Phytogenic Additives and Glutamine Plus Glutamic Acid in Broiler Diets

The objective of this study was to evaluate the effect of the dietary supplementation of phytogenic additives (PAs) and glutamine plus glutamic acid (Gln/Glu), associated or not, in replacement of antibiotic growth promoters and anticoccidials (AGP/AC) on the performance and carcass yield of broilers. Five hundred male Cobb broilers were housed in an experimental house and randomly distributed into five treatments, with four replicates of 25 birds each. Treatments consisted of a control diet (CD); CD+AGP/AC; CD+Gln/Glu; CD+PAs; CD+Gln/ Glu+PAs. Diets were formulated only with plant feedstuffs, i.e., they did not contain any animal byproducts. Performance data were collected for the accumulated periods of 1-7, 1-21, and 1-42 days of age. Carcass yield and parts yield were determined at 42 days of age. Treatments did not influence performance during none of the evaluated periods. The greatest carcass yield (p<0.05) was obtained in birds in the treatments CD+Gln/Glu and CD+Gln/Glu+PAs relative to CD, but not different from birds in the AGP+AC and PAs treatments, which were not different from the CD treatment. Birds fed the CD+Gln/Glu diet presented greater breast yield (p<0.05) compared with those in the CD and AGP/AC treatments, but there was no difference in comparison with the other treatments. Under the conditions of the present experiment, the dietary supplementation with phytogenic additives and with glutamine plus glutamic acid does not affect the performance, but improves carcass yield and breast yield of broilers.


INTRODUCTION
The public is increasingly concerned with animal welfare and food safety and quality.Also, there is a growing public pressure at domestic and international level against the addition of low doses of antibiotics and chemotherapeutic drugs in animal feeds, with a consequent increasing demand for the so-called alternative animal products, particularly for alternative poultry products.Alternative chicken products are those derived from industrial broilers that were not fed antibiotic growth promoters, anticoccidials, or animal feedstuffs and that were reared at lower stocking density, i.e., at a maximum of 12 birds/m 2 (Demattê Filho & Mendes, 2001).Therefore, there is a need to search for alternative natural additives to replace antibiotics and chemotherapic drugs in broiler diets with beneficial effects on broiler intestinal flora, thereby protecting the birds against pathogens, controlling or preventing diseases, and improving the efficiency of nutrient utilization.
Several researchers (Bartel & Batal, 2007;Murakami et al., 2007;Lora et al., 2006;Mcreynolds et al., 2009) observed the beneficial effects of glutamine and glutamic acid, as well as phytogenic additives (essential oils and plant extracts) on broiler immune response and intestinal microflora and structure, and consequently, on broiler performance, particularly in the presence of health challenges.
Glutamine (Gln) and glutamic acid (Glu) are important energy substrates for high turnover cells, such as those of the immune system and of the intestinal mucosa (Windmueller & Spaeth, 1974;Newsholme et al., 1985;Newsholme, 2001;Piva et al., 2001;Newsholme et al., 2003a and b), in addition of being part of proteins and peptides.Glutamine is also used for the synthesis of other amino acids and nucleotides (Wu, 1998).
Bartel & Batal (2007) observed higher antibody levels in broilers fed a Gln-supplemented diet compared to those not fed Gln.When supplementing 1% Gln to broiler diets, Maiorka et al. (2000), Sakamoto et al. (2005), andMurakami et al. (2007) observed beneficial effects on the development of the intestinal mucosa in one-week-old broilers, with better nutrient digestion and absorption capacities, which may improve their performance.Lora et al. (2006) studied the effect of the inclusion of different levels of a product containing a mixture of glutamine and glutamic acid (10% each) on the performance of 1-to 42-d-old broilers reared on reused litter.Broilers fed the mixture at 0.5, 1.0, and 1.5% presented higher weight gain relative to the control birds during the entire experimental period.The best production efficiency index was obtained with the 1.0% inclusion level.
Considering the reported beneficial effects of these natural additives on the intestinal structure, nutrient digestibility, and immune system of broilers, it may be possible to use them to replace antibiotic growth promoters and chemotherapeutic drugs.
The objective of this study was to evaluate the effect of the dietary supplementation with phytogenic additives and glutamine plus glutamic acid, associated or not, as an alternative to the inclusion of antibiotic growth promoter and anticoccidials on the performance and carcass yield and parts yield of broilers.

