EFFECTS OF DIETARY SUPPLEMENTAL
L-CARNITINE AND ASCORBIC ACID ON
PERFORMANCE, CARCASS COMPOSITION AND
PLASMA L-CARNITINE CONCENTRATION OF
BROILER CHICKS REARED UNDER DIFFERENT
TEMPERATURE
L. C¸ELI˙K* and O. O¨ZTU¨RKCAN
The University of C¸ukurova,Agricultural Faculty, Department of Animal Science, Adana, Turkey
(Received 7 March 2002, accepted 14 October 2002)
The present study was initiated to determine whether dietary supplemental L-carnitine and ascorbic acid affect growth performance, carcass yield and composition, abdominal fat and plasma L-carnitine concentration of broiler chicks reared under normal and high temperature. During the experiment, two temperature regimes were employed in two experimental rooms, which were identical but different in environmental temperature. The regimes were thermoneutral (20 – 228C for 24 h) or recycling hot (34 – 368C for 8 h and 20 – 228C for 16 h). One-day-old broiler chicks (ROSS) were used in the experiment. A 2 6 2 6 2 factorial arrangement was employed with two levels (0 and 50 mg/kg) of supplemental L-carnitine and two levels (0 or 500 mg/kg) of supplemental ascorbic acid in drinking water under thermoneutral or high temperature regimes. Body weight gain was affected by high temperature. However, body weight gain was significantly improved in animals receiving supplemental L-carnitine, ascorbic acid or L-carnitine + ascorbic acid compared to animals receiving unsupplemented diet under high temperature. On the other hand, supplemental carnitine or L-carnitine + ascorbic acid reduced body weight gain under thermoneutral condition. Supplemental ascorbic acid significantly improved feed conversion efficiency, the improvement was relatively greater under high temperature. The carnitine content in the plasma was higher in the groups receiving supplemental L-carnitine and ascorbic acid under high temperature, while broilers fed supplemental L-L-carnitine and ascorbic acid had a decreased level of plasma L-carnitine concentration under normal temperature. It is concluded that dietary supplemental L-carnitine or L-carnitine + ascorbic acid may have positive effects on body weight gain, carcass weight under high temperature conditions.
Keywords: Broiler performance; Carnitine; Ascorbic acid; Environmental temperature; Blood plasma
1. INTRODUCTION
It is well documented that chicks are very sensitive to ambient temperatures over 328C. Environmental temperature during summer months is of great concern to poultry producers. Literature suggests that the advantages of dietary L-carnitine and ascorbic
*Address for correspondence: Res. Assist. L. C¸elik, C¸ukurova University, Agricultural Faculty, Department of Animal Science, 01330 Adana, Turkey. Tel: + 90.322.338.70.27; Fax: + 90.322.338.65.76; E-mail: ladine@cu.edu.tr
(T&F) GAAN031003
Arch. Anim. Nutr., 2003, Vol. 00, pp. 00 – 00
ISSN 0003-942X print; ISSN 1477-2817 online#2003 Taylor & Francis Ltd DOI: 10.1080/0003942031000086644
acid have been particularly apparent under these suboptimal conditions (Rabie et al., 1997a,b; Kutlu, 2001).
It is generally accepted that growth performance of broiler chicks is connected with their genetic constitution and environmental factors, of which nutrition is the most important. The effects of dietary L-carnitine and ascorbic acid supplementation on the performance and body composition of broiler chickens has been reported (Leibetseder, 1995; Kutlu and Forbes, 1993b, Rabie and Szila´gy, 1998).
Studies with broiler chicks by Rabie et al. (1997a,b) suggest that the effectiveness of supplemental L-carnitine improved body weight gain and reduced the abdominal fat content of broilers, although Barker and Sell (1994) were unable to confirm this observation.
The literature concerning reducing fat accumulation by dietary methods, especially using L-carnitine or ascorbic acid, provide contradictory results.
