Glutamine, glutamic acid and phytogenic products as alternative additives in broiler feeds

Introduction

Normal microflora alterations or the presence of lesions in the intestinal epithelium caused by stressors, pathogens, or chemicals, are known to facilitate the invasion with other pathogens and noxious substances, resulting in badly reduced nutrient digestive/absorptive capacity. This is why feed additives have been used in animals to control rious agents that affect the digestion and absorption processes, in order to promote improved productive performance indexes.

Due to the restrictions on performance-enhancing antibiotics (PEA) use in animal feeds, and due to the demands of consumers in the search of wholesome, drug-free foods, intensive search is occurring for alternative, natural feed additives.

Research has shown that glutamine and el glutamic acid (Newsholme, 2003a; 2003b; Yi et al., 2005; Yoo et al., 1997) as well as essential oils and plant extracts (Christaki et al., 2004; Jamroz et al., 2005; Vasconcelos et al., 2010) have the ability of improving the immune response and the intestinal microflora thus preventing their negative repercussions on the intestinal structure and improving the absorption of nutrients and animal bottom line performance, in replacement of PEA, as alternative farming systems.

For economic reasons and aiming to reduce pollution, re-used litter is becoming a more and more popular practice, with the resulting increased health challenges on birds.

The objective of this study was to evaluate the effect of dietary supplementation with glutamine plus glutamic acid and phytogenic additives, either alone or in combination, as an alternative to PEA on the performance, carcass yield and edible part yields of broilers grown on re-used litter".

Materials and Methods

The experimental design was completely at random, with 5 treatments and 4 repetitions. Five hundred (500) one-day-old Cobb chicks were placed in a house divided in 24 pens of 2.5 m², at the rate of 25 birds each, for a stocking density of 10 birds/m². The birds were vaccinated in the hatchery against Marek's disease, infectious bursal disease, and fowl pox. At 8 and 14 days of age the birds received a boosted vaccine against infectious bursal disease. The treatments included one control diet (CD); CD + PEA; CD + glutamine + glutamic acid¹ (Gln/Glu); CD + phytogenic additives² (PAs) and CD + Gln/Glu + PAs. The feeding period included four phases i.e., pre-starter, started, grower, finisher. Nutrient requirements of birds were fulfilled in agreement with Rostagno et al. (2005). Feed and water were furnished ad libitum during the entire experimental period. Aiming to augment the challenge, the birds were grown on reused wood s litter.

In order to evaluate performance results, the following variables were recorded: body weight (The birds in each pen were weighed together both at arrival and at the end of the period); weight gain (estimated by the difference between final weight and start weight) feed intake (the difference between total feed offered and leftovers at period end); feed conversion rate (the ratio between total feed offered and weight gain in the period, corrected to the weight of birds dead in the period), variability (Percent of live birds in the period); productive efficiency index (PDI, calculated multiplying daily weight gain times livability times FCR times 100).

Once performance data was obtained, 5 birds per pen were taken, for a total of 20 birds per treatment. These birds were fasted for 8 hours and submitted to the experimental abattoir, UNESP, Botucatu, College of Veterinary Medicine and Animal Husbandry, Brazil. All slaughter, evisceration and cut up processes were done under industrial practices. In order to calculate carcass yield, the body weight at platform was taken, immediately prior to killing, and the weight of the eviscerated, cold, headless, neck less, feetless carcass was recorded. Breast yields and thigh+legg yield were calculated with relation to the eviscerated carcass weight. Results were tabulated then analyzed using the GLM procedure, SPSS 13.0 Windows software (2004) and the means were compared using Tukey´s test at the 5% probability level.

¹1% AminoGut ®, from 1 to 21 days and 0.5% from 22 to 42 days.

²Imunostart^® (turmeric extract, citric extracts, and grape seed extracts ) at the inclusion level of 700 g/ton from 1 to 10 days of age; 500 g/ton from 11 to 21 days of age) + Enterocox^® (eucalyptus oil, China cinnamon essential oil, Chilean pemus leafs, trigonella seeds) at the inclusion level of 300 g/ton from 1 to 10 days of age, 1,000 g/ton from 11 to 35 days of age, and 500 g/ton from 36 to 42 days of age).

