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Effect of acute heat stress on amino acid digestibility in laying hens
Research Notes Effect of Acute Heat Stress on Amino Acid Digestibility in Laying Hens1 K. W. KOELKEBECK,2 C. M. PARSONS, and X. WANG Department of Animal Sciences, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801 ABSTRACT An experiment was conducted to determine the effect of acute heat stress exposure on amino acid digestibility in laying hens. A total of 30 commercial laying hens were singly housed in an environmentally controlled facility, fed a standard laying ration, and exposed to a constant thermoneutral temperature (21 C) for 12 d. The hens were then randomly fed one of three diets (10 hens per diet) and exposed to three consecutive temperature periods (8 d each), which consisted of: 1) a constant 21 C temperature, 2) a cycling temperature of 35 C for 12 h and 29 C for 12 h, and 3) a constant 21 C temperature. The three isonitrogenous (18% CP) diets fed were: 1) a corn-soybean meal diet, 2) a corn-soybean meal diet containing 15% meat and bone meal, and 3) a corn-soybean meal diet containing 5% alfalfa meal and 20% wheat bran. Excreta were collected from all hens
during the last 4 d of each temperature period and apparent amino acid digestibility was determined. There was a significant diet effect (P < 0.05) on amino acid digestibility. Digestibility of amino acids in Diet 2 (corn-soybean meal/meat and bone meal) was higher (P < 0.05) than in the other two diets. In addition, digestibility of amino acids in Diet 3 (corn-soybean meal/alfalfa meal/wheat bran) was significantly lower (P < 0.05) than in Diets 1 or 2. Heat stress generally had no significant effect on amino acid digestibility except for His and Lys digestibility. Histidine digestibility was higher during the heat stress period than during the initial and recovery thermoneutral periods, whereas Lys digestibility was higher during the heat stress period than during the initial thermoneutral period. These results indicated that acute heat stress (8 d) had no adverse effects on dietary amino acid digestibility in laying hens.
(Key words: layer, amino acid digestibility, high fiber diet, meat and bone meal, heat stress) 1998 Poultry Science 77:1393–1396
INTRODUCTION High environmental temperatures have deleterious effects on growth and production performance of poultry. In broilers, it has been shown that decreased rate of growth occurs (Howlider and Rose, 1987) when environmental temperature rises. In laying hens, heat stress depresses egg production (Marsden et al., 1987) and egg weight (Peguri and Coon, 1991). This negative effect of heat stress on growth rate and production is probably primarily due to reduced feed intake for broilers (Hurwitz et al., 1980) and laying hens (Savory, 1986). However, some earlier studies suggested that the dietary availability of nutrients such as amino acids may also be reduced by heat stress. In a recent study by Zuprizal et al. (1993), they found that the true digestibilities of 12 amino acids were generally depressed in two
Received for publication November 14, 1997. Accepted for publication March 31, 1998. 1Supported by Illinois Agricultural Experiment Station Hatch Project ILLU-35-0327. 2To whom correspondence should be addressed: 282 Animal Sciences Laboratory, 1207 W. Gregory Drive, Urbana, IL 61801, e-mail: [email protected]
rape seed and two soybean meal diets when fed to broilers subjected to an increasing ambient temperature exposure from 21 to 32 C. In an earlier study, Wallis and Balnave (1984) found that the influence of environmental temperature on amino acid digestibility was sexrelated, with high temperatures decreasing digestibility of amino acids in female but not male broilers. The results of these two studies suggest that digestibilities of amino acids may be reduced in broiler chickens during periods of heat stress. To our knowledge, no such research has been conducted with laying hens. Therefore, the purpose of this study was to determine the digestibility of amino acids for laying hens fed three different diets during an acute exposure to heat stress conditions.
