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Influence of dietary protein level, amino acid supplementation, and dietary energy levels on growing-finishing pig performance and carcass composition¹

B. J. Kerr^2,*, L. L. Southern, T. D. Bidner, K. G. Friesen and R. A. Easter

^* USDA-ARS Swine Odor and Manure Management Research Unit, Ames, IA 50011-3310; and Department of Animal Sciences, Louisiana State University Agricultural Center, Baton Rouge 70803; and University of Arkansas, Department of Animal Sciences, Fayetteville 72701; and and Department of Animal Sciences, University of Illinois, Urbana 61801

	Abstract

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Two experiments were conducted to determine the effects of feeding reduced-CP, AA-supplemented diets at two ambient temperatures (Exp. 1) or three levels of dietary NE (Exp. 2) on pig performance and carcass composition. In Exp. 1, 240 mixed-sex pigs were used to test whether projected differences in heat increment associated with diet composition affect pig performance. There were 10 replications of each treatment with four pigs per pen. For the 28-d trial, average initial and final BW were 28.7 kg and 47.5 kg, respectively. Pigs were maintained in a thermoneutral (23°C) or heat-stressed (33°C) environment and fed a 16% CP diet, a 12% CP diet, or a 12% CP diet supplemented with crystalline Lys, Trp, and Thr (on an as-fed basis). Pigs gained at similar rates when fed the 16% CP diet or the 12% CP diet supplemented with Lys, Trp, and Thr (P > 0.10). Pigs fed the 12% CP, AA-supplemented diet had a gain:feed similar to pigs fed the 16% CP diet when housed in the 23°C environment but had a lower gain:feed in the 33°C environment (diet x temperature, P < 0.01). In Exp. 2, 702 gilts were allotted to six treatments with nine replicates per treatment. Average initial and final BW were 25.3 and 109.7 kg, respectively. Gilts were fed two levels of CP (high CP with minimal crystalline AA supplementation or low CP with supplementation of Lys, Trp, Thr, and Met) and three levels of NE (high, medium, or low) in a 2 x 3 factorial arrangement. A four-phase feeding program was used, with diets containing apparent digestible Lys levels of 0.96, 0.75, 0.60, and 0.48% switched at a pig BW of 41.0, 58.8, and 82.3 kg, respectively. Pigs fed the low-CP, AA-supplemented diets had rates of growth and feed intake similar to pigs fed the high-CP diets. Dietary NE interacted with CP level for gain:feed (P < 0.06). A decrease in dietary NE from the highest NE level decreased gain:feed in pigs fed the high-CP diet; however, gain:feed declined in pigs fed the low-CP, AA-supplemented diet only when dietary NE was decreased to the lowest level. There was a slight reduction in longissimus area in pigs fed the low-CP diets (P < 0.08), but other estimates of carcass muscle did not differ (P > 0.10). These data suggest that pigs fed low-CP, AA-supplemented diets have performance and carcass characteristics similar to pigs fed higher levels of CP and that alterations in dietary NE do not have a discernible effect on pig performance or carcass composition.

Key Words: Amino Acids • Growing-Finishing Pigs • Net Energy • Temperature

	Introduction

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The use of low-CP, AA-supplemented diets may reduce feed costs and N excretion. However, pigs fed low-CP, AA-supplemented diets have been shown to have fatter carcasses compared with pigs fed high-CP diets (Kerr et al., 1995; Tuitoek et al., 1997b). The increased fatness in pigs fed low-CP, AA-supplemented diets may be partially due to more dietary energy being available for fat synthesis as a result of reduced energy expenditure for catabolization of excess dietary protein. Excess CP intake has been shown to increase energy expenditure (Buttery and Boorman, 1976) and impact organ size and energy metabolism (Yen, 1997; Nyachoti et al., 2000). Noblet et al. (1987) observed that pigs fed diets containing 37.5 g protein/Mcal DE had lower heat production (HP) compared with pigs fed a diet containing 45 g protein/Mcal DE. Kerr et al. (2003) reported that pigs fed a 12% CP, AA-supplemented diet had a lower HP than pigs fed a 16% CP diet. In addition, reduced plasma urea N observed in pigs fed the low-CP, AA-supplemented diet (Lopez et al., 1994; Kerr and Easter, 1995) is another indication of a reduced energy need for deaminating excess AA.

