Objective: We investigated the independent and interactive effects of dietary starch concentration and feeding management regimen on growth performance, carcass characteristics, and prevalence of liver abscesses in finishing beef cattle. Materials and Methods: Beef steers (n = 720) were assigned to 48 pens in a randomized complete block design, with treatments arranged in a 2 x 2 factorial (12 pens per treatment). Factors were finishing diets with either low (49.1%; CON) or high (64.4%; HOT) starch concentrations and feeding management regimens designed for consistent feed delivery (REG) or randomized variations (ERR) in both feed quantity (85% followed by 115% of the previous 4-d average randomly once per week) and delivery time (randomly delayed for 1, 2, 3, or 4 h twice per week). Results and Discussion: No interactions between diet and feeding management regimen were detected for growth performance, carcass outcomes, or liver abscess prevalence. Steers fed HOT had greater liver abscess frequency (55.1% vs. 33.4%) and a greater proportion of liver scars (46.7% vs. 34.0%) compared with CON. Steers consuming HOT also had less final BW, ADG, DMI, hot carcass weight, marbling score, and calculated YG versus CON. Feeding management regimen did not affect liver abscess frequency, growth performance, or carcass merit. Implications and Applications: Feeding a highstarch diet increased liver abscess prevalence and decreased growth and affected carcass outcomes. In contrast, erratic feeding management did not affect liver or production outcomes.

In livestock, exposure to stress initiates a series of biological signaling cascades that influence the animal's nutritional and immunological status. The duration of time an animal is exposed to stress may influence the magnitude of the response and determine if the resulting changes are beneficial or detrimental. Our study evaluated if biological responses to a stress challenge model using exogenous hormones are impacted differently if cattle are exposed to short-term (acute), long-term (chronic), or negative control (no stress hormones) treatments. Cattle that received a stress challenge had increased cortisol, glucose, and insulin concentrations. The stress challenge also influenced total white blood cell, monocyte, and eosinophil concentrations. Rumen fermentation end products were minimally influenced by stress treatment, but stress reduced the liquid passage rate. Therefore, the administration of stress hormones influenced biological indicators of nutritional and immunological function of growing steers. Additionally, administration of a chronic stress challenge resulted in longer alteration of some variables compared to steers that were acutely stressed.

Abstract Liver abscesses present significant challenges for the beef industry, yet understanding of the interplay between diet composition, eating behavior, and ruminal acidosis in finishing cattle and their effects on liver abscess prevalence and growth performance is lacking. Therefore, this study investigated the independent and interactive effects of dietary starch concentration and feed delivery regimen on growth performance, rumen buffering characteristics, carcass outcomes, and prevalence of liver abscesses in finishing beef steers. On d 0, beef steers [n = 720; body weight (BW) = 407 ± 4.53 kg) were sorted into 12 blocks according to BW and assigned to 1 of 4 treatments arranged as a 2 × 2 factorial (12 pens/interaction treatment; 24 pens/main effect) in a randomized complete block design. Treatments were finishing diets with low (49.1%; CON) or high (64.4%; HOT) starch concentration fed to steers receiving consistent feed delivery (REG) or randomized variations (ERR) in feed quantity (85% followed by 115% of the previous 4-d average once per week) and delivery time (delayed for 1, 2, 3, or 4 h twice per week). The 3 steers closest to the median BW in each pen were administered a 3-axis accelerometer ear-tag to quantify time spent ruminating and an indwelling rumen bolus to measure ruminal pH for the first 150 d of the study. Fecal score (1 = hard and dry consistency to 5 = water like consistency) and fecal pH were recorded on d 0, 56, 112, and before harvest. Daily dry matter intake (DMI) variability was greatest (P < 0.01; diet × feed delivery interaction) for CON + ERR, intermediate for HOT + ERR, and least for HOT + REG and CON + REG. No additional interactions (P ≥ 0.14) between diet and feed delivery regimen were observed. Feeding HOT increased total liver abscesses (P < 0.01) by 21.7 percentage points and liver scars (P < 0.01) by 12.7 percentage points compared with CON. Additionally, steers consuming HOT had less (P ≤ 0.05) final BW, average daily gain, DMI, gain-to-feed ratio, hot carcass weight, marbling score, and yield grade than CON. Steers fed HOT also had fewer daily rumination minutes (P < 0.01; diet × day interaction), lower fecal pH (P < 0.01; diet × day interaction) lower ruminal pH (P = 0.04), and less desirable fecal scores (P = 0.02) vs. CON. Feed delivery regimen did not affect (P ≥ 0.21) growth performance, rumen buffering characteristics, carcass traits, or liver abscess prevalence. Increasing the concentration of readily fermentable starch fed to finishing steers reduced growth and carcass performance, ruminal pH, and fecal pH, while increasing the proportion of liver abscesses. In contrast, inducing erratic DMI did not affect growth performance or carcass outcomes.

