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Revista MVZ Córdoba

Print version ISSN 0122-0268

Rev.MVZ Cordoba vol.19 no.3 Córdoba Sept./Dec. 2014

 

ORIGINAL

Blood biochemical parameters of broilers fed differently thermal processed soybean meal

Parámetros bioquímicos en sangre de pollos alimentados con harina de soja procesada bajo distintos procesos térmicos

Mojgan Nahavandinejad,1 M.Sc, Alireza Seidavi,1* Ph.D, Leila Asadpour,2 Ph.D, Rita Payan-Carreira3 Ph.D.

1Islamic Azad University, Rasht Branch, Department of Animal Science, Rasht, Iran.
2Islamic Azad University, Rasht Branch, Department of Veterinary Medicine, Rasht, Iran.
3Animal and Veterinary Research Centre-CECAV; Department of Zootecnics, ECAV, UTAD, Vila Real, Portugal.

*Correspondence: alirezaseidavi@iaurasht.ac.ir

Received: February 2014; Accepted: July 2014.


ABSTRACT

Objective. A 42-days feeding trial was carried out to evaluate the influences of differently thermal processed soybean meal on the broilers blood biochemical parameters. Materials and methods. A total of 200 male birds of Ross strain were allocated into five different diets formulated using differently heat-treated soybean meals, with ten birds per treatment and per replicate. Diets contained: raw soybean (controls), autoclaved for a short (121°C, 20 min; Aut1 group) or medium length period (121°C, 30 min; Aut2 group) soybean meal, micro-waved soybean meal (46°C, 540 Watt, 7 min; McW group) and browned soybean meal (120°C, 20 min; Brn group). Results. Blood serum metabolites showed that all treated diets presented lower lipid metabolism makers and higher protein metabolism markers. Broilers showed increased final body weight when fed heat-treated meals compared with control. Results suggested that thermal treatments altered the lipid metabolism in broilers that might originate a decrease in abdominal fat deposition. Conclusions. Comparison of the results for all the treated groups showed the Aut2 treatment is the most suitable method for soybean thermal treatment processing; in contrast, the Aut1 treatment had the closest results to the control group.

Key words: Broiler chicken, cholesterol, processing, soybean meal, total protein (Source: CAB).


RESUMEN

Objetivo. Se llevó a cabo un estudio de 42 días para determinar la influencia de la introducción de harina de soja sometida a diferentes procesos térmicos sobre los parámetros sanguíneos bioquímicos de pollos de engorde. Materiales y métodos. Un total de 200 pollos machos, de raza Ross, fueron asignados a cinco dietas equivalentes conteniendo harina de soja sometida a diferentes tratamientos térmicos, creando grupos de10 aves por cada tratamiento y por replicado. Los tratamientos térmicos fueron: harina de soja en bruto (Grupo control), harina de soja en autoclave durante un período de tiempo corto (121°C, 20 min; Grupo Aut1) o medio (121°C, 30 minutos; Grupo Aut2), harina de soja irradiado en el microondas (46°C, 540 Watts, 7 min; Grupo McW) y harina tostada de soja (120°C, 20 min; Grupo Brn). Resultados. Todos los grupos de tratamiento mostraron una disminución delos niveles de los marcadores de metabolismo de los lípidos y un aumento del metabolismo de la proteína circulante, en comparación con el grupo control. Los pollos alimentados con dietas conteniendo soja tratada mostraron además un aumento en su peso corporal final, en comparación con los del control. Los resultados sugieren que los tratamientos térmicos interfieren con el metabolismo de los lípidos, lo que puede originar una menor deposición de grasa abdominal en los pollos. Conclusiones. La comparación de los datos obtenidos para los diferentes tratamientos térmicos identifica el tratamiento en autoclave (Aut2) como el método más adecuado para el procesamiento de la soja. En contraste, el tratamiento en autoclave (Aut1) demostró ser el método con resultados más semejantes a los del control.

Palabras clave: Dieta deharina de soja; procesamiento; colesterol; proteínas totales; pollos de engorde (Fuente: CAB).


INTRODUCTION

Growing of global population is accompanied by an increased demand for continuous and diversified food supply, which drove the need for the production of sufficient, safe, nutritious and affordable food, not only for feeding but also for people wealth. Further, livestock production plays a major social role in developing countries, while providing food, income, employment and many other contributions to rural development.

