QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Abstract Full Text (PDF) Purchase Article View Shopping Cart Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Temim, S. Articles by Tesseraud, S. Search for Related Content PubMed PubMed Citation Articles by Temim, S. Articles by Tesseraud, S.

---

Article

Chronic Heat Exposure Alters Protein Turnover of Three Different Skeletal Muscles in Finishing Broiler Chickens Fed 20 or 25% Protein Diets^{1 ,2}

Station de Recherches Avicoles, Institut National de la Recherche Agronomique, Centre de Tours-Nouzilly, 37380 Nouzilly, France

⁴To whom correspondence should be addressed.

	ABSTRACT

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION REFERENCES

 
Heat-exposed chickens exhibit a lower growth rate and a depressed protein retention which may result from an alteration in protein metabolism. A high-protein diet seems to be beneficial under hot conditions because it tends to improve growth. Effects of high ambient temperature (32 vs. 22°C) and dietary crude protein (25 vs. 20%) on muscle protein turnover were investigated in finishing broiler chickens. At 5–6 wk of age, protein synthesis was measured in vivo in the Pectoralis major, Sartorius and Gastrocnemius muscles (flooding dose of [³H]-phenylalanine). Protein breakdown was determined in the same muscles as the difference between protein synthesis and deposition. Chronic heat stress markedly reduced protein synthesis, irrespective of muscle type (P < 0.05). This was mainly related to the lower capacity for protein synthesis (muscle RNA/Protein) (P < 0.01). Chronic heat exposure also decreased protein breakdown in the P. major and Sartorius; this effect was not observed in the Gastrocnemius. Protein synthesis was more affected than breakdown, leading to reduced protein deposition, at least in the P. major and Gastrocnemius muscles. Increasing dietary protein content had no significant impact on muscle protein turnover. Particularly at 32°C, the high-protein diet did not significantly modify either protein synthesis, ribosomal capacity or translational efficiency. However, it favored muscle protein deposition, which was probably related to reduced proteolysis. In conclusion, we showed that chronic heat exposure decreased muscle protein deposition, mainly by reducing protein synthesis. Under these conditions, the impaired protein synthesis was not restored by a 5% higher protein intake.

KEY WORDS: • muscle protein turnover • ambient temperature • dietary protein • chickens

	INTRODUCTION

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION REFERENCES

 
High environmental temperatures markedly affect broiler performance, especially between 4 and 6 wk of age (finishing period; Austic 1985 , Geraert 1991 , Geraert et al. 1996a ). Compared with pair-fed birds maintained at thermoneutrality, heat-exposed chickens have reduced growth, feed efficiency, protein retention efficiency and net protein gain (Geraert et al. 1996a ). To compensate for the depressed growth performance in hot conditions, various nutritional conditions have been investigated. Some authors have recommended a reduction in dietary protein content with suitable supplementation by essential amino acids (Austic 1985 , Waldroup et al. 1976 , Waldroup 1982 ). However, Alleman and Leclercq (1997) showed that providing a low-protein diet (16% crude protein with added lysine, methionine, threonine, arginine and valine vs. a control 20% crude protein diet as recommended by the NRC (1994) did not prevent the negative heat effects. Conversely, increasing the dietary protein level could improve growth in heat-exposed chicks (Cahaner et al. 1995 , Temim et al. 1999 ).

To our knowledge, in chickens as in other homeothermic species, few investigations have been performed to investigate the impact of ambient temperatures on protein metabolism. In rats, muscle protein synthesis and degradation were increased by cold stress (Millward et al. 1983 ). In young chicks (15-d-old), whole-body protein turnover rates were increased by lowering ambient temperature from 30 to 20°C (Aoyagi et al. 1988 ). Similarly, Hayashi et al. (1992) reported in 15-d-old chicks that the rates of myofibrillar protein turnover, estimated from 3-methylhistidine excretion, were higher at 20 than at 30°C. In tube-fed chickens aged 2 to 3 wk, muscle protein turnover rates (estimated from 3-methylhistidine excretion) were also affected by ambient temperature (Yunianto et al. 1997 ). Thus, environmental temperature influences both protein synthesis and breakdown in chicks, even with equalized food intake. However, protein metabolism has never been estimated in individual skeletal muscles, which could respond differently.