Heat increment (HI) is the amount of heat released because of the energy costs of the digestive and metabolic processes. Heat production includes the energy associated with HI, energy required for maintenance, and energy expended in response to changes in the environment (NRC, 1998). To reduce HI, heat-stressed pigs voluntarily decrease feed intake, causing a decrease in growth with little change in feed conversion (Nienaber et al., 1987). In heat stress conditions, an improved growth performance by feeding diets formulated to minimize AA excesses has been observed in chicks (Waldroup et al., 1976) and pigs (Stahly et al., 1991).

The objective of the present studies was to determine whether projected differences in the HI of diets or the NE level of the diet would affect pig growth performance and carcass traits.

	Experimental Procedures

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All experimental procedures were approved by the University of Illinois Committee on Laboratory Animal Care.

Experiment 1.
Two hundred forty, Landrace x Hampshire crossbred pigs were used to test the hypothesis that pigs will perform differently under heat stress (33.8 vs. 24.5°C) when fed diets varying in CP and crystalline AA supplementation (16% CP, 12% CP, or 12% CP + AA). Pigs were weaned at approximately 4 wk of age and fed a common diet until allotted to treatment. Pigs were housed in 1.4- x 2.3-m pens with floors that were half solid concrete and half concrete slats. The thermoneutral temperature room was equipped with two 8.8-kW natural gas heaters, whereas the heat-stress room had additional heat provided by a 17.6-kW and a 29.3-kW natural gas heater. Temperature and relative humidity were recorded continuously by a calibrated hygrothermograph located in the center of each building, 25 cm above the floor. Temperature and relative humidity for the thermoneutral and heat-stress rooms averaged 24.5°C (SD 1.71), 57.0% relative humidity (SD 6.78), and 33.8°C (SD 1.45), 37.1% relative humidity (SD 6.13), respectively. Temperature and relative humidity remained constant throughout the day. Photoperiod was regulated to provide 10 h of normal-intensity light followed by 14 h of low-intensity light. Pigs were adapted to the environmental temperature for 1 wk before initiation of dietary treatments because changes in environmental temperature can cause alterations in body water, thereby distorting short-term performance results (Morrison and Mount, 1971; Phillips et al., 1982).

Diets (Table 1) were formulated using analyzed CP, Lys, and Thr composition values for the corn and soybean meal. Nitrogen analysis of ingredients and diets were done by the macro-Kjeldahl procedure (AOAC, 1984). Lysine and Thr concentrations of the ingredients and diets were determined using ion-exchange chromatography (Beckman 119 CL Amino Acid Analyzer, Palo Alto, CA) after hydrolysis of the samples in 6 N HCl for 22 h at 100°C under a nitrogen atmosphere. Tryptophan addition to the low-CP diet was based on the expected Trp level in the corn and soybean meal calculated from tabular values of CP-to-AA ratios (NRC, 1988) and the analyzed CP level of each ingredient. Tryptophan analysis on the diets was done by ion-exchange chromatography following alkaline hydrolysis of the samples as described previously (Sato et al., 1984). Lysine, Trp, and Thr additions to the 12% CP diet were made to equal the total levels calculated to be present in the 16% CP diet. Methionine plus Cys levels were not equalized but were formulated similarly to diets used previously (Kerr and Easter, 1995; Kerr et al., 1995) to help explain differences in pig performance, carcass composition, and heat production reported in those experiments. Diets and water were provided for ad libitum consumption using a single automatic nipple drinker and a two-hole self-feeder. Dietary treatments were imposed at an average initial BW of 28.7 kg and continued for 28 d. Individual pig weights and feed disappearance were recorded biweekly to calculate ADG, ADFI, and gain:feed ratio. Following weighing on d 28, a blood sample from the jugular vein of all pigs was obtained, centrifuged for serum separation, and analyzed in triplicate for urea plus ammonia N (SUN; Kit No. 640, Sigma Diagnostics, St. Louis, MO).