The structure of the world livestock industry changed accordingly, in several parameters, such as size, intensification, efficiency and genetic background of the animals (1).

Feeding assumed a major importance in poultry production and aims to maintain relatively low prices while increasing poultry meat and egg production. The main aspects targeted in research include the improvement of feed digestibility and feed efficiency (2); the use of least-cost and alternative ingredients in diet formulation; the interaction of feed value and nutrient metabolism on meeting bird requirements (2); influences of feed on the birds immunology and health (3); and the production of a high quality final product meeting the market requirements.

There are several factors that may affect feed and nutrient intake level, and consequently compromise the efficiency of poultry production. Among such factors, the physical form of feed, the feed flavour, the presence of anti-nutritional factors, the changes in the digestive tract microflora and the nutrient absorption are main issues that need attention.

Corn has been gradually changed by soybean in many poultry diets. Soybeans are widely used as protein sources in human and animal diets, but it contains certain anti-nutritional factors (such as the trypsin inhibitor and lectins) that may interfere with protein digestibility and absorption as well as with gut homeostasis, thus reducing of weight gain. Thereby, it is important to explore the effects of different processing methods on its nutritional quality (4), and consequently on birds health and growth rates.

Though non-thermal treatments may be used to neutralize anti-nutritional factors in soybeans (2), a wide range of heat-treatments are the most commonly used as they promote protein denaturation (4); however excessive heat-treatment may compromise also the non-deleterious protein and amino acid availability in the meal, which is particularly prejudicial on what concerns the essential amino acids and vitamins, even if overheating is avoid (2, 5). So, it is important to determine the proper heat-treatment for an adequate formulation of soybean diets.

Autoclaving, extrusion and microwave irradiation have been described as effective methods for reducing deleterious constituents from seed legumes (4). Due to differences in the methods, the success in the inactivation of non-nutritional factors surely differs between these methods, since the degree of protein denaturation depends on the intensity and duration of the thermal treatments and also on the parallel effect of pressure that is used in certain methods such as autoclaving.

The goal for the thermal processing of seed legumes for poultry nutrition is to increase the nutritional value of feed and to maximize the bird performance. To select the appropriate method for these heat procedures it is ought to compare the process outcome in the same conditions, to minimize the side effects of environmental factors on the groups' performances. However, limited research has been conducted in poultry fed soybean based diets in regard to soybean processing on blood parameters of broilers. Therefore, this study aimed to investigate the effect of different heat processing methods on the blood serum parameters in broilers.

MATERIALS AND METHODS

Study site. This study was conduct in 2011, in the poultry farm facilities and the Nutrition and Milk Industry Animal Nutrition Laboratory of the Agriculture Faculty of Islamic Azad University, Rasht Branch, Iran (37°15' N and 49°36', 5 m above sea level). The experiments lasted 42 days.

The study was approved by the Scientific Board of the Islamic Azad University, and was conducted in respect to the International Guidelines for research involving animals (Directive 2010/63/EU).

Animals. In this study, 200 male Ross 308 broilers were randomly distributed into 5 treatments with 4 replicates per treatment, in a total of 40 birds per treatment. The experiments started with one-day-old chicks, which were randomly assigned into groups with similar mean body weights, with a starting average weight of 42 g.

The experimental diets were maintained until the age of 42 days, thus covering 3 periods: the starter (1-14 days), the grower (15-35 days) and finisher (36-42 days) periods.

Soybean thermal processing and diets formulation. All thermal treatments were performed at the Nutrition and Milk Industry Laboratory of the Faculty of Agriculture, Islamic Azad University, Rasht Branch. For the heat-treatment, portions of 1.5 kg were placed into the centre of trays and then distributed homogeneously over the tray surface to achieve uniformity during treatment. After the thermal treatments, the meals were allow to cooling in a different tray before being transferred into plastic bags and stored at an adequate temperature (25°C, 60% humidity).

