Relative Bioavailability Value (RBV) of mineral supplementation in the broilers’ diet contains wheat and barley as sources of non-starch polysaccharide

ABSTRACT

The experiment was conducted for investigating the effect of Non-Starch Polysaccharide (NSP) feed containing wheat and barley on relative bioavailability values (RBVs) of minerals and supplementation in the broilers’ diet. A total of 72 male broiler chickens (Ross 308) were arranged with 4 repetitions (6 birds per each replicated in the metabolic cages) on the 3 treatment diets. The experimental diets contain one control diet and 2 diets with formulation of 25% wheat and 20% barley. Estimated relative mineral bioavailability values (RMBVs) were based on daily dietary mineral intake. The RBVs of Ca, P, Cu, Mn, Fe, and Zn were 44, 120, 17, 0.37, 125, and 15.38, respectively for dietary-containing wheat. Data showed that NSP contain a diet effect on bone characteristics and seed or index tibiae bone (P < 0.05). RMBVs of Ca, P, Mn, Fe, and Zn for a diet including wheat were 65.20, 84.96, 21.05, 8.50, and 2.56, respectively based on the tibia bone. Also, RMBVs of tibia bone minerals, such as Ca, P, Mn, Fe, and Zn from a diet containing barley, were 53.60, 43.33, 40.60, 44.16, and 44.69, respectively. The results of experiments indicated that Ca, P, and Fe have highly RMBVs concerning the amount of NSP contained in barley.

KEYWORDS:

• Wheat
• barley
• Non-Starch Polysaccharide
• relative mineral bioavailability values
• minerals

Introduction

The ability of cereals’ cell walls to interact with mineral elements is noticeable from the nutritional point of view (Kelsay 1986). A consequence of this issue can decrease the absorption of various minerals. Thus, for toxic mineral elements, the interaction could be considered positive, as the metal ions, bound to the dietary fibre components, may be excreted in feces. On the other hand, the availability of essential trace elements could be reduced. Cereals are one of the best sources of both dietary fibre and minerals, especially the outer parts of the grain (Pedersen and Eggum 1983a, 1983b, 1983c; Nyman et al., 1988; Fralich and Nyman 1988).

In wheat, as in the fibre of other cereals, hemicelluloses, cellulose, lignin can influence the binding of some minerals. Lignin can bind great quantities of Ca, Zn, Fe, and Mg, while cellulose binds only small quantities (Camire, et al., 1981). Total dietary fibre binds more Cu, while the fibre components, such as hemicelluloses, lignocelluloses, and lignin bind more Zn. Also, there is a strong correlation between the combined effects of protein, hemicelluloses, and lignin contents of the fibre vs. total Zn-binding capacity (Claye et al., 1998).

The major physico-chemical properties of cereals’ cell walls are the cat ion exchange capacity, hydration properties, viscosity, and compound absorptive properties (Bach Knudsen 2001).

The mineral reduction in birds occurs when fed diets with cereals rich in dietary fibres (Reinhold et al., 1975; Harland 1989). Many scientists reported that total dietary fibre barley was 15–24.1, soluble dietary fibre was 3.3–6.7 and total β-glucan was 2–5%. Thus, calcium absorption was unaffected by a barley dietary fibre, but it decreases by a wheat dietary fibre (Harring et al., 2001; Kennefick and Cashman 2000). Weber (1993), reported that the Ca-binding capacity of dietary fibre including barley has 3.5% soluble and 5.71 insoluble dietary fibre. Another study has shown that barley dietary fibre bound more copper, but less magnesium and zinc. The increase in NSP intake has possible negative effects on mineral bioavailability (Idouraine, 1995, 1996). In another way, barley dietary fibre bound more copper than zinc or cadmium (Persson et al., 1991).