Experiment 2.
Seven hundred two gilts (Hampshire x Duroc boar on Yorkshire x Landrace dams) were allotted to treatments on the basis of initial BW, 25.3 kg, to test the hypothesis that modification of dietary NE and CP would impact pig growth performance and carcass composition. Gilts were housed in a commercial, double curtain-sided facility from February to June, 1998. Pens measured 3.91 x 2.44 m, with solid concrete flooring in 40% of the pen and concrete slats in the remaining 60% of the pen. Feed and water were provided for ad libitum consumption throughout the experiment. Pen pig weights and feed disappearance were recorded at the beginning and end of the growth phase to calculate ADG, ADFI, and gain:feed ratio. Each treatment had nine replicates with 13 gilts per pen in a randomized complete block.

Gilts were fed either high-CP or reduced-CP diets and three levels of NE (high, medium, or low), resulting in a 2 x 3 factorial arrangement of treatments. The high-CP diets only had small quantities of crystalline Thr and Met supplementation. The reduced-CP diets were formulated to an apparent digestible isoleucine:Lys ratio of 0.60, which equates to approximately a 3.1 percentage unit reduction in CP, and they were supplemented with Lys, Trp, Thr, and Met. Digestible Lys (dLys) levels of 0.96, 0.75, 0.60, and 0.48% were fed for the actual weight ranges of 25.3 to 41.0, 41.0 to 58.8, 58.8 to 82.3, and 82.3 to 109.7 kg, respectively. Diets (Tables 2 to 5) were formulated on a basis of apparent digestible AA, using total AA composition of the corn and soybean meal (Kidd et al., 1996) and AA digestibility values of Southern (1991). All diets were balanced relative to dLys according to Baker (1997) to Trp:Lys, Thr:Lys, total sulfur AA:Lys, Ile:Lys, and Val:Lys ratios of 0.18, 0.67, 0.62, 0.60, and 0.68 for pigs up to 58.8 kg, and 0.19, 0.70, 0.64, 0.60, and 0.68 ratios for pigs from 58.8 to 109.7 kg. Diets were formulated on a NE basis (Noblet et al., 1994) based on analyses of feed ingredients for ether extract, ash, NDF, and ADF (AOAC, 1984), as well as starch (Thivend et al., 1972). Net energy values used for corn, soybean meal, wheat middlings, and tallow were 2,731, 2,085, 1,665, and 7,255 kcal/kg, respectively. Dietary energy levels were reduced by approximately 17 kcal NE/kg with each 1 percentage unit reduction in CP according to NE calculations of Noblet et al. (1994). Amino acid concentrations of mixed diets were determined as in Exp. 1, with Met and Cys analyzed following performic acid oxidation (AOAC, 1984).

Fat-free lean (FFLEAN) and total fat (TOFAT) were obtained by total body electrical conductivity (TOBEC) methods (Calkins et al., 1993; Higbie et al., 2002). The equations used to calculate FFLEAN and TOFAT contain the response variables that best predict either FFLEAN or TOFAT (Higbie, 1997) based on TOBEC scans of the cold (following a 24-h chill at 2°C) carcass sides. The FFLEAN was calculated as [7.005 + (8.938 x psoas muscle weight, kg) + (0.151 x TOBEC scan peak) - (0.520 x carcass temperature, °C)] (R² = 0.93) and TOFAT was calculated as [-9.528 + (1.181 x TRF, cm) + (0.660 x cold carcass side weight, kg) - (0.132 x TOBEC scan peak) + (0.465 x carcass temperature, °C)] (R² = 0.90). Percentage FFLEAN (PFFLEAN) was calculated as {[FFLEAN, kg/(CCW, kg x 2)] x 100} and percentage TOFAT (PTOFAT) was calculated as {[TOFAT, kg/(CCW, kg x 2)] x 100}. Fat-free lean in the ham (HLEAN) and total fat in the ham (HTOFAT) were obtained by TOBEC. Cold ham TOBEC scans were used to obtain HLEAN and HTOFAT. The HLEAN was calculated as [2.700 + (0.112 x TOBEC scan peak)] (R² = 0.93) and HTOFAT was calculated as [-2.189 - (0.102 x TOBEC scan peak) + (0.765 x ham weight, kg)] (R² = 0.74) (Higbie, 1997). Percentage HLEAN (PHLEAN) was calculated as [(HLEAN, kg/ham weight, kg) x 100] and percentage HTOFAT (PHTOFAT) was calculated as [(HTOFAT, kg/ham weight, kg) x 100]. Data for each response variable were analyzed by ANOVA using the GLM procedure of SAS (SAS Inst. Inc., Carey, NC), with replicate and dietary treatment included in the model. The pen of pigs was the experimental unit for all data. The PDIFF option of SAS was used to determine differences between treatment means.

