Department of Animal Sciences, University of Florida, Gainesville, Florida 32611

Transcription

1 Performance of Commercial Laying Hens when Six Percent Corn Oil Is Added to the Diet at Various Ages and with Different Levels of Tryptophan and Protein 1 R. S. Antar, R. H. Harms, 2 M. Shivazad, 3 D. E. Faria, 4 and G. B. Russell Department of Animal Sciences, University of Florida, Gainesville, Florida ABSTRACT Three experiments were conducted to evaluate the use of corn oil in the diet of commercial layers as a method of increasing egg weight. In the first experiment, the performance of commercial layers receiving 6% added corn oil beginning at 18 to 30 wk at 2- wk intervals was evaluated. In the second experiment, comparisons were made between performance of young and old commercial layers when 6% corn oil was added to the diet. The third experiment was conducted to evaluate the effects upon commercial layers when 6% corn oil was added to diets varying in Trp content. In experiment 1, egg weights increased during the first 2 wk that corn oil was added to the diet. During this time, the intake of Trp was greater than or equal to the hen requirements. However, during the last 2 wk of the experiment, when Trp intakes were low, egg weights (Key words: commercial layer, corn oil, dietary energy, egg weight, tryptophan) INTRODUCTION Increasing egg weight (EW) is of considerable economic importance, especially during early egg production and periods of hot weather. The price spread in Florida between medium and large eggs has ranged from 4 to 38 cents per dozen (Bohnsack et al., 2002). Extensive research has been conducted on increasing EW. Supplemental fat has been shown to produce small increases in EW (Hochreich et al., 1958; Combs and Helbacka, 1960). The addition of corn oil to the diet has been shown to be the most effective fat source for increasing EW (Jensen et al., 1957; Marion and Edwards, 1964; Bohnsack et al., 2002). In 2004 Poultry Science Association, Inc. Received for publication September 10, Accepted for publication October 20, 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. R To whom correspondence should be addressed: harms@animal. ufl.edu. 3 University of Tehran, Tehran, IRAN. 4 Universidade de Sao Paulo (USP), Pirassununga, Brazil. decreased when corn oil was added to the diet. In experiment 2, egg weights from young and old hens increased during the first 2 wk after corn oil was added to the diet. During the last 2 wk, egg weights from young hens decreased, whereas egg weights from old hens increased. In experiment 3, egg weight was not affected when the diet contained or 0.176% Trp. However, egg weights significantly increased when corn oil was added to the diet containing 0.193% Trp. The data in these experiments indicate that the diet of a laying hen must contain a high level of Trp to get an increase in egg weight from the addition of corn oil to the diet. Also the need for other amino acids must be met. Therefore, the hen eats to meet her energy requirement for maximum egg production, and her amino acid intake determines the egg weight Poultry Science 83: recent studies, the addition of 6% corn oil to the diet resulted in a 2.5-g increase in EW (Harms et al., 2000; Bohnsack et al., 2002). Harms et al. (2000) reported a significant interaction of weeks by diet for feed consumption (FC), energy intake (EI), and EW when 6% corn oil was added to the diet. There was a significant increase in EW during the first 2 wk when hens were fed the highenergy diet. However, the hens were not as responsive after several weeks of receiving the high-energy diet. In previous experiments the dietary energy was increased 10%, and hens failed to adjust feed intake to reduce EI (Harms et al, 2000; Bohnsack et al., 2002). It was anticipated that hens would reduce feed intake by 10% when the energy was increased 10%; however, hens reduced FC only by 3%. The nutrient content of the diet was increased by 10% with the expectation of a 10% decrease in feed intake. These additional nutrients increased feed cost, partially offsetting the economic benefits of supplemental fat. Based on the fact that FC was decreased Abbreviation Key: EI = energy intake; EM = egg mass; EP = egg production; EW = egg weight, FC = feed consumption; TI = tryptophan intake. 447

