2003 Poultry Science Association, Inc.
Effect of Method of Feeding and Feed Formulation on Performance and Profitability of Laying Hens: An Econometric Approach H. A. Ahmad1,2 and D. A. Roland, Sr. 341 Poultry Science Department, Auburn University, Alabama 36830
Primary Audience: Poultry Nutritionists, Poultry Extension Personnel, Researchers, and Commercial Producers SUMMARY Egg-producing hens are generally fed based upon their daily feed intake for a predetermined fixed TSAA level. The diet formulation for such hens is based either on lysine or protein, the two commonly employed methods in commercial layer operations. Market variables such as feed and egg price are not directly considered in diet choice selections. In the current research we evaluated two formulation methods, lysine vs. protein, and two feeding methods, constant vs. variable, with an objective of determining the optimal feeding and formulation method under varying market prices for eggs and feeds. Hens fed under the constant method of feeding had significantly higher feed consumption, egg production, egg weight, and body weight than hens fed diets with formulations based on lysine or protein under the variable method of feeding. No difference in the two formulation methods occurred when hens were fed by the variable methods of feeding. Method of formulation (lysine vs. protein) and TSAA levels required for maximum profits can vary from at least 562 to 859 mg per hen/d depending upon energy and protein cost. Key words: feeding method, feed formulation, layer performance, farm income over cost 2003 J. Appl. Poult. Res. 12:291–298
DESCRIPTION OF PROBLEM Commercial White Leghorn layers are generally phase-fed, with subsequent adjustment based upon their daily feed intake levels. Egg producers over the years have streamlined such feeding methodologies and introduce few or no changes even under varying market conditions. Once the laying flock achieves peak production, they are generally fed a series of diets based on daily feed intake to provide fixed and predetermined TSAA intake, without considering the 1 2
effect of market variables, such as egg price and feed price, on production costs and returns. These ration formulations are based either on lysine or protein. A lysine-based diet is formulated by keeping lysine and TSAA ratios constant and allowing the protein level to float. To do so, feed is supplemented with synthetic methionine. This method is generally recommended by amino acid manufacturers and is widely used in the poultry industry. In the protein method of feed formulation, the ration is formulated by
To whom correspondence should be addressed:
[email protected]. Current address: 107 Williams-Bowie Hall, Tuskegee University, Tuskegee, AL 36088.
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292 keeping protein constant and allowing lysine level to float. This method is proposed in at least one breeder management guide [1]. The cost of energy vs. protein, particularly corn and soybean oil meal (SBOM), can substantially affect feed cost and, subsequently, production cost, depending upon which formulation method is being used. For example, if the price ratio between corn (energy) and SBOM (protein) is comparatively narrow, feed formulation based upon protein could be more profitable, as it will be cheaper to add more SBOM for higher protein content in the ration to attain maximum production performance. When protein is expensive, it may be more feasible to balance the ration with synthetic amino acids, thereby using less protein. There is little research information on these two methods of feed formulations, particularly in regard to economics of feeding. Considerable research data is available, however, on different levels of TSAA required to obtain optimum laying hen performance. The National Research Council [2] has recommended 580 mg per hen/ d of TSAA. Schutte et al. [3] found no difference in egg production or egg weight between hens fed TSAA levels ranging from 685 to 820 mg per hen/d from 25 to 49 wk of production. Calderon and Jensen [4] reported methionine requirements of 381, 388, and 414 mg per hen/ d for diets containing 13, 16, and 19% CP, respectively, at TSAA intakes varying between 659 and 773 mg per hen/d. Cao et al. [5] estimated the requirement for methionine and TSAA to be 424 and 785 mg per hen/d, respectively, for an egg mass of 54.3 g per hen/d. All of the abovementioned requirements by various researchers were determined with an objective of obtaining optimum performance. The objectives of this research, however, were to 1) determine the best method of formulation, lysine or protein, and 2) gather data necessary to determine the TSAA requirement for maximum profits using Dekalb Delta hens from 56 to 64 wk of production with various egg and feed prices.
