Initial BW Research Articles

PSXII-20 Differences in Fat Accretion Rate of Different Depots of Angus, Brahman and Charolais Feedlot Steers

Abstract Understanding accretion rate of intramuscular and subcutaneous fat in feedlot steers is crucial to ensure that carcasses are meeting market specifications and therefore optimizing profitability. Intramuscular fat (marbling) and subcutaneous fat (P8 and rib) are key areas of assessment on the live animals and carcasses determining quality. The objective of the present study was to determine fat accretion rate in three popular breeds of cattle with contrasting accretion rate throughout the feedlotting period. We hypothesized that Angus would have the fastest fat accretion rate being early maturing. Thirty of each Angus, Brahman and Charolais steers were entered into a feedlot (344 ± 5.3 kg initial BW) and six of each breed randomly selected for slaughter at 50-day intervals for 200 days on feed (DOF). Ultrasound scanning and BW were measured at each slaughter point, measuring fat thickness at the rib and P8 site, intramuscular fat (IMF), kidney fat and the eye muscle area (EMA). Body weight, intramuscular fat (%), P8 and rib fat (mm) all had significant interactions between DOF and breed (P < 0.001). At the start of the feeding period, Charolais were lighter than Angus and Brahman (P > 0.001). However, Charolais (663.7 ± 9.31 kg) and Angus were the heavier (680.4 ± 8.68 kg) than Brahman (539.4 ± 8.68 kg) at 200 DOF (P < 0.05). The interaction for P8 and rib fat was due to all breeds having similar fat thickness at 0 DOF (P > 0.05) but Angus had greatest (21.38 ± 0.882 mm, 17.12 ± 0.549 mm), Brahman intermediate (16.73 ± 0.883 mm and 10.38 ± 0.550 mm) and Charolais thinnest (9.97 ± 0.966 mm, 7.23 ± 0.600 mm) P8 and rib fat, respectively, at 200 DOF (P < 0.05). Similarly, IMF was similar between breeds at 0 DOF (P > 0.05), but Angus had greater IMF (7.76 ± 0.287 %; P < 0.001) compared with Brahman (5.08 ± 0.287 %) and Charolais (5.18 ± 0.314 %), which were not different amongst them (P > 0.10). Results of the present study demonstrated the contrasting fat metabolisms of each genotype with Angus steers showing the fastest fat accretion rate for all fat depots, whereas Brahman steers showed intermediate and Charolais slowest subcutaneous fat accretion rate. However, both Brahman and Charolais steers showed similarly low IMF and kidney fat accretion rates. Fat accretion rate of each depot and whole body should be considered in mathematical simulation models of animal growth.

PSXII-18 The Probiotic Containing Bacillus Licheniformis and Bacillus Subtilis Improves Feed Efficiency in Beef Cattle

Abstract The aim of this study was to investigate the effects of a probiotic containing B. licheniformis and B. subtilis on fecal characteristics, blood parameters, and performance in feedlot cattle. One hundred and forty-four single-sourced Angus x Nellore bulls (initial shrunk BW = 401 ± 45.5 kg) were randomly assigned to 1 of 2 treatments (4 bulls per pen; 18 pen replicates per treatment). Treatments consisted of a finishing diet containing no probiotic (CONTROL) or a diet with 2 g of probiotic/bull/d (PROB). The probiotic was composed of B. licheniformis CH200 and B. subtilis CH201 (3.2 x 109 CFU/g; BOVACILLUS). The diet was formulated using NASEM (2016) to provide an ADG of 1.9 kg/d (23% of corn silage, 65% of ground corn, 8% of soybean meal, 1% of urea, and 3% of mineral mix; DM basis). Bulls were adapted to the finishing diet over a 15-d period and fed for a total of 84 d. Fecal samples were collected on d 33 and 63. Blood samples were collected on the day of shipping to slaughter. Statistical analysis of experimental data was performed using the MIXED procedure of SAS 9.4. An α of 0.05 determined significance and an α of 0.06 to 0.10 was considered a tendency. No differences were obtained for initial BW, final BW, ADG, hot carcass, and dressing. Dry matter intake was reduced by 4% (P = 0.002) and G:F was increased by 6.3% (P = 0.036) in bulls consuming PROB diet. Regarding blood parameters, no differences were observed for glucose, haptoglobin, and LBP. There was a tendency of greater plasma urea (P = 0.09) in bulls consuming CONTROL diets. Fecal characteristics (DM, starch, N, pH, and scoring) were not different between treatments. Overall, dietary supplementation with B. licheniformis and B. subtilis improves feed efficiency in feedlot cattle.

423 Effects of Prescribed Fire Timing on Stocker Cattle Performance and Native Plant Species Composition in the Kansas Flint Hills

Abstract Ranchers in the Kansas Flint Hills apply spring-season prescribed fire to improve growth performance of yearling stocker calves, increase native warm-season grass production, and reduce encroachment of woody and invasive plant species. Shifting prescribed fire application from spring (i.e., April) to late summer (i.e., August) or early fall (i.e., September) can reduce Sericea lespedeza infestation, increase native forb diversity, and improve air quality by distributing smoke produced from burning the Flint Hills throughout the year. Effects of late-summer or early-fall prescribed fire on yearling grazing cattle performance is unknown; therefore, our objective was to determine the impact of prescribed-fire timing on growth performance of yearling grazing cattle and plant community characteristics in the Kansas Flint Hills. Over a four-year period, 18 pastures were grouped by watershed and each watershed was assigned to one of three prescribed-fire treatments (24 pastures/treatment): spring (9 April ± 5.1 d), summer (23 August ± 4.9 d), or fall (29 September ± 8.7 d). Burn treatments were applied in years 1, 2, and 3 but were not applied in year 4 due to unfavorable burn conditions. Over 4 consecutive grazing seasons, 1,416 yearling calves (initial BW = 304 ± 49.6 kg) were grazed from May to August following prescribed fire application. Calves were grazed for 90 d at a targeted stocking density of 280 kg live-weight· ha-1. A permanent 100 m transect was established in each pasture and was used to determine plant species composition and soil cover using a modified step-point method. Plant species composition was determined annually in June. Data were analyzed as a completely random design using a mixed model. The final model contained treatment as a fixed effect and year and pasture within treatment as random effects. Average daily gain (ADG) tended to be greater (P = 0.06) for spring-burned pastures compared with fall-burned pastures, whereas ADG for summer-burned pastures were intermediate. Proportions of bare soil were greater (P < 0.01) in spring-burned pastures compared with summer- and fall-burned pastures. Conversely, proportions of litter on the soil surface were greatest (P < 0.05) in summer, intermediate (P < 0.05) in fall, and least (P < 0.01) in spring-burned pastures. Total grass, native grass, total forb, and native forb basal cover did not differ (P ≥ 0.13) among treatments. Conversely, basal cover of nectar-producing forbs was greater (P < 0.01) in fall-burned pastures compared with spring- and summer-burned pastures. Overall, fall prescribed-fire tended to reduce ADG; however, stocker cattle growth performance and native rangeland plant composition was similar between spring- and summer-burned pastures.