MATERIALS AND METHODS A total of 30 commercial White Leghorn hens at the end of their first laying cycle (61 wk of age) were moved from a cage layer facility of commercial design and singly housed in an environmentally controlled facility. They were each fed an 18% CP standard layer ration (Table 1, Diet 1) and provided water for ad libitum intake. A 17-h daily photoperiod was maintained
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KOELKEBECK ET AL. TABLE 1. Composition of experimental diets Diet Ingredients and analysis
Corn-SBM
Corn-SBM + MBM
Corn-SBM + ALF + WB
Corn (8.0% CP) Dehulled soybean meal (SBM) (48% CP) Meat and bone meal (MBM) (45% CP) Alfalfa meal (ALF) (17% CP) Wheat bran (WB) (15.5% CP) Limestone Dicalcium phosphate Iodized salt Vitamin mix1 Trace mineral mix2 Chromix oxide Calculated analysis CP Calcium Available phosphorus
59.41 29.43 . . . . . . . . . 8.48 1.73 0.30 0.20 0.15 0.30
66.27 12.22 15.00 . . . . . . 5.56 . . . 0.30 0.20 0.15 0.30
39.97 24.12 . . . 5.00 20.00 8.31 1.65 0.30 0.20 0.15 0.30
18.00 3.80 0.45
18.00 3.80 0.45
18.00 3.80 0.45
(%)
1Supplied per kilogram of diet: vitamin A, 4,400 IU; cholecalciferol, 1,000 IU; vitamin E, 11 IU; vitamin B , 12 0.011 mg; riboflavin, 4.4 mg; d-pantothenic acid, 10 mg; niacin, 22 mg; menadione sodium bisulfate complex, 2.33 mg. 2Supplied per kilogram of diet: manganese, 75 mg; iron, 75 mg; zinc, 75 mg; copper, 5 mg; iodine, 0.75 mg.
throughout the experiment. The hens were exposed to a constant thermoneutral temperature of 21 C for a 12-d adjustment period. At the end of this adjustment period, the hens were randomly fed one of three diets (10 hens per diet) and exposed to three consecutive temperature periods (8 d each), which consisted of: 1) a constant 21 C temperature; 2) a daily cycling temperature of 35 C for 12 h and 29 C for 12 h; and 3) a constant 21 C temperature. The three isonitrogenous (18% CP) diets were fed for the 24-d experimental period and consisted of: 1) a corn-soybean meal diet, 2) a cornsoybean meal diet containing 15% meat and bone meal, and 3) a corn-soybean meal diet containing 5% alfalfa meal and 20% wheat bran (Table 1). These three diets were chosen to determine whether the effect of heat stress might be influenced by diet composition; thus, the diets varied in amount of plant vs animal protein and fiber content. It was anticipated that the hens would consume about 90 g of feed per bird per d during the heat stress period and thus, the hens were fed 90 g/d during the first thermoneutral period and consumed feed ad libitum for the next two periods. Excreta were collected from each bird for 4 h/d from 1000 to 1400 h during the last 4 d of each experimental period and freeze dried. Chromic oxide (0.30% of diet) was used as a digesta marker and Cr analyses were performed using the procedure of Williams et al. (1962). Diet and excreta samples were analyzed for amino acids using an amino acid analyzer following hydrolysis in 6 N HCl at 110 C for 24 h (Spackman et al., 1958). Methionine and cystine were determined using the performic acid oxidation method described by Moore (1963) except that the samples were diluted with water and lyophilized to remove the excess performic acid. Apparent digestibilities of 14 amino acids were then calculated.
All data were analyzed by the General Linear Models procedure (SAS Institute, 1987) for a 3 × 3 factorial arrangement of treatments (Steel and Torrie, 1980) with temperature period and diet type as main effects. Differences between individual treatment means were assessed using the least significant difference test (Steel and Torrie, 1980).
