The effects of dry heat processing, autoclaving and enzyme supplementation on the nutritive value of wheat for growing Japanese quails

Abstract

Two experiments were conducted to study the effect of autoclaving and heat processing (HP) and enzyme supplementation on wheat nutritive value for quails. In the first experiment, 72 male quails (13 weeks) were used to determine apparent metobalisable energy corrected for nitrogen (AMEn) of wheat samples. In the second experiment, 720 seven-day-old as-hatched Japanese quail were randomly assigned to a 3×3 factorial design. Factors include three processing methods (untreated, autoclaving and HP) and three levels of enzyme (0, 0.25 and 0.5 g/kg). Each treatment group consisted of 4 replicates of 20 birds. According to the results, the total and insoluble none starch polysaccharides (NSP) and insoluble to soluble NSP ratio increased by processing (P<0.01) and also total and insoluble β-glucan increased by processing (P<0.01). The amount of AME, AMEn, gross energy efficiency and dry matter digestibility of wheat has significantly increased by autoclaving (P<0.05). Quails performance was increased by wheat autoclaving (P<0.05). However, wheat dry heat processing had no significant effect on performance. Adding enzyme to diet significantly improved quails performance. By autoclaving wheat, carcass and breast weight significantly increased (P<0.05). Adding enzyme to diet significantly increased breast and thigh weight (P<0.05). In conclusion, we can use autoclaving, in spite of enzyme supplementation, to improve growth rate and feed conversion ratio of growing quail fed diets based on wheat.

Keywords:

• autoclaving
• enzyme
• heat processing
• quail
• wheat

Introduction

Corn is the high-energy grain favoured by most poultry nutritionists and poultry producers. However, it is not always available at an economic price. Wheat may be a more economic and readily available alternative. One of the benefits of wheat is that it contains 12–14% protein, compared with about 8.5% protein in corn (NRC 1994). As a result, less soy-bean meal has to be used in wheat-based diets to achieve the protein level necessary in the quail diet. Wheat varies considerably in chemical composition, which probably reflects varietal differences and variation in growing conditions. The presence of none starch polysaccharides (NSP), and in particular arabinoxylans, gives the greatest cause for concern, because these substances are not well digested, especially by young birds. Unabsorbed arabinoxylans are soluble in water and because of their molecular structure the resultant solution is very viscous. Research indicates that such viscous digesta interfere with digestion and absorption of most nutrients. Choct and Annison (1992) attribute the poor digestibility of wheat to their presence. The anti-nutritive activity of pentosans found in wheat has been highlighted in numerous studies, where growth rate, nutrient digestibility and feed conversion ratio (FCR) have all been depressed in broilers fed on diets based on wheat (Choct and Annison 1992). Wheat is mostly excluded from the diet prepared for growing quail because of its poor digestibility due to the high content of NSP. Birds do not possess the enzymatic capability to digest dietary fibre components, mainly mixed-linked β-glucans (Annison 1991). Various treatments have been used to improve the nutritive value of wheat-based diets for chickens. Supplementation of wheat-based diets with pentosanase can improve utilisation of wheat NSP by chickens (Crouch et al. 1997).

Several conventional food processing methods like heating, autoclaving, soaking, germination and fermentation have been successfully used to either eliminate or reduce these anti-nutrients in foods (Svihus et al. 1997; Al-Kaisey et al. 2002; Owoyele et al. 2003; Skrede et al. 2003, 2007). In recent years, there has been considerable interest in the use of heat treatment to increase the nutritional values of feed ingredients (Niu et al. 2003). Heating cereals at temperatures above 95°C is common practice for improving performance of piglets (Medel et al. 2004; Mateos et al. 2007). However, heat processing (HP) of ingredients for inclusion in poultry diets is not well documented. Gracia et al. (2003) reported that HP of wheat improved body weight gain (BWG) in broilers in the early stages of growing and that the beneficial effects of HP disappeared with age. HP of wheat modifies the physical and chemical structure of the cereal, improving accessibility of enzymes to the dietary components and facilitating its utilisation (Gracia et al. 2008). Plavnik and Sklan (1995) reported that dry extrusion of barley increases the AME of diets by 2.2%. Application of heat partly solubilises the starch and the fibre components of the cereal and increases viscosity. HP of cereals gelatinises starch to some extent (Medel et al. 2000), facilitating its endogenous enzymatic degradation, and solubilises fibre components that might enhance the activity of exogenous enzymes (Osman et al. 1990; Vukic Vranjes and Wenk 1995) and partly solubilises fibre constituents (Fadel et al. 1988). In contrast, Herstad and McNab (1975) concluded that HP of barley did not have any effect on performance of broilers at any age. Scott et al. (2003) demonstrated that pelleting destroyed endogenous phytase and NSP enzymes in wheat-based diets and increased the levels of soluble NSP, but did not improve performance of broilers, possibly explained by changes in the water hydration rate in the gut. Autoclaving rye greatly potentiated the growth response to dietary pentosanase while producing little or no effect without enzymes (Teitge et al. 1991).