PSVI-12 Comparison of a Visual Health Scoring System with Vaginal Temperatures of Newly Received Feedlot Heifers

Abstract Newly received feedlot cattle frequently succumb to bovine respiratory disease (BRD), which can be visually diagnosed and medically treated by employing a 4-point scoring system based on depression, appetite, respiration, and temperature (DART). Using this system, cattle are treated with antimicrobial medications for BRD if they have a rectal temperature (RT) ≥ 40°C and a DART score of 2 (scale = 1 to 4), or if they have a DART score of 3 or 4 regardless of the 40°C RT threshold. However, cattle often exhibit several visible clinical symptoms of BRD but do not have an RT above the 40°C threshold to warrant medical treatment. The objective of this study was to evaluate if DART scoring could be used to identify cattle with elevated vaginal temperatures (VT) throughout a 28-day receiving period. Upon feedlot arrival, 198 crossbred heifers (primarily Angus influence; initial BW = 219 ± 63 kg) were initially processed, weighed, and allocated to one of 10 soil-surfaced pens (12 x 35 m; 20 heifers per pen). A blank Controlled Intravaginal Drug Release (CIDR) device attached with an indwelling temperature probe (iButton DS1925L) was inserted vaginally into each heifer to collect and store VT every 10 minutes for 28 days. All heifers were evaluated daily (0700 h) for signs of morbidity by three individuals (blinded from each other) implementing the DART scoring system. Individual DART evaluations were then pooled prior to determination of heifers needing further evaluation for medical treatment. Results confirmed that DART score increases as VT increases (P < 0.001). Similarly, mean time DART ≥ 2 (TDART≥2) increased as mean time VT ≥ 40°C (TVT≥40) increased (P < 0.001). Accuracy of DART ≥ 2 to VT ≥ 40°C analogous by day is denoted as (MATCH). Simple regression analysis of MATCH and TVT≥40 for determining accuracy of visually diagnosing clinical BRD, was MATCH = 0.89 – 0.71 × TVT≥40 (r2 = 0.70; P < 0.001). The accuracy to visually diagnose BRD decreases as the number of days spent with a VT ≥ 40°C increases. Average daily gain decreased (P < 0.001) as TDART≥2 and TVT≥40 increased. The BRD symptoms indicating high VT and DART score (P ≤ 0.01) were nasal discharge, anorexia, abnormal respiration, and teeth grinding. Additionally, weakness, cough, lowered head, and ocular discharge indicate greater DART score (P ≤ 0.01). Basophils and hemoglobin decreased with elevated VT and DART score (P ≤ 0.02). Monocytes increased with increased DART score (P ≤ 0.04). In conclusion, data from this evaluation employing VT sensors and the DART scoring method provided an overview of how effective clinical BRD can be visually diagnosed, therefore contributing to the improvement and development of more effective strategies for identifying respiratory diseases in feedlot cattle.

PSXIII-18 Feeding One-Year Stored Sorghum Silage: Effects of Grain Processing on Intake and Apparent Total Tract Digestibility of Backgrounding Beef Heifers

Abstract This study evaluated the effect of feeding sorghum silage after one-year of storage (SS) based diets, on dry matter intake and nutrient digestibility of beef cattle. A dual-purpose sorghum (ADV2450IG, Advanta seeds, Irving, TX) was harvested (Claas Jaguar 930, Harsewinkel, Germany) at the late-dough stage of grain maturity and processed (PRO) or not (NPR) with a specific SS cracker (196 mm rolls of 125 teeth each, 40% speed differential, 1.1 mm roll gap). Whole-plant was chopped at 15 mm and ensiled in polyethylene ag-bags (60 m long and 2.74 m diameter), for 388 d until the beginning of a 60 d-performance trial which was followed by the digestibility trial. From a performance trial with eight heifers/pen, and 12 total (six per treatment), one heifer (13.5 ± 1 mo and 259,4 ± 38 kg of BW) by pen was randomly selected for the digestibility trial. Two backgrounding diets containing (DM basis), 90.5% SS either PRO or NPR, 6.5% soybean meal (expeller) and 3% supplement (ROC90, Provimi, Argentina); continued to be offered ad libitum for an extra 3 d of adaptation while feed and feces were collected the next 4 d. Feed was individually offered once daily, and orts were collected the following day. Fecal samples were collected twice daily and apparent total tract digestibility (TTD) was determined using uNDF240h as a marker. Data were analyzed as a completely randomized design using pen as the experimental unit, and initial BW as a covariate. No differences among treatments were detected for DM, OM, NDF, ADF, CP and starch intake (P > 0.35). No effects of treatment were observed (P > 0.40) for DM, OM, NDF, ADF, CP and starch TTD. In conclusion, no effects of processing on apparent total tract digestibility were detected when feeding a one-year stored sorghum silage to backgrounding beef heifers.