We have recently shown (Temim et al. 1999 ), in finishing broilers, a significant effect of heat on muscle ribosomal capacities (Cs)⁵ independently of feed intake. To extend these findings and to understand the regulation of protein deposition in chickens subjected to chronic heat exposure, we studied protein turnover in different skeletal muscles and the potential effect of dietary crude protein (25% vs. 20%) in these conditions. Protein synthesis and proteolysis were measured in vivo in three skeletal muscles: the Pectoralis major (breast muscle, entirely fast-twitch glycolytic fiber type), the Gastrocnemius and the Sartorius (leg muscles, mixed-fiber type).

	MATERIALS AND METHODS

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION REFERENCES

 
Animals and experimental design.

Three hundred and fifty 1-d-old male broiler chicks (ISA JV15), obtained from a local hatchery (Sicamen, Bouloire, France), were raised conventionally in battery cages in controlled environment rooms. They consumed water and a complete starter diet ad libitum (12.7 MJ metabolizable energy/kg and 220 g crude protein/kg) for the first 28 d. The ambient temperature was reduced gradually from 32 to 26°C at 21 d of age. A relative humidity of ~55% and a 23 h light, 1 h dark cycle were maintained until the end of the experiment. On d 28, birds were weighed after 4 h of food deprivation and 168 were selected and divided into four experimental groups of similar weight (1165 ± 12 g). They were then placed into individual battery cages in controlled environment rooms maintained at a constant temperature of either 22°C (thermoneutral temperature) or 32°C (high temperature). They were provided free access to a control (C) or a high-protein diet (HP) from 4 to 6 wk of age. These two diets were isocaloric and had the same amino acid proportions in relation to lysine content (compositions are given in Table 1 ). Growth performance was measured for each group (n = 25–30) throughout the experimental period (from 28 to 42 d of age). At 5–6 wk of age, five to six chicks, with growth performances close to the group mean, were used to determine muscle characteristics and rates of muscle protein turnover. All experiments were carried out with due regard to legislation governing the ethical treatment of animals, and investigators were certified by the French government for carrying out animal experiments (n° 04601).

Protein fractional synthesis rates (FSR) were measured in vivo according to the flooding-dose method (Garlick et al. 1980 and 1994). This method, previously validated in chickens by Muramatsu and Okumura (1985), has been adapted in our laboratory (Tesseraud et al. 1992 ). At 20 min before slaughter, birds that had not eaten for 4 to 6 h received a single intravenous injection (0.8 mL/100 g body weight) of a radioactive-phenylalanine solution (150 mmol/L; 1.67–1.85 kBq/L). The plasma-free [³H]-phenylalanine specific radioactivity in each group was at least 95% of that of the injected phenylalanine. Just before slaughter, the birds were anesthetized with 1 mL of Pentobarbital (intravenous injection in the leg); then they were decapitated and exsanguinated. Blood was collected in heparinized tubes which were immediately centrifuged. The left Pectoralis major, Sartorius and Gastrocnemius muscles were quickly excised, weighed, frozen in liquid nitrogen and stored at -20°C until analysis.

Analytical methods.