MATERIALS AND METHODS A total of 1,920, 56-wk-old Dekalb Delta hens were randomly divided into 15 dietary treatments (Table 1). There were eight replications of 16 hens per treatment. The hens were housed four per cage (30.5 × 40.6 cm) in a two-
tier cage house. Feed and water were provided for ad libitum consumption. The experiment was conducted (56 to 64 wk of age) in the winter months of November to January, with house temperature cycling between 21.1 to 28.9°C (average 25.5°C) in a computerized temperaturecontrolled building. Computer-linked sensors monitored the inside temperature and accordingly adjusted in-house temperatures. The photoperiod provided was 16 h of light and 8 h of dark. Treatments 1 to 5, formulated based on lysine and fed constantly, varied in protein levels from 18.0 to 15.5%, and TSAA levels from 0.81 to 0.65% (constant feeding, Table 2). Each treatment group was fed the diet shown (Table 2) throughout the experiment regardless of feed intake. These were typical industry diets formulated on the basis of 77 to 95 g per hen/d feed intake to supply 620 mg per hen/day TSAA if they were fed based on feed intake. However, because they were not fed based on feed intake, TSAA intake for treatments 1 to 5 ranged from 857 to 693 mg per hen/d. A second set of diets (variable feeding) were formulated based on lysine and fed based on feed intake to supply 640, 620, 600, 580, or 560 mg of TSAA per hen/d intake for treatments 6, 7, 8, 9, and 10, respectively. These diets were formulated on the basis of lysine and were designed around the formula generally used by layer producers. A third set of diets (variable feeding) provided daily intakes of 620, 600, 580, 560, or 540 mg of TSAA per hen/d for treatments 11, 12, 13, 14, and 15, respectively. These diets were formulated on the basis of protein and were designed around a breeder’s specification [1]. Two levels above and two levels below a recommendation of 580 mg per hen/d of TSAA were used. For each of the last 10 experimental treatments (6 to 15) 10 formulas for each treatment were prepared for intake levels ranging from 77 to 118 g per hen/ d, but only those diets needed based on feed intake were mixed and used. The formulations fed for each treatment (6 to 15) were determined based on the previous 7-d feed intake average. The formula for 100 g per hen/day of feed intake for treatments 6 to 15, along with treatments 1 to 5 (constant diets), are presented in Table 2. All hens in treatments 6 to 15 were initially fed 104 g per hen/d of feed, and as soon as the consumption changed (based on weekly average
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TABLE 1. Experimental design Diets
Feeding method
Formulation method
Comparison 1
1 to 5 vs. 6 to 10
Constant vs. Variable
Based on lysine Based on lysine
Comparison 2
1 to 5 vs. 11 to 15
Constant vs. Variable
Based on lysine Based on protein
Comparison 3
6 to 10 vs. 11 to 15
Variable vs. Variable
Based on lysine Based on protein
feed consumption data), they were switched to the next appropriate feed and so forth. Producers using the variable feeding method feed diets based on feed consumption to maintain a fixed intake of TSAA. For analysis purposes the experiment was divided into three different comparisons (Table 1). In comparison 1, treatments 1 to 5 formulated based on lysine and fed using the constant method of feeding were compared to treatments 6 to 10, variable feeding formulated based on lysine. The diets between each feeding method were pooled together and then compared with each other for possible TSAA effect. In comparison 2, treatments 1 to 5 of the constant method of feeding were compared to treatments 11 to 15 of the variable method of feeding formulated based on protein. In comparison 3, the two variable methods of feeding formulated based on lysine (treatments 6 to 10) and protein (treatments 11 to 15) were compared. For example, the first variable feeding diet (lysine formulation), which contained the highest TSAA level (0.64%), was pooled with the diet of variable feeding (protein formulation), which contained the highest TSAA level (0.62%), and so on until the respective diets in each method were pooled with each other, and then these diets were compared for possible TSAA effect. Diets, feeding method and formulation method were compared in the following manner. The performance criteria used in this experiment were feed consumption, egg production, egg weight, shell quality (egg specific gravity), and BW. Feed consumption and hen-day egg production were determined weekly. Egg weight was determined biweekly and egg specific gravity at the 60th and 64th wk of age on all the eggs saved on two separate days. Egg specific gravity was determined by dipping eggs in graded salt solutions of 0.005 increments. Body
weight of 64 individual hens for each treatment was determined at the end of the experiment. The data were analyzed as a completely randomized block design with cage row location as a block using the General Linear Model Procedure of SAS [6]. The farm income was calculated using the following formula: Farm income over feed cost (FIOC) = farm egg income − nonfeed production cost − feed cost. FIOC = farm egg income − $0.18 − feed cost The FIOC here reflects the net gain at the production level. Production cost includes the nonfeed cost, such as the cost of the replacement pullet, farm management, labor, utilities, and so forth. The last variable in the FIOC formula is the cost of mixed feed for layers.
