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Tuesday, March 01, 2016 4:57:51 PM
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Evaluation of soybean meal source and particle size on broiler performance, nutrient digestibility, and gizzard development

 

W. J. Pacheco et al., Prestage Department of Poultry Science, North Carolina State University

 


ABSTRACT

 
Although there have been several reports concerning the effects of particle size of cereal grains on productive performance of poultry, there is limited information about the effects of soybean meal (SBM) particle size on broiler performance. The objective of the present experiments was to evaluate the effects of SBM source and particle size on broiler performance, gizzard weight, and nutrient digestibility. The first experiment was a 2 × 2 factorial arrangement of 2 SBM sources: expeller-extracted (ESBM) and solvent-extracted (SSBM), and 2 particle sizes: coarse grind, 971μm, and fine grind, 465 μm. The second experiment was a 2 × 2 factorial arrangement of 2 ESBM particle sizes: coarse grind, 1,290 μm, and fine grind, 470 μm, and 2 corn particle sizes: coarse grind, 1,330 μm, and fine grind, 520 μm. In the first experiment, there was an interaction (P < 0.05) between SBM source and particle size on BW at 49 d of age. No differences in BW were observed when birds were fed coarse SSBM or ESBM, whereas birds fed diets containing fine ESBM exhibited lower BW than birds fed diets containing fine SSBM. In the second experiment, fine-grind ESBM (P < 0.05) and corn (P < 0.01) produced greater 19-d BW than did coarse grind. A significant interaction (P < 0.01) between ingredient type and particle size revealed that chicks fed coarse particles of corn or ESBM exhibited higher protein digestibility compared with chicks fed only fine particles. Corn particle size had a greater effect on gizzard weight than ESBM particle size. Birds fed diets that contained coarse corn had larger gizzards than birds fed fine corn (P < 0.01), but differences in gizzard weight were not observed when birds were fed coarse or fine ESBM. Particles greater than 1,300 μm depressed BW but improved protein digestibility.

 

INTRODUCTION

 

Soybean meal (SBM) is a coproduct that remains after the oil is extracted from whole soybeans, either by solvent extraction (SSBM) or mechanically by using an extrusion-expeller (ESBM) process. Solvent extraction has been most widely used to process soybeans, as it has been the most efficient method to extract the oil and reduce heat-labile antinutritional factors, such as trypsin inhibitors. However, solvent extraction has required a considerable capital investment, has had high energy consumption, and has required a consistent supply of soybeans to operate continuously throughout the year. The expeller-extrusion process has become an alternative approach because it can be designed for a small-scale operation. Some advantages of the expeller- extrusion process include low capital investment, relatively simple extraction equipment, and the ability to use organic soybeans to produce specialty organic SBM. Additionally, the process can be used to process identity preserved SBM due to its ability to rapidly change soybean sources with minimal cross contamination (Wang et al., 2001).

 

The increase in the price of cereal grains, protein meals, and other feed ingredients used in animal feeds has forced the animal feed industry to evaluate alternative ingredients and processing methods in an effort to improve feed efficiency and reduce production costs. Particle size has been reported to influence many aspects of poultry production, including nutrient utilization, growth performance, digestive tract development, and feed passage rate (Gabriel et al., 2003; Amerah et al., 2007, 2008). Although there has been extensive information developed concerning the feeding value of ESBM in swine diets (Woodworth et al., 2001; Webster et al., 2003; Opapeju et al., 2006), there have been few studies that evaluated the feeding value of ESBM for poultry. The objective of the present studies was to evaluate the effect of SBM type and particle size of corn and ESBM on broiler live performance, relative gizzard weight, and nutrient digestibility.

 

Table 1.  Composition and calculated contents of the experimental diets in experiment 1 (as-fed basis)1
 

 

1SSBM = soybean meal from solvent extraction; ESBM = soybean meal from extrusion-expeller process.

2Vitamin premix provided the following per kilogram of diet: vitamin A, 6,600 IU; cholecalciferol, 1.980 IU; niacin, 55 mg; α-tocopherol, 33 mg; pantothenic acid, 11 mg; riboflavin, 6.6 mg; pyridoxine, 4 mg; menadione, 2 mg; folic acid, 1.1 mg; thiamine, 2 mg; vitamin B12, 0.02 mg; and biotin, 0.13 mg.