However, few studies have been carried out to investigate the effect of processed wheat, autoclaving and Heating alone or in combination with exogenous enzymes in quails (Okan et al. 1995). Therefore, the objectives of the experiments reported were to evaluate effects of heating, autoclaving, and enzyme treatments on wheat nutritive value for quails.

Materials and methods

Apparent metobalisable energy

The reference diet that calculated nutrients for net NRC (1994) quail requirement is presented in Table 1. Diet was diluted with 40% finely ground wheat samples and then mixed with 0.5% chromic oxide, which was used as a marker for determination of the AME and AMEn. AME and AMEn were estimated by difference methods using the following equation:

Table 1. Composition of reference diet and experimental quail diets as formulated and as calculated from analysed composition of the ingredients (g/kg).

Ingredients	Reference diet	Test diet	Experimental diet
Untreated or treated wheat	0	400	600
Corn	581	348.6	0
Soybean meal (44%)	316.9	190.1	297.0
Corn gluten meal (64%)	66.7	40.0	55.6
Soy oil	0	0	11.9
Oyster shell	13.4	8.04	13.5
DCP	8.4	5.04	7.7
Salt	2.9	1.74	2.3
Micro minerals^a	2.5	1.5	2.5
Vitamin premix^b	2.5	1.5	2.5
L-threonine	1.3	0.78	2.1
DL-methionine	1.1	0.66	1.2
L-lysine HCl	3.2	1.92	3.6
Safizyme	0	0	0, 0.25 or 0.5 g/kg
Total	1000	1000	1000
Calculated composition
Crude protein (%)	24	18.7	24
ME (kcal/ kg)	2900	3140	2900
Calcium (%)	0.8	0.48	0.8
Avail. phosphorus (%)	0.3	0.21	0.3
Lysine (%)	1.3	0.9	1.3
Met + cys (%)	0.89	0.67	0.84
Threonine (%)	1.022	0.72	1.02
^aSupplemented kg^−1 diet; Fe 50 mg, Mn 102 mg, Zn 70 mg, Cu 10 mg, I 0.5 mg, Se 0.2 mg.
^bSupplemented kg^−1diet; Vitamin A 12,000 IU, Vitamin D3 360 IU, tocopheryl acetate 50 mg, Vitamin K3 33 mg, thiamine 2.5 mg, riboflavin 12 mg, pyridoxine 4.5 mg, pantothenic acid 16.65 mg, biotin 0.26 mg, folacin 2 mg, niacin 50 mg, Vitamin B12 0.025 mg.

Gross energy efficiency (GEE) was calculated AMEn as a proportion of the gross energy.

Male quails (13 weeks old) were used in this study. Each dietary treatment was replicated six times with four quails per replication. The experiments were conducted in a well-ventilated open shed with ceiling fans. The birds received artificial light for about 16 h with intensity 20 lux and had free access to water and diets during the experiments. Four quails were placed in the cages with dimensions 25 cm long×21 cm wide×25 cm high. Each cage was provided with an individual feeder, a drinker and a plastic-covered tray for collection of excreta. The birds were fed with the experimental wheat for 4 days and the excreta were collected twice daily at 12-h intervals.