	Results

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Experiment 1.
Pigs maintained in the 33°C environment consumed less feed and consequently grew at a slower rate than pigs maintained in the 23°C environment, Table 6 (P < 0.01). Pigs fed the 12% CP diet without AA supplementation grew slower than pigs fed either the 16% CP diet or the 12% CP, AA-supplemented diet (P < 0.01). There was an environmental temperature x diet interaction for gain:feed (P < 0.01). Pigs fed the 12% CP, AA-supplemented diet had a lower gain:feed compared with pigs fed the 16% CP diet when fed in the 33°C environment but similar gain:feed when fed in the 23°C environment. Pigs fed in the 33°C environment had lower concentrations of SUN than pigs fed in the 23°C environment (P < 0.01). Pigs fed the 16% CP diet had the highest level of SUN, pigs fed the 12% CP diet without AA supplementation had intermediate SUN concentrations, and pigs fed the AA-supplemented, 12% CP diet had the lowest SUN concentrations (P < 0.01).

	Discussion

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The differences in feed intake due to environmental temperature in Exp. 1 are supported by others (Stahly et al., 1979; Nienaber et al., 1985; Le Bellego et al., 2002) who reported feed intake differences of approximately 15% in pigs fed at environmental temperatures similar to those we used. In contrast, Collin et al. (2001) reported a decrease in feed intake by 30% using 23 vs. 33°C. However, their experimental period lasted only 13 d compared to the 28 d in our trial, which may have exacerbated the impact of heat on voluntary feed intake. Improved growth performance has been achieved by feeding reduced-CP, AA-supplemented diets in heat stress conditions (Waldroup et al., 1976; Stahly et al., 1979; Chewning et al., 1995), which have been related to decreased HP (Noblet et al., 1987; Le Bellego et al., 2001; Kerr et al., 2003). Thus, the reduction in feed intake due to high ambient temperature should have been less in pigs fed the reduced-CP, AA-supplemented diets. However, this was not the case. The lack of an interaction between temperature and diet on feed intake suggests little effect of low-CP, AA-supplemented diets on feed intake modification at high ambient temperatures, and consequently on ADG. Had we utilized finishing pigs, a diet x temperature interaction may have been expected because higher temperatures have a larger negative impact on feed intake at heavier BW (Quiniou et al., 2000). However, our data are supported by those of Lopez et al. (1994) and Le Bellego et al. (2002), who also reported no interaction between environmental temperature and dietary treatment on feed intake or growth rates in finishing or growing-finishing pigs, respectively.

The lack of a dietary CP effect on ADFI in Exp. 1 and in all but GR2 (41.0 to 58.8 kg) of Exp. 2 agrees with others using similar reductions in CP (Kerr et al., 1995; Knowles et al., 1998). Although numerically greater feed intakes in pigs fed-low CP, AA-supplemented diets were reported by Kerr et al. (1995), Cromwell et al. (1996), and Knowles et al. (1998), no numerical feed intake differences were noted in trials by Schoenherr (1992), Tuitoek et al. (1997a), and Smith et al. (1999). In contrast, Le Bellego et al. (2002) reported that pigs fed reduced-CP, AA-supplemented diets had lower feed intakes than pigs fed high-CP diets. Thus, in trials covering extended periods of growth, dietary CP seems to have little impact on feed intake, provided that amino acids are adequately fortified.

Dietary NE had no effect on overall ADFI in Exp. 2. Although it is well known that changes in dietary energy can have large impacts on feed intake (NRC, 1987), most of these studies have dealt with relatively large differences in dietary energy levels. In Exp. 2, the difference in dietary NE from the high NE to low NE was only 124, 118, 76, and 90 kcal NE/kg in GR1, GR2, FN1, and FN2, respectively. These differences in NE may have been too small to influence feed intake, or the variation observed in feed intake in Exp. 2 overshadowed any potential NE effect. Smith et al. (1999) reported a difference in feed intake due to dietary NE difference of 65 kcal/kg, although feed intake only differed by approximately 35 g/d. The effect of NE on pig growth from 25.3 to 41.0 kg BW suggests that pigs at this age may have been more sensitive to dietary NE and may have been in an energy-dependent phase of growth (Campbell et al., 1985). Later stages of growth were unaffected by dietary NE, which suggests that their growth curves may have leveled out so that energy was no longer limiting protein accretion. In general, changing dietary NE through adjustments of corn, SBM, wheat middlings, and tallow within this narrow energy range has no effect on growth or feed intake.

