Dietary Net Energy Research Articles

Growth Performance, Dietary Energetics, Blood Metabolites, Carcass Traits, Meat Quality, and Gene Expression of Lambs Supplemented with a Polyherbal Phytogenic Additive

This study aimed to evaluate the effects of supplementation with a polyherbal phytogenic additive (PPA) on the productive performance, dietary energetics, blood metabolites, carcass traits, meat quality, and gene expression of finishing lambs. Thirty-six male Pelibuey lambs (23.61 ± 0.57 kg body weight (BW)) were housed in individual pens and assigned to four treatments (n = 9) with different doses of PPA: 0 (CON), 2.5 (PPAL), 5 (PPAM), and 7.5 (PPAH) g of PPA/kg of DM for 56 days. Average daily gain, dry matter intake, and observed dietary net energy for maintenance and weight gain increased linearly (p < 0.05) in lambs supplemented with PPAH. A linear reduction (p = 0.02) in FCR was detected in lambs fed PPAM and PPAH. The PPAH supplementation linearly increased (p < 0.001) Longissimus dorsi muscle area, but other carcass traits were not affected (p > 0.05) by PPA doses. The physicochemical characteristics of the meat and the hematological parameters of the lambs were not affected (p > 0.05) by the PPA doses. The glucose, uric acid, creatinine, and bilirubin serum concentrations decreased linearly (p < 0.05) in lambs supplemented with PPAM and PPAH. Gene ontology analyses showed that nine biological processes were modified (p < 0.05), including DNA replication, drug metabolism–cytochrome P450, oxidative phosphorylation, and chemical carcinogenesis–reactive oxygen species. In conclusion, high doses (7.5 g/kg DM) of PPA can improve growth performance and dietary energy utilization efficiency in finishing lambs. Likewise, gene expression analysis indicates that supplementation with high doses of PPA could improve energy production and antioxidant status in finishing lambs.

Effect of Long-Term Supplementation of AZOMITE (Hydrated Sodium Calcium Aluminosilicate) in Finishing Diets on Growth Performance, Dietary Energy, and Carcass Yield of Hairy Lambs.

The aim of this study was to evaluate growth performance, dietary energy utilization, and carcass characteristics (carcass weight, dressing percentage, and visceral organ mass) of feedlot lambs fed different levels of AZOMITE (AZO), a source of volcanic clay composed of hydrated sodium calcium aluminosilicate, the same as that included in a finishing diet. For this reason, 36 Pelibuey × Katahdin crossbred intact male lambs (18.81 ± 3.04 kg initial weight) were used in a feeding trial lasting 81 d. Lambs were grouped by initial weight and assigned within six weight groupings to 18 pens in a randomized complete block design. Diets, offered ad libitum, were corn-based finishing diets with an 88:12 concentrate-to-forage ratio supplemented as follows: 1) no AZO inclusion (CTRL), 2) AZO inclusion at a 0.75% level (0.75AZO) in diet dry matter, 3) AZO inclusion at a 1.50% level (1.5AZO) in diet dry matter. Cracked corn was replaced by AZO. After the feeding trial was finished, lambs were slaughtered and carcass weight was registered and dressing percentage was calculated. The data were analyzed as a randomized complete block design, with the pen as the experimental unit. Water consumption and dry matter intake were not affected (p ≥ 0.11) by supplemental AZO. The incorporation of AZO into the diet increased gain efficiency and observed dietary net energy (NE), being maximal with 0.75% AZO inclusion (quadratic effect, p = 0.02). The observed-to-expected dietary NE in the control group was as anticipated (1.00) according to the estimated energy based on the ingredient composition in diet, while in the 0.75AZO group, the observed dietary energy was 6% above expected, indicating a greater efficiency in energy utilization destined to growth (quadratic effect, p = 0.006). Lambs that were fed the AZO treatment showed an improvement (linear effect, p = 0.04) in hot carcass weight (HCW), and tended (linear effect, p = 0.06) to improve dressing percentage (DP) as AZO was increased in the diet. Visceral organ mass was not affected by the treatments. It is concluded that AZOMITE clay can be included up to 1.5% in finishing diets for lambs without negative effects on the intake of water and feed. Lambs that received diets supplemented with 0.75% AZO showed greater improvements in feed efficiency and dietary energy utilization, but an inclusion of 1.50% resulted in greater improvements to HCW and DP. This is the first report regarding the effects of AZO supplementation in the dietary energy utilization of fattening hairy lambs. Further research about the effects of AZO supplementation on ruminal and total tract digestion, carcass and meat quality, and the health of lambs is needed in order to more deeply understand the effects of AZO on its productivity performance.

PSLBI-9 The growth performance and total tract starch digestibility of finishing Nelore bulls fed flint corn-based diets are improved by the corn processing method and urea source

Abstract The aim of this study was to evaluate the flint corn processing method (CPM) and urea source for finishing Nellore bulls fed corn-based diets. In this study, 80 Nellore bulls [initial body weight (BW) = 388 ± 45.7 kg] were allocated into 28 pens (7 pens/treatment; 6 pens with 3 bulls + 1 pen with 2 bulls). A completely randomized design with a 2 × 2 factorial arrangement of treatments was used to test two CPMs: dry ground corn (DGC) and reconstituted and ensiled corn (REC), and two US: feed-grade urea (FGU) and post-ruminal release urea (PRU). Dietary inclusion (% DM) of flint corn (vitreousness = 86.0%) was 61.3% (DGC or REC), and urea source addition was 0.5% as non-protein nitrogen (NPN; as FGU or PRU). The PRU source (Trouw Nutrition, Netherlands) contained 82% urea on a DM basis. In an in vitro assay, 27% of this urea was released into the rumen. Experimental period lasted 100 d (with 14 d of adaptation). Fecal samples from each bull were collected in two periods of three consecutive days (d 44 to 46 and 94 to 96) at different time (0600, 1200, and 1800 h). Samples were composited by pen and analyzed for fecal starch (FS) and indigestible NDF as markers for fecal excretion. At the end of the experiment, bulls were slaughtered and the jejunum and pancreas were sampled from one bull per pen. Interaction effects were not found (P ≥ 0.31) for any feedlot growth performance variables (Table 1). Final BW, average daily gain, and feed efficiency (gain to feed; G:F) were greater for bulls fed REC and PRU than for those fed DGC and FGU (P < 0.02), respectively. As a result, observed dietary net energy (NE) for maintenance and BW gain were about 7.0% and 9.0% greater for bulls fed REC diets, and 4.3% and 5.6% greater for bulls fed PRU diets, respectively. Bulls fed DGC had 2.2 times greater FS compared with bulls fed REC, resulting in lower fecal pH and total tract starch digestibility (TSD) for bulls fed DGC compared with those fed REC (P < 0.01). Interestingly, a similar trend was observed in bulls fed PRU compared with those fed diets with FGU (P < 0.06). Jejunal gene expression of SLC5A1 was not affected by treatments (P > 0.14). Nevertheless, bulls fed diets with PRU presented greater jejunal α-amylase activity (P = 0.02). Pancreatic α-amylase activity was less when bulls were fed DGC + PRU diet. In conclusion, REC markedly improved TSD and growth performance compared with DGC. Additionally, independent of CPM, PRU inclusion as NPN source increased G:F and dietary NE concentration due to the positive effects on jejunal amylase activity and TSD.