Analytical procedures were described previously (Tesseraud et al. 1996 ). Briefly, frozen tissues were finely pulverized in liquid N₂. The acid-soluble fraction containing free amino acids was separated from the protein precipitate (extraction in 0.2 mol/L-perchloric acid). The FSR were determined using the measurements of the free and protein-bound phenylalanine specific radioactivities after conversion into ß-phenylethylamine (Garlick et al. 1980 ). This compound was measured fluorimetrically (SFM 25 fluorimeter; Kontron Instruments, St. Quentin Yvelines, France) by a modification of the method of Suzuki and Yagi (1976) and quantified for radioactivity by liquid-scintillation counting (Tricarb 2300TR; Packard Instruments, Meriden, CT). Tissue protein content was measured according to Smith et al. (1985) by the colorimetric reaction with bicinchoninic acid (Pierce, Rockford, IL). Tissue RNA content was measured from the UV absorbance at 260 nm, with a correction for peptide material based on the UV absorbance at 232 nm, as described by Munro and Fleck (1969) . The fractional protein growth rates (FGR) were estimated from the increases in tissue-protein, as described by McDonald and Swick (1981) and Tesseraud et al. (1996) . Briefly, during the experimental period, the growth linearity was verified for each experimental group, which allowed the correlation of muscle protein content to body weight. The regressions (muscle protein mass vs. body weight) were established for each group, and calculations included the same five to six chicks per group used for synthesis measurements and additional chicks killed 2–3 d before and after protein synthesis measurements to better estimate muscle protein deposition. The tissue protein gained per day was calculated for each chick from its daily growth rate. This method provides a crude estimation of muscle protein gain. Finally, the fractional breakdown rates (FBR) were calculated as the difference between FSR and FGR.

For each studied muscle, absolute rates of protein turnover, i.e., the total amounts of protein synthesized, gained or degraded each day (ASR, AGR or ABR, respectively, in mg protein/d) were calculated by multiplying FSR, FGR or FBR by the muscle protein content present on the day of the experiment. The capacity for protein synthesis, i.e., ribosomal capacity (Cs, mg/g), was estimated as the RNA/protein ratio. The translational efficiency (kRNA) was determined by calculating the amount of protein synthesized daily (mg) per mg RNA.

Statistical methods.

Values are given as means with standard errors. The homogeneity of variance between treatments was verified by Bartlett’s test. Data were analyzed using a classical two-way ANOVA to study the effects of temperature (32 vs. 22°C), dietary crude protein (25 vs. 20%) and their interaction (StatView, 5.0 version; SAS Institute, Cary, NC). When the interaction was significant, a posthoc analysis (Student-Newman-Keuls test) was conducted to identify the difference among the groups. When not otherwise specified, the level of significance used was P < 0.05.

	RESULTS

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION REFERENCES

 
Growth performances and muscle characteristics.

Body weights and growth rates were significantly lower at 32 than at 22°C; ~ -16 and -40%, respectively, irrespective of diet (Table 2 ; P < 0.001). Muscle weights and protein and RNA contents generally were also reduced in heat-exposed birds. These reductions were more pronounced and were significant in the P. major muscle (-25, -26 and -45%, for muscle weight, protein and RNA contents, respectively; P < 0.001). RNA contents were significantly lower at 32°C than at 22°C in the Sartorius (-20%, P < 0.01) and Gastrocnemius (-25%, P < 0.001) muscles. When muscle weights were expressed relative to body weight (data not shown), the proportion of P. major was lower in hot conditions, ~ -10% (P < 0.01), whereas those of the two leg muscles were significantly greater: +11% for Sartorius (P < 0.05) and + 15% for Gastrocnemius (P < 0.01).

Muscle protein turnover.

In the P. major muscle, chronic heat exposure significantly (P < 0.001) depressed FSR (-35 and -45% for C and HP diets, respectively), Cs (~ -25% for both diets), and kRNA (-10 and -25% for C and HP diets, respectively) (Table 3 ). Similarly, the fractional rates of breakdown and gain were significantly (P < 0.001) lower under hot conditions: -45 and -60% for FBR and ~ -25% for FGR. The same result was found when the protein turnover rates were expressed in absolute rates: ASR, ABR and AGR were much lower at 32 than at 22°C (Table 3) . Because protein deposition was decreased less than protein synthesis, the efficiency of protein deposition (100 x FGR/FSR) was greater in heat-exposed chickens compared to chickens maintained at 22°C (+15 and +37%, dependent on the diet; P < 0.01). There was no significant interaction between temperature and diet, and no significant diet effect for FSR and FBR. Conversely, there was an interaction between temperature and diet for ASR (P < 0.05). Thus, ASR was increased in chickens fed the HP diet at 22°C (+21%, P < 0.05), whereas it was not affected at 32°C. There was also a weak interaction between temperature and diet for ABR (P = 0.06): ABR tended to be greater in chickens fed the HP diet at 22°C (+23%, P = 0.09) but not at 32°C. Therefore, independent of the variation in protein turnover, the HP diet improved protein deposition in the P. major muscle.

