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ANIMAL PRODUCTION • Cienc. Rural 54 (3) • 2024 • https://doi.org/10.1590/0103-8478cr20210540 linkcopy

Open-access Dietary supplementation of glutamine and glutamic acid on performance, intestinal morphometry, and carcass characteristics of broiler quails

Suplementação dietética de glutamina e ácido glutâmico sobre o desempenho, morfometria intestinal e características de carcaça de codornas de corte

AuthorshipSCIMAGO INSTITUTIONS RANKINGS

    ABSTRACT:

    This study evaluated the effect of dietary supplementation with glutamine and glutamic acid (Gln+Glu) on performance, intestinal morphometry, and carcass characteristics of broiler quails. Eight hundred birds were used, distributed in an entirely randomized design with 20 birds per experimental unit, and given five treatments (0.0; 0.2; 0.4; 0.6; and 0.8% Gln+Glu supplementation) with eight replicates. At 1-21 days of age, lower (P < 0.05) feed intake at 0.6 and 0.8% Gln+Glu supplementation and lower weight gain at 0.8% Gln+Glu supplementation compared to the control treatment were observed. By regression analysis, excluding the control treatment, there was an increasing linear effect (P < 0.05) for feed intake at 22 to 42 days of age. For intestinal morphometry, Gln+Glu supplementation only favored the villus development of the ileum (P < 0.05), giving it greater height at 0.2, 0.6, and 0.8% supplementation. Carcass characteristics, cuts, and edible viscera of the birds at 42 days were not affected (P > 0.05) by Gln+Glu supplementation levels. Thus, the glutamine and glutamic acid supplementation affected the performance and intestinal morphology of 21-d-old quails, decreasing feed intake and weight gain associated with the improvement of ileum morphology; conversely, performance and carcass characteristics at 42 days were not affected by amino acid supplementation.

    Key words:  Coturnix ; glutamate; intestinal morphophysiology; cell renewal

    RESUMO:

    Objetivou-se avaliar o efeito da suplementação dietética de glutamina e ácido glutâmico (Gln+Glu) sobre o desempenho, a morfometria intestinal e as características de carcaça de codornas de corte. Foram utilizadas 800 aves, distribuídas em delineamento inteiramente casualizado, com cinco tratamentos (0,0; 0,2; 0,4; 0,6 e 0,8% de suplementação de Gln+Glu) e oito repetições com 20 aves por unidade experimental. Na fase de um a 21 dias, constatou-se menor (P < 0,05) consumo de ração aos níveis de 0,6 e 0,8% de Gln+Glu e menor ganho de peso ao nível 0,8% de Gln+Glu em comparação ao tratamento controle; e, pela análise de regressão, excluindo-se o tratamento controle, houve efeito linear crescente (P < 0,05) para consumo de ração na fase 22 a 42 dias de idade. Para morfometria intestinal, a suplementação de Gln+Glu apenas favoreceu o desenvolvimento vilos do íleo (P < 0,05), conferindo-lhe maior altura aos níveis de 0,2; 0,6 e 0,8% de suplementação. As características de carcaça, cortes e vísceras comestíveis das aves aos 42 dias não foram afetadas (P > 0,05) pelos níveis de suplementação de Gln+Glu. Assim, a suplementação de glutamina e ácido glutâmico influenciou o desempenho e a morfometria intestinal de codornas de corte aos 21 dias de idade, promovendo redução do consumo de ração e do ganho, associado ao aumento morfométrico do íleo; por outro lado, o desempenho das aves e as suas características de carcaça aos 42 dias não foram afetados pela suplementação dos aminoácidos.

    Palavras-chave:  Coturnix coturnix ; glutamato; morfofisiologia intestinal; renovação celular

    INTRODUCTION:

    The immaturity of the digestive tract in the first weeks post-hatch is a limiting factor for the development of productive poultry. This is because increases in enzyme secretion capacity and absorption area, which occur through the longitudinal growth of the small intestine and the increase in villus height, remain ongoing (CRUZ et al., 2019; CASTRO et al., 2020). Studies have been developed with the purpose of maximizing the functional capacity of the poultry intestine, using nutrients that can improve the development of the mucosa (DAI et al., 2011; SAKAMOTO et al., 2011; REZAEI et al., 2018), so that there is better utilization of the diet.