3Mineral premix provided the following per kilogram of diet: Zn, 120 mg; Mn, 120 mg; Fe, 80 mg; Cu, 10 mg; I, 2.5 mg; Co, 1.0 mg.

4Selenium premix provided 0.2 mg/kg of Se.

5Monensin was included at 99 mg/kg (Coban 90, Elanco Animal Health, Indianapolis, IN).

 

MATERIALS AND METHODS

 

Diets, Housing, and Management

 

Diets were formulated to meet or exceed NRC requirements (NRC, 1994) and were composed mainly of corn, SBM, and poultry by-product meal (Table 1). Dietary amino acids were formulated on a digestible basis with diets formulated to a minimum digestible amino acid level. The coarse SSBM and ESBM were added to the diets as received from the supplier, and the fine SSBM and ESBM were obtained by grinding the coarse material in a hammermill. In the second experiment, fine ESBM and corn were obtained by grinding the whole corn and ESBM using a rollermill to obtain a better particle size distribution of the corn and ESBM and reduce the levels of fines (Figure 1). The starter diet (Table 2) contained 0.5% titanium dioxide, which was used as an indigestible marker for nutrient digestibility determination.

 

The care of the animals used in these trials conformed to the Guide for Care and Use of Animals in Agricultural Research and Teaching (FASS, 2010). In the first experiment, 1,024 one-day-old male Heritage (Perdue Farms, Salisbury, MD) broiler chicks were hatched at the research site and reared in a curtain-sided broiler house until 49 d of age. There were 32 chicks placed per pen with 32 pens in total. Each pen was assigned to 1 of 4 dietary treatments with 8 replicates per treatment. The birds were raised on used litter that was top-dressed with new wood shavings with ad libitum access to feed and water. Feeders were shaken once per day from 1 to 14 d and twice per day from 15 to 49 d to prevent variation in feed intake due to feed flow characteristics. The lighting program began with 23 h of light from 1 to 7 d, 22 h of light to 14 d, 20 h of light to 21 d, and natural light from 22 to 49 d of age. The house temperature was maintained between 32 and 34°C from placement to 7 d, 29°C to 14 d, 27°C to 21 d, and ambient thereafter. Chicks were fed 0.9 kg of starter feed/ chick, 3.2 kg of grower feed/chick, and 3.6 kg of finisher feed/chick.

 

The second experiment used 256 male Ross 344 × 708 broiler chicks (Aviagen, Huntsville, AL) that were hatched at the research site and placed in 4 Petersime batteries with electric brooders and wire mesh floors, and housed in an environmentally controlled room. Each battery had 12 cages distributed over 6 decks. Seven chicks were placed in each cage using the 8 cages of the 4 middle decks of each battery. Each cage was randomly assigned to 1 of the 4 dietary treatments with 8 replicates per treatment. Feed and water were provided for ad libitum consumption. Feed spills were collected at the bottom of each battery and added back to the feeder. The lighting program consisted of 23 h of artificial light per day throughout the 21-d experimental period. The room temperature was maintained at 32°C from 1 to 3 d, 31°C from 4 to 7 d, and 29°C from 8 to 21 d. Chicks were fed 1.4 kg of starter feed/chick in mash form from 1 to 21 d of age.

 

 

Figure 1.  Particle size distribution of the coarse and fine corn and coarse and fine expeller-extracted soybean meal (ESBM) used in experiment 2.

 

Table 2.  Composition and calculated contents of the experimental diets in experiment 2 (as-fed basis)

 

1ESBM = expeller-extracted soybean meal.

2Vitamin premix provided the following per kilogram of diet: vitamin A, 6,600 IU; cholecalciferol, 1.980 IU; niacin, 55 mg; α-tocopherol, 33 mg; pantothenic acid, 11 mg; riboflavin, 6.6 mg; pyridoxine, 4 mg; menadione, 2 mg; folic acid, 1.1 mg; thiamine, 2 mg; vitamin B12, 0.02 mg; and biotin, 0.13 mg.