RESULTS Average feed intake of all hens during the thermoneutral, heat stress, and thermoneutral recovery periods were 89.0, 103.3, and 98.2 g per hen per d, respectively. There were no significant interaction effects of diet and temperature period on any amino acid digestibilities calculated. For all amino acid digestibilities calculated except Tyr, there was a significant diet effect (P < 0.05) (Table 2). Digestibility of Asp and Glu was higher in the corn-soybean meal diet than in the other two diets. Digestibility of Ala, Leu, Phe, Thr, and Val in the 15% meat and bone meal diet was higher (P < 0.05) than in the other two diets. Digestibility of Arg, His, Ile, Lys, and Ser were not different between the corn-soybean meal and 15% meat and bone meal diets, but both were higher (P < 0.05) than in the diet containing alfalfa meal and wheat bran. Digestibility of all but three of the amino acids was higher in the 15% meat and bone meal diet than in the diet containing alfalfa meal and wheat bran. Heat stress or temperature period generally had no significant effect on amino acid digestibility except for Lys and His (Table 2). Lysine digestibility was higher (P < 0.05) during the heat stress period than in the initial thermoneutral period. During the thermoneutral recovery period, Lys digestibility decreased slightly to a level
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RESEARCH NOTE
that was not different than during the initial thermoneutral period. Histidine digestibility was higher during the heat stress period than during the initial and recovery thermoneutral periods. Lysine and His were the only two amino acids whose digestibilities were both significantly affected by the type of diet fed and temperature exposure.
DISCUSSION The results of this study showed that acute heat stress exposure for 8 d did not have an adverse effect on amino acid digestibility in laying hens. Earlier work by Zuprizal et al. (1993) and Wallis and Balnave (1984) showed that amino acid digestibility was significantly affected when broilers were subjected to increasing ambient temperatures. In the Wallis and Balnave (1984) study, male and female broilers were exposed to a 21 or 31 C temperature period from 21 to 50 d of age (29 d) and ileal amino acid digestibility was determined. They showed that broilers exposed to a 31 C temperature produced a significant depression in Thr, Ala, Met, Ile, and Leu digestibility compared to those exposed to a 21 C temperature. Zuprizal et al. (1993) also showed that digestibility of most amino acids were significantly depressed for broilers subjected to a 32 vs a 21 C temperature period from 4 to 6 wk of age and fed either a whole rapeseed meal, a dehulled rapeseed meal, or a soybean meal diet. In addition, the effect of heat stress was more pronounced in females than in males. The reason for the lack of effect of heat stress in our study
compared to the Wallis and Balnave (1984) and Zuprizal et al. (1993) studies is unknown. However, the differences in results may be associated with type of bird used or the experimental methodology. The earlier studies used broiler chickens whereas our study used laying hens. In the Zuprizal et al. (1993) study, broilers were exposed to a 32 C constant temperature period from 4 to 6 wk of age, and then the birds were force-fed a single small quantity of the experimental diets. Perhaps the constant high temperature produces a greater negative effect on amino acid digestibility than a cycling temperature (29 to 35 C) such as that used in the current study. This cycling temperature was chosen to simulate typical day/night conditions. Direct observations of the hens in this study revealed that gular flutter and rapid panting occurred during the heat stress period. The primary effect of diet type was that the amino acid digestibility of a high-fiber diet containing wheat bran and alfalfa meal was lower than the corn-soybean meal diet and the 15% meat and bone meal diet. The negative effect of the high-fiber diet on amino acid digestibility was not unexpected. Several studies have shown that excretion of N and amino acids are increased as dietary fiber is increased (Beames and Eggum, 1981; Parsons et al., 1983). These results indicate that feeding high-fiber diets may reduce availability of amino acids for laying hens. Because intact hens were used herein; the amino acid digestibility values for the diets may be slightly higher than values that would have been obtained with cecectomized hens (Parsons, 1986). However, the relative difference in amino acid digesti-