RESULTS AND DISCUSSION Comparison 1 The TSAA content of dietary treatments 1 to 10 in comparison 1, constant vs. variablelysine method of feeding, had no overall significant effect on feed consumption, egg production, egg weight, egg specific gravity, or BW. The data for TSAA (dietary treatments) comparisons and interaction between the TSAA and feeding methods for all three comparisons, being statistically NS, are not presented. Hens fed treatments 1 to 5 using the constant method of feeding and lysine formulation had significantly higher feed consumption (2 g), egg production (3%), egg weight (0.8 g), and BW (0.05 kg) than hens fed treatments 6 to 10 using the variable method of feeding formulated based on lysine (Tables 3 and 4). There was no difference in mortality between treatments (TSAA) or method of feeding (data not shown). There was also no interaction found between the diets (TSAA) and feeding methods.
18.0 2,803 4.0 0.66 0.45 0.52 0.81 0.97
Calculated analysisG Protein ME kcal/kg Calcium Total phosphorus Avail phosphorus Methionine TSAA Lysine
17.3 2,814 4.0 0.65 0.45 0.48 0.76 0.92
61.2 25.2 7.06 2.00 1.86 1.59 0.45 0.25 0.25 0.19 126
2
16.7 2,809 4.0 0.65 0.45 0.45 0.72 0.87
63.5 23.3 7.07 2.00 1.87 1.14 0.46 0.25 0.25 0.16 122
3
16.1 2,809 4.0 0.64 0.45 0.43 0.69 0.83
65.3 21.8 7.07 2.00 1.88 0.80 0.44 0.25 0.25 0.14 119
4
15.5 2,812 4.0 0.64 0.45 0.40 0.65 0.79
67.1 20.4 7.08 2.00 1.89 0.50 0.42 0.25 0.25 0.12 116
5
14.9 2,816 4.25 0.49 0.30 0.40 0.64 0.75
68.4 18.8 8.17 2.00 1.11 0.50 0.41 0.25 0.25 0.13 111
6D
14.6 2,824 4.25 0.48 0.30 0.38 0.62 0.72
69.2 18.0 8.17 2.00 1.11 0.50 0.41 0.25 0.25 0.12 110
7
14.3 2,833 4.25 0.48 0.30 0.37 0.60 0.72
70.1 17.1 8.17 2.00 1.12 0.50 0.41 0.25 0.25 0.11 109
8 70.9 16.3 8.17 2.00 1.12 0.50 0.41 0.25 0.25 0.10 108
9
13.9 2,841 4.25 0.48 0.30 0.36 0.58 0.68
Variable-lysineB
Experimental diets
13.7 2,849 4.25 0.48 0.30 0.36 0.58 0.65
71.7 15.5 8.18 2.00 1.13 0.50 0.41 0.25 0.25 0.10 107
10
16.0 2,860 4.25 0.49 0.30 0.36 0.62 0.83
63.8 22.0 8.16 2.00 1.09 2.03 0.41 0.25 0.25 0.08 116
11
15.5 2,860 4.25 0.49 0.30 0.35 0.60 0.79
65.4 20.6 8.16 2.00 1.10 1.75 0.41 0.25 0.25 0.08 114
12
15.0 2,860 4.25 0.49 0.30 0.34 0.58 0.76
67.1 19.2 8.17 2.00 1.11 1.47 0.41 0.25 0.25 0.07 111
13
14
14.5 2,860 4.25 0.48 0.30 0.33 0.56 0.72
68.7 17.9 8.17 2.00 1.11 1.18 0.41 0.25 0.25 0.06 109
Variable-proteinC
14.0 2,860 4.25 0.48 0.30 0.32 0.54 0.68