    Glutamine, glutamic acid, and threonine are nutrients that have shown important trophic effects on the intestinal mucosa of birds, acting on their development and histological maturation (CASTRO et al., 2020; SALMANZADEH et al., 2016). Among these amino acids, glutamine (Gln) and glutamic acid (Glu) have drawn attention for their functional properties on the intestinal mucosa. Glutamine and glutamic acid are important sources of energy for rapidly proliferating cells, such as enterocytes and defense cells. As trophic agents, they contribute to the development and maintenance of the mucosal structure (FASINA et al., 2010), acting directly on the improvement of poultry performance. Research with broilers and layers has shown satisfactory results regarding the effect of glutamine and glutamic acid supplementation on the performance, digestibility and intestinal microbiota of broilers (NASCIMENTO et al., 2014; BEZERRA et al., 2015; SALMANZADEH et al., 2016); however, studies are needed to evaluate the effect on bird growth and utilization of dietary nutrients in quails.

    This study evaluated the effect of dietary glutamine supplementation associated with glutamic acid on the performance, intestinal morphometry, and carcass characteristics of broiler quails.

    MATERIALS AND METHODS:

    A total of 800 unsexed broiler quails were used from 1 to 42 days of age, with a mean initial weight of 9.35 g ± 0.10 g. On the first day, the birds were weighed individually, separated by weight and distributed uniformly by weight range in 40 experimental units.

    The experimental design was entirely randomized using 20 birds per experimental unit, with five levels (0.0; 0.2; 0.4; 0.6; and 0.8%) of glutamine supplementation associated with glutamic acid,with eight replicates.

    The experimental diets were isonutritive, formulated based on a corn and soybean meal and meeting the nutritional requirements of broiler quails (SILVA & COSTA, 2009) (Table 1). Dietary supplementation of glutamine associated with glutamic acid was performed until 21 days of age of the birds, and from 22 to 42 days of age all birds received the same basal diet. The birds received water and food during the entire rearing period. Weight gain, feed consumption, and feed conversion were evaluated for birds from 1 to 21, 22 to 42, and 1 to 42 days of age. Mortality was monitored daily to calculate rearing viability and to correct feed consumption and feed conversion.

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    Table 1
    Percentage and nutritional composition of experimental diets from 1 to 21 days of age.

    At 21 days of age, five birds per treatment, with an average weight of the experimental unit (± 5%), were removed for evaluation of intestinal morphometry. After stunning by electroscalding followed by bleeding, the median region of the duodenum, jejunum, and ileum was collected to measure villus height, crypt depth, and villus:crypt ratio. The samples were kept in 10% buffered formaldehyde solution for 24 hours, then dehydrated in an increasing series of alcohols, treated with xylene; and subsequently, embedded in paraffin. To mount the slides, cuts 5 µm thick were made with the aid of a rotating microtome. Subsequently, the sections were deparaffinized and hydrated using xylene, a series of alcohols and water, and then stained using the hematoxylin-eosin (HE) method.

    Image capture of histological sections was performed using an optical microscope with a 4× magnification lens. The morphometric analyses were performed on an image analyzer (Motic Images Plus 2.0), performing 12 measurements of villus height and 12 measurements for crypt depth per histological section, totaling 60 readings per variable, per treatment, for each intestinal segment.

    At 42 days of age, 2 birds per experimental unit, varying by up to 5% from the average weight of the experimental unit, were selected and slaughtered for determination of carcass yield. After manual plucking, the carcasses were eviscerated, washed, drained, and weighed. The weight of the cleaned carcass as a percentage of the live weight of the bird after fasting was considered as the carcass yield. Subsequently, the carcass was dressed and the cuts and viscera were weighed. The yield of legs, breast, wings, back, and edible viscera were considered in relation to the weight of the eviscerated and cleaned carcass.

    The results were subjected to an analysis of variance, then compared using Dunnett’s post hoc test and regression, with the aid of the statistical program SAS - Statistical Analysis System 9.0 at 5% probability.