2 448 ANTAR ET AL. by slightly less than 3%, only a 3% increase in amino acids would have been necessary to supply an adequate amount of amino acids. The purpose of these experiments was to examine the effects of adding 6% corn oil to the diet of commercial laying hens at various ages and with different levels of dietary Trp. MATERIALS AND METHODS All experiments were conducted in thermostatically controlled houses to obtain uniform feed intake. The temperature ranged from 23.9 to 26.7 C. All hens were housed in individual wire cages ( cm) at 18 wk of age. Feed and water were offered ad libitum. The EW from each hen was obtained weekly from the last egg produced. Average EW per replicate was recorded for weekly performance analysis. Egg production (EP) was recorded for each hen, and the replicate average of hen-day EP was calculated for weekly performance analysis. FC was obtained biweekly. Egg mass (EM) was calculated by multiplying EW times EP. Trp and EI intakes were calculated by multiplying the dietary contents of each by the amount of feed consumed. The amount of Trp and energy consumed per gram of EM were calculated by dividing daily intake by EM. Body weight change was determined by comparing individual measurements taken at the beginning and end of the study. Experiment 1 Sixty-four replicate groups of 5 individually caged Hy- Line W-36 pullets were used. The experiment went from 18 to 34 wk of age. The eight treatments were used. The control (treatment 1) hens were fed a corn-soybean meal basal diet (Table 1; diet 1) throughout the entire 16-wk period. Diet 2 was formulated to contain 6% corn oil and 3% more amino acids than the control. The addition of 6% corn oil increased the energy content of the diet by 13% based on values of NRC (1994). Treatment 2 received the diet containing 6% corn oil (Table 1; diet 2) from 18 to 34 wk of age. Thereafter, at 2-wk intervals, another group of 8 replicates was changed to the diet containing 6% corn oil, forming treatments 3 to 8. Eight replicates of 5 hens were fed each diet. Comparisons were made for performance of hens fed the control diet and hens that received the corn oil at 18 wk of age (1 to 16 wk). These same comparisons were made for each treatment during the time that corn oil was added to the diet. These comparisons were made for the performance during the first 2 wk after the addition of corn oil, the last 2 wk of the experiment, and the average for the entire experiment. Also, a comparison was made for the average of control and average of all treatments for each period. Data were analyzed using one-way analysis of variance (SAS Institute Inc., 1982). Experiment 2 Two groups of young hens (26 wk of age) were used in experiment 1. The control group comprised the same hens fed the control diet in experiment 1. Hens fed the diet with added corn oil were the same hens on treatment 6 in experiment 1. Collection of data was started when the hens were 26 wk old. Eighty Hy-Line W-36 hens, 59 wk of age, were randomly housed and assigned to 16 groups of 5 individually caged hens at the same time that the 18-wk-old pullets were housed. These hens were fed the control diet (Table 1; diet 1) for 8 wk. Eight replicates of 5 hens continued to receive the control diet throughout the entire experiment (Table 1; diet 1). When the hens were 67 wk of age, 8 replicates were fed the diet containing 6% added corn oil (Table 1; diet 2). The experiment was terminated when the pullets and hens were 34 and 75 wk of age, respectively. Comparisons were made for performance of young and old hens fed the control diet and hens fed the diet with added corn oil during the first 2 wk after the addition of corn oil to the diet, the last 2 wk of the experiment, and for the entire experimental period. Data were analyzed using one-way analysis of variance (SAS Institute Inc., 1982). Experiment 3 Two hundred forty Hy-Line W-36 hens were randomly assigned to 48 groups of 5 individual cages. All hens were fed a corn-and-soybean-meal basal diet from 18 to 32 wk of age (Table 1; diet 5). The experiment was initiated at 32 wk of age and terminated at 40 wk of age. A 2 3 factorial arrangement of treatments was used. The treatments consisted of 2 levels of added corn oil (0 and 6%) and 3 levels of Trp (0.166, 0.176, and 0.193%) (Table 1; diets 3 to 8). Corn and soybean meal were varied to obtain the 3 levels of Trp. Met and Lys were added to the diet to ensure an adequate intake of these 2 amino acids. Eight replicates of 5 hens were fed each diet. Data for each measurement was analyzed using a 2-way analysis of variance (SAS Institute Inc., 1982). Significant differences among the 6 treatments were determined by Duncan s (1955) multiple range test. EP RESULTS AND DISCUSSION Experiment 1. During the first 2 wk that corn oil was added to the diet, EP was significantly reduced for hens switched to the corn oil diet at 18, 20, and 22 wk of age (Table 2). EP was not significantly reduced when corn oil was added to the diet at other ages. During the last 2 wk of the experiment, EP was lower for hens fed the diets with corn oil than EP from hens fed the control diet at 18, 20, 22, and 24 wk (Table 2). The EP for the entire experimental period was lower from hens fed the diet containing corn oil than EP from hens fed the control diet from 18, 20, 22, and 24 wk of age (Table 2). EP was significantly reduced when corn oil was added to the diet at 20 wk of age. Reduction of EP was evident after the corn oil was added to the diet for7d.

