The efficient use of feed is extremely important in broiler production. Investigations have to be continued to decrease cost of broiler production and improve broiler performance. Pellet feed has been shown to have the greatest potential to improve feed conversion ratio (FCR) and reduce cost compared to mash feed (Maiorka et al. 2005, Salari et al. 2006, Amerah et al. 2008). These improvements have been associated with changes in nutrients, digestibility and less feed wastage (Amerah et al. 2007).
Sundu et al. (2009) reported that birds tended to prefer larger pellet sizes, while the fine pellet sized diets (more than 50% <2.0mm) were not attractive to the birds at any age and they become less attractive as the birds got older; the larger pellet sizes of the mixed diet increased body weight and feed intake significantly. Tufarelli et al. (2011) reported that live body weight, feed intake and feed conversion ratio (FCR) were greater in guinea fowls and pheasants fed 2mm pellet diet than those of them fed 4mm pellet diet. The best FCR observed in birds fed processed feeds compared to birds given mash feed, may be accounted for an increased available net energy because less activity is used for eating.
Energy utilization in corn-soybean meal and sorghum-soybean meal diets could be improved by an enzyme cocktail contains amylase, xylanase and protease to promote the breakdown of starch, cell walls and endogenous proteins, respectively (Hong et al. 2002). Several studies have found that optimizing phosphorus intake and digestion with phytase reduce the release of phosphorus in manure by around 30% (Attia et al. 2006). Also, Wu et al. (2006) reported that phytase supplementation to diets containing 0.11% non-phytate phosphorus significantly reduced excreta phosphorus with no adverse effect on performance. The use of phytase not only releases the bound phosphorus but also other essential nutrients (proteins, starch, calcium, magnesium, iron and zinc) which led to higher nutritional value of the diet (Ceylan et al. 2003, Panda et al. 2005, Jiang et al. 2013). Attia et al. (2008) observed that the addition of multi-enzyme to the diet improved the economic efficiency of chicken’s diets. However, improved performance of poultry depends on dietary composition and type of enzyme (Attia 2003, Abudabos 2012, Nourmohammadi et al. 2012).
The use of an enzyme complex containing carbohydrases and phytase should allow the improvement of energy, protein, P and Ca utilization by broilers, laying hens, ducks and Japanese quails (Attia 2003, Attia et al. 2003a, 2003b, El-Ghamry et al. 2005, Attia et al. 2008, Yang et al. 2010) and thus it would be possible to add a low dose of these nutrients to the diet. This study aimed to investigate the effect of phytase with or without multi-enzyme supplementation on performance, nutrient digestibility and economic traits of broilers fed mash or pellet diets with different diameter (2-2, 2-3 and 3-3.5mm) during 21-37 days (d) of age.
Material and methods
A total of 420, 21-day-old unsexed Arbor Acres broiler chicks were distributed keeping equal initial body weight in 60 cages (7 birds per cage). The trial was listed from 21 to 37 d of age and along this period the birds fed two kinds of diet: grower (from 21 to 29 d) and finisher (from 30 to 37 d). The groups were submitted to the following dietary treatments: mash group (fed mash diets); 2-2mm pellet group (fed pellet diets with 2mm diameter in both 21-29 and 30-37 d periods); 2-3mm pellet group (fed pellet diets with 2 and 3mm diameter, respectively during grower and finisher periods); 3-3.5mm group pellet (fed pellet diets with 3 and 3.5mm of diameter, respectively during grower and finisher periods). Each group was divided into 3 subgroups (5 cages and 35 chicks/subgroup) whose diets were, respectively, unsupplemented (control subgroups), supplemented with phytase (phytase subgroups, Phyzyme XP at 0.07g/kg diet) and supplemented with multi-enzyme plus phytase (multi+phytase subgroups, Avizyme 1505 at 0.2g/kg diet plus Phyzyme XP at 0.07g/kg diet). Pelleting temperature did not exceed 80 °C. Phyzyme and Avizyme are products of Danisco Animal Nutrition (Marlborough, Wiltshire, UK). Avizyme 1505 is a multi-enzyme containing 1 500U/g endo-1, 4-β-xylanase, 2 000U/g α-amylase and 20 000U/g subtilisin. Phyzyme XP is an Escherichia coli phytase classified as a 6-phytase with hydrolysis of the phosphate moiety being initiated at the 6-position on the phytate molecule.