	DISCUSSION

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION REFERENCES

In the present experiment, breeding conditions and experimental procedures were selected based on previous studies (Geraert et al. 1996a , b ). The effect of chronic heat exposure was investigated by comparing two ambient temperatures (22 or 32°C) maintained for 2 wk. We used chickens in the finishing period (4- to 6-wk-old), during which they are more sensitive to higher ambient temperatures than younger birds. Under these conditions, and as expected, the negative effect of high environmental temperatures on growth performance was observed, as previously reported (Austic 1985 , Geraert 1991 , Geraert et al. 1996a , Temim et al. 1999 ). Moreover, chronic heat exposure significantly altered the weight of the P. major muscle, with a decrease in both protein and RNA contents. When expressed as a percentage of body weight, the proportion of the P. major was lower (P < 0.01) at 32°C than at 22°C but those of the Sartorius and Gastrocnemius were higher (P < 0.05; P < 0.01, respectively). Aïn Baziz et al. (1996) had observed a similar decrease in the proportion of breast muscle, with a significant increase in proportion of leg muscles in birds exposed to hot conditions. A reduced breast meat yield was also found by Howlider and Rose (1989) .

In this study, we attempted to understand the regulation of muscle protein deposition under warm conditions. In chronic heat-exposure experiments, the choice of appropriate control chickens is difficult to solve because of the heat-related decrease in food intake. To abolish the effect of food-intake reduction, two alternative techniques could be used: pair- or tube-feeding. Unfortunately, these both induce a diurnal cycling, with successive postprandial and postabsorptive states, i.e., short-term fasting. In addition, it is well-established that skeletal muscle protein synthesis is highly sensitive to short-term variation in supply (Grizard et al. 1995 ) and, as this measurement is performed at a precise chosen time, feeding ad libitum was preferred in our study. Furthermore, using the same experimental model, we previously found that the reduced food intake did not explain the whole effect of high temperature on growth performance, nitrogen retention and ribosomal capacity (Temim et al. 1999 ), i.e., there was probably a direct effect of heat exposure on these parameters. Now we have clearly shown that the fractional rates of protein synthesis are depressed by chronic heat exposure in the three muscles studied (P < 0.001 for P. major and Gastrocnemius; P < 0.01 for Sartorius). The depression in FSR was principally related to a reduced capacity for protein synthesis (~ -20%; P < 0.01), i.e., RNA content was lowered more than protein by heat stress. Translational efficiency was not significantly altered by heat exposure for the leg muscles but was for the breast tissue. The calculated fractional rate of proteolysis was clearly decreased by the hot environment at least in P. major (P < 0.001) and Sartorius (P < 0.01). So, under these conditions, muscle protein turnover was lower in heat-exposed chickens compared to those maintained at thermoneutrality. These declines in both protein synthesis and breakdown are consistent with earlier studies performed on younger birds (Aoyagi et al. 1988 , Hayashi et al. 1992 , Yunianto et al. 1997 ). In these previous studies, significant decreases in rates of whole-body or muscle protein turnover occurred when the ambient temperature was increased from ~20 to 30–32°C. However, in the current experiment, we have shown that the response in protein metabolism to heat exposure depends on the muscle studied. First, the P. major muscle was more sensitive to high ambient temperatures than the Sartorius and Gastrocnemius muscles. These differential responses may relate to the energy characteristics of these muscles and their fiber-type composition: entirely fast-twitch glycolytic fibers for P. major; mixed fiber-type for the Sartorius and Gastrocnemius muscles. Second, for P. major and Gastrocnemius muscles, protein synthesis was more affected than proteolysis under hot conditions, resulting in a lower protein deposition. Conversely, in the Sartorius muscle, the heat-related decrease in protein gain was not observed.