70.4 16.5 8.17 2.00 1.12 0.90 0.41 0.25 0.25 0.06 107
15
B
Treatments 1 to 5, formulated based on lysine and fed constantly. Treatments 6 to 10, formulated based on lysine and fed variably. C Treatments 11 to 15, formulated based on protein and fed variably. D Treatments 6 to 15 were formulated for 100 g per hen/d (22 lbs/100 hens per day) feed intake, although the actual feed intake for respective experimental birds was different because they were fed based on intake. E Provided per kilogram of diet: vitamin A, 8,000 IU; cholecalciferol, 2,200 IU; vitamin E, 8 IU; vitamin B12, 0.02 mg; riboflavin, 5.5 mg; d-calcium pantothenate, 13 mg; niacin, 36 mg; choline, 500 mg; folic acid, 0.5 mg; thiamin, 1 mg; pyridoxine, 2.2 mg; biotin, 0.05 mg; menadione sodium bisulfite complex, 2 mg. F Provided per kilogram of the diet: manganese, 65 mg; iodine, 1 mg; iron, 55 mg; copper, 6 mg; zinc, 55 mg; selenium, 0.3 mg. G The chemical analysis for protein, methionine, cystine, and lysine was 8.29, 0.19, 0.19, and 0.24%, respectively, for corn and 48.9, 0.52, 0.78, and 3.08%, respectively, for soybean meal.
A
59.1 27.0 7.06 2.00 1.85 1.84 0.48 0.25 0.25 0.22 130
1
Corn SBOM 48% Limestone Pullet size CaCO3 Dical phosphate Poultry oil NaCl Vitamin premixE Mineral premixF DL-methionine Cost/ton $
Ingredients (%)
Constant-lysineA
TABLE 2. Ingredient and nutrient composition of experimental diets
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TABLE 3. Influence of feeding method (constant vs. variable-lysine) and formulation method (lysine vs. protein) on laying hen performance (56 to 64 wk)A Feeding and formulation method
Feed consumption (g/h per d)
Egg production (% h/d)
Egg weight (g)
Egg specific gravity
Comparison 1 Constant-lysine (diets 1–5) Variable-lysine (diets 6–10)
* 106 ± 1.61 104 ± 2.26
* 84 ± 6.96 81 ± 6.41
* 65.8 ± 1.29 65.0 ± 1.26
1.0806 ± 0.0015 1.0805 ± 0.0015
Comparison 2 Constant-lysine (diets 1–5) Variable-protein (diets 11–15)
* 106 ± 1.61 105 ± 1.97
* 84 ± 6.96 82 ± 6.08
* 65.8 ± 1.29 65.0 ± 1.26
1.0806 ± 0.0015 1.0802 ± 0.0014
Comparison 3 Variable-lysine (diets 6–10) Variable-protein (diets 11–15)
NS 105 ± 1.97 104 ± 2.26
NS 82 ± 6.08 81 ± 6.41
NS 65.0 ± 1.264 65.0 ± 1.65
1.0802 ± 0.0014 1.0805 ± 0.0015
A Average values with standard deviation from 8 replicates of 16 hens over the entire experimental period. *Significantly different (P < 0.05).