3 ADDITION OF CORN OIL COMMERCIAL LAYER DIETS 449 TABLE 1. Composition of diets Experiments 1 and 2 Experiment 3 Ingredient Diet 1 Diet 2 Diet 3 Diet 4 Diet 5 Diet 6 Diet 7 Diet 8 Yellow corn Soybean meal Ground limestone Dicalcium phosphate Common salt Mineral premix Vitamin premix Lysine DL-Methionine Corn oil Calculated values 4 ME (kcal/kg) 2,826 3,192 2,849 3,233 2,834 3,218 2,802 3,192 Protein (%) Calcium (%) Total phosphorus (%) Sodium (%) Met (%) Lys (%) Trp (%) Cys (%) Thr (%) Arg (%) Val (%) Ile (%) Leu (%) His (%) Contained 18.5% P and 21% Ca. 2 Supplied 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; pyroxidine, 5 mg; riboflavin, 5 mg; thiamin, 3 mg; vitamin A, 8,000 IU; vitamin B 12, 0.02 mg; vitamin E, 20 IU; vitamin K, 2 mg. 3 Supplied per kilogram of diet; copper, 10 mg; ethoxyquin, 65 mg; iodine, 2 mg; iron, 60 mg; manganese, 90 mg; selenium, 0.2 mg; zinc, 80 mg. 4 Amino acid analysis were based on analysis of corn and soybean meal. Energy content was based on NRC (1994) values. TABLE 2. Egg production, egg weight, egg mass, and feed consumption from 18 to 23 wk by hens fed a control ( ) diet and hens fed a diet with 6% corn oil (+) at various ages (experiment 1) Egg production Egg weight Egg mass Feed consumption Beginning First Last First Last First Last First Last age + or 2 2wk 3 wk 4 Avg 5 2wk 3 wk 4 Avg 5 2wk 3 wk 4 Avg 5 2wk 3 wk 4 Avg 5 (wk) (%) (g) (g) (g/hen/day) a 90.2 a 88.9 a 46.1 b 57.5 a 52.4 a 27.8 a 52.0 a 46.9 a 59.5 a 93.4 a 83.4 a b 89.8 a 87.3 a 47.7 a 56.1 a 52.3 a 27.8 a 50.5 a 45.7 a 59.4 a 79.3 c 75.0 b a 92.8 a 48.6 a 53.5 a 45.9 a 49.6 a 71.4 a 86.4 a b 89.6 a 90.7 b 48.8 a 55.7 a 52.9 a 42.3 a 50.1 a 47.9 b 63.8 b 80.2 b 76.3 b a 92.4 a 49.6 b 54.4 a 47.1 a 50.2 a 82.8 a 88.5 a b 88.8 a 90.5 a 51.4 a 57.4 a 55.0 a 48.1 a 51.1 a 49.8 a 77.7 b 79.4 c 80.7 b a 91.9 a 53.3 a 55.4 a 48.3 a 50.9 a 86.6 a 89.4 a a 88.2 a 89.6 a 52.8 a 57.1 a 55.3 a 49.0 a 50.8 a 49.6 a 77.8 b 79.0 c 78.4 b a 91.9 a 53.6 a 56.1 a 50.6 a 51.5 a 84.6 a 90.0a a 91.0 a 91.9 a 54.8 a 57.0 a 55.8 a 50.0 a 51.1 a 51.3 a 80.0 b 80.3 b 80.9 b a 91.3 a 55.3 b 56.7 a 50.8 a 51.8 a 87.9 a 91.3 a a 91.8 a 91.7 a 57.2 a 56.4 s 57.2 a 52.5 a 52.5 a 52.5 a 88.1 a 81.8 b 85.6 a a 91.3 a 57.0 a 57.2 a 52.5 a 52.2 a 90.8 a 92.5 a a 90.4 a 91.8 a 57.0 a 56.8 a 56.5 a 52.8 a 50.2 a 51.8 a 89.5 a 83.9 b 85.9 b Avg a 90.2 a 91.5 a 51.9 a 57.5 a 55.1 a 46.1 a 52.0 a 50.4 a 80.5 a 93.4 a 88.8 a a 89.9 a 90.5 a 52.8 a 56.6 a 55.0 a 45.9 a 50.9 a 49.8 a 76.6 a 80.6 b 80.4 b (%) a c Means with the same superscripts within a column do not differ significantly (P > 0.05) 1 Age at which corn oil was added to the diet. 2 The control ( ) was the same hens throughout the column (treatment 1); diets containing corn oil (+) were for hens for each of the starting periods (treatments 2 through 8). 3 Performance of hens during the first 2 wk after addition of 6% corn oil. 4 Performance of hens during the last 2 wk of the study. 5 Avg = average. Performance of hens over the entire experimental period. 6 An average of the control ( ) and 6% corn oil (+) in each column.