In the present study, increasing dietary protein content significantly improved muscle FGR: significant diet effect for the P. major muscle and significantly greater values in chickens fed the HP diet than in chickens fed the C diet, at least in hot conditions, for the Sartorius and Gastrocnemius muscles. This beneficial effect of the HP diet at 32°C is probably related to a reduced muscle protein breakdown. This observation needs to be confirmed using more direct measurements of proteolysis. In any case, at 32°C the HP diet did not significantly affect either FSR, Cs or kRNA, irrespective of muscles studied, although it compensated the heat-related reduction in protein intake: ~30.5 g protein/d both at 32°C with the HP diet and at 22°C with the C diet compared to 22.5 g protein/d at 32°C with the C diet. It may be surprising that the HP diet did not stimulate protein synthesis since this stands in contrast with data obtained under thermoneutral conditions. Indeed, when dietary protein supply was lower than the protein requirement, increasing protein intake improves skeletal muscle FSR in rats (Jepson et al. 1988 ).

It has been clearly demonstrated that an acute heat stress affects protein synthesis, i.e., changes in ribosomal gene transcription leading to lower protein synthesis capacity (Jacob 1995 ). However, prolonged heat treatment could result in some degree of thermotolerance and in a different regulation of protein synthesis. The mechanisms underlying muscle protein synthesis reductions following chronic heat exposure have not yet been established. It is worthwhile to note that in warm ambient temperatures, several metabolic and hormonal parameters are altered and they may in part contribute to the protein turnover changes. First, the reduction in protein synthesis might involve the depressed plasma amino acid concentrations observed at high ambient temperatures, particularly for the branched-chain and sulfur amino acids plus glutamine (Geraert et al. 1996b ). However, in our study, the heat-related decrease in muscle protein synthesis was not enhanced by increasing dietary protein content. Second, the lower muscle protein synthesis might originate from a failure in the energy supply to the muscle under hot conditions. Peripheral glucose uptake by muscles may be reduced; this would affect the glycolytic P. major muscle more, and this is where the largest effects on protein synthesis were noted. Finally, the heat-induced changes in endocrine profiles or in sensitivity to exogenous insulin (Geraert et al. 1996b ) may contribute to a significant modification in the hormonal control of protein metabolism. In addition, hot-temperature conditions decreased plasma triiodothyronine concentrations and increased plasma corticosterone, factors which are known to reduce protein deposition through alterations in protein turnover in birds and other species (Grizard et al. 1995 , Yunianto et al. 1997 ).

In conclusion, in finishing broiler chickens, chronic heat exposure induced a marked decrease in protein synthesis rates, as measured directly in different muscles. This was mainly related to a lower ribosomal capacity. Muscle protein turnover was lower under hot conditions than at thermoneutrality. At 32°C, protein synthesis was more affected than proteolysis, at least in the P. major and the Gastrocnemius muscles, thereby reducing muscle protein deposition. Increasing dietary protein intake under high ambient temperatures generally improved muscle protein gain, without any change in protein synthesis rate, ribosomal capacity or translational efficiency. The underlying mechanisms involved in the regulation of muscle protein turnover by nutrients and ambient temperatures require more investigation at the cellular and molecular levels.

	ACKNOWLEDGMENTS

 
The authors gratefully acknowledge M. Taouis (INRA Tours, France), G. E. Lobley and R. M. Palmer (The Rowett Research Institute, Bucksburn Aberdeen, UK) for helpful comments, and K. Gerard for his technical assistance in breeding the chickens.