    RESULTS:

    The levels of glutamine associated with glutamic acid influenced the performance of the quails, as presented in table 2. Dunnett’s test revealed that from 1 to 21 days of age, there was a significant effect (P < 0.05) of Gln+Glu supplementation on feed consumption, which was lower at 0.6 and 0.8% Gln+Glu; and on the weight gain of the birds, which also decreased at 0.8% Gln+Glu supplementation, compared to the control treatment. However, the feed conversion of the birds was not influenced (P > 0.05) by the tested levels. In the regression analysis, except for the zero level of Gln+Glu in the analysis of variance, the performance of the birds was not affected (P > 0.05) by the levels of Gln+Glu in the diet.

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    Table 2
    Feed intake (FI, g), weight gain (WG, g), and feed conversion (FC, g/g) of broiler quails subjected to glutamine supplementation levels associated with glutamic acid.

    From 22 to 42 days of age, the treatments showed no significant effect on the performance variables (P > 0.05); however, by the regression analysis, excluding the control treatment from the analysis of variance, only feed consumption was affected, presenting na increasing linear effect (P < 0.05), with an average of 527.82 g. In the total rearing period from 1 to 42 days of age, the performance variables were not influenced by the treatments (P > 0.05) either by Dunnett’s test or by regression analysis.

    The effect of glutamine supplementation levels associated with glutamic acid on the intestinal morphometry of broiler quails at 21 days of age is presented in table 3. For morphometry of the duodenum, by Dunnett’s test, the only significant effect (P < 0.05) of the Gln+Glu supplementation levels was on the crypt depth, which was higher in the 0.6% Gln+Glu treatment, compared to the control treatment; however, the regression analysis excluding the treatment without glutamine and glutamic acid supplementation from the analysis of variance, showed no effect (P > 0.05) of Gln+Glu levels on the morphometry of this intestinal segment.

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    Table 3
    Effect of dietary glutamine supplementation associated with glutamic acid on intestinal morphometry of broiler quails at 21 days of age.

    Birds’ jejunum morphometry was affected (P < 0.05) by Gln+Glu supplementation levels for villus height and crypt depth. Villus height was lower at 0.4, 0.6, and 0.8% Gln+Glu levels; and crypt depth showed a significant reduction for all Gln+Glu supplementation treatments when compared to the control treatment. The analysis of variance by regression test, excluding the control treatment, showed a quadratic effect (P < 0.05) for villus height and crypt depth of the jejunum, estimating, respectively, minimum points at 0.59 and 0.58% of Gln+Glu supplementation, with respective measurements of 647.99 and 0.55 µm.

    The morphometry of the ileum showed a significant effect (P < 0.05) only for villus height, both by Dunnett’s test and regression analysis. Dunnett’s test showed that the levels of 0.2, 0.6, and 0.8% of Gln+Glu were higher than the control treatment, while the regression analysis, excluding the control treatment, showed a quadratic effect, with lower villus height at the 0.51% Gln+Glu supplementation level, estimating a height of 614 µm.

    Dietary supplementation of glutamine and glutamic acid did not influence (P > 0.05) the carcass characteristics, cuts, and edible viscera of broiler quails at 42 days of age (Table 4).

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    Table 4
    Absolute (g) and relative (%) weights of carcass, cuts and edible viscera of European quails at 42 days of age subjected to supplementation levels of glutamine associated with glutamic acid in the diet.

    DISCUSSION:

    The performance results of the present study indicate that Gln+Glu supplementation in quails from 0.6% in the first three weeks of life triggers satiety mechanisms, reflected in the lower weight gain at the 0.8% dietary supplementation level. This response in performance can be explained by the aminostatic theory, in which the increase in the availability of glutamine and glutamic acid in the organism causes aminoacid imbalance in relation to the real needs of the animals, resulting in a reduction of the feed consumption by the excitation of hypothalamic control areas (GLEAVES, 1989; GONZALES, 2002). Even so, the fact that the diet was not isoaminoacidic may have contributed to the results.