4 450 ANTAR ET AL. TABLE 3. Performance of young (26 wk) and old (67 wk) hens fed with and without addition of 6% corn oil to the diet Young hen (26 wk of age) Old hens (67 wk of age) Week of measurement Control +6% Corn Oil Control +6% Corn Oil Egg production (%) First 2 wk a 92.1 a 83.0 a 82.1 a Last wk a 91.0 a 79.0 a 77.9 a Average a 91.9 a 81.2 a 80.3 a Egg weight (g) First 2 wk a 54.8 a 62.5 b 65.2 a Last wk a 57.0 a 64.1 b 65.8 a Average a 55.8 a 63.4 a 65.2 a Egg mass (g) First 2 wk a 50.0 a 51.8 a 53.5 a Last wk a 51.1 a 50.8 a 51.3 a Average a 51.3 a 51.5 a 52.4 a Feed consumption (g/hen/day) First 2 wk a 80.0 b 92.7 a 93.6 a Last wk a 80.3 b 97.6 a 86.7 b Average a 80.9 b 92.8 a 88.1 b Energy intake (kcal) First 2 wk a 253 a 263 b 300 a Last wk a 257 a 276 a 277 a Average a 259 a 265 b 280a Energy (kcal /g of egg mass) First 2 wk a 5.07 a 5.24 b 6.08 a Last wk a 4.95 b 5.45 a 5.40 a Average b 5.04 a 5.18 b 5.40 a Tryptophan intake (mg/d) First 2 wk a 139 a 159 a 165 a Last wk a 141 b 167 a 153 b Average a 142 b 160 a 154 a Tryptophan/g EM (mg/g egg mass) First 2 wk a 2.85 b 3.16 b 3.33 a Last wk a 2.73 b 3.29 a 2.97 b Average a 2.78 b 3.13 a 2.97 b BW change (g) Average a 250 a 17 a 75 a 1 Performance during the first 2 wk that the corn oil was added to the diet. 2 Performance during the last 2 wk of the experiment. 3 Overall averages for the entire experiment. a b Means with the same superscript within each age and each time period or row do not differ significantly (P > 0.05). Experiment 2. The EP was not affected during the first 2 wk when corn oil was added to the diet of young or old hens (Table 3). EP was not affected when corn oil was added to the diet during the last 2 wk of the experiment for young or old hens (Table 3). There was a small increase (0.8 %) in EP in young hens fed the diet containing corn oil and a small decrease (1.1 %) in EP in old hens fed the diet containing corn oil. The addition of corn oil to the diet during the entire experiment did not significantly affect EP for young or old hens (Table 3). Experiment 3. The EP from hens fed the diet containing the highest level of Trp with the added corn oil was significantly lower than EP from hens fed the diet containing 0.176% Trp and no added corn oil (Table 4). EP was highest from hens fed the diet containing 0.176% Trp with no added corn oil. Average EP was significantly decreased when corn oil was added to the diet of all hens. The levels of dietary Trp did not significantly affect EP. EW Experiment 1. During the first 2 wk after corn oil was added to the diet, the average EW increased 0.9 g for all treatments (Table 2). This increase in EW agreed with previous findings (Harms et al., 2000; Bohnsack et al., 2002). However, the increase in EW was much smaller in the present experiment. The increase in EW was only significant when corn oil was added to the diet at 18, 22, and 28 wk of age. No response was observed when corn oil was added to the diet at 30 wk of age. During the last 2 wk of the experiment, EW from hens fed the control diet were heavier than EW from hens fed the diets with corn oil (Table 2). Furthermore, the difference during any week was not significant. The average decrease in EW during the last 2 wk was 0.9 g. Average EW for the entire experimental period was not affected by the addition of corn oil to the diet regardless of the age at which the corn oil was added (Table 2). This finding did not agree with previous research (Harms et al., 2000; Bohnsack et al., 2002). Also, EW from hens receiving the diets with 6% corn oil was slightly reduced for the entire experimental period, except when corn oil was added to the diet at 22 and 28 wk of age. The increase in EW during the first 2 wk that corn oil was added to the diet, and the decrease in EW during

5 ADDITION OF CORN OIL COMMERCIAL LAYER DIETS 451 TABLE 4. Performance of laying hens fed 3 levels of Trp with or without 6% corn oil added to the diet Dietary level of Trp (%) Corn oil Avg 1 Egg production (%) 89.9 ab 91.3 a 90.5 ab 90.5 A ab 89.3 ab 88.1 b 88.8 B Avg A 90.3 A 89.3 A Egg weight (g) 57.9 bc 59.2 ab 57.4 c 58.1 B bc 58.9 ab 59.8 a 59.0 A Avg B 59.0 A 58.6 AB Egg mass (g) 52.0 ab 54.0 a 51.9 b 52.6 A ab 52.6 ab 52.7 ab 52.4 A Avg A 53.3 A 52.3 A Feed consumption (g/h per d) 90.4 b 95.6 a 90.7 b 92.3 A bc 86.2 bc 85.5 c 86.3 B Avg A 90.9 A 88.1 A A,B Means with the same superscripts among 3 different levels of Trp or between the treatments with (+) or without ( ) corn oil do not differ significantly (P > 0.05). a c Means with the same superscripts do not differ significantly (P > 0.05). 