As expected, pigs in Exp. 1 fed the 12% CP diet without AA supplementation grew at a slower rate than pigs fed either the 16% CP diet or pigs fed the 12% CP diet with Lys, Trp, and Thr supplementation, regardless of environmental temperature. In both experiments, pigs fed the reduced-CP, AA-supplemented diets grew similarly to pigs fed the high-CP diets. Only during the FN2 phase of Exp. 2 did pigs fed the reduced-CP, AA-supplemented diet have any indication of slower growth than pigs fed the high-CP diet. Similar growth between pigs fed high- or reduced-CP, AA-supplemented diets has been shown previously (Kerr et al., 1995; Cromwell et al., 1996; Tuitoek et al., 1997a; Knowles et al., 1998). Smith et al. (1999), however, reported that pigs grew faster on higher CP diets.

In Exp. 1, there was an interaction between diet and temperature. Pigs fed the AA-supplemented, 12% CP diet in the 23°C environment had a feed conversion similar to pigs fed the 16% CP diet, but the pigs fed the AA-supplemented, low-CP diet had a reduced feed conversion in the 33°C environment. This response was not expected and contrary to the concept of the ability of dietary HI to affect pig performance. One might have expected that a diet containing less HI should result in equal or better feed conversion in a hot environment than a diet containing a greater amount of HI. The fact that pigs fed the unsupplemented 12% CP diet had a reduced feed conversion was fully anticipated (Kerr et al., 1995). In Exp. 2, there was an interaction between dietary CP and NE. Pigs fed the high-NE sequence of diets exhibited the best feed conversion when fed the highest CP sequence, whereas feed conversions in pigs fed the medium- and low-NE sequences were equal. In contrast, pigs fed the high-NE sequence had similar feed conversion as pigs fed the medium NE when fed the reduced-CP, AA-supplemented diets. Whether this is due to the level of wheat middlings supplemented in the medium- and low-NE diets, greater than 15%, and the lack of tallow supplementation in the two finisher diets, is unclear. Assuming we had fully accounted for both NE and AA levels in our diet formulation, the fact that pigs fed the low-CP, AA-supplemented diet had reduced feed conversion was somewhat surprising. However, other researchers also have shown that pigs fed low CP, AA-supplemented diets have reduced feed conversion than pigs fed higher levels of dietary CP (Tuitoek et al., 1997a; Knowles et al., 1998; Smith et al., 1999), whereas Lopez et al. (1994), Kerr et al. (1995), and Cromwell et al. (1996) reported equal feed conversions.

The decrease in SUN concentrations in pigs fed in the 33°C environment was expected due to a decrease in feed intake. In contrast, Lopez et al. (1994) reported an increase in SUN levels in finishing pigs maintained in a hot diurnal environment when measured on d 14, but not on d 29, even though feed intake was decreased by elevation of the environmental temperature. The decrease in SUN levels in pigs fed the 12% CP diet supplemented with Lys, Trp, and Thr indicates a reduction in the amount of excess AA being consumed and is similar to that observed by others (Lopez et al., 1994; Ward and Southern, 1995; Knowles et al., 1998).

The lack of any effect of NE on carcass composition was somewhat unexpected because diets were adjusted for NE differences due to dietary CP levels. Some difference in fat deposition might have been expected given the fact that pigs fed the high-NE diets consumed 3% more energy than pigs fed the low-NE diets. However, estimation of total energy intake over the 108-d trial approximated 18,500 kcal, which would have amounted to a difference in body fat of only 2 kg. Thus, differences in dietary NE utilized in Exp. 2 were apparently not large enough to influence carcass fatness. Smith et al. (1999) reported greater 10th-rib fat depths and lower lean percentages in ultrasound data due to increasing dietary NE, but their commercial slaughter data showed no differences in carcass characteristics due to dietary NE. Likewise, Knowles et al. (1998) reported few effects of dietary NE levels on carcass traits of pigs. However, in their data obtained from a commercial slaughter plant from the same experiment, pigs fed the intermediate level of NE had lower rates of fat gain per day, and pigs fed the lowest level of dietary NE had greater 10th-rib fat depth, but estimated lean percentage did not differ.

