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Evaluation of pea protein isolates as a protein source for broilers
Evaluation of pea protein isolates as a protein source for broilers
Department of Animal Sciences, University of Manitoba, Winnipeg, MB R3T 2N2, Canada ABSTRACT A study was conducted to determine the effect of including pea protein isolate (PPI) in diets for broilers on performance, visceral organ weights, and nutrient digestibility. A total of 192 day-old chicks were assigned to 4 diets with 6 birds per cage and 8 replicates per treatment for a 21-d study. The diets included a corn-soybean meal-based basal diet with 0, 5, 10, or 15% of PPI. Total BW and feed disappearance were monitored weekly to determine ADG, ADFI, and feed conversion ratio per cage basis. Excreta samples were collected during the last 3 d of the experiment to determine the apparent total tract retention (ATTR) of protein and energy. On day 21, 3 birds from each cage were euthanized to collect ileal digesta to determine the apparent ileal digestibility (AID) of energy and amino acids (AA), and visceral organs were weighed. Increasing dietary inclusion of PPI resulted in a linear decrease in overall ADFI (P = 0.002) and ADG
(P = 0.001), and a linear increase in feed conversion ratio (P = 0.013). Dietary PPI quadratically increased (P = 0.005) the spleen weight. The weight of proventriculus showed both linear (P = 0.023) and quadratic (P = 0.005) reduction while the weight of gizzard was quadratically reduced (P = 0.002) with the increase in dietary PPI content. Weights of small and large intestine showed both linear (P < 0.05) and quadratic (P < 0.05) reduction with increasing dietary PPI content. An increase in the dietary level of PPI resulted in a quadratic reduction (P < 0.05) in ATTR of DM and CP. The AID of His, Asp, Glu, Gly, and Ser showed a quadratic reduction (P < 0.05), Tyr a linear reduction (P = 0.031) and Cys and Pro both linear (P < 0.05) and quadratic (P < 0.05) reduction with dietary inclusion of PPI. In conclusion, formulating diets with increasing PPI linearly decreased the growth performance of broilers.
Key words: broiler, nutrient digestibility, organ weight, pea protein isolates, performance 2018 Poultry Science 0:1–8 http://dx.doi.org/10.3382/ps/pey387
INTRODUCTION
alkaline extraction for separating the protein from field pea, followed by acidic precipitation (Sumner et al., 1981) producing the pea protein isolates (PPI) with low concentrations of anti-nutritional factors. Furthermore, PPI contain around 4 times more CP than the parent field pea (Le Guen et al., 1995a; Owusu-Asiedu et al., 2003), making it an excellent protein source for non-ruminants. Pea protein isolates are rich in most of the indispensable amino acids (AA), especially lysine (Nandha et al., 2013). The high lysine concentration can be beneficial while formulating low protein diets with cereal grains naturally low in lysine, resulting in a reduced requirement of synthetic AA. Few studies have evaluated the nutritive value of pea proteins, mostly the pea protein concentrates for swine and poultry through performance and nutrient digestibility. Moreover, only a few studies have determined the ileal digestible AA content of PPI fed to broilers. Apparent ileal digestibility (AID) of most of the AA was found to be higher in PPI when compared to the whole pea in swine (Le Guen et al., 1995b; Woyengo et al., 2015) and poultry (Nandha et al., 2013). However, studies have shown that inclusion of pea protein concentrates in diets of young pigs can reduce the growth performance, mainly by lowering the
Pea (Pisum sativum) is a major source of protein, being used both as human food and animal feed (Fredrikson et al., 2001). However, peas contain anti-nutritional factors such as antigenic proteins, trypsin inhibitors, α-amylase inhibitors, lectins, alkaloids, tannins, and saponins (Rohe et al., 2017), which can reduce the nutrient digestibility and performance when fed to livestock. Processing of feed ingredients was shown to reduce the anti-nutritional factors and thereby improving nutritional value (Akande and Fabiyi, 2010). Field peas are processed through various commercial techniques such as air classification, wet milling, and membrane treatment to extract the protein fraction known as protein concentrates, from the starch and fiber. Taking the concentration procedure a step further, an “isolation technique” eliminates a much higher fraction of the nonprotein content. Isolation technique involves the use of
C 2018 Poultry Science Association Inc. Received September 27, 2017. Accepted October 8, 2018. 1 Corresponding author: Martin [email protected]
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D. E. Velayudhan, G. A. Mejicanos, and C. M. Nyachoti1
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VELAYUDHAN ET AL. Table 1. Ingredient and nutrient composition of experimental diets.1 Dietary PPI2 inclusion level, % Item
5
10
15
47.49 0.00 41.50 5.59 1.64 1.68 1.00 0.50 0.02 0.11 0.17 0.30
54.94 5.00 30.90 3.58 1.65 1.73 1.00 0.50 0.03 0.15 0.22 0.30
62.31 10.00 20.34 1.59 1.65 1.82 1.00 0.50 0.03 0.18 0.28 0.30
69.25 15.00 9.82 0.00 1.68 1.86 1.00 0.50 0.04 0.22 0.33 0.30
3,000 22.4 1.05 0.74 1.26 0.51 0.90
3,000 22.4 1.05 0.77 1.26 0.51 0.88
3,000 22.2 1.05 0.76 1.25 0.50 0.86
3,000 22.2 1.05 0.78 1.25 0.51 0.87
4,217 10.1 7.4
4,159 9.5 6.3
4,098 8.8 4.7
4,057 8.2 3.6
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as fed basis. PPI = Pea protein isolates. Analyzed composition of PPI: CP = 78.4%, GE = 5,292 kcal/kg, DM = 93.1%. 3 Provided per kilogram of diet: vitamin A, 8,255 IU; vitamin D3, 3,000 IU; vitamin E, 30 IU; vitamin B12, 0.013 mg; vitamin K3, 2.0 mg; niacin, 41.2 mg; choline, 1300.5 mg; folic acid, 1.0 mg; biotin, 0.25 mg; pyridoxine, 4.0 mg; thiamine, 4.0 mg; calcium pantothenic acid, 11.0 mg; riboflavin, 6.0 mg. 4 Provided per kilogram of diet: manganese, 70.0 mg; zinc, 80.0 mg; iron, 80.0 mg; iodine, 0.5 mg; copper, 10 mg; selenium, 0.3 mg. 2
daily feed intake (Christison and Parra de Solano, 1982; Valencia et al., 2008). To the best of our knowledge, no studies have been conducted to evaluate the effect of feeding diets containing PPI as a protein source on performance of broiler chicken. Therefore, the objective of the current study was to determine the effects of feeding increasing levels of PPI as a source of dietary protein on performance, apparent ileal AA digestibility, and apparent total tract protein and energy retention of diets fed to broilers.
MATERIALS AND METHODS All experimental procedures were reviewed and approved by the University of Manitoba Animal Care Committee, and birds were cared for and handled in accordance with the guidelines of the Canadian Council on Animal Care (CCAC, 2009).
Animals and Housing A total of 192 day-old male broiler chicks (Ross 308) were obtained from a local hatchery (Carlton Hatchery, Grunthal, Manitoba, Canada) and used in a 21-d study. The chicks were individually weighed upon arrival and divided into 32 groups of 6 birds balanced for BW. They were then group weighed, and each group was
housed in a cage in an electrically heated Super brooder (Alternative Design Manufacturing and Supply, Siloam Springs, AR). The room and brooder temperatures were set at 32 and 29◦ C, respectively, during the first week. Subsequently, heat supply in the brooder was switched off, and room temperature was reduced by 1◦ C each week. The light was provided for 24 h daily throughout the experiment.
Experimental Diets The experimental diets include a corn-soybean mealbased basal diet containing either 0, 5, 10, or 15% of PPI (Table 1). Several sources, including the NRC (1994) nutrient requirements, Breeder Recommendations (Aviagen, 2014), and feed industry recommendations (personal communication) were used to determine the adequate nutrient balance. All diets contained titanium dioxide (0.3%) as an indigestible marker. The PPI was obtained from Nutri-pea Ltd., Portage La Prairie, Manitoba, Canada.
