Effect of L-carnitine supplementation on fattening and carcass parameters of broiler chickens

© Slovak University of Agriculture in Nitra Faculty of Agrobiology and Food Resources, 2015 http://www.fapz.uniag.sk/ DOI: 10.15414/afz.2015.18.01.15–19


Introduction
L-carnitine is synthesized in vivo from lysine and methionine, and it is formed with contributions from vitamins B 3 , B 6 , B 12 , C and folic acid, as well as iron (Golzar Adabi et al., 2011;Michalczuk et al., 2012).It has been reported that L-carnitine has two major functions.The best known is to facilitate the transport of long-chain fatty acids across the inner mitochondrial membrane.L-carnitine also facilitates the removal of short and medium-chain fatty acids from the mitochondria that accumulate as a result of normal and abnormal metabolism (Matalliotakis et al., 2000;Buyse et al., 2001;Xu et al., 2003).
Consequently, L-carnitine supplementation in diets reduces the amount of long-chain fatty acids availability for esterification to triacylglycerols and storage in the adipose tissue (Barker and Sell, 1994;Xu et al., 2003).
In addition, L-carnitine has secondary functions, including the containment, buffering and removal of potentially toxic acyl groups from cells, equilibrating the ratio of free CoA and acetyl-CoA between the mitochondria and cytoplasm, participating in biological processes such as regulation of gluconeogenesis, stimulating fatty acid and the metabolism of ketones, branched-chain amino acids, triglycerides and cholesterol (Novotny, 1998;Corduk et al., 2007).
The objective of the study was to investigate the effect of preparation on the base L-carnitineon performance of broiler chickens and results of slaughter analysis.

Material and methods
The experiment was realised in extensive conditions in breeding pens with deep litter with housing density 30 kg m -2 .A total of 100 broiler chickens Ross 308 were randomly divided into two groups (control and experimental -preparation with 30 % of L-carnitine).Broiler chickens in the control (C) and experimental groups (E) received a feed of the same nutritional value and chickens from experimental group were supplemented by preparation on the base L-carnitine (30.00 %), arginin chloride (19.33 %), taurine (13.33 %), magnesium gluconate (6.67 %), N-acetylocysteine (6.67 %), biotine (0.00667 %), sorbitol (0.30 %), aromatic additives (5.28 %) and vehiculum (wheat feed flour ad 1000 g).Broiler chickens were fed commercial feed mixtures: starter (days 1 to 21), grower (days 22 to 35) and finisher (days 36 to 42).The nutritive values of the feed mixtures are presented in Table 1.
During the experiment broiler chickens were weighted for individual body weight at 1, 7, 14, 21, 28, 35 and 42 days of age, feed consumption and mortality were recorded at the end of fattening period.In 42 day of fattening, 5 male and 5 females with body weight similar to the mean were chosen from each group for slaughter weighed and subjected to a 12-hours feed withdrawal.After slaughter, carcasses were chilled, weighed and subjected to simplified dissection.Abdominal fat, edible giblets and breast and leg muscles were collected and weighed.The results obtained were used to calculate dressing percentage and the percentage of carcass components.We used SAS software version 9. 3.1 (2003) to conduct statistical analyses, t-test was used to calculate basic statistic characteristics and to determine significant differences between experimental and the control groups.The choice of tests was made automatically according to the distribution of the data.Data presented were given as mean and standard deviation (SD).Differences between groups were compared for statistical significance at the level P <0.05.