It is reported that L-carnitine (b-OH-g-N-trimethylaminobutyric acid) has two major functions. The well-established role of L-carnitine is facilitating the entry of long-chain fatty acids into mitochondria for energy-generating processes via b-oxidation. L-carnitine also facilitates removal from mitochondria of short-chain and medium-chain fatty acids that accumulate as a result of normal and abnormal metabolism (Bremer, 1983; Rebouche, 1992). Carnitine biosynthesis in animals is regulated by the diet, age, and hormonal status of the animal. Two essential amino acids (lysine and methionine), three vitamins (ascorbate, niacin, and vitamin B6), and
a metal ion (reduced iron) are required as cofactors for the enzymes involved in the metabolic pathway of L-carnitine (Bieber, 1988; Borum, 1983; Leibetseder, 1995; Rebouche 1992; Sa´ndor et al., 1983). Endogenous biosynthesis is sufficient to cover normal requirements. However, this is not the case in neonates (biosynthesis not fully developed), conditions of stress, higher performance and diets rich in fat (Rebouche, 1992; Rabie and Szila´gy, 1998). L-carnitine concentrations in animals vary according to species, tissue type and nutritional status of the animal (Rabie et al., 1997a,b).
Vitamin C is an effective antioxidant, which is essential for collagen synthesis, helps to maintain various enzymes in their required reduced form, and participates in the biosynthesis of carnitine, norepinephrine and certain neuroendocrine peptides (Henrique et al., 1998).
Invertebrates, insects, most fishes, some birds, guinea-pigs, bats and primates are not able to synthesize ascorbic acid. Thus, these animals must depend upon a dietary supply of this vitamin. In poultry, ascorbic acid has been demonstrated to be essential for growth. An ascorbic acid role in relation to the physiological response to stress in fish was also suggested (Henrique et al., 1998). The literature has also provided evidence that supplemental vitamins, especially ascorbic acid, induce a considerable alleviation of heat stress, although the improvement in growth does not completely compensate the adverse effects of high temperatures (Kutlu and Forbes, 1993a).
Theoretically, dietary L-carnitine and ascorbic acid could play a role in reducing heat stress of broilers and the deposition of undesirable fat in market poultry. We hypothesized that L-carnitine and ascorbic acid may help in improving the fattening performance and carcass weight and yield of broiler chickens.
The present study was conducted to determine whether supplemental L-carnitine and ascorbic acid in drinking water would influence growth performance and other parameters under normal temperature condition and under heat exposure.
2. MATERIALS AND METHODS 2.1. Animals and feeding
One hundred and twenty-eight, 1-day-old male broiler chicks (ROSS) obtained from a commercial hatchery were divided into eight groups of similar mean weight (39.37 g; SE 4.47), comprising 16 birds each. Standard broiler starter (230 g/kg CP and 12.8 MJ/kg, from 1 – 3 weeks) and finisher (215 g/kg CP and 13.2 MJ/kg, from 4 – 6 weeks at trial) diets were produced by a commercial feed company. The composition and chemical analyses of the starter and finisher diets are presented in Table I. The L-carnitine contents were 7.14 mg/kg and 14.6 mg/kg in the starter and finisher diets, respectively. A 2 6 2 6 2 factorial arrangement was employed with two levels (0 and 50 mg/kg) supplemental L-carnitine and two levels (0 or 500 mg/ kg) of supplemental ascorbic acid in the drinking water under thermoneutral or high
TABLE I Composition of the broiler starter and finisher diets Basal diets
Starter Finisher
[Week 1 – 3] [Week 4 – 6]
Ingredients [g/kg]
Full fat soybean 175.0 18.4
Corn 492.7 437.9 Corn gluten 63.36 80.0 Wheat middlings 78.45 80.0 Soybean meal (440 g CP/kg) 102.15 200.0 Rice – 80.0 Fish meal (660 g CP/kg) 20.7 11.7
Meat and bone meal (340 g CP/kg) 30.0 20.0
Dicalcium phosphate 10.0 5.7 Limestone 9.79 7.22 Vitamin premix1 2.5 2.5 Mineral premix2 1.0 1.0 Anticoccidial3 1.0 1.0 Methionine 2.12 0.9 NaCl 3.08 2.31 Vegetable fat 8.05 51.45 Analysis [g/kg] Dry matter 891.7 887.7 Ash 39.0 33.2 Crude protein 230.0 215.0 Ether extract 71.7 84.6 Crude fibre 36.2 32.5 Lysine 11.0 9.7 Methionine 6.2 5.0 Methionine + Cystine 10.0 8.6 Calcium 11.0 7.5 Available phosphorus 5.0 3.5 Carnitine [mg/kg] 7.14 14.6 ME [MJ/kg] 12.8 13.2 1
Provided per kg diet: 12.000.000 IU vit. A, 1.500.000 IU vit. D3; 50 g vit. E, 5 g vit. K3, 3 g vit. B1, 6 g vit. B2, 25 g niacin,
12 g Ca-D-pantothenate, 5 g vit. B6, 30 mg vit. B12, 1 g folic acid, 50 mg D-biotin, 400 g choline chloride. 2
Provided per kg diet: 80 g Mn, 60 g Fe, 60 g Zn, 5 g Cu, 0.2 g Co, 1 g I, 0.15 g Se.