3Mineral premix provided the following per kilogram of diet: Zn, 120 mg; Mn, 120 mg; Fe, 80 mg; Cu, 10 mg; I, 2.5 mg; Co, 1.0 mg. 4Selenium premix provided 0.2 mg/kg of Se. 5Monensin was included at 99 mg/kg (Coban 90, Elanco Animal Health, Indianapolis, IN).

 

Data Collection

 

In the first experiment initial chick BW was recorded on a pen basis. Feed consumption and BW by pen were subsequently recorded at 14, 35, and 49 d of age, which approximated the feeding periods of the starter, grower, and finisher diets. Mortality was removed, weighed, and recorded twice daily. Feed conversion ratio (FCR) was adjusted by adding the weight of the dead birds to the weight of the live birds in each pen.

 

Experiment 2, initial chick BW was recorded on a cage basis. Feed consumption and BW by cage were then recorded at 7 and 19 d of age. At 16 d of age, clean paper was placed under each cage and feces were collected for 3 consecutive days. Every 24 h, a sample of feces (free of feed, feathers, and other contaminants) was collected. At 21 d of age, ileal digesta was collected (2 cm posterior of Meckel’s diverticulum to 2 cm anterior of the ileal-cecal junction) by gently squeezing the ileal contents in a manner that provided sufficient sample for digestibility analysis. The gizzard was excised, contents removed, rinsed, and blotted dry. The gizzard was weighed and expressed as a percentage of BW.

 

Laboratory Analyses

 

Dry sieving according to ASAE method S319.3 (ASABE, 2007) was used to determine the particle size of corn and SBM with the addition of sieve agitators and 0.5 g of dispersing agent per 100 g of sample. Soybean meal was analyzed for gross energy (Merrill and Watt, 1973), trypsin inhibitors (Hamerstrand et al., 1981), as well as ether extract (method 920.39), CP (N × 6.25; method 990.03), and crude fiber (method 962.09; AOAC International, 2006). Proximate values were used to calculate the ME content of the ESBM and SSBM (Janssen et al., 1979) before diet formulation. Additionally, in the second experiment samples of feed and feces were analyzed for gross energy (Merrill and Watt, 1973), moisture (method 934.01), CP (N × 6.25; method 990.03), ether extract after HCl hydrolysis (method 954.02; AOAC International, 2006), and titanium dioxide (Myers et al., 2004). Titanium dioxide analyses were used to calculate ileal protein and fat digestibility (Fan et al., 1994; Marty et al., 1994).

 

Statistical Analyses

 

Experiments were analyzed as a 2 × 2 factorial randomized complete block design to identify main effects and interactions. The first experiment used 2 SBM types (SSBM and ESBM) and 2 SBM particle sizes (coarse and fine), whereas the second experiment used 2 ESBM particle sizes (coarse and fine) and 2 corn particle sizes (coarse and fine). Pen and cage served as the experimental units for the statistical analysis of the live performance data. Data were analyzed using PROC GLM (SAS, 2006). Statements of statistical differences were based upon P < 0.05 unless otherwise indicated. Differences between means were separated by the least significant difference test.

 

RESULTS AND DISCUSSION

 

Experiment 1

 

The geometric mean diameter of the particle size was 971 and 465 μm for the coarse and fine SSBM and 1,080 and 352 μm for the coarse and fine ESBM, respectively. Moisture, CP, and crude fat were 12.0, 47.4, and 1.4% in SSBM and 11.8, 40.7, and 7.2% in ESBM, respectively. The trypsin inhibitor levels were 22.1 TIU/mg for the ESBM and 3.8 TIU/mg for the SSBM.