The feeding system and husbandry practice during 1-20 d of age are presented by Attia et al. (2012).
The available phosphorous (avP) and Ca contents were adjusted in the diets supplemented with phytase according to phytase equivalent values (Attia 2003, Attia et al. 2003a, Choct 2006). The experimental diets were formulated according to NRC (1994). Ingredients and chemical composition of the experimental basal diets fed during the grower and finisher stages are shown in Table 1.
Housing and husbandry
Broilers were housed in battery brooders in semi-opened house. They were fed ad libitum the experimental diets and given free access to water. A light schedule was 20 h light during 21st to 34th day of age followed by 24h of light until slaughter. The average outdoor minimum and maximum temperature and relative humidity during the experimental period were 21.2 and 24.2 °C and 56.7 and 58.7%, respectively. The housing temperature was 24 °C at 21d of age, declined gradually to 21 °C at 28d of age and then was around 21 °C until slaughter. Broilers were vaccinated against the most common diseases such as Newcastle disease, avian influenza, infectious bursa disease and infectious bronchitis.
Birds were weighed individually at 21, 29 and 37 d of age and body weight gain (BWG) was calculated. Feed intake was recorded for each replicate and was used to calculate FCR (g feed/g gain) during 21-29, 30-37 and 21-37 d of age. The survival rate (100 – mortality rate) was also recorded along the trial.
Apparent digestibility of dry matter (DM), crude protein (CP), ether extract (EE), crude fibre (CF) and crude ash (CA) was measured on finisher diets on three replicates of three males per treatment using the total collection method as described by Attia et al. (2003a). Dry matter, CP, EE, CF and CA contents of the excreta, as well as those of feed, were determined according to AOAC (2004).
European Production Efficiency Index (EPEI) was calculated using Hubbard Broiler Management Guide (1999) equation as follows:
where BW is the body weight in kg, SR is the survival rate, PP is the production period in days and FCR is the feed conversion rate.
Economical evaluation for all experimental diets was made as described by Attia et al. (2014).
Statistical analysis was carried out using the GLM procedure of Statistical Analysis Software 2002 (SAS Institute Inc., Cary, NC, USA) using a two-way factorial design (4 types of feed with 3 different enzyme treatments); the experimental model also included the interaction between the main factors. All percentages were transformed to their corresponding arcsin value before run the analyses. Mean difference at P≤0.05 was tested using Student-NewmanKeuls-test. Survival rate was analysed as percent using chi-square analyses.
Body weight gain
The effects on growth of broilers because of diet and/or enzyme supplementation are shown in Table 2. Body weight gain in broilers fed pellet diets was higher (P<0.01) from 21-29 and 21-37 days than that of those fed mash diet. However, there were no significant differences in BWG during 21 to 29 d of age among groups fed different diameter of pellets. Broilers fed 2-3mm pellet diameter had a significantly higher BWG during d 30 to 37 and 21 to 37 d of age than those fed mash or 2-2mm and 3-3.5mm pellet diets.
Control group resulted in significantly lower BWG in the period 21-29, 30-37 and 21-37 d of age, while multi-enzyme+phytase supplementation resulted in a significantly higher BWG in the period 30-37 and 21-37 d of age than the phytase group.
A significant interaction between diet form and enzyme supplementation was shown only on BWG during 30-37 d of age. In broilers fed mash diets the BWG did not change when phytase or multi-enzyme+phytase were supplemented while with pellet diets BWG increased (P<0.01) when multi-enzyme+phytase (2-2mm diets) or both phytase and multienzyme+phytase (2-3 and 3-3.5mm diets) were added.