TABLE 2. Main effect of dietary treatment and temperature period on apparent digestibility of amino acids1 Dietary treatment
Amino acid
Corn-SBM2
Corn-SBM + MBM2
Alanine Arginine Aspartic acid Glutamic acid Histidine Isoleucine Leucine Lysine Phenylalanine Proline Serine Threonine Tyrosine Valine
84.2b 90.2a 86.1a 90.4a 87.1a 85.3a 88.7b 83.8a 88.2b 89.0ab 86.6a 82.2b 89.9a 84.9b
85.8a 89.6a 84.9b 89.6b 87.3a 86.1a 89.8a 84.6a 89.4a 90.7a 87.3a 84.1a 88.3a 86.3a
Temperature period3
Corn-SBM + ALF + WB2
TN
HS
81.0c 88.1b 84.2b 89.3b 85.7b 83.9b 86.4c 81.6b 87.0c 88.4b 84.6b 80.3c 88.6a 82.1c
83.4a 89.2a 84.9a 89.5a 86.0b 85.1a 88.0a 82.5b 87.9a 89.6a 86.2a 82.0a 89.2a 84.3a
84.2a 89.8a 85.4a 90.1a 87.7a 84.9a 88.7a 84.0a 88.3a 89.0a 86.2a 82.4a 89.6a 84.8a
(%)
a–cMeans
TN recovery
Pooled SEM
83.4a 88.9a 84.9a 89.6a 86.4b 85.2a 88.3a 83.5ab 88.3a 89.5a 86.1a 82.0a 88.0a 84.2a
0.5 0.3 0.5 0.2 0.3 0.5 0.3 0.4 0.3 0.8 0.5 0.4 0.7 0.4
(%)
within a row and dietary treatment or temperature period heading with no common superscript differ significantly (P < 0.05). acid digestibility values were determined from pooled excreta collections (4 h/d from 1000 to 1400 h) for 10 hens per diet during the last 4 d of each 8-d temperature period. For each dietary treatment value, n = 30 (10 hens × 3 temperature periods), and for each temperature period value, n = 30 (10 hens × 3 dietary treatments). Values represent the main effect of diet or temperature period and are averaged over the three temperature periods or dietary treatments. 2SBM = soybean meal, MBM = meat and bone meal, ALF = alfalfa meal, WB = wheat bran. 3Temperature periods are consecutive 8-d periods of: 1) TN (constant 21 C); 2) HS (daily cycling temperature of 35 C for 12 h and 29 C for 12 h; 3) TN recovery (constant 21 C). 1Amino
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bility among diets in cecectomized hens would likely be similar to that observed herein with intact hens. The earlier studies by Wallis and Balnave (1984) and Zuprizal et al. (1993) were conducted using intact broilers.
REFERENCES Beames, R. M., and B. O. Eggum, 1981. The effect of type and level of protein, fibre and starch on nitrogen excretion patterns in rats. Br. J. Nutr. 46:301–313. Howlider, M.A.R., and S. P. Rose, 1987. Temperature and the growth of broilers. World’s Poult. Sci. J. 43:228–237. Hurwitz, S., M. Weiselberg, U. Eisner, I. Bartov, G. Riesenfeld, M. Sharvit, A. Niv, and S. Bornstein, 1980. The energy requirements and performance of growing chickens and turkeys as affected by environmental temperature. Poultry Sci. 59:2290–2299. Marsden, A., T. R. Morris, and A. S. Cromarty, 1987. Effects of constant environmental temperatures on the performance of laying pullets. Br. Poult. Sci. 28:361–380. Moore, S., 1963. On the determination of cysteine as cysteic acid. J. Biol. Chem. 238:235–237. Parsons, C. M., 1986. Determination of digestible and available amino acids in meat meal using conventional and caecectomized roosters or chick growth assays. Br. J. Nutr. 56:227–240. Parsons, C. M., L. M. Potter, and R. D. Brown, Jr., 1983. Effects of dietary carbohydrate and of intestinal microflora on
excretion of endogenous amino acids by poultry. Poultry Sci. 62:483–489. Peguri, A., and C. Coon, 1991. Effect of temperature and dietary energy on layer performance. Poultry Sci. 70: 126–138. SAS Institute, 1987. SAS Users Guide: Statistics. Version 6.04. SAS Institute Inc., Cary, NC. Savory, J. C., 1986. Influence of ambient temperature on feeding activity parameters and digestive function in domestic fowls. Physiol. Behav. 38:353–357. Spackman, D. H., W. H. Stein, and S. Moore, 1958. Automatic recording apparatus for use in chromatography of amino acids. Anal. Chem. 30:1190–1206. Steel, R.G.D., and J. H. Torrie, 1980. Principles and Procedures of Statistics: A Biometrical Approach. 2nd ed. McGrawHill Book Co., New York, NY. Wallis, I. R., and D. Balnave, 1984. The influence of environmental temperature, age and sex on the digestibility of amino acids in growing broiler chickens. Br. Poult. Sci. 25:401–407. Williams, C. H., D. J. David, and O. Ilsmaa, 1962. The determination of chromic oxide in faeces samples by atomic absorption spectrophotometry. J. Agric. Sci. 59: 381–386. Zuprizal, M. Larbier, A. M. Chagneau, and P. A. Geraert, 1993. Influence of ambient temperature on true digestibility of protein and amino acids of rapeseed and soybean meals in broilers. Poultry Sci. 72:289–295.