The impact of dietary CP on carcass composition reported in literature is variable. Schoenherr (1992), Kerr et al. (1995), Cromwell et al. (1996), and Smith et al. (1999) all reported that pigs fed the low-CP, AA-supplemented diets produced carcasses with slightly less percentage lean. In contrast, Noblet et al. (1987), Lopez et al. (1994), Tuitoek et al. (1997b), and Knowles et al. (1998) indicated little effect of dietary CP on carcass lean percentage. Excluding the Kerr et al. (1995) data, where diets may have been low in the total sulfur AA-to-Lys ratio, the reasons for these discrepancies are not clear. These different responses are especially perplexing given the fact that the current data along with Knowles et al. (1998) and Smith et al. (1999) have tried to balance the NE level of the diets for these differences in calculated NE. However, because HP is largely affected by the composition of body weight gain (Quiniou et al., 1995; van Milgen et al., 1998) and because pigs fed the high-CP diet and low-CP, AA-supplemented diets in Exp. 2 had similar gain and carcass composition, potential HI differences between diets will have little impact on overall animal performance or carcass composition.

	Implications

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The results of these experiments indicate that low-crude protein (3% reduction), amino acid-supplemented diets can be fed with no serious adverse effects on growth, gain:feed, or carcass traits. These data do not support the idea that feeding a low-crude protein, amino acid-supplemented, corn-soybean meal based diet or formulating these diets on a net energy basis will have a discernible effect on pig performance or carcass composition in pigs maintained in heat-stressed environments.

	Footnotes

² Correspondence: USDA-ARS-MWA-SOMMRU, National Swine Research and Information Center, NSRIC-2167 (phone: 515-294-0224; fax: 515-294-1209; E-mail: kerr{at}nsric.ars.usda.gov).

Received for publication January 14, 2003. Accepted for publication August 18, 2003.

	Literature Cited

Top Abstract Introduction Experimental Procedures Results Discussion Implications Literature Cited

 


AOAC. 1984. Official Methods of Analysis. 14th ed. Assoc. Offic. Anal. Chem. Washington, DC.

Baker, D. H. 1997. Ideal amino acid profiles for swine and poultry and their applications if feed formulation. BioKyowa Tech. Rev. Vol. 9. Nutri-Quest, Inc., Chesterfield, MO.

Brannaman, J. L., L. L. Christian, M. F. Rothschild, and E. A. Kline. 1984. Prediction equations for estimating lean quantity in 15- to 50-kg pigs. J. Anim. Sci. 59:991–996.[Abstract/Free Full Text]

Buttery, P. J., and K. N. Boorman. 1976. The energy efficiency of amino acid metabolism. Page 197 in Protein Metabolism and Nutrition. D. J. A. Cole, ed., Butterworths, London.

Calkins, C. R., J. C. Forrest, and J. W. Lamkey. 1993. Using total body electrical conductivity (TOBEC) and optical fat probes for estimating carcass composition. Recip. Meat Conf. Proc. 46:49–51.

Campbell, R. G., M. R. Taverner, and E. M. Curic. 1985. The influence of feeding level on the protein requirement of pigs between 20 and 45 kg live weight. Anim. Prod. 40:489–496.

Chewning, J. J., R. A. Nugent, III, P. A. Smith, C. V. Maxwell, Jr., and B. Z. deRodas. 1995. Effect of partial substitution of synthetic amino acids for soybean meal to meet the ideal protein requirement of gilts. J. Anim. Sci. 73(Suppl. 1):190. (Abstr.)

Collin, A., J. van Milgen, S. Dubois, and J. Noblet. 2001. Effect of high temperature on feeding behavior and heat production in group-housed young pigs. Br. J. Nutr. 86:63–70.[Medline]

Cromwell, G. L., M. D. Lindemann, G. R. Parker, K. M. Laurent, R. D. Coffey, H. J. Monegue, and J. R. Randolph. 1996. Low protein, amino acid supplemented diets for growing-finishing pigs. J. Anim. Sci. 74(Suppl. 1):174. (Abstr.)