The NSP should have limited mineral bioavailability because the transit time of nutrients is shortening when the NSP moves along the small intestine and thus reduces the time required for mineral absorption; thus, directly or indirectly impairing the transportation of minerals when the NSP moves across the intestinal mucosa cells. Also, electro-statistic binding and/or trapping of minerals within NSP particles leads to the formation of stable, unabsorbable mineral-fibre complexes, thus reducing the pool of ionized minerals for absorption (Harland 1989, Kelsay1986, Munoz, 1993; Laszlo 1989). The higher levels of wheat and barley cereals may negatively affect trace mineral utilization (Van der Klis et al., 1993; Carre  et al., 1994). For all the cereals most of the minerals and trace elements were recovered in the soluble dietary fibre fraction, while only small amounts could be recovered in the insoluble dietary fibre fraction. The soluble dietary fibre fraction of wheat interacted strongly with zinc, cadmium, and copper (Persson et al., 1991).

However, the low bioavailability of trace minerals and the influence of NSP contents on mineral bioavailability values occasion for the excretion of trace elements to pollute the environment. Thus, the present investigation aimed to study the effect of NSP containing wheat and barley and their characteristics on the RBVs of minerals supplementation in the broilers’ diet.

Materials and methods

Experimental design

The experiment was carried out in a completely randomized design (CRD) with 72 male broiler chicks (Ross 308) for 4 repetitions (6 birds per each replicated) in the metabolic cages. Feeding the birds according to the experimental finisher diets (21–42 days) and water was offered as ad libitum. Experimental diets include a control group and two diets, formulated for 25% wheat and 20% barley (see Table 1). The guide for the care and use of laboratory animals was followed, and the project was approved by the (CETEA) of the Federal University of Minas Gerais, (protocol number 111/2009).

Table 1. The calculated and analysis composition and nutrient content of experimental diets fed to broiler chickens (21–42 days of age).

Ingredient	Basal diet	Wheat^a	Barley^a
Yellow corn	64.00	42.37	47.33
Soybean meal	29.29	26.50	26.02
Soy oil	3.50	3.01	3.50
Wheat	–	25	–
Barley	–	–	20
DCP	1.81	1.0	1.15
Calcium carbonate	0.8	1.12	1.00
Sodium chloride	0.14	0.20	0.20
DL-methionine	0.05	0.05	0.05
L-lysine HCL	0.01	0.00	0.00
Vitamin premix^a	0.20	0.25	0.25
Mineral premix^a	0.20	0.50	0.50
Total	100	100	100
Calculated values
MEn (Kcal/Kg)	3200	3120	3100
Protein (%)	19	19	18
Met + Cys (%)	0.85	0.85	0.84
Lysine (%)	1.2	1.19	1.11
Calcium (%)	0.95	0.95	0.87
Available phosphorus (%)	0.45	0.42	0.43
Mn mg/kg	31.86	77.46	76.99
Zn mg/kg	26.02	62.45	62.04
Sodium (%)	0.15	0.15	0.15
Chloride (%)	0.22	0.23	0.23
Potassium (%)	0.87	0.87	0.88
(Na + K)-Cl (meq/kg)	231.23	231.56	231.54
NSP determination
Total NSP (%)		22.50	22.82
NSP estimation
Total NSP (%)		22.70	16.27
Soluble NSP (%)		2.97	2.95
Non-soluble NSP (%)		18.86	13.22

^a Provided per kilogram of diet: Vitamins: 44000 IU A, 17000 IU D3, 440 mg E, 40 mg K3, 70 mg B12, 65 mg B1, 32 mg B2, 49 mg Pantothenic acid, 122 mg Niacin, 65 mg B6, 22 mg Biotin, 27 mg Choline Chloride, and Minerals: 99.20 mg Mn (MnO), 85 mg Zn (ZnO), 50 mg Fe (FeSo₄₎, 10 mg Cu (Cu SuSo₄₎, 0.2 mg Se (Na2SeO3), 13 mg I (KI), and 250 mg Co.