Objective: This study evaluated the effects of starch dilution with different sources of dietary fiber from terminal implant to slaughter on growth performance, energy utilization, and carcass characteristics of feedlot cattle. Materials and Methods: Steers (n = 416; initial BW = 372 +/- 2.67 kg) were allocated to 48 pens in a randomized complete block design. Pens of cattle (n = 12 per treatment) were assigned to 1 of 4 treatments consisting of diets based on steam-flaked corn, containing (1) 7.50% corn stalks on a DM basis fed for the entire feeding period (CON), (2) 14.75% corn stalks on a DM basis fed from terminal implant to slaughter (CS), (3) 9.50% wet distillers grains with solubles and 7.50% corn stalks on a DM basis fed from terminal implant to slaughter (WD), and (4) 19.00% wet distillers grains with solubles and 0.0% corn stalks on a DM basis fed from terminal implant to slaughter (NR). Six days before administration of the terminal implant, steers were transitioned to their treatment diets using a 2 -ration system, whereas CON consumed the same diet throughout the entire feeding period. Results and Discussion: As expected, performance (BW, DMI, ADG, G:F) was not different from d 0 of the study to dietary transition. Dry matter intake and calculated ME intake from dietary transition to slaughter were greatest for cattle consuming CS, intermediate for WD and CON, and least for NR. Final BW and ADG did not differ among treatments from dietary transition to slaughter; G:F was greatest for NR, intermediate for WD, and least for CS and CON. There was no difference in hot carcass weight, DP, marbling score, QG, YG, or percentage KPH among treatments. Steers consuming CS had greater 12th-rib s.c. fat thickness. The proportion of abscessed livers did not differ among treatments. Implications and Applications: Increasing the proportion of corn stalks in the diet after terminal implant administration increased DMI and ME intake with no effect on G:F. In contrast, removing corn stalks from the diet and increasing the proportion of wet distillers grains with solubles to provide an equivalent starch concentration reduced DMI and improved G:F.

To improve animal performance and modify growth by increasing lean tissue accretion, beef cattle production has relied on use of growth promoting technologies such as beta-adrenergic agonists. These synthetic catecholamines, combined with the variable inclusion of rumen degradable (RDP) and undegradable protein (RUP), improve feed efficiency and rate of gain in finishing beef cattle. However, research regarding the impact of beta-adrenergic agonists, protein level, and source on the ruminal microbiome is limited. The objective of this study was to determine the effect of different protein concentrations and beta-adrenergic agonist (ractopamine hydrochloride; RAC) on ruminal bacterial communities in finishing beef heifers. Heifers (n = 140) were ranked according to body weight and assigned to pens in a generalized complete block design with a 3 × 2 factorial arrangement of treatments of 6 different treatment combinations, containing 3 protein treatments (Control: 13.9% CP, 8.9% RDP, and 5.0% RUP; High RDP: 20.9% CP, 14.4% RDP, 6.5% RUP; or High RUP: 20.9% CP, 9.7% RDP, 11.2% RUP) and 2 RAC treatments (0 and 400 mg/day). Rumen samples were collected via orogastric tubing 7 days before harvest. DNA from rumen samples were sequenced to identify bacteria based on the V1-V3 hypervariable regions of the 16S rRNA gene. Reads from treatments were analyzed using the packages 'phyloseq' and 'dada2' within the R environment. Beta diversity was analyzed based on Bray-Curtis distances and was significantly different among protein and RAC treatments (P < 0.05). Alpha diversity metrics, such as Chao1 and Shannon diversity indices, were not significantly different (P > 0.05). Bacterial differences among treatments after analyses using PROC MIXED in SAS 9 were identified for the main effects of protein concentration (P < 0.05), rather than their interaction. These results suggest possible effects on microbial communities with different concentrations of protein but limited impact with RAC. However, both may potentially act synergistically to improve performance in finishing beef cattle.

Objective: This experiment evaluated effects of a single extended-release implant compared with 2 re-implant programs administered at either 120 d on feed (DOF) or 80 d before slaughter on growth performance, carcass characteristics, activity, and rumination time of feedlot steers slaughtered at 166, 180, 194, or 208 DOF.Materials and Methods: Using a randomized complete block design, steers (n = 6,840; initial BW = 370 +/- 7.74 kg) were randomly assigned to 108 pens across 12 treatments in a 3 x 4 factorial arrangement. Treatments were a single extended-release growth implant administered on d 0 (IMP), an extended-release growth implant administered on d 0 followed by a second implant at 120 DOF (REIMP+120), or an extended-release growth im plant administered on d 0 followed by a second implant administered 80 d before slaughter (REIMP-80); steers were slaughtered at 166, 180, 194, or 208 DOF. Three-axis accelerometer ear tags were applied to a random subset of steers (n = 1,080) to quantify rumination and activity minutes.Results and Discussion: Dry matter intake was reduced, which improved G:F for steers administered RE- IMP+120 and REIMP-80 compared with IMP. Re-im- planted steers tended to have heavier hot carcass weight (HCW) and had greater DP and LM area but less 12th- rib s.c. fat and marbling and lower YG. Choice carcasses were less frequent and Select carcasses were more frequent for re-implanted cattle than for IMP cattle. Final BW increased, concomitant with diminishing ADG and G:F as DOF increased. As DOF increased, there was an increase in HCW, the percentage of carcasses >477 kg, 12th-rib s.c. fat, marbling, YG, and DP. There were greater Choice and fewer Select carcasses with increased DOF. The proportion of steers exhibiting buller-steer syndrome was greatest for REIMP-80, intermediate for REIMP+120, and least for IMP. An implant x day interaction for activity minutes indicated that re-implanted steers had increased activity following re-implant.Implications and Applications: Administration of a second growth implant that overlapped the 200-d efficacy window of an extended-release implant improved G:F, HCW, and DP but decreased carcass fatness and reduced QG regardless of the timing of secondary implant administration.

