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XXII Congresso Latino-Americano de Avicultura 2011
The following technical article is related to the event::
XXII Congresso Latino-Americano de Avicultura 2011

Effects of a mono-component protease in broiler diets with increasing levels of trypsin inhibitors

Published on: 10/20/2011
Author/s : ME Mayorga1*, SL Vieira1, JOB Sorbara2 - 1Universidad Federal de Rio Grande do Sul, Departamento de Zootecnia, Porto Alegre, RS, Brazil; 2DSM Nutritional Products, São Paulo, SP, Brazil
Summary

Thermal processing, especially moist heating, and enzyme supplementation are two of best known methods for improving the nutritional quality of the oilseeds used in poultry nutrition. These methods inactivate proteinaceous anti-nutritional factors and can also help to offset the effects of the anti-nutritional factors found in soybeans. This experiment was conducted aiming to assess the addition of a mono-component protease in diets containing soybean subjected to various heat treatment periods. Whole raw soybeans were autoclaved for 0, 105, 115 or 135 min (120 ºC and 1.5 atm.) then used in the manufacturing of the experimental feeds at a 20% inclusion level. Two enzyme supplementation levels were tested: 0 and 200 ppm. These feeds were given to 400 Cobb male broilers from d 1 to d 28 of age. Body weight gain, feed intake, feed efficiency, carcass yield, and the pancreas weight/duodenum weight-to-body weight rations (i.e., relative organ weights) were recorded. Results showed that the protease-supplemented birds had better performance results, better carcass yield, and lower levels of abdominal fat deposition. No interaction was observed between protease level and urease index. Animal performance and carcass yield were influenced as urease levels increased. Increasing urease levels resulted in increased relative pancreas and duodenum weights, but the dietary supplementation with 200 ppm mono-component protease level the size of these organs was reduced regardless of unease levels.
Key Words: Broilers, Heat treatment, Mono-component protease, Organ size, Urease.

Introduction
In nature, soybeans posses a series of secondary metabolites known as anti-nutritional factors. These compounds have rious effects on bird growth, feed efficiency, and nutrient digestibility, particularly protein digestibility. Anti-nutritional factors found most frequently in soybeans are condensed tannins, lectins, amylase inhibitors, phytate, alkaloids, saponin and, mainly, protease inhibitors, particularly Kunitz's and Bowman-Birk's factors (Hamza and Abu-Tarboush, 1998; Trugo et al., 2000; Oliva and Sampaio, 2009). This inhibitors are proteins and, as such, they are denaturalized when exposed to heat (Drew et al., 2007) during soy processing to produce roasted beans or soybean meal. The presence of these factors in soy is typically detected by the rapid urease test, which result is higher as these factors are less and less denatured (Ruiz et al., 2004). In poorly heat-treated soy products, such factors result in depressed animal growth due to inhibition of the action of pancreatic trypsin and chymotrypsin, causing pancreas hypertrophy (Carvalho et al., 2002). The addition of protease improves protein digestibility and it can complement the action of endogenous enzymes (Wiryawan and Dingle, 1999). This experiment was undertaken as an attempt to evaluate the supplementation of a mono-component protease in feeds based on soy subjected to different heat treatment times.
Materials and Methods
The experiment was carried in the metabolic room, Teaching and Research Aviary, Federal University of Rio Grande do Sul, Brazil. Four hundred (400) one-day-old Cobb male broilers were used (8 treatments x 5 repetitions x 10 birds per cage). On day one, the birds were weighed so that birds in each cage had similar weights. Sexing errors were culled at arrival. The birds were housed in metabolic cages (0.80 x 0.90 m2) and maintained under artificial lighting for 24 hours per day throughout the experimental period. On day one, the temperature was maintained at 32ºC to ben decreased at the rate of 0.5ºC per day, down to 22ºC, then remaining at this temperature until experiment completion. Baby-type drinkers and feeders were used from 1 to 14 days, then replaced to trough-type drinkers and feeders, from 15 to 28 days. Water and feed were offered ad libitum throughout the experimental period. Heat treatment (autoclave) was applied to soy in natura for 0, 105, 110 or 135 minutes (120ºC, 1.5 atmospheres), respectively, and urease activity was determined in duplicate (Table 1). Basal diets were prepared using all four autoclaved soy types, at the inclusion level of 20%, with two different enzyme supplementation levels (0 and 200 ppm). The feeds were formulated observing typical Brazilian standards, and offered in a mash form (Table 2). The overall health status and bird mortality were recorded daily, as well as maximum/minimum temperatures. Animal performance parameters (weight gain [WG], feed conversion rate [FCR] and feed intake [FI]) were recorded weekly. At 28 days of age, 320 birds (eight per cage) were selected and individually identified. These birds were euthanized in order to determine carcass yield and abdominal fat contents. In addition, pancreas and duodenum weights were also recorded. The experimental design was completely at random, with a 2 x 4 factorial arrangement (two protease levels x four urease levels).
Table 1. Urease activity values in heat-treated soybeans1
Heat treatment (min.)
Urease activity (D pH)2
0
2.02
105
1.86
110
1.03
135
0.49
1In natura, autoclaved soybeans (120°C and 1.5 atmospheres). 2Urease activity was determined as per the AOAC method (1980).
Table 2. Composition of the experimental feeds and estimated nutrient levels
Ingredients
%
Nutrients
 