In this study, the five treatments evaluated and the soybean processing was as follows:

a) Raw soybean meal, originated from the Cerrado region of Brazil, as controls (Ctr group);

b) Soybean meal autoclaved at 121°C under 1 Pascal pressure (Iran TebZaeem autoclave 2000), for short or medium length treatment (respectively 20 minutes for Aut1, or 30 minutes for Aut2).

c) Soybean meal browned at 120°C (20 min; Brn group)-Soybean browning was conducted using Do 636 Memert Oven, UNB400 model, with beans poured into a special aluminium container of 2cm height, for achieving an homogeneous temperature for the entire meal. The tray entered the oven when the temperature stabilized at 120°C and remained in the oven for 20 min.

d) Micro-waved soybean meal (46°C, 540 Watt, 7 min; McW group)- Microwave treatment was performed on a household LG microwave, TCR 4284-CC. Before treated in the microwave, soybean was milled, the atmospheric humidity was determined using a psychrometer and the moisture in the sample adjusted to 25%. Afterwards, the soybeans entered the microwave within 7 cm diameter Pyrex and treated at 540 watt for 7 min.

The composition of the diets used in this study is presented in table 1. Soybean was incorporated in all the diets in a fixed proportion of 40%, 35% and 39.97% respectively in the starter, the grower and the finisher diets (Table 1).

Sampling and blood parameters. Forty birds in each experimental group were weighted at the end of the first week and at the end of the experiment, at the age of 42 days. Moreover, at the end of the feeding trials, one bird from each replicate, in a total of 4 birds for each experimental diet, was randomly selected for blood sampling.

Blood samples (~1 mL/bird) were collected from the wing veins into tubes for serum separation and rapidly transferred to the laboratory for analysis (within 2 h of collection). After centrifugation (3000 g, for 10 min at room temperature) serum was harvested.

Blood parameters analysed in this study included: glucose (GLU), cholesterol (Chol), triglycerides (TG), very low-density lipoprotein (VLDL), high density lipoprotein (HDL), low density lipoprotein (LDL), HDL/LDL ratios, uric acid (UAc), albumin (Alb), total protein (TP), calcium (Ca) and phosphorus (P). The measurements were performed with commercial kits from Pars Azmoon (Pars Azmoon Co., Tehran, Iran), according to the manufacturer's instructions. GLU was measured by a glucose-oxidase photometric assay (6), while Chol, TG, HDL, LDL and VLDL were determined by enzymatic CHOD-PAP assays, the reaction being revealed by reaction with aminoantipyrin (6). Alb was determined based on the bromocresol green method (6), whilst the UAc was determined by enzymatic methods using the uricase-TOOS method (6) and TP was assayed by the Biuret method (6). Calcium was estimated from formed kersulphetaline complex (6), and phosphorus was determined by photometric method (6) by means of UV test.

Data analysis. Data gathered during the experimental trials were organised in Excel data sheets and the statistical analysis performed with SAS® 8.0 (7). For statistical analysis the mean of replicate results was considered as the experimental unit. Data gathered in this experiment were subjected to analysis of variance using GLM procedures in a completely randomized design; before performing the analysis of variance, normality test was carried out. Mean comparisons between groups and replicates was achieved by the multi-domain Tukey test at 5% probability.

RESULTS

Data obtained in this study are summarized in tables 2 and 3. At the end of the experimental period, the soybean thermal processing influenced the final body weight (p=0.012). By week 1, the groups presenting the highest body weights were the Aut1 and McW (p=0.017 and p=0.002, respectively), whilst the Aut2 group tend to present lower weight than all others heat-treated groups (p=0.015). All treatment Aut2, Brn, and McW groups presented higher body weight than controls at the end of the study (Table 2), with Aut2 and McW groups being those with the highest values at the end of the trials (respectively, p≤0.000 and p=0.000), just fallowed by Brn group (p=0.006).

Soybean treatment did not significantly affect glucose concentration in blood (p=0.687; Table 3). The GLu concentrations in serum were similar between groups Aut1, McW and control, whilst an increase was noticed in Aut2 and Brn groups (Figure 1).

Serum Chol levels did not vary between groups (p=0.158), thought they were generally lower than control group. Still, though no differences were found in absolute serum values between soybean treatment groups (Table 3), a tendency was detected in Aut2 group to present the lowest serum values for Chol (p=0.0523; Figure 1).

Similarly, TG serum levels did not differ among the dietary groups (p=0.589). Nevertheless, lower serum levels were observed in birds fed with autoclaved and microwave irradiated meals (Table 3); Brn was the group that showed the closest values compared to Ctr (Figure 1).

Soybean thermal treatment significantly affected the HDL concentrations in broilers´ serum (p=0.043), being lower in all treated groups when compared to control (Table 3). HDL levels did not differ between groups Ctr and McW (Figure 1). Values for blood concentrations of HDL were particularly lower in groups Aut1, Aut2 and Brn and statistically different from the other groups (p<0.01; Figure 1).