    On the other hand, SALMANZADEH et al. (2013) reported a significant increase in weight gain in Japanese quails supplemented with 30 and 40 mg/kg of glutamine. Similarly, SALLAM et al. (2019) reported improved weight gain and feed conversion in 42-d-old Japanese quails that had been supplemented in ovo with glutamine. Nevertheless, studies with poultry from other species have demonstrated well-marked limits of glutamine supplementation. For example, SOLTAN et al. (2009), obtained higher feed intake and weight gain of birds supplemented with 1% glutamine; however, when increasing the level to 1.5 and 2.0%, the authors found that feed intake and weight gain worsened. They concluded that high levels of glutamine can result in lower feed intake, lower weight gain, and even cause toxicity in animals. Similarly, BARTELL et al. (2007) reported an improvement in the weight gain of broiler chicks supplemented with 1% glutamine in the diet during the first three weeks of life, but the weight of the birds decreased when the level of supplementation was increased to 4%.

    Thus, the performance results seen in the present study showed possible particularities of broilers quails in response to glutamine and glutamic acid supplementation, differing from what had been described in most studies focusing on other poultry (FASINA et al., 2010; DAI et al., 2011; SAKAMOTO et al., 2011; NASCIMENTO et al., 2014; FIGUEIREDO et al., 2015). Authors such as SAKAMOTO et al. (2006) and FIGUEIREDO et al. (2015) found no significant difference in the performance of chickens that received glutamine supplementation at 1% and 0.5 to 1.5%, respectively, in the feed. Also, no improvement in the productive performance of broilers subjected to different densities and fed with 0.5% glutamine and glutamic acid in the diet was reported (SHAKERI et al., 2014).

    The morphometric results of the intestine justify the performance of the birds in their first three weeks of life; the jejunum, the main site of absorption of most of the nutrients, showed a reduction in villus height by supplementation at levels greater than 0.2%, and this probably impaired the utilization of nutrients. On the other hand, the greater development of the ileum in response to supplementation levels can be explained by the lower amount of Gln+Glu that reached this segment when compared to the jejunum; while the levels above 0.2% were high for the development of the jejunum, the rest of the supplemented amino acids that reached the ileum were quantitatively sufficient to favor the development of the mucosa of this segment.

    The relationship between glutamine and increased intestinal villus length in poultry has been described by other authors (BARTELL et al., 2007; SOLTAN et al., 2009; SALMANZADEH et al., 2016). In Japanese quails, glutamine supplementation resulted in expressive increase in villus height in the jejunum of birds at 21 and 42 days of age (SALMANZADEH et al., 2013). However, increased villus size and less intestinal mucosal wasting are not always associated with better growth responses in birds (SAKAMOTO et al., 2006; PELÍCIA et al., 2013; FIGUEIREDO et al., 2015). Although the early development of the intestinal mucosa is important for the performance of the animal, the greater the height and density of villi, the higher the energy cost of maintenance (REISINGER et al., 2011). SALLAM et al. (2019) reported no differences in the relative intestine weight of Japanese quails at 42 days of age that had been supplemented in ovo with glutamine when compared with the non-supplemented control group.

    The data obtained for the carcass and internal organs are consistent with performance, because the weight gain and feed conversion of birds did not vary between treatments from 1 to 42 days of age. Corroborating this proposition, NASCIMENTO et al. (2014) and FIGUEIREDO et al. (2015), found no variation in the carcass characteristics of broilers supplemented with glutamine.

    CONCLUSION:

    Glutamine and glutamic acid supplementation affected the performance and intestinal morphology of 21-d-old quails, decreasing feed intake and weight gain associated with the improvement of ileum morphology; on the other hand, performance and carcass characteristics at 42 days were not affected by amino acid supplementation.

    ACKNOWLEDGEMENTS

    The authors thank Ajinomoto do Brasil for the donation of the aminoacid compound for the execution of this research and was financed in part by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES), Brasil - Finance code 001.

    REFERENCES

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      CR-2021-0540.R2

    BIOETHICS AND BIOSSECURITY COMMITTEE APPROVAL

    • BIOETHICS AND BIOSSECURITY COMMITTEE APPROVAL
      All procedures in this study were approved by the Ethics Committee on Animal Use of the Universidade Federal da Paraíba (Protocol No. 118/2015).

    Edited by

    Publication Dates

    • Publication in this collection
      28 Aug 2023
    • Date of issue
      2024

    History

    • Received
      15 July 2021
    • Accepted
      24 May 2023
    • Reviewed
      26 July 2023
    Creative Common - by 4.0
    This is an open-access article distributed under the terms of the Creative Commons Attribution License
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