Initial BW Research Articles

119 Effects of Replacing Lactose with Novel Carbohydrate Sources on Feed Intake Preference in Nursery Pigs

Abstract This experiment was conducted to determine the effects of replacing lactose in phase 1 and 2 nursery diets with 1 of 2 novel carbohydrate products; (Cargill Starches, Sweeteners, & Texturizers, Blair, Nebraska) on feed intake preference. Pigs (n = 300; 600×241, DNA; initial BW = 5.6 kg) were used in three, 3-d periods to determine feed intake preference from various CHO sources. Pigs were weaned at approximately 21 days of age and allotted to pens in one of two BW blocks based on initial BW (initially 5.0 and 6.2 kg), with 5 pigs/pen. Pigs were provided ad libitum access to water and pelleted feed. To determine feed intake preference, each pen was equipped with two identical feeders containing dietary treatments. Feeder location within pen was balanced across dietary comparison to minimize feeder location bias. On d 3, 9, and 17 post-weaning, pigs were weighed, and pens were allotted to 1 of 3 dietary comparisons in a completely randomized design. There were 20 replications of each diet comparison during each period. The carbohydrate sources utilized were whey powder, a novel dry carbohydrate (CHO-D), and a novel liquid carbohydrate (CHO-L). Dietary treatments were corn-soybean meal-based with 5-7.5% DDGS and included: 1) a positive control (PC; containing 10 and 5% lactose, phase 1 and 2, respectively); 2) a diet replacing 100% of lactose with CHO-D; and 3) a diet replacing 100% of lactose with CHO-L. Novel carbohydrate sources (CHO-D or CHO-L) replaced whey powder on a total carbohydrate basis in phase 1 and 2 diets. Phase 1 diets were fed from d 3 to 6 and 9 to 12, with phase 2 diets fed from d 17 to 20. Within each period, 20 pens were used to test the effect of feeder location within pen with each feeder containing the PC diet. There was no observed effect of feeder (P > 0.100) on daily feed disappearance indicating feeder location within pen did not influence feed intake preference (Table). During each period, dietary comparisons included: 1) PC vs. CHO-D; and 2) PC vs. CHO-L. For comparison 1, pigs tended (P = 0.060) to prefer the diet with CHO-D compared with the PC, on a percentage intake basis during phase 1; however, this reversed in phase 2 (P = 0.001) as pigs consumed more of the PC diet compared with the diet with CHO-D. For comparison 2, in all phases pigs preferred (P < 0.001) the PC diet compared with the CHO-L diet. In summary, pigs tended to prefer the CHO-D diet compared with the PC during phase 1, but the inverse was observed during phase 2. However, throughout all phases, pigs preferred the PC diet over the diet containing CHO-L. Additional research could be conducted to further explore the ability of CHO-D to increase feed intake immediately after weaning.

307 Effect of Calcium Magnesium Carbonate and/or Tylosin Phosphate Supplementation on Receiving Period Growth Performance in Yearling Beef Steers

Abstract The objective of this study was to evaluate the effects of CaMg(CO3)2 (MIN-AD, Papillon Agricultural Company, Easton, MD; MA) and/or tylosin phosphate (Tylan, Elanco, Indianapolis, IN; TY) supplementation on growth performance of yearling beef steers during transition to a finishing diet during the first 28 days on feed. Treatments were arranged in a 2 × 2 factorial arrangement including MA and TY. Beef steers (n = 156; initial BW = 469 ± 18.0 kg) were randomly assigned to dietary treatments pens (7 to 8 steers/pen) with pen (n = 20 pens total, 10 pens/main effect mean, and 5 pens/simple effect mean) serving as the experimental unit. Cattle were transitioned from a 30 % roughage receiving diet to a 7 % roughage finishing diet based on dry-rolled corn, dried distillers grains plus solubles, a liquid supplement, and oat silage over the initial 20 d period. Monensin sodium was included in the diet at 30 mg/kg (DM basis). The MA was included at 1.5 % of the diet (DM basis) in replacement of dry-rolled corn and TY was provided at 90 mg/animal·d-1. Data were analyzed according to a randomized complete block design with the fixed effects of MA, TY, or their interaction; block was considered a random effect. No interaction was noted between MA or TY (P ≥ 0.68) for any variables measured. The main effect of TY did not influence d 28 BW, ADG, DMI, or G:F (P ≥ 0.43). The main effect of MA reduced DMI by 1.9 % (P = 0.01), but did not appreciably influence d 28 BW, ADG, or G:F (P ≥ 0.42). MA may decrease DMI while maintaining similar BW gain and efficiency compared with non-supplemented calves.

167 Timing of Implants use in a Backgrounding System

Abstract A 2-year study conducted at the Eastern Nebraska Research and Extension Center near Mead, Nebraska determined the effects of backgrounding rate of gain and implanting during the winter or summer phases on animal performance and carcass traits. The study design was a 2 x 3 factorial arrangement with the factors of winter gain (0.45 or 0.90 kg/d; LG and HG, respectively) and three implant strategies. The implant strategies included a 36 mg zeranol (Ralgro; Merck Animal Health, De Soto, KS) implant during the winter phase and 40 mg trenbolone acetate and 8 mg estradiol (Revalor-G; Merck Animal Health) implant during the summer phase (STRNG), no implant during the winter phase and Rev-G during the summer phase (MED), and no implant during the winter or summer phases (NONE). The study used 240 (initial BW = 247 kg, SD = 5.9 kg YR 1; BW = 255 kg, SD = 10.9 kg YR 2) weaned steers each year that were fed one of two backgrounding diets consisting of bromegrass hay and 10% MDGS (LG) or 30% MDGS (HG). Steers were backgrounded in the feedlot for a 148-day winter phase followed by a 56-day summer phase where they grazed smooth bromegrass paddocks. Upon arrival in the feedlot for the finishing phase, steers received 200 mg TBA and 40 mg estradiol (Revalor-XS; Merck Animal Health) and were fed a common diet for the entire finishing phase. In the winter phase, steers fed the HG diet had a greater ADG, ending BW, DMI, and improved G:F over steers fed LG (P < 0.01). Steers that received a Ralgro implant during the winter phase (STRNG) were observed to have an 13% improved ADG (P < 0.01), a 10% increase in G:F (P < 0.01), and an additional 14 kg of BW for the winter phase. There were no interactions between the rate of gain and implant strategy (P ≥ 0.15) during the winter period. In the summer, HG steers had maintained greater ending BW than LG, although LG steers had greater ADG than HG (0.70 and 0.53 kg, respectively; P < 0.01) due to compensatory gain. Steers assigned to HG during the winter phase had a greater IBW for the finishing phase. Steers fed HG during the winter and administered an implant at both backgrounding phases (STRNG) had the greatest HCW with no differences in ADG or G:F during the finishing phase. Combining a strong implant program and an increased rate of gain during winter backgrounding resulted in 34 kg of additional HCW at marketing. Implant strategy and rate of gain during the winter growing period had additive effects to increase animal performance through all phases.