Comparison 2 The TSAA level of dietary treatments 1 to 5 and 11 to 15 in comparison 2, constant-lysine vs. variable-protein method of feeding, had no significant effect on feed consumption, egg production, egg weight, egg specific gravity, or BW (data not shown). As in comparison 1, hens fed treatments 1 to 5 using the constant method of feeding had significantly higher feed consumption (1 g), egg production (2%), egg weight (0.8 g), and BW (0.05 kg) than hens fed treatments 11 to 15 using the variable method of feeding formulated based on protein (Tables 3 and 4). There was no difference in mortality between dietary treatments or method of feeding (data not shown). There was no interaction found between diets (TSAA) and method of feeding in any of the performance criteria. Comparison 3 The TSAA level of dietary treatments 6 to 15 in comparison 3, variable-lysine vs. variableprotein, had no significant effects on feed consumption, egg production, egg weight, egg specific gravity, or BW (data not shown). The two methods of formulation, lysine and protein, did not produce any significant effect on feed consumption, egg production, egg weight, egg specific gravity, or BW (Tables 3 and 4). There was no difference in mortality between either treatment or method of feeding (data not shown). There was no interaction found between diets (TSAA) and method of feeding in any of the
performance criteria, except egg production that was significantly lower when hens were fed treatment 15 with the lowest TSAA level. In the first two comparisons, when the constant feeding based on lysine was compared to the variable feeding based on lysine or protein, hens fed constantly had better production performance in terms of egg production and egg weight. One of the major reasons for this was the first five diets of the constant feeding method supplied higher nutrient densities, particularly TSAA, ranging from 857 to 693 mg per hen/d throughout the entire duration of the experiment. In the constant method of feeding, the same diets were fed regardless of the feed intake and, therefore, hens overconsumed diets and produced eggs at a higher rate compared with other experimental diets, which were adjusted as feed intake varied. The improvement in egg production was not big enough to offset extra cost of additional nutrients; therefore, the dietary treatment 5, which was least expensive in that series, proved most profitable. This situation could have been alleviated if feeds had been formulated for the higher intake levels, thereby diluting the nutrient densities. Ingredient composition was the other factor that could have optimized the constant feeding method based on lysine. Although 100 diets were formulated for treatment 6 to 15 (10 for each treatment) in case the hens switched from one intake level to another, only two to three diets for each treatment of variable feeding were actually fed. With computerized control of temperature, hens con-
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TABLE 4. Influence of feeding methods and methods of formulation and dietary total sulfur amino acid level on BW of hens (kg) at the end of the experiment: comparisons 1 through 3 Feeding method
Comparison 1A
Comparison 2B
Comparison 3C
* 1.80 1.75
* 1.80
NS
Constant-lysine (diets 1–5) Variable-lysine (diets 6–10) Variable-protein (diets 11–15) TSAA level
Feeding methods × TSAA
1.75 1.75
1.75 Diets (1 + 6) (2 + 7) (3 + 8) (4 + 9) (5 + 10) Diets 1 2 3 4 5 6 7 8 9 10
Diets (1 + 11) (2 + 12) (3 + 13) (4 + 14) (5 + 15)
1.80 1.76 1.78 1.77 1.76
Diets 1 2 3 4 5 11 12 13 14 15
1.85 1.74 1.81 1.79 1.81 1.75 1.79 1.74 1.76 1.72
1.80 1.73 1.76 1.77 1.77
1.85 1.74 1.81 1.79 1.81 1.75 1.80 1.71 1.75 1.72
Diets (6 + (7 + (8 + (9 + (10 + Diets 6 7 8 9 10 11 12 13 14 15
11) 12) 13) 14) 15)
1.75 1.79 1.73 1.76 1.72
1.75 1.79 1.74 1.76 1.72 1.75 1.80 1.71 1.75 1.72
A