Small and not significant changes were observed in the LDL absolute values between birds feed with differently treated soybean meals (Table 3). LDL serum values were lower than controls in all the treatment groups except Aut1 that showed a small increase in serum LDL concentrations (Figure 1). Still, the differences were voided of significance (p=0.584).

The HDL/LDL ratio was showed small, non-significant changes amongst all treatment groups and the controls (p=0.692), the main decrease being presented by Aut1 group (Table 3). The HDL/LDL ratio was lower than the control in all treatments despite no significant different were evident.

Soybean thermal treatment did not influence VLDL levels in the blood serum (p=0.598), despite that all treated groups presented lower blood concentrations than the control (Table 3; Figure 1). The largest changes were observed in the Aut1, Aut2 and McW groups.

Serum levels for UAc were raised in all treated groups compared with controls (Table 3); still no statistical differences were found between groups (p=0.263). Yet, a tendency was noticed to record higher UAc concentrations in broilers from groups Aut2 and McW (p=0.091 and p=0.071, respectively; Figure 1).

Heat-treatment during soybean meal processing showed to have an important impact on the blood albumin levels in broilers (p=0.016). Autoclaving of soybean meals was the thermal treatment with largest differences from controls (p=0.022 and p=0.016, respectively for groups Aut1 and Aut2), in comparison to Brn and McW groups that showed moderate changes towards controls (p=0.073 and p=0.054, respectively; Figure 1). Briefly, differences in mean values of blood albumin were significant for Aut1 and Aut2, when compared with Crt, only, and they do not differ between thermal treatments.

Blood concentrations of total proteins significantly differed among all groups (p=0.050), with major differences found between broilers with treated meals and controls (respectively p=0.027, p=0.010, p=0.043, p=0.024 for groups Aut1, Aut2, Brn and McW). Treatment groups showed higher protein serum levels than controls (Table 3; Figure 1), with major differences found in Aut1 group, whilst the mean values for the remainder groups (Aut2, Brn and McW) tend to be closer to controls (p=0.090). Briefly, the only difference observed is related with Aut1, and this treatment only differ from Crt. Total protein in serum do not varied with the other treatments

Thermal treatments did not influence the serum concentrations of Ca (p=0.789) or P (p=0.762) (Figure 1). Still, Ca average concentrations were higher for soybean treated meals than in controls (Table 3). There are no significant differences among the groups on respect to P (Table 3).

DISCUSSION

Inclusion of soybean in poultry diet demands for a balanced pre-treatment to neutralize the anti-nutritional factors to an acceptable levels without compromising the availability of essential amino acids, and therefore the nutritional quality of the diet. An adequate control of both the temperature and processing time is crucial to achieve such balance and to allow the production of an acceptable carcass both in weight and in composition.

In the present experiment we compared the effect of different heat or heat and pressure treatments on the blood serum metabolites of broilers feed soybean-based diets. Previously, it was showed that feeding birds with raw soybean meal the chicks revealed very poor feed utilization (8). In general, in the study presented herein, none of the treatments compromised nutrient availability when compared to the control (raw soybean), estimated from the body weight at the end of the experiment. Similar findings were reported in the literature for soybean submitted to different extrusion temperatures or dietary inclusion rate of wet EFFSB (extruded full-fat soybean) in meal (8).

There was a distinct disadvantage of feeding raw soybean meal on body weight in this study, so body weight of Aut2, Brn, and McW treatment birds at 42nd day of age was higher than control birds significantly. Also, some of the thermal treatments (Aut1) may not successfully destroy deleterious compounds in soybean. The body weight at 42 days in chickens fed with raw soybean or autoclaved soybean for 20 min was lower than those of birds fed with meals submitted to autoclaving for 30 min or microwave treated, although Aut1 treatment had not significant differences from the other treatments. The lowest body weight was observed in Aut1 and Brn. Therefore, the reduction of the birds' weight at the end of the trials suggests that a short (20 min) autoclaving or browning treatments were insufficient to adequately neutralise anti-nutritional substances found in raw soybean.