 

The main effects of SBM type and particle size on BW, feed intake, and FCR are shown in Table 3. The SSBM increased BW at 14 (P < 0.01), 35 (P < 0.01), and 49 d of age (P < 0.05) compared with ESBM. The higher BW observed in the SSBM treatments was mainly explained by a greater feed intake. The inclusion of SSBM increased feed intake at 14 (P < 0.01), 35 (P < 0.01), and 49 d of age (P < 0.01) compared with ESBM. Particle size had an effect on BW with birds fed coarse SBM exhibiting higher BW at 35 (P < 0.01) and 49 d of age (P < 0.01) compared with birds fed fine SBM. Although birds fed the fine SBM exhibited greater feed intake at 14 (P < 0.05) and 35 d (P < 0.05), no differences were observed at 49 d of age. Chicks fed ESBM exhibited poorer FCR at 14 d (P < 0.01), but improved FCR at 35 (P < 0.01) and 49 d of age (P < 0.01) than chicks fed SSBM. The poorer FCR observed at 14 d of age in diets that contained ESBM could have been because intestinal motility, pancreatic enzyme secretion, and bile salt synthesis have been reported to be only partially developed at hatching (Buddington and Diamond, 1989; Buddington, 1992); therefore, young birds were probably more affected by high levels of trypsin inhibitors in the ESBM. The differences in FCR observed at 35 and 49 d of age were attributed to the higher than expected percentage crude fat present in the ESBM. Initially, the ESBM was analyzed using only the ether extraction method, which did not accurately estimate the fat content; therefore, acid hydrolysis should be performed before ether extraction to obtain a more accurate estimate of fat content, particularly in the ESBM. The addition of coarse SBM in the diets improved FCR at 14 (P < 0.01), 35 (P < 0.01), and 49 d of age (P < 0.01) compared with birds fed fine SBM. Many studies have demonstrated the positive influence of large particles on nutrient and mineral retention during digestion. Reece et al. (1985) and Nir et al. (1995) reported that broilers fed diets with coarse particles of wheat, sorghum, and corn exhibited higher BW and improved feed efficiency compared with broilers fed finely ground grains. In addition, Gabriel et al. (2003) reported that large feed particles increased gizzard functionality, enhanced pepsin chemical activity in the proventriculus, lowered the pH of the gizzard contents, and improved protein digestion. Some authors have also reported improvements in mineral absorption and retention with larger particle feed ingredients. Kilburn and Edwards (2004) reported that increasing the particle size of commercial SBM from 891 to 1,239 μm improved mineral utilization and feed efficiency in semipurified diets.

 

There were significant interactions between SBM type and particle size on BW at 14 (P < 0.01), 35 (P < 0.01), and 49 d of age (P < 0.05). Chicks feed coarse ESBM exhibited greater BW at 14 (P < 0.01), 35 (P < 0.01), and 49 d of age (P < 0.05) compared with chicks feed fine ESBM. However, chicks fed fine SSBM had greater BW at 14 d (P < 0.01) compared with chicks fed coarse SSBM, but this effect was not present at 35 and 49 d of age. At 49 d of age, no significant differences in BW were found among birds fed coarse SSBM or ESBM. In contrast, birds fed fine ESBM exhibited lower BW than birds fed fine SSBM (P < 0.01). Generally speaking, the fine-ESBM combination produced the lowest BW at 14, 35, and 49 d of age. These results suggested that the larger particle size ESBM, probably as a result of greater gizzard activity, may have ameliorated the adverse effects of high levels of trypsin inhibitor that were present in the ESBM. There was a significant interaction (P < 0.01) for cumulative feed intake between SBM type and particle size at 14, 35, and 49 d of age. At 49 d of age, birds fed the fine-SSBM combination consumed more feed than the coarse-ESBM and fine-ESBM groups. The feed consumption of the diet containing coarse-SSBM was intermediate. There was a significant interaction (P < 0.05) between SBM type and particle size on FCR at 35 d of age. There were no significant differences in FCR observed among birds fed coarse or fine ESBM, whereas birds fed coarse SSBM exhibited improved FCR compared with birds fed fine SSBM (P < 0.01). The poorer FCR observed in diets containing fine-SSBM could be due to decreased gut peristalsis that increased feed passage rate and subsequently increased feed consumption. Indeed, at 35 d of age broilers fed fine-SSBM exhibited greater feed intake compared with the broilers consuming the other diets. No other interactions concerning FCR were observed.

 

 
 

Figure 2.  Particle size distribution of the diets manufactured using the combination of coarse corn (CC), fine corn (FC), coarse expellerextracted soybean meal (CE), and fine expeller-extracted soybean meal (FE) in experiment 2.