Birds, diets, experimental design, and data collection

The experiment was conducted to study different processing methods of wheat with or without supplemental enzyme on performance of quails. The birds were randomly assigned to a 3×3 factorial design. Factors included: three processing methods (untreated, heating and autoclaving) and three levels of enzyme (0, 0.25 or 0.5 g/kg). Each treatment group consisted of four replicates of 20 birds. There was no blocking criterion. Used enzyme (SAFIZYM GP 800, Saf Agri USA/Lesaffre Feed Additives) contained mainly β-glucanase and xylanase activities. The β-glucanase and xylanase activities, as determined by the manufacturers, were endo-1,4-β-glucanase activity min 800 units/kg diet; endo-1,3(4)-β-glucanase activity min 1800 units/kg diet and endo-1,4-β-xylanase activity min 2600 units/kg diet for enzyme. A total of 720 seven-day-old (26.4±5) as-hatched Japanese quail (Coturnix coturnix japonica) were used in the study, obtained from the hatchery of animal research station of Tehran University. The breeder population was selected for FCR and BWG for several years (Khaldari et al. 2010 and Varkoohi et al. 2010, 2011). Birds were kept in wire cages (60×100×50 cm) in groups of 20 birds in a temperature-controlled windowless room. The target room temperature was initially set at 38°C and was then gradually decreased during the first 20 days of life to 20°C. Diets and fresh water was offered ad libitum. Lighting schedule was 23L: 1D throughout the experiment. Ingredients and chemical composition of the experimental diet are shown in Table 1. The experimental diet was wheat-based to meet or exceed the nutrient requirements of growing quail (NRC 1994). Experiment procedures adopted in the study were in accordance with animal welfare norms. During the experimental period, the growth performance of quail was evaluated by recording weight gain (WG), feed intake (FI) and FCR. Individual BW of quail was recorded at the beginning of the experiment and on a weekly basis thereafter. The FCR was calculated weekly as the amount of feed consumed per unit of BWG. Water consumption was recorded weekly by checking the volume of water left in the drinkers at the end of each day and subtracting this from all water allocated to each drinker in the preceding 24-hour period, then water to feed intake ratio (WFR) was calculated. At the end of the experiment, six quails (three male and three female) whose body weights were similar to the group average were selected from each of the replicate groups in each treatment and slaughtered by severing the jugular vein, to determine some measurements of carcass yield. They were then plucked, eviscerated, and carcasses were kept for 4 h at 4°C, then each carcass without feet was weighed (empty carcass weight). Carcass yield was calculated as the ratio of empty BW relative to live BW. Thigh quarters were obtained by separating the thigh from the back at the joint between femur and ilium, and by separating the tibia and shank at the hock joint (Yalçin et al. 1995). The whole breast portion was obtained by cutting through the ribs, thereby separating the breast portion from the back (Yalçin et al. 1995). In order to reduce variation in the cutting procedure, one operator carried out all dissections. Part of yields refers to the part weight/eviscerated weight ratio. Carcass yield refers to eviscerated weight/live body weight ratio.

Processing procedure

Autoclaving (AUP)

Wheat was autoclaved at 120°C (15 p.s.i.) for 45 min in a batch weighing approximately 20 kg. Each lot was placed to a depth of 5 cm in a specially constructed wire-bottomed autoclave tray followed by spreading on a heated floor and air-dried at 35–40°C for 7 days (Skrede et al. 2001).

Dry heat processing (DHP)

Wheat was heated by oven at 70°C for 45 min where each lot was placed to a depth of 2 cm in oven trays (Owoyele et al. 2003).

Laboratory analyses

Dry matter (DM), ash, crude protein (Kjeldahl-N×6.25) and fat, calcium and phosphorus were determined by the AOAC (1980) methods. Soluble and insoluble NSPs and dietary fibre were determined by using a modified method based on AOAC (2005) method 991.43 ‘total, soluble and insoluble dietary fibre in foods’ and AACC (2009) method 32-07 ‘determination of soluble, insoluble and total dietary fibre in foods and food products’. This method is the simplified modification of the AACC soluble/insoluble dietary fibre method, 32-21. Briefly, 1 g of dried wheat sample (in duplicate) was subjected to sequential enzymatic digestion by heat-stable α-amylase, protease and amyloglucosidase. Subsequently, insoluble NSPs (INSPs) were filtered and the residue was washed with warm distilled water. Combined solution of the filtrate and water washings was precipitated with four volumes of 95% ethanol for soluble NSPs (SNSPs) determination. The faecal samples from each replicate were mixed and dried in an oven at 65°C until they reached a constant weight. The dried feed and excreta samples were ground and assayed for gross energy using a Gallenkamp Ballistic Bomb Calorimeter (Model No. CBA 101 AB 1C). The concentrations of chromic oxide in the excreta and wheat samples were measured using procedure described by Williams et al. (1962) and the apparent metabolisable energy calculated (Choct et al. 1995) as follows:

where Cr₂O₃fd = Chromic oxide/g feed; Cr₂O₃ec=Chromic oxide/g excreta; GEfd=Gross energy/g feed; GEec=Gross energy/g excreta; Nfd=Nitrogen/g feed; Nec=Nitrogen/g excreta.

Statistical analyses

Data were analysed as a completely randomised design and subjected to ANOVA using the GLM procedure of SAS software (SAS Institute Inc., 2001). One-way ANOVA was used to analyse the data from the NSPs and AMEn. Root mean square error (RMSE) for each parameter was calculated as the square root of the residual mean squares of the one-way ANOVAs. The data from the performance experiments were analysed by two-way ANOVA using a general linear model (effects of processing (n=3), levels of enzyme (n=3) and their interaction. Significant differences among treatment means were determined at P<0.05 by Tukey's test (Steel and Torrie 1980) when significant F values were obtained.

Results

Effects of processing on wheat chemical composition

Chemical composition of differently treated wheat is presented in Table 2. Analysis of untreated and processed wheat revealed significant effects on total and soluble and insoluble NSP, β-glucans, GEE and total dietary fibre (Table 2).

