Effects of Increasing Soybean Meal in Diets Based on Corn and Effects of Increasing Soybean Meal in Diets Based on Corn and Dried Distillers Grains with Solubles on Growth Performance and Dried Distillers Grains with Solubles on Growth Performance and Carcass Characteristics of Late Finishing Pigs Carcass Characteristics of Late Finishing Pigs

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Effects of Increasing Soybean Meal in Diets Based on Corn and Dried Distillers Effects of Increasing Soybean Meal in Diets Based on Corn and Dried Distillers Grains with Solubles on Growth Performance and Carcass Characteristics of Late Grains with Solubles on Growth Performance and Carcass Characteristics of Late Finishing Pigs Finishing Pigs
Cover Page Footnote Cover Page Footnote Introduction Soybean meal (SBM) is a key dietary component and a commonly used protein source for swine due to its high digestibility, consistent processing methods, and excellent AA profile. However, it is common for swine diets to be formulated with increasing amounts of feed grade AA and corn co-products such as DDGS. These are used as partial or complete replacements of SBM due to widespread availability and lower cost. As a result, late finishing swine diets may contain very little SBM in corn-based diets.

Kansas State University Agricultural Experiment Station and Cooperative Extension Service
Corn-based diets with low SBM levels typically contain CP concentrations below 12 or 13%, which may compromise growth performance or carcass characteristics of finishing pigs. 2 Recent studies have evaluated replacement of SBM with corn gluten meal 3 and soy protein concentrate 4 in diets containing 12% CP and observed linear reductions in growth performance of late finishing pigs, which suggests that there may be biological benefits to the pig when utilizing dietary SBM. Thus, the influence of dietary CP sources such as DDGS or from SBM must be further researched and understood. Therefore, the objective of this experiment was to determine if SBM is needed to optimize growth performance of finishing pigs from 220 lb to market when provided corn and DDGS-based diets.

Materials and Methods
The Kansas State University Institutional Animal Care and Use Committee approved the protocol used in these experiments. This study was conducted at a commercial research facility in southwestern Minnesota. The barn was naturally ventilated and double-curtained-sided. Each pen was equipped with a 4-hole stainless steel dry feeder and a cup waterer to allow ad libitum access to feed and water.

Animals and diets
A total of 1,827 pigs (L337 × 1050, PIC; initially 215.8 ± 2.5 lb) were used in two groups, respectively, with 23 to 27 pigs per pen and 14 pens per treatment (7 per group). Pens of pigs were blocked by initial BW and randomly assigned to 1 of 5 dietary treatments in a randomized complete block design. Experimental diets were corn-based with 25% DDGS and feed grade AA. Soybean meal levels increased from 0 to 16% in 4% increments, and replaced feed grade AA. All diets were formulated using assumed AA composition and SID from the NRC. 5 Additionally, diets were formulated to be isocaloric and contained 0.70% SID Lys (Table 1). Dietary additions of feed grade AA were adjusted to meet the minimum AA requirements in relation to Lys between the two groups.
Pens of pigs were weighed and feed disappearance was measured on d 0, 15, and 29; or on d 0, 19, 34, and 42 for groups one and two, respectively, to determine ADG, ADFI, and F/G. On d 15 and 19 of the experimental period for groups one and two, respectively, two pigs within each pen were marketed. The remaining pigs were then marketed at the conclusion of the experiment. At completion of the first group, final pen weights were recorded and each pig was tattooed with a pen identification number and transported to a commercial abattoir (JBS Swift, Worthington, MN) for processing and carcass data collection. Carcass measurements included HCW, backfat depth, loin depth, and percentage lean (as per JBS Swift's proprietary calculation). Carcass yields were then calculated by the pen average HCW divided by the pen average final BW. Additionally, two pigs/pen were randomly selected for collection of backfat tissue and analyzed at Iowa State University for determination of iodine value. Due to unforeseen circumstances relating to COVID-19, carcass data were not collected for pigs from the second group.

Statistical analysis
Data were analyzed using the GLIMMIX procedure in SAS (v. 9.4, SAS Institute, Inc., Cary, NC) and considered pen as the experimental unit. The statistical model considered fixed effects of dietary treatment, linear and quadratic contrasts, and random effects of group and block. Additionally, initial BW was utilized as a covariate in the statistical model. All data are reported as least square means and considered statistically significant at P ≤ 0.05 and marginally significant at 0.05 < P ≤ 0.10.

Results and Discussion
For overall growth performance, as dietary SBM increased in the late finishing period, pigs exhibited marginally increased BW at first marketing and at experiment end (Table 2; linear P = 0.066 and quadratic P = 0.065, respectively). There were no overall effects of SBM level on ADG, ADFI, nor F/G. For carcass characteristics, there was no influence of SBM level on carcass criteria measured.
In the present experiment, all treatments' CP exceeded the 13% requirement estimate for late finishing pigs established by Soto et al. 2 However, our results suggest that increasing dietary SBM concentrations up to 8% in diets that contain 25% DDGS marginally increased final BW but did not influence carcass characteristics of late finishing pigs.
Brand names appearing in this publication are for product identification purposes only. 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.   Represents data from the first group and 7 replications per treatment. 4 Final BW utilized as a covariate in the statistical model.

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HCW utilized as a covariate in the statistical model. 6 Represents average of a subset of 2 randomly selected pigs/pen.