Experimental Design and Procedure The 4 experimental diets were fed to the 32 groups (8 groups/diet) of birds from day 1 to 21 of age. Freshwater and feed were made available to all birds for ad libitum intake throughout the experiment. During the
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Ingredient, % of diet Corn PPI2 Soybean meal, 46% CP Canola oil Calcium carbonate Monocalcium phosphate Vitamin premix3 Mineral premix4 Lys-HCl L-Thr DL-Met Titanium dioxide Calculated composition ME, kcal/kg CP, % Ca, % Total P, % SID Lys, % SID Met, % SID Thr, % Analyzed composition GE, kcal/kg Neutral detergent fiber, % Ether extract, %
0
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PEA PROTEIN ISOLATES FOR BROILERS
Calculations
Sample Preparation and Analysis
Statistical Analysis
The experimental diet, excreta, and digesta samples were finely ground using a coffee grinder (CBG5 Smart Grind; Applica Consumer Products Inc., Shelton, CT) before chemical analysis. Diet, excreta, and digesta samples were analyzed for DM, CP, AA (diet and digesta only), gross energy (GE), and titanium dioxide. Dry matter content was determined according to the AOAC (1990; method 925.09) by oven drying 5 g of sample at 102◦ C overnight. Gross energy was measured using an adiabatic bomb calorimeter (model 6400, Parr Instrument, Moline, IL) which had been calibrated using benzoic acid as a standard. Nitrogen content was determined using the combustion method (method 990.03; AOAC, 1990) using the LECO N analyzer (model CNS-2000; LECO Corp., St. Joseph, MI), and CP was calculated as nitrogen × 6.25. Titanium contents were determined according to the procedures described by Lomer et al. (2000) and read on an inductively coupled plasma mass spectrometer (Varian Inc., Palo Alto, CA). Amino acid contents were determined according to AOAC (1990; method 982.30). Briefly, about 100 mg of each sample was digested in 4 mL of 6 M HCl for 24 h at 110◦ C followed by neutralization with 4 mL of 25% (wt/vol) NaOH and cooled to room temperature. The mixture was then equalized to 50 mL volume with sodium citrate buffer (pH 2.2) and analyzed using an AA analyzer (Sykam GmbH, F¨ urstenfeldbruck, Germany). Samples for analysis of sulfur-containing AA (methionine and cysteine) were subjected to performic acid oxidation before acid hydrolysis. Particle size of the diets was determined by using a Tyler Ro-Tap shaker machine (Model RX-29, W. S. Tyler Industrial Group, Mentor, OH) equipped with set of 13 sieves as recommended by the American Society of Agricultural and Biological Engineers (ASABE; Standard, 2003).
Data were analyzed using the MIXED procedure of SAS (SAS software 9.2; SAS Inst. Inc., Cary, NC) in a randomized complete block design, with the pen as the experimental unit. Results were considered significant at P ≤ 0.05, and tendencies were observed at 0.05 < P < 0.10. Orthogonal polynomials were used to determine linear and quadratic effects of increasing dietary PPI content.
Apparent ileal digestibility (AID) and total tract retention (ATTR) coefficients were calculated using the following equation: % Apparent nutrient digestibility = 100 − {[(Nd /Nf ) × (Tif /Tid )] × 100} where Nd = nutrient concentration in ileal digesta or excreta (mg/kg DM) Nf = nutrient concentration in feed (mg/kgDM) Tif = TiO2 concentration in feed (mg/kgDM) Tid = TiO2 concentration in ileal digesta or excreta (mg/kgDM)
RESULTS The analyzed composition of experimental diets and PPI is presented in Tables 1 and 2. The CP values in the diets were close to the calculated values. Particle size distributions of the diets are shown in Figure 1. Comparison of the particle size distributions of the diets showed that a variation in particle size distribution persisted between diets, particularly in the proportion of fine particles. Data on the effect of graded levels of PPI in diets on growth performance of broilers are presented in Table 3. Increasing the dietary inclusion level of PPI from 0 to 15% resulted in a linear decrease in overall feed intake (P = 0.002) and overall BW gain (P < 0.001). An increase in the dietary inclusion of PPI also resulted in a linear increase in feed conversion ratio (P = 0.013). Data on the effect of inclusion level of PPI in diets on organ weights are presented in Table 4. Increasing dietary inclusion of PPI showed a quadratic increase (P = 0.005) in the spleen weight, even though the spleen weight for diets with 10% PPI showed a significant decline. The weight of proventriculus showed both linear (P = 0.023) and quadratic (P = 0.005) reduction with an increase in the dietary inclusion of PPI. However, the weight of proventriculus significantly declined only with a dietary inclusion level of 10% PPI. The weight
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experimental period, total BW and feed disappearance were monitored weekly to determine ADG, ADFI, and feed conversion ratio on cage basis. Grab excreta samples were collected from each cage during the last 3 d of the trial to determine the apparent total tract energy and protein retention. On day 21, 3 birds per cage were killed by carbon dioxide euthanasia, and the digesta samples from the ileum (from Meckel’s diverticulum to a point 4 cm proximal to the ileocecal junction) were collected by gently squeezing the contents of the ileum into sample bags. Excreta and digesta samples within a cage were pooled into 1 bag and frozen immediately after collection and subsequently freezedried. The dried ileal digesta were stored in airtight bags at −4◦ C until required for chemical analysis. The liver, kidney, and gastrointestinal tract (proventriculus, gizzard, small and large intestine) were also removed from the killed birds and weighed after emptying the contents.
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VELAYUDHAN ET AL. Table 2. Analyzed DM, CP, and amino acid (AA) composition in pea protein isolates (PPI) and experimental diets (as-fed basis). Dietary PPI inclusion level, % PPI
0
5
10
15
DM, % CP, % Indispensable AA, % Arg His Ile Leu Lys Met Phe Thr Val Dispensable AA, % Ala Asp Cys Glu Gly Pro Ser Tyr
93.10 78.40
90.48 22.90
90.12 23.00
90.25 22.80
90.57 22.90
5.56 1.66 3.05 5.67 4.81 0.70 4.00 2.33 3.06
1.30 0.49 0.79 1.53 1.31 0.56 1.01 0.92 0.87
1.31 0.50 0.81 1.58 1.34 0.72 1.00 0.89 0.89
1.33 0.52 0.84 1.54 1.30 0.68 0.99 0.87 0.91
1.36 0.54 0.87 1.59 1.43 0.66 0.99 0.88 0.94
2.97 7.73 0.68 12.43 2.50 2.91 3.26 2.00
0.71 1.89 0.28 2.97 0.68 1.02 0.87 0.58
0.88 1.87 0.30 2.82 0.60 0.94 1.01 0.55
0.86 1.70 0.32 2.81 0.67 0.93 0.93 0.53
0.99 1.84 0.34 2.90 0.71 0.87 0.96 0.58
Amount retained on sieve (%)
24
0% PPI
22
5% PPI
20 18
10% PPI
16
15% PPI
14
GMD 0% PPI - 559 μm 5% PPI - 524 μm 10% PPI - 490 μm 15% PPI - 421 μm
12 10 8 6 4 2 0
3360 2360 1700 1180 850
600
420
297
212
150
103
73
53
37
Size of sieve opening (µm) Figure 1. Particle size distribution of diets. PPI = Pea protein isolates. GMD = Geometric mean diameter is the average particle size expressed microns (μ m).