3
Provided per kg diet: 72 mg Salinomycin (starter diet), 110 mg Methylchlorypidnol.
3 CARNITINE IN BROILER FEEDING
temperature regimes as main effects. According to the experimental design, four dietary treatment groups were obtained under each temperature regime. These groups were control (no supplemental carnitine or ascorbic acid), supplemental L-carnitine, supplemental ascorbic acid and supplemental L-carnitine + ascorbic acid. The birds under thermoneutral condition received 20 – 228C for 24 h, while the birds under high temperature regime were exposed to 34 – 368C for 8 h and 20 – 228C for 16 h in a day.
Each group was fed ad-libitum with diet and its own water for a period of 42 days. The basal diet was analysed for dry matter (DM), crude protein (CP; N 6 6.25), crude fibre (CF), diethyl ether-extractable fat and crude ash (CA) using standard methods. Concentrations of L-carnitine in the starter and finisher basal diets were determined according to Brˇichna´cˇova´ (1999). All birds were housed in individual cages in a complete randomised design. During the experiment, relative humidity (60 – 70%) was controlled and light was provided 24 h.
2.2. Growth performance, carcass analysis and plasma L-carnitine concentration
During the experiment, growth performance was evaluated by recording body weight, body weight gain, water intake, feed intake and feed conversion ratio.
Individual body weights of the chicks were recorded at the beginning of the experiment (1-day-old) and on a weekly basis thereafter. Feed and water intakes were recorded weekly. Feed conversion ratio was calculated weekly as the amount of feed consumed per unit of body weight gain. Birds were slaughtered for carcass analyses at 42 days of age. The carcasses were immediately plucked, eviscerated, weighed and then chilled overnight in a fridge in order to facilitate the removal of abdominal fat before cold carcass weight.
At the end of the experiment five birds from each experimental group, with body weights around the average of the representative group, were selected and blood samples were collected in heparinized tubes. After centrifugation of blood samples, plasma samples were obtained and analysed for free L-carnitine according to Enzymatic UV test (Roche, 1999).
Edible parts of carcasses selected for nutrients analyses were minced and analysed for dry matter, crude ash, crude protein (N 6 6.25), crude fat.
2.3. Statistical analysis
The data were analysed statistically using the GLM (General Linear Model) procedure of SAS (1996) and treatment means were separated using Duncan’s New Multiple Range Test.
3. RESULTS
The results with regard to growth performance are summarized in Tables II (body weight gain), III (feed intake), IV (feed conversion ratio), V (water intake) and VI (carcass weight, carcass yield, abdominal fat weight, plasma L-carnitine concentration). The results showed that supplemental L-carnitine, ascorbic acid had no significant effects on body weight gain during the entire period (1 – 6 weeks). However,
TABLE II Effect of ambient temperature and dietary L-carnitine and ascorbic acid on body weight gain of broiler chicks (mean + SD)
Variables Main effects
Ascorbic acid [mg/l]
Parameters Temperature L-carnitine [mg/l] 0 500 Temperature L-carnitine Ascorbic acid BWG Weeks 1 – 3 [g/bird] Normal 0 588 + 91 605 + 28
50 601 + 66 568 + 68 NS NS NS
High 0 545 + 88 584 + 75
50 586 + 53 565 + 77 BWG Weeks 1 – 6 [g/bird] Normal 0 2286 + 230a 2315 + 250a
50 2200 + 251ab 2141 + 193abc * NS NS High 0 1926 + 253d 1981 + 214dc
50 2015 + 141bcd 2068 + 209bcd
Means with different supercript letters for each parameter represents a significant interaction (P 5 0.05). * Represent significant main effects (P 5 0.05).