Relative mineral bioavailability value (RMBV)

The relative mineral bioavailability value (RMBV) was calculated by establishing the relationship between the angular linear coefficient obtained for the NSP contain wheat and barley included diets (the experimental group). The linear coefficient referring to the control diet (basal diet without NSP sources) obtained from the linear regression analysis was 100 percent. The amount of RMBV of the NSP sources (wheat and barley) was calculated according to Littell et al., (1995, 1997). To determine a biological apparent ileal of feed containing sources of non-starch polysaccharides such as wheat and barley, chromic oxide (Cr₂O₃) as an indigestible marker was included at 0.3 percent in all diets. The whole ileal digest was collected individually, and measured for Cr₂O₃ and mineral concentration. Apparent ileal mineral digestibility in experimental diets was calculated using the following equation (Kadim and Moughan, 1997; Kadim et al. 2002). The means of 4 observations were considered in the statistical analysis. $\mathrm{A}\mathrm{I}\mathrm{M}\mathrm{D}=1-\left[\right(\mathrm{D}\mathrm{i}\mathrm{e}\mathrm{t}\mathrm{a}\mathrm{r}\mathrm{y}\mathrm{C}{\mathrm{r}}_2{\mathrm{O}}_3\mathrm{C}\mathrm{o}\mathrm{n}\mathrm{t}./\mathrm{F}\mathrm{e}\mathrm{c}\mathrm{a}\mathrm{l}\mathrm{C}{\mathrm{r}}_2{\mathrm{O}}_3\mathrm{C}\mathrm{o}\mathrm{n}\mathrm{t}.)\times (\mathrm{F}\mathrm{e}\mathrm{c}\mathrm{a}\mathrm{l}\mathrm{m}\mathrm{i}\mathrm{n}\mathrm{e}\mathrm{r}\mathrm{a}\mathrm{l}\mathrm{C}\mathrm{o}\mathrm{n}\mathrm{t}./\mathrm{D}\mathrm{i}\mathrm{e}\mathrm{t}\mathrm{a}\mathrm{r}\mathrm{y}\mathrm{m}\mathrm{i}\mathrm{n}\mathrm{e}\mathrm{r}\mathrm{a}\mathrm{l}\mathrm{C}\mathrm{o}\mathrm{n}\mathrm{t}.\left)\right]$AIMD = Apparent Ileal minerals’ Digestibility. The means of 4 observations were considered in the statistical analysis.

Tibia quality characteristics

Tibia characteristics, such as weight (g), length, (cm), diameter (mm), tibia volume (cm3), tibia density (g/cm³), seedor index, and ash % were measured according to Zhang and Coon (1997) and Park et al., (2003). All tibia were first weighed in the air, then reweighed while suspended in the water at room temperature. Tibia volume was calculated with the assumption that the specific gravity of water is 1 g/cm³ at room temperature. To determine bone ash content, bones were oven-dried at 105°C for 24 h and ash in a muffle furnace at 600°C for 6 h. The percentage of ash was determined in relation to the dry weight of the tibia. The Seedor index is obtained when the tibia weight is divided by its length, as proposed by Seedor (1995). The Seedor index is an indication of tibia density. If the value is high, the density of the tibia will be more.

Collection and processing of samples

During the trial (21–42 d), the amount of feed intake and total droppings output were measured quantitatively for the determination of AIMD per cage over four consecutive days. The droppings were collected daily, dried overnight at 80°C in a forced-draft oven, and collections from each pen were pooled for analysis. At the end of the trial (d 42), all surviving chicks were authorized by intracranial injection of sodium pentobarbitone and were immediately exposed to the small intestine. The contents of the lower ileum were expressed by gentle flushing with distilled water into plastic containers. The ileum was defined as that portion of the small intestine extending from the vitelline diverticulum to a point 40 mm proximal to the ileocaecal junction. The ileum was divided into 2 halves and the digesta were collected from the lower half towards the ileocaecal junction. The digested samples were frozen immediately after the collection of dried droppings. Whole ileal digesta samples were ground to pass 0·5-mm sieve and stored until chemical analysis. Examinations of mineral concentrations from sources by the ash solution were then analyzed using a flame atomic absorption spectroscopy, as described by AOAC (1990) (Spectro AA, VARIAN).

Statistical analysis

The data were analyzed by the General Linear Models (GLM) procedure (SAS 1999, Inst. Inc., Cary, NC). RBVs were determined using basal diet as the standard source by slope ratio comparisons (Littell et al., 1995, 1997). Differences among sources were determined by differences in their respective regression coefficients. Duncan’s multiple range test was used to compare each experimental group with the control group of means (P < 0.05).