Fontaine, J., and M. Eudaimon, 2000. Liquid chromatographic determination of lysine, methionine, and threonine in pure amino acids (feed grade) and premixes: collaborative study. J. AOAC Int. 83:771–783.[Medline]

Higbie, A. D. 1997. Prediction of swine body composition by total body electrical conductivity (TOBEC). M.S. Thesis. Louisiana State Univ.

Higbie, A. D., T. D. Bidner, J. O. Matthews, L. L. Southern, T. G. Page, M. A. Persica, M. B. Sanders, and C. J. Monlezun. 2002. Prediction of carcass composition by total body electrical conductivity. J. Anim. Sci. 80:113–122.[Abstract/Free Full Text]

Kerr, B. J., and R. A. Easter. 1995. Effect of feeding reduced protein, amino acid-supplemented diets on nitrogen and energy balance in grower pigs. J. Anim. Sci. 73:3000–3008.[Abstract]

Kerr, B. J., F. K. McKeith, and R. A. Easter. 1995. Effect on performance and carcass characteristics of nursery to finisher pigs fed reduced crude protein, amino acid-supplemented diets. J. Anim. Sci. 73:433–440.[Abstract]

Kerr, B. J., J. T. Yen, J. A. Nienaber, and R. A. Easter. 2003. Influences of dietary protein level, amino acid supplementation and environmental temperature on performance, body composition, organ weights and heat production of growing pigs. J. Anim. Sci. 81:1998–2007.[Abstract/Free Full Text]

Kidd, M. T., B. J. Kerr, and R. L. Wilson. 1996. Amino acid survey of ingredients may aid nutritionists. Feedstuffs 68(36):14.

Knowles, T. A., L. L. Southern, T. D. Bidner, B. J. Kerr, and K. G. Friesen. 1998. Effect of dietary fiber or fat in low-crude protein, crystalline amino acid-supplemented diets for finishing pigs. J. Anim. Sci. 76:2818–2832.[Abstract/Free Full Text]

Le Bellego, L., J. van Milgen, S. Dubois, and J. Noblet. 2001. Energy utilization of low-protein diets in growing pigs. J. Anim. Sci. 79:1259–1271.[Abstract/Free Full Text]

Le Bellego, L., J. van Milgen, and J. Noblet. 2002. Effect of high temperature and low-protein diets on the performance of growing-finishing pigs. J. Anim. Sci. 80:691–701.[Abstract/Free Full Text]

Lopez, J., R. D. Goodband, G. L. Allee, G. W. Jesse, L. J. Nelssen, M. D. Tokach, D. Spiers, and B. A. Becker. 1994. The effects of diets formulated on an ideal protein basis on growth performance, carcass characteristics, and thermal balance of finishing gilts housed in a hot, diurnal environment. J. Anim. Sci. 72:367–379.[Abstract]

Morrison, S. R., and L. E. Mount, 1971. Adaptation of growing pigs to changes in environmental temperature. Anim. Prod. 13:51–57.

Nienaber, J. A., G. L. Hahn, and J. T. Yen. 1987. Thermal environment effects on growing-finishing swine. Part I: Growth, feed intake and heat production. Trans. ASAE (Am. Soc. Agric. Eng.) 30:1772–1775.

Nienaber, J. A., M. D. Shanklin, G. L. Hahn, and R. C. Manak. 1985. Performance of neonatal and newly-weaned pigs as affected by temperature and diet. Trans. ASAE (Am. Soc. Agric. Eng.) 28:1626–1633.

Noblet, J., H. Fortune, X. S. Shi, and S. Dubois. 1994. Prediction of net energy value of feeds for growing pigs. J. Anim. Sci. 72:344–354.[Abstract]

Noblet, J., Y. Henry, and S. Dubois. 1987. Effect of amino acid balance on nutrient utilization and carcass composition of growing swine. J. Anim. Sci. 65:717–726.

NPPC. 1991. Procedures to Evaluate Market Hogs. 3rd ed. Natl. Pork Prod. Counc., Des Moines, IA.

NRC. 1998. Pages 3–15 in Nutrient Requirements of Swine. 10th rev. ed. Natl. Acad. Press, Washington, DC.

NRC. 1988. Pages 54–59 in Nutrient Requirements of Swine. 9th rev. ed. Natl. Acad. Press, Washington, DC.