Feed intake and feed conversion ratio
Data concerning feed intake (FI) and FCR of broilers affected by form of diet and/or enzyme supplementations are shown in Table 3. Feed intake was significantly decreased in broilers fed the pellet-feeds compared with those fed the mash feed during the experimental period. There was neither a significant effect of enzyme supplementation on FI during the tested periods, nor a significant interaction between form of diet and enzyme supplementation on FI during the tested periods.
Feed conversion ratio was significantly lower in broilers fed pellet diets than that of those fed mash diet and in the period 30-37 d of age birds fed 2-3mm diets had the lowest FCR. During days 21 to 37 broilers fed 2-3mm and 3-3.5mm pellet diets had significantly lower FCR than those fed mash or 2-2mm diets.
Both phytase and multi-enzyme+phytase significantly improved FCR compared to the unsupplemented control from day 21 of age. However, FCR of broilers fed multi-enzyme plus phytase diet was significantly lower than that of those fed phytase alone during 30-37 and 21-37d of age.
A significant interaction between form of diet and enzyme supplementations was shown for FCR during only 30-37d of age with a different trend among the type of diets. In broilers fed mash diets FCR was similarly improved (P=0.05) due to the supplementation of phytase or multi-enzyme+phytase; with 2-2mm pellet diets, only multi-enzyme+phytase was able to improve FCR in comparison to the control group; broilers fed 3-3.5mm pellet diets had better FCR when both phytase and multi-enzyme+phytase were administered and no differences were observed between the FCR obtained with the two types of enzymes; just with 2-3mm pellet diets there is a progressive improvement of FCR from control, phytase and multienzyme+phytase groups.
Apparent digestibility of nutrients
Data concerning the effects of the diet form and enzyme supplementation on apparent digestibility of nutrients of broilers are shown in Table 4.
Pellet diets resulted in a significantly higher CP, EE, CF and CA digestibility than mash diet, but did not affect DM digestibility. However, there were no significant differences on the apparent nutrient digestibility among groups fed different pellet diameters.
Groups fed diets supplemented with either phytase or multi-enzyme plus phytase showed significantly and similarly greater CP, EE and CA digestibility than the control group. There was no significant interaction between feed form and enzyme supplementation in the apparent digestibility of nutrients.
Survival rate, production index and economic efficiency
During the trial, no deaths were observed. The data concerning production index and economic efficiency are presented in Table 5. The production index was the highest in broilers fed 2-3mm pellet diets, followed by 3-3.5mm, 2-2mm pellet and mash diets. The economic efficiency was higher (P<0.01) in 2-3 than 2-2mm and mash diets while no differences were observed between 2-3 and 3-3.5mm diets; however mash diets had the lowest economic efficiency. Either phytase alone or multi-enzyme+phytase showed a significantly higher production index and economic efficiency than the control group. However, broilers fed multi-enzyme plus phytase had a significantly higher production index and an economic efficiency than those supplemented with phytase alone. There was no significant interaction between feed form and enzyme supplementation on production index and economic efficiency.
Feeding pellet diets with 2-2, 2-3 and 3-3.5mm diameter increased BWG (6.4, 14.2 and 10.1%, respectively), decreased feed intake (8.5, 9.3 and 9.8%) and then improved FCR (14.9, 21.3 and 19.0%) compared to broilers fed mash diets. This coincided with a higher digestibility of CP (15.3, 17.3 and 17.6%), EE (22.2, 20.1 and 20.1%), CF (34.7, 32.2 and 33.9%) and CA (15.7, 14.4 and 15.1%) and resulted in a greater production index (28.9, 46.0 and 37.4%) and economic efficiency (43.1, 62.6 and 52.9%). These results are similar to those reported by Cerrate et al. (2009), Sundu et al. (2009), Tufarelli et al. (2011) and Corzo et al. (2012). These improvements have variously attributed to the size of pellet, whose particles with a dimension suitable for the oral cavity of the bird, allowed a reduction in the energy for eating and consequently a greater net energy (NE) value (Tufarelli et al. 2007, Latshaw 2008, Cerrate et al. 2008, 2009, Dozier et al. 2010). In addition, in many studies, it was observed that pellet diets improve FCR compared to mash feed. These improvements have been associated with greater digestibility of nutrients and less feed wastage and microbial load (Kilburn & Edwards 2001, Engberg et al. 2002, Maiorka et al. 2005, Salari et al. 2006, Amerah et al. 2007, Attia et al. 2012). The nutritive value of pellet diets may be improved as a result of increasing starch gelatinization in the pellet process (Heffner & Pfost 1973, Moritz et al. 2005).