	FOOTNOTES

 
¹ A preliminary report of part of this work has been published in the book of abstracts of the VIII^th International Symposium on Protein Metabolism and Nutrition, Aberdeen, UK, 1–4 September 1999, Effect of high ambient temperature and dietary protein intake on tissue protein synthesis in finishing broiler chickens by S. Temim and S. Tesseraud, p. 24.

² Funded by SYPRAM (France), an association created by the ‘Association pour le maintien de l’élevage en Bretagne,’ the ‘Syndicat National des Industriels de la Nutrition Animale’ and the ‘Syndicat des coopératives d’Aliments Composés’.

³ Supported by grant from: Ministère de l’Enseignement Supérieur et de la Recherche Scientifique d’Algérie.

⁵ Abbreviations used: ABR, absolute breakdown rate; AGR, absolute growth rate; ASR, absolute synthesis rate; C diet, control diet; Cs, capacity for protein synthesis; FBR, fractional breakdown rate; FGR, fractional growth rate; FSR, fractional synthesis rate; HP diet, high-protein diet; kRNA, translational efficiency.

Manuscript received September 27, 1999. Initial review completed November 7, 1999.

	REFERENCES

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION REFERENCES

 

1. Aïn Baziz H., Geraert P. A., Padilha J. C. F., Guillaumin S. Chronic heat exposure enhances fat deposition and modifies muscle and fat partition in broiler carcasses. Poult. Sci. 1996;75:505-513[Medline]

2. Alleman F., Leclercq B. Effect of dietary protein and environmental temperature on growth performance and water consumption of male broiler chickens. Br. Poult. Sci. 1997;38:607-610[Medline]

3. Aoyagi A., Tasaki I., Okumura J. I., Muramatsu T. Effect of low ambient temperature on protein turnover and heat production in chicks. Comp. Biochem. Physiol. 1988;89A(3):433-436

4. Austic R. E. Feeding poultry in hot and cold climates. Youssef M. K. eds. Stress Physiology in Livestock 1985:123-136 CRC Press Boca Raton, FL.

5. Cahaner A., Pinchasov Y., Nir I., Nitsan Z. Effects of dietary protein under high ambient temperature on body weight, breast meat yield and abdominal fat deposition of broiler stocks differing in growth rate and fatness. Poult. Sci. 1995;74:968-975[Medline]

6. Garlick P. J., McNurlan M. A., Essen P., Wernerman J. Measurements of tissue protein synthesis rates in vivo: critical analysis of contrasting methods. Am. J. Physiol. 1994;266:E287-E297[Abstract/Free Full Text]

7. Garlick P. J., McNurlan M. A., Preedy V. R. A rapid and convenient technique for measuring the rate of protein synthesis in tissues by injection of [3H]-Phe. Biochem. J. 1980;192:719-723[Medline]

8. Geraert P. A. Energy metabolism of broilers under hot environmental conditions (in French). INRA Prod. Anim. 1991;4:257-267

9. Geraert P. A., Padilha J. C. F., Guillaumin S. Metabolic and endocrine changes induced by chronic heat exposure in broiler chickens: growth performance, body composition and energy retention. Br. J. Nutr. 1996a;75:195-204[Medline]

10. Geraert P. A., Padilha J. C. F., Guillaumin S. Metabolic and endocrine changes induced by chronic heat exposure in broiler chickens: biological and endocrinological variables. Br. J. Nutr. 1996b;75:205-216[Medline]

11. Grizard J., Dardevet D., Papet I., Mosoni L., Patureau-Mirand P., Attaix D., Tauveron I., Bonin D., Arnal M. Nutrient regulation of skeletal muscle protein metabolism in animals. The involvement of hormones and substrates. Nutr. Res. Rev. 1995;8:67-91

12. Hayashi K., Kaneda S., Otsuka A., Tomita Y. Effects of ambient temperature and thyroxine on protein turnover and oxygen consumption in chicken squeletal muscle. Mulder R. eds. Proceeding 19^th World’s Poultry Congress 1992;vol. 2:93-96 Ponsen & Looijen Amsterdam.