of gizzard quadratically declined (P = 0.002) such that the gizzard weight decreased when the dietary level of PPI was increased from 0 to 15%. Weights of small and large intestine showed both linear (P < 0.05) and quadratic (P < 0.05) reduction with an increase in the dietary inclusion of PPI. However, a significant reduction in weights of small and large intestine was observed only with a dietary inclusion level of 10 and 15% PPI. There was no effect of dietary treatment on liver weight. An increase in the dietary level of PPI from 0 to 15% resulted in a quadratic reduction (P < 0.05) in ATTR
of DM and CP with ATTR of GE showing a tendency for reduction (quadratic P = 0.053) with increasing inclusion levels of PPI (Table 5). The AID values of AA in diets with graded levels of PPI are presented in Table 5. Among the indispensable AA, only AID of His showed a quadratic reduction (P = 0.008) with increasing dietary inclusion of PPI. However, the level of PPI inclusion (5, 10, and 15%) did not have any effect on AID of His. Also, a tendency for reduction in AID was observed for Leu (P = 0.087) and Phe (P = 0.065) with increasing inclusion levels of PPI. Among dispensable AA, AID of
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PEA PROTEIN ISOLATES FOR BROILERS Table 3. Effect of graded levels of pea protein isolates (PPI) in diets on growth performance of broilers from hatch to 21 d of age.1 Dietary PPI inclusion level, %
Body weight, g Initial (day 0) Final (day 21) Body weight gain, g
0
5
10
15
SEM
Linear
Quadratic
46.0 704.2a
45.6 700.2a
46.2 659.7a
45.2 607.5b
0.37 16.66
0.277 < 0.001
0.439 0.159
Week 1 Week 2 Week 3 Overall Feed Intake, g
103.4a 267.9a 286.9 658.2a
105.6a 244.2b 304.8 654.6a
107.7a 238.4b 267.4 613.6a
85.7b 206.7c 270.0 562.4b
3.99 8.07 14.68 16.60
0.008 < 0.001 0.192 < 0.001
0.005 0.619 0.605 0.162
Week 1 Week 2 Week 3 Overall Feed conversion ratio
121.1b 315.7a 406.6a,b 843.3a
129.5a,b 301.7a,b 416.1a 847.3a
139.1a 290.3b 376.5a,b 805.8a
118.2b 260.2c 370.9b 749.2b
4.14 6.09 13.98 17.15
0.162 < 0.001 0.026 0.002
0.002 0.197 0.590 0.089
0.004 0.068 0.389 0.013
0.730 0.706 0.617 0.929
Week 1 Week 2 Week 3 Overall
1.18b 1.18b 1.45 1.28b
1.23b 1.25a,b 1.37 1.30a,b
1.30a,b 1.22a,b 1.42 1.32a,b
1.38a 1.27a 1.38 1.33a
0.047 0.026 0.037 0.014
Means in the same row with different superscripts differ (P ≤ 0.05). Growth performance data are means of 8 pens of broilers with 6 broilers per pen.
a–c 1
Table 4. Effect of graded levels of pea protein isolates (PPI) in diets on organ weights of broilers from hatch to 21 d of age.1 Dietary PPI inclusion level, % Item
0
Organ weights, mg/g of BW Liver 30.9 Spleen 0.85a Proventriculus 6.1a Gizzard 19.9a Small intestine 34.8a Large intestine 8.5a
P-Value
5
10
15
SEM
linear
Quadratic
32.9 0.75a,b 5.9a 17.8b 32.7a 7.9a
28.7 0.68b 4.7b 17.7b 26.1b 5.8b
33.8 0.89a 5.8a 15.8c 29.3b 6.7b
1.29 0.05 0.20 0.64 1.41 0.32
0.421 0.748 0.023 0.123 0.008 < 0.001
0.219 0.005 0.005 0.002 0.012 0.029
Means in the same row with different superscripts differ (P ≤ 0.05). Organ weight data are means of 8 pens of broilers with 3 broilers per pen.
a–c 1
Asp, Glu, Gly, and Ser showed a quadratic reduction (P < 0.05) and AID of Tyr showed a linear reduction (P = 0.031) with increasing dietary inclusion of PPI. The AID of Cys and Pro showed both linear (P < 0.05) and quadratic (P < 0.05) reduction with increasing dietary inclusion of PPI. However, the level of inclusion of PPI (5, 10, and 15%) showed no effect AID values for dispensable AA.
DISCUSSION The protein content (78.4%) for the PPI used in the current study was comparable to the value for PPI that was used in our previous study (84.9%; Nandha et al., 2013). Moreover, the PPI used in the present study had a comparable CP values to soy protein isolates (86.2%; Chen et al., 2015). A 15% dietary inclusion of PPI in the current study resulted in reduced BW gain. The reduced BW gain as a result of increased dietary inclusion level of PPI could partly be attributed to reduced feed intake in birds.
Furthermore, this reduction in feed intake at a high inclusion level of PPI could be because of the extremely fine feed particles due to the presence of PPI as shown in Figure 1. Chewning et al. (2012) reported a similar reduction in feed intake in broilers fed diets containing finely ground corn, thus resulting in a lower BW gain. Similar effects of feed particle size were also reported with feed ingredients like wheat and sorghum, wherein broilers fed diets containing coarser particles had a better BW gain and feed efficiency when compared to those fed fine particle mash diets (Nir et al., 1995; Amerah et al., 2007). Moreover, uniformity of the feed particle size is another factor that influences feed intake in birds. Birds can differentiate feed particle size with the help of mechanoreceptors in the beak (Amerah et al., 2007) and birds of all ages have shown to prefer larger feed particles in the diet (Schiffman, 1968; Portella et al., 1988). However, when diets containing uniform particle size are fed, birds spend less time searching for larger particles (Amerah et al., 2007) and thereby increases the feed intake. The diets used in the current study
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P-Value
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VELAYUDHAN ET AL. Table 5. Effect of graded levels of pea protein isolates (PPI) in diets on apparent total tract retention (ATTR) of gross energy (GE) and protein, and apparent ileal digestibility (AID) of amino acids (AA) in broilers. Dietary PPI inclusion level, % 0
5
10
15
SEM
linear
Quadratic
69.8a 61.2a 72.9
65.1a,b 57.3a,b 74.6
63.6b 53.1b 70.7
61.9b 53.3b 70.9
2.21 2.62 1.65
0.117 0.315 0.440
0.039 0.029 0.053
79.8 54.3a 72.4 74.2 75.8 82.6 79.5 65.0 69.1
75.8 47.1a,b 67.6 73.2 73.2 86.1 73.5 65.2 64.6
70.7 42.6b 64.9 68.0 68.0 83.7 71.0 61.5 60.5
76.5 43.2b 65.4 67.0 67.9 85.5 70.9 62.3 62.3
3.65 2.74 3.69 3.50 4.09 2.03 2.89 3.14 3.26
0.295 0.084 0.377 0.904 0.674 0.344 0.176 0.992 0.304
0.251 0.008 0.198 0.087 0.119 0.901 0.065 0.311 0.104
63.1 67.4a 74.5a 78.8a 65.2a 75.9a 66.7 76.8a
64.9 62.7a,b 53.6b 72.8a,b 58.6a,b 65.9b 64.1 66.5b
62.1 59.4b 50.9b 68.1b 57.5b 63.4b 59.4 65.6b
61.9 59.8b 50.1b 68.8b 54.6b 64.9b 61.6 67.9b
3.46 2.72 3.19 3.17 2.37 3.18 2.99 3.28
0.579 0.492 0.001 0.193 0.121 0.034 0.461 0.031
0.483 0.025 0.001 0.028 0.021 0.042 0.100 0.147
ATTR, % DM CP GE AID, % Indispensable AA Arg His Ile Leu Lys Met Phe Thr Val Dispensable AA Ala Asp Cys Glu Gly Pro Ser Tyr a–c
Means in the same row with different superscripts differ (P ≤ 0.05).
had moderately ground corn-soybean meal with very fine particle sized PPI, and this dissimilarity in particle size could be one reason for a lower feed intake by birds fed high PPI containing diets. When compared to similar protein sources like the soy protein isolates, growth performance of broiler chicken in the present study has shown comparable results. Chen et al. (2015) in a 21-d study reported similar BW gain (524 g/bird) and daily feed intake (814 g/bird) in birds fed a corn-based diet with 16.5% soy protein isolates when compared to those fed 15% PPI in the current study. Also, Jankowski et al. (2009) have reported a significant reduction in BW gain in turkeys when fed diets containing soy protein isolates (19.5%) compared to those fed a wheat-soybean meal based control diet. Yet another reason for a reduced BW gain in birds fed 15% PPI could be because of a lower level of dietary fat. Since all the diets contained similar levels of energy and protein, the reduced performance in birds with low dietary fat suggests that energy from fat is more efficiently utilized than that from other ingredients as observed in previous studies (Atteh et al., 1983; Nitsan et al., 1997; Peebles et al., 2000). On the contrary, few studies also observed no difference on dietary fat inclusion levels on growth performance in broilers (Anderotti et al., 2004; Rezaeipour et al., 2016). Digestibility of fats is lower in young birds and found to increases with age (Nitsan et al., 1997). Henceforth, at an early age in birds with low-fat digestibility, the benefits of dietary fat supplementing are not always consistent (Wiseman and Salvador, 1991; Nitsan et al., 1997).