1 Average (Avg) of treatments with or without corn oil. 2 Average of treatments with 3 different levels of Trp. the last 2 wk of the experiment resulted in an interaction (P = ) of week diet when corn oil was added to the diet at 18 wk (Figure 1). The interaction of week and diet was also significant (P = ) when the corn oil was added to the diet at 20 wk (Figure 2). This interaction was the result of a slight increase in EW when corn oil was first added to the diet and a reduction of EW after wk 8. The interaction of week diet was not significant when corn oil was added to the diet at 22 wk (P = 0.217) or when corn oil was added to the diet at 24 wk (P = 0.187). There was no indication of an interaction during wk 26, 28, or 30, as these hens only received the corn oil diet for 8, 6, and 4 wk, respectively. Experiment 2. Two weeks after the corn oil was added to the diet, EW increased 1.2 and 2.7 g from young and old hens, respectively (Table 4). This increase in EW was significant when corn oil was added to the diet of old hens. Egg weight from young hens was not affected by adding corn oil to the diet during the last 2 wk of the experiment (Table 3). However, EW significantly increased 1.7 g when corn oil was added to the diet of old hens. Egg weight from young or old hens was not affected by the addition of corn oil to the diet during the entire experimental period (Table 3). However, there was a 0.3- g decrease in EW from young hens and a 1.8-g increase in EW from old hens when the corn oil was added to the diet. EW were heavier from old hens than from young hens for the entire experiment. Experiment 3. Egg weights increased as the level of dietary Trp increased when corn oil was added to the diet (Table 4). However, when the diet did not contain corn oil, EW increased as dietary Trp increased from to 0.176% and then decreased as Trp increased from to 0.193%. EW significantly increased (2.4 g) when corn FIGURE 1. The interaction of week diet for egg weight at 18 wk when hens were fed diets with and without corn oil. TRT = treatment. FIGURE 2. The interaction of week diet for egg weight at 20 wk when hens were fed diets with and without corn oil. TRT = treatment.

6 452 ANTAR ET AL. FIGURE 3. The interaction of Trp and egg weight for hens fed diets with and without corn oil. oil was added to the diet of hens fed the diet containing 0.193% Trp. However, EW decreased 0.3 g when corn oil was added to the diet containing 0.176% Trp. Average EW significantly increased when corn oil was added to the diet. EW was heaviest from hens fed the diet containing 0.176% Trp. The Trp corn oil interaction was significant (P = ) for EW (Figure 3). This was a result of EW increasing when corn oil was added to the diets containing 0.166% and 0.193% Trp and decreasing when corn oil was added to the diet that contained 0.176% Trp. EM Experiment 1. During the first 2 wk that corn oil was added to the diet, EM was not significantly affected (Table 2). During the last 2 wk of the experiment, there were no significant differences in EM among hens fed the 8 diets with corn oil (Table 2). EM for the entire experiment was significantly decreased when corn oil was added to the diet at 20 wk of age (Table 2). Otherwise, there were no significant differences among the treatments. Experiment 2. During the first 2 wk after corn oil was added to the diet, EM from young and old hens were not significantly affected (Table 3). However, the EM decreased when corn oil was added to the diet of young hens and increased when added to the diet of the old hens. EM was not affected by the addition of corn oil to the diet of young or old hens during the last 2 wk of the experiment (Table 3). There was a decrease in EM from young hens and an increase in EM from old hens receiving the diet with added corn oil. The addition of corn oil to the diets of young and old hens did not affect EM over the entire experimental period (Table 3). There was a decrease in EM when corn oil was added to the diet of young hens and an increase in EM when corn oil was added to the diet of old hens. Experiment 3. The EM was lowest from hens fed the diet containing 0.193% Trp and no added corn oil as compared with the other treatments (Table 4). EM was not different among the hens fed diets with the 3 different levels of dietary Trp or corn oil. FC Experiment 1. During the first 2 wk that corn oil was added to the diet, FC was significantly reduced below the FC of the control hens, except at 18, 28, and 30 wk of age (Table 2). The reduction of FC was 7.6, 5.1, 8.8, and 4.6 g when corn oil was added to the diet at 20, 22, 24, and 26 wk of age, respectively. There was a reduction of only 1.3 g in FC when corn oil was added to the diet at 30 wk of age. The average decrease in FC was 3.9 g during the first 2 wk that corn oil was added to the diet. During the last 2 wk of the experiment, FC was significantly reduced at all ages (Table 2). There was an average decrease of 12.8 g in FC during the