Determining Amino Acid Digestibility of Soybean Meal from South Determining Amino Acid Digestibility of Soybean Meal from South Carolina Soybean Varieties Fed to Broilers Carolina Soybean Varieties Fed to Broilers

Summary At hatch, 240 male broilers (Ross 308, Aviagen, Sallisaw, OK) were placed in batteries (Petersime Brood Unit, Gettysburg, OH) for a 15-d study to evaluate amino acid digestibility of soybean meal (SBM) from specialty variety soybeans grown in South Carolina. There were 10 replicates per treatment and 6 broilers per cage. Broilers were given a common corn and soybean meal-based diet from d 0 to 9. On d 9, broilers were weighed, and cages were allotted to 1 of 4 dietary treatments within location block. Dietary treatments consisted of 1 of 4 soybean sources varying in quality determined by crude protein (CP) content and processed into SBM. Two sources consisted of soybeans from a similar region and processed either commercially solvent extracted or experimentally solvent extracted at Texas A&M University. Therefore, dietary treatments consisted of a commercially processed SBM with 44% CP (CON) or experimentally processed SBM with 50% CP (PCON), 52% CP (52SBM), or 56% CP (56SBM). Assay diets were dextrose and SBM-based, formulated to supply 20% dietary CP with titanium dioxide as an indigestible marker. On d 15, broilers were euthanized by CO 2 inhalation and ileal samples were collected for determination of apparent ileal digestibility (AID) of AA. Data were analyzed using the GLIMMIX procedure in SAS v. 9.4 (SAS Institute Inc., Cary, NC), with pen as the experimental unit, pen location as the blocking factor and adjusted using Tukey-Kramer multiple comparisons. Broilers fed CON and 56SBM had increased ( P < 0.003) digestibility of total AA, Arg, His, Lys, Thr, and Trp


Introduction
Soybean meal (SBM) is the primary protein source used in broiler diets.Recent developments in soybean selection programs have led to increasing protein content of soybeans; therefore, leading to increased CP and AA concentrations of SBM.Determining SBM value can provide opportunity for cost savings through precision diet formulation.One of the main attributes of SBM quality is defined by CP content and AA availability for growth.While traditionally SBM has 46% CP, the opportunity for higher CP and AA content can increase SBM value ultimately decreasing diet inclusion and lowering diet costs.Therefore, it is essential to focus on optimizing SBM quality to improve the economics of poultry production.Selecting for soybean varieties that lead to increased available AA concentrations in SBM will provide an improvement in the feeding value of SBM.Therefore, the objective of this study was to determine the apparent ileal digestibility of AA for select varieties of SBM varying in CP content when fed to broilers.

Materials and Methods
The Kansas State University Institutional Animal Care and Use Committee approved the protocol used in this experiment.A total of 240 one-day-old male broilers (Ross 308, Aviagen, Sallisaw, OK) were obtained and transported to the Kansas State University Poultry Facility (Manhattan, KS) to be used in a 15-d digestibility study.Broilers were placed in 2 Petersime batteries (Petersime Brood Unit, Gettysburg, OH) with 6 broilers per cage (dimensions, 38.0 × 13.0 in.), balanced by BW and provided a common corn, SBM diet.On d 9, cages were randomly assigned to 1 of 4 dietary treatments within location block and balanced by BW with 10 replicates per treatment.Broilers were maintained on a 24-hr lighting schedule in a thermostatically controlled room.Illumination was provided by fluorescent bulbs for the duration of the experiment.A HOBOware data logger was used to record temperature, relative humidity, and light intensity of the battery room.For the first 9-d, averages were 76.6°F, 53.5%, and 11.4 lum/ft 2 , followed by 73.9°F, 51.2% and 11.4 lum/ft 2 for the remainder of the experiment for temperature, relative humidity, and light intensity, respectively.Feed was provided ad libitum in a 1-pan feeder (capacity approximately 4.4 lb) per pen.Water was provided ad libitum through water troughs.Broilers were weighed on day 0, 9, and 15 for allotment to treatment and final BW.Mortalities were recorded daily.

Dietary treatments
Dietary treatments consisted of 1 of 4 soybean sources varying in quality determined by CP content and processed into SBM.Two sources consisted of soybeans from a similar region and processed either commercially solvent extracted or experimentally solvent extracted at Texas A&M University.Therefore, dietary treatments consisted of a commercially processed SBM with 44% CP (CON) or experimentally processed SBM with 50% CP (PCON), 52% CP (52SBM), or 56% CP (56SBM).Assay diets were dextrose and SBM-based and formulated to supply 20% dietary CP with titanium dioxide as an indigestible marker.