NS : Not significant (P 4 0.05).
TABLE III Effect of ambient temperature and dietary L-carnitine and ascorbic acid on feed intake of broiler chicks (mean + SD)
Variables Main effects
Ascorbic acid [mg/l]
Parameters Temperature L-carnitine [mg/l] 0 500 Temperature L-carnitine Ascorbic acid Feed intake Weeks 1 – 3 [g/bird] Normal 0 915 + 102ab 958 + 162a
50 905 + 123ab 913 + 89ab * NS *
High 0 776 + 130c 899 + 118ab
50 840 + 76bc 890 + 114ab Feed intake Weeks 1 – 6 [g/bird] Normal 0 3769 + 303ab 3931 + 450a
50 3589 + 450ab 3656 + 280ab * NS * High 0 3017 + 387d 3443 + 461bc
50 3262 + 246cd 3570 + 379bc
Means with different supercript letters for each parameter represents a significant interaction (P 5 0.05). *Represent significant main effects (P 5 0.05).
NS: Not significant (P 4 0.05).
8
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5 CAR NITINE IN BROILER FEED INGT A BLE IV E ff ec t o f a mbie nt te mp erat ure a nd d ietary L -carnitine an d a scorb ic a cid o n fee d conve rsion ratio o f b roiler chick s (m ean + SD ) V a riabl e s M a in effects A scorbic acid [mg/l] Paramete rs Temperatur e L -carni ti ne [mg/l] 0 500 Temperature L -c a rnitine As c o rb ic acid FCR W eeks 1 – 3 Norma l 0 1 .56 + 0.2 ab 1. 5 8 + 0.1 a 5 0 1.51 + 0.1 b 1. 6 1 + 0.1 ab *N S* Hig h 0 1 .42 + 0.1 c 1. 5 4 + 0.1 ab 5 0 1.43 + 0.0 c 1.58 + 0.1 ab FCR W eeks 1 – 6 Norma l 0 1 .65 + 0.1 bc 1. 7 0 + 0.0 ab 5 0 1.63 + 0.1 c 1. 7 1 + 0.1 a NS NS * Hig h 0 1 .57 + 0.1 d 1. 7 4 + 0.1 a 5 0 1.62 + 0.1 c 1. 7 3 + 0.1 a Me an s w it h d iffer en t su p er cr ip t let te rs fo r ea ch p a ra m e te r re pr es en ts a si g n ifi ca n t in te ra ct io n (P 5 0. 05 ). *R ep re se nt si gn ifi ca nt ma in eff ec ts (P 5 0. 05 ). NS :Not si gn ifi ca nt (P 4 0. 05) . T A B L E V E ff ec t o f a mb ie nt te mp er at ur e a n d di et ary L -c ar nit in e and a sco rb ic a cid o n w a ter int a ke of b ro ile r chic k s (me an + SD ) V a riables Main effe c ts A sc o rb ic ac id [ m g /l] Pa ra meters Temperature L -car n iti n e [m g /l] 0 500 Temperature L -carnitine Ascorbi c acid Wa te r intake 1 – 3 weeks [g/bir d ] N or mal 0 1 563 + 26 0 1 583 + 22 0 50 1 574 + 32 3 1 484 + 24 2 N S N S N S High 0 1 527 + 38 5 1 697 + 34 9 50 1 631 + 25 4 1 529 + 17 9 Wa te r intake 1 – 6 weeks [g/bir d ] N or mal 0 6 541 + 84 8 6 868 + 12 43 50 6 599 + 14 03 6 582 + 14 55 NS NS * High 0 6 559 + 14 57 7 400 + 20 72 50 6 948 + 13 98 6 733 + 96 2 *R ep re sen t si g n ifi ca n t m a in effe ct s (P 5 0. 05 ). NS :N o t si gn ifi ca nt (P 4 0. 05 ).