260 Effect of Biochar Inclusion in Finishing Beef Cattle Diets on Enteric Methane Production and Performance

Abstract An experiment was conducted to evaluate the impacts of biochar on methane (CH4) and carbon dioxide (CO2) emissions and interim performance of finishing beef cattle. This experiment used crossbred beef steers (n = 128; initial BW= 347 kg ± 9 kg) fed a biochar sourced from pistachio shells (VGrid Energy Systems). The diet contained 61% dried rolled corn, 30% Sweet Bran (Cargill Corn Milling, Blair, NE), 5% wheat straw, and 4% supplement with Tylan (Elanco Animal Health) targeted at 9.7 mg/kg of dry matter (DM) and Rumensin (Elanco Animal Health) at 33.1 mg/kg of DM in a fine ground corn carrier. Two treatments consisted of a control (CON) group fed a diet containing no biochar and a biochar (BIO) group fed a diet with 0.5% biochar replacing 0.5% dried rolled corn in the diet. Cattle were implanted on d 0 with Revalor XS (Merck Animal Health). Pen was the experimental unit with 8 steers per pen and 8 replications. Interim data were collected on d 90 of the experiment. Four pen replications were rotated twice through a two-chambered barn equipped with open-circuit indirect calorimeters using a negative air pressure system. Within replicate, each pen of cattle was monitored in both chambers. LI-COR (Biosciences, Lincoln, NE) sensors were used to capture emissions (7700 Open-Path CH4 analyzer and 7500DS Open-Path CO2/H2O analyzer). Each replicate was monitored for 5 d in the pen chamber followed by 1 d manure contribution and 1 d used for baseline corrections. Cattle performance data were analyzed using the MIXED procedure of SAS with treatment as the fixed effect and emissions data were analyzed as a repeated measure. Feeding biochar tended to increase emissions of CH4 in g/d (194 g/d BIO and 176 g/d CON, P = 0.09) but had no other effects on CH4 in g/kg of dry matter intake (DMI) with 16.3 g/kg DMI BIO and 14.2 g/kg DMI CON (P = 0.27). Likewise, feeding BIO had no effect on CO2 as g/day (10854 g/d BIO and 10691 g/d CON, P = 0.78) or as g/kg of DMI (904 g/kg DMI BIO and 860 g/kg DMI CON, P = 0.34). Interim cattle performance showed no differences between treatments in interim body weight (529 kg BIO and 534 kg CON, P = 0.49) and average daily gain (2.02 kg/d BIO and 2.07 kg/d CON, P = 0.50). Dry matter intake (12.3 kg/d BIO and 12.1 kg/d CON, P = 0.45) was not different between groups, which resulted in no differences in feed efficiency (0.165 BIO and 0.169 CON, P = 0.23). Supplementing biochar at 0.5% of the diet DM did not decrease eructed CH4 (slight increase) or impact respired CO2. Interim animal performance was not impacted by feeding biochar.

PSV-14 Effects of Forage or Coproduct-Based Transition Diets on the Rumen Microbiome and Ruminal Fermentation ex Vivo in Feedlot Steers

Abstract The objective was to determine the effect of replacing forage with coproducts in transition diets on rumen microbiome composition and ruminal fermentation ex vivo after steers consumed a common finishing diet. A random subset of 30 steers were selected from a larger, separate pen study. Steers were blocked by initial BW and allotted into 9 pens. Pens were then assigned to 1 of 3 dietary treatments for the 35 d adaptation period: a forage-based diet (FO; alfalfa and grass hay), a coproduct-based diet (CO; soybean hulls and modified wet distillers grains with solubles), and a coproduct-based diet pair-fed (CO-P) to isoenergetic levels of FO. Dry-rolled corn inclusion increased with either decreasing forage or coproduct inclusion. Both FO and CO were fed with slick bunk management. At d 35 and 63, rumen fluid was collected by esophageal tubing to determine differences in fermentation of the finishing diet as the substrate in an ex vivo model. Rumen fluid was also utilized for microbiome analysis using 16S rRNA sequencing on the Illumina MiSeq platform with 2 × 300 bp paired-end sequencing. Sequencing reads were analyzed within QIIME2. Statistical analyses were conducted using SAS 9.4. Fermentation data were analyzed using the MIXED procedure, while bacterial relative abundance data were analyzed in the GLIMMIX procedure. Correlations were analyzed using the CORR procedure. A treatment × sampling day interaction (P = 0.02) was observed for in vitro dry matter disappearance; on d 35, it was greater in steers fed CO compared with CO-P (58 vs. 53%, respectively), but no differences were observed on d 63. Within the rumen microbiome, there was a tendency (P = 0.06) for alpha diversity to have a treatment × day interaction. Specifically, CO steers had the greatest decrease in alpha diversity from d 35 to 63, but there was no change in alpha diversity in FO steers and CO-P steers over time. Final pH in from the ex vivo model was positively correlated (r = 0.32) with Bacteroidetes relative abundance but negatively correlated (r = -0.25) with Proteobacteria (P ≤ 0.05). In vitro dry matter disappearance was positively correlated (r = 0.38) with relative abundance of Firmicutes, but negatively correlated (r = -0.43) with Proteobacteria (P < 0.01). Dietary treatment did not affect (P ≥ 0.21) richness within the rumen microbiome. Rumen microbiome composition and ex vivo fermentation results suggest all treatments were adapted for the finishing diet at the conclusion of the 35-d adaptation period.