Results and discussion

The results of the analyses for the nutritive value of wheat and barley used in the experiment are presented in Table 2. The nutritive value of crude protein, crude fibre, ether extract, crude ash and total carbohydrate, NDF, ADF, ADL, and NSP of both wheat and barley, are shown in Table 2.

Table 2. Nutritive values of wheat and barley used in experiments (% DM).

Nutritive value	Wheat	Barley
Dry matter	95.95	95.67
Crud protein	14.69	10.92
Crud fibre	2.75	5.43
Ether extract	1.25	0.96
Ash	1.66	2.84
NDF	13.20	30.20
ADF	0.80	6.40
ADL	1.00	2.00
CHO	82.40	85.28
Cellulose	1.80	4.40
Hemicelluloses	10.40	23.62
Total dietary fibre	17.22	30.72
SDF	1.01	4.45
USDF	16.21	25.72
NSP	18.80	35.17
NFC	69.20	55.08

Abbreviations: Acid Detergent Lignin (ADL), Neutral Detergent Fibre (NAF), Acid Detergent Fibre (ADF).

Cellulose content was calculated by difference: ADF – ADL.

Hemicellulose content was calculated by difference: NDF – ADF.

Total carbohydrate (CHO): [100 – (protein + fat + moisture + ash)].

Un-Soluble Dietary Fibre (USDF), Soluble Dietary Fibre (SDF).

Non-Starch Polysaccharide(NSP)  = Dietary Fibre + Lignin.

Non-Fibre Carbohydrate is calculated (NFC) by difference [100 – (NDF + CP + Fat + Ash)].

Data presented that NSP supplementation in diets containing wheat and barley, did not affect biological apparent ileal digestibility values of mineral diets (Table 3). Data obtained from experiments showed that the P digestibility of the diet containing wheat and barley was relatively higher. This may be attributed to the endogenous enzyme role activity that relays the play of P in the phytate content of wheat and barley in the diet to improve the apparent ileal digestibility. Because, P in phytate is largely unavailable and phytate can bind multivalent minerals, thus reducing their availability (Van der Klis et al., 1997; Camden et al., 2001; Rutherfurd et al., 2012). However, fewer studies have focused on the possible effects of NSP on minerals other than P, and on improved mineral availability general as Ca absorption (Ravindran et al., 2008; Santos et al., 2008; Saima et al., 2009; Rutherfurd et al., 2012), Fe (Um et al., 2000). Thus, other studies have shown no effect for the same minerals, Ca (Um et al., 2000) and Fe (Rutherfurd et al., 2012).

Table 3. Biological apparent ileal digestibility (g/100 g) of diets included wheat and barley for broiler chickens^a (21–42-d-old).

Minerals	Wheat^b	Sig. level	SE	Barley^c	Sig. level	SE
Ca	0.39 ± 0.04	NS	0.01	0.34 ± 0.09	NS	0.02
P	0.51 ± 0.33	NS	0.05	0.46 ± 0.05	NS	0.02
Cu	0.34 ± 0.10	NS	0.02	0.26 ± 0.05	b	0.02
Mn	0.47 ± 0.06	NS	0.02	0.37 ± 0.32	NS	0.05
Fe	0.19 ± 0.15	NS	0.02	0.18 ± 0.02	NS	0.02
Zn	0.18 ± 0.04	NS	0.01	0.16 ± 0.10	NS	0.01

^a The number of each sample is 4 replicated with 24 birds.

^b Diets included 25% wheat with 22.77% total NSP.

^c Diet included 20% Barley with 22.82% total NSP.

NS = Non-Significantly; SE = Standard Error.