PSX-12 Effects of Cottonseed Meal Supplementation on Calf Performance and Forage Utilization Grazing Late Season Summer Forage

Abstract Nutritive quality of perennial warm-season grasses during summer may limit the DMI of growing calves due to low protein and increased NDF content. Cottonseed meal (CSM) supplementation may improve forage utilization by increasing rumen degradable protein, but research in calves is limited. It was hypothesized that supplementation of CSM to heifers grazing mature forage would have improved performance due to greater forage DMI and fiber digestibility. Objectives were to compare the effects of CSM supplementation on calf gain performance, estimated forage intake, and in vitro true digestibility (IVTD) and neutral detergent digestibility (IVNDFD) of low-quality, warm-season forage. Angus heifers (n = 18) weighing 232.7 ± 12.6 kg were blocked by BW (light, medium, and heavy) and allocated to 6 paddocks (1.64 ha) of W.W. B-Dahl Bluestem (Bothriochloa bladhii) for 67 d. Heifers were supplemented daily with a mineral mix and either no cottonseed meal (CON) or 454 g/animal of CSM (CSM1) in a RCBD with a 2×3 factorial arrangement of treatments and BW blocks, respectively. Initial and final shrunk BW was measured to calculate total gain, ADG, and percent of BW gained. Forage samples were collected weekly and composited into 3 periods for chemical analysis and in vitro incubations. Forage DMI was estimated using a double sampling technique for each paddock within period. Forage IVTD and IVNDFD were analyzed using batch fermentation with and without CSM in a CRD (2 treatments by 3 periods). Mean forage CP during periods 1 and 2 were 5.75% and increased to 10.3% in period 3 (P < 0.01). Forage NDF content increased over time (64.1 vs. 69.3%; P < 0.01) and estimated forage DMI of heifers tended (P = 0.07) to decrease from 2.9 to 2.1% of BW. Treatment did not affect estimated forage DMI (P = 0.40). Heifers receiving CSM1 gained 28.3% more BW than heifers receiving CON (47.27 vs. 36.82 kg, respectively; P = 0.02). Percent of BW gained was greater for heifers receiving CSM1 than CON (16.9 vs. 13.8% of initial BW, respectively, P = 0.029). There were no treatment by period interactions on IVTD or IVNDFD. The IVTD of forage from period 1 was greater than periods 2 and 3 (49.9 vs. 47.1 and 46.6%, respectively; P = 0.005). The IVTD of forage incubated with CSM tended (P = 0.06) to be greater than forage without CSM (52.1% vs. 47.8%, respectively). The IVNDFD was not affected by period but tended to be greater with CSM inclusion (P = 0.09) relative to CON (24.83% vs. 18.95%, respectively). In conclusion, 454 g/d of CSM supplemented to heifers grazing late-summer W.W. B-Dahl Bluestem forage likely provided sufficient protein to alter ruminal fiber digestibility, without affecting forage intake, and had measurable effects on gain.

262 Weaning-Induced Changes in Tissue Cysteine Utilization in Pigs

Abstract Weaning stress in pigs is associated with low and variable feed intake, poor nutrient utilization, and high feed costs. Cysteine is a sulfur amino acid with key roles in pig production, but how cysteine metabolism and requirements are affected by weaning stress should be better defined. The objective of this study was to determine weaning-induced changes in tissue cysteine metabolism. Pigs (initial BW = 7.23 ± 0.68 kg) were either weaned at 21 d age and euthanized at 23 d age (W; n = 9) or remained with the sow and euthanized at 23 d age (NW; n = 9). Weaned pigs were fasted to simulate acute nutritional stress but had free access to water. At euthanasia, blood, liver, jejunum, and ileum tissues were collected. Plasma and tissue amino acids and amino thiols were analyzed by HPLC. The abundance of proteins central to liver cysteine utilization were determined by immunoblot and enzyme activity assays. Glutathione (GSH) concentrations were less in jejunum (1,379 versus 1,720 ± 70 nmol/g; P < 0.01) and ileum (1,497 versus 1,740 ± 74 nmol/g; P < 0.05) in W than NW pigs. However, liver GSH concentration was not different between W and NW pigs (P > 0.10). While cysteine in jejunum and ileum were not affected by weaning (P > 0.10), γ-glutamylcysteine (γ-GC), the immediate precursor of GSH, declined in both jejunum (9.7 versus 14.3 ± 1.4 nmol/g; P < 0.01) and ileum (6.4 versus 11.2 ± 0.8 nmol/g; P < 0.001) in W compared with NW pigs. In liver, cysteine concentration was greater in W compared with NW pigs (417 versus 298 ± 33 nmol/g; P < 0.05). Although liver cysteine was greater in W pigs, liver activity of glutamate cysteine ligase (GCL; 2.49 versus 4.15 ± 0.25 nmol γ-GC/(mg protein•min); P < 0.001) and glutathione synthetase (GSS; 1.54 versus 1.92 nmol GSH/(mg protein•min); P < 0.001), enzymes needed for GSH production, were less in W than NW pigs. Immunoblot analysis of the catalytic subunit of GCL (GCLC; P < 0.05) and modifier subunit of GCL (GCLM; P = 0.057) were also lower in W compared with NW pigs, but GSS was not different between groups (P > 0.10). While plasma taurine was lower in W compared with NW pigs (64 versus 128 ± 7 µmol/L, P < 0.001), liver taurine was greater in W compared with NW pigs (4,726 versus 2,250 ± 471 nmol/g; P < 0.01). Despite an increase systemic and liver availability of cysteine, the rate-limiting amino acid for GSH synthesis, small intestine GSH concentrations decline. This suggests that systemic cysteine is not effectively utilized for gut GSH production in pigs after weaning.

242 Methionine and Guanidinoacetic Acid Supplementation During the Periconceptual Period of Gestation Shifts Methionine Metabolism of Fetal Bull Calves at D 63 of Gestation