102 Growth Performance in Pigs fed a High Soybean Meal Diet During Heat Stress

Abstract In the U.S. swine industry, feeding programs are focused on using feed ingredients that are easily digestible and cost effective. With the predicted increases in soybean processing, pig producers may have increased availability of a cost-effective protein source in soybean meal (SBM). This expanded availability of SBM may result in feeding protein above the ostensible requirements, which would likely intensify the thermic effect of digestion, potentially increasing the susceptibility of the pig to heat stress (HS). Heat stress has damaging effects on feed intake and growth performance, costing the swine industry >$900 million annually. Therefore, the study objectives were to evaluate the effects of dietary crude protein diets (in the form of SBM) during HS on growth performance in growing pigs. Growing pigs (n = 40; initial BW = 55 ± 5.6 kg) were allocated into six treatments: 1) thermoneutral (TN) ad libitum control diet (TN-Ctl; n = 6), 2) TN pair-fed (PF) control diet (PF-Ctl; n = 6), 3) HS ad libitum control diet (HS-Ctl; n = 8), 4) TN ad libitum high SBM diet (TN-SBM; n = 6), 5) TN PF high SBM diet (PF-SBM; n = 6), and 6) HS ad libitum high SBM diet (HS-SBM; n = 8). The control diet included 15% crude protein (CP) while the high SBM diet included 23% CP with excess amino acids. The study consisted of two periods: Period 1 (P1; 7 d) in which all pigs were housed in TN environments (26.7 ± 1.4°C) with ad libitum access to respective diets. Period 2 (P2; 21 d), HS groups were exposed to cyclical HS with daytime temperatures reaching 35°C and evening temperatures decreased to 29.4°C. During P2, PF groups were fed to respective HS-Ctl or HS-SBM equivalents in TN conditions. Pigs exposed to HS had an overall increase in rectal temperature and respiration rate (0.91°C and 45 bpm, respectively; P ≤ 0.01) and HS-SBM pigs had increased evening rectal temperature (± 0.13°C; P ≤ 0.01), relative to HS-Ctrl. Overall, HS decreased ADFI (19%; P ≤ 0.01), ADG (26%; P ≤ 0.01) and increased F:G (10%; P ≤ 0.01) irrespective of dietary CP levels. Loin muscle area (P = 0.19) and backfat (P = 0.98) were not different between the TN and HS pigs regardless of diet. Circulating blood urea nitrogen levels did not differ between HS and TN pigs (P = 0.68), but an increase was observed in pigs fed the SBM diet relative to the control diet (P ≤ 0.01). In summary, these results demonstrate that HS decreases growth performance, but the negative effects are not augmented by feeding a high SBM diet.

308 Zinc Supplementation and Implant Abscess Effects on Growth Performance and Immune System of Growing Beef Steers

Abstract Zinc is beneficial in growth and immune system function in cattle. Angus-cross steers (n = 72; initial BW = 261 ± 14 kg) were used in this 58-day study to determine the effects of supplemental Zn on growth, trace mineral status, and circulating immune cell populations. On d 0, steers received a Component E-S with Tylan implant (Elanco Animal Health, Greenfield, IN) and were stratified by BW into twelve GrowSafe-equipped pens. Dietary treatments included: control (CON; no supplemental Zn), Zn100 (100 mg supplemental Zn/kg DM), and Zn150 (150 mg supplemental Zn/kg DM). Supplemental Zn was provided as Zn sulfate, and other trace minerals were supplemented at NASEM (2016) recommendations. Individual BW was recorded on days -1, 0, 12, 13, 27, 28, 56, and 57. Blood was collected from 9 steers per treatment on d 13 for immune cell population and function assays. Liver biopsies were conducted on 18 steers per treatment on d 14. On d 16, implant abscesses (ABSC) were evaluated, and all steers were treated with meloxicam (285 mg). Data were analyzed using the Mixed procedure of SAS (Cary, NC) with fixed effects of treatment and ABSC prevalence using steer as the experimental unit. Abscess prevalence among treatments was analyzed using Proc Glimmix. Sixty percent of steers had ABSC; ABSC prevalence was similar by treatment (P = 0.67). Steers without ABSC had greater (P = 0.04) ADG d 0 to 13 and tended to have greater (P = 0.09) ADG d 0 to 57. There was also a tendency (Trt × ABSC; P ≤ 0.09) for steers without ABSC to have greater ADG and G:F from d 14 to 27 in CON and Zn100 while within Zn150 steers without ABSC tended to have lesser ADG and G:F than ABSC steers. No other treatment by ABSC or treatment effects (P ≥ 0.14) for growth performance were observed. There were no treatment by ABSC effects for immune cell populations on d 13 (P ≥ 0.26). In Zn150 steers, activated natural killer and gamma delta T cells were increased (P ≤ 0.03) on d 13. Similarly, CD21+ MHC IIhi B cells tended to be increased in Zn150 steers (P = 0.08). Steers with ABSC had increased relative frequency of CD5+ and CD21+ B cells (P ≤ 0.05) and tended to have increased natural killer and CD21+ MHC IIhi B cells (P ≤ 0.09). In addition, steers without ABSC had greater liver Mn on d 14 than ABSC steers (P = 0.05). There were no other effects on liver trace mineral concentrations (P ≥ 0.17). These observations suggest Zn supplementation has greater impact on the cellular immune system, while ABSC have a greater effect on B cells and the adaptive immune system.

182 Influence of Group Size on Performance and Tail Damage Caused by Tail Biting in Undocked Growing-Finishing Pigs

Abstract Tail biting is both an economic and welfare problem of grower-finishing pigs. This destructive chewing behavior of tails of pen-mates causes challenges for farmers who raise pigs with intact tails, resulting in the need to find management solutions. Our objective was to determine if group size influences growth performance and tail damage caused by biting behavior of undocked growing-finishing pigs. Pigs (n = 432; initial BW = 22 ± 3.8 kg) with intact tails were allocated to small pens or large pens on totally slatted floors, with equal ratio of barrows to gilts in each pen and balanced for average initial BW across pens. Small pens (SM; n = 24) housed 9 pigs/pen and large pens (LG; n = 12) held 18 pigs/pen. Floor space allowance (0.76 m2/pig) and feeder-space allowance (4 feeder spaces/9 pigs) were consistent across group sizes. Pigs were weighed individually and feed intake was recorded on a pen basis every 4 weeks for 16 weeks until market weight (120 kg ± 3.8 kg), from which ADG, ADFI, and Gain:Feed were calculated. Number of pigs that were dead (mortality) and removed (morbidity) from the study due to tail biting, lameness, and other health issues were recorded throughout the study period. Tail damage was evaluated using a 0 to 4 scale scoring system: 0 = no evidence of tail biting; 1 = evidence of chewing without visible blood; 2 = evidence of tail bitten with visible blood and no signs of infection; 3 = open wounds or abscesses with signs of infection; 4 = partial or total loss of the tail. Tail damage was assessed once weekly during the study period, and the maximum tail score (MTS) that each pig received over the entire 16 weeks was recorded. Data were analyzed using SAS software, with a mixed procedure for performance variables and a frequency procedure with chi-square test for mortality, morbidity, and MTS. Group size did not affect growth performance (all P > 0.70; Table 1), mortality, or morbidity (Chi-square = 2.33, df = 2; P = 0.31). However, group size affected MTS (chi-square = 10.78, df = 4; P = 0.03). Pigs in SM experienced a marginally lower prevalence of tail biting compared with LG (16% vs. 9% of pigs receiving an MTS of 0); but greater severity with 13.0% of pigs in SM vs. 7.4% of pigs in LG receiving an MTS of 4. These results suggest group size did not influence growth performance, mortality, or morbidity; but affect severity of tail damage caused by tail biting. Compared with LG, SM had more pigs that lost their tails due to tail biting, which seriously compromised pig welfare.