Table 2. Influence of wheat processing on chemical composition (g/kg on dry matter basis) and AME and AMEn values (kcal/kg dry matter).

	Untreated	Heated	Autoclaved	RMSE	P-values	R ^2
DM	93.15	94	93	NA	–	–
Crude protein	111.6	114.2	110.7	NA	–	–
Ether extract	24.5	20.1	20	NA	–	–
Total ash	15	20.6	20	NA	–	–
NSPs
Total	112^c	127^a	118^b	2.84	0.01	0.86
Insoluble	93.5^c	110^a	100^b	2.82	<0.01	0.88
Soluble	18.5^a	17.0^b	18.5^a	0.47	0.02	0.75
Insoluble/soluble ratio	5.06^c	647^a	5.42^b	0.20	<0.01	0.91
β-glucans
Total	4.97^b	5.55^a	5.07^b	0.10	<0.01	0.87
Insoluble	3.25^c	4.05^a	3.62^b	0.07	<0.01	0.96
Soluble	1.72^a	1.50^b	1.45^b	0.07	<0.01	0.74
Insoluble/soluble ratio	1.89^c	2.70^a	2.50^b	0.09	<0.01	0.94
AME	2993^b	3018^b	3114^a	50.2	0.01	0.55
AMEn	2990^b	3016^b	3115^a	21.1	0.01	0.84
GEE	72.4^b	74.5^ab	76.0^a	1.2	0.04	0.88
Dry matter digestibility	70.5^b	70.5^b	74.2^a	3.11	0.03	0.46
Note: Mean values within a row with no common letters are significantly different (P ≤ 0.05) as determined by least significant difference comparison.
RMSE, root mean square error (one-way ANOVA); NA, not analysed; GEE, gross energy efficiency=(AMEn/GE)×100.

Total and insoluble β-glucans and NSP increased significantly during DHP and AUP, soluble β-glucans and NSP decreased (P<0.01). Insoluble to soluble ratio of β-glucans and NSP increased by processing (P<0.01). The amount of wheat AME, AME_n and GEE were significantly increased by autoclaving (P<0.05). With AUP and DHP AME_n 4.18 and 0.86% increased, respectively. Dry matter digestibility increased significantly by AUP processing.

Effects of processing and enzyme addition on growth performance in quails

The results from the growth experiment with quails are presented as weekly averages in Table 3. There were significant effects of processing and enzyme level in the diet on weight gain at weeks 1, 2, 3, 4 and over the total period of the experiment. DHP and AUP of wheat significantly improve WG (P<0.01). Generally, quails that receive AUP wheat had the highest total weight gain (237.6 g), whereas quails fed with untreated wheat had the lowest weight gain (222.7 g). No significant effect of processing methods on feed intake (FI) in all of the weeks was observed. Feed conversion ratio (FCR) at weeks 1, 2, 3, 5 and over the total period of the experiment was affected significantly by processing methods (P<0.01). Overall, quails given diets with AUP wheat had significantly lower FCR during the experiment (3.07 vs. 3.25). Processing significantly increased body weight (BW) in all of the weeks (P<0.01) and quails fed with AUP wheat had the highest body weight (264.0 vs. 249.2 g). Water to feed intake ratio (WFR) was not affected by processing in the whole experiment (P>0.05).

Table 3. Effect of wheat processing and enzyme on quail body weight (BW), weight gain (WG) feed conversion ratio (FCR), feed intake (FI) and water to feed intake ratio (WFR).