during the last 4 d of each temperature period and apparent amino acid digestibility was determined. There was a significant diet effect (P < 0.05) on amino acid digestibility. Digestibility of amino acids in Diet 2 (corn-soybean meal/meat and bone meal) was higher (P < 0.05) than in the other two diets. In addition, digestibility of amino acids in Diet 3 (corn-soybean meal/alfalfa meal/wheat bran) was significantly lower (P < 0.05) than in Diets 1 or 2. Heat stress generally had no significant effect on amino acid digestibility except for His and Lys digestibility. Histidine digestibility was higher during the heat stress period than during the initial and recovery thermoneutral periods, whereas Lys digestibility was higher during the heat stress period than during the initial thermoneutral period. These results indicated that acute heat stress (8 d) had no adverse effects on dietary amino acid digestibility in laying hens.
(Key words: layer, amino acid digestibility, high fiber diet, meat and bone meal, heat stress) 1998 Poultry Science 77:1393–1396
INTRODUCTION High environmental temperatures have deleterious effects on growth and production performance of poultry. In broilers, it has been shown that decreased rate of growth occurs (Howlider and Rose, 1987) when environmental temperature rises. In laying hens, heat stress depresses egg production (Marsden et al., 1987) and egg weight (Peguri and Coon, 1991). This negative effect of heat stress on growth rate and production is probably primarily due to reduced feed intake for broilers (Hurwitz et al., 1980) and laying hens (Savory, 1986). However, some earlier studies suggested that the dietary availability of nutrients such as amino acids may also be reduced by heat stress. In a recent study by Zuprizal et al. (1993), they found that the true digestibilities of 12 amino acids were generally depressed in two
Received for publication November 14, 1997. Accepted for publication March 31, 1998. 1Supported by Illinois Agricultural Experiment Station Hatch Project ILLU-35-0327. 2To whom correspondence should be addressed: 282 Animal Sciences Laboratory, 1207 W. Gregory Drive, Urbana, IL 61801, e-mail: [email protected]
rape seed and two soybean meal diets when fed to broilers subjected to an increasing ambient temperature exposure from 21 to 32 C. In an earlier study, Wallis and Balnave (1984) found that the influence of environmental temperature on amino acid digestibility was sexrelated, with high temperatures decreasing digestibility of amino acids in female but not male broilers. The results of these two studies suggest that digestibilities of amino acids may be reduced in broiler chickens during periods of heat stress. To our knowledge, no such research has been conducted with laying hens. Therefore, the purpose of this study was to determine the digestibility of amino acids for laying hens fed three different diets during an acute exposure to heat stress conditions.
MATERIALS AND METHODS A total of 30 commercial White Leghorn hens at the end of their first laying cycle (61 wk of age) were moved from a cage layer facility of commercial design and singly housed in an environmentally controlled facility. They were each fed an 18% CP standard layer ration (Table 1, Diet 1) and provided water for ad libitum intake. A 17-h daily photoperiod was maintained
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KOELKEBECK ET AL. TABLE 1. Composition of experimental diets Diet Ingredients and analysis
Corn-SBM
Corn-SBM + MBM
Corn-SBM + ALF + WB
Corn (8.0% CP) Dehulled soybean meal (SBM) (48% CP) Meat and bone meal (MBM) (45% CP) Alfalfa meal (ALF) (17% CP) Wheat bran (WB) (15.5% CP) Limestone Dicalcium phosphate Iodized salt Vitamin mix1 Trace mineral mix2 Chromix oxide Calculated analysis CP Calcium Available phosphorus
59.41 29.43 . . . . . . . . . 8.48 1.73 0.30 0.20 0.15 0.30
66.27 12.22 15.00 . . . . . . 5.56 . . . 0.30 0.20 0.15 0.30
39.97 24.12 . . . 5.00 20.00 8.31 1.65 0.30 0.20 0.15 0.30
18.00 3.80 0.45
18.00 3.80 0.45
18.00 3.80 0.45
(%)
1Supplied per kilogram of diet: vitamin A, 4,400 IU; cholecalciferol, 1,000 IU; vitamin E, 11 IU; vitamin B , 12 0.011 mg; riboflavin, 4.4 mg; d-pantothenic acid, 10 mg; niacin, 22 mg; menadione sodium bisulfate complex, 2.33 mg. 2Supplied per kilogram of diet: manganese, 75 mg; iron, 75 mg; zinc, 75 mg; copper, 5 mg; iodine, 0.75 mg.