PSII-13 Effects of Standardized Ileal Digestible Lysine, Fiber Level, and Amino Acid Ratios on Growth Performance of Nursery Pigs

Abstract An experiment was conducted to determine the interactive effects of standardized ileal digestible (SID) lysine, dietary fiber, and amino acid ratios on growth performance of nursery pigs. A total of 4,320 pigs (initial BW = 7.8 kg), placed in pens of 36 mixed sex pigs, were used in a 43-d trial. Treatments were arranged in a 2 × 2 × 2 factorial structure with two levels of SID Lys (1.15 or 1.38%), two levels of dietary fiber [control or high fiber (5% sugar beet pulp + 3.75% soy hulls)], and two amino acid ratio profiles [control (65% SID Thr:Lys, 58% SID Met+Cys:Lys, 67% SID Val:Lys, 55% SID Ile:Lys, and 18.5% SID Trp:Lys) or AA+ (5 percentage points greater than control ratios)] with 15 replicates per treatment. The experimental diets were fed from d 0 to 25 and a common corn-soybean meal-based diet was fed from d 25 to 43. Pigs were weighed on d 0, 25, and 43 to calculate ADG, ADFI, and G:F. Data were analyzed with the MIXED procedure in SAS. From d 0 to 25, there was a fiber × amino acid ratio interaction (P = 0.008) for ADFI, where pigs fed the high fiber diet had similar ADFI, regardless of AA ratios, but those fed control levels of fiber had reduced ADFI when fed AA+ ratios (Table 1). Similar interactions were also observed (P < 0.05) for overall (d 0 to 43) ADG, ADFI, and final BW. There were no other significant interactions (P > 0.05). As for main effects, pigs fed low Lys had reduced (P < 0.05) ADG, ADFI, and G:F. Feeding high fiber diets reduced (P < 0.05) G:F but did not impact (P > 0.05) ADG or ADFI. Pigs fed AA+ ratios had improved (P < 0.05) G:F but no evidence for differences (P > 0.05) for ADG or G:F was observed.

121 Use of Specialty Soy Products as Alternatives to Poultry Meal and Spray-Dried Blood Plasma in Nursery Pig Diets

Abstract A total of 2,260 pigs (initial BW = 6.7 ± 0.3 kg) were used to evaluate specialty soy protein sources as alternatives to poultry meal and spray-dried blood plasma on nursery pig performance. At weaning, pigs were allotted to 1 of 5 dietary treatments based on initial weight in two research nurseries. In the first facility there were 20 pigs per pen and 10 pens per treatment. In the second facility, there were 21 pigs per pen and 12 replications per treatment for a total of 22 replications per treatment. Pigs were fed experimental diets during phase 1 (d 0 to 7) and phase 2 (d 7 to 21) followed by a common diet for an additional 21 days (d 21 to 42). Dietary treatments included a control diet containing 9.5% poultry meal (AV-E Digest, XFE Products, Des Moines, IA) and 4.13 (Phase 1) or 2.75% (Phase 2) spray-dried blood plasma (Appetein, APC Inc., Ankeny, IA) and a 2 × 2 factorial with a novel soy protein concentrate (AX3 Digest; Protekta; Plainfield, IN) or microbial enhanced soy protein (MEPro; Prairie Aquatech; Brookings, SD) replacing poultry meal or poultry meal and spray-dried blood plasma. Protein sources were added to the diet to maintain a similar level of soybean meal and balance for SID amino acids. Thus, soy protein sources were added to the diet at 6 and 13 (Phase 1) or 10.75% (Phase 2) to replace poultry meal or poultry meal and spray-dried blood plasma, respectively. Dietary treatment structure allowed the opportunity to compare each protein source to each other, soy protein sources as a replacement to poultry meal, and soy protein sources as a replacement to spray-dried blood plasma. During the experimental period (d 0 to 21), pigs fed novel soy protein concentrate had improved (P < 0.001) G:F with no differences (P > 0.10) in ADG or ADFI compared with pigs fed microbial enhanced soy protein (Table). Pigs fed either soy protein as a replacement of poultry meal had increased (P < 0.001) ADG and ADFI compared with pigs fed the control diet. Additionally, pigs fed either soy protein source as a replacement of spray-dried blood plasma had improved (P = 0.044) G:F compared with pigs fed either soy protein without replacing spray-dried blood plasma, with no differences (P > 0.10) in ADG or ADFI. In summary, utilizing a specialty soy protein source as a replacement for poultry meal improved growth performance. Further replacing poultry meal and spray-dried blood plasma with the specialty soy proteins improved feed efficiency during the experimental period. The novel soy protein concentrate improved feed efficiency compared with microbial enhanced soy protein during the experimental period with no effect on ADG or ADFI.

51 Evaluation of the Effects of a Single Intranasal Dose of Essential oil Spray on the Nasopharyngeal Microbiota of Feedlot Cattle: A Pilot Study