TABLE VI Effect of ambient temperature and dietary L-carnitine and ascorbic acid on carcass parameters and level of plasma L-carnitine of broiler chicks (mean + SD)
Variables Main effects
Ascorbic acid [mg/l]
Parameters Temperature L-carnitine [mg/l] 0 500 Temperature L-carnitine Ascorbic acid Carcass weight [g/bird] Normal 0 1704 + 164a 1711 + 184a
50 1628 + 196ab 1588 + 140abc
High 0 1409 + 190d 1476 + 170cd * NS NS
50 1498 + 109bcd 1533 + 162bcd Carcass yield [% of BW at day 42 of age] Normal 0 73.3 + 1.8a 72.7 + 0.7ab
50 72.7 + 1.7ab 72.8 + 1.3ab
High 0 71.7 + 2.4b 73.0 + 1.9ab NS NS NS
50 72.9 + 1.0ab 72.6 + 1.9ab Abdominal fat weight [g/bird] Normal 0 32.3 + 9.6ab 34.2 + 9.8a
50 28.7 + 6.8ab 30.6 + 10.2ab
High 0 26.0 + 7.6b 29.3 + 9.4ab * NS NS
50 29.6 + 7.9ab 30.5 + 8.0ab
Relative weight of abdominal fat Normal 0 1.88 + 0.4 2.01 + 0.6 [% of carcass weight] 50 1.76 + 0.3 1.91 + 0.6
High 0 1.83 + 0.4 1.96 + 0.5 NS NS NS
50 1.96 + 0.4 1.98 + 0.4 Plasma L-carnitine [mg/l] Normal 0 17.43 + 2.5ab 14.26 + 1.3ab
50 16.20 + 3.0ab 12.45 + 2.7ab
High 0 8.74 + 1.3b 15.38 + 2.6ab NS NS NS
50 13.15 + 1.5ab 20.17 + 3.3a
Means with different supercript letters for each parameter represents a significant interaction (P 5 0.05). *Represent significant main effects (P 5 0.05).
NS : Not significant (P 4 0.05).
8
7 CAR NITINE IN BROILER FEED INGtemperature had a significant effect on body weight gain at the end of the experiment, although temperature had no influences during the first 3 weeks of the experiment.
Feed intake of broilers was influenced significantly by temperature and ascorbic acid supplementation during the experimental period (1 – 3 weeks and 1 – 6 weeks). Birds fed ascorbic acid and L-carnitine + ascorbic acid supplemented diets consumed a higher amount of feed compared with the unsupplemented and L-carnitine supplemented animals under stress conditions (Table III).
Feed conversion ratio was influenced significantly by temperature and ascorbic acid supplementation during the first 3 weeks of the experiment and during the experimental period, respectively. Feed conversion ratio was lower (P 5 0.05) for chicks fed the L-carnitine diet when compared to chicks fed the ascorbic acid and L-L-carnitine + ascorbic acid under normal conditions during the study (1 – 6 weeks). Throughout the experiment under high temperature, a significantly improved feed conversion ratio was noted for chicks receiving the control diet (1.57) compared to those fed supplemental L-carnitine (1.62), ascorbic acid (1.74) and L-carnitine + ascorbic acid diets (1.73). The feed conversion ratio was affected negatively by supplemental ascorbic acid during the experimental period. However, temperature affected (P 5 0.05) feed conversion rate of broilers between 1 – 3 weeks (Table IV).
As indicated in Table V, neither temperature nor supplemental dietary L-carnitine affected water intake of broilers throughout this study. However, ascorbic acid increased water intake significantly, as the groups receiving supplemental ascorbic acid consumed higher amount of water than their unsupplemented counterparts. L-carnitine intakes of broiler groups were 330, 329.1, 347.4 and 336.7 mg in normal fed supplemental carnitine, normal carnitine + ascorbic acid, heated supplemental L-carnitine and heated supplemental L-L-carnitine + ascorbic acid groups, respectively. Ascorbic acid intakes of broiler groups were 3434, 3291, 3700 and 3365.5 mg in normal fed supplemental ascorbic acid, normal L-carnitine + ascorbic acid, heated supple-mental ascorbic acid and heated supplesupple-mental L-carnitine + ascorbic acid groups, respectively.