last 2 wk of the experiment. Feed consumption of all hens fed the diets with corn oil was significantly reduced for the entire experimental period (Table 2). This reduction in FC was greater than observed in previous experiments (Harms et al., 2000; Bohnsack et al., 2002). Reductions in FC for the entire experimental period were 8.4, 10.1, 7.8, 11, and 9.1 g when corn oil was added to the diet at 18, 20, 22, 24, and 26 wk of age, respectively, compared with FC of hens fed the control diet. The decreases in FC were only 5.7 and 6.6 g when corn oil was added to the diet at 28 and 30 wk of age, respectively. Average FC for all hens fed the diet containing corn oil was 8.4 g less than FC of hens fed the control diet. Experiment 2. During the first 2 wk that corn oil was added to the diet, FC was significantly reduced in young hens but not in old hens (Table 3). FC significantly decreased during the last 2 wk of the experiment for young and old hens receiving corn oil in the diet (Table 3). During this period, FC decreased 13.1 and 10.9 g in young and old hens, respectively. When corn oil was added to the diet, FC was significantly reduced for young and old hens during the entire experimental period (Table 3). This reduction was 9.1 and 4.7 g in young and old hens, respectively. Experiment 3. Feed consumption was significantly higher from the hens fed diets with 0.176% Trp and no added corn oil than FC from hens fed other diets (Table 4). Average FC was significantly lowered (6 g) when corn oil was added to the diets of all hens. However, there were no significant differences in FC among hens fed the diets containing different levels of dietary Trp. EI Experiment 1. Daily EI increased during the first 2 wk that corn oil was added to the diet, regardless of the age at which corn oil was added (Table 5). This increase was significant (P < 0.05) when corn oil was added at 18, 28, and 30 wk of age. The average increase in EI for all hens fed the diet containing corn oil was 16 kcal during the first 2 wk that corn oil was added to the diet. The EI decreased during the last 2 wk of the experiment when corn oil was added to the diet (Table 5), which

7 ADDITION OF CORN OIL COMMERCIAL LAYER DIETS 453 TABLE 5. Energy intake, energy per gram of egg mass (EM), Trp intake, and Trp per gram of egg mass from hens fed a control ( ) diet or a diet with 6% corn oil (+) at various ages (experiment 1) Energy intake Energy g/ EM Tryptophan intake Trp/g EM Beginning First Last First Last First Last First Last BW age 1 +or 2 2wk 3 wk 4 Avg 5 2wk 3 wk 4 Avg 5 2wk 3 wk 4 Avg 5 2wk 3 wk 4 Avg 5 gain (kcal/d) (kcal/d) (mg) (mg) (wk) (g) b 265 a 236 a 6.08 b 5.10 a 5.04 b 102 a 160 a 143 a 3.67 a 3.08 a 3.04 a 283 a a 254 a 240 a 3.83 a 5.02 a 5.25 a 104 a 140 b 132 b 3.74 a 2.76 b 2.89 b 283 a a 256 a 245 a 4.40 b 4.93 b 122 a 148 a 2.65 a 2.98 a a 244 a 4.72 a 5.12 a 5.09 a 112 b 141 b 134 b 2.59 a 2.82 b 2.80 b 262 a a 258 a 251 a 4.96 b 4.99 b 141 a 151 a 2.99 a 3.01 a a 259 a 5.16 a 5.05 a 5.20 a 129 b 139 b 142 b 2.68 b 2.78 b 2.86 b 306 a a 253 a 253 a 5.07 a 4.98 a 148 a 153 a 3.06 a 3.01 a a 251 a 5.08 a 4.95 a 5.06 a 133 b 141 b 137 b 2.71 b 2.71 b 2.77 b 239 a a 257 a 255 a 4.74 b 4.95 a 145 a 154 a 2.97 a 2.99 a a 259 a 5.07 a 4.95 a 5.04 a 139 a 144 b 142 b 2.85 b 2.73 b 2.78 b 250 a b 261 a 259 b 4.92 b 5.00 b 151 a 156 a 3.06 a 3.02 a a 274 a 5.52 a 4.97 a 5.22 a 155 a 144 b 151 a 2.89 a 2.74 b 2.87 b 268 a b 268 a 262 b 5.06 b 5.02 b 155 a 158 a 3.04 a 3.03 a a 275 a 5.70 a 5.28 a 5.30 a 153 a 144 b 147 b 3.05 a 2.82 b 2.83 b 238 a Avg a 265 a 252 a 5.03 a 5.10 a 4.98 b 138 a 160 a 152 a 3.06 a 3.08 a 3.01 a a 258 a 257 a 5.44 a 5.05 a 5.17 a 132 a 141 b 141 b 2.93 a 2.78 b 2.83 b 273 a 1 Age at which corn oil was added to the diet. 2 Control ( ) or diet containing 6% corn oil (+). 3 Performance of hens during the first 2 wk after the addition of 6% corn oil. 4 Perfromance of hens during last 2 wk of the study. 5 Avg = average. Performance of hens over the entire experimental period. 6 An average of the control ( ) and 6% corn oil (+) in each column. a,b Means with the same superscripts within a column do not differ significantly (P > 0.05). resulted in a small, nonsignificant decrease in EI of 7 kcal of ME per day (Table 5). The EI for the entire experimental period was not significantly affected when corn oil was added to the diet at 18, 20, 22, 24, or 26 wk of age (Table 5). However, the EI for the entire experimental period was significantly increased when corn oil was added to the diet at 28 and 30 wk of age. This increase in energy was not as great as was observed in previous findings at our laboratory (Harms et al., 2000; Bohnsack et al., 2002). Experiment 2. The EI was not affected during the first 2 wk when corn oil was added to the diets of young