Corn
52.51
ME, kcal/kg
3,100
Heat-treated soybeans1
20.00
CP
22.00
Soybean meal
19.89
Ca
0.86
Meat and bone meal (41%)
3.65
av P
0.38
Celite
1.00
K
0.91
Limestone
0.98
Na
0.21
Soybean oil
0.87
Cl
0.34
Salt
0.43
Lys dig.
1.15
DL-Methionine, 99%
0.28
Met+Cys dig.
0.86
L-Lysine, 78%
0.11
Met dig.
0.58
Vitamin premix
0.10
Thre dig.
0.72
Maxiban
0.05
Arg dig.
1.41
Mineral premix
0.05
Trp dig.
0.22
Choline, 60%
0.02
Choline, ppm
1650
Linco-Spectin 440
0.02
 
 
Kaolin
0.02
 
 
Ronozyme NP CT
0.015
 
 
L-Threonine, 98%
0.01
 
 
1 In natura autoclaved soybeans (120°C and 1.5 atmospheres).
Results and Discussion
Results are shown in Table 3. The protease-supplemented birds had the best performance parameters and the highest carcass yields, with the lowest levels of abdominal fat deposition. Several authors have reported beneficial effects with the heat treatment of various grains and seeds, particularly soybeans, on poultry performance, particularly during their early life stages, due to the denaturalization of these proteins prior to digestion in the gastrointestinal tract (Gracia et al., 2003; Clarke and Wiseman, 2007). No protease x urease interaction existed, and the adverse effects on animal performance and carcass yields were gradually increased, together with urease levels. The absence of a more evident expression of enzyme supplementation on animal performance could have been due to the fact that protease inhibitors present in crude soybeans, could be only responsible for 40% bird grow depression, and pancreatic hypertrophy. This way, other substances with noxious effects on animal physiology should be considered, and their inactivation should be assured by using the appropriate heat treatments (Leeson and Atteh, 1996). It is thought that the increasing urease levels caused an increase the relative weights of both pancreas and duodenum, but protease supplementation reduced the size of these organs regardless of the urease levels (Table 3).
Table 3. Animal performance, carcass yield, and relative organ weights of birds fed growing urease levels1, supplemented or not with protease, from 1 to 28 days of age
 
Live wght
FI
WG
FCR
Carcass
Abdominal
fat
Pancreas
Duodenum
g
 
%
g/100 g PV
Enzyme
 
 
 
 
 
 
 
 
0
1.436b
2.168
1,397b
1.54a
69.76b
1.17b
0.295a
0.870a
200
1.491a
2.174
1,445a
1.47b
71.22a
1.04a
0.281b
0.832b
Urease, ∆pH1
 
 
 
 
 
 
 
 
0.13
1.535a
2.186
1,494a
1.46a
71.25a
1.06
0.232d
0.835b
0.23
1.509a
2.231
1,463a
1.49a
70.48ab
1.10
0.265c
0.814b
0.72
1.433b
2.109
1,388b
1.49a
70.29b
1.10
0.290b
0.833b
1.52
1.370b
2.157
1,317b
1.60b
69.85b
1.20
0.365a
0.937a
P
 
 
 
 
 
 
 
 
Enzime (E)
0.0464
0.1555
0.0401
0.0317
<.0001
0.0159
0.0088
0.0004
Urease (U)
<.0001
0.8840
<.0001
0.0115
0.0276
0.3656
<.0001
<.0001
E x U
0.6889
0.1913
0.8402
0.8410
0.6491
0.1242
0.8135
0.2219
Different letters in a column mean statistically-significant differences as per Tukey´s test  (P<0.05).
1Urease activity in the feed: 0.13 (level obtained with the inclusion of soybeans autoclaved for 135 min.); 0.23 (level obtained by the inclusion of soybeans autoclaved for 110 min.); 0.72 (level obtained with the inclusion of soybeans autoclaved for 105 min.); 1.52 (level obtained with the inclusion of non-autoclaved, crude soybeans).
Conclusions
Feed supplementation with protease showed to be effective in improving bird performance and yield. Increasing urease levels had rious effects on performance and resulted in increased relative weights of both pancreas and duodenum.
Bibliography
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