249 Effects of sorghum silage kernel processing on growth performance and blood metabolites of beef heifers

Abstract Our previous studies suggested that using a shredlage (SHRD) processor or a conventional (CONV) sorghum kernel processor leads to similar apparent total tract nutrient digestibility of whole plant sorghum silage (WPSS). This study evaluated the effects of feeding WPSS harvested using different kernel processors (CONV vs. SHRD), on growth performance of beef heifers. Grain sorghum (ADV2450IG; Advanta Seeds, Argentina) was harvested at the hard-dough stage with a Class Jaguar 950 (Harsewinkel, Germany), switching the kernel processor to generate the forage material for the two treatments: CONV and SHRD. The material was bagged in two 2.7 m diameter bags and allowed to ferment for 3 mo. Black Angus heifers [n = 96; body weight (BW) = 15 ± 1 mo, 249.6 ± 28.6 kg] were blocked by initial BW, and randomly assigned to pens (8 heifers/pen, 6 pens/treatment). Diets consisted, all in DM basis, of WPSS of each respective type (SHRD or CONV) at 90.5%, expeller soybean meal at 7.0%, and a vitamin-mineral-NNP concentrate at 2.5%. The experiment consisted of a 14-d adaptation period, followed by a 56-d growing period; and feed was offered once daily. Data were analyzed as a randomized complete block design, using pen as the experimental unit, with the fixed effect of treatment and the random effect of block. No differences were observed (P > 0.10) for final BW, dry matter intake, and residual feed intake. However, CONV fed heifers tended to gain more BW per day (ADG, 0.83 vs. 0.77 kg/d; P = 0.07) and had greater gain to feed ratio (GF, 0.083 vs. 0.075 kg/kg; P = 0.05) and greater Kleiber ratio (KR, 12.1 vs 11.2 g/kg; P = 0.05) as compared with SHRD fed heifers. Furthermore, performance calculated dietary Net Energy of gain (NEg) in CONV fed heifers tended to be greater than that for SHRD (0.70 vs. 0.65 Mcal/kg of diet DM, respectively; P = 0.06). Moreover, blood serum from CONV fed heifers had 16% greater total bilirubin (P = 0.04), 12% greater cholesterol (P = 0.02), and slightly greater non esterified fatty acids (P = 0.03) concentrations. Noteworthy, serum concentrations of total bilirubin were correlated (P ≤ 0.03) with ADG, GF, KR and NEg. In conclusion, the type of kernel processor utilized for the harvest of sorghum silage may have an impact on feed efficiency of beef cattle. These differences could be related to changes on the site of utilization of nutrients, particularly starch; what could also explain the differences on blood metabolites. However, further research is needed to help explain these findings.

380 Diet protein concentration does not influence dietary net energy by group housed growing pigs offered ad libitum access to feed

Abstract The objective was to test the hypothesis that net energy (NE) of diets is not increased by reducing soybean meal (SBM) and increasing crystalline amino acids (CAA) in diets fed to group-housed pigs on an ad libitum basis. Two “normal protein” diets with 17 and 14% crude protein (CP) were formulated. One diet was based on corn, SBM, and no CAA and the other diet was based on corn, SBM, and crystalline Lys, Met, and Thr. Four additional diets containing 13, 12, 11, or 10% CP were formulated by reducing SBM and increasing crystalline Lys, Met, Thr, Trp, Val, and Phe. Growing pigs (n = 24; initial body weight = 29.9 ± 2.4 kg) were randomly allocated to 6 calorimeter chambers with 4 pigs per chamber. The 6 chambers were allotted to the six diets using a 6 × 6 Latin square design with six 15-d periods providing 6 replicate chambers per diet. Pigs had ad libitum access to diets throughout the experiment except during the fasting periods. Consumption of O2 and production of CO2 and CH4 were measured, and fecal and urine samples were collected for 6 d after 7 d of adaptation. Fasting heat production (FHP) was determined for 12 h following a 24 h fasting period. Diets, fecal samples, and lyophilized urine samples were analyzed for gross energy (GE) and N. Data were analyzed using contrasts statements to determine linear and quadratic effects of reducing dietary protein. Results indicated that feed intake, fecal and urine GE output, the apparent total tract digestibility (ATTD) of dry matter and GE, total heat production (THP), FHP, and retained energy were not different between pigs fed the 17 and the 14% CP diets (Table 1). The respiratory quotient (RQ) of pigs fed the 17% CP diet was less (P = 0.045) compared with the 14% CP diet. Digestible energy (DE) and metabolizable energy (ME) in the 17% CP diet were greater (P < 0.05) than in the 14% CP diet, but NE was not different between these 2 diets. Feed intake, GE intake, and fecal GE output of pigs were linearly (P = 0.044) increased by reducing CP in diets, but reducing diet CP did not affect ATTD of dry matter or GE or urine GE excretion. Total heat production, FHP, retained energy, and DE, ME, and NE were also not affected by reducing CP in diets. In conclusion, reducing CP of diets for pigs by reducing SBM and increasing CAA did not increase NE of the diet when fed to group-housed pigs on an ad libitum basis, and dietary CP does not appear to influence diet NE.

Effects of Supplemental Calcium Propionate and Concentrate Level: Growth Performance, Body Fat Reserves, and Health of High-Risk Beef Calves.