Development of various sections of the gastrointestinal tract in birds has been shown to be influenced by the feed particle size. The muscular stomach or the gizzard in birds helps in the reduction of the particle size of ingested feed and mixes them with digestive enzymes. Larger feed particles in the diet have shown to have a stimulatory effect on the gizzard, resulting in increased size of the gizzard (Jacobs et al., 2010). Hence when fed fine particle size diets, the gizzard is relatively underdeveloped (Taylor and Jones, 2004) as evident in the current study wherein birds fed PPI containing diets had a lower a gizzard weight. This reduction in the gizzard weight could probably be due to the lack of mechanical stimulation by the feed because of the presence of fine particle sized PPI. Likewise, studies have shown small intestinal hypertrophy when fed fine particle size mash diets (Nir et al., 1994) and a lower relative duodenal weight in birds fed coarse particle diets compared to those fed fine particle diets (Nir et al., 1995; Gabriel et al., 2003). However, such observations were not found in the current study, the reasons for which are unclear. Larger particle size in the diets also results in a longer residence time within the stomach since coarser particles are retained in the gastrointestinal tract for a longer duration when compared to fine particles (Nir et al., 1994; Amerah et al., 2007). Moreover, a slower passage rate may better facilitate the mixing of feed with digestive enzymes (Qaisrani et al., 2014), thereby improving the digestibility of nutrients. The reduction in the ATTR of nutrients in the current study with increasing
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PEA PROTEIN ISOLATES FOR BROILERS
REFERENCES Akande, K. E., and E. F. Fabiyi. 2010. Effect of processing methods on some antinutritional factors in legume seeds for poultry feeding. Int. J. Poult. Sci. 9:996–1001. Amerah, A. M., V. Ravindran, R. G. Lentle, and D. G. Thomas. 2007. Feed particle size: Implications on the digestion and performance of poultry. World Poult. Sci. J. 63:439–455. Anderotti, M. D. O., O. M. Junqueira, M. J. B. Barbosa, L. C. Cancherini, L. F. Araujo, and E. A. Rodrigues. 2004. Intestinal transit time, performance, carcass characteristics and body composition in broilers fed isoenergy diets formulated with different levels of soybean oil. R. Bras. Zootec. 33:870–879. AOAC. 1990. Official Methods of Analysis. 15th ed. Assoc. Offic. Anal. Chem., Washington, DC. Atteh, J. O., S. Leeson, and R. J. Julian. 1983. Effects of dietary levels and types of fat on performance and mineral metabolism of broiler chicks. Poult. Sci. 62:2403–2411. Aviagen. 2014. Ross 308: Broiler Nutrition Specification. Ross Breeders Limited, Newbridge, Midlothian, Scotland, UK. Bandegan, A., A. Golian, E. Kiarie, R. L. Payne, G. H. Crow, W. Guenter, and C. M. Nyachoti. 2011. Standardized ileal amino acid digestibility in wheat, barley, pea and flaxseed for broiler chickens. Can. J. Anim. Sci. 91:103–111. Canadian Council on Animal Care. 2009. Guide to the Care and Use of Experimental Animals. 2nd ed., Vol. 1. Can. Council Animal Care, Ottawa, Ontario, Canada. Chen, X., Y. P. Chen, D. W. Wu, C. Wen, and Y. M. Zhou. 2015. Effects of heat-oxidized soy protein isolate on growth performance and digestive function of broiler chickens at early age. AsianAustralas. J. Anim. Sci. 28:544–550. Chewning, C. G., C. R. Stark, and J. Brake. 2012. Effects of particle size and feed form on broiler performance. J. Appl. Poult. Res. 21:830–837. Christison, G. I., and N. M. Parra de Solano. 1982. Utilization of protein from peas, barley, buttermilk powder and soy-
bean meal by early weaned pigs. Can. J. Anim. Sci. 62:899– 905. Fredrikson, M., P. Biot, M. L. Alminger, N. G. Carlsson, and A. S. Sandberg. 2001. Production process for high-quality pea-protein isolate with low content of oligosaccharides and phytate. J. Agric. Food Chem. 49:1208–1212. Fern´ andez-Quintela, A., M. T. Macarulla, A. S. Del Barrio, and J. A. Mart´ınez. 1997. Composition and functional properties of protein isolates obtained from commercial legumes grown in northern Spain. Plant Foods Hum. Nutr. 51:331–341. Gabriel, I., S. Maillet, and M. Leconte. 2003. Differences in the digestive tract characteristics of broiler chickens fed on complete pelleted diet or on whole wheat added to pelleted protein concentrate. Br. Poult. Sci. 44:283–290. Jacobs, C. M., P. L. Utterback, and C. M. Parsons. 2010. Effects of corn particle size on growth performance and nutrient utilization in young chicks. Poult. Sci. 89:539–544. Jankowski, J., J. Juskiewicz, K. Gulewicz, A. Lecewicz, B. A. Slominski, and Z. Zdunczyk. 2009. The effect of diets containing soybean meal, soybean protein concentrate, and soybean protein isolate of different oligosaccharide content on growth performance and gut function of young turkeys. Poult. Sci. 88:2132–2140. Le Guen, M. P., J. Huisman, J. Gu´eguen, G. Beelen, and M. W. A. Verstegen. 1995. Effects of a concentrate of pea antinutritional factors on pea protein digestibility in piglets. Livest. Prod. Sci. 44:157–167. Le Guen, M. P., J. Huisman, and M. W. A. Verstegen. 1995. Partition of the amino acids in ileal digesta from piglets fed pea protein diets. Livest. Prod. Sci. 44:169–178. Lomer, M. C. E., R. P. H. Thompson, J. Commisso, C. L. Keen, and J. J. Powell. 2000. Determination of titanium dioxide in foods using inductively coupled plasma optical emission spectrometry. Analyst 125:2339–2343. Nandha, N. K., T. A. Woyengo, R. L. Payne, and C. M. Nyachoti. 2013. Ileal digestibility of amino acids in pea protein isolates, wheat-corn distillers dried grains with solubles, and short-season corn fed to broiler chicks. Poult. Sci. 92:184–191. Nir, I., R. Hillel, I. Ptichi, and G. Shefet. 1995. Effect of particle size on performance: 3. Grinding pelleting interactions. Poult. Sci. 74:771–783. Nir, I., R. Hillel, G. Shefet, and Z. Nitsan. 1994. Effect of grain particle size on performance. 2. Grain texture interactions. Poult. Sci. 73:781–791. Nitsan, Z., A. Dvorin, Z. Zoref, and S. Mokady. 1997. Effect of added soyabean oil and dietary energy on metabolisable and net energy of broiler diets. Br. Poult. Sci. 38:101–106. NRC. 1994. Nutrient Requirements of Poultry. 9th rev. ed. Natl. Acad. Press, Washington, DC. Owusu-Ansah, Y.J., and S. M. McCurdy. 1991. Pea proteins: a review of chemistry, technology of production, and utilization. Food Rev. Int. 7:103–134. Owusu-Asiedu, A., C. M. Nyachoti, and R. R. Marquardt. 2003. Response of early-weaned pigs to an enterotoxigenic Escherichia coli (K88) challenge when fed diets containing spray-dried porcine plasma or pea protein isolate plus egg yolk antibody, zinc oxide, fumaric acid, or antibiotic. J. Anim. Sci. 81:1790–1798. Peebles, E. D., C. D. Zumwalt, S. M. Doyle, P. D. Gerard, M.A. Latour, C. R. Boyle, and T. W. Smith. 2000. Effects of dietary fat type and level on broiler breeder performance. Poult. Sci. 79: 629–639. Portella, F. J., L. J. Caston, and S. Leeson. 1988. Apparent feed particle size preference by laying hens. Can. J. Anim. Sci. 68:915– 922. Qaisrani, S. N., P. C. A. Moquet, M. M. Van Krimpen, R. P. Kwakkel, M. W. A. Verstegen, and W. H. Hendriks. 2014. Protein source and dietary structure influence growth performance, gut morphology, and hindgut fermentation characteristics in broilers. Poult. Sci. 93:3053–3064. Rezaeipour, V., H. Alinejad, and S. Asadzadeh. 2016. Growth performance, carcass characteristics and blood metabolites of broiler chickens fed diets formulated on total or digestible amino acids basis with bovine bile salts powder and soybean oil. J. Cent. Eur. Agric. 17:272–284.