Abstract Five essential oils (EO) were previously characterized in vitro and identified as candidates for the development of an intranasal EO spray to inhibit the colonization and proliferation of bovine respiratory disease (BRD) pathogens, especially at feedlot entry when cattle are most susceptible to BRD. In the present pilot study, these EO were evaluated for their potential to reduce BRD pathogens and to modulate nasopharyngeal microbiota in feedlot cattle. Angus-crossbred calves [n = 40; 7to 8 months old; initial BW = 284 ± 5 kg (SE)] received either an intranasal EO spray consisting of ajowan, thyme, fennel, cinnamon leaf, and citronella (0.025%, vol/vol per EO) suspended in PBS (3 mL per nostril) or PBS (Control) on day (d) 0. Deep nasopharyngeal swabs were collected on d -1 (24 h before EO administration), 1, 2, 7, 14, 28, and 42, and processed for microbiota characterization using 16S rRNA gene. The calves that received EO had similar feed intake (P = 0.62) and average daily gain (P = 0.37) than control calves. Overall bacterial concentration estimated by qPCR was greater in control (P =0.049) than EO group, with EO group having reduced bacterial concentration on d 2 (P = 0.01) and d 7 (P=0.07). Sequencing results revealed that overall community structure of nasopharyngeal microbiota was different between EO and control calves (PERMANOVA: R2 = 0.01, P = 0.02), and was strongly affected by time (R2 = 0.1, P = 0.001). Within individual sampling day, the effect of EO on community structure was only detected on d 1 (R2 = 0.05, P = 0.03). Microbial richness (observed ASVs) and diversity (Shannon and Inverse Simpson) were not different between the two groups (P ≥ 0.17). The effect of EO on the most dominant phyla was observed (P ≤ 0.05) with Proteobacteria (d14), Firmicutes (d1, 14), Actinobacteriota (d14), and Bacteroidota (d2, 14). Among the predominant genera: Moraxella, Ralstonia, Mycoplasma, Mannheimia, Filobacterium, Pseudomonas, Pasteurella, and Corynebacterium, the abundance of Mannheimia (4.34% vs. 10.4%) and Filobacterium (2.53% vs. 11.9%) were reduced (P < 0.05) by EO on d 2. In control calves, Mannheimia was enriched by 3.9-fold (P < 0.05) from d -1 (2.66%) to d 2 (10.4%), whereas it remained constant in EO calves (P > 0.05) between these days (2.23% and 4.34%). Corynebacterium was also decreased (P < 0.05) in EO calves on d 1 (1.06% vs. 2.58%). The BRD-associated Histophilus genus was low (mean 0.02%), so EO effect was not assessed. Overall, a single dose of intranasal EO spray modulated nasopharyngeal microbiota and reduced the abundance of Mannheimia within 48 h post administration while having no effect on feed intake and daily gain. Our study highlights that nasally dosing EO may modulate respiratory microbiota and potentially mitigate bovine respiratory disease in finishing cattle.

PSI-A-11 The Effect of Soybean Meal and Its Functional Compounds on Growth Performance, Fecal Scores, and Fecal Characteristics of Nursery Pigs

Abstract High levels of soybean meal (SBM) are deterred in nursery diets due to antinutritional factors and impacts on fecal consistency. However, SBM may improve performance in the presence of inflammatory stressors due to its functional compounds. The experimental objective was to evaluate the non-nutritive value of SBM and its functional compounds on growth performance and fecal characteristics of nursery pigs. A total of 408 newly weaned pigs with an initial BW of 5.43 ±0.77 kg were used for a 35-d study across three replications. Pigs were randomly assigned to 1 of 6 dietary treatments fed across 3 phases: d 0-7 (phase 1), d 7-21 (phase 2), and d 21-35 (phase 3). Dietary treatments consisted of a high SBM control (SBMC), a control void of SBM (SP), but included soy protein isolate and concentrate to provide amino acids similar to SBM in SBMC; SP formulated to equivalent contribution of isoflavones as SBMC (SP+ISO); SP diet fortified with soybean functional lipids to the level of SBMC (SP+LIP); SP formulated with a similar ratio of insoluble to soluble fiber as SBMC (SP+FIB); or SP diet fortified with lunasin (SP+LUN). There were 9 split-sex pens per treatment (7 or 8 pigs/pen). On d 7, 14, 21, and 35, pigs and feeders were weighed, pen fecal samples were collected, and fecal score was evaluated using a 4-point scale (1 = solid; 4 = liquid). Continuous data were analyzed as a linear mixed model (PROC MIXED) with treatment and period as fixed effects, replicate as a random effect, and initial BW as a covariate where appropriate. Fecal scores were analyzed using a multinomial model in PROC FREQ. Compared with SP, on d 7 and 14 pigs fed SBMC and SP+FIB had reduced fecal dry matter (DM%), but on d 21 and 35, fecal DM% did not differ among treatments (time×treatment P = 0.016). There was a treatment×time interaction for fecal score, whereas on d 7, pigs fed SBMC had increased proportion of semi-liquid feces and on d 14 pigs fed SP+FIB had increased abundance of semi-liquid feces, but fecal score distribution did not differ on d 21 or 35 (time×treatment P = 0.035). Fecal water binding capacity (WBC) did not differ across time (P=0.288) but relative to SP, SBMC had 30% less fecal WBC (P = 0.002). There was a treatment×time interaction for ADG and ADFI. Pigs fed SP+ISO had greater ADG in phase 2, but pigs fed SBMC gained more in phase 3 (time×treatment P = 0.044). Among treatments, ADFI did not differ in phase 1 and 2, but was increased in SBMC in phase 3 (time×treatment; P = 0.037). Pigs fed SBMC tended to have the greatest final BW (P = 0.071). Feeding SBM altered fecal characteristics in the early nursery period, but improved growth performance from d 21-35 post-weaning.

125 Effects of Wheat Middlings and Sugar Beet Pulp on Growth Performance of Nursery Pigs

Abstract An experiment was conducted to determine the interactive effects of wheat middlings (WM) and sugar beet pulp (SBP), on growth performance of nursery pigs. A total of 2,393 pigs (initial BW = 7.4 kg), placed in pens with 33 to 35 pigs each, were used in a 42-d trial. Treatments were arranged in a 2 × 3 factorial structure with two levels of WM (0 or 15%) and three levels of SBP (0, 2.5, or 5%) with 12 replicates per treatment. Corn and a fermented soybean meal product (ME-Pro, Prairie AquaTech, Brookings, SD) were replaced by the fiber sources to achieve the desired levels, whereas soybean meal inclusion rate was held constant across treatments. Diets were not balanced for net energy. The experimental diets were fed from d 0 to 21 and a common corn-soybean meal-based diet was fed from d 21 to 42. Pigs were weighed on d 0, 21, and 42 to calculate ADG, ADFI, and G:F (Table 1). Data were analyzed with the MIXED procedure in SAS. There was no evidence (P > 0.10) for WM × SBP interactive effects. From d 0 to 21, pigs fed WM had poorer (P ≤ 0.040) ADG, ADFI, and G:F. Feeding up to 5% SBP did not affect (P > 0.10) growth performance. From d 21 to 42, pigs previously fed WM had improved (P = 0.012) G:F and those previously fed SBP had decreased (P, linear = 0.032) G:F. Overall (d 0 to 42), pigs fed WM had lower (P ≤ 0.048) ADG and G:F and those fed SBP had decreased (P, linear = 0.012) G:F. In conclusion, there were no interactive effects between WM and SBP. Pigs fed 15% WM had decreased performance and a minor impact was observed by feeding up to 5% SBP.