MATERIALS AND METHODS
The study was carried out at the facilities of the Poultry Nutrition Laboratory, School of Veterinary Medicine and Animal Science, Universidade Estadual Paulista (UNESP), Botucatu campus.The trial was approved by the Committee of Ethics of Animal Experimentation (protocol n. 07/2009, CEEA).
Five hundred one-d-old male Cobb broilers were housed on a twice-reused litter at a density of 10 birds/m2 , as recommended for alternative broiler production (Demattê Filho & Mendes, 2001).Chicks were vaccinated in the hatchery against Marek's disease, infectious bursal disease (IBD), and fowl pox.Birds received booster vaccine against IBD at eight and 14 days of age.
Glutamine and glutamic acid were added to the diets at the expense of corn starch as they have similar energy values, while the other additives were added at the expense of inter material (kaolin), according to the recommendations of the manufacturer.
The rearing period was divided in four phases: pre-starter, starter, grower, and finisher.Feeds were formulated according to the nutritional requirement tables of Rostagno et al. (2005), as shown in Table 1.
Performance data were collected and analyzed for the accumulated periods of 1-7, 1-21, and 1-42 days of age.The following parameters were calculated: weight gain (difference between body weight at the end of each period and body weight at housing; feed intake (difference between total feed offer and feed residues at the end of each period); feed conversion ratio (ratio between total feed offer and weight gain in the period corrected for weight of birds that died during the period), livability (percentage of live birds in each period), and production factor (average daily weight gain multiplied by livability and feed conversion ratio, and dividing the result by 100).
On day 42, 20 birds per treatment were randomly selected, submitted to fasting for eight hours, electrically stunned, and bled.Carcass yield was then calculated as the difference between live weight and the weight of the eviscerated carcass with no head, neck, or feet.Breast and leg (thighs and drumstick) yields were calculated relative to empty carcass weight.
Data were analyzed using the GLM procedure of the SPSS® version 13.0 (2004) statistical package, and means were compared by the test of Tukey at 5% probability level.

RESULTS
Variance homogeneity was confirmed by the test of Levene.All data presented normal distribution according to the KS test.
There was no effect (p>0.05) of treatment on broiler performance in the cumulative periods of 1 to 7, 1 to 21 and 1 to 42 days of age (Table 2).
However, treatments influenced carcass yield and breast yield (Table 3).Broilers in the CD+Gln/ Glu treatment presented higher (p<0.05)breast yield when compared with those in the CD and AGP/AC treatment, which were not different from each other, but similar breast yield compared with the remaining treatments.

DISCUSSION
The performance results obtained in the present study are consistent with those of other authors, who did not report any effect on performance during the periods of 1 to 7 days (Miguel et al., 2009), 1 to 21 days (Hernández et al., 2004;Toledo et al., 2007;Barreto et al., 2008) and 1 to 42 days (Fukayama et al., 2005;Toledo et al., 2007;Barreto et al., 2008) when supplementing broilers diets with phytotherapic products.However, working with 1-to 42-d-old broilers challenged with Eimeria tenella, Christaki et al. (2004) observed better performance when birds were fed a diet supplemented with a phytogenic additive (mixture of essential oils) compared than those fed a negativecontrol diet, but worse performance compared with broilers fed a diet containing an anticoccidial agent.On the other hand, Miguel et al. (2009) obtained better performance results in broilers between one and 42 days of age challenged with E. tenella, E. acervulina and E. maxima and fed the same PA as that utilized in the present study, when compared both with birds fed a negative-control diet and those fed antibiotic growth promoters (bacitracin and salinomycin).Fascina et al. (2012) also found better performance in nonchallenged broilers also fed the same PAs relative to the negative-control birds during the periods of 1-21 and 1-42 days of age.Alves et al. (2008) reported that the supplementation of broiler diets only with glutamine or glutamine associated with glutamic acid improved live performance, and recommended supplementation levels of 1.5% L-Gln and 3.0% Gln/Glu.Sakamoto et al. (2010) also obtained better performance when broilers were fed a diet supplemented with 3% Gln/Glu.In the pres-Table 2 -Average weight gain (WG), feed intake (FI), feed conversion ratio (FCR), livability (L), and production factor (PF) of broilers during the periods of 1-7, 1-21, and 1-42 days of age as a function of treatment.

Table 1 -
Composition of the control diets according to rearing phase.

Table 3 -
Average carcass yield and parts yield of 42-d-old broilers as a function of treatment.