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inclusion of PPI could be attributed to the increase in the digesta passage rate because of finely ground PPI in diets. Pea protein isolates are refined protein fractions derived using wet processing technique (Vose et al. 1976; Owusu-Ansah and McCurdy, 1991) and are considered to contain only marginal levels of anti-nutritive factors (Nandha et al., 2013). The relatively low levels of antinutritive factors explain the reason for a higher AID of AA in PPI when compared to those observed for whole peas (Bandegan et al., 2011) and pea protein concentrates (Valencia et al., 2009) fed to broilers. However, Fern´ andez-Quintela et al. (1997) have reported around 50% trypsin inhibitor activity and phytate levels retained in PPIs after processing when compared to the pea seeds. The presence of these anti-nutritive factors could be among the probable reasons for the lower AA digestibility at higher PPI inclusion rate (15%) in the current study. In conclusion, increasing inclusion of PPI in broiler chick diets showed a linear reduction in growth performance of birds, with a negative impact on ATTR of nutrients and AID of most of the dispensable AA. However, based on the results from the current study it is not possible to determine an optimum inclusion level for PPI in broilers. Hence, this warrants more investigations into the mechanisms underlying the negative effects of PPI inclusion on growth performance and nutrient digestibility in broilers.
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VELAYUDHAN ET AL. diets for young pigs: Effects on productivity and digestive traits. Livest. Sci. 118:1–10. Valencia, D. G., M. P. Serrano, E. Jimenez-Moreno, R. Lazaro, and G. G. Mateos. 2009. Ileal digestibility of amino acids of pea protein concentrate and soya protein sources in broiler chicks. Livest. Sci. 121:21–27. Vose, J. R., M. J. Basterrechea, P. A. J. Gorin, A. J. Finlayson, and C. G. Young. 1976. Air classification of field peas and horse-bean flours: chemical studies of starch and protein fractions. Cereal Chem. 53:928–936. Wiseman, J., and F. Salvador. 1991. The influence of free fatty acid content and degree of saturation on the apparent metabolizable energy value of fats fed to broilers. Poult. Sci. 70:573–582. Woyengo, T. A., J. M. Heo, Y. L. Yin, and C. M. Nyachoti. 2015. Standardized and true ileal amino acid digestibilities in field pea and pea protein isolate fed to growing pigs. Anim. Feed Sci. Technol. 207:196–203.
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R¨ohe, I., T. W. G¨ obel, F. Goodarzi Boroojeni, and J. Zentek. 2017. Effect of feeding soybean meal and differently processed peas on the gut mucosal immune system of broilers. Poul. Sci. 0:0– 10. Schiffman, H. R. 1968. Texture preference in the domestic chick. J. Comp. Physiol. Psychol. 66:540–541. Sumner, A. K., M. A. Nielsen, and C. G. Youngs. 1981. Production and evaluation of pea protein isolate. J. Food Sci. 46:364– 366. Standard, A. S. A. E. 2003. Method of Determining and Expressing Fineness of Feed Materials by Sieving. American Society of Agricultural and Biological Engineers, St. Joseph, Michigan. Taylor, R. D., and G. P. D. Jones. 2004. The incorporation of whole grain into pelleted broiler chicken diets. II. Gastrointestinal and digesta characteristics. Br. Poult. Sci. 45:237–246. Valencia, D. G., M. P. Serrano, C. Centeno, R. L´ azaro, and G. G. Mateos. 2008. Pea protein as a substitute of soya bean protein in
Department of Animal Sciences, University of Manitoba, Winnipeg, MB R3T 2N2, Canada ABSTRACT A study was conducted to determine the effect of including pea protein isolate (PPI) in diets for broilers on performance, visceral organ weights, and nutrient digestibility. A total of 192 day-old chicks were assigned to 4 diets with 6 birds per cage and 8 replicates per treatment for a 21-d study. The diets included a corn-soybean meal-based basal diet with 0, 5, 10, or 15% of PPI. Total BW and feed disappearance were monitored weekly to determine ADG, ADFI, and feed conversion ratio per cage basis. Excreta samples were collected during the last 3 d of the experiment to determine the apparent total tract retention (ATTR) of protein and energy. On day 21, 3 birds from each cage were euthanized to collect ileal digesta to determine the apparent ileal digestibility (AID) of energy and amino acids (AA), and visceral organs were weighed. Increasing dietary inclusion of PPI resulted in a linear decrease in overall ADFI (P = 0.002) and ADG
(P = 0.001), and a linear increase in feed conversion ratio (P = 0.013). Dietary PPI quadratically increased (P = 0.005) the spleen weight. The weight of proventriculus showed both linear (P = 0.023) and quadratic (P = 0.005) reduction while the weight of gizzard was quadratically reduced (P = 0.002) with the increase in dietary PPI content. Weights of small and large intestine showed both linear (P < 0.05) and quadratic (P < 0.05) reduction with increasing dietary PPI content. An increase in the dietary level of PPI resulted in a quadratic reduction (P < 0.05) in ATTR of DM and CP. The AID of His, Asp, Glu, Gly, and Ser showed a quadratic reduction (P < 0.05), Tyr a linear reduction (P = 0.031) and Cys and Pro both linear (P < 0.05) and quadratic (P < 0.05) reduction with dietary inclusion of PPI. In conclusion, formulating diets with increasing PPI linearly decreased the growth performance of broilers.