Abstract Recent research has demonstrated that feeding rumen protected methionine (MET) products increases circulating methionine while feeding guanidinoacetic acid (GAA) may result in a methyl deficiency. Therefore, we hypothesized that maternal MET or GAA supplementation from 63 days before breeding until d 63 of gestation would increase fetal hepatic methyl donors or result in a fetal hepatic methyl donor deficiency, respectively. Eighty MARC II heifers (n = 20 per treatment; initial BW = 344 ± 8 kg; day -63) were weighed and assigned to one of four breeding groups and four treatments stratified by age and starting weight. Heifers were fed a total mixed ration to gain 0.68 kg/d and received 100 g of one of four treatments top dressed: control supplement of ground corn (CON), MET (10 g/d) in a ground corn carrier, GAA (40 g/d) in a ground corn carrier, or MET + GAA (10 g/d MET + 40 g/d GAA) in a ground corn carrier. At breeding (d 0), all heifers were bred to a single sire using male sexed semen. At d 63 of gestation, 35 heifers (CON n = 10, MET n = 8, GAA n = 7, MET + GAA, n = 10) confirmed pregnant with bull calves were humanely slaughtered and fetal liver tissues were collected and sent to Metabolon Inc. for global metabolomics analysis. Data were analyzed as a 2 x 2 factorial with 2 levels of GAA and 2 levels of MET with breeding group included in the model. For this abstract, only metabolites from the methionine cycle and adjacent pathways will be reported and only metabolites with significant P-values will be discussed (P ≤ 0.05). There were no main effects or interactions for the abundance of methionine, GAA, creatine, SAM, SAH or homocysteine. Glycine was decreased and sarcosine increased in fetuses from MET supplemented dams. Serine was affected by a MET x GAA interaction being decreased in livers of CON, MET, and MET + GAA fetuses compared with GAA. Cystathione, S-methylcysteine, s-methylcysteine sulfoxide, and hypotaurine were greater in fetuses of MET supplemented heifers and pyridoxal phosphate was reduced in fetal liver of MET supplemented heifers. The abundance of urea was greater in GAA supplemented fetuses. These results indicate that fetuses from dams fed methionine may be able to maintain balance in methionine supply by shunting methionine through adjacent pathways including the transsulfuration pathway. We also interpret these data to imply that excess methionine is not utilized by the fetus and is metabolized to products that can be excreted. Lastly, GAA did not alter the fetal methyl supply. USDA is an equal opportunity provider and employer. Funded by (USDA-NIFA-AFRI # 2022-67015-36196).

PSVIII-A-2 How Does the Duration of Low Feed Intake Affect the Ruminant Gastrointestinal tract?

Abstract The objective of this study was to determine the effect of 5 and 10 d low feed intake (LF) on the ruminant gastrointestinal tract (GIT). Twelve rams and nine wethers were used in a randomized complete block design where they were blocked by castration status and BW. After 5 d of ad libitum feeding, lambs were either exposed to 0 (CON; 100% DMI; n = 7), 5 (LF5; 30% DMI; n = 7), or 10 d (LF10; 30% DMI; n = 7) of LF. At the end of the study, lambs were euthanized, the GIT was removed to determine the digesta and tissue weights by region and the weights of the liver, spleen, and kidneys were recorded. There were no castration × treatment interactions (P ≥ 0.32). Initial (P = 0.97) and final (P = 0.19) BW did not differ by treatment. The weight of the reticulo-ruminal tissue tended to be less (P = 0.06) for LF10 than CON, with LF5 being intermediate but not different. Ruminal digesta weight was not affected (P = 0.98). Omasal tissue weight did not differ among treatments (P = 0.24), but digesta weight tended (P = 0.07) to be greater for CON compared with LF10 and LF5. Abomasal tissue weight was reduced for LF10 (P = 0.04), with LF5 being intermediate but not different. Abomasal digesta weight was less for LF5 and LF10 than CON (P = 0.04). The weight of the duodenum tended (P = 0.08) to be greater for CON than LF10 and LF5, but digesta weight was not affected (P = 0.16). For the jejunum, tissue and digesta weight tended (P = 0.07) to be greater for CON than LF10, with LF5 being intermediate. The weight of the ileum tended to be the greatest for CON, intermediate for LF5, and the least for LF10 (P = 0.10), but digesta weight was not affected (P = 0.81). Cecal tissue weight was not affected by treatment (P = 0.89); whereas digesta weight was the greatest (P = 0.03) for LF10, the least for CON, and intermediate but not different for LF5. In contrast, colonic tissue weight was less for LF10 relative to LF5 and CON (P = 0.01) and digesta weight tended (P = 0.05) to be greater for CON than LF5 and LF10. Liver weight was reduced (P < 0.01) for both LF5 and LF10 relative to CON, but kidney and spleen weights were not affected (P ≥ 0.33). This study indicates that exposing ruminants to LF rapidly reduces the weights for regions of the GIT and liver. These changes likely implicate a reduced absorptive capacity of the GIT and a lesser metabolic capacity of the liver.

PSVI-24 A Phytogenic Feed Additive Improves Performance By Nellore Growing Bulls Grazing on Tropical Pastures

Abstract Our objective was to evaluate the effect of including a phytogenic additive in protein supplement on performance of grazing Nellore bulls during growing phase in the rainy season. One hundred and fourteen animals (iBW, 273 ± 4.46 kg) were allocated for 152 days in six paddocks of Brachiaria brizantha cv. Marandu (~7 ha each), with automatic feeders and scales (in drinkers, Intergado, Brazil); and randomly distributed in six treatments fed on protein supplement (30% Crude protein): 1) Negative Control (CON), with no additive; 2) Monensin (MON; positive control, 15 ppm) 3) Digestarom (DSM Nutritional Products) at 0.2 g· animal-1· /day-1 (D0.2); 4) Digestarom at 0.4 g· animal-1· /day-1 (D0.4); 5) Digestarom at 0.6 g· animal-1· /day-1 (D0.6) and 6) Digestarom at 0.8 g· animal-1· /day-1 (D0.8). Supplement offered and additives inclusion were adjusted weekly, based on the intake of the previous week. Supplement intake (SI, measured by the automatic feeders) and Average Daily Gain (ADGs; measured subtracting final and initial fast BW, divided by 152 days; and ADGf; measured by the automatic scales) were evaluated during this study. Data were analyzed by SAS PROC GLIMMIX and significance of 5% was adopted. Means of Digestarom levels were compared with the CON and MON, and of the MON was compared with the CON using a Dunnett test. MON reduced (P < 0.05) SI (175 g/d) compared with CON (433 g/d) and all Digestarom levels (423, 303, 468 and 332 g/d respectively). D0.4 and D0.8 also reduced SI when compared with CON. The ADGs and the ADGf of animals on D0.6 (927 and 1.262 g/d) were greater (P < 0.05) compared with CON (0.860 and 1.127 g/d) and MON (0.840 and 1.114 g/d). The other levels of Digestarom [D0.2 (0.886 and 1.107 g/d), D0.4 (0.823 and 1.054 g/d), and D0.8 (0.853 and 1.071 g/d)] did not differ from CON and MON. D0.6 did not reduce SI (compared with CON; P > 0.05) and increased ADGs and ADGf (compared with CON and MON; P < 0.05). Feeding Digestarom at the dose of 0.6 g· animal-1· /day-1 may increase BW gain of grazing growing bulls during rainy season.