Constant vs. variable-lysine (treatments 1 to 5 and 6 to 10). Constant vs. variable based on protein (treatments 1 to 5 and 11 to 15). C Variable-lysine vs. variable-protein (treatments 6 to 10 and 11 to 15). *Significantly different (P < 0.05). B
sumed a fairly uniform quantity of feed throughout the experiment. Therefore, only two or three feeds for each treatment were necessary in order to maintain a constant intake of nutrients. The 15 experimental diets, which ranged in TSAA content from 0.54 to 0.81% produced little or no difference in egg production, but their cost per ton varied greatly ($109 to $130) because of the ingredient prices used (Tables 2 and 5). When FIOC were calculated, the diet supplying 620 mg per hen/d of TSAA formulated based on lysine and fed variably proved the most profitable under the given conditions of feed and egg price (corn, $2.50/bushel and SBOM, $200/ton; Table 5). These are typical market prices for feed and eggs. For Delta hens in their late production phase (56 to 64 wk), the price spread between medium and large eggs had little influence on FIOC because very few medium eggs were produced. Therefore, change in feed prices has a greater influence on FIOC and the TSAA requirement. As the price of SBOM increases (from $200 to $300/ton) in relation to corn, the diets formulated based on
low protein become more feasible (Table 5) due to less cost for each additional unit of protein added in the ration. Because of this, the method of feeding and TSAA required for maximum profits varied. In this experiment, the TSAA for maximum FIOC for the variable method of feeding can be shown to vary from 620 to 540 mg per hen/d (treatments 7 and 15, respectively at 100 g intake per day) simply by changing feed and egg prices (Table 5). For example, with a corn price of $2.50/bushel and SBOM price of $200/ton, the TSAA requirement for maximum profit was obtained from hens fed the variablelysine diets supplying 620 mg TSAA per hen/ d. With these feed prices, the maximum FIOC was 15.97¢ per dozen eggs at typical egg prices. However, with a high SBOM price, $300/ton, the TSAA requirement for maximum profit was 540 mg of TSAA per hen/d both at high or low spread between medium and large eggs. This indicated that TSAA levels required for maximum profits decreased as the SBOM price increased. The reason for this is the difference in ingredient cost between the 0.62 and 0.54%
106 103 104 104 104
104 106 104 105 104
Variable-lysine 6 7 8 9 10
Variable-protein 11 12 13 14 15
645 636 603 588 562
678 639 624 603 582
859 813 763 738 696
TSAA (mg/h per d)
298 302 298 299 297
301 291 295 296 296
297 301 299 299 300
ME (kcal/h per d)
116.59 114.73 112.78 110.89 109.24
114.02 112.95 111.84 110.79 109.69
129.84 126.63 123.26 120.08 117.86
Feed cost ($/ton)
15.28 14.98 15.01 15.06 15.67
15.03 15.97 15.89 15.35 15.18
13.47 13.95 14.01 14.77 14.96
FIOC (¢/doz)
D
142.37 141.98 141.55 141.13 140.83
142.28 142.01 141.74 141.50 141.21
147.65 146.79 145.64 144.43 143.76
20.43 19.75 19.45 19.22 19.71
19.60 20.59 20.37 19.53 19.06
19.99 20.08 19.69 20.15 20.04
−1.48 −2.10 −2.25 −2.37 −1.84
−2.31 −1.54 −1.22 −2.02 −2.65
−2.14 −2.38 −2.50 −2.18 −2.29
Low
124.63 121.19 117.65 114.20 111.01
119.44 117.42 115.32 113.32 111.27
146.66 141.08 135.42 130.31 126.35
$/ton
23.36 23.27 23.54 23.86 24.74
23.51 24.67 24.69 24.30 24.27
20.15 21.03 21.41 22.52 22.99
1.44 1.43 1.84 2.27 3.19
1.59 2.55 3.09 2.75 2.57
−1.97 −1.42 −0.78 0.20 0.66
LowF
HighE
High
E
$/ton
Spread
Spread F
FIOC (¢/doz)
FIOC (¢/doz)
B
A
Typical feed cost: corn, $2.50/bushel; SBOM, $200/ton. Ton = 2,000 lbs (909 kg). Typical egg price: jumbo, $0.61; extra large, $0.55; large, $0.50; medium, $0.38; small, $0.32; check, $0.24. Corn, $4.00/bushel; SBOM, $150/ton. C Corn, $2.00/bushel; SBOM, $300/ton. D FIOC (farm income over feed cost) = farm income − nonfeed production cost − feed cost. E High egg spread: jumbo, $0.71; extra large, $0.65; large, $0.60; medium, $0.38; small, $0.32; check, $0.24. F Low egg spread: jumbo, $0.42; extra large, $0.41; large, $0.40; medium, $0.38; small, $0.32; check, $0.24.