Phytase and multi-enzyme plus phytase supplementation increased BWG (8.3 and 12.7%), decreased feed intake (0.6 and 2.3%) and improved FCR (7.4 and 12.7%) compared to broilers fed diet without enzyme supplementation. The positive effect of enzymes on growth performance of broilers was observed along with increasing nutrient digestibility of CP (5.8 and 8.3%), EE (4.6 and 8.0%) and CA (15.6 and 17.4%); production index (15.9 and 26.1%) and economic efficiency (19.6 and 31.5%). These results are in agreement with those reported by Douglas et al. (2000), Persia et al. (2002) and Attia et al. (2003a, b, 2008). Multienzyme containing amylase, xylanase and protease was found to improve energy utilization in corn-soybean meal and sorghum-soybean meal diets due to the breakdown of starch, cereal cell walls and endogenous proteins (Hong et al. 2002, Attia et al. 2003a, El-Ghamry et al. 2005, Attia et al. 2008).
The improvements due to phytase supplementation could have attributed to the capability of phytate to form complexes with proteins and inorganic mineral such as calcium, magnesium, iron and zinc. Thus phytase not only releases the bound phosphorus but also the other essential nutrients which led to higher nutritional value of the diet (Keshavarz 2003, Ceylan et al. 2003, Panda et al. 2005).
The greater effect of both enzymes, when added together, indicated a synergetic effect and this is in agreement with the results of Cowieson et al. (2006) and Yang et al. (2010). The use of an enzyme complex containing carbohydrases and phytase can improve the utilization of phytate P, energy, protein, and Ca concentrations. However, the results reported by Attia et al. (2003a and 2008) indicated that phytase or multi-enzyme alone may be adequate. The response to enzyme supplementations may be affected by type of diet, age of birds and enzyme profiles (Zanella et al. 1999, Attia 2003, Attia et al. 2003a, b, 2006, 2008).
The form of feed and/or two enzymes had no significant effect on survival rate; this is similar to reports by Deaton (1992) and Dozier et al. (2010). Also, Cerrate et al. (2009) and Tufarelli et al. (2011) reported that the physical form of diet had no influence on the health status of poultry.
The beneficial effects of pellet feed and/or enzyme supplementation on production index and economic efficiency are in line with those reported by Jahan et al. (2006). Also, Fairfield (2003) noticed that pelleting of feed provides opportunities to reduce feed formula costs.
However, the lack of significant interaction between feed form and enzyme supplementations on performance and nutrient digestibility for the whole period indicated that the effects of multi-enzyme plus phytase or phytase alone supplemented to mash or pellet diets are independent of feed type.
In conclusion, phytase and multi-enzyme plus phytase supplementation resulted in an improved performance of broilers fed mash or pellet diet. However, broilers fed 2-3mm pellet diet supplemented with multi-enzyme plus phytase resulted in the greatest productive performance, production index and economic efficiency during days 21-37 of age.
This article was originally published in Archiv Tierzucht 57 (2014) 34, 1-11 Received: 28 May 2014. doi: 10.7482/0003-9438-57-034. This is an Open Access article distributed under the terms and conditions of the Creative Commons Attribution 3.0 License (http://creativecommons.org/licenses/by/3.0/).