281 Effects of Corynebacterium Glutamicum Cell Mass Supplementation on Modulation of Mucosa-Associated Microbiota to Intestinal Health of Nursery Pigs

Abstract The objectives were to evaluate the effects of Corynebacterium glutamicum cell mass (CGCM) supplementation, replacing blood plasma in diets, on the gene expressions of biomarkers associated with peptidoglycan and their correlation with intestinal health in nursery pigs. Weaned pigs (n = 32) were allotted to 4 dietary treatments based on the randomized complete block design with initial BW as blocks. The diets with supplementation of CGCM (0, 0.7, 1.4, and 2.1%) replacing blood plasma up to 1.5% were fed for 21 d. Pigs were euthanized on d 21 to collect proximal and distal jejunal mucosa to measure intestinal health markers. Gene expression of receptors associated with peptidoglycan (PGN) and intestinal health were evaluated by PCR. Correlations between gene expressions of receptors associated with PGN and intestinal health markers in jejunal mucosa were assessed by Pearson’s analysis. Data were analyzed using the Mixed procedure of SAS 9.4. Increasing CGCM supplementation affected (quadratic) the relative gene expression of peptidoglycan recognition protein (PGLYRP) 1 (P = 0.080, max: 1.85% at 1.1% CGCM), PGLYRP4 (P < 0.05, max: 3.24% at 1.2% CGCM), and interferon-γ (P = 0.088, max: 3.25% at 1.1% CGCM). Increasing CGCM supplementation did not affect the relative gene expression of PGLYRP2A, PGLYRP2B, PGLYRP3, Toll-like receptor (TLR) 2, TLR4, Nucleotide-binding oligomerization domain-containing protein (NOD) 1, NOD2, cluster of differentiation (CD) 14, and nuclear factor-kappa B. In proximal jejunal mucosa, PGLYRP1 was positively correlated with immunoglobulin A (IgA) and interleukin 8 (r = 0.50 and 0.45, respectively; P < 0.05). PGLYRP4 was positively correlated with protein carbonyl and IgA (r = 0.65 and 0.60, respectively; P < 0.05). Interferon-γ was positively correlated with Campylobacter coli (r = 0.61; P < 0.05) and IgA (r = 0.52; P < 0.05). PGLYRP2A was negatively correlated (r = -0.44; P < 0.05) with Pseudomonadaceae. TLR2 was positively correlated with Corynebacteriaceae, Pasteurellaceae, and Propionibacteriaceae (r = 0.55, 0.51, and 0.52, respectively; P < 0.05). NOD1 was positively correlated (r = 0.50; P < 0.05) with Propionibacteriaceae. NOD2 were positively correlated with Pasteurellaceae and Propionibacteriaceae (r = 0.73 and 0.53, respectively; P < 0.05). CD14 was negatively correlated (r = -0.47; P < 0.05) with IgA. Campylobacteraceae was positively correlated with tumor necrosis factor-alpha (r = 0.50; P < 0.05). Pseudomonadaceae was negatively correlated with IgG (r = -0.39; P < 0.05). In conclusion, supplementing 1.1% to 1.2% CGCM, replacing 0.8 to 0.9% blood plasma, increased the relative gene expressions of PGLYRP1, PGLYRP4, and interferon-γ, which were related to the modulation of the mucosa-associated microbiota, immune response, and oxidative stress markers caused by CGCM supplementation. Supplementing 2.1% CGCM showed to have a similar expression of receptors associated with PGN and intestinal health by promoting the growth of less inflammatory microbiota.

40 Effect of Soybean Meal Inclusion on Grow-Finish Pig Performance and Nitrogen Balance

Abstract Mixed-sex pigs (n = 240 PIC 337×1050; initial BW = 23 ± 4.7 kg) were used to evaluate the effects of soybean meal (SBM) inclusion on the growth performance and nitrogen balance of grow-finish pigs. Pigs were assigned across 60 split-sex pens, and pens were randomly assigned to one of three dietary treatments (10 pens∙treatments-1∙sex-1). Diets were formulated with increasing SBM for an approximate 3% incremental difference in crude protein (CP) between treatments. The treatments were: 1) low SBM (L-SBM) corn-soy diet supplemented with synthetic amino acids, 2) medium SBM diet (M-SBM) with SBM formulated to replace all synthetic lysine and equal to L-SBM in SID lysine, and 3) high SBM diet (H-SBM) contained excess levels of all amino acids. Diets were fed in four feeding phases ranging from approximately 25-50, 51-75, 76-105, and 106-135 kg for phases 1-4, respectively. From phases 1 to 4, SBM inclusion ranged from approximately 26-48% (SID Lys 1.06-1.32%), 19-41% (SID Lys 0.89-1.15%), 15-35% (SID Lys 0.76-1.01%), and 13-29% (SID Lys 0.68-0.86%), respectively. Additionally, diets within each phase were isocaloric. Pig BW and feed intake were measured for each phase to calculate ADG, ADFI, and G:F. On day 66, 18 gilts (n =6/treatment) were placed into metabolism stalls for total urine and feces collection over a 72 h period to assess CP digestibility and nitrogen balance. Pigs were marketed at approximately 134 kg BW, and carcass weight, backfat depth, and loin depth were measured at the harvest facility. Data were subject to ANOVA in SAS 9.4. Pen was the experimental unit, and the results were significant at P ≤ 0.05. Overall (d 0-98) pig ADFI, ADG, or G:F did not differ across treatments (P ≥ 0.202). However, there was a significant diet-by-phase interaction for ADG (P = 0.045) and G:F (P = 0.008), where H-SBM fed pigs grew faster in phase two compared with the M-SBM (1.07 vs. 1.02 kg/d; P = 0.026) or L-SBM (1.07 vs. 1.02 kg/d; P = 0.028) fed pigs. Consequently, in phase two, H-SBM pigs had improved G:F compared with M-SBM (0.47 vs. 0.44; P = 0.005) or L-SBM pigs (0.47 vs. 0.44; P = 0.001). However, these effects were not evident in the other phases. Apparent total tract digestibility of CP and nitrogen retention were similar between treatments (P ≥ 0.762). However, as expected, nitrogen retention as a proportion of intake, linearly decreased (P < 0.001) as SBM inclusion increased, which translated to an approximate 130% increase in total nitrogen excretion in pigs fed H-SBM compared with L-SBM (40.8 vs. 17.7 g/d; P < 0.001). In conclusion, low and high SBM formulations did not alter grow-finish pig overall performance. However, linearly increased nitrogen excretion was reported as SBM levels increased.