Key words: broiler, nutrient digestibility, organ weight, pea protein isolates, performance 2018 Poultry Science 0:1–8 http://dx.doi.org/10.3382/ps/pey387
INTRODUCTION
alkaline extraction for separating the protein from field pea, followed by acidic precipitation (Sumner et al., 1981) producing the pea protein isolates (PPI) with low concentrations of anti-nutritional factors. Furthermore, PPI contain around 4 times more CP than the parent field pea (Le Guen et al., 1995a; Owusu-Asiedu et al., 2003), making it an excellent protein source for non-ruminants. Pea protein isolates are rich in most of the indispensable amino acids (AA), especially lysine (Nandha et al., 2013). The high lysine concentration can be beneficial while formulating low protein diets with cereal grains naturally low in lysine, resulting in a reduced requirement of synthetic AA. Few studies have evaluated the nutritive value of pea proteins, mostly the pea protein concentrates for swine and poultry through performance and nutrient digestibility. Moreover, only a few studies have determined the ileal digestible AA content of PPI fed to broilers. Apparent ileal digestibility (AID) of most of the AA was found to be higher in PPI when compared to the whole pea in swine (Le Guen et al., 1995b; Woyengo et al., 2015) and poultry (Nandha et al., 2013). However, studies have shown that inclusion of pea protein concentrates in diets of young pigs can reduce the growth performance, mainly by lowering the
Pea (Pisum sativum) is a major source of protein, being used both as human food and animal feed (Fredrikson et al., 2001). However, peas contain anti-nutritional factors such as antigenic proteins, trypsin inhibitors, α-amylase inhibitors, lectins, alkaloids, tannins, and saponins (Rohe et al., 2017), which can reduce the nutrient digestibility and performance when fed to livestock. Processing of feed ingredients was shown to reduce the anti-nutritional factors and thereby improving nutritional value (Akande and Fabiyi, 2010). Field peas are processed through various commercial techniques such as air classification, wet milling, and membrane treatment to extract the protein fraction known as protein concentrates, from the starch and fiber. Taking the concentration procedure a step further, an “isolation technique” eliminates a much higher fraction of the nonprotein content. Isolation technique involves the use of
C 2018 Poultry Science Association Inc. Received September 27, 2017. Accepted October 8, 2018. 1 Corresponding author: Martin [email protected]
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D. E. Velayudhan, G. A. Mejicanos, and C. M. Nyachoti1
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VELAYUDHAN ET AL. Table 1. Ingredient and nutrient composition of experimental diets.1 Dietary PPI2 inclusion level, % Item
5
10
15
47.49 0.00 41.50 5.59 1.64 1.68 1.00 0.50 0.02 0.11 0.17 0.30
54.94 5.00 30.90 3.58 1.65 1.73 1.00 0.50 0.03 0.15 0.22 0.30
62.31 10.00 20.34 1.59 1.65 1.82 1.00 0.50 0.03 0.18 0.28 0.30
69.25 15.00 9.82 0.00 1.68 1.86 1.00 0.50 0.04 0.22 0.33 0.30
3,000 22.4 1.05 0.74 1.26 0.51 0.90
3,000 22.4 1.05 0.77 1.26 0.51 0.88
3,000 22.2 1.05 0.76 1.25 0.50 0.86
3,000 22.2 1.05 0.78 1.25 0.51 0.87
4,217 10.1 7.4
4,159 9.5 6.3
4,098 8.8 4.7
4,057 8.2 3.6
1
as fed basis. PPI = Pea protein isolates. Analyzed composition of PPI: CP = 78.4%, GE = 5,292 kcal/kg, DM = 93.1%. 3 Provided per kilogram of diet: vitamin A, 8,255 IU; vitamin D3, 3,000 IU; vitamin E, 30 IU; vitamin B12, 0.013 mg; vitamin K3, 2.0 mg; niacin, 41.2 mg; choline, 1300.5 mg; folic acid, 1.0 mg; biotin, 0.25 mg; pyridoxine, 4.0 mg; thiamine, 4.0 mg; calcium pantothenic acid, 11.0 mg; riboflavin, 6.0 mg. 4 Provided per kilogram of diet: manganese, 70.0 mg; zinc, 80.0 mg; iron, 80.0 mg; iodine, 0.5 mg; copper, 10 mg; selenium, 0.3 mg. 2
daily feed intake (Christison and Parra de Solano, 1982; Valencia et al., 2008). To the best of our knowledge, no studies have been conducted to evaluate the effect of feeding diets containing PPI as a protein source on performance of broiler chicken. Therefore, the objective of the current study was to determine the effects of feeding increasing levels of PPI as a source of dietary protein on performance, apparent ileal AA digestibility, and apparent total tract protein and energy retention of diets fed to broilers.
MATERIALS AND METHODS All experimental procedures were reviewed and approved by the University of Manitoba Animal Care Committee, and birds were cared for and handled in accordance with the guidelines of the Canadian Council on Animal Care (CCAC, 2009).
Animals and Housing A total of 192 day-old male broiler chicks (Ross 308) were obtained from a local hatchery (Carlton Hatchery, Grunthal, Manitoba, Canada) and used in a 21-d study. The chicks were individually weighed upon arrival and divided into 32 groups of 6 birds balanced for BW. They were then group weighed, and each group was
housed in a cage in an electrically heated Super brooder (Alternative Design Manufacturing and Supply, Siloam Springs, AR). The room and brooder temperatures were set at 32 and 29◦ C, respectively, during the first week. Subsequently, heat supply in the brooder was switched off, and room temperature was reduced by 1◦ C each week. The light was provided for 24 h daily throughout the experiment.
Experimental Diets The experimental diets include a corn-soybean mealbased basal diet containing either 0, 5, 10, or 15% of PPI (Table 1). Several sources, including the NRC (1994) nutrient requirements, Breeder Recommendations (Aviagen, 2014), and feed industry recommendations (personal communication) were used to determine the adequate nutrient balance. All diets contained titanium dioxide (0.3%) as an indigestible marker. The PPI was obtained from Nutri-pea Ltd., Portage La Prairie, Manitoba, Canada.
Experimental Design and Procedure The 4 experimental diets were fed to the 32 groups (8 groups/diet) of birds from day 1 to 21 of age. Freshwater and feed were made available to all birds for ad libitum intake throughout the experiment. During the
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Ingredient, % of diet Corn PPI2 Soybean meal, 46% CP Canola oil Calcium carbonate Monocalcium phosphate Vitamin premix3 Mineral premix4 Lys-HCl L-Thr DL-Met Titanium dioxide Calculated composition ME, kcal/kg CP, % Ca, % Total P, % SID Lys, % SID Met, % SID Thr, % Analyzed composition GE, kcal/kg Neutral detergent fiber, % Ether extract, %
0
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PEA PROTEIN ISOLATES FOR BROILERS
Calculations
Sample Preparation and Analysis
Statistical Analysis
The experimental diet, excreta, and digesta samples were finely ground using a coffee grinder (CBG5 Smart Grind; Applica Consumer Products Inc., Shelton, CT) before chemical analysis. Diet, excreta, and digesta samples were analyzed for DM, CP, AA (diet and digesta only), gross energy (GE), and titanium dioxide. Dry matter content was determined according to the AOAC (1990; method 925.09) by oven drying 5 g of sample at 102◦ C overnight. Gross energy was measured using an adiabatic bomb calorimeter (model 6400, Parr Instrument, Moline, IL) which had been calibrated using benzoic acid as a standard. Nitrogen content was determined using the combustion method (method 990.03; AOAC, 1990) using the LECO N analyzer (model CNS-2000; LECO Corp., St. Joseph, MI), and CP was calculated as nitrogen × 6.25. Titanium contents were determined according to the procedures described by Lomer et al. (2000) and read on an inductively coupled plasma mass spectrometer (Varian Inc., Palo Alto, CA). Amino acid contents were determined according to AOAC (1990; method 982.30). Briefly, about 100 mg of each sample was digested in 4 mL of 6 M HCl for 24 h at 110◦ C followed by neutralization with 4 mL of 25% (wt/vol) NaOH and cooled to room temperature. The mixture was then equalized to 50 mL volume with sodium citrate buffer (pH 2.2) and analyzed using an AA analyzer (Sykam GmbH, F¨ urstenfeldbruck, Germany). Samples for analysis of sulfur-containing AA (methionine and cysteine) were subjected to performic acid oxidation before acid hydrolysis. Particle size of the diets was determined by using a Tyler Ro-Tap shaker machine (Model RX-29, W. S. Tyler Industrial Group, Mentor, OH) equipped with set of 13 sieves as recommended by the American Society of Agricultural and Biological Engineers (ASABE; Standard, 2003).
Data were analyzed using the MIXED procedure of SAS (SAS software 9.2; SAS Inst. Inc., Cary, NC) in a randomized complete block design, with the pen as the experimental unit. Results were considered significant at P ≤ 0.05, and tendencies were observed at 0.05 < P < 0.10. Orthogonal polynomials were used to determine linear and quadratic effects of increasing dietary PPI content.