354 Effect of Finishing System on Growth, Efficiency, and Carcass Quality of Dairy × Beef Hybrids

Abstract Our objective was to determine how calf-fed or yearling finishing systems affect the performance and efficiency of dairy-beef crossbred steers. Dairy-beef hybrid steers were acquired from Land O’ Lakes Calf Milk Research Facility at Grey Summit, Missouri at 12-wk (BW /SD) of age and transported to Willard Sparks Beef Research Center (WSBRC). Upon arrival at WSBRC, steers were weighed, vaccinated, treated for parasites, and implanted with 36 mg of zeranol (Ralgro). Alternating groups of steers were placed either directly on finishing diets (FIN) or on high-quality pasture and supplementation for 5 to 6 mo before returning to WSBRC for finishing (GRW/FIN). Steers in FIN were grown on successively higher energy growing diets through d 112, stepping up to a 20% roughage growing diet from d 28 to 112. On d 112, FIN steers were transitioned to a 12% roughage finishing diet. A final 8% roughage finishing was fed to FIN steers from d 224 to slaughter. Steers in FIN were reimplanted with Ralgro on d 56, Component TE-IS (80 mg trenbolone acetate, 16 mg estradiol, and 29 mg tylosin tartrate; Elanco US, Greenfield, IN) on d 112, and Component TE-S (200 mg progesterone, 20 mg estradiol benzoate, 29 mg tylosin tartrate; Elanco) on d 224. Steers in GRW/FIN were returned to WSBRC, weighed, and processed when they reached 312 ± 7.0 kg. Steers in GRW/FIN were implanted with Component TE-IS at the start of finishing, and Component TE-S on d 120. Steers in GRW/FIN were stepped up to the finishing diet when they reached 407 ± 6.0 kg. Finishing diets for the final 28 d for FIN and GRW/FIN included ractopamine hydrochloride at a rate of 300 mg·steer-1·d-1. At WSBRC, steers within each finishing system were sorted by BW into 4 to 5 head pens. Initial and terminal BW were greater (P < 0.01) in steers in the GRW/FIN finishing system. Body weight at reimplant was greater (P < 0.01) for FIN. Steers in the GRW/FIN system were on feed for fewer (P < 0.01) days compared with FIN steers. Average daily gain (ADG) and DMI (kg·steer-1·d-1) were greater (P < 0.01) for GRW/FIN. Steers in GRW/FIN had a greater (P < 0.02) feed:gain ratio than those placed directly into a finishing system. There were no differences (P < 0.10) in USDA Yield Grade, marbling, ribeye area (REA), or back-fat thickness (BFT) between finishing systems. Steers in FIN had a greater (P < 0.01) dressing percentage (DP) and lighter (P < 0.01) hot carcass weight than those for GRW/FIN. Finishing system has an impact on performance and efficiency of dairy-beef hybrid steers, but minimal impact on carcass quality.

PSIX-22 Performance, Digestibility, and Blood Parameters in Pregnant Beef Cows Fed Total Mixed Ration Silages

Abstract The aim of this study was to investigate the effects of two total mixed ration (TMR) silages (low and high rumen undegradable protein; RUP) on digestibility, blood parameters, and performance in pregnant beef cows. Thirty-three mid-gestation (~130 d of gestation) Tabapua beef cows were randomly assigned to 1 of 2 treatments: 1) a TMR silage containing Brachiaria grass, soybean hulls, urea, and mineral mix (low RUP; n = 16) or 2) a TMR silage containing Brachiaria grass, DDG, and mineral mix (high RUP; n = 17). The concentration of A1 fraction was, on average, 12.9% and 34.0% of N in low and high RUP silages, respectively. A preservative with a blend of organic acids, surfactants, and activated propionates was applied in both silages. Pressed bag silos were used to conserve silages for 7 wk. Cows were housed in individual pens for 100 d. During a 4-d digestion period (at 50 d of housing), fecal samples were collected for measurement of nutrient digestibility using undigested neutral detergent fiber as a marker. Blood parameters were collected at the last day of housing. Statistical analysis of experimental data was performed using the GLM procedure of SAS 9.4. Diet, calf sex (male or female), and interactions between these factors were considered fixed effects. No differences were obtained for initial BW. High RUP diet showed greater final BW (P = 0.0004) and ADG (P = 0.0003). Cows fed high RUP gained 50 g/d, while cows fed low RUP diet lost 445 g/d. Dry matter intake was greater by 23% (P < 0.0001) in cows consuming high RUP silage. Dry matter, CP, and NDF digestibility did not differ between treatments. Regarding blood parameters, no differences were observed for glucose at 0 h and 4 h post-feeding. Plasma urea at 0 h post-feeding was greater in cows fed low RUP silage (P = 0.0003). However, no differences were observed for plasma urea at 4 h post-feeding. The plasma concentrations of non-esterified fatty acids (P = 0.017) and beta-hydroxy-butyric acid (P = 0.002) were greater in cows consuming low RUP diet. Overall, feeding pregnant cows during mid-gestation with TMR silage containing high RUP promotes greater performance.

PSXIV-1 Impact of Slow-Release Nitrogen Or Regular Protein-Based Supplementation During Late Gestation on Maternal and Offspring Performance in Beef Cattle

Abstract The objective of this study was to determine whether supplementing pregnant beef cows with regular nitrogen or a slow-release nitrogen source at the late gestation could enhance the use of a low protein basal diet and improve the performance of cows and their offspring until weaning. Thirty-five pregnant Brahman cows (556 ± 47 kg and 4.5 ± 1.4 years old) were individually housed in covered pens and randomly divided into three groups. From 180 ± 19 days of gestation until calving, cows were fed either a control (CON, n = 12) low crude protein (CP) basal diet (6% of CP, ad libitum) plus mineral mixture (130 g·cow-1·d-1), or the CON treatment supplemented with protein concentrate supplements (40% CP, fed 2 g·kg of BW-1·d-1 in the morning) based either on a regular (REG, n = 11) composition (corn, soybean meal, and urea) or on a slow-release N (SRN, n = 12) source (Timafeed Boost, Roullier Group, Saint-Malo, France) which replaced 60% of soybean meal and urea in the supplement composition. The MN, fetal sex (FS), and MN×FS were used as fixed effects in the statistical model, while the number of previous calvings was considered as a random effect. Maternal initial BW was used as a covariate. Statistical differences were declared at P < 0.05. Supplementation with REG and SRN increased total dry matter intake (DMI) and basal diet intake compared with the control treatment (P < 0.01). Protein supplementation allowed the cows to have a higher average daily gain (P < 0.01; 0.177 and 0.193 kg/day, respectively, for REG and SRN) than the CON treatment (-0.255 kg/day). Body condition score (BCS) also increased (P < 0.01) when cows received protein supplementation in late pregnancy, but with no differences between REG and SRN cows (P = 0.31). Interactions between MN and FS were observed for calf birth weight (CBW, P < 0.01) and calves' average daily gain up to 120 days of age (ADG120, P = 0.01), but not at weaning weight (P = 0.69). Male calves born from REG and SRN cows were born heavier and gained more weight up to 120 days after birth than calves born from CON cows (P < 0.05) but did not differ from each other (P = 0.94 and 0.92, respectively, for CBW and ADG120). Female calves had no differences in CBW and ADG120 as a function of maternal dietary treatment during pregnancy. The REG and SRN calves weaned heavier (P < 0.05) than CON calves. In conclusion, supplementing protein to pregnant beef cows during periods of low CP pasture improves maternal and progeny performance. The SRN-based product can replace the major part of soybean and urea in the protein supplement, achieving same level of improvement in forage utilization and animal performance as the regular protein-based supplement.