Ileal collection
On d 15, broilers were euthanized by CO 2 inhalation and ileal samples were collected for AA analysis.Ileal contents were collected beginning 0.4-in.posterior to the Meckel's diverticulum and ending 0.4-in.prior to the ileocecal junction.Ileal samples were collected and pooled by pen.Composite samples were stored at -4°F prior to lyophilization (University of Illinois, Champaign, IL).Samples were finely ground to pass through a 0.02-in.screen and sent to the University of Missouri Agricultural Experiment Station (Columbia, MO) for analysis.

Chemical analysis
Individual soybean meal and diet samples were analyzed for proximate analysis and complete AA profile, 2 and available Lys 3 (Table 1).Diets and ileal samples were analyzed for titanium dioxide 4 as an indigestible marker (Table 3).Ileal contents were analyzed for dry matter and complete AA profile 2 for determination of apparent ileal digestibility (AID) of AA.

Calculations and statistical analysis
Apparent ileal digestibility of AID was calculated using the following equation 5 : where AA digesta and AA diet represent the AA concentrations (g/kg) in digesta and diet DM, respectively; and TiO 2, diet and TiO 2, digesta represent the digestible marker concentrations (g/kg) in diet and digesta DM, respectively (Table 4).
Data were analyzed using the PROC-GLIMMIX procedure of SAS (v.9.4, SAS Institute, Inc., Cary, NC) with cage serving as the experimental unit.Results were considered significant at P ≤ 0.05.

Results and Discussion
Individual soybean meal samples contained 44.8, 50.1, 52.4, and 56.1% CP, and 2.90, 3.05, 3.11, and 3.47% Lys in the CON, PCON, 52SBM, and 56SBM, respectively (Table 1).The PCON was sourced from the same geographical region as the CON, therefore it was expected these would be similar in CP content.The PCON, 52SBM, and 56SBM were processed into SBM on a pilot scale crush facility at Texas A&M University.These samples had increased DM compared to the CON.Therefore, the CON and PCON had similar CP and Lys when expressed on a DM basis.Individual SBM samples contained 2.79, 2.80, 2.90, and 3.24% available Lys and 0.6, 0.5, 2.1, and 1.1 crude fat in the CON, PCON, 52SBM, and 56SBM, respectively.High CP soybean samples had lower crude fiber where crude fiber was 5.2, 4.9, 4.7, and 4.3 in CON, PCON, 52SBM and 56SBM, respectively.Starch was greatest in CON (3.09%) followed by PCON (1.17%), 56SBM (0.19%), and 52SBM (0.12%).Broilers fed CON and 56SBM had increased (P < 0.003) AID of total AA, Arg, His, Lys, Thr, and Trp compared to those fed PCON and 52SBM (Table 3).The AID of Ile and Phe increased (P < 0.001) in broilers fed 56SBM compared to CON and 52SBM, while PCON was intermediate to CON and 52SBM.Broilers fed 56SBM had increased (P < 0.001) AID of Leu compared to all other sources.The AID of Met increased (P = 0.007) in broilers fed CON and 56SBM compared to 52SBM while there was no evidence for differences between those fed PCON and all other sources.Broilers fed CON and 56SBM had increased (P < 0.001) AID of Val compared to PCON and 52SBM with no evidence for difference between those fed CON and PCON.
In conclusion, SBM processed from 2 high quality soybean varieties from South Carolina resulted in increased SBM and had improved amino acid digestibility compared to experimentally processed soybean meal from similar sources.The 56SBM had increased digestibility of indispensable AA compared to SBM from PCON and 52SBM when fed to 15-day-old broilers.The increased AID of AA and increased AA content of high CP soybean meal resulted in an increase in digestible amino acid content provided by SBM.
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No endorsement is intended, nor is criticism implied of similar products not mentioned.Persons using such products assume responsibility for their use in accordance with current label directions of the manufacturer.At hatch, 240 male broilers (Ross 308, Aviagen, Sallisaw, OK) were placed in battery cages with 6 broilers per cage and 10 replicates per treatment.

Table 1 .
Chemical analysis of individual soybean meal varieties (as-is basis)1,2