hens but was significantly increased when corn oil was added to the diets of old hens due to an increase in FC (Table 3). When corn oil was added to the diet, EI increased 13 and 37 kcal in young and old hens, respectively. During the last 2 wk of the experimental period, EI was not affected by the addition of corn oil to the diet of young or old hens (Table 3). EI for the entire experimental period was not affected by the addition of corn oil to the diets of young hens but was significantly increased when corn oil was added to the diets of old hens (Table 3). Experiment 3. The EI was significantly lower in hens fed the diets with and 0.193% dietary Trp and no added corn oil than EI from hens fed other diets (Table 6). EI was greatest from hens fed the diet containing 0.166% dietary Trp with added corn oil. There were no significant differences in EI when the hens were fed different levels of Trp. However, EI was significantly higher when corn oil was added to the diet of the laying hen. Energy Per Gram of EM Experiment 1. During the first 2 wk that corn oil was added to the diet, the energy per gram of EM increased (Table 5). This increase (P < 0.05) was for all ages except when corn oil was added to the diet at 24 wk of age. The energy per gram of EM during the last 2 wk of the experimental period was not different among the treatments (Table 5). However, the energy per gram of EM for the entire experimental period was significantly (P < 0.05) increased when corn oil was added to the diet at all ages except at 24 and 26 wk (Table 5). Experiment 2. Energy per gram of EM of young hens was not affected during the first 2 wk following the addition of corn oil to the diet but was significantly increased when corn oil was added to the diets of old hens (Table 3). During the last 2 wk of the experiment, energy per gram of EM significantly decreased when corn oil was added to the diet of young hens but was not significantly affected when corn oil was added to the diet of old hens (Table 3). Energy per gram of EM significantly increased when corn oil was added to the diet of young and old hens for the entire experiment. Experiment 3. Energy per gram of EM was lower from hens that were fed the diet containing no added corn oil than from hens that were fed diets with added corn oil (Table 6). Average energy per gram of EM significantly increased (0.34 kcal) when corn oil was added to the diet. Energy per gram of EM was more when hens received the diets with 0.166% Trp compared with hens fed the diet with 0.193% Trp.

8 454 ANTAR ET AL. TABLE 6. Performance of laying hens fed the three levels of Trp with or without 6% corn oil added to the diet Dietary level of Trp (%) Corn oil Avg 1 Trp Intake Energy intake (kcal/h/d) 258 b 271 a 255 b 261 B a 277 a 273 a 277 A Avg A 274 A 264 A Energy/g of egg mass (kcal/g) 4.96 d 5.02 cd 4.91 d 4.96 B a 5.29 ab 5.18 bc 5.30 A Avg A 5.15 AB 5.05 B Tryptophan intake (mg) 150 c 163 b 175 a 164 A c 151 c 165 ab 154 B Avg C 160 B 170 A Trp per gram of egg mass (mg/g) 2.89 c 3.12 b 3.38 a 3.11 A d 2.90 c 3.13 b 2.91 B Avg C 2.97 B 3.26 A BW Gain (g) 26 c 9 bc 2 bc 5 B + 53 a 34 ab 55 a 48 A Avg 2 14 A 22 A 29 A a d Means with the same superscripts do not differ significantly (P > 0.05). A C Means with the same superscripts among the three different levels of Tryptophan or between the treatments with or without corn oil do not differ significantly (P > 0.05). 1 Average (vg) of treatments with or without corn oil. 2 Average of treatments with 3 different levels of Trp. Experiment 1. Tryptophan intake (TI) was reduced during the first 2 wk that the corn oil was added to the diet at all ages except when corn oil was added to the diet at 18 and 28 wk of age. These reductions were significant (P < 0.05) only at 20, 22, and 24 wk of age (Table 5). During the last 2 wk of the experimental period, TI was significantly reduced at all ages when corn oil was added to the diet (Table 5). The daily TI for the entire experimental period was significantly reduced when corn oil was added to the diet at all ages, except when corn oil was added to the diet at 28 wk of age (Table 5). Experiment 2. The TI was not affected during the first 2 wk after the addition of corn oil to the diet of young or old hens (Table 3). However, TI was significantly reduced when corn oil was added to the diet during the last 2 wk of the experiment in young and old hens (Table 3). The TI was reduced during the entire experimental period when corn oil was added to the diet of young and old hens but was only (P < 0.05) in young hens (Table 3). This reduction was 12 and 6 mg in young and old hens, respectively. Experiment 3. The TI was lower from hens fed the diet containing 0.166% Trp with added corn oil than TI for hens fed the other 5 diets (Table 6). TI