The aim of this study was to examine the impact of daily calcium propionate (CaPr) supplementation (0 or 20 g/calf) on growth performance, dietary energetics, body fat reserves, serum metabolites, and hematological responses in high-risk beef calves fed diets with varying (50, 60, or 70%) concentrate (CON) levels. In addition, a cost/income analysis of CaPr supplementation was carried out. Forty-eight crossbred bull calves (152.8 ± 1.56 kg body weight and 5.5 months of age) were involved in a fully randomized experimental design employing a 2 × 3 factorial arrangement of treatments. Calves were allocated (n = 8 per treatment) to individual pens (3.14 × 5.25 m) and were subjected to one of the following treatments during 42 d: No CaPr supplementation in diets containing 50, 60, or 70% CON (NoCaPr + 50, NoCaPr + 60, NoCaPr + 70, respectively) or daily CaPr supplementation dosed at 20 g/calf in diets containing 50, 60, or 70% CON (20CaPr + 50, 20CaPr + 60, 20CaPr + 70, respectively). Non-supplemented calves exhibited decreased dry matter intake (DMI) with increasing CON levels in their diets, while CaPr-supplemented calves displayed the opposite effect (interaction, p = 0.04). In calves fed a lower-CON diet (50%), those supplemented with CaPr showed greater average daily gain (ADG, 20.2%, p = 0.05) and lower DMI (2.2%, p = 0.03), resulting in improved ADG/DMI ratio, dietary energy, and energy retention (24.6, 14.4, and 18%, p < 0.05). These effects diminished when calves received diets with 60 or 70% CON but led to a 14.2% increase in rump fat thickness (p = 0.04). Only in non-supplemented CaPr calves, increasing the level of CON from 50 to 70% in the diet increased ADG (21.2%), decreased DMI (2.2%), and improved the ADG/DMI ratio (22.7%), with no impact on dietary net energy utilization. Non-supplemented calves exhibited an increase in lymphocytes as CON levels rose in their diets, whereas CaPr-supplemented calves showed the opposite effect (interaction, p = 0.05). Supplementation of CaPr decreased total protein (TP, p = 0.03) and albumin (ALB, p < 0.01) serum concentrations, with lower concentrations observed in 20CaPr + 50. CaPr supplementation reduced (p = 0.01) total cholesterol (TCHO) levels. An interaction between CaPr and CON level (p = 0.02) was observed since TCHO levels remained consistently low at higher CON levels. Glucose was decreased with increasing levels of CON (p = 0.02) but not (p = 0.85) for CaPr-supplemented calves. NoCaPr + 50 and NoCaPr + 70 increased (p = 0.05) ALB concentration. Gamma glutamyltransferase levels increased (p = 0.05) with increasing CON levels irrespective of CaPr supplementation. Comparing the profit within the same CON level in the diet, CaPr treatments yielded higher income, with the largest difference in profit observed when CaPr was supplemented at 50% CON level (USD 29 more/calf). In conclusion, CaPr supplementation proves to be an effective strategy for enhancing growth performance and dietary energy among high-risk beef calves, resulting in greater economic returns. The groups that received CaPr demonstrated superior profitability, particularly in calves fed diets with lower CON levels. Under the conditions in which this experiment was carried out, the optimal response occurred when the low-CON diet (50%) was supplemented with CaPr.

Encapsulated Butyric Acid and Zinc as a Feed Additive for Lambs Abruptly Transitioned to a Grain-Based Diet.

Butyric acid is attributed to gastrointestinal epithelial development and health and two studies were conducted to determine if supplementing encapsulated butyric acid and zinc (BZ) in lambs abruptly transitioned to a finishing diet has effects on growth performance, efficiency of dietary net energy utilization, rumen morphometrics, small intestinal histology, and carcass traits. Polypay wethers (n = 84; initial shrunk body weight = 38.8 kg ± 4.8 kg) were used in a randomized complete block design study. Wethers were abruptly transitioned from a high roughage-based diet to a 100% concentrate-based diet and dietary treatments were 0 or 2 g BZ/kg of diet dry matter. Study 1 evaluated growth performance and carcass traits of lambs over a 59.5 d feeding period, and Study 2 evaluated changes in rumen morphometrics and small intestine histology in serial harvested lambs. Wethers supplemented with BZ had increased body wall thickness, decreased calculated boneless closely trimmed retail cuts, and decreased red meat yield (p ≤ 0.03) compared to non-supplemented wethers. Linear effects (p ≤ 0.01) for harvest date were observed for most rumen and small intestine measurements. Supplementing wethers with BZ did not improve growth performance, carcass traits, or rumen and small intestine measurements. The effects of BZ supplementation on fat deposition in ruminants should be further investigated.

Influences of a Supplemental Blend of Essential Oils Plus 25-Hydroxy-Vit-D3 and Zilpaterol Hydrochloride (β2 Agonist) on Growth Performance and Carcass Measures of Feedlot Lambs Finished under Conditions of High Ambient Temperature.

Forty-eight Pelibuey × Katahdin male intact lambs (25.12 ± 3.79 kg LW) were used in a 70-d growing-finishing trial. Dietary treatments consisted of total mixed corn-based diet supplemented with: (1) no feed additives (Control); (2) 150 mg of essential oils blend plus 0.10 mg of 25-hydroxy-Vit-D3/kg diet offered throughout the 70-d experimental period (EOD3); (3) Control diet fed during the first 35 days and zilpaterol hydrochloride (ZH) supplementation at 6 mg/kg diet offered during the final 35 days of the experiment (32 days with ZH with a withdrawal 3-d before harvest), and (4) basal diet supplemented with EOD3 during first 35 days finishing, and EOD3 in combination with ZH (EOD3 + ZH) during the subsequent 32-days with ZH withdrawal 3 days before harvest. The temperature-humidity index during the experiment averaged 80.4 ± 3.2. There were no treatment interactions (p > 0.20) on growth performance and carcass measures. Supplemental EOD3 did not affect (p = 0.43) dry matter intake (DMI), but increased (p < 0.01) carcass adjusted average daily gain (ADG, 9.2%), gain efficiency (GF, 6.7%), and observed vs. expected dietary net energy for maintenance (NEm, 4.8%) and for gain (NEg, 6.4%). Supplemental ZH did not affect dry matter intake (DMI, p = 0.50) but increased (p < 0.01) carcass adjusted ADG (14.5%), GF (13%) and observed vs. expected dietary NEm (9%) and NEg (11.7%). Compared to control lambs, the combination of both additives increased ADG (24.9%), GF (21.2%), and observed vs. expected dietary NEm and NEg (14.2% and 18.9%, respectively). There were no treatment interactions on carcass characteristics, visceral organ mass, or on gene expression of IGF1, IGF2 and mTOR in longissimus muscle (LM). Supplemental EOD3 increased hot carcass weight (HCW; 4.0%, p < 0.01) but did not affect other carcass measures. Supplemental EOD3 decreased (3%, p = 0.03) intestine mass weight (g intestine/kg empty body weight). Supplemental ZH increased HCW (6%, p < 0.01), dressing percentage (1.7%, p = 0.04), and LM area (9.7%, p < 0.01), and decreased kidney-pelvic-fat percentage (16.2%, p < 0.01), fat thickness (14.7%, p = 0.03), and visceral fat. Compared to controls, the combination of EOD3 with ZH increased HCW (10.2%). It is concluded that growth performance responses to supplemental EOD3 and ZH are additive. Both supplements can be fed in combination without detrimental effects on expected benefits when fed separately. In addition, ZH supplementation improves carcass traits.