The differences found among body weights for the different thermal processing of the meals were not so clearly expressed by the end of the first week in birds, but it might be possible that differences were related to differences in growth rates and on the energy demands between the two periods (day 7 and day 42) for maintenance and meat production. Another explanation could be that ingestion of soybean meal submitted to different thermal treatments induces differences in intestinal microbial flora, thus interfering with the absorption ability of ingesta within the digestive tract. Still, available data from Nahavandinejad et al (9) showed that no differences were found among heat treatments on regards to total bacteria, E. coli and lactobacillus content in the cecum, although the lactic acid bacteria population increased significantly in birds fed heat-treated meals.

The combination of the temperature, pressure and length of the autoclaving treatment seemed not to be detrimental to the production of an acceptable body weight at the end of rearing (9).

In heat-treated soybean meal, particular attention must be paid to the protein content and protein quality in the final product, as thermal treatments may change the amino acid composition of diets, most importantly on the essential amino acids. Changes in protein or amino acids availability and additionally the presence of isoflavones may affect cholesterol and energetic metabolism (10). It is generally accepted that, in birds, manipulation of diets may originate modification of the profiles of metabolic hormones and metabolites in blood, alike it happens with variations due to the strain, age or sex. In the present study, blood indicators for energy, protein or lipid metabolism showed small variations amongst groups.

In data presented herein, no statistical differences were found in GLU circulating values between the treatment groups or towards the controls. However, an increased in absolute concentrations were found in birds from groups Aut2, Brn and in a lesser extent also in McW. Thought GLU levels are maintained within strict values in circulation due to a finely tuned control mechanism, these may vary with the meal carbohydrate content, the genetic lines, sex and age, stress or the husbandry conditions. Still, it is now accepted that such variations are not consistently associated with changes in body weight. Glucose is an important cellular source for energy and serves as metabolic substrate. The higher absolute values in blood GLU were found in the groups presenting heavier body weights. Nevertheless, this slight increase indirectly suggests that for the groups Aut2, Brn and McW, the thermal treatment of meals did not disturbed nutrient absorption or compromised liver glycogenolysis, in which case a decrease in GLU levels would be expected (11).

Lipid metabolites in blood are strongly associated to the energy metabolism (12). In general, elevated circulating lipids levels indicate enhanced de novo lipolysis, while low lipid profile in blood reflects an increased rate of amino acid transportation and enhanced lipid metabolism with consequent decreased in fat deposition (13). In the present study, the analysis of the lipid profile suggests an overall decrease in lipid availability in the blood of birds feed heat-treated meals.

The main changes were recorded for Chol and HDL; still, significant differences among groups were only found for HDL concentrations in blood. Moreover, the circulating values for both lipid metabolites were markedly lower than in controls compared with similar groups of Ross 308 broilers, reared under analogous management at the same station, also feed a soybean-based diet (14). This difference may be related to differences in soybean concentration of anti-nutritional factors, which may differ with the variety (15), the origin (16) or the maturation of the crops (17), or on the absorption or metabolism of cholesterol, which might be either associated to changes in the intestinal environment or to the meal content in isoflavones and fibre. Still, an increased in isoflavones would expectably be associated with an increase in total blood lipid levels, which was not the case in this experiment.

On the other hand, older studies reported that changes in nutrient availability in animals fed soybean-based meals might be related to a reduction in fat digestibility due to increased excretion of bile acids. The absolute values for total cholesterol were decreased in all the treatment groups compared to control, particularly in Aut2 and Brn group. Contrasting, blood triglycerides concentrations in blood, though decreased in comparison with controls, were more alike among groups of heat-treated meals. The Brn group presented closer values to the controls for blood TG. Triglycerides decreased values in bloodstream may suggest a decreased in the intensity in lipid metabolism and transport (12). Triglycerides are the most important source of fatty acids for fat accumulation (18), and its levels in blood correlated well with body fat. Thus, its decreased levels in blood suggest that fat deposition may be delayed in animals feed with treated soybean meals, in particular for the groups feed with autoclaved and microwaved meals. The major source for TG variations is the food or GLU conversion (11). However, a clear relation between the blood GLU levels and those for TG were not established in the present work.

As previously said, HDL concentrations in blood encompassed the lower Chol circulating levels, as naturally expected since HDL carries 70% of total cholesterol in birds (19). In the present experiment, HDL/Chol ratios were relatively similar among the groups fed soybean treated diets and the control; the content of HDL fraction varied from 57 to 61% of the total cholesterol. Still, a non-significant reduction in the HDL concentrations in blood was found in birds fed autoclaved, browned and micro-waved meals. Additionally, HDL concentrations in all the groups were below those reported by Jahanpour et al. (14) in their Ctr group, using similar chicks and environmental conditions. Being a cholesterol carrier, lower values for HDL reflect the reduction in cholesterol availability for lipogenesis in liver (19), may account for a decrease of fat deposition in carcasses. The diet is an important source of variation for HDL concentrations in blood. Thus it is possible that heat-treatment in soybean based meals might interfere either with the absorption of fat and cholesterol or with lipid metabolism.