throughout the experiment. The hens were exposed to a constant thermoneutral temperature of 21 C for a 12-d adjustment period. At the end of this adjustment period, the hens were randomly fed one of three diets (10 hens per diet) and exposed to three consecutive temperature periods (8 d each), which consisted of: 1) a constant 21 C temperature; 2) a daily cycling temperature of 35 C for 12 h and 29 C for 12 h; and 3) a constant 21 C temperature. The three isonitrogenous (18% CP) diets were fed for the 24-d experimental period and consisted of: 1) a corn-soybean meal diet, 2) a cornsoybean meal diet containing 15% meat and bone meal, and 3) a corn-soybean meal diet containing 5% alfalfa meal and 20% wheat bran (Table 1). These three diets were chosen to determine whether the effect of heat stress might be influenced by diet composition; thus, the diets varied in amount of plant vs animal protein and fiber content. It was anticipated that the hens would consume about 90 g of feed per bird per d during the heat stress period and thus, the hens were fed 90 g/d during the first thermoneutral period and consumed feed ad libitum for the next two periods. Excreta were collected from each bird for 4 h/d from 1000 to 1400 h during the last 4 d of each experimental period and freeze dried. Chromic oxide (0.30% of diet) was used as a digesta marker and Cr analyses were performed using the procedure of Williams et al. (1962). Diet and excreta samples were analyzed for amino acids using an amino acid analyzer following hydrolysis in 6 N HCl at 110 C for 24 h (Spackman et al., 1958). Methionine and cystine were determined using the performic acid oxidation method described by Moore (1963) except that the samples were diluted with water and lyophilized to remove the excess performic acid. Apparent digestibilities of 14 amino acids were then calculated.
All data were analyzed by the General Linear Models procedure (SAS Institute, 1987) for a 3 × 3 factorial arrangement of treatments (Steel and Torrie, 1980) with temperature period and diet type as main effects. Differences between individual treatment means were assessed using the least significant difference test (Steel and Torrie, 1980).
RESULTS Average feed intake of all hens during the thermoneutral, heat stress, and thermoneutral recovery periods were 89.0, 103.3, and 98.2 g per hen per d, respectively. There were no significant interaction effects of diet and temperature period on any amino acid digestibilities calculated. For all amino acid digestibilities calculated except Tyr, there was a significant diet effect (P < 0.05) (Table 2). Digestibility of Asp and Glu was higher in the corn-soybean meal diet than in the other two diets. Digestibility of Ala, Leu, Phe, Thr, and Val in the 15% meat and bone meal diet was higher (P < 0.05) than in the other two diets. Digestibility of Arg, His, Ile, Lys, and Ser were not different between the corn-soybean meal and 15% meat and bone meal diets, but both were higher (P < 0.05) than in the diet containing alfalfa meal and wheat bran. Digestibility of all but three of the amino acids was higher in the 15% meat and bone meal diet than in the diet containing alfalfa meal and wheat bran. Heat stress or temperature period generally had no significant effect on amino acid digestibility except for Lys and His (Table 2). Lysine digestibility was higher (P < 0.05) during the heat stress period than in the initial thermoneutral period. During the thermoneutral recovery period, Lys digestibility decreased slightly to a level
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RESEARCH NOTE
that was not different than during the initial thermoneutral period. Histidine digestibility was higher during the heat stress period than during the initial and recovery thermoneutral periods. Lysine and His were the only two amino acids whose digestibilities were both significantly affected by the type of diet fed and temperature exposure.