Apparent ileal digestibility (AID) and total tract retention (ATTR) coefficients were calculated using the following equation: % Apparent nutrient digestibility = 100 − {[(Nd /Nf ) × (Tif /Tid )] × 100} where Nd = nutrient concentration in ileal digesta or excreta (mg/kg DM) Nf = nutrient concentration in feed (mg/kgDM) Tif = TiO2 concentration in feed (mg/kgDM) Tid = TiO2 concentration in ileal digesta or excreta (mg/kgDM)
RESULTS The analyzed composition of experimental diets and PPI is presented in Tables 1 and 2. The CP values in the diets were close to the calculated values. Particle size distributions of the diets are shown in Figure 1. Comparison of the particle size distributions of the diets showed that a variation in particle size distribution persisted between diets, particularly in the proportion of fine particles. Data on the effect of graded levels of PPI in diets on growth performance of broilers are presented in Table 3. Increasing the dietary inclusion level of PPI from 0 to 15% resulted in a linear decrease in overall feed intake (P = 0.002) and overall BW gain (P < 0.001). An increase in the dietary inclusion of PPI also resulted in a linear increase in feed conversion ratio (P = 0.013). Data on the effect of inclusion level of PPI in diets on organ weights are presented in Table 4. Increasing dietary inclusion of PPI showed a quadratic increase (P = 0.005) in the spleen weight, even though the spleen weight for diets with 10% PPI showed a significant decline. The weight of proventriculus showed both linear (P = 0.023) and quadratic (P = 0.005) reduction with an increase in the dietary inclusion of PPI. However, the weight of proventriculus significantly declined only with a dietary inclusion level of 10% PPI. The weight
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experimental period, total BW and feed disappearance were monitored weekly to determine ADG, ADFI, and feed conversion ratio on cage basis. Grab excreta samples were collected from each cage during the last 3 d of the trial to determine the apparent total tract energy and protein retention. On day 21, 3 birds per cage were killed by carbon dioxide euthanasia, and the digesta samples from the ileum (from Meckel’s diverticulum to a point 4 cm proximal to the ileocecal junction) were collected by gently squeezing the contents of the ileum into sample bags. Excreta and digesta samples within a cage were pooled into 1 bag and frozen immediately after collection and subsequently freezedried. The dried ileal digesta were stored in airtight bags at −4◦ C until required for chemical analysis. The liver, kidney, and gastrointestinal tract (proventriculus, gizzard, small and large intestine) were also removed from the killed birds and weighed after emptying the contents.
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VELAYUDHAN ET AL. Table 2. Analyzed DM, CP, and amino acid (AA) composition in pea protein isolates (PPI) and experimental diets (as-fed basis). Dietary PPI inclusion level, % PPI
0
5
10
15
DM, % CP, % Indispensable AA, % Arg His Ile Leu Lys Met Phe Thr Val Dispensable AA, % Ala Asp Cys Glu Gly Pro Ser Tyr
93.10 78.40
90.48 22.90
90.12 23.00
90.25 22.80
90.57 22.90
5.56 1.66 3.05 5.67 4.81 0.70 4.00 2.33 3.06
1.30 0.49 0.79 1.53 1.31 0.56 1.01 0.92 0.87
1.31 0.50 0.81 1.58 1.34 0.72 1.00 0.89 0.89
1.33 0.52 0.84 1.54 1.30 0.68 0.99 0.87 0.91
1.36 0.54 0.87 1.59 1.43 0.66 0.99 0.88 0.94
2.97 7.73 0.68 12.43 2.50 2.91 3.26 2.00
0.71 1.89 0.28 2.97 0.68 1.02 0.87 0.58
0.88 1.87 0.30 2.82 0.60 0.94 1.01 0.55
0.86 1.70 0.32 2.81 0.67 0.93 0.93 0.53
0.99 1.84 0.34 2.90 0.71 0.87 0.96 0.58
Amount retained on sieve (%)
24
0% PPI
22
5% PPI
20 18
10% PPI
16
15% PPI
14
GMD 0% PPI - 559 μm 5% PPI - 524 μm 10% PPI - 490 μm 15% PPI - 421 μm
12 10 8 6 4 2 0
3360 2360 1700 1180 850
600
420
297
212
150
103
73
53
37
Size of sieve opening (µm) Figure 1. Particle size distribution of diets. PPI = Pea protein isolates. GMD = Geometric mean diameter is the average particle size expressed microns (μ m).
of gizzard quadratically declined (P = 0.002) such that the gizzard weight decreased when the dietary level of PPI was increased from 0 to 15%. Weights of small and large intestine showed both linear (P < 0.05) and quadratic (P < 0.05) reduction with an increase in the dietary inclusion of PPI. However, a significant reduction in weights of small and large intestine was observed only with a dietary inclusion level of 10 and 15% PPI. There was no effect of dietary treatment on liver weight. An increase in the dietary level of PPI from 0 to 15% resulted in a quadratic reduction (P < 0.05) in ATTR
of DM and CP with ATTR of GE showing a tendency for reduction (quadratic P = 0.053) with increasing inclusion levels of PPI (Table 5). The AID values of AA in diets with graded levels of PPI are presented in Table 5. Among the indispensable AA, only AID of His showed a quadratic reduction (P = 0.008) with increasing dietary inclusion of PPI. However, the level of PPI inclusion (5, 10, and 15%) did not have any effect on AID of His. Also, a tendency for reduction in AID was observed for Leu (P = 0.087) and Phe (P = 0.065) with increasing inclusion levels of PPI. Among dispensable AA, AID of
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Item
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PEA PROTEIN ISOLATES FOR BROILERS Table 3. Effect of graded levels of pea protein isolates (PPI) in diets on growth performance of broilers from hatch to 21 d of age.1 Dietary PPI inclusion level, %
Body weight, g Initial (day 0) Final (day 21) Body weight gain, g
0
5
10
15
SEM
Linear
Quadratic
46.0 704.2a
45.6 700.2a
46.2 659.7a
45.2 607.5b
0.37 16.66
0.277 < 0.001
0.439 0.159
Week 1 Week 2 Week 3 Overall Feed Intake, g
103.4a 267.9a 286.9 658.2a
105.6a 244.2b 304.8 654.6a
107.7a 238.4b 267.4 613.6a
85.7b 206.7c 270.0 562.4b
3.99 8.07 14.68 16.60
0.008 < 0.001 0.192 < 0.001
0.005 0.619 0.605 0.162
Week 1 Week 2 Week 3 Overall Feed conversion ratio
121.1b 315.7a 406.6a,b 843.3a
129.5a,b 301.7a,b 416.1a 847.3a
139.1a 290.3b 376.5a,b 805.8a
118.2b 260.2c 370.9b 749.2b
4.14 6.09 13.98 17.15
0.162 < 0.001 0.026 0.002
0.002 0.197 0.590 0.089
0.004 0.068 0.389 0.013
0.730 0.706 0.617 0.929
Week 1 Week 2 Week 3 Overall
1.18b 1.18b 1.45 1.28b
1.23b 1.25a,b 1.37 1.30a,b
1.30a,b 1.22a,b 1.42 1.32a,b
1.38a 1.27a 1.38 1.33a
0.047 0.026 0.037 0.014
Means in the same row with different superscripts differ (P ≤ 0.05). Growth performance data are means of 8 pens of broilers with 6 broilers per pen.
a–c 1
Table 4. Effect of graded levels of pea protein isolates (PPI) in diets on organ weights of broilers from hatch to 21 d of age.1 Dietary PPI inclusion level, % Item
0
Organ weights, mg/g of BW Liver 30.9 Spleen 0.85a Proventriculus 6.1a Gizzard 19.9a Small intestine 34.8a Large intestine 8.5a
P-Value
5
10
15
SEM
linear
Quadratic
32.9 0.75a,b 5.9a 17.8b 32.7a 7.9a
28.7 0.68b 4.7b 17.7b 26.1b 5.8b
33.8 0.89a 5.8a 15.8c 29.3b 6.7b
1.29 0.05 0.20 0.64 1.41 0.32
0.421 0.748 0.023 0.123 0.008 < 0.001
0.219 0.005 0.005 0.002 0.012 0.029
Means in the same row with different superscripts differ (P ≤ 0.05). Organ weight data are means of 8 pens of broilers with 3 broilers per pen.
a–c 1
Asp, Glu, Gly, and Ser showed a quadratic reduction (P < 0.05) and AID of Tyr showed a linear reduction (P = 0.031) with increasing dietary inclusion of PPI. The AID of Cys and Pro showed both linear (P < 0.05) and quadratic (P < 0.05) reduction with increasing dietary inclusion of PPI. However, the level of inclusion of PPI (5, 10, and 15%) showed no effect AID values for dispensable AA.