60 Effects of phase feeding rolled hybrid rye on feedlot performance in backgrounded beef steers

Abstract The objective of this study was to evaluate the effects of phase-fed rolled hybrid rye on feedlot performance and carcass characteristics of finishing steers. Backgrounded steers [n = 110; initial shrunk (4% of body weight; BW) = 391 ± 1.3 kg] were assigned to 1 of 14 pens at the Southeast Research Farm, Beresford, SD in a randomized complete block design. Pens were blocked by location with four blocks of dirt-surfaced, outside pens (8 pens; 10 steers/pen) and three blocks of concrete-surfaced, partially covered pens (6 pens; 5 steers/pen). Pens were randomly assigned to one of two dietary treatments (7 pens/treatment): dry rolled corn (DRC) included at 66% diet dry matter (DM) or rolled hybrid rye (RRYE) included at 66% diet DM for the initial 46 d of the experiment followed by the DRC diet from d 47 to trial completion on d 144. One steer was removed from the study because of lameness. During the rye feeding period (d1 to d 46), RRYE decreased average daily gain (ADG) by 13% (P = 0.01; 1.59 and 1.83 kg, respectively) and DMI by 18% (P = 0.01; 8.45 and 10.30 kg, respectively) with no effect (P = 0.15) on gain to feed ratio (G:F) compared with DRC. Negative effects of RRYE were more pronounced during the first 20 d of the experiment with ADG reduced by 29% (P = 0.01; 1.13 and 1.60 kg, respectively), DMI by 15% (P = 0.01; 8.20 and 9.61 kg, respectively), and G:F by 17% (P = 0.01; 0.139 and 0.167, respectively). Dietary net energy values for RRYE were increased (P ≤ 0.03) from d 1 to 46. Feeding rye reduced BW on d 46 by 10 kg compared with DRC (P = 0.01; 474 and 464 kg, respectively). From d 47 to 144 when all steers were fed a common diet there were no differences (P ≥ 0.38) in any growth performance responses or measures of dietary net energy utilization. When measured over the entire experiment, DMI tended to be less (P = 0.08) for RRYE compared with DRC with no effect on ADG or G:F (P ≥ 0.19). Final BW was numerically reduced in the RRYE treatment compared with DRC (P = 0.21; 614 and 623 kg, respectively). Cumulative observed-to-expected ratios for NEm and NEg were increased (P = 0.05) for RRYE compared with DRC. Dietary treatments did not affect (P ≥ 0.29) carcass characteristics, distribution of USDA yield or quality grades, or liver abscess incidence or severity. Feeding rolled rye decreased ADG, DMI, and G:F during the first 46 DOF with similar growth performance when fed a DRC-based diet for the final 98 d.

28 Investigation of protein deposition pattern of PIC337×Camborough commercial pigs

Abstract The objective of the trial was to investigate the protein deposition pattern of PIC337×Camborough commercial pigs. A total of 1,064 barrows and gilts [PIC337×Camborough, initial body weight (BW) = 6.0 ± 0.1 kg] were used in the trial with 38 mixed sex pens, 28 pigs per pen. At the beginning of the trial, the lightest 10% of the barrows and gilts were selected and placed in four pens (equal numbers of barrows and gilts within a pen), and the remaining pigs were randomly placed into the other pens (equal numbers of barrows and gilts within a pen). A common 6-phase corn-soybean based wean-to-finish diets were fed throughout the trial. Dietary net energy and standardized ileal digestible lysine levels were (6-10 kg BW: 2,600 Kcal/kg and 1.35%; 10-20 kg BW: 2,520 Kcal/kg and 1.30%; 20-38 kg BW: 2,470 Kcal/kg and 1.20%; 38-72 kg BW: 2,450 Kcal/kg and 0.98%; 72-127 kg BW: 2,450 Kcal/kg and 0.87%; and 127-149 kg BW: 2,450 Kcal/kg and 0.77%). On d 97 after placement, 5 barrows and 5 gilts with BW close to pen average were selected for individual BW by a portable scale and 10th rib backfat and loin depth measurements (ExaGo portable ultrasound scanner, Imv imaging, UK). Then on d 111, 117, 136, 142, and 167 after placement, the same 5 barrows and 5 gilts were measured for individual BW, 10th rib backfat and loin depth. The fat-free lean mass is estimated by the equation 6.783-0.6198×(10th rib backfat depth, mm)+0.1578×(10th rib loin depth, mm)+1.0362×(warm carcass weight, kg). A constant carcass yield of 75% was used to estimate warm carcass weight. Data were analyzed using a linear mixed model in R Studio (Version 3.5.2, R Core Team; Vienna, Austria). The average BW of pigs at the 6 measurements were: 77.2, 92.4, 99.2, 122.5, 128.0, and 153.6 kg, respectively. The average daily gain (ADG) was 1,139, 1,155, 1,145, 1,126, and 977 g/d for 77.2 to 92.4 kg BW, 92.4 to 99.2 kg BW, 99.2 to 122.5 kg BW, 122.5 to 128.0 kg BW, and 128.0 to 153.6 kg BW, respectively. The average daily 10th rib backfat depth gain was 0.05, 0.08, 0.15, 0.17, and 0.20 mm/d. The average daily 10th rib loin depth gain was 0.42, 0.43, 0.41, 0.39, and 0.23 mm/d. The average daily fat-free lean mass gain (ADFFLG) was 547, 551, 528, 515, and 422 g/d. The fitted quadratic model for ADG is 83.57782 + 19.90632 × (BW, kg)-0.09176×(BW, kg)2, and the calculated maximum ADG was 1,163 g/d when BW was 108.5 kg. The fitted quadratic model for ADFFLG is 85.90926 + 9.23773 × (BW, kg) - 0.04591 × (BW, kg)2, and the calculated maximum ADFFLG is 550.6 g/d when BW was 100.6 kg. Under the conditions of the current trial, PIC337×Camborough pigs reaches the maximum rate of protein deposition at BW between 100.6 and 108.5 kg.