	BW(g)					WG (g)						FCR						FI(g)	WFR
	14	21	28	35	42	7–14	14–21	21–28	28–35	35–42	7–42	7–14	14–21	21–28	28–35	35–42	7–42	7–42	7–42
Processing
UT	63.7^b	111.0^b	159.3^b	205.5^b	249.2^c	37.3^b	47.3^b	48.2^b	46.2^b	43.6	222.7^c	2.22^a	2.56^a	2.83^a	3.79	4.78^a	3.25^a	726.1	2.33
DHP	64.5^b	112.2^b	161.6^b	208.1^b	252.8^b	38.1^b	47.6^b	49.4^ab	46.5^b	44.6	226.4^b	2.20^a	2.54^a	2.77^ab	3.74	4.75^a	3.22^a	728.8	2.33
AUP	67.4^a	116.9^b	168.3^a	217.7^a	264.0^a	41.0^a	49.4^a	51.4^a	49.4^a	46.2	237.6^a	2.15^b	2.39^b	2.64^b	3.63	4.49^b	3.07^b	729.9	2.22
Enzyme(g/kg)
0	64.3^b	111.6^b	160.3^b	206.5^b	250.3^c	37.9^b	47.3^b	48.6	46.2^c	43.8	223.8^c	2.23^a	2.57^a	2.82	3.77	4.77^a	3.25^a	727.4	2.35
250	64.7^b	112.7^b	162.4^b	209.6^b	254.4^b	38.3^b	47.9^ab	49.6	47.2^b	44.9	228.8^b	2.18^b	2.50^ab	2.75	3.72	4.65^ab	3.18^ab	724.6	2.30
500	66.6^a	115.8^a	166.6^a	215.4^a	261.3^a	40.2^a	49.2^a	50.7	48.8^a	45.9	234.8^a	2.16^b	2.41^b	2.67	3.68	4.60^b	3.12^b	732.8	2.23
P×E
DHP×0	61.6^d	108.5^e	157.1^c	203.1^cd	246.6^de	35.2^d	46.9	48.5	45.9	43.6	220.2^e	2.21	2.60	2.81	3.77	4.75	3.25	717.2	2.36
DHP×0.25	62.4^d	109.6^ed	158.3^c	204.3^cd	248.8^de	36.0^cd	47.1	48.7	46.0	44.6	222.4^de	2.19	2.58	2.80	3.73	4.75	3.24	721.4	2.35
DHP×0.50	69.6^ab	118.5^cde	169.5^ab	217.1^ab	262.9^ab	43.2^a	48.9	50.9	47.6	45.8	236.5^ab	2.19	2.45	2.70	3.73	4.74	3.16	747.8	2.27
UT×0	61.5^d	108.4^e	157.2^c	202.9^d	246.0^e	35.1^cd	46.6	47.1	45.4	42.8	219.6^e	2.27	2.61	2.90	3.84	4.83	3.30	730.9	2.38
UT×0.25	63.7^cd	112.3^cde	159.6^c	205.0^cd	247.8^de	37.3^bcd	46.8	48.8	45.7	43.2	221.4^de	2.22	2.59	2.85	3.82	4.79	3.28	721.0	2.34
UT×0.50	65.9^bcd	112.5^cde	161.2^bc	208.6^cde	253.7^ab	39.5^bc	48.6	48.8	47.5	45.0	227.2^cd	2.17	2.47	2.75	3.72	4.73	3.19	726.4	2.27
AUP×0	65.5^bcd	113.9^bcd	164.2^abc	211.3^bc	256.3^bc	39.1^bc	48.4	50.3	47.1	44.9	229.8^bc	2.21	2.51	2.75	3.70	4.73	3.19	734.2	2.30
AUP×0.25	70.3^a	120.2^a	171.6^a	221.5^a	268.4^a	43.9^a	49.8	51.4	49.8	46.9	241.9^a	2.12	2.33	2.61	3.61	4.41	3.02	731.5	2.19
AUP×0.50	66.6^abc	116.7^abc	169.1^ab	220.5^a	267.3^a	40.1^ab	50.1	52.4	51.4	46.8	240.9^a	2.12	2.32	2.57	3.58	4.33	3.05	724.2	2.16
p-Value
Processing	<0.01	<0.01	<0.01	<0.01	<0.01	<0.01	<0.01	<0.01	<0.01	ns	<0.01	<0.01	<0.01	0.01	ns	<0.01	<0.01	ns	ns
Enzyme	<0.01	<0.01	<0.01	<0.01	<0.01	<0.01	<0.01	<0.01	<0.01	ns	<0.01	<0.01	0.01	ns	ns	0.02	<0.01	ns	ns
P×E	<0.01	<0.01	<0.01	<0.01	<0.01	<0.01	ns	ns	ns	ns	<0.01	ns	ns	ns	ns	ns	ns	ns	ns
R ^2	0.84	0.87	0.78	0.85	0.92	0.84	0.57	0.45	0.84	0.27	0.92	0.67	0.55	0.41	0.36	0.67	0.66	0.16	0.29
RMSE	1.60	1.89	3.45	3.51	2.95	1.6	1.27	2.38	1.01	2.97	2.95	0.03	0.11	0.14	0.19	0.14	2.69	23.3	0.13
Note: Mean values within a column in each section (processing or enzyme) with no common letters are significantly different (P ≤ 0.05) as determined by least significant difference comparison.
UT, untreated; DHP, dry heat processing; AUP, autoclave processing; P×E, processing×enzyme interactions; RMSE, root mean square error (two-way ANOVA).