DISCUSSION The protein content (78.4%) for the PPI used in the current study was comparable to the value for PPI that was used in our previous study (84.9%; Nandha et al., 2013). Moreover, the PPI used in the present study had a comparable CP values to soy protein isolates (86.2%; Chen et al., 2015). A 15% dietary inclusion of PPI in the current study resulted in reduced BW gain. The reduced BW gain as a result of increased dietary inclusion level of PPI could partly be attributed to reduced feed intake in birds.
Furthermore, this reduction in feed intake at a high inclusion level of PPI could be because of the extremely fine feed particles due to the presence of PPI as shown in Figure 1. Chewning et al. (2012) reported a similar reduction in feed intake in broilers fed diets containing finely ground corn, thus resulting in a lower BW gain. Similar effects of feed particle size were also reported with feed ingredients like wheat and sorghum, wherein broilers fed diets containing coarser particles had a better BW gain and feed efficiency when compared to those fed fine particle mash diets (Nir et al., 1995; Amerah et al., 2007). Moreover, uniformity of the feed particle size is another factor that influences feed intake in birds. Birds can differentiate feed particle size with the help of mechanoreceptors in the beak (Amerah et al., 2007) and birds of all ages have shown to prefer larger feed particles in the diet (Schiffman, 1968; Portella et al., 1988). However, when diets containing uniform particle size are fed, birds spend less time searching for larger particles (Amerah et al., 2007) and thereby increases the feed intake. The diets used in the current study
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P-Value
6
VELAYUDHAN ET AL. Table 5. Effect of graded levels of pea protein isolates (PPI) in diets on apparent total tract retention (ATTR) of gross energy (GE) and protein, and apparent ileal digestibility (AID) of amino acids (AA) in broilers. Dietary PPI inclusion level, % 0
5
10
15
SEM
linear
Quadratic
69.8a 61.2a 72.9
65.1a,b 57.3a,b 74.6
63.6b 53.1b 70.7
61.9b 53.3b 70.9
2.21 2.62 1.65
0.117 0.315 0.440
0.039 0.029 0.053
79.8 54.3a 72.4 74.2 75.8 82.6 79.5 65.0 69.1
75.8 47.1a,b 67.6 73.2 73.2 86.1 73.5 65.2 64.6
70.7 42.6b 64.9 68.0 68.0 83.7 71.0 61.5 60.5
76.5 43.2b 65.4 67.0 67.9 85.5 70.9 62.3 62.3
3.65 2.74 3.69 3.50 4.09 2.03 2.89 3.14 3.26
0.295 0.084 0.377 0.904 0.674 0.344 0.176 0.992 0.304
0.251 0.008 0.198 0.087 0.119 0.901 0.065 0.311 0.104
63.1 67.4a 74.5a 78.8a 65.2a 75.9a 66.7 76.8a
64.9 62.7a,b 53.6b 72.8a,b 58.6a,b 65.9b 64.1 66.5b
62.1 59.4b 50.9b 68.1b 57.5b 63.4b 59.4 65.6b
61.9 59.8b 50.1b 68.8b 54.6b 64.9b 61.6 67.9b
3.46 2.72 3.19 3.17 2.37 3.18 2.99 3.28
0.579 0.492 0.001 0.193 0.121 0.034 0.461 0.031
0.483 0.025 0.001 0.028 0.021 0.042 0.100 0.147
ATTR, % DM CP GE AID, % Indispensable AA Arg His Ile Leu Lys Met Phe Thr Val Dispensable AA Ala Asp Cys Glu Gly Pro Ser Tyr a–c
Means in the same row with different superscripts differ (P ≤ 0.05).
had moderately ground corn-soybean meal with very fine particle sized PPI, and this dissimilarity in particle size could be one reason for a lower feed intake by birds fed high PPI containing diets. When compared to similar protein sources like the soy protein isolates, growth performance of broiler chicken in the present study has shown comparable results. Chen et al. (2015) in a 21-d study reported similar BW gain (524 g/bird) and daily feed intake (814 g/bird) in birds fed a corn-based diet with 16.5% soy protein isolates when compared to those fed 15% PPI in the current study. Also, Jankowski et al. (2009) have reported a significant reduction in BW gain in turkeys when fed diets containing soy protein isolates (19.5%) compared to those fed a wheat-soybean meal based control diet. Yet another reason for a reduced BW gain in birds fed 15% PPI could be because of a lower level of dietary fat. Since all the diets contained similar levels of energy and protein, the reduced performance in birds with low dietary fat suggests that energy from fat is more efficiently utilized than that from other ingredients as observed in previous studies (Atteh et al., 1983; Nitsan et al., 1997; Peebles et al., 2000). On the contrary, few studies also observed no difference on dietary fat inclusion levels on growth performance in broilers (Anderotti et al., 2004; Rezaeipour et al., 2016). Digestibility of fats is lower in young birds and found to increases with age (Nitsan et al., 1997). Henceforth, at an early age in birds with low-fat digestibility, the benefits of dietary fat supplementing are not always consistent (Wiseman and Salvador, 1991; Nitsan et al., 1997).
Development of various sections of the gastrointestinal tract in birds has been shown to be influenced by the feed particle size. The muscular stomach or the gizzard in birds helps in the reduction of the particle size of ingested feed and mixes them with digestive enzymes. Larger feed particles in the diet have shown to have a stimulatory effect on the gizzard, resulting in increased size of the gizzard (Jacobs et al., 2010). Hence when fed fine particle size diets, the gizzard is relatively underdeveloped (Taylor and Jones, 2004) as evident in the current study wherein birds fed PPI containing diets had a lower a gizzard weight. This reduction in the gizzard weight could probably be due to the lack of mechanical stimulation by the feed because of the presence of fine particle sized PPI. Likewise, studies have shown small intestinal hypertrophy when fed fine particle size mash diets (Nir et al., 1994) and a lower relative duodenal weight in birds fed coarse particle diets compared to those fed fine particle diets (Nir et al., 1995; Gabriel et al., 2003). However, such observations were not found in the current study, the reasons for which are unclear. Larger particle size in the diets also results in a longer residence time within the stomach since coarser particles are retained in the gastrointestinal tract for a longer duration when compared to fine particles (Nir et al., 1994; Amerah et al., 2007). Moreover, a slower passage rate may better facilitate the mixing of feed with digestive enzymes (Qaisrani et al., 2014), thereby improving the digestibility of nutrients. The reduction in the ATTR of nutrients in the current study with increasing
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P-Value
PEA PROTEIN ISOLATES FOR BROILERS
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inclusion of PPI could be attributed to the increase in the digesta passage rate because of finely ground PPI in diets. Pea protein isolates are refined protein fractions derived using wet processing technique (Vose et al. 1976; Owusu-Ansah and McCurdy, 1991) and are considered to contain only marginal levels of anti-nutritive factors (Nandha et al., 2013). The relatively low levels of antinutritive factors explain the reason for a higher AID of AA in PPI when compared to those observed for whole peas (Bandegan et al., 2011) and pea protein concentrates (Valencia et al., 2009) fed to broilers. However, Fern´ andez-Quintela et al. (1997) have reported around 50% trypsin inhibitor activity and phytate levels retained in PPIs after processing when compared to the pea seeds. The presence of these anti-nutritive factors could be among the probable reasons for the lower AA digestibility at higher PPI inclusion rate (15%) in the current study. In conclusion, increasing inclusion of PPI in broiler chick diets showed a linear reduction in growth performance of birds, with a negative impact on ATTR of nutrients and AID of most of the dispensable AA. However, based on the results from the current study it is not possible to determine an optimum inclusion level for PPI in broilers. Hence, this warrants more investigations into the mechanisms underlying the negative effects of PPI inclusion on growth performance and nutrient digestibility in broilers.
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