232 Evaluation of a phytogenic feed additive with essential oils and plant extracts on growth performance in single sourced steer calves fed a forage-based diet during the initial 53 d receiving period

Abstract The receiving period of a feedlot calf is one of the most stressful stages in the life of that animal and can result in respiratory disease caused, in part, by reduced feed intake and transit stress. Feeding a phytomolecule compound in combination with current therapeutic strategies may aid in controlling systemic inflammation and improve the performance of newly received calves. This study determined whether a phytogenic feed additive with essential oils and plant extracts (PFA) influences measures of growth and growth efficiency during the feedlot receiving phase. The two treatments were a control group fed no additive (CON) and a treatment group fed PFA additive at a rate of 0.25 g/45.4 kg of body weight (BW; PFA). Steers were transported 285 km from an auction facility to the Ruminant Nutrition Center in Brookings, SD where they were vaccinated against viral respiratory diseases and clostridial species, and administered pour-on anthelmintic. Steers were divided into 10 replicate pens of 8 steers (305 ± 30 kg) per treatment (n = 160 steers) in a randomized complete block design. The steers were fed a basal diet [dry matter (DM) basis] containing corn silage (74%), DDGS (21%), a liquid supplement (5%), and monensin sodium (Rumensin-90, Elanco Animal Health) at 25 g/907 kg (DM basis) for 53 d. Steers were fed 2X daily with intakes closely managed for the first 14 d during adaptation to the receiving diet then a slick bunk management strategy was applied for the remainder of the study. No mortality was observed in this study, and one steer was treated for respiratory disease from the CON group. There were no significant differences observed in BW, average daily gain (ADG), variation in ADG, dry matter intake, or feed conversion efficiency from d 1 to 29, 29 to 53, or during the cumulative receiving period (P ≥ 0.11) between the CON and PFA groups. NEm and NEg did not differ between the treatments (P ≥ 0.79). The ratio of observed-to-expected dietary net energy was also not affected by dietary treatment (P ≥ 0.71). The steers used in this study were in good health and had minimal morbidity (0.63%) with no mortality during the 53-d receiving study which contributed to the feed additive having no appreciable influence on the growth and health outcomes in this study.

23 The effects of dietary net energy level on grow-finish performance and carcass characteristics of intact male market pigs managed with Improvest

Abstract Improvest is a gonadotropin releasing factor (GnRF) analogue-diphtheria toxoid conjugate product approved for temporary suppression of testicular function and reduction of boar taint in intact male pigs (Zoetis Canada Inc.). Objectives for this study were to determine the effects of dietary net energy (NE) level during the grow-finish period on live performance and carcass characteristics of intact male pigs managed with Improvest/immunological castration (IC) when compared with physically castrated (PC) male pigs. The 101-d study began when 1,008 pigs (504 intact male pigs and 504 PC male pigs; 10 wk old) were allocated by body weight to 48 pens with 21 intact males or 21 PC males per pen. Three dietary NE treatments were fed to pigs using five dietary phases to provide an average of 2,212 kcal/kg (Low NE), 2,337 kcal/kg (Medium NE), or 2,462 kcal/kg (High NE). Dietary programs were formulated according to standardized ileal digestible lysine requirements of IC males or PC males. The experiment was designed and analyzed as a 2 × 3 factorial with main effects of Improvest management and NE. For the overall study period, there were no significant interactions between Improvest management and NE (P ≥ 0.19) for average daily feed intake (ADFI), average daily gain (ADG), or gain to feed ratio (G:F; Table). There were also no significant interactions between Improvest management and NE (P ≥ 0.06) for carcass characteristics. Immunologically castrated male pigs consumed less feed (5.3% less ADFI; P &amp;lt; 0.01), grew faster (5.1% greater ADG; P &amp;lt; 0.01), and were more efficient (11.2% greater G:F; P &amp;lt; 0.01) compared with PC male pigs. Hot carcass weight (HCW) did not differ (P = 0.16) between IC males and PC males (attributed to 1.6 percentage unit less dressing percentage for IC males; P &amp;lt; 0.01); however, IC males were leaner (0.9 mm less backfat and 0.65% greater predicted lean yield; P &amp;lt; 0.01) compared with PC males. For the overall study period, pigs fed Low NE and Medium NE diets consumed more feed than pigs fed High NE diets, and pigs fed Low NE diets grew slower than pigs fed Medium NE and High NE diets. This resulted in pigs fed Low NE diets having 4.4% less G:F than pigs fed Medium NE and 8.6% less G:F than pigs fed High NE diets (P &amp;lt; 0.01). Pigs fed Low NE had 3.0 kg lighter (P &amp;lt; 0.01) HCW compared with Medium NE, while High NE had intermediate HCW that did not differ from the other two treatments. Overall, typical Improvest response levels were sustained for each of the NE treatments in this study; however, consideration should be provided to the known production impacts of low NE diets when male market pigs are managed with Improvest.

103 Effects of partial or total replacement of dried distiller’s grain with soybean meal on growth performance, carcass characteristics, sera urea nitrogen, and net energy utilization in finishing beef steers

Abstract The objective of this study was to determine if partial or complete replacement of dried distiller’s grains plus solubles (DDGS) with solvent-extracted soybean meal (SBM) influences growth performance, efficiency of dietary net energy utilization, sera urea-N (SUN) concentrations, or carcass traits in finishing beef steers. Continental × British steers [initial shrunk body weight (BW) = 382 ± 37 kg] were used in a 139-d experiment. Treatments included: DDGS fed at 20% DM (13.4% CP; DDGS), SBM replacing 50% of DDGS (14.4% CP; SBM50), and SBM replacing 100% of DDGS (15.4% CP; SBM100). Steers (n = 189) were weighed and allotted to 1 of 24 pens (n = 8 steers per pen; 8 pens per treatment) at the Ruminant Nutrition Center near Brookings, SD. Whole blood was collected and harvested as sera on d 77, 105, and 139 to determine SUN concentration. Growth and carcass data were analyzed as a randomized complete block design using the GLIMMIX procedure of SAS 9.4 with treatment and block (initial BW grouping) as fixed effects; SUN data were analyzed using repeated measures, pen was the experimental unit. Inclusion level was evaluated for linear and quadratic components by the method of orthogonal polynomials. Final BW was calculated by dividing hot carcass weight (HCW) by 0.625. No differences were noted (P ≥ 0.18) for final BW, average daily gain, dry matter intake, or feed efficiency. Dietary treatment tended to affect gain to feed ratio (G:F; quadratic; P = 0.10) and SBM increased the apparent efficiency of energy capture. Treatment had no effect (P ≥ 0.22) on HCW, rib fat, marbling score, USDA yield grade, or final BW adjusted to 28% empty body fat. Complete replacement of DDGS with SBM increased rib eye area by 1% (linear; P = 0.02), but decreased dressing percentage (linear, P = 0.03). Distribution of USDA quality or yield grades were unaffected by treatment (P ≥ 0.36). No treatment × day interaction was observed for SUN (P = 0.20). However, day (P &amp;lt; 0.01) and treatment (P &amp;lt; 0.01) effects were observed. Initial samples (d 77) differed between DDGS and SBM treatments, with the latter having greater SUN values (P &amp;lt; 0.01). On d 105, the SBM100 treatment had greater SUN than DDGS, and SBM50 was intermediate (P &amp;lt; 0.01). On d 139, steers from SBM100 had elevated increased SUN compared with SBM50 and DDGS treatments (P &amp;lt; 0.01). Net energy values calculated from animal performance for DDGS agreed closely with tabular estimates. In this experiment, replacement of DDGS with SBM increased the observed to expected ratio of dietary NE, increased muscularity and tended to decrease DP with no other observed effects on growth performance or carcass traits.