Results and discussion
Table 2 showed the average body weights of broiler chickens at 1, 7, 14, 21, 28, 35 and 42 days of fattening.The experimental group chickens with supplementation of L-carnitine achieved higher body weights in comparison with the control group.Significant differences (P <0.05) were noted at 28, 35 and 42 days of fattening.At the end of fattening period, supplementation of preparation on the base L-carnitine statistically increased (P <0.05) body weight in males (Table 3).The preparation also had an effect on final body weight of females, but the differences were not significant (P <0.05).Nouboukpo et al. (2009), who investigated the effect of L-carnitine supplementation in drinking water on the growth ability of broiler chickens, observed at 7 days of rearing that chickens from the control group had significantly lower body weight compared to the experimental groups receiving 30 and 60 mg of L-carnitine in 1 l of drinking water.Rabie and Szilagyi (1998) and Buyse et al. (2001) observed a positive effect of L-carnitine on the body weight of chickens on the end of fattening period but the differences were not significant (P <0.05).Other authors who studied the effect of L-carnitine on broiler performance found that it had no effect on body weight (Leibetseder 1995;Lien and Horng, 2001;Xu et al. 2003;Cevik and Ceylan 2005).Totally feed consumption per kg live body weight was different between groups (1.74 vs. 1.79 kg) in benefit of experimental group with 1 ml preparation on the base L-carnitine per 1.2 l of drinking water.Similar results were observed by other authors (Rabie and Szilagyi, 1998;Geng et al., 2004;Czeczot and Ścibor, 2005;Geng et al., 2007).Our results are not supported by the studies of Buyse et al. (2001) and Rezaei et al. (2007), according to these authors L-carnitine supplemented to chickens had no effect on feed conversion.
The mortality rate in the both groups was identical (4.00 %).De Simone et al. (1982) and Daskirian and Teeter (2001) observed decrease in mortality in broilers receiving dietary L-carnitine.
Addition of L-carnitine in drinking water to the experimental group caused a non-significant (P <0.05) decrease in the percentage of breast muscle in males and females compared to the control group (Table 4).The addition of acetyl-L-carnitine caused a non-significant increase (Zhang et al., 2010) or significantly increases (Xu et al., 2003) in the proportion of breast muscle in the carcass.Daskirian and Teeter (2001) reported that dietary L-carnitine supplementation no affected the proportion of breast muscle.
Supplementation of L-carnitine to the experimental group of males statistically significant increased of leg muscle and non-significant decreased the proportion of leg muscle in females compared to the control group   (Table 4).Zhang et al. (2010) recorded statistically nonsignificant increase in the proportion of leg muscle.L-carnitine supplementation decreased carcass abdominal fat in broiler chickens of both sexes (Table 4).Xu et al. (2003) found a decrease in the abdominal fat of carcasses from males.In the group supplemented with L-carnitine, the abdominal fat content decreased significantly in relation to the control group.Similar results were recorded by Kamińska (2003) and Wang et al. (2003).These authors recorded statistically significant decrease of fat content in the experimental broiler chickens supplemented with L-carnitine.Opposite results to those in the L-carnitine study were obtained by Buyse et al. (2001), who observed the proportion of abdominal fat to increase in the experimental group of males and to decrease in females.
Carcass yield of males and females was higher in the experimental group in both sexes that received L-carnitine compared to the control group (Table 4), but the differences were not significant (P <0.05).Similar results were obtained by Daskirian and Teeter (2001) and Zhang et al. (2010) that the carcass yield of which increased as a result of L-carnitine supplementation, but the differences were not significant.Different results were recorded by Celik andOzturkcan (2003), Celik et al. (2003) and Kidd et al. (2009) who observed that supplementation of L-carnitine had no effect on carcass yield.
The supplementation of L-carnitine in broiler chickens from the experimental group had little effect on the percentage of gizzard, liver and heart in the carcass (Table 5).In males, the proportion of gizzard remained almost unchanged and the proportion of liver and heart slightly decreased in the L-carnitine-supplemented group compared to the control group.In females from the experimental group, the proportion of gizzard and heart decreased, the proportion of liver increased, but the differences were not significant (P <0.05).Arslan et al. ( 2004) showed a significant increase in liver percentage in group with L-carnitine supplementation.Buyse et al. ( 2001) observed average liver and heart weight to not significant increase in both males and females.Decreased weight of gizzard was found by Rabie and Szilagyi (1998), however, differences between control and experimental group (50 mg of L-carnitine per 1 kg of feed) were not significant.Not significant increase in average liver weight was also reported by Celik et al. (2003).In contrast, Rezaei et al. (2007) recorded decrease of liver weight in broiler males with L-carnitine addition.

Conclusions
In this experiment feed additive of preparation on the base L-carnitine with 30.00 % of L-carnitine had a positive effect on body weight and feed consumption in the end of fattening period.The addition of L-carnitine in drinking water positively affected the proportion of leg muscle in broiler chickens males.In other slaughter parameters we recorded statistically non significant differences between experimental group with supplementation of L-carnitine and control group.

Table 1
Nutritive values of feed mixtures in experiment

Table 2
Comparison of body weight of broiler chickens in control and experimental groups during fattening period in grams

Table 3
Comparison of body weight of broiler chickens in control and experimental groups in 42 day of fattening in grams

Table 4
Comparison of some carcass items of broiler chickens in control and experimental groups in slaughter analyse in % a, b -means in a row with different superscript differ significantly (P <0.05)

Table 5
Comparison of some edible giblets of broiler chickens in control and experimental groups in slaughter analyse in % a, b -means in a row with different superscript differ significantly (P <0.05)