As shown Table VI, temperature had a significant effect on carcass weight. The groups maintained under a high temperature regime exhibited lower carcass weight than their unheated counterparts. Carcass yield, relative abdominal fat
and plasma L-carnitine concentration of broilers were not affected by
temperature, supplemental L-carnitine and ascorbic acid. However, abdominal fat weight was affected by temperature, as groups receiving no supplemental L-carnitine + no supplemental ascorbic acid, no supplemental L-L-carnitine + supple-mental ascorbic acid, supplesupple-mental L-carnitine + supplesupple-mental ascorbic acid under high temperature exhibited a lower abdominal fat weight than their unheated counterparts.
Carcass dry matter, ash and fat content was modified by the various treatments. Only carcass protein content was reduced by supplemental ascorbic acid (Table VII).
4. DISCUSSION
The results of this investigation suggested that broilers receiving L-carnitine supple-mentation could be better able to cope with various stress factors during fattening. L-carnitine and L-L-carnitine + ascorbic acid combination have a positive effect on growth
TABLE VII Effect of ambient temperature and dietary L-carnitine and ascorbic acid on carcass composition of broiler chicks (mean + SD)
Variables Main effects
Ascorbic acid [mg/l] Parameters [%] Temperature L-carnitine [mg/
l]
0 500 Temperature L-carnitine Ascorbic acid Dry Matter Normal 0 35.3 + 1.9ab 36.4 + 1.3ab
50 38.2 + 2.9a 36.6 + 0.4ab High 0 34.0 + 1.5b 36.4 + 1.1a
50 34.6 + 0.4b 35.8 + 3.0ab NS NS NS
Crude Ash Normal 0 2.4 + 0.2a 2.4 + 0.3a
50 2.4 + 0.2a 2.2 + 0.2ab
High 0 2.2 + 0.3ab 1.8 + 0.4b
50 2.4 + 0.6a 2.4 + 0.1a NS NS NS
Crude Fat Normal 0 15.2 + 1.7 15.5 + 1.2 50 16.9 + 1.4 16.9 + 1.2
High 0 15.2 + 0.9 17.3 + 1.2 NS
50 15.3 + 2.0 16.8 + 3.2 NS NS
Crude Protein Normal 0 18.2 + 0.5ab 17.5 + 0.8bc 50 18.1 + 0.5ab 17.8 + 0.3abc
High 0 18.6 + 0.6a 17.1 + 0.3c
50 18.1 + 0.2ab 17.1 + 0.5c NS NS *
Means with different supercript letters for each parameter represents a significant interaction (P 5 0.05). *Represent significant main effects (P 5 0.05).
NS : Not significant (P 4 0.05).
8
9 CAR NITINE IN BROILER FEED INGof broiler chicks reared under heat. Kutlu and Forbes (1993b) reported that 200 – 250 mg/kg ascorbic acid supplementation of the diet alleviated growth and food intake of broiler chicks under heat stress.
Reports on the response of avian species, particularly broilers, to supplementary dietary L-carnitine are conflicting. Studies with layers, young pigs and fish have shown some favourable responses to added dietary L-carnitine addition (Rabie et al., 1997c; Weeden et al., 1991; Torreele et al., 1993).
Rabie and Szila´gy (1998) reported that in broilers the requirement for L-carnitine is increased by rapid growth. Borum (1991) reported that biosynthetic capacity of L-carnitine is reduced by prematurity, and is high in infancy. Supplemental dietary L-carnitine and ascorbic acid or/in combination L-carnitine + ascorbic acid may imply that the requirement of broiler chicks for L-carnitine and ascorbic acid are lower during a period of early ages. We found no significant differences in broiler weight gain within groups during the first 3 weeks of the experimental period.
The additions of L-carnitine and L-carnitine + ascorbic acid in these trials led to increased body weight gain compared to the control group reared under heat stress. Control and supplementation with ascorbic acid, by contrast, produced the opposite result compared to L-carnitine and L-carnitine + ascorbic acid reared under normal conditions. This effect may be due to the enhanced stress resistance.
Plasma of L-carnitine were low in unsupplemented animals, especially under heat stress (not significant). This result may suggest L-carnitine was not synthesized in the liver sufficiently, although L-carnitine can be synthesized in the liver from methionine and protein bound lysine. Another explanation would be a stimulated turnover of carnitine under heat stress.