161 Effect of replacement of dried distiller’s grains plus solubles with increasing extruded and expelled soybean meal on feedlot performance and carcass characteristics in finishing steers

Abstract The objective of this study was to evaluate the effects of increasing inclusion of extruded and expelled soybean meal (EESBM) as a partial replacement of dried distiller’s grains plus solubles (DDGS) feedlot performance and carcass characteristics in steers. Steers [n = 144; initial shrunk body weight (BW) = 399 ± 27 kg] were assigned to 1 of 18 pens (8 steers/pen). Pens were randomly assigned to one of three dietary treatments (6 pens/treatment): 100% DDGS included at 15% of diet dry matter (DM; NO-SBM), a blend of 70% DDGS and 30% SBM included at 15% of diet DM (30-EESBM), and a blend of 40% DDGS and 60% SBM included at 15% of diet DM (60-EESBM) in a randomized complete block design with pen as experimental unit. Data were analyzed as a RCBD with fixed effects of treatment and random effect of block (location within feedyard). Linear and quadratic contrasts were used to assess EESBM level effects. All growth performance results were determined on a carcass-adjusted [hot carcass weight (HCW)/0.625] basis. Supplementation of EESBM increased (P ≤ 0.04) final BW and average daily gain (ADG) by 1.6 and 3.8%, respectively. Additionally, dietary treatment tended to result in increased (P ≤ 0.07) DMI and improved feed conversion by 1.2 and 2.6%. Final BW, ADG and gain to feed ratio (G:F) increased (linear; P ≤ 0.03) with increasing inclusion of EESBM in replacement of DDGS. Dry matter intake (DMI) tended to increase quadratically (P = 0.10) with increasing EESBM inclusion. No differences (P ≥ 0.37) were observed in any other carcass-adjusted growth performance responses as well as apparent utilization of dietary net energy (P ≥ 0.15). Increasing inclusion of EESBM resulted in a linear increase (P = 0.02) in HCW. A tendency for a linear increase (P = 0.09) was noted for empty body fat% with greater EESBM inclusion. No other differences (P ≥ 0.12) were observed in carcass performance, distribution of yield and quality grades, and lung and liver health outcomes. In conclusion, feeding EESBM as a partial replacement of DDGS resulted in greater DMI, ADG and carcass weight, without negatively influencing measures of carcass quality or cutability. Under the conditions of this experiment, the NE value of EESBM is 8.5% greater than DDGS.

146 Comparing feeding strategies during heat stress in finishing pigs using a stochastic swine model

Abstract Nutritionists may feed standard diets or increase dietary net energy (NE) and/or standardized ileal digestible lysine (SIDLys) to counter reduced average daily feed intake (ADFI) due to heat stress in the late finishing phase. The objective of this work was to develop a set of statistical tools to analyze different grow-finish feeding strategies using the simulations from a proprietary stochastic swine model (Watson) when heat stress occurs during the last 2 wk of the finishing phase. Financial considerations were excluded from the study. Nutrient recommendations for maximum feed efficiency were derived from Watson and used to formulate a grower diet for 25 to 60 kg body weight (BW), and four finisher diets for 60 to 135 kg BW: a) thermoneutral (10 MJ NE/kg, 7.9 g/kg SIDLys), b) high AA (10 NE/kg, 9.2 g/kg SIDLys), c) high NE (10.5 MJ/kg NE, 7.9 g/kg SIDLys), and d) high NE and high AA (10.5 MJ NE/kg, 8.3 g/kg SIDLys). The grow-finish period was simulated by feeding the grower diet followed by the finisher diets in 5 different scenarios: 1) thermoneutral, diet a; 2) heat stress, diet a; 3) heat stress, diet a, and b during last 2 wk; 4) heat stress, diet a, and c during last 2 wk; 5) heat stress, diet a, and d during last 2 wk. Performance results were obtained by running each scenario 100 times, generating a new population per simulation. Results from scenarios 1) and 2 showed that heat stress in the last 2 wk reduced (P &amp;lt; 0.05) ADFI and average daily gain of pigs fed diet a by 790 g/d and 310 g/d, respectively. This resulted in a decrease of 4.79 kg in final BW, an increase of 0.64% lean yield, and a decrease of 0.80 mm back-fat at slaughter (P &amp;lt; 0.05). An increased dietary SIDLys (3), NE (4), or both (5) during heat stress did not affect BW compared with scenario 2 (P &amp;gt; 0.05). An increased NE (4) or NE and SIDLys (5) did not affect lean yield and back fat compared with scenario 2 (P &amp;gt; 0.1). But increased SIDLys during heat stress (3), increased lean yield (P = 0.04) and a trend in less back fat (P = 0.07) compared with scenario 2. In conclusion, pig performance was reduced with heat stress in the late finishing period. With the developed statistical tools, we determined from the simulations that none of the proposed strategies significantly increased final BW compared with the baseline (2). But feeding greater SIDLys will likely result in significantly greater lean yield and less back fat. When formulating diets with greater nutrient density attention to ingredient cost and pig prices should be considered.

58 Evaluation of a phytogenic blend on growth performance, health, carcass traits, and efficiency of dietary net energy utilization in finishing beef steers