Weight gain in weeks 1, 2, 4 and during the overall period of the experiment was significantly affected by enzyme levels in diet (P<0.05). Enzyme addition increased total WG from 223.8 to 234.8 g. However, WG in quails fed with a diet containing 0.25 or 0.5 g/kg enzyme differed significantly (P<0.05). FI was not affected by an enzyme addition to diet. FCR in week 1, 2, 5 and the total period of the experiment were affected by enzyme level in diet and the addition of enzymes to diet decreased FCR significantly (P<0.05), However, FCR in 0.25 and 0.5 g/kg enzyme did not significantly differ. Enzyme addition significantly increased (P<0.05) BW in the whole experiment. Quails fed with a diet containing 0.5 g/kg enzymes had the highest BW. However, BW difference in diet containing 0.25 and 0.5 g/kg was significant. Enzyme levels in the diet did not affect WFR. However, the addition of the enzyme decreased this ratio (2.23 vs. 2.35).

Weigh gain in the first week and the total period of the experiment was significantly affected by the processing×enzyme (P×E) interaction (Table 3). Adding 0.5 g/kg enzyme to UT, DHP and AUP wheat increased WG by 3.4, 7.4 and 4.8%, respectively. The highest and the lowest WG in this period were observed in the group that received AUP wheat with 0.25 g/kg enzymes and untreated wheat without enzyme, respectively. Feed intake was not affected by P×E interaction. Feed conversion ratio was not affected by P×E interaction.

Body weight in the whole experiment was significantly (P<0.05) affected by the P×E interaction. The highest BW in groups that received a diet containing AUP wheat with 0.25 g/kg enzymes and the lowest BW in groups that received untreated wheat without enzyme addition were observed. Adding 0.5 g/kg enzymes to UT, DHP and AUP wheat increased BW 3.1, 6.6 and 4.3%, respectively. WFR was not affected by the P×E interaction. However, BW, WG and FCR of quail fed AUP wheat without enzyme supplementation and UT wheat supplemented with 0.5 g/kg enzymes was not significantly different.

Effects of processing and enzyme addition on carcass parameters

The results from the measured carcass parameters are presented as weekly averages in Table 4. Processing significantly increased male (M) and female (F) quails carcass weight (CW). Highest CW in M and F quails was observed in diet containing AUP wheat, which significantly differs with UT and DHP. In addition, CW was affected by enzyme addition to diet in both sex and with increasing enzyme levels, increased significantly (P<0.05). Breast weight in F and M quails that were fed by AUP wheat was increased up to 10.4 and 5.2%, respectively (P<0.05). Breast weight in diet containing 0.5 g/kg enzymes was higher in both M and F quails. Thigh Weight in F and M quails was affected by processing and the highest thigh weight in quails that were fed with a diet containing AUP wheat was observed. However, thigh weight was significantly higher (P<0.05) in diets containing 500 g/kg enzymes in both F and M quails. Abdominal fat weight with fed AUP wheat in both sexes increased (P<0.05). Also, abdominal fat weight was significantly increased by enzyme addition in M quails (P<0.05). Carcass yield in F and M quails was not affected by processing and enzyme level. Breast and thigh yield in both sexes was not affected by processing. Whereas, breast and thigh yield in F quails were affected by enzyme level. By enzyme levels, breast and thigh percentage increased. Abdominal fat percentage significantly increased in M quails with enzyme addition (P<0.05). Carcass weight and yield in M and F quails was affected by P×E interaction (P<0.05). In each type of wheat, the highest CW was observed in groups that received 0.5 g/kg enzymes. Breast weight and yield were affected in M and F quails by P×E interaction (P<0.05) and quails fed with diets containing UT wheat with 0.5 g/kg enzymes had the highest breast weight. Thigh, back and abdominal fat weight and breast, thigh, back and abdominal fat percentages were not affected by P×E interaction.

Table 4. Effect of wheat processing and enzyme on male and female quail carcass quality.