Regression was calculated based on daily dietary analyzed minerals such as Ca, P, Cu, and Mn, Fe, and Zn intake during the experiment period (Table 4). RMBVs of NSP sources based on the slope ratio of wheat are present in Table 5. Linear regression relationships were observed in all minerals, so the RMBVs were estimated based on daily dietary minerals intake. When the response to the control diet was set at 100%, the estimated relative mineral bioavailability of Ca, P, Cu, Mn, Fe, and Zn was respectively 44, 120, 17, 0.37, 125, and 15.38 for the NSP content of wheat. The bioavailability of minerals was defined as the proportion of an ingested element that is absorbed, transported on its action, and converted to a physiologically active form. Therefore, for the assessment of bioavailability target tissue accumulation of minerals has a criterion. The bioavailability value of Fe (125%) is higher than that of other minerals (Cao et al., 1996). Thus, bioavailability values of Mn are lower than those of other minerals and it has been under influence of NSP containing wheat. Wheat, as a NSP (soluble, insoluble), can influence the binding of greater quantities of some minerals, such as Ca, P, and Fe (Camire, et al., 1981). While, cellulose or total dietary fibre (insoluble) binds only small quantities of Mn, Zn, and Cu from broiler ration (Camire, et al., 1981). In contrast, Claye et al., (1998) reported that total dietary fibre bound more Cu, while the fibre components, such as hemicelluloses, lignocelluloses, and lignin bound more Zn. As a result, physicochemical properties of dietary fibre are the cation exchange capacity, viscosity, and compound absorptive properties (Bach Knudsen 2001). The reduction in mineral availability in birds when fed diets with cereals that are rich in fibres (Reinhold et al., 1975; Harland 1989) has been associated with their fibre content and with the amount of phytic acid, which is also implicated in lowering cation bioavailability (Davies and Nightingale 1975; Ismail-Beigi et al., 1977; Brink et al., 1991). The soluble fibre fraction of wheat interacted strongly with zinc, cadmium, and copper (Persson et al., 1991). Van der Klis et al., (1993) suggested that an increase in intestinal intraluminal viscosity decreases mineral absorption. The introduction of higher levels of wheat may negatively affect trace mineral utilization due to their higher viscosity (Carre et al., 1994).

Table 4. Linear regressions equation of mineral concentrations on daily dietary NSP content of wheat.*

Minerals	Regression equation	SEM	Significant level
Ca	Y = 27.90 + 0.115χ	21.2	*
P	Y = 16.69 + 0.429 χ	17.2	*
Cu	Y = 35.96 + 0.002 χ	35.2	NS
Mn	Y = 39.40 + 0.0004χ	59.2	NS
Fe	Y = 12.41 + 0.0006 χ	06.2	**
Zn	Y = 36.52 + 0.0002χ	42.2	NS

*Number of each sample is 4 replicated with 24 birds.

SEM = Standard Error of Means.

Table 5. Regression coefficient and Relative Mineral Bioavailability Value (RMBV) of wheat in the 42 d-old chickens.

		Regression coefficient
Minerals	Relative Bioavailability Value (RBV)	SE	Slope
Ca	44	0.06	0.11
P	120	0.20	0.42
Cu	17	0.001	0.002
Mn	0.37	0.00016	0.000005
Fe	125	0.00027	0.00065
Zn	15.38	0.00016	0.0002

SE = Standard Error.

Estimation of the relative mineral biological availability was obtained by the ratio of the slopes from the linear regression equations (Tables 6 and 7). When the slope of the regression control diet was set equal to 100%, based on the NSP content of barley RMBVs 190, 111, 14, 8.33, 154, and 10 was obtained respectively for Ca, P, Cu, Mn, Fe, and Zn. The result of the experiment indicated that Ca, P, and Fe were highly RMBVs concerning the amount of NSP contained in barley. This is according to Harring et al., (2001) who report calcium absorption was unaffected by a barley dietary fibre but was decreased by a wheat dietary fibre (Kennefick and Cashman 2000). Another way, Weber (1993) reported that there was no correlation between total Ca bound and phytic acid in barley. In a similar study, barley fibre bounded with more copper, but less magnesium and Zinc (Idouraine et al., 1995).

Table 6. Linear regressions equation of mineral concentrations on daily dietary NSP content of barley.

Minerals	Regression equation	SEM	Significant level
Ca	Y = 118.37–0.74χ	11.09	**
P	Y = 62.89 -0.39 χ	11.48	NS
Cu	Y = 34.66 + 0.002 χ	12.59	NS
Mn	Y = 35.43 + 0.0001χ	12.76	NS
Fe	Y = 73.03 + 0.0008 χ	30.11	NS
Zn	Y = 36.06 + 0.0001χ	12.85	NS

SEM = Standard Error of Means.