126 Effects of Soy Hulls and Sugar Beet Pulp on Growth Performance of Nursery Pigs

Abstract An experiment was conducted to determine the interactive effects of soy hulls (SH) and sugar beet pulp (SBP) on growth performance of nursery pigs. A total of 2,448 mixed sex pigs (initial BW = 6.3 kg), placed in pens of 36 pigs each, were used in a 40-d trial. Treatments were arranged in a 2 × 3 factorial with two levels of SBP (0 or 5%) and 3 levels of SH (0, 3.75, or 7.5%) with 11 replicates per treatment. Corn and a fermented soybean meal product (ME-Pro, Prairie AquaTech, Brookings, SD) were replaced by the fiber sources to achieve the desired fiber concentration, whereas soybean meal inclusion rate was held constant across treatments. Diets were not balanced for net energy. Experimental diets were fed from d 0 to 18 and a common corn-soybean meal-based diet was fed from d 18 to 40. Pigs were weighed on d 0, 18, and 40 to calculate ADG, ADFI, and G:F (Table 1). Data were analyzed with the MIXED procedure in SAS. From d 0 to 18, there was a SH × SBP interaction for ADG (P = 0.016) and ADFI (P = 0.023). Pigs fed diets with the highest inclusion of SH without SBP had increased ADG and ADFI; however, pigs fed diets containing SBP had improved performance up to 3.75% SH inclusion, and decreased ADG and ADFI with the highest SH inclusion. From d 18 to 40 and overall (d 0 to 40), there was an interaction (P ≤ 0.007) for G:F, where pigs fed diets containing 3.75% SH without SBP had improved G:F, while pigs fed diets with 3.75% SH containing SBP had worsened G:F. In summary, these results suggest that both fiber sources can be safely fed to nursery pigs, although the interactive effects must be considered when determining inclusion rates.

PSVI-14 Mitigating the Negative Effects of Heat Stress in Grow-Finish Pigs Using Water Delivered Oregano Essential Oil

Abstract Grow-finish pigs (n = 192) were used in a 28-day experiment to determine if adding oregano essential oil to the water would mitigate the detrimental effects of heat stress. Pigs (initial BW = 51.9 kg) were blocked by sex and BW and randomly allotted to a 2x2 factorial arrangement of water treatment (oregano essential oil vs. control) and environment (heat stress vs. thermoneutral). There were 6 pigs/pen (4 barrows and 2 gilts/pen) and 8 pens/treatment. Pigs were given 15 d to acclimate to pens and water treatment under thermoneutral conditions (21.1℃). Following acclimation, one-half the pigs were subjected to a 3-day diurnal heat stress (12 h at 33.3℃ and 12 h at 26.7℃). On d 22 of the experiment (3 d post-heat stress), one barrow/pen was euthanized; jejunal mucosa scrapings were collected, flash frozen in liquid nitrogen, and stored at -80oC for subsequent RNA isolation and cDNA creation. Gene expression of CDKN1A, TP53, GPX1, SOD1, SLC2A2, SLC2A5, and MUC2 were determined by qPCR using SYBR green, normalized using housekeeper genes and expressed relative to the control treatment using the 2-ΔΔCT method. Data were analyzed as RCB using GLM procedure in SAS 9.4 with fixed effects of water treatment, environment, and the interaction. Heat-stressed pigs had reduced ADG (P < 0.003) and Gain:Feed (P < 0.008) during the 3d heat stress compared with pigs housed in thermoneutral conditions. Post-heat stress, ADG (P < 0.001) and Gain:Feed (P < 0.001) increased in previously heat-stressed pigs compared with thermoneutral pigs. There was no effect of oregano supplementation before or during heat stress. However, in the post-heat stress period, ADG was increased (P < 0.05) by oregano supplementation in the water for both heat stressed and non-heat stressed pigs. Oregano supplementation did not affect ADFI before heat stress. An interaction (P < 0.005) of heat stress and water treatment was observed for ADFI during heat stress and after heat stress. During heat stress, oregano supplementation resulted in reduced feed intake. Post-heat stress ADFI was lowest for non-heat stressed pigs with no oregano supplementation. Oregano essential oil increased water consumption before (P < 0.02), during (P < 0.03), and after heat stress (P < 0.02), with an overall increase in water consumption of 35% compared with control pigs (P < 0.04). No interactions of heat stress and oregano supplementation were observed for gene expression. SLC2A2 expression tended (P < 0.08) to be downregulated when oregano essential oils were added to the water and upregulated following an acute heat stress. SLC2A5 expression was increased in pigs given oregano compared with control pigs (P < 0.02), but was unaffected by heat stress. Water delivered oregano essential oil increased water intake and had a slight effect on intestinal gene expression but did not mitigate the effects of a short-term heat stress.

211 Evaluating the Influence of Soybean Meal and its Bioactive Compounds on Nutrient Utilization, Fermentation, and Gastrointestinal Metabolites of Nursery Pigs

Abstract Recently soybean meal (SBM) has garnered more attention due to its increased feeding value during periods of stress and improved bioavailable energy. However, the influence of the innate bioactive compounds in SBM on the microbiome and fermentation products have not been fully elucidated. Thus, the experimental objective was to investigate the mechanism of action of SBM and its bioactive compounds in the gastrointestinal tract of nursery pigs. Two replications of 18 barrows (8.12 ± 0.80 kg BW; PIC800 × Camborough; n = 36), were randomly assigned to a dietary treatment of either a high SBM positive control (SBMC; 28.6%), a negative control void of SBM (SP), but included soy protein isolate and concentrate to provide amino acids from soy protein the same as SBM in SBMC; SP formulated to the same contribution and composition of isoflavones as SBMC (SP+ISO; 528 mg/kg of soy-isoflavones); SP diet fortified with soybean functional lipids of lecithin and phytosterols at similar concentration in SBMC (SP+LIP; 2.85 g/kg of functional lipids); SP formulated to the same contribution and ratio of insoluble to soluble fiber as SBM in SBMC (SP+FIB; 30 g/kg of soy fiber); or SP diet fortified with lunasin peptide at 3.81 g/kg (SP+LUN). Pigs were individually housed, and limit fed 2.5 times maintenance for a metabolism study consisting of a 6-d adaptation period, followed by 72-h of urine and fecal collections. On d 12, pigs were necropsied, and ileal, cecal, and colonic digesta were collected for immediate short-chain fatty acid (SCFA) analysis. The pH of ileal and cecal digesta were also collected. Data were analyzed as a linear mixed model with treatment as a fixed effect, replicate as a random effect, and initial BW as a covariate where appropriate using PROC MIXED in SAS 9.4. The pH of both ileal (P = 0.478) and cecal (P = 0.874) digesta did not differ among treatments. Relative to SP, pigs fed SP+FIB and SBM had a 97.8% and 63.4% increase in acetate production, respectively (P = 0.012). Similarly, pigs fed SP+FIB and SBM had increased total SCFA concentration in the ileum (P = 0.016), but there was no difference among treatments for propionate or butyrate production (P > 0.05). The molar proportion of butyrate was increased in the cecum in pigs fed SBMC and SP+FIB (P < 0.01), which increased the total concentration (mM/g) of SCFA in the cecal digesta (P < 0.05). The SP+FIB treatment had increased concentration (mM/g) and molar proportion of butyrate produced in the colon (P < 0.01). While pigs fed SBMC and SP had increased molar proportion of propionate in the colon (P < 0.05), total colonic SCFA concentration did not differ (P > 0.05). Collectively, SBM and its fiber can modulate SCFA composition and production in nursery pigs, and this may be related to an increase in fermentable substrates available to the microbiome.

