Abstract
A 4 × 3 factorial experiment was designed to study the effects of a multi-enzyme (Avizyme 1502; combination of xylanase, α-amylase and protease) in three levels (0, 250, 500 mg/kg) on performance and carcass characteristics of broiler chickens fed corn-soybean meal diets with different levels of metabolizable energy (ME; 13.18; 12.34; 11.93 and 11.51 MJ/kg) from 1 to 49 days of age. Results showed that dietary treatments had no significant effect (P > 0.05) on feed intake at 10 days and 24 days but birds fed diets containing 13.18 MJ/kg ME with 500 mg/kg multi-enzyme consumed more feed than birds fed diets with 11.51 MJ/kg ME and 250 mg/kg multi-enzyme (P < 0.05) at 49 days. Average daily gain in starter (1–10 days) and finisher (25–49 days) periods was affected by interaction between ME and enzyme. No significant differences (P > 0.05) were observed for feed conversion ratio (FCR) in grower period, although dietary treatments affected FCR in starter and finisher phases. At 49 days of age, the best FCR obtained for birds fed diets containing 13.18 MJ/kg ME and 250 mg/kg multi-enzyme. The highest FCR was for birds fed a diet with 11.51 MJ/kg ME with 250 mg/kg multi-enzyme. Breast, thigh and liver were significantly affected by dietary treatments. A diet with 13.18 MJ/kg ME and 500 mg/kg multi-enzyme resulted in the highest breast and thigh yield (P < 0.05). It can be concluded that adding enzymes to corn-soy based diets allowed the reduction in the energy level of broiler diets without any negative effects on performance of broiler chickens.
1. Introduction
Enzyme supplementation as a feed additive has become common since last four decades (Jensen et al. Citation1957; Chesson Citation1993). Advances in enzyme biotechnology and knowledge of substrates have led to the development of non-starch polysaccharide (NSP) degrading enzymes, such as glucanase and xylanase, which are capable of improving metabolizable energy (ME) of viscous grains, such as wheat and barley. Numerous studies of exogenous enzyme supplementation in broiler diets have been conducted, and improvements of the performance of broiler chicks and nutrient availability have been well documented. Addition of enzymes to diets can help to eliminate the effects of anti-nutritional factors and improve the utilization of dietary energy and amino acids, resulting in improved performance of chickens (Rotter et al. Citation1990; Cowan et al. Citation1996; Yu et al. Citation2007; Zhou et al. Citation2009). Since corn and soybean meal are the main parts of poultry diets, the energy utilization in corn and soybean meal also depends on the amount of indigestible carbohydrates present in particular oligosaccharides and NSP. The ME level of diet is one of the key factors for rapid growth of broiler chickens. Addition of enzymes to diets for improving energy availability has received much attention by animal nutritionists and feed manufacturers.
Previously, researchers have mostly focused on the energy improvement of barley, wheat, rye and oats-based diets supplemented with NSP degrading enzymes while corn-soy diets with different ME levels have received less attention. Therefore, the aim of this study was to evaluate the efficiency of energy improvement in corn-soy based diets with different ME levels by addition of different levels of a multi-enzyme (Avizyme 1502).
2. Materials and methods
2.1. Diets and enzymes
The experimental diets were formulated with four levels of ME (11.51, 11.93, 12.34, 13.18 MJ/kg) and three enzyme inclusion rates (0, 250 and 500 mg/kg). Composition of starter (1–10 days), grower (11–24 days) and finisher (24–49 days) diets is shown in , and , respectively. The enzyme used was a commercial multi-enzyme complex (Avizyme 1502) which provided 300, 2500 and 2000 units of xylanase, α-amylase and protease per kg, respectively.
Table 1. Composition of experimental diets for starter phase.
Table 2. Composition of experimental diets for grower phase.
Table 3. Composition of experimental diets for finisher phase.
2.2. Birds
Five hundred and seventy six day-old Ross 308 broilers were obtained from a commercial hatchery. Chicks weighed individually and distributed randomly to 12 experimental diets with 4 replicates of 12 chicks each. The birds were housed in deep litter pens and reared based on the standard management guidelines (Ross 308). The brooding temperature was kept at 35°C during the first day and gradually lowered by 3°C till fifth week. Parameters measured at the end of each phase were feed intake (FI), feed conversion ratio (FCR) and average daily gain (ADG). Mortality was recorded daily and any died bird was weighed and used for adjusted FI and FCR. The Institution’s Ethics and Animal Welfare Commission approved all procedures.
