نوع مقاله : مقاله پژوهشی
عنوان مقاله English
نویسندگان English
This study was conducted to develop predictive regression equations for the apparent metabolizable energy corrected for nitrogen (AMEn) of wheat bran samples produced in Iran. To this end, twelve wheat bran samples were collected from flour mills across various provinces of the country (Alborz, Khuzestan, Hamedan, Shiraz, Azerbaijan, Lorestan, Kerman, Zanjan, Qom). The samples were analyzed for crude protein, crude fiber, crude fat, acid detergent fiber (ADF), and neutral detergent fiber (NDF) content.The apparent metabolizable energy of the wheat bran samples was determined in broiler chickens aged 22 to 27 days, using the substitution method in the diet and the CELITE marker (used as acid-insoluble ash) for digestibility calculations. The basal diet in this study consisted of corn and soybean meal, with wheat bran substituted at 30% of the basal diet.The data obtained from this experiment were analyzed using SPSS software, applying the ENTER regression procedure to develop predictive equations for AMEn based on the chemical composition of wheat bran samples.The resulting regression equations for predicting AMEn of Iranian wheat bran samples were derived, and among them, the most suitable equation was selected based on criteria including p-values of the equations, p-values of the independent variables’ coefficients, the coefficient of determination (R²), and the standard error of prediction (SEP), the most appropriate equation proposed was: AMEn=23.421×NFE.
کلیدواژهها English
Extended Abstract
Introduction
Wheat bran is a major by-product of the flour milling industry and has garnered increasing attention as a partial substitute for corn in poultry nutrition. The global surge in corn prices, coupled with escalating demand for corn in bioethanol production and animal feed, has intensified the search for alternative feed ingredients. Wheat bran, with its rich content of insoluble fiber and betaine, not only offers a cost-effective alternative but also confers several health benefits to poultry, such as improved gut health, enhanced antioxidant status, and reduced risk of coccidiosis. Its high levels of betaine and phenolic compounds have been linked to improved mucosal integrity and antioxidant capacity, respectively, while its insoluble fiber content supports digestive enzyme secretion and beneficial gut microbiota. Despite these advantages, the metabolizable energy (ME) content of wheat bran is highly variable, influenced by wheat genotype, agronomic conditions, and processing methods. Accurate estimation of the nitrogen-corrected apparent metabolizable energy (AMEn) of wheat bran is therefore essential for precise feed formulation, optimal broiler performance, and economic efficiency in poultry production.
Materials and Methods
This study aimed to develop robust prediction equations for the AMEn of wheat bran samples produced in Iran, tailored for use in broiler chicken diets. For each experimental treatment, three replicates were considered, with each replicate consisting of three experimental units (male broiler chicks). A total of 21 wheat bran samples were collected from flour mills in diverse provinces, including Alborz, Khuzestan, Hamedan, Shiraz, Azerbaijan, Lorestan, Kerman, Zanjan, and Qom. Each sample underwent proximate analysis to determine dry matter (DM), crude protein (CP), crude fiber (CF), ether extract (EE), ash, acid detergent fiber (ADF), neutral detergent fiber (NDF), and nitrogen-free extract (NFE), following AOAC (1990) protocols.
To determine AMEn, a biological assay was conducted using 120 AA+ strain broiler cockerels aged 22 to 27 days. The experimental design included a basal diet (corn-soybean meal-based) and 11 test diets, each formulated by replacing 30% of the basal diet with a different wheat bran sample. After a three-day adaptation period, 2% Celite® (acid-insoluble ash) was added as an indigestible marker to all diets. Each diet was fed to three replicates of three birds each. Excreta were collected over three days, dried, ground, and analyzed for gross energy and nitrogen content. The AMEn of each wheat bran sample was calculated using the substitution method and the following equations:
where GE is gross energy, N is nitrogen, and Marker refers to the concentration of acid-insoluble ash. Statistical analyses, including regression modeling, were performed using SPSS (ENTER procedure) to derive prediction equations for AMEn based on the chemical composition of the wheat bran samples.
Results and Discussion
The proximate analysis revealed considerable variation among the wheat bran samples: CP ranged from 12/61% to 14/57%, CF from 6/5% to 10/1%, EE from 2/9% to 4/6%, ash from 4.24% to 6.97%, NFE from 58/02% to 63/67%, ADF from 7.8% to 12/4%, and NDF from 32/5% to 44/4%. The AMEn values of the samples ranged from 1271 to 1973 kcal/kg DM, highlighting the influence of regional and processing differences.
Regression analysis yielded several prediction equations for AMEn, with the following being the most notable:
Among these, the equation based on NFE ( ) demonstrated the highest predictive accuracy, as indicated by the highest coefficient of determination (R²), lowest standard error of prediction (SEP), and statistically significant p-values. This finding underscores the pivotal role of NFE as a single, robust predictor of the metabolizable energy content of wheat bran for broilers. The results align with previous studies, such as those by Lotfi et al. (2020) and Ning et al. (2022), though differences in absolute values and relationships are attributable to local wheat varieties, environmental conditions, and processing techniques. The study also highlights the limitations of relying on outdated feed tables or equations derived from foreign datasets, emphasizing the necessity of locally validated prediction models for Iranian wheat bran.
The observed variability in wheat bran composition and energy content underscores the importance of routine chemical analysis and the use of updated, locally relevant prediction equations in feed formulation. The inclusion of wheat bran at appropriate levels can reduce feed costs, improve gut health, and potentially enhance immune function in broilers, provided that its energy contribution is accurately estimated. The study further suggests that periodic reassessment of prediction equations is warranted, given ongoing changes in wheat cultivation and processing practices.
Conclusion
This research successfully established a practical and accurate prediction equation for the nitrogen-corrected apparent metabolizable energy (AMEn) of wheat bran produced in Iran, based on its chemical composition. The equation is recommended for use in broiler diet formulation to ensure precise energy supply and optimal performance. The significant variability in wheat bran composition observed in this study reinforces the importance of regular chemical analysis and the use of locally derived prediction models. Future research should focus on validating these findings across different broiler strains, production systems, and wheat genotypes, as well as exploring the broader effects of wheat bran inclusion on poultry health and productivity.
The authors' contributions to this article are equal.
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All authors contributed equally to the conceptualization of the article and writing of the original and subsequent drafts.
Data available on request from the authors.
The authors would like to thank all participants of the present study.
The study was approved by the Ethics Committee of the University of Tehran (Ethical code: IR.UT.RES.2024.500). The authors avoided data fabrication, falsification, plagiarism, and misconduct.
The author declares no conflict of interest.