	Carcass				Breast				Thigh				Abdominal fat
	Weight (g)		Yield (%)		Weight (g)		Yield (%)		Weight (g)		Yield (%)		Weight (g)		Yield (%)
	F	M	F	M	F	M	F	M	F	M	F	M	F	M	F	M
Processing
UT	163.6^c	166.5^b	63.4^b	69.8^ab	67.3^c	74.6^b	41.2	44.8	42.1^b	44.1^b	25.7	26.5	1.68^b	1.05^b	1.03	0.62
DHP	168.8^b	165.9^b	64.4^ab	69.4^b	71.2^b	72.5^c	42.2	43.8	44.9^ab	43.8^b	26.6	26.4	1.72^ab	1.12^ab	1.02	0.67
AUP	178.4^a	177.7^a	65.4^a	71.0^a	74.3^a	78.5^a	41.6	44.3	46.6^a	47.4^a	26.1	26.8	2.24^a	1.36^a	1.25	0.76
Enzyme(g/kg)
0	166.3^c	164.5b	64.4	69.6	68.1^b	73.1^c	40.9^b	44.4	42.7^b	44.7	25.7	27.2	1.68	1.00^b	1.01	0.61^b
0.25	170.3^b	172.2a	64.6	70.9	69.8^b	75.0^b	41.0^b	43.6	44.1^ab	44.5	25.9	25.9	1.85	1.16^ab	1.08	0.66^ab
0.50	174.2^a	173.4a	64.2	69.6	74.9^a	77.6^a	43.0^a	44.8	46.7^a	46.2	26.8	26.6	2.11	1.37^a	1.21	0.79^a
P×E
DHP×0	165.4^c	158.7^e	65.0^ab	68.4^b	68.1^bc	71.0^d	41.2^ab	44.7^ab	42.2^b	42.0	25.5	26.5	1.63	0.93	0.99	0.58
DHP×0.25	166.0^bc	164.9^cde	64.4^ab	69.9^ab	68.2^bc	71.7^cd	41.1^ab	43.5^ab	41.6^b	42.9	25.1	26.0	1.68	1.06	1.01	0.64
DHP×0.50	174.9^ab	174.0^bc	63.7^ab	70.0^ab	77.5^a	75.1^bcd	44.3^a	43.1^ab	50.9^a	46.5	29.1	26.7	1.84	1.37	1.06	0.79
UT×0	162.3^c	163.4^de	63.2^ab	70.2^ab	65.2^c	72.5^cd	40.2^b	44.4^ab	41.6^b	43.2	25.6	26.4	1.62	0.94	0.99	0.57
UT×0.25	164.2^c	164.7^de	64.7^ab	69.6^b	67.4^bc	73.4^cd	41.1^ab	44.5^ab	42.3^b	43.6	25.7	26.4	1.53	0.95	0.94	0.58
UT×0.50	164.5^c	171.3^bcd	62.4^b	69.5^b	69.4^bc	77.9^ab	42.2^ab	45.5^ab	42.4^b	45.6	25.8	26.6	1.90	1.25	1.16	0.73
AUP×0	171.1^bc	171.2^bcd	65.0^ab	70.2^ab	71.1^abc	75.7^abc	41.5^ab	44.2^ab	44.4^ab	48.9	25.9	28.6	1.80	1.14	1.05	0.67
AUP×0.25	180.8^a	187.0^a	64.7^ab	73.4^a	74.1^ab	80.1^a	40.9^ab	42.8^b	48.3^ab	47.1	26.8	25.1	2.33	1.46	1.29	0.77
AUP×0.50	183.3^a	174.8^b	66.5^a	69.5^b	77.9^a	79.8^a	42.5^ab	45.7^a	469^ab	46.3	25.6	26.5	2.58	1.48	1.41	0.84
P-value
Processing	<0.01	<0.01	0.01	0.03	<0.01	<0.01	ns	ns	<0.01	0.01	ns	ns	0.02	0.01	ns	ns
Enzyme	<0.01	<0.01	ns	ns	<0.01	<0.01	<0.01	ns	0.01	0.34	ns	ns	ns	<0.01	ns	0.01
P×E	0.02	<0.01	0.05	0.02	0.05	0.05	0.05	0.03	0.01	ns	ns	ns	ns	ns	ns	ns
R ^2	0.82	0.82	0.43	0.50	0.73	0.79	0.38	0.46	0.59	0.41	0.34	0.28	0.35	0.46	0.22	0.37
RMSE	3.83	4.17	1.47	1.49	2.92	1.86	1.66	2.64	3.05	2.97	1.83	1.53	0.52	0.26	0.31	0.14
Note: Mean values within a column in each section (processing or enzyme) with no common letters are significantly different (P ≤ 0.05) as determined by least significant difference comparison.
UT, untreated; DHP, dry heat processing; AUP, autoclave processing; P×E, processing×enzyme interactions; RMSE, root mean square error (two-way ANOVA).

Discussion

Many advantages are cited in favour of feed processing including increased availability of protein and energy, destruction of anti-nutritive factors and hence an extension to the number of raw materials that can be employed in formulations (Williams et al. 1997). Soluble NSP are considered to either block digestion of other important nutrients, e.g. protein, fat and starch, or inhibit absorptive capacity. Most of the anti-nutritive activities of NSP, which directly affect broiler performance, have been attributed directly to soluble polysaccharides (Rebole et al. 2010). An increased ratio of insoluble to soluble β-glucans and NSP may be favourable to chicken performance, as the negative effects of β-glucans are mainly associated with the soluble fraction (Skrede et al. 2003). This was confirmed in the present study, ratio of insoluble to soluble β-glucans and NSP in all treatment compared with untreated wheat increased and this ratio may be indicating that reduced β-glucans solubility due to processing may have contributed to improved quail performance. We have no explanation to increased level of dietary NSP and β-glucans in the wheat after DHP and AUP, except that processing may have increased the availability of β-glucans to analytical enzymes. Autoclaving caused starch gelatinisation, shown by increased levels of damaged starch and hydration capacity in barley (Skrede et al. 2001). Simultaneously there was a comparable increase in the levels of total dietary fibre, indicating that autoclaving may have caused formation of resistant starch in barley (Berry 1986).