PSI-6 Effects of a Postbiotic Program Consisting of Liquid and Solid Saccharomyces Cerevisiae Fermentation Products on Digestibility, Ruminal Fermentation, and Plasma Metabolome of Finishing Beef Steers

Abstract The objective of this study was to determine the effects of a postbiotic feeding program consisting of liquid and solid Saccharomyces cerevisiae fermentation products (SCFP) on digestibility, ruminal fermentation, and plasma metabolome of finishing beef steers. Eight Holstein steers (BW 467 ± 13.9 kg) equipped with rumen cannulas were used in a crossover design study, with 21-d per period and 7-d washout period in between periods. Steers were blocked based on initial BW to one of two treatments: 1) Control, basal diet only (CON), or 2) SCFP, one day feeding of LiquiCare RTU (Diamond V, dosed via rumen cannula at 11 mL/100 kg BW) followed by daily feeding of 12 g NaturSafe (Diamond V, top-dressed). Feed and fecal samples were collected during d 17 to 20 for determination of digestibility and fecal excretion of N, P, Cu and Zn using acid-insoluble ash as an internal marker. Blood samples were collected on d 21 before morning feeding. Rumen fluid samples were collected on d 0, 1, 2, 3, 5 and 21 at 0, 4, 8, or 12 h post morning feeding via rumen cannula. Results were analyzed with the GLIMMIX procedure of SAS 9.4 (SAS, 2022). BW, DMI and digestibility were not affected by treatment. There was a tendency of treatment by period interaction (P = 0.09) on feed efficiency, which was improved by feeding SCFP only in period 1. Feeding SCFP did not affect (P > 0.10) ruminal pH. Feeding SCFP tended to reduce ruminal lactate concentration on d 21 (0.09 vs. 0.02 mM, P = 0.10). Supplementing SCFP reduced ruminal NH3-N concentration on d 2 (4.24 vs. 7.31 mg/dL, P = 0.03) and d 21 (4.86 vs. 6.83 mg/dL, P = 0.04). By feeding SCFP, ruminal total VFA concentration was increased 4-h post-feeding on d 5 (139.7 vs. 126.7 mM, P = 0.01) and numerically increased 4-h post-feeding on d 21 (151.2 vs. 133.3 mM, P = 0.12). For VFA composition, no treatment differences were observed on day 21. However, feeding SCFP reduced (P = 0.01) propionate proportion and increased (P = 0.05) butyrate proportion on day 3. The enriched plasma metabolic pathways (P ≤ 0.05) by feeding SCFP are citric acid cycle, pyrimidine metabolism, glycolysis/gluconeogenesis, retinol metabolism, and inositol phosphate metabolism pathways. Overall, our results indicated potential benefits of the SCFP feeding program on improving ruminal fermentation, preventing acidosis and improving N utilization in the rumen. Furthermore, feeding SCFP enriched several important pathways in lipid, protein, and glucose metabolism, which may improve feed efficiency of energy and protein in finishing beef cattle.

PSI-17 Use of Sunn Hemp as Forage for Early-Weaned Beef Calves

Abstract Sunn hemp (Crotalaria juncea) has been widely used as cover crop in the USA and due to superior biomass accumulation and nutritive value, there is interest from producers to use sunn hemp as forage for livestock. However, sunn hemp has pyrrolizidine alkaloids, which can affect animal performance. The objective of this study was to evaluate the effects of feeding sunn hemp hay to early-weaned beef calves in a dry lot in Florida. The experiment was conducted at the UF/IFAS Range Cattle Research and Education Center, Ona, FL from April to May 2021 (42 d). Treatments were calves receiving sunn hemp or stargrass (Cynodon nlemfuensis) hay distributed in a randomized complete block design with 12 replicates. Calves were supplemented with concentrate at 1.3% BW daily (18% CP and 78% TDN). Twenty-four Angus crossbred calves were weaned with 90 ± 14 kg BW and grazed annual ryegrass (Lolium multiflorum) with 1% BW concentrate supplementation for approximately 60 d. Subsequently, calves were randomly distributed and assigned to experimental units (pen) on 14 April 2021 with initial BW of 184 ± 10 kg. ‘Ubon’ sunn hemp hay was harvested approximately 49 d after seeding when 75% of the plants were initially flowering. Ground hay was fed daily targeting 10% refusals, and the initial CP and in vitro digestible organic matter concentrations of sunn hemp and stargrass hay were 9 and 48%, and 9 and 47%, respectively. The average concentration of pyrrolizidine alkaloids from sunn hemp hay was 58 μg/g DM. Early-weaned calves receiving stargrass had a tendency to have greater ADG than sunn hemp (0.5 vs. 0.4 kg/d, P = 0.09), and had greater forage DM intake (1.2 vs. 1.0% BW, P < 0.01) and total DM intake (2.5 vs. 2.3% BW, P < 0.01). Conversely, diets with sunn hemp had greater in vivo DM digestibility than stargrass (68 vs. 62%, P = 0.04). There was no difference between treatments on parasite egg count (mean = 45 eggs/3 g feces, P = 0.25) and coccidia egg count (log10 eggs/g feces, P = 0.35). Early-weaned calves receiving sunn hemp consumed 0.25 g pyrrolizidine alkaloids/d; however, there was no detectable amount (< 0.05 μg/g DM) of pyrrolizidine alkaloids in the feces. The presence of pyrrolizidine alkaloids in sunn hemp may be the potential cause of decreased early-weaned calves forage intake and animal performance.