Table 7. Regression coefficient and Relative Mineral Bioavailability Value (RMBV) of barley in the 42-d-old chickens.

		Regression coefficient
Minerals	Relative Bioavailability Value (RBVs)	SE	Slope
Ca	190	0.40	−0.75
P	111	0.25	−0.39
Cu	14	0.003	0.002
Mn	8.33	0.0003	0.0001
Fe	154	0.00045	0.0008
Zn	10	0.0012	0.0001

SE = Standard Error.

But, Cu, Mn, and Zn have less RMBVs. However, these reductions in mineral relative mineral biological availability in birds when fed ration that content barley, are associated with their NSP and also implicated in lowering cations’ bioavailability (Reinhold et al., 1975; Harland 1989; Davies and Nightingale 1975; Ismail-Beigi et al., 1977; Brink et al., 1991). Thus, Persson et al., (1991) showed that barley fibre has bound more copper, than zinc or cadmium. In other words, published research reported that minerals’ bioavailability of cereals is used in animal sources poorly by monogastric animals. Endogenous and exogenous factors have been implicated in the reduction of mineral absorption from cereals (Van der Klis et al., 1993, Carre  et al., 1994).

The mineral concentration of the tibia bone been obtained from the diet content of the NSP form of wheat and barley is shown in Table 8. Literature review shows that bone mineral density values are affected by many factors, such as age, gender, type of production, diet, and management. Almeida Paz et al., (2006) suggested that the tibia bone is the main bone supplying the Ca requirement (Jonquière and Carencro 2004).

Table 8. Effect of dietary NSP content of wheat and barley on tibia mineral concentration in the 42-d-old chickens.

Minerals	Wheat	Barley	Significant level
Ca (%)	15.09 ± 1.64	14.43 ± 1.41	NS
P (%)	6.10 ± 1.07	6.01 ± 0.15	NS
Mn (mg/kg)	16.20 ± 0.60	15.85 ± 1.05	NS
Fe (mg/kg)	387.90 ± 19.5	372.80 ± 36.50	NS
Zn (mg/kg)	193.25 ± 20.05	169.60 ± 4.00	NS

The results of tibia quality characteristics such as weight, length, diameter, bone volume, bone density, and Seedor index (SI) of chickens are presented in Table 9. Data show that NSPs affected tibia bone quality characteristics and Seedor index tibiae, respectively (P < 0.05). This is similar to Onyango et al., (2003) who reported that where birds fed with a mineral diet (Zn, Mn, and Cu) showed improved tibia weight, length, diaphysis diameter, weight/length index, and tibia robust city index. The result of the tibiae bone volume value showed differences significantly in the effect of both NSP sources (P < 0.05), this result is consistent with Garlich et al., (1982).

Table 9. Mean values of tibia bone quality characteristics for broiler chickens (42-d-old).

Characteristics	Wheat	Barley	Significant level
Weight (g)	6.97 ± 0.10	6.93 ± 0.10	*
Length, (cm)	10.29 ± 0.01	10.73 ± 0.18	*
Diameter (mm)	7.50 ± 0.50	7.44 ± 0.54	*
Bone volume (cm^3)	9.50 ± 0.50	10.00 ± 0.00	*
Bone density (g/cm^3)	0.73 ± 0.02	0.69 ± 0.0	NS
SI*	67.73 ± 0.1	64.58 ± 0.005	*
Ash %	36.69 ± 3.84	35.50 ± 0.16	NS

*Seedor Index.

Bone mineral density is one of the most important factors to measure bone quality. It can also be measured using bone mineral composition, bone breaking strength, and Seedor index (Seedor, 1995), among others (Orban et al., 1983). But our experiment had shown that NSP sources did not affect tibia mineral density. As agreed with Zhao et al., (2010) who reported that broilers fed diets supplemented with 40 mg Zn + 60 mg Mn + 8 mg Cu as OTM/kg diet did not affect tibia strength. Seedor et al., (1995) showed that the higher the bone weight/bone length index, the denser the bone (Monteagudo et al., 1997; Reisenfeld 1972). Our experiment showed that the Seedor index values were significantly different for two NSP sources, as values ranged from 67/73 for wheat to 64/58 for barley. Zhang and Coon (1997) found that breaking strength, also called bone strength, is not a function of bone ash percentage but rather a function of bone volume (Geraldo et al., 2004a, 2004b). Bone volume is considered in the Seedor index. However, these measures are very important when measuring bone quality as they are closely related. As a result, bone strength and volume, as well as bone density, are significant traits in the breeding of birds on the shelf. And it needs to be considered by nutritionists.