An experiment was conducted to determine the effect of a concentrate diet containing Reed Sedge Peat (RSP) on nutrient digestibility, and serum glucose and insulin concentrations in mature exercised horses. The addition of RSP to the diet may effect nutrient digestibility and glucose metabolism in exercising horses. Six stock-type geldings (μ 546 kg), ranging from 8 to 19 yr of age, were fed a diet consisting of coastal Bermudagrass hay and a concentrate with or without RSP in a duplicated 3 × 3 Latin-square design. Three dietary treatments consisted of: control, no RSP (C); 10 lb/ton RSP (RSP10; Kent Nutrition Group, Muscatine, IA); and 20 lb/ton RSP added (RSP20). The 12-wk study consisted of 3 21-d adjustment periods followed by a 3-d fecal collection period. Total feces voided was collected every 4 h. Blood was collected 30 min pre-feeding, 30 min post-feeding, 8 h post-feeding, 30 min pre- Standard Exercise Test (SET); then 30 s, and 10, 30, 60, and 120 min post-SET. Horses were fed hay at a minimum 2% body weight per day and 2.2 kg/d of each dietary treatment. Feed and feces were analyzed for dry matter (DM), crude protein (CP), ether extract (EE), acid detergent fiber (ADF), neutral detergent fiber (NDF), ash, Ca, and P concentrations. Blood serum was analyzed for fasting insulin and glucose concentrations. Data for nutrient digestibilities, and serum glucose and insulin concentrations were analyzed using theProc Mixed Procedure of SAS v. 9.4. Significant differences between means were declared at P < 0.05. There was an effect of period on apparent DM (P = 0.02), NDF (P = 0.04), ADF (P = 0.01), Ca (P = 0.03), and P (P = 0.01) digestibility. There was an effect of treatment (P = 0.03) on pre- and post-prandial serum glucose concentrations. Horses consuming RSP20 (95.5 mg/dL) had greater overall mean serum glucose concentrations compared with horses consuming RSP10 (87.2 mg/dL) and C (86.6 mg/dL). Overall post-prandial serum insulin concentrations (17.81 uIU/mL) were greater (P < 0.01) compared with pre-prandial (7.1 uIU/mL) and 8 h post-prandial (6.52 uIU/mL). Immediately following exercise, mean serum glucose concentrations decreased (P < 0.01) from 86.43 mg/mL pre-SET to 80.13 mg/dL. Serum insulin concentrations decreased (P < 0.01) from 5.56 ulU/mL pre-SET to 3.05 ulU/mL post-SET. The data suggests no benefits were observed in nutrient digestibility when RSP was added to horses’ diets. However, greater glucose concentrations with the RSP20 diet may provide more energy for performance of the horse. Therefore, further research may be warranted to investigate effects of RSP on glucose and insulin dynamics in exercising horses.

Salmonella contamination of beef products, specifically from the incorporation of bovine lymph nodes into ground beef, remains a food safety concern. Current postharvest Salmonella mitigation techniques do not address Salmonella bacteria that are harbored in the lymph nodes, nor is it well understood how Salmonella invades the lymph nodes.

Objective: This study evaluated the effects of feeding beef cattle finishing diets with greater than 14.0% dietary CP and with or without ractopamine hydrochloride (RH) on growth performance, carcass merit, net energy utilization, and metabolizable protein balance. Materials and Methods: Heifers (n = 525) were assigned to 48 pens in a generalized complete block design, and pens of cattle were assigned randomly to 0 or 400 mg of RH/animal per day and 3 CP treatments in a 2 x 3 factorial arrangement (n = 8 pens/treatment) fed for 35 d before slaughter. Dietary protein treatments were steamflaked corn-based diets containing 13.9% CP, 8.9% RDP, and 5.1% RUP (CON); 20.9% CP, 14.4% RDP, and 6.5% RUP (High RDP); or 20.9% CP, 9.7% RDP, and 11.2% RUP (High RUP) on a DM basis. Results and Discussion: No RH x CP interactions were observed. Final BW, ADG, water disappearance, DMI, and G:F were not different among CP treatments. Dressing percentage was greater for cattle fed High RDP than for those fed High RUP, but other carcass outcomes RUP, intermediate for High RDP, and least for CON. CatRH. Dietary CP requirements were greater for cattle fed 400 compared with 0 mg of RH but did not exceed the CP supplied by CON, High RDP, or High RUP. Implications and Applications: Feeding greater than 14.0% CP does not negatively affect performance or carcass characteristics of finishing cattle, and the absence of interactions between CP and RH suggests that RH does not increase CP requirements above those provided in a typical