NRC. 1987. Pages 25–41 in Predicting Feed Intake of Food-Producing Animals. Natl. Acad. Press, Washington, DC.

Nyachoti, C. M., C. F. M. de Lange, B. W. McBride, S. Leeson, and H. Schulze. 2000. Dietary influence on organ size and in vitro oxygen consumption by visceral organs. Livest. Prod. Sci. 65:229–237.[Medline]

Phillips, P. A., B. A. Young, and J. B. McQuitty, 1982. Live-weight, protein deposition, and digestibility responses in growing pigs exposed to low temperature. Can. J. Anim. Sci. 62:95–108.

Quiniou, N., S. Dubois, and J. Noblet. 1995. Effect of dietary crude protein level on protein and energy balances in growing pigs: comparison of two measurement methods. Livest. Prod. Sci. 41:51–61.

Quiniou, N., S. Dubois, and J. Noblet. 2000. Voluntary feed intake and feeding behavior of group-housed growing pigs are affected by ambient temperature and body weight. Livest. Prod. Sci. 63:245–253.[Medline]

Sato, H., T. Seino, T. Kobayashi, A. Murai, and Y. Yugari. 1984. Determination of the tryptophan content of feed and feedstuffs by ion-exchange liquid chromatography. Agric. Biol. Chem. 48:2961–2969.

Schoenherr, W. D. 1992. Ideal protein formulation of diets for growing-finishing pigs housed in a hot environment. J. Anim. Sci. 70(Suppl. 1):242. (Abstr.)

Smith, II, J. W., P. R. O’Quinn, R. D. Goodband, M. D. Tokach, and J. L. Nelssen. 1999. Effects of low-protein, amino acid-fortified diets formulated on a net energy basis on growth performance and carcass characteristics of finishing pigs. J. Appl. Anim. Res. 15:1–16.

Southern, L. L. 1991. Digestible Amino Acids and Digestible Amino Acid Requirements for Swine. BioKyowa Tech. Rev. Vol. 2. Nutri-Quest, Inc., Chesterfield, MO.

Stahly, T. S., G. L. Cromwell, and M. P. Aviotti. 1979. The effect of environmental temperature and dietary lysine source and level on the performance and carcass characteristics of growing swine. J. Anim. Sci. 49:1242–1251.[Abstract/Free Full Text]

Stahly, T. S., G. L. Cromwell, G. R. Robe, and J. A. Miyat. 1991. Influence of thermal environment and dietary protein regimen on the response of pigs to ractopamine. J. Anim. Sci. 69(Suppl. 1):121. (Abstr.)

Thivend, P., C. Merier, and A. Guilbot. 1972. Methods Carbohydr. Chem. 6:100–105.

Tuitoek, J. K., L. G. Young, C. F. M. de Lange, and B. J. Kerr. 1997a. The effect of reducing excess dietary amino acids on growing-finishing pig performance: an evaluation of the ideal protein concept. J. Anim. Sci. 75:1575–1583.[Abstract/Free Full Text]

Tuitoek, J. K., L. G. Young, C. F. M. de Lange, and B. J. Kerr. 1997b. Body composition and protein and fat accretion in various body components in growing gilts fed diets with different protein levels but estimated to contain similar levels of ideal protein. J. Anim. Sci. 75:1584–1590.[Abstract/Free Full Text]

van Milgen, J., J. F. Bernier, Y. Lecozler, S. Dubois, and J. Noblet. 1998. Major determinants of fasting heat production and energetic cost of activity in growing pigs of different body weight and breed/castration combination. Br. J. Nutr. 79:509–517.[Medline]

Waldroup, P. W., R. J. Mitchell, J. R. Payne, and K. R. Hazen. 1976. Performance of chicks fed diets formulated to minimize excess levels of essential amino acids. Poult. Sci. 55:243–253.[Medline]

Ward, T. L., and L. L. Southern. 1995. Sorghum amino acid-supplemented diets for the 50- to 100-kilogram pig. J. Anim. Sci. 73:1746–1753.[Abstract]

Yen, J. T. 1997. Oxygen consumption and energy flux of porcine splanchnic tissues. Pages 260–269 in Digestive Physiology in Pigs. EAAP Publ. No. 88. Saint Malo, France.

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