Abstract The objective of this study was to determine if a formulated blend of capsicum oleoresin, clove essential oil, and garlic essential oil (CCG; Fytera Advance - Selko USA, Indianapolis IN) influences measures of cattle growth, efficiency, health, or carcass traits, during the finishing phase in steers fed a concentrate-based diet. Charolais × Angus steers [n = 96; initial shrunk body weight (BW) = 391 ± 34.0 kg] were used in a 144-d finishing experiment at the Ruminant Nutrition Center in Brookings, SD. Steers were individually weighed and allotted to one of 14 pens (n = 6 to 7 steers; 7 pens/treatment) in a randomized complete block design and randomly assigned to 1 of 2 treatments: control diet without the test product (CON) or a diet including CCG at 500 mg/steer daily (CCG). The average nutrient content of the finishing diet was: 13.5% CP; 18.7% NDF; 2.06 Mcal/kg NEm; and 1.39 Mcal/kg NEg; monensin sodium was included in the diet at 30 g/907 kg. Steers were fed twice daily, and bunks were managed according to a slick bunk system. There were no differences (P ≥ 0.10) in any growth performance outcome from d 1 to 35, 36 to 70, or 71 to 98. The within pen standard deviation for average daily gain (ADG) from d 71 to 98 tended to be reduced (P = 0.10) for CCG steers compared with CON. From d 99 to 144 steers supplemented CCG had 5% greater dietary energy utilization (P = 0.01), tended to have 5% greater ADG (P = 0.09), and 8% improved feed efficiency (P = 0.01). Experimental periods when improved pen gain uniformity and feed efficiency were observed coincided with increased summertime temperatures. No differences (P ≥ 0.15) were noted for cumulative growth performance. No differences were noted for any carcass measurements or categorical carcass outcomes, nor lung or liver health outcomes (P ≥ 0.15). Use of CCG had no appreciable influence on any cumulative growth performance responses. However, the use of CCG decreased within pen variation in ADG indicating more uniform nutrient intake among cattle and increased feed efficiency during summertime heat events.

47 Application of a ‘high’ or ‘low’ energy matrix to a nutrient-reduced diet supplemented with a novel phytase maintained growth performance and conferred production and sustainability benefit

Abstract This study assessed the capacity of a novel consensus bacterial 6-phytase variant (PhyG) to maintain growth performance of weaned pigs when added to a nutrient-reduced mixed cereal diet with two levels of dietary net energy (NE) reduction applied. A total of 360 newly weaned pigs [Greater York × Norsvin Landrace; initial body weight (BW) 8.4 ± 0.78 kg] were assigned to 60 floor-pens and 5 dietary treatments in a randomized complete block design. There were 2 blocks (weaning group), 6 replicate pens per block, and 6 pigs/pen (3 male, 3 female), in total of 12 replications per treatment. Diets were based on wheat, corn, barley, and soybean meal and were offered to pigs in 2 phases in pelleted form (0–14 and 14–35 d post-weaning). Treatments comprised a nutritionally adequate positive control (PC) and 4 negative control (NC) diets supplemented with PhyG. The NC diets were reduced in digestible P, Ca, Na, and digestible amino acids vs. PC, according to the expected contribution of PhyG added at 1,000 phytase units (FTU)/kg (NC1) or 2,000 FTU/kg (NC2), respectively. Each NC1 and NC2 was formulated at two NE reduction levels, designated ‘low’ and ‘high’ (‘low’: -53 to -65 kcal/kg and ‘high’: -73 to -86 kcal/kg, vs. PC at 1,000 and 2,000 FTU/kg PhyG, respectively). Data were analyzed by ANOVA. Means separation was by Tukey’s HSD test. During both phases and overall (0–35 d), average BW, average daily gain (ADG), average daily feed intake (ADFI), and feed conversion ratio (FCR) in all PhyG-supplemented, nutrient- and NE-reduced treatments, were either not different or were improved compared with the PC. Overall ADG, ADFI, and final BW (d 35) were greater in NC2+PhyG 2,000 FTU/kg ‘low’ vs. PC (466 vs. 424 g, 9.9%, 622 vs. 567 g, 9.7%, and 24.7 vs. 23.1 kg, 6.9%, respectively; P &amp;lt; 0.05). Total feed costs (ingredients price, February 2023) and estimated carbon footprint (CFP; FeedPrint, WUR, The Netherland) per kilogram of BW gain (BWG) were reduced in all PhyG-supplemented, nutrient- and NE-reduced treatments vs. PC. Feed costs saving per kg BWG were greater with ‘high’ than ‘low’ NE reduction applied (-0.013 vs. -0.007 €, respectively, vs. PC) with PhyG at 1,000 FTU/kg, and it was greatest in NC2+PhyG 2,000 FTU/kg with ‘low’ NE reduction (-0.036 € vs. PC). Similarly, the CFP was reduced from 2,068 to 1,840 g CO2 eq/kg BWG (-11 %) by NC2+PhyG 2,000 FTU/kg with ‘low’ NE reduction vs. PC. In conclusion, the application of a full nutrient matrix with ‘high’ or ‘low’ NE reduction combined with supplementation of PhyG maintained growth performance of weaned pigs and reduced the total feed costs and carbon footprint per kg BW gain, lead to production and sustainability benefits.

24 Effects of reducing dietary net energy on growth performance and carcass characteristics of grow-finish pigs

Abstract This study was conducted to evaluate the effects of dietary NE on growth performance, carcass characteristics, and removal and mortality rates of grow-finish pigs. A total of 1,927 pigs [initial body weight (BW) 23.3 ± 0.23 kg] were used in a 125-d study. Pens of pigs were blocked by BW and randomly allotted to dietary treatments in a randomized complete block design with 23 to 26 pigs/pen and 15 replications/treatment. Pens received 1 of 5 diets with decreasing NE based on Eq. 1-8 NRC (2012) using proximate analysis of the major ingredients. A corn-soybean meal-based control diet was blended with a low energy diet that contained 8% less NE through inclusion of 25% wheat middlings and 15% DDGS (6% oil) to achieve intermediate NE levels. Thus, dietary NE fed through 5 dietary phases were: phase 1 (2,432, 2,383, 2,335, 2,286, and 2,237 kcal/kg); phase 2 (2,463, 2,413, 2,363, 2,315, and 2,266 kcal/kg); phase 3 (2,495, 2,445, 2,395, 2,345, and 2,295); phase 4 (2,518, 2,468, 2,417, 2,367, and 2,317 kcal/kg); and phase 5 (2,537, 2,486, 2,435, 2,384, 2,334 kcal/kg). Dietary phases were fed from approximately 23-40, 40-60, 60-80, 80-105, and 105-133 kg BW, respectively. Overall, reducing NE decreased (linear, P &amp;lt; 0.001) average daily gain (ADG) and final BW and increased (linear, P &amp;lt; 0.001) average daily feed intake (ADFI), resulting in decreased (linear, P &amp;lt; 0.001) gain to feed ratio (G:F; Table). Decreasing NE also tended to increase (linear, P = 0.073) the percentage of removals, with no evidence of difference (P &amp;gt; 0.10) in mortality. Reducing NE worsened (linear, P &amp;lt; 0.001) caloric efficiency (CE) based on NRC nutrient loading values, but improved (linear, P ≤ 0.003) CE based on INRA (2008) or Brazilian Tables for Poultry and Swine (2017) nutrient loading values. When formulating diets using CVB (2021) nutrient loading values, decreasing NE did not influence CE (P &amp;gt; 0.10). For carcass characteristics, decreasing NE decreased (linear, P &amp;lt; 0.001) HCW, backfat depth, and carcass yield. However, decreasing NE increased (linear, P ≤ 0.024) loin depth and percentage lean. When considering CE on a carcass gain basis, decreasing NE worsened (linear, P ≤ 0.004) CE based on NRC or CVB nutrient loading values, but improved (linear, P &amp;lt; 0.001) CE based on INRA nutrient loading values. Decreasing NE resulted in no differences (P &amp;gt; 0.010) in CE based on Brazilian Tables nutrient loading values. These results suggest that the NRC database overestimates NE contributions of fibrous ingredients, such as wheat middlings and corn DDGS, while the INRA database underestimates their contributions to NE, whether CE is calculated based on live or carcass gain. Meanwhile, NE values in the CVB database appear to assess nutrient values more accurately for NE based on live gain but underestimate their value on a carcass basis. The Brazilian tables appear to underestimate the contributions of fibrous ingredients to dietary NE on a live basis, but more accurately value their contributions on a carcass basis.