Regressions were calculated based on the dietary minerals intake content of wheat and barley in the experiment (Tables 10 and 11). The linear regression value of tibia bone mineral concentration added to dietary NSP source from the wheat and barley resulted in an equation with a linear model. The slope for Ca (wheat) and Fe (barley) is higher than those for P, Mn, and Zn. Relative mineral bioavailability estimates of NSP source based on linear regression slope for the tibia bone concentration are shown in Tables 12 and 13. RMBVs of wheat, such as Ca, P, Mn, Fe, and Zn were respectively 65.20, 84.96, 21.05, 8.50, and 2.56 based on the tibia bone (Table 12). Thus, RMBVs of the tibia bone of barley, such as Ca, P, Mn, Fe, and Zn, were respectively 53.60, 43.33, 40.60, 44.16, and 44.69 (Table 12). Our experiment data showed that Zinc and Fe elements unlike Ca, P, and Mn are absorbed in the intestinal lumen for tibia bone retention (Wong-Valle et al., 1988; Underwood 1977). The reason for this different solubility of minerals is the content of wheat and barley source. Thus, there may be a limitation of different molecular weight ligands of NSP content of wheat and barley for bonding minerals.

Table 10. Linear regressions equation of tibia bone mineral concentrations on daily dietary NSP content of wheat.^a

Minerals		SEM	Significant level
Ca	Y = 119.73 + 2.08χ	17.75	NS
P	Y = 41.64 + 6.34 χ	4.086	**
Mn	Y = 429.21 + 146.79χ	876.63	NS
Fe	Y = 31550.0−6.46χ	7745.71	NS
Zn	Y = 61417.0 + 6.97χ	3856.01	NS

^a The number of each sample is 4 replicated with 24 birds.

Table 11. Linear regressions equation of tibia bone mineral concentrations on daily dietary NSP content of barley.^a

Significant level		SEM	Minerals
Ca	Y = 1389.243 + 1.71χ	13.61	NS
P	Y = 301.86−32.63 χ	19.74	a
Mn	Y = 8175.3−2831.65χ	22.002	NS
Fe	Y = 55434 + 36.26χ	12294	NS
Zn	Y = −1551.0 + 121.79χ	4050/13	a

^a Number of each sample is 4 replicated with 24 birds.

Table 12. Regression coefficient and Relative Mineral Bioavailability Value (RMBV) of bone minerals from wheat in the 42-d-old chickens.^a

Relative Bioavailability Value (RBV)			Regression coefficient
Minerals		SE	Slope
Ca	65.20	4.8	20.08
P	84.96	2.25	6.34
Mn	21.05	237.56	146.79
Fe	8.50	122.62	6.46
Zn	2.56	43.61	6.97

^a Number of each sample is 4 replicated with 24 birds, SE = Standard Error of Means.

Table 13. Regression coefficient and Relative Mineral Bioavailability Value (RMBV) of bone minerals from barley in the 42-d-old chickens.^a

Relative Bioavailability Value (RBV)			Regression coefficient
Minerals		SE	Slope
Ca	53.60	15.89	32.63
P	433.33	15.89	32.63
Mn	406.01	74.22	28.36
Fe	44.16	167.90	36.26
Zn	44.69	60.91	121.79

^a N. The number of each sample is 4 replicated with 24 birds. SE = Standard Error.