 

 

Experiment 2

 

The geometric mean diameter of the particle size was 1,290 and 470 μm for the coarse and fine ESBM at 1,330 and 520 μm for the coarse and fine corn (Figure 1). In addition, the geometric mean diameter of the particle size of the diets was 1,217 μm for coarse ESBM and coarse corn, 900 μm for coarse ESBM and fine corn, 818 μm for fine ESBM and coarse corn, and 630 μm for fine ESBM and fine corn (Figure 2).

 

There were no significant particle size interactions for broiler live performance at 7 and 19 d of age (Table 4). Coarse particle size ESBM decreased BW at 7 (P < 0.01) and 19 d of age (P < 0.05), but no differences in BWG were observed between 7 and 19 d of age due to ESBM particle size. The lower BW observed was related to reduced feed intake at 7 (P < 0.01) and 19 d of age (P < 0.01), and by poorer FCR at 7 d of age (P < 0.01). Coarse particle size corn reduced BW at 7 (P < 0.01) and 19 d of age (P < 0.01) due to reduced feed intake at 7 (P < 0.01) and 19 d of age (P < 0.01). In a similar manner, FCR was poorer at 7 (P < 0.01) and 19 d of age (P < 0.01) due to coarse particle size corn. Generally speaking, with respect to both main effects, diets that resulted in greater feed consumption produced greater BW. Indeed, particle size of the corn and ESBM did not affect FCR between 7 and 19 d of age. Charbeneau and Roberson (2004) reported a significant decrease in BW gain at 7 and 15 d when the particle size of the corn in a diet was increased from 606 to 1,094 μm. Moreover, Jacobs et al. (2010) reported a linear decrease in BW gain (0 to 21 d) and poorer feed efficiency (0 to 7 d) when the particle size of the corn was increased from 557 to 1,387 μm. They suggested that the gizzard of very young chicks was not developed sufficiently to grind large particles. In contrast, Parsons et al. (2006) reported that increasing corn particle size from 781 to 2,242 μm resulted in greater feed intake, improved feed efficiency, and increased nitrogen retention in broilers fed pelleted diets from 3 to 6 wk of age.

 

The effect of ESBM and corn particle size on fat and protein digestibility, and relative gizzard weight is detailed in Table 5. Coarse particle size ESBM exhibited greater protein digestibility at 21 d of age (P < 0.01), whereas coarse particle size corn produced a greater relative gizzard weight at 21 d of age (P < 0.01). Protein digestibility of the fine ESBM-fine corn diet was poorer than the remaining 3 combinations (P < 0.01).
 

 

Table 5.  Effect of expeller-extracted soybean meal (ESBM) and corn particle size on fat and protein digestibility, and relative gizzard weight of broilers at 21 d of age in experiment 21

 

 

The addition of coarse particles to the diet may have increased gastric reflux exposing the feed to pepsin digestion in the proventriculus and pancreatic proteases in the upper part of the small intestine (Gabriel et al., 2003). Gizzard weight was greater in the coarse ESBMcoarse corn and fine ESBM-coarse corn combinations, which suggested that corn particle size had a greater influence on gizzard size than did ESBM particle size. Charbeneau and Roberson (2004) and Jacobs et al. (2010) reported an increase in gizzard weight as particle size of dietary corn increased. Moreover, Nir et al. (1994) reported that when 1-d-old chicks were fed coarse and medium size corn particles, gizzard weight increased by 26 and 41%, respectively, compared with chicks fed fine particles.

 

The results of the present studies indicated that SBM type (SSBM and ESBM) and particle size of ESBM and corn influenced broiler performance, nutrient digestibility, and gizzard weight. The first experiment showed that ESBM has the potential to replace SSBMin broiler diets, particularly when offered in a coarse texture because it appears to assist the chicks in counteracting the negative effect of high levels of trypsin inhibitors. In spite of the benefits such as better ileal protein digestibility and better gizzard development from feeding coarse particles observed in the second experiment, particle size distribution must also be taken into consideration when feeding young chickens because particles that are too large (>1,300 μm) may be difficult to consume and may require greater energy to be ground in the gizzard, which may leave less energy available for productive growth.

  
        

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Article made possible through the contribution of W. J. Pacheco et al., Prestage Department of Poultry Science, North Carolina State University

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