143 Effect of increasing dietary net energy content at a constant lysine on feed intake and performance of 7 to 11 kg and 11 to 20 kg pigs

Abstract Information about NE requirements for nursery pigs is still limited. Therefore, 2 experiments were conducted to evaluate the effect of dietary NE contents on growth performance of 7 to 11 kg pigs (Exp. 1) and 11 to 20 kg pigs (Exp. 2). In Exp. 1, mixed-sex pigs (n = 192; PIC; initial body weight (BW) of 7.8 ± 1.07 kg] were assigned to 4 diets for 14 d. Diets 1 to 4 were formulated to contain 4 levels of NE (9.8, 10.1, 10.4 and 10.7 MJ/kg) and adequate in all AA with standardized ileal digestible (SID) Lys being constant at 1.42%. In Exp. 2, mixed-sex pigs (n = 192; PIC; initial BW of 11.2 ± 1.54 kg) were assigned to 4 diets for 21 d. Diets 1 to 4 contained 4 levels of NE (9.6, 9.9, 10.2 and 10.5 MJ/kg) and adequate in all AA (1.32% SID Lys). For both studies, there were 6 pen replicates (4 entire males and 4 gilts/pen) per treatment, and diets were based on corn, soybean meal, whey powder, wheat bran and soy oil. Pigs had ad libitum access to feed (mash) and water. Individual pigs and pen feed disappearance were weighed weekly to calculate average daily gain (ADG), average daily feed intake (ADFI), and feed efficiency gain to feed ratio (G:F). Data were analyzed by ANOVA using the GLM procedure of SAS with pen as the experimental unit. In Exp. 1, ADFI tended to decrease (quadratic; P ≤ 0.08) with increasing NE levels during d 0 to 7 and d 8 to 14. The ADG during d 0 to 7 tended to be greater (158, 192, 187 and 152 g for diets 1 to 4; quadratic; P = 0.08) at 10.1 MJ/kg NE; however, the overall ADG (d 0 to 14) was not affected by the NE levels. Although not significant, G:F, Lys utilization efficiency were greatest at 10.1 MJ/kg NE for the overall period. In Exp. 2, ADFI decreased (827, 783, 768 and 749 g for diets 1 to 4; linear; P = 0.05) with increasing NE levels during d 15 to 21 but was not affected (P &amp;gt; 0.05) for other periods. The ADG (d 8 to 14) tended to be greater at 9.6 MJ/kg NE (quadratic; P = 0.06) and G:F (d 15 to 21) tended to be greater at a dietary NE of 10.2 MJ/kg (linear; P = 0.10). However, the overall (d 0 to 21) ADG and G:F were not affected (P &amp;gt; 0.05) by NE levels. Although not significant, G:F and Lys utilization efficiency were greatest at a dietary NE of 10.2 MJ/kg for the overall period. These results indicate that G:F of 7 to 11 kg pigs and 11 to 20 kg pigs maximized at a dietary NE content of 10.1 MJ/kg and 10.2 MJ/kg, which correspond to 1.41 and 1.29 g SID Lys/MJ NE, respectively.

Influence of low-level tannin supplementation on comparative growth performance of Holstein and Angus × Holstein cross calf-fed concentrate-based finishing diets for 328 d.

The objective of the current study was to evaluate the effects of tannin and monensin supplementation in feedlot diets and breed (Holstein vs. Angus × Holstein) on growth performance, energetic efficiency, and carcass characteristics. Eighty purebred Holstein calves (HOL; initial body weight (BW) = 130 ± 5kg) and 80 Angus × Holstein calves (AXH; initial BW = 129 ± 6kg) were blocked by initial BW and randomly assigned to 40 pens. Dietary treatments consisted of a steam-flaked corn-based diet supplemented with (1) no feed additive (CON); (2) 30mg of monensin/kg of dry matter (DM; MON; Rumensin 90, Elanco, Greenfield, IN); (3) 1.5g tannin)/kg of DM (TAN; ByPro, 70% condensed tannin, SilvaFeed, Indunor, S.A., Buenos Aires, Argentina); (4) M + T, the combination of MON plus TAN dietary treatments. Data were analyzed as a randomized complete block in a 2 × 4 factorial arrangement of treatments, using pens as experimental units. There were no interactions (P > 0.05) between feed additives and breed. Supplemental MON increased (P ≤ 0.04) initial 112-d BW and gain efficiency. However, there were no dietary treatment effects (P > 0.10) on overall growth performance. Monensin supplementation decreased (P = 0.04) minimum daily ruminal temperature compared with other dietary treatments during July, but TAN did not affect ruminal temperature. Holstein steers had greater (P = 0.04) overall DM intake compared with AXH, with no difference (P = 0.19) in overall ADG, leading to increased (P < 0.01) gain efficiency for AXH compared with HOL. Dietary net energy for maintenance and gain, based on growth performance, were greater (P ≤ 0.01) for AXH vs HOL. Compared with HOL, AXH steers had greater (P ≤ 0.01) carcass weight, dressing percentage, kidney, pelvic, and heart fat, 12th rib fat thickness, longissimus area, and preliminary yield grade. Holstein steers had lower (P ≤ 0.04) minimum average ruminal temperature during June compared with AXH, with no differences (P ≥ 0.14) between breeds during July or August. Results indicate that feed additives did not appreciably affect steer growth performance and carcass characteristics, but crossbred AXH steers had greater growth performance, efficiency of dietary energy utilization, and carcass quality measures compared with HOL. This study observed a reduction (4.7%) in maintenance energy expenditure in AXH compared with HOL, implying in maintenance energy coefficient of 0.086 vs 0.082 for HOL and AXH, respectively.