significantly decreased each time corn oil was added to the diet. Hens receiving the diet with 0.193% Trp with added corn oil had the highest intake of Trp. Trp Per Gram of EM Experiment 1. The Trp per gram EM was significantly reduced during the first 2 wk that corn oil was added to the diet at 22, 24, and 26 wk (Table 5). There was a nonsignificant reduction in Trp per gram of EM when corn oil was added at 20 and 28 wk of age. During the last 2 wk of the experiment, the TI per gram of EM was significantly reduced each time corn oil was added to the diet (Table 5). The Trp per gram EM for the entire experimental period was significantly reduced when corn oil was added to the diet at all ages (Table 5). Experiment 2. Tryptophan per gram of EM was significantly reduced during the first 2 wk that corn oil was added to the diet of young hens (Table 3). However, Trp per gram of EM significantly increased during the first 2 wk when corn oil was added to the diet of old hens. During the last 2 wk of the experiment, Trp per gram of EM significantly decreased in young and old hens receiving the diet containing corn oil (Table 3). Trp per gram of EM was significantly reduced when young and old hens received the diet containing corn oil during the entire experimental period. Experiment 3. Tryptophan per gram of EM was significantly lower from hens fed the diet containing 0.166% Trp with added corn oil than Trp per gram of EM from hens fed the other five diets (Table 6). Trp per gram of EM was significantly lower when corn oil was added to the diet and was significantly increased as the level of dietary Trp increased.

9 ADDITION OF CORN OIL COMMERCIAL LAYER DIETS 455 BW Change Experiment 1. Body weight change was not affected by the addition of corn oil to the diet at any age (Table 5). However, hens that received the corn oil diet gained more than the control hens. Experiment 2. Body weight gain was greater in old hens than in the young hens when corn oil was added to the diet (Table 3). The addition of corn oil to the diet did not change BW gain with young or old hens. Experiment 3. Body weight gain was increased each time corn oil was added to the diet (Table 6). The level of dietary Trp did not affect BW gain. The addition of 6% corn oil to the diets in all 3 experiments resulted in increased EW during the first 2 wk that corn oil was added to the diet. However, EW decreased during the last 2 wk. In the first experiment, this increase and decrease in EW resulted in an interaction when corn oil was added to the diet at 18 wk (P = ) and at 20 wk (P = ). EP was not affected by the addition of corn oil in most cases. A lack of a consistent response when corn oil was added to the diet does not agree with previous findings (Harms et al., 2000; Bohnsack et al., 2002). However, the increase in EW during the first 2 wk in the first experiment does agree with earlier data. Also, the increase in EW from old hens in the second experiment and increase in EW from hens when corn oil was added to the diet containing 0.193% Trp agrees with previous findings (Harms et al., 2000; Bohnsack et al., 2002). The EW increased when the daily TI was greater than or equal to the requirement in these experiments. Also, when the diet did contain enough Trp, there was a decrease in EW when corn oil was added. In experiment 3 Met and Lys were added when Trp was increased. More studies need to be conducted to determine the amino acid level of the diet necessary to increase EW when corn oil is added to the diet. The daily amino acid need increased when EM increased as a result of increased EM. REFERENCES Bohnsack, C. R., R. H. Harms, W. D. Merkel, and G. B. Russell Performance of commercial layers when fed diets with four levels of corn oil or poultry fat. J. Appl. Poult. Res. 11: Combs, G. F., and N. V. Helbacka Studies with laying hens 1: Effect of dietary fat,protein levels and other variables in practical rations. Poult. Sci. 39: Duncan, D. B Multiple range and multiple F tests. Biometrics 11:1 42. Harms, R.H., G.B. Russell, and D.R. Sloan Performance of four strains of commercial layers with major changes in dietary energy. J. Appl. Poult. Res. 9: Hochreich, H. J., C. R. Douglas, I. H. Kidd, and R. H. Harms The effect of dietary protein and energy levels upon production of Single Comb White Leghorn hens. Poult. Sci. 37: Jensen, L. S., J. B. Allred, R. E. Fry, and J. McGinnis Studies on an unidentified factor necessary for maximum egg weight. Poult. Sci. 36:1130. (Abstr.) Marion, J. E., and H. M. Edwards, Jr The response of laying hens to dietary oils and purified fatty acids. Poult. Sci. 43: National Research Council Nutrient Requirements of Poultry. 9th rev. ed. National Academy Press, Washington, DC. SAS Institute SAS User s Guide: Statistics. SAS Institute Inc., Cary, NC.