DISCUSSION The results of this study showed that acute heat stress exposure for 8 d did not have an adverse effect on amino acid digestibility in laying hens. Earlier work by Zuprizal et al. (1993) and Wallis and Balnave (1984) showed that amino acid digestibility was significantly affected when broilers were subjected to increasing ambient temperatures. In the Wallis and Balnave (1984) study, male and female broilers were exposed to a 21 or 31 C temperature period from 21 to 50 d of age (29 d) and ileal amino acid digestibility was determined. They showed that broilers exposed to a 31 C temperature produced a significant depression in Thr, Ala, Met, Ile, and Leu digestibility compared to those exposed to a 21 C temperature. Zuprizal et al. (1993) also showed that digestibility of most amino acids were significantly depressed for broilers subjected to a 32 vs a 21 C temperature period from 4 to 6 wk of age and fed either a whole rapeseed meal, a dehulled rapeseed meal, or a soybean meal diet. In addition, the effect of heat stress was more pronounced in females than in males. The reason for the lack of effect of heat stress in our study
compared to the Wallis and Balnave (1984) and Zuprizal et al. (1993) studies is unknown. However, the differences in results may be associated with type of bird used or the experimental methodology. The earlier studies used broiler chickens whereas our study used laying hens. In the Zuprizal et al. (1993) study, broilers were exposed to a 32 C constant temperature period from 4 to 6 wk of age, and then the birds were force-fed a single small quantity of the experimental diets. Perhaps the constant high temperature produces a greater negative effect on amino acid digestibility than a cycling temperature (29 to 35 C) such as that used in the current study. This cycling temperature was chosen to simulate typical day/night conditions. Direct observations of the hens in this study revealed that gular flutter and rapid panting occurred during the heat stress period. The primary effect of diet type was that the amino acid digestibility of a high-fiber diet containing wheat bran and alfalfa meal was lower than the corn-soybean meal diet and the 15% meat and bone meal diet. The negative effect of the high-fiber diet on amino acid digestibility was not unexpected. Several studies have shown that excretion of N and amino acids are increased as dietary fiber is increased (Beames and Eggum, 1981; Parsons et al., 1983). These results indicate that feeding high-fiber diets may reduce availability of amino acids for laying hens. Because intact hens were used herein; the amino acid digestibility values for the diets may be slightly higher than values that would have been obtained with cecectomized hens (Parsons, 1986). However, the relative difference in amino acid digesti-
TABLE 2. Main effect of dietary treatment and temperature period on apparent digestibility of amino acids1 Dietary treatment
Amino acid
Corn-SBM2
Corn-SBM + MBM2
Alanine Arginine Aspartic acid Glutamic acid Histidine Isoleucine Leucine Lysine Phenylalanine Proline Serine Threonine Tyrosine Valine
84.2b 90.2a 86.1a 90.4a 87.1a 85.3a 88.7b 83.8a 88.2b 89.0ab 86.6a 82.2b 89.9a 84.9b
85.8a 89.6a 84.9b 89.6b 87.3a 86.1a 89.8a 84.6a 89.4a 90.7a 87.3a 84.1a 88.3a 86.3a
Temperature period3
Corn-SBM + ALF + WB2
TN
HS
81.0c 88.1b 84.2b 89.3b 85.7b 83.9b 86.4c 81.6b 87.0c 88.4b 84.6b 80.3c 88.6a 82.1c
83.4a 89.2a 84.9a 89.5a 86.0b 85.1a 88.0a 82.5b 87.9a 89.6a 86.2a 82.0a 89.2a 84.3a
84.2a 89.8a 85.4a 90.1a 87.7a 84.9a 88.7a 84.0a 88.3a 89.0a 86.2a 82.4a 89.6a 84.8a
(%)
a–cMeans
TN recovery
Pooled SEM
83.4a 88.9a 84.9a 89.6a 86.4b 85.2a 88.3a 83.5ab 88.3a 89.5a 86.1a 82.0a 88.0a 84.2a
0.5 0.3 0.5 0.2 0.3 0.5 0.3 0.4 0.3 0.8 0.5 0.4 0.7 0.4
(%)
within a row and dietary treatment or temperature period heading with no common superscript differ significantly (P < 0.05). acid digestibility values were determined from pooled excreta collections (4 h/d from 1000 to 1400 h) for 10 hens per diet during the last 4 d of each 8-d temperature period. For each dietary treatment value, n = 30 (10 hens × 3 temperature periods), and for each temperature period value, n = 30 (10 hens × 3 dietary treatments). Values represent the main effect of diet or temperature period and are averaged over the three temperature periods or dietary treatments. 2SBM = soybean meal, MBM = meat and bone meal, ALF = alfalfa meal, WB = wheat bran. 3Temperature periods are consecutive 8-d periods of: 1) TN (constant 21 C); 2) HS (daily cycling temperature of 35 C for 12 h and 29 C for 12 h; 3) TN recovery (constant 21 C). 1Amino
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KOELKEBECK ET AL.