106 107 106 107 107
Constant-lysine 1 2 3 4 5
Diets
Feed intake (g/hen per d)
A
Low corn, high SBOMC
High corn, low SBOMB
TABLE 5. Effect of feed price as influenced by corn and soybean oil meal (SBOM) price and spread in egg price between large- and medium-sized eggs on profits and nutrient requirements of Delta hens (56 to 64 wk) fed experimental diets
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298 TSAA diets, due to variation in energy and protein prices. With high-protein and low-energy ingredient prices it costs less to formulate diets with lower protein levels. These results are in partial agreement with those of Schutte et al. [3], who did not find any difference in egg production or egg weight when hens were fed diets supplying 690 to 820 mg of TSAA per hen/d. Our main emphasis, however, was not to determine the TSAA requirement for
maximum performance but to gather data so that TSAA requirements could be determined under any given market conditions using different feeding and formulation methods. In order to determine the TSAA requirement for commercial leghorn hens, all the related aspects of production, management, environment, feeding and formulation methods, and market variables (feed and egg prices) must be carefully analyzed.
CONCLUSIONS AND APPLICATIONS 1. Dietary TSAA level had no influence on feed consumption, egg production, egg weight, egg specific gravity, BW, or mortality within the ranges used in this experiment. 2. Hens fed diets using a constant method of feeding had superior production performance than hens fed diets formulated based on lysine or protein using the variable method of feeding. With the typical prices used at the time of the experiment, hens fed the lowest-price constant-lysine diet had the greatest FIOC mainly because the higher egg production on the nutrient-dense diets did not offset the extra cost of more nutrients. 3. When variable lysine or protein feeding were compared, no differences in production performance was measured, indicating little impact of either feeding method. 4. It was concluded that the method of formulation (lysine vs. protein) and TSAA levels required for maximum farm income over cost can vary from at least 562 to 859 mg per hen/d, depending upon energy and protein cost and methods of feeding.
REFERENCES AND NOTES 1. Hy-Line. 1992. Management Guide. 4th ed. Hy-Line International, West Des Moines, IA. 2. National Research Council. 1994. Nutrient Requirements of Poultry. 9th rev. ed. Natl. Acad. Press, Washington, DC. 3. Schutte, J. B., J. De Jong, and H. L. Bertram. 1994. Requirement of the laying hen for sulfur amino acids. Poult. Sci. 73:274–280.
4. Calderon, V. M., and L. S. Jensen. 1990. The requirement for sulfur amino acid by laying hens as influenced by the protein concentration. Poult. Sci. 69:934–944. 5. Cao, Z., C. J. Jevne, and C. N. Coon. 1992. The methionine requirement of laying hens as affected by dietary protein levels. Poult. Sci. 71(Suppl. 1):39. (Abstr.). 6. SAS Institute Inc. 1990. SAS User’s Guide: Statistics. Version 6. ed. SAS Inst. Inc., Cary, NC.