The present study showed beneficial effects of feeding autoclaved wheat on BW, WG and FCR in Quails. Improved performance of quail by feeding autoclaved wheat in current experiment could be attributed to improved nutrient digestibility and AME. The result of the current experiment is in agreement with Afsharmanesh et al. (2008) who reported that heat treatment (oven dried at 80°C for 15 h) significantly improved FCR and AME, protein and P digestibility and destroyed endogenous phytase and xylanase in wheat-based diets, also increasing the levels of soluble NSP. Steam HP of cereal may modify the physical and chemical structure of the cereal, improving accessibility of enzymes to dietary components and facilitating its utilisation (Gracia et al. 2008). Zaghari (2006) reported that autoclaving of wheat increased its amino-acid digestibility. Nir et al. (1993) found that starch in corn after steam processing had a 4.5-fold higher in vitro digestion by amylase than that in unprocessed corn. Teitge et al. (1991) reported that autoclaving of rye can gelatinise starch and increase the solubility of NSP, resulted in an increased chick growth response to dietary enzyme while producing little or no effect without enzyme. However, in the current experiment, AUP without enzymes had improved growth performance but the effect of AUP increased with enzyme addition.

DHP in the current experiment had little effect on growth performance of quail and enzyme supplementing DHP wheat compared with UT wheat, which had little beneficial effect. This result agrees with Gonzalez-Alvarado et al. (2008) who reported that DHP (45 min at 90°C) did not affect broiler performance from 1 to 21 days old and, if anything, it impaired BWG and F:G from 1 to 4 days old. Herstad and McNab (1975) and Vukic Vranjes and Wenk (1995) concluded that DHP of barley did not have any effect on performance of broilers. In contrast, Afsharmanesh et al. (2008) reported that DHP treatment of wheat (oven dried at 80°C for 15 h) significantly improved FCR and AME, protein, and P digestibility in the broiler. The reasons for the discrepancies amongst authors are unknown but might be related, at least in part, to differences in the conditions applied during the thermal process and to the type of cereal used. For example, Niu et al. (2003) indicated that broiler productivity was improved when wheat was micronised at 90 or 105°C. However, when the temperature was above 120°C, productivity was reduced. Gonzalez-Alvarado et al. (2007) observed that HP (for 60 min at 104°C) increased the total tract retention of nutrients in the corn diet but decreased it in the rice diet suggesting that the impact of DHP on digestibility is dependent on the type of cereal used.

By autoclaving the wheat and adding enzyme to the diet, abdominal fat increased. Abdominal fat constitutes a large discrete fat depot in broiler chickens and is highly correlated to total carcass lipids (Larbier and Uzu 1991). Higher fat deposition can increase the energy expenses associated with growth in the finishing period, and may have concealed effects of autoclaving on nutrient digestibility. With increasing BW due to processing or enzyme addition eviscerated carcass, breast and thigh weight increased. This indicates that the amount of carcass parts, which are edible, has now increased.

Enzymes improve WG and FCR of quails. This may be due to the increasing nutritive value of cereals with high levels of soluble NSP by the use of feed enzymes. Enzymes need only cleave at a few places in the polysaccharide chain to greatly reduce the viscosity of solutions and thus enhance nutritive value (Williams et al. 1997). Several studies have shown that the addition of β-glucanase to chicken diets may degrade endosperm cell walls, resulting in increased digestibility of nutrients which otherwise may be encapsulated in the cell structures (Hesselman and Aman 1986; Bergh et al. 1999). The improvement of chicken performance on diets supplemented with enzymes are caused by the breakdown of the fibre components into smaller polymers (de Silva et al. 1983), rather than complete hydrolysis of the polysaccharides and absorption of released sugars (White et al. 1983; Campbell et al. 1989). The beneficial effect of the use of exogenous enzymes in the present study on FCR was observed only in quail that received a diet containing untreated wheat. This indicates that processing can improve nutrient digestibility without the addition of enzymes to the diet.

In conclusion, autoclaving can be used to improve growth rate and FCR of growing quail that are fed diets based on wheat in spite of enzyme supplementation. However, enzyme addition to autoclaved wheat increases the beneficial effects.

Additional information

Notes on contributors

Ruhollah Kianfar

Current Address: Ruhollah Kianfar, Department of Animal Science, Faculty of Agriculture and Natural Resources, University of Tehran, Karaj, Iran