13. Howlider M.A.R., Rose S. P. Rearing temperature and the meat yield of broilers. Br. Poult. Sci. 1989;30:61-67

14. Jacob S. T. Regulation of ribosomal gene transcription. Biochem. J. 1995;306:617-626

15. Jepson M. M., Bates P. C., Millward D. J. The role of insulin and thyroid hormones in the regulation of muscle growth and protein turnover in response to dietary protein in the rat. Br. J. Nutr. 1988;59:397-415[Medline]

16. McDonald M. L., Swick R. W. The effect of protein depletion and repletion on muscle-protein turnover in the chick. Biochem. J. 1981;194:811-819[Medline]

17. Millward D. J., Bates P. C., de Benoist B., Brown J. G., Cox M., Halliday D., Odedra B., Rennie M. J. Protein turnover: the nature of the phenomenon and its physiological regulation. Arnal M. Pion R. Bonin D. eds. Proceeding 4th International Symposium on Protein Metabolism and Nutrition 1983;vol. 1:69-96 INRA Publications Paris.

18. Munro H. N., Fleck A. Analysis of tissues and body fluids for nitrogenous constituents. Munro H. N. eds. Mammalian Protein Metabolism 1969;vol. 3:424-525 Academic Press New York.

19. Muramatsu T., Okumura J. Whole-body protein turnover in chicks at early stages of growth. J. Nutr. 1985;115:483-490

20. National Research Council Nutrient Requirements of Poultry 9th rev. ed. 1994 National Academy Press Washington, D.C.

21. Smith P. K., Krohn R. I., Hermanson G. T., Mallia A. K., Gartner F. H., Provenzano M. D., Fujimoto E. K., Goeke N. M., Olson B. J., Klenk D. C. Measurements of protein using bicinchoninic acid. Anal. Biochem. 1985;150:76-85[Medline]

22. Suzuki O., Yagi K. A fluorimetric assay for phenylethylamine in rat brain. Anal. Biochem. 1976;75:192-200[Medline]

23. Temim S., Chagneau A. M., Guillaumin S., Michel J., Peresson J., Geraert P. A., Tesseraud S. Effects of chronic heat exposure and protein intake on growth performance, nitrogen retention and muscle development in broiler chickens. Reprod. Nutr. Dev. 1999;39:145-156

24. Tesseraud S., Larbier M., Chagneau A. M., Geraert P. A. Effects of dietary lysine on muscle protein turnover in growing chickens. Reprod. Nutr. Dev. 1992;32:163-175

25. Tesseraud S., Peresson R., Lopes J., Chagneau A. M. Dietary lysine deficiency greatly affects muscle and liver protein turnover in growing chickens. Br. J. Nutr. 1996;75:853-865[Medline]

26. Waldroup P. W. Influence of environmental temperature on protein and amino acid needs of poultry. Fed. Proc. 1982;41:2821-2823[Medline]

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

28. Yunianto V. D., Hayashi K., Kaneda S., Ohtsuka A., Tomita Y. Effect of environmental temperature on muscle protein turnover and heat production in tube-fed broiler chickens. Br. J. Nutr. 1997;77:897-909[Medline]

This article has been cited by other articles:

				J. Gao, H. Lin, Z. G. Song, and H. C. Jiao Corticosterone Alters Meat Quality by Changing Pre-and Postslaughter Muscle Metabolism Poult. Sci., August 1, 2008; 87(8): 1609 - 1617. [Abstract] [Full Text] [PDF]

				C. Garriga, R. R. Hunter, C. Amat, J. M. Planas, M. A. Mitchell, and M. Moreto Heat stress increases apical glucose transport in the chicken jejunum Am J Physiol Regulatory Integrative Comp Physiol, January 1, 2006; 290(1): R195 - R201. [Abstract] [Full Text] [PDF]

This Article Abstract Full Text (PDF) Purchase Article View Shopping Cart Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Temim, S. Articles by Tesseraud, S. Search for Related Content PubMed PubMed Citation Articles by Temim, S. Articles by Tesseraud, S.