232 Evaluation of Clay-Based Binders and in-Feed Antimicrobial on Growth Performance and Biological Measurements in Nursery Pigs

Abstract AbstractBarrows (n = 360; 200×400, DNA; initial BW = 6.5 ± 0.04 kg) were used in a 42-day study to evaluate clay-based binders or an in-feed antimicrobial on growth performance and biological measurements including fecal and blood analysis in nursery pigs. Pigs were weaned at approximately 21-day of age and randomly allotted to 1 of 4 dietary treatments in a completely randomized design. There were 5 pigs per pen and 18 replications per treatment. Dietary treatments were corn-soybean meal-based and fed in two phases from d 0 to 9 (Phase 1) and 9 to 21 (Phase 2) after weaning. Either clay-binders (Proteck, 0.40% of the diet; Nutriquest, Mason City, IA; Protect-8 Plus, 0.10% of the diet; Essential Ag Solutions, Sioux Falls, SD), or an antimicrobial (0.04% of the diet; Avilamycin (Kavault); Elanco, Greenfield, IN) were added to the control diet to create the experimental treatments. A common phase 3 diet was fed to all pigs from d 21 to 42. Overall (d 0 to 42), pigs fed Avilamycin had increased (P < 0.05) final BW, ADG and ADFI compared with all other treatments. There was evidence that frequency of fecal scores with softer feces increased over time (P < 0.001), with d 21 having the greatest frequency of diarrhea and soft feces (Table). Fecal E. coli colony count was less (P < 0.001) on d 21 compared with d 9 (2.04 vs. 4.03 Log10, respectively). For fecal myeloperoxidase (MPO), concentrations were less (P < 0.05) on d 21 compared with d 6 and 9 (0.014, 0.059, and 0.045 nmole∙min-1∙mL-1, respectively). For fecal DM, pigs fed Avilamycin had decreased (P < 0.05) DM percentage compared with all other treatments. Fecal DM percentage was greater (P < 0.05) on d 6 and 9 compared with d 21 (26.64, 27.63, and 24.88%, respectively). Correlation coefficients were used to further characterize the relationships between biological measurements in the nursery period. There was a strong negative correlation between fecal DM and score (P < 0.001) on d 6, 9, and 21 indicating that as fecal DM increased, the score became closer to 0, representing a firmer fecal sample. Fecal DM on d 6 and fecal DM on d 9 were negatively correlated with ADG from d 0 to 9 meaning that as growth rate increased, fecal DM decreased. In summary, pigs fed Avilamycin had increased BW, ADG, and ADFI compared with those fed the 2 clay-based additives or the control diet. There were no treatment effects on fecal score, fecal MPO, or blood measurements. However, fecal consistency was softer and fecal E. coli colony count and MPO had lower concentrations on d 21 compared with samples collected earlier in the nursery phase.

166 Influence of Source of Metabolizable Protein and Implant Status on Feedlot Performance and Feeding Behavior in Yearling Steers

Abstract Crossbred steers (n = 60; beginning BW 454 ± 24 kg) were used in a split-plot design with a 2 x 3 factorial arrangement of treatments to determine effects of source of metabolizable AA and implant status on animal performance and feeding behavior. Calves were blocked by initial BW and assigned to 1 of 5 BW blocks. Pen (n = 2 pens, 6 steer/pen) within each BW block were fed diets formulated to meet the RDP requirement of cattle and provide 150% and 152% the metabolizable Lys and Met requirement (RP-AA), or a diet designed to meet RDP and closely match the predicted metabolizable Lys and Met requirement (RDP-ONLY; metabolizable Lys = 99.3% of required; metabolizable Met = 119% of required, NASEM, 2016). Subsequently, within pen two calves were randomly assigned to 1 of 3 implant strategies: no implant, moderate (100 mg trenbolone acetate and 14 mg estradiol; Synovex Choice) or potent (200 mg trenbolone acetate and 28 mg estradiol; Synovex Plus). Cattle were fed for 125 days and feed intake and feeding behavior was determined using a semi-autonomous feed monitoring system (GrowSafe System Ltd). Data were analyzed using the MIXED procedure of SAS. There was a tendency for an interaction of source of metabolizable AA and implant status on dry matter intake; calves with a moderate implant consumed less feed when fed RP-AA while calves with a potent implant consumed greater amounts. Dry matter intake was not affected by metabolizable AA supply (P = 0.87) or implant status (P = 0.43). There was an interaction of source of metabolizable AA and implant status on ADG; implanted calves gained similar amount regardless of source of metabolizable AA, but non-implanted calves fed RP-AA gained 25% less compared with RDP-ONLY diet. Moderate and potent implants had greater ADG (P < 0.01) than non-implanted cattle. Overall, ADG was not affected by source of metabolizable AA (P=0.95). Feeding behavior was largely unaffected by source of metabolizable AA or implant status. Feed intake per meal, number of meals per day, meal duration and visit duration were not influenced by source of metabolizable AA or implant status (P ≥ 0.16). Number of visits per meal tended (P = 0.07) to be greater for RP-AA while feeding rate tended (P = 0.09) to be less. There was a significant interaction of source of metabolizable AA and implant status on feeding rate (P < 0.01) as non-implanted and potently implanted calves ate feed at a lesser rate when fed RP-AA but moderately implanted calves fed RP-AA ate feed at a greater rate compared with RDP-ONLY. These data demonstrate that metabolizable AA requirements of growing cattle are dynamically related to implant status in cattle, but that implant status does not largely influence feeding behavior.