bility among diets in cecectomized hens would likely be similar to that observed herein with intact hens. The earlier studies by Wallis and Balnave (1984) and Zuprizal et al. (1993) were conducted using intact broilers.
REFERENCES Beames, R. M., and B. O. Eggum, 1981. The effect of type and level of protein, fibre and starch on nitrogen excretion patterns in rats. Br. J. Nutr. 46:301–313. Howlider, M.A.R., and S. P. Rose, 1987. Temperature and the growth of broilers. World’s Poult. Sci. J. 43:228–237. Hurwitz, S., M. Weiselberg, U. Eisner, I. Bartov, G. Riesenfeld, M. Sharvit, A. Niv, and S. Bornstein, 1980. The energy requirements and performance of growing chickens and turkeys as affected by environmental temperature. Poultry Sci. 59:2290–2299. Marsden, A., T. R. Morris, and A. S. Cromarty, 1987. Effects of constant environmental temperatures on the performance of laying pullets. Br. Poult. Sci. 28:361–380. Moore, S., 1963. On the determination of cysteine as cysteic acid. J. Biol. Chem. 238:235–237. Parsons, C. M., 1986. Determination of digestible and available amino acids in meat meal using conventional and caecectomized roosters or chick growth assays. Br. J. Nutr. 56:227–240. Parsons, C. M., L. M. Potter, and R. D. Brown, Jr., 1983. Effects of dietary carbohydrate and of intestinal microflora on
excretion of endogenous amino acids by poultry. Poultry Sci. 62:483–489. Peguri, A., and C. Coon, 1991. Effect of temperature and dietary energy on layer performance. Poultry Sci. 70: 126–138. SAS Institute, 1987. SAS Users Guide: Statistics. Version 6.04. SAS Institute Inc., Cary, NC. Savory, J. C., 1986. Influence of ambient temperature on feeding activity parameters and digestive function in domestic fowls. Physiol. Behav. 38:353–357. Spackman, D. H., W. H. Stein, and S. Moore, 1958. Automatic recording apparatus for use in chromatography of amino acids. Anal. Chem. 30:1190–1206. Steel, R.G.D., and J. H. Torrie, 1980. Principles and Procedures of Statistics: A Biometrical Approach. 2nd ed. McGrawHill Book Co., New York, NY. Wallis, I. R., and D. Balnave, 1984. The influence of environmental temperature, age and sex on the digestibility of amino acids in growing broiler chickens. Br. Poult. Sci. 25:401–407. Williams, C. H., D. J. David, and O. Ilsmaa, 1962. The determination of chromic oxide in faeces samples by atomic absorption spectrophotometry. J. Agric. Sci. 59: 381–386. Zuprizal, M. Larbier, A. M. Chagneau, and P. A. Geraert, 1993. Influence of ambient temperature on true digestibility of protein and amino acids of rapeseed and soybean meals in broilers. Poultry Sci. 72:289–295.