The results of this study showed that L-carnitine and ascorbic acid alone or in combination, may slightly increase weight gain and carcass weight in broiler chicks at high environmental temperature. The differences are most probably due to the improved energy transformation rate produced by L-carnitine, which plays important roles in the intermediary metabolism of amino acids and fatty acids resulting from the ascorbic acid treatment, and, furthermore, ascorbic acid is involved in L-carnitine synthesis.
Although considerable species and tissue-specific differences exist in L-carnitine
concentrations, various studies have shown that the oral or parenteral
administration of L-carnitine in various species, particularly when given for therapeutic purposes, markedly increases L-carnitine concentrations in plasma (humans: Gregory S. Kelly, 1998; horses: Foster et al., 1989) and cardiac muscle (dogs: Neu, 1995). This particular finding was also observed in the animals receiving supplemental L-carnitine and ascorbic acid under high temperature in the plasma investigated in our study, and may explain the slight improvement in body weight gain with L-carnitine supplementation. However the amount of abdominal fat was not reduced as observed in other studies (Lettner et al., 1992; Leibetseder, 1995).
These inconsistent responses of animals to supplementary L-carnitine and ascorbic acid may be related mainly to inter-species differences, age, sex, plane of nutrition, feeding programme, nutrient composition of the diet, levels of L-carnitine or its precursors in the diet and/or managerial or environmental conditions.
5. CONCLUSION
The results obtained in the present study showed that L-carnitine and ascorbic acid could have growth-promoting effects in broiler chicks under heat stress. The diet should be reinforced more L-carnitine supplementation reared under high temperature. The results may also provide evidence that L-carnitine biosynthesis in birds is lowered under heat stres. Additional studies are required in order to explore the specific role of L-carnitine in the metabolism of broiler chickens maintained under high temperature.
Acknowledgements
The authors would like to acknowledge the grant support provided by C¸.U. Research Fund. L-carnitine analysis in feed was determined by Lohmann Animal Health, Cuxhaven, Germany. Special thanks are due to Dr. S. Jacobs, Lohmann Cuxhaven for his support to Prof. H. Krog for gifts of Carniking, to Dr. O¨. Yu¨celt of Ekol A. S¸. for gifts of protected ascorbic acid.
References
Barker, D.L. and Sell, J.L. (1994) Dietary carnitine did not influence performance and carcass composition of broiler chickens and young turkeys fed low- or high-fat diets. Poult. Sci., 73, 281 – 287.
Bieber, L.L. (1988) Carnitine. Ann. Rev. Biochem., 57, 261 – 283. Borum, P.R. (1983) Carnitine. Ann. Rev. Nutr., 3, 233 – 259.
Borum, P.R. (1991) Carnitine and lipid metabolism. Boletin de la Associacio´n Me´dica de Puerto-Rico, 83, 134 – 135.
Bremer, J. (1983) Carnitine-metabolism and functions. Physiol. Rev., 63, 1420 – 1480.
Brˇichna´cˇova´, J. (1999) Determination of L-carnitine in L-carnitine dir, L-carnitine usp crystalline, carnifeed and carniking by potentiometric titration. Lonza group fine chemicals and specialities. LONZA Biotec s.r.o., 2, 1 – 8.
Cartwright, A.L. (1986) Effect of carnitine and dietary energy concentration on body weight and body lipid of growing broilers. Poult. Sci., 65(Suppl.): S21.
Foster, C.V.L., Harris, R.C. and Pouret, J.M. (1989) Effect of oral L-carnitine on its concentration in the plasma of yearling throughbred horses. Vet. Rec., 125, 125 – 128.
Gaylord, T.G. and Gatlin III, D.M. (2000) Dietary lipid level but not L-carnitine affects growth performance of hybrid striped bass (Morone chrysops 6 M. saxatilis). Aquacult., 190, 237 – 246.
Gregory, S. and Kelly, N.D. (1998) L-carnitine: therapeutic applications of a conditionally-essential amino acid. Altern. Med. Rev., 3, 345 – 360.
Harpaz, S., Becker, K. and Blum, R. (1999) The effect of dietary L-carnitine supplementation on cold tolerance and growth of the ornamental cichlid fish pelvicachromis pulcher-preliminary results. J. Therm Biol., 24, 57 – 62. Henrique, M.M.F., Gomes, E.F., Gouillou-Coustans, M.F., Oliva-Teles, A. and Davies, S.J. (1998) Influence of supplementation of practical diets with vitamin C on growth and response to hypoxic stress of seabream sparus aurata. Aquaculture, 161, 415 – 426.