105 The Effects of Roughage Neutral Detergent Fiber Concentration and Bulk Density of Steam-Flaked Corn on Performance, Carcass Characteristics, and Liver Abscesses in Finishing Beef Steers

Abstract We evaluated the effects of dietary neutral detergent fiber (NDF) concentration from alfalfa hay and bulk density of steam-flaked corn (SFC) on growth performance, carcass characteristics, and liver abscesses in finishing beef steers. Crossbred beef steers (n = 214; 60 pens; 10 pens/treatment; initial BW 417 ± 11.9 kg) were blocked by BW and assigned randomly to treatments and fed an average of 112 d. The treatments were arranged as a 2 × 3 factorial and consisted of three NDF concentrations from alfalfa hay (3, 4.5, or 6%) and 335 g/L (10.9 kg/bu) or 425 g/L (14.5 kg/bu) steam-flaked corn (SFC; 33 or 69% starch availability, respectively). Steers were harvested at a commercial abattoir where carcass data and livers scores were collected. Performance and carcass data were analyzed with PROC MIXED of SAS with pen as the experimental unit. Pen quality grade distribution and liver scores were analyzed as binomial proportions using PROC GLIMMIX. No interactions between roughage NDF and bulk density of SFC were noted (P > 0.18); therefore, main effects are presented. Live and carcass-adjusted growth performance did not differ throughout the study (P ≥ 0.28), except for an increase in dry matter intake by steers fed 6% vs. 3 or 4.5% roughage NDF from d 70 to 105 (P = 0.02). Marbling score was greater (P = 0.05) for steers fed 3% than for 4.5 or 6% roughage NDF, and steers fed 335 g/L SFC tended to have a larger longissimus muscle area (P = 0.10) than those fed 425 g/L SFC. Presence of LA at harvest was 17.9 and 23.4% less (P < 0.01) in the steers fed 4.5 and 6% roughage NDF, respectively, than for those fed 3% roughage NDF. Similarly, the presence of A+ abscesses was greater (P = 0.03) in steers fed 3% roughage NDF than in those fed 4.5 or 6% roughage NDF. Liver abscesses were 11.7% less (P = 0.05) in steers fed 425 vs. 335 g/L SFC. Results suggest that increasing roughage NDF and bulk density of SFC are dietary strategies to decrease the presence of liver abscesses at harvest without negatively affecting growth performance.

Phosphorus equivalency of exogenous phytase relative to phosphorus in monosodium phosphate in broiler chickens

The objective of this study was to estimate phosphorus (P) equivalency of exogenous phytase relative to P from monosodium phosphate (MSP) in broiler chickens. To attain this objective, the impact of dietary MSP or exogenous phytase on growth performance, ileal digestibility of P, and bone characteristics in broiler chickens was assessed. Six experimental diets consisting of a P-deficient basal diet based on corn and soybean meal, basal diet plus 0.9 or 1.8 g/kg of inorganic P from MSP, and basal diet plus 500, 1,000, or 2,000 FYT/kg of exogenous phytase. Calcium to P ratio in all diets was maintained at 1.5:1. A total of 576 male broiler chickens (Cobb 500; initial BW=190 ± 17 g) on d 8 post hatching were allotted to the 6 dietary treatments in a randomized complete block design using BW as a blocking factor. Each dietary treatment contained 8 replicate cages with 12 birds per cage. On d 11 post hatching, 7 birds from each cage were euthanized by CO2 asphyxiation and dissected for the collection of ileal digesta. On d 18, ileal digesta were also collected from the remaining 5 birds in each cage. The left femur and tibia were collected from the bird with the median BW on d 11 and 18 from each cage, and analyzed for bone breaking strength and bone ash. Weight gain and gain-to-feed ratio linearly or quadratically increased (P < 0.05) in every period as the inclusion rate of MSP or phytase increased. Ileal digestibility of P linearly increased (P < 0.05) on d 11 with increasing MSP, but there was no significant effect on d 18. Increasing phytase concentration linearly increased (P < 0.05) ileal digestibility of P on d 11 and 18. Increasing dietary MSP or phytase linearly increased ileal digestible P concentration in diets (P < 0.05). Bone breaking strength and bone ash linearly or quadratically increased (P < 0.05) with increasing inclusion rate of MSP or phytase on d 11 and 18. The equivalency of 1,000 FYT/kg of exogenous phytase based on dietary ileal digestible P concentration was 1.5 and 1.2 g/kg of inorganic P in diets on d 11 and 18, respectively. The current results showed that the supplementation of MSP or exogenous phytase can increase growth performance, ileal P digestibility, bone breaking strength, and bone ash in young broiler chickens.