Results and Discussion

Result means of performance, carcass yield and part yields, are shown in Table 1.

No influence of the treatments (P<0.05) was seen on performance variables at 42 days of age. These results disagree from others published elsewhere, which report improved performance results in birds fed glutamine-supplemented diets (Nogueira et al., 2010 and Souza et al., 2010) and glutamine + glutamic acid (Lora et al., 2006), as compared to birds fed a non-supplemented feed. Our results also disagree with those obtained by Christaki et al. (2004) who, using coccidia-challenged chickens, found an improved performance in the phytogenic additive-supplemented diet as compared with the negative controls, but a lower performance when compared with the anticoccidial-fed birds. This lack of influence of treatments on performance can be related with the mild challenge resulting from the reused litter.

Higher carcass yield (P<0.05) was obtained in the Gln+Glu and Gln/Glu + PAs treatments as compared to the CD treatment, with no differences from the PEA and PAs treatments, that, also, did not differ among themselves. The highest breast yield (P<0.05) was obtained with the Gln/Glu treatment as compared to the CD and PEA treatments, which did not differ among themselves or with any other treatments.

In addition of being involved in the structure of proteins and peptides, glutamine donates one carbon chain and one amino group that enter the processes leading to the synthesis of other amino acids, and that can be used in the synthesis of purines and pyrimidines, basic constituents of nucleotides that, in turn, are components of the DNA and RNA molecules (Nelwsholme et al., 2003a; 2003b), essential for protein synthesis. Some studies have reported a positive correlation between free glutamine concentrations and protein synthesis rate in the skeletal muscle. In other words, the higher the circulating glutamine concentration the higher the protein synthesis rate. In addition of promoting protein synthesis in the muscle, glutamine exerts an inhibitory effect on muscle protein catabolism (Maclennan et al., 1988). Therefore, glutamine can work as a metabolic regulator, increasing protein synthesis and reducing protein catabolism, when supplemented in the feed (Lobley et al., 2001). This could explain the better results in carcass yield and breast yield obtained in this study.

Other workers that added PAs (Sheuermann et al., 2009) and Gln/Glu (Sakamoto et al., 2009) to broiler diets, observed no effect whatsoever on performance variables.

Table 1. Per-treatment means of end weight (EW), weight gain (WG), feed intake (FI), feed conversion rate (FCR), livability (LIV), productive efficiency index (PEI) carcass yield and part yields in broilers, at 42 days.

Variables	Treatments
CD	PEA	Gln+Glu	PAs	Gln+Glu+PAs	CV (%)
Performance
EW (g)	2,932.44	2,920.13	2,961.24	2,951.23	2,944.02	3.37
WG (g)	2,887.64	2,875.58	2,916.54	2,906.53	2,898.77	3.41
FI (g)	4,920.67	4,835.65	4,937.24	4,877.28	4,856.67	3.31
FCR (g/g)	1.710	1.692	1.695	1.693	1.705	1.86
LIV (%)	98.00	95.00	97.00	95.00	93.00	3.74
PEI	393.80	384.38	397.62	388.75	376.37	4.49
Yield
Carcass (%)¹	73.35^b	74.44^ab	74.66^a	74.10^ab	74.73^a	2.11
Breast (%)²	39.01^b	38.95^b	40.33^a	39.34^ab	39.54^ab	3.90
Leg/Thigh(%)²	29.00	29.01	28.38	28.94	28.53	3.76

^{1Percent of live weight, 2Percent of eviscerated carcass.
Means followed by different in the same line, within a variable are statistically different, as per Tukey´s test (P<0.05).}

Conclusions

Glutamine and glutamic acid, with or with no association to phytogenic additives, result in improved carcass yield/breast yield in broilers grown under this alternative production system.

Acknowledgements

Gratitude is expressed to FAPESP, "São Paulo State Research Protection Foundation" for the scholarship granted.

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Glutamine, glutamic acid and phytogenic products as alternative additives in broiler feeds

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