2.3. Carcass analysis
At the end of experiment, all birds fasted for 8 h prior to slaughter, then three birds from each replicate were randomly selected, weighed and slaughtered to obtain breast, thigh, liver, gizzard, spleen, heart, bursa of fabricius, pancreatic and abdominal fat (all as g).
2.4. Statistical analysis
The study was conducted in a 4 × 3 factorial arrangement with four levels of ME and three levels of multi-enzyme. Data obtained were analyzed using GLM procedure of SAS 9.1 (SAS Institute Citation1991). The cage was the experimental unit, and least squares means were compared using orthogonal contrasts. Differences were considered significant at P < 0.05.
3. Results
The effects of investigated dietary treatments on FI, BW and FCR at 10, 24 and 49 days of age are summarized in . Results showed that the ME and enzyme main effects and their interaction had no significant effect on FI of broilers at 10 days and 24 days. Although, no effect of enzyme or its interaction with ME could be detected in 49 days, but the ME main effect significantly affected the FI of birds in this period (P < 0.01). In the finisher phase (49 days), birds fed diets containing 13.18 MJ/kg ME and 500 mg/kg multi-enzyme showed the highest FI (=121.4 g/bird per day) while the lowest FI (=105.2 g/bird per day) was observed for the group of birds fed diets with 11.51 MJ/kg ME and 250 mg/kg multi-enzyme. Although ADG was not significantly affected by the ME and enzyme main effects or their interaction in 24 days, but ME main effect and its interaction with enzyme level both affected ADG in both 10 days and 49 days. Based on the results obtained here, minimum ADG (=42.96 g/birds per day) at 49 days was achieved with birds consumed a diet containing 11.51 MJ/kg ME and 250 mg/kg of diet enzyme addition. At this phase (49 days) maximum ADG (=63.91 g/birds per day) was for those birds which were allocated to a diet with 13.18 MJ/kg ME supplemented with 250 mg/kg of diet multi-enzyme. Based on , birds during grower phase (24 days) showed no significant response (in terms of FCR) to the dietary treatments while birds in starter and finisher periods were significantly affected by the interaction between ME and enzyme (P < 0.05). In this case, during the starter period minimum (=1.13) and maximum (=1.46) values for FCR was for those birds consumed diets both with 11.93 MJ/kg ME but supplemented with 500 and 0 mg/kg of diet multi-enzyme, respectively.
Table 4. Effects of dietary treatments on FI, ADG and FCR of broilers in 10, 24 and 49 days of age.
For the finisher period the lowest, and therefore, the best FCR (=1.78) was achieved with a diet containing 13.18 MJ/kg ME supplemented with 250 mg/kg of diet multi-enzyme.
The effects of dietary treatments on carcass characteristics are presented in . Analysis of carcass characteristics data showed that only breast, thigh and liver were affected by (P < 0.05) the dietary treatments investigated here ().
Table 5. Effects of dietary treatments on live body weight and carcass composition (g) of broilers in 49 days of age.
The maximum breast weight (695.4 g) was achieved with birds fed a diet containing 13.18 MJ/kg ME and 500 mg multi-enzyme per kg of diet. As shows, the maximum thigh (=608.7 g) and liver (=73.1 g) weight were belonged to the same dietary treatment which caused the maximum breast weight. The other part of carcass that might of interest for nutritionists and producers is abdominal fat. However, in this study dietary treatments were unable to significantly affect this part (P > 0.05).
4. Discussion
As corn and soybean dominate the feed market for both poultry and pigs, there is considerable interest in identifying situations in which enzyme addition to feeds based on these ingredients might be profitable. To date, little indication of success exists regarding the development of enzyme preparations specific to corn-soy diets.
Huisman et al. (Citation2000), in an in vitro experiment, showed that corn contains highly branched glucuronoarabinoxylans, which can be degraded by exogenous enzymes into a series of oligomers. These oligomers have high water-holding capacity capable of causing an increase in viscosity. In another experiment, Knudsen (Citation1997) reported that corn has up to 0.9% and 6% soluble and insoluble NSP, respectively, while soy bean meal contains up to 6% soluble and 16–18% insoluble NSP.