163 Effect of Enogen Feed Corn Inclusion in Conventional and Natural Finishing Cattle Diets

Abstract A finishing experiment was conducted to determine the effects of Enogen Feed Corn inclusion in comparison with a control corn hybrid within natural and conventional feeding programs on finishing performance. The experiment used 400 crossbred steers (initial BW = 384 ± 33 kg) and 200 crossbred heifers (initial BW = 330 ± 19 kg) in a 2×2 factorial arrangement of treatments with 10 replications of steers and 5 replications of heifers per treatment. Factors were Enogen Feed Corn (EFC) or control corn hybrid inclusion as dry-rolled corn and corn silage within conventional and natural feeding programs. Cattle assigned to the conventional program were fed rations that contained feed additives and received implants whereas cattle in the natural program received neither. Performance data were analyzed as a 2×2×2 factorial assessing interactions between sex, feeding program, and corn hybrid inclusion. A sex by feeding program by corn hybrid (P = 0.01) interaction was observed for dry matter intake (DMI). Interactions between sex and feeding program were observed for carcass adjusted final BW (final BW; P &amp;lt; 0.01), average daily gain (ADG; P &amp;lt; 0.01), feed efficiency (G:F; P &amp;lt; 0.01), and hot carcass weight (HCW; P = 0.01). No significant corn hybrid by sex interactions (P ≥ 0.12) or corn hybrid by feeding program interactions (P ≥ 0.13) were observed. Inclusion of EFC in natural heifer diets tended to increase DMI by 0.4 kg/d (P = 0.10), while hybrid inclusion had no impact on DMI of conventional heifers. Feeding EFC in conventional steer diets tended to increase DMI by 0.4 kg/d (P = 0.06) compared with steers consuming the control corn hybrid diet. Corn hybrid had no impact on DMI in natural steer diets (P = 0.15). Carcass adjusted final BW decreased by 75 kg in natural steers and 41 kg in natural heifers compared with conventional programs (P &amp;lt; 0.01). Natural heifers gained 0.24 kg/d less than conventional heifers (P &amp;lt; 0.01). Feeding steers in the natural program reduced ADG by 0.43 kg/d in comparison with conventional program steers (P &amp;lt; 0.01). Compared with natural cattle, G:F improved by 13.0% when heifers were fed in a conventional program (P &amp;lt; 0.01) and 19.4% when steers were fed in a conventional program (P &amp;lt; 0.01). Feeding program had no effect on marbling (P = 0.38) while conventional cattle had greater 12th rib fat than natural cattle (P &amp;lt; 0.01). Inclusion of EFC had no effect on ADG (P = 0.71), G:F (P = 0.22), or HCW (P = 0.57). The incorporation of implants and feed additives within the finishing period increased final BW, HCW, and ADG leading to improved G:F in steers and heifers, with the improvement being greater in steers.

251 Effects of Fat Source and Level on Growth Performance and Carcass Characteristics of Commercial Finishing Pigs

Abstract Two experiments evaluated different fat sources and levels on growth performance and carcass characteristics in commercial finishing pigs. In Exp. 1, pigs (n = 2,160 337 × 1050, PIC; initial BW 37.3 ± 0.93 kg) were used. Pens of pigs were blocked by initial BW and randomly assigned to 1 of 4 dietary treatments. Three of the treatments included: 0, 1, and 3% choice white grease fed throughout the trial. The final treatment contained no added fat until pigs were approximately 100 kg, and then the diet containing 3% fat was fed. Experimental diets were fed over 4 phases and were corn-soybean meal-based with 40% dried distillers grains with solubles. There were 27 pigs per pen and 20 replications per treatment. Overall, increasing choice white grease decreased (linear, P = 0.006) ADFI and increased (linear, P = 0.006) G:F without influencing ADG (Table 1). Pigs fed 3% fat only during the late finishing phase (approximately 100 to 129 kg) had similar G:F compared with pigs fed 3% fat for the entire study. Increasing fat tended to increase (linear, P = 0.068) HCW. In Exp. 2, pigs (n = 2,011 PIC 1050 × DNA 600; initially 28.3 ± 0.53 kg) were used. Pens of pigs were blocked by location in the barn and randomly assigned to 1 of 5 dietary treatments arranged in a 2 × 2 + 1 factorial with main effects of fat source (choice white grease or corn oil) and level (1 or 3% of the diet) and a control diet with no added fat. There were 16 replications per treatment with 21 to 27 pigs per pen. Overall, increasing fat, regardless of source, increased (linear, P &amp;lt; 0.001) ADG, decreased (linear, P = 0.013) ADFI, and increased (linear, P &amp;lt; 0.001) G:F. Increasing fat increased (linear, P ≤ 0.016) HCW, carcass yield, and backfat depth (Table 2). There was a fat source × level interaction (P &amp;lt; 0.001) in belly fat iodine value (IV), where IV increased to a greater extent in pigs fed diets containing corn oil with only a small increase in IV in pigs fed diets with choice white grease. In conclusion, the results from these experiments suggest that increasing fat from 0 to 3%, regardless of source, produced variable responses in ADG but consistently improved G:F. Increasing fat increased HCW, carcass yield, and backfat depth, but feeding diets containing corn oil increased belly fat IV to a greater magnitude than choice white grease.

299 Poultry Meal Autoclaving Time-Related Reduction in Amino Acid Digestibility for Broiler Chickens and Growing Pigs

Abstract Poultry meal (PoMe), a rendered product of slaughtered poultry carcasses, is widely used in swine and poultry diets because of its highly digestible protein and balanced amino acid profile. Rendering may reduce amino acid digestibility of PoMe because rendering can induce heat damage to PoMe, and the effect of heat damage on amino acid digestibility in PoMe may be different between broiler chickens and growing pigs. For this reason, the objective of this study was to determine the effect of autoclaving on standardized ileal digestibility (SID) of amino acid in PoMe fed to broiler chickens and growing pigs. Poultry meal from the same batch was autoclaved at 134°C for 0, 30, 60, 90, 120, 150, or 180 min for 7 samples. Eight experimental diets consisted of 7 diets containing each PoMe sample as a sole source of nitrogen and a nitrogen-free diet. In Exp. 1, 656 male broiler chickens (initial BW = 719 ± 97 g) at d 18 post hatching were assigned to the 8 diets in a randomized complete block design with BW as a blocking factor. On d 23, birds were euthanized by CO2 asphyxiation and dissected for the collection of ileal digesta. In Exp. 2, 16 barrows (initial BW = 23.3 ± 0.7 kg) surgically fitted with T-cannulas at the distal ileum were allotted to duplicate 8 × 4 incomplete Latin square design with the 8 diets and 4 periods. Each experimental period consisted of 5-d adaptation and 2-d ileal digesta collection periods. Data for Exp. 1 and 2 were pooled together as a 2 × 7 factorial treatment arrangement with the effects of species (i.e., pigs and broiler chickens) and autoclaving time (i.e., 0 to 180 min). An Interaction between species and linear effect of autoclaving time was observed (P &amp;lt; 0.05) in SID of nitrogen, arginine, and threonine in PoMe. To be specific, the linear decrease in ileal digestibility of nitrogen and those AA with increasing autoclaving time was greater in pigs compared with broiler chickens. The SID of AA both linearly and quadratically decreased (P &amp;lt; 0.05) as autoclaving time increased. The SID of isoleucine, leucine, methionine, phenylalanine, and tryptophan in PoMe was greater (P &amp;lt; 0.05) in growing pigs compared with broiler chickens regardless of autoclaving time. In conclusion, increasing autoclaving time decreases SID of amino acids in PoMe, and SID values in some indispensable amino acids are greater in growing pigs compared with broiler chickens.