LDL levels in bloodstream are relatively constant in birds and reflect the availability of cholesterol and triglycerides for tissue metabolism. In this experiment, despite the absence of differences between control and the meal treated groups an increased absolute value for circulating LDL was found in Aut1 group, just followed by Crt group, opposing to the Aut2 group, which showed the lowest levels.

VLDL is usually envisaged as a good indicator for fat deposition in broilers (8). Synthesised in the liver, this is the main transporter of endogenous fat and its amount correlates well with ability for fat deposition (12, 19). In the present work, though no differences were found between soybean treatments, lower absolute values were found in autoclaved and microwave irradiated meals compared to those browned. Further, VLDL concentrations in bloodstream were lower than those reported in controls from another study developed in similar environmental and dietetic conditions (14). Decreased VLDL is associated with a decrease in hepatic expression and activity of lipogenic enzymes provoking an alteration in lipids metabolism in the liver and reducing de novo fatty acid synthesis (19).

VLDL concentrations in plasma and HDL/LDL ratios obtained herein are suggestive of a limitative availability of lipids for abdominal fat deposition in all the groups, including control. This in fact is indirectly support by the increases recorded in the chicks' body weight, in particular those with heat-treated meals, since decreased lipid profile in blood has been associated with increased weight of the breast muscle and decreased abdominal fat content (20).

All the metabolites generally used as markers for the protein metabolism (TP, Alb and UAc) were increased in broilers fed heat-treated soybean meals compared to control. Total proteins in the bloodstream are a currently used parameter to estimate body condition in birds, and when taken together, TP and Alb are indicative of the protein synthesis (12). In the present study, all groups fed heat-treated meal presented significantly higher concentrations of TP and Alb in the bloodstream than Ctr. In all the groups, the concentration of albumin in plasma followed the TP concentrations. Further it also indicates that heat-treatments were beneficial for the overall protein content or the protein availability of diets, and also that the protein content in the diets was enough to support normal blood indicators for protein metabolism. Similar results have been reported by other researchers which obtained improvement of nitrogen retention in broilers following the soybean processing (8, 15).

Uric acid is a marker for protein catabolism. It corresponds to the major avian nitrogenous waste product. Changes in UAc circulating levels reflects the changes occurring in protein catabolism, even if the levels of this molecule may present individual variations in birds under standard management and nutritional conditions according to the protein content or the protein quality of the diet (12, 21). Further, UAc concentrations are directly proportional to the weight recorded in birds (2). In the study reported herein, though no statistical differences were found between groups, absolute values for UAc in bloodstream were increased in birds fed heat-treated meals in comparison to Ctr, and the higher increased were found in Aut 2 and McW meal groups. These results suggest that all the thermal treatments in this study increased the protein biological value, in particular the autoclaving for 30 min and the microwave irradiation. The presence of anti-nutritional factors in soybean meals, especially trypsin inhibitors, is an important constraint to diet protein availability (22), requesting for the use of an inhibitory treatment to decrease the activity of those substances to increase the nutritional value of the meal.

Minerals are essential for body growth. Further, they are also important players in central physiological and synthetic body processes. In the present experiment, no differences were found between groups in calcium or phosphorus concentrations in blood. Calcium is needed for bone ossification and muscle activity, while phosphorus is a major constituent of phospholipids, therefore being essential for energy accumulation.

In conclusion, the results from this experiment showed that all the tested thermal-treatments of soybean diets were advantageous rather than control (raw soybean) diet, in regard to body weight and concentrations of blood lipids and protein metabolites. Further, these essays also suggest that the heat treatment of soybean meals interferes with lipogenesis, and might reduce the abdominal fat deposition, without disturbing the protein metabolism. Comparison of the final body weight and the variations in blood metabolites demonstrated that the most suitable method for soybean thermal treatment processing was, in a decreasing order: Aut2→McW→Brn→Aut1.

Acknowledgments

We are grateful to the Islamic Azad University, Rasht Branch, Rasht, Iran for support.


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