Janssens, G.P.J., Buyse, J., Seynaeve, M., Decuypere, E. and De Wilde, R. (1998) The reduction of heat production in exercising pigeons after L-carnitine supplementation. Poult. Sci., 77, 578 – 584.
Kutlu, H.R. (2001) Influences of wet feeding and supplementation with ascorbic acid on performance and carcass composition of broiler chicks exposed to a high ambient temperature. Arch. Anim. Nutr., 54, 127 – 139. Kutlu, H.R. and Forbes, J.M. (1993a) Alleviation of the effect of heat stress by dietary methods in broilers: a
review. World Review of Animal Production, 28, 16 – 26.
Kutlu, H.R. and Forbes, J.M. (1993b) Changes in growth and blood parameters in heat stressed broiler chicks in response to dietary ascorbic acid. Live. Prod. Sci., 36, 335 – 350.
Leibetseder, J. (1995) Untersuchungen u¨ber die Wirkungen von L-Carnitin beim Huhn. Arch. Anim. Nutr., 48, 97 – 108.
Lettner, V.F., Zollitsch, W. and Halbmayer, E. (1992) Einsatz von L-Carnitin im Hu¨hnermastfutter. Bodenkultur, 43, 161 – 167.
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11 CARNITINE IN BROILER FEEDINGNeu, H. (1995) L-carnitine-chemistry, function and clinical ımportance in canine cardiac disease (cardiomyo-pathies)- A review of the literature. Kleintierpraxis, 40, 197 – 220.
Pardue, S.L., Thaxton, J.P. and Brake, J. (1985) Influence of supplemental ascorbic acid on broiler performance following exposure to high environmental temperature. Poult. Sci., 64, 1334 – 1338.
Rabie, M.H. and Szila´gyi, M. (1998) Effects of L-carnitine supplementation of diets differing in energy levels on performance, abdominal fat content and yield and composition of edible meat of broilers. Brit. J. Nutr., 80, 391 – 400.
Rabie, M.H., Szila´gyi, M. and Gippert, T. (1997a) Effects of dietary L-carnitine supplementation and protein level on performance and degree of meatness and fatness of broilers. Acta Biol. Hung., 48, 221 – 239. Rabie, M.H., Szila´gyi, M. and Gippert, T. (1997c) Influence of supplemental dietary L-carnitine on performance
and egg quality of pullets during the early laying period. A´llattenye´szte´s e´s Takarma´nyoza´s, 46, 457 – 468. Rabie, M.H., Szila´gyı, M., Gippert, T., Votisky, E. and Gerendai, D. (1997b) Influence of dietary L-carnitine on
performance and carcas quality of broiler chickens. Acta Biol. Hung., 48, 241 – 252.
Rebouche, C.J. (1992) Carnitine function and requirements during the life cycle. Faseb J., 6, 3379 – 3386. Roche, (1999) L-Carnitine. Enzymatic UV test for the determination of L-carnitine in research samples from
seminal plasma, serum or urine. Cat. No. 1 242 008.
SAS Institute (1996) SAS User’s guide: statistics. (Cary, NC, SAS Institute).
Torreele, E., Sluiszen, A.V.D. and Verreth, J. (1993) The effect of dietary L-carnitine on the growth performance in fingerlings of the african catfish (Clarias Garipinus) in relation to dietary lipid. Brit. J. Nutr., 69, 289 – 299. Weeden, T.L., Nelssen, J.L., Hansen, J.A., Fitzner, G.E. and Goodband, R.D. (1991) The effect of L-carnitine on
starter pig performance and carcass composition. J. Anim. Sci., 69, Suppl. 105 Abstr.
Whitehead, C.C., McCormack, H.A. and McTeir, L. (1997) Effects of dietary carnitine supplementation on cell integrity in young chicks under acute heat stress. Roslin Institute, Midlothian EH25 9PS, Scotland.
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1 Sa´ndoret al., 1983 in text, not in references
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3 Gaylord and Gatlin (2000) in refs, not located in text
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