According to the result of the data, the retention of each mineral in the tibia bone was not constant and varies for each NSP source. Another way, retention of each mineral in tibia bones has more sensitivity to dietary sources, such as wheat and barley. Tibia minerals are recognized as the variables of choice in the calculation of the RMBV (Cook 1973; Lo et al., 1980; Ranhotra et al., 1976). These variable responses on the NSP source were used to calculate the RMBV of minerals in wheat and barley based on diets. The RMBV was calculated based on tibia minerals, as follows: $\begin{array}{rl}\mathrm{R}\mathrm{M}\mathrm{B}\mathrm{V}& =\left(\mathrm{T}\mathrm{i}\mathrm{b}\mathrm{i}\mathrm{a}\mathrm{m}\mathrm{i}\mathrm{n}\mathrm{e}\mathrm{r}\mathrm{a}\mathrm{l}\mathrm{s}\text{–}Y\text{-}\mathrm{i}\mathrm{n}\mathrm{t}\mathrm{e}\mathrm{r}\mathrm{c}\mathrm{e}\mathrm{p}\mathrm{t}\right)\times \\ & 100/(\mathrm{s}\mathrm{l}\mathrm{o}\mathrm{p}\mathrm{e}\mathrm{o}\mathrm{f}\mathrm{r}\mathrm{e}\mathrm{g}\mathrm{r}\mathrm{e}\mathrm{s}\mathrm{s}\mathrm{i}\mathrm{o}\mathrm{n}\mathrm{l}\mathrm{i}\mathrm{n}\mathrm{e}\mathrm{r}\mathrm{e}\mathrm{l}\mathrm{a}\mathrm{t}\mathrm{i}\mathrm{n}\mathrm{g}\mathrm{t}\mathrm{i}\mathrm{b}\mathrm{i}\mathrm{a}\mathrm{m}\mathrm{i}\mathrm{n}\mathrm{e}\mathrm{r}\mathrm{a}\mathrm{l}\mathrm{s}\times \\ & \mathrm{m}\mathrm{i}\mathrm{n}\mathrm{e}\mathrm{r}\mathrm{a}\mathrm{l}\mathrm{s}\mathrm{i}\mathrm{n}\mathrm{t}\mathrm{a}\mathrm{k}\mathrm{e})\end{array}$

Using this method, the Relative Mineral Bioavailability Value (RMBV) of minerals in wheat and barley was significantly different for both NSP sources except for the Mn value (Table 14) (based on reference diet = 100). However, using this method RMBV of minerals significantly have a low difference (Table 14). The apparent retention or RBVs in the tibia of minerals in wheat and barley ranged Ca 33.19–44.39, P 6.84–9.88, Fe 7.71–2.26, and Zn 44.0–0.06% receptivity. These differences may be dependent on physicochemical properties and cation exchange capacities or compound absorptive properties (Bach Knudsen 2001; Van der Klis et al., 1993). Also, levels of wheat and barley may be negatively affected by trace mineral utilization due to their higher viscosity (Carre  et al., 1994). However, in cereals, most of the trace elements were recovered in the soluble fibre fraction, while only small amounts of them could be recovered in the insoluble fibre fraction (Person et al., 1991).

Table 14. Relative Bioavailability Value (RBV) of tibia bone Minerals on broiler chickens.

	Wheat	Barley	SEM*	Significant level
Ca	33.19^b	44.39^a	2.96	**
P	6.84^d	9.88^c	1.46	**
Mn	0.01^c	0.011^c	0.04	NS
Fe	7.71^a	2.26^b	0.41	**
Zn	44.0^a	0.06^b	8.43	**

*Standard Error of Mean.

Conclusion

The present data demonstrated that the RMBVs for diet-containing wheat would be respectively 65.20, 84.96, 21.05, and 8.50, 2.56 for Ca, P, Mn, Fe, and Zn. Also, diets containing barley RMBV are 53.60, 43.33, 40.60, 44.16, and 44.69, respectively. Under the conditions of the present study, NSP in diet had affected the tibiae bone for Ca from diet included wheat. The diet that included barley Fe digestibility has been higher than those for P, Mn, and Zn.

The present study shows that under these conditions, RMBVs of Ca, P, Cu, Mn, Fe, and Zn for a diet that contains wheat as NSP sources were, respectively, 44, 120, 17, 0.37, 125, and 15.38. RMB values of diets that contain barley are 190, 111, 14, 8.33, 154, and 10, obtained from Ca, P, Cu, Mn, Fe, and Zn, respectively.

Disclosure statement

No potential conflict of interest was reported by the author(s).