Noy and Sklan (Citation1995) reported that digestibility of cornstarch at the terminal ileum could be as low as 85% and did not seem to increase with age of the chicken. The starch that escapes digestion in the small intestine is known as resistant starch (Brown Citation1996) which may potentially present an opportunity for exogenous an amylase supplementation. Since cereal grains like corn contain long-chain carbohydrate molecules, cellulose and NSPs, which are mainly found in the cell wall and are bound together in a complex matrix, adding exogenous NSP degrading enzymes to feeds may unlock the encapsulated starch molecules by solubilizing the cell wall structure and increasing accessibility to digestive enzymes, thus further enhancing nutrient availability for growth. These enzymes in corn-soy based diets, in some cases, were able to compensate for the 3% reduction in dietary ME content, without compromising feed (Yu & Chung Citation2004). In present study, in starter and finisher periods, interaction between ME and enzyme improved productive performance (FI and FCR) of birds. In agreement with these results, previous studies reported a significantly positive growth performance response in corn-based diets supplemented with enzymes, either multi-enzymes which contains xylanase, protease and amylase or a single protease enzyme (Zanella et al. Citation1999; Zhou et al. Citation2009).
On the other hand, some researchers believe that when the constituent NSP in corn and soy bean meal is analyzed, it becomes clear that an extensive blend of carbohydrases must be supplemented if any performance response is to be achieved. These researchers further stated this is likely why minimal performance improvements have been reported in corn-soy poultry diets supplemented solely with xylanase and β-glucanase or a combination of xylanase, amylase and protease (Slominski Citation2011). In current study, no significant differences were observed for FCR in grower period, but in starter and finisher period FCR was affected by these treatments. However, in 49 days the best FCR was obtained for birds fed diets with 13.18 MJ/kg ME and supplemented with 250 mg/kg multi-enzyme. The highest FCR was obtained for a diet with 11.51 MJ/kg ME and 250 mg/kg multi-enzyme.
Troche et al. (Citation2007) conducted an experiment to evaluate the effects of Avizyme 1502 on Turkey Tom poults fed corn-soy-wheat diets. They reported that, in most instances, production response differences between the dietary treatments were not significant, making definitive interpretation of enzyme addition difficult (Troche et al. Citation2007).
Zanella et al. (Citation1999) fed a low-energy diet supplemented with 1000 mg multiple enzyme/kg fed to chickens and reported the improved in nutrient digestibility. Kocher et al. (Citation2003), using an enzyme cocktail containing pectinase, protease and amylase, found that this enzyme cocktail was able to improve the ME available from a low-energy corn-soy-based diet but they could not prove this effect in high-energy diets.
In the current study, breast, thigh and total body weight were affected by the dietary treatments. Through the results achieved here, it seemed that a dietary treatment with 13.18 MJ/kg ME supplemented with 500 mg/kg multi-enzyme had a higher breast, thigh and total body meat yield. These results are in contrast with those reported by Café et al. (Citation2002). In their experiment addition of 1000 mg multi-enzyme per kg of diet (Avizyme 1500) to a corn-soy-based diet had no significant effect on breast, thigh and wing components (Café et al. Citation2002).
Excessive fat is one of the main problems faced the broiler industry these days, since not only reduces carcass yield and feed efficiency but also causes rejection of the rest by consumers and causes difficulties in processing. In this study, however, abdominal fat was not affected significantly by interaction between ME and enzyme (P > 0.05). In contrast to these results, Café et al. (Citation2002) reported that birds fed the diets supplemented with Avizyme had a significantly (P ≤ 0.03) higher proportion of abdominal fat at 42 days and 49 days. Although, results from some previous studies showed that carcass yields and internal organs were not affected due to addition of enzyme to diets of broiler chickens (Biswas et al. Citation1999; Kidd et al. Citation2001; Hassan et al. Citation2011).
Based on the results of this study, it can be concluded that adding enzymes to corn-soy-based diets allowed the reduction in the energy level of broiler diets without any negative effects on the performance of broiler chickens.
Related Research Data
References
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