy was calculated by multiplying the concentrations in the feed by FC. Kilocalories of energy and milligrams of Ile per gram of EM were calculated by dividing the daily intake by daily EM. The experiment was conducted for 8 wk; however, the first 2 wk were considered an adjustment period, and Weeks 3 to 8 were used to test experimental treatments. This procedure has been used in our laboratories for AA studies (Harms and Russell, 1996). These data were subjected to ANOVA with the general linear models procedure of SAS (1990). Diet × replicate (49 df) was used to test significance of diet and where significant Duncan’s multiple range test (1955) was used to determine significant differences among treatment means. The Ile requirements for EP, EM, and EW change were determined by using broken-line regression as described by Noll and Waibel (1989).

RESULTS AND DISCUSSION Decreasing the Ile content of the diet from 0.60 to 0.51% did not significantly decrease EP (Table 2). However, there was a significant decrease in EP each time the Ile was decreased below 0.51%. Broken-line regression of EP on Ile intake (Figure 1) resulted in a requirement of 449.8 ± 8.8 mg/d per hen (R2 = 0.90). Egg weight followed the same trends as EP and was not significantly decreased until the Ile content of the diet was decreased to 0.48% (Table 2). Each time the Ile was decreased below 0.51%, EW was decreased, except when

FIGURE 1. Broken-line regression of egg production, egg weight, and egg mass on Ile intake.

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SHIVAZAD ET AL. TABLE 2. Performance of commercial laying hens fed diets with various levels of Ile

Dietary Ile (%) 0.60 0.57 0.54 0.51 0.48 0.45 0.42 0.39

Egg production

Egg weight

Egg mass (EM)

Feed consumption

(%) 88.5a 88.2ab 87.9ab 86.8ab 83.5b 77.4c 67.9d 63.3e

(g) 56.9ab 57.1a 56.8ab 56.5ab 55.5bc 54.9cd 55.7bc 54.0d

(g) 50.3a 50.3a 50.0a 49.0a 46.3b 42.7c 37.8d 34.1e

(g) 88.3a 91.4a 89.6a 89.7a 88.6a 80.1b 73.9c 70.1c

Weight change

Energy intake (kcal/h per d) 252a 262a 259a 259a 257a 234b 217c 206c

kcal/g EM) 5.02f 5.22ef 5.17ef 5.29de 5.56c 5.49cd 5.80b 6.09a

(g) 10a 11a 3a –8a –37a –93b -137c -188d

Ile (mg/d) 530a 521a 484b 457c 425d 360e 310f 273g

(mg/g EM) 10.55a 10.38a 9.70b 9.32bc 9.20c 8.46d 8.32d 8.07de

Means with the same superscript within a column do not differ significantly (P < 0.05).

a–g

of dietary Ile significantly increased weight loss each time the Ile was reduced. The requirement of Ile in the present experiment was 9.30 (469.0 ÷ 50.4) mg to produce a gram of EM for hens producing 50.4 g EM. This would be a 511.5 (9.30 × 55)mg daily requirement when the hen is producing 55 g EM. The daily requirement of 511.5 mg/d is near the requirement of 492 (8.95 × 55) mg recently found (Harms, unpublished data). However, this requirement per day is considerably less than the 650 mg suggested by NRC (1994), the 650 to 700 mg suggested by Gous et al. (1987), and the 579 mg digestible Ile suggested by Coon and Zhang (1999).

REFERENCES Coon, C., and B. Zhang. 1999. Ideal amino acid profile for layers examined. Feedstuffs 71:13–15, 31. Duncan, D. B. 1955. Multiple range and multiple F tests. Biometrics 11:1–42. Gous, R. M., M. Grissell, and T. R. Morris. 1987. Effect of dietary energy concentrations on the response to amino acids. Br. Poult. Sci. 28:427–436. Harms, R. H., and G. B. Russell. 1996. A re-evaluation of the methionine requirement of the commercial layer. J. Appl. Anim. Res. 9:141–151. Harms, R. H., and G. B. Russell, 2000a. Evaluation of the isoleucine requirement of the commercial layer in a corn-soybean meal diet. Poult. Sci. 79:1154–1157. Harms, R. H., and G. B. Russell, 2000b. Evaluation of tryptophan requirement of the commercial layer using a corn-soybean meal basal diet. Poult. Sci. 79:740–742. Muirhead, S., 2002. Ajnomoto opens Iowa threonine production facility. Feedstuffs 74:1–3. National Research Council. 1971. Nutrient Requirements of Poultry. 6th rev. ed. National Academy Press, Washington, DC. National Research Council. 1994. Nutrient Requirements of Poultry. 9th rev. ed. National Academy Press, Washington, DC. Noll, S. L., and P. E. Waibel. 1989. Lysine requirement of the growing turkey in various temperature environments. Poult. Sci. 68:781–794. SAS Institute. 1990. SAS User’s Guide. Statistics. SAS Institute Inc., Cary, NC.

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the diet contained 0.42% Ile. The EW was heavier than expected with this diet, which was likely due to a larger reduction in EP than expected with this diet. Broken-line regression of EW on Ile intake (Figure 1) resulted in a requirement of 497.0 ± 49.3 mg/d per hen (R2 = 0.34). The R2 (0.34) for the regression of EW was very low. This was a result of the large variation in EW (Figure 1). The low R2 value for EW might be unexpected with R2 values of 0.90 and 0.93 for EP and EM, respectively. However, using EM of 50.41 g and EP of 88.23% indicated by regression, the calculated EW would be 57.13 g, which is in close agreement with the 56.90-g EW indicated by regression analysis. In several experiments, we have observed a low R2 for EW; however, the regression equation indicated essentially the same EW as calculated EW when using EP and EM (Harms and Russell, 2000a,b). Egg mass followed the same trend as EP and EW (Table 2) with no significant decrease until Ile was reduced below 0.51%. Each time the Ile was reduced below this level, EM was significantly decreased. Broken-line regression of EM on Ile intake (Figure 1) indicated a requirement of 469.0 ± 7.3 mg/d per hen (R2 = 0.93). Feed consumption and energy intake were not significantly reduced until the diet contained 0.45% Ile (Table 2). There was a significant reduction in feed and energy intake each time the Ile content of the diet was reduced below 0.48%; however, the energy intake was not significantly different for hens fed the diets with 0.39 and 0.42% Ile. The energy intake to produce a gram of EM was significantly increased when the Ile content of the diet was reduced to 0.51% (Table 2). Hens receiving the diets with 0.42 and 0.39% Ile had the highest intake of Ile per gram of EM. The intake of Ile per day decreased as the dietary level of Ile decreased (Table 2). The intake of Ile per gram of EM also decreased as the dietary level of Ile decreased. A significant decrease occurred when the Ile in the diet was reduced from 0.57 to 0.54%. There was a further decrease when the Ile was decreased to 0.48%, and a further decrease when the Ile was reduced to 0.45%. Body weight was not significantly changed until the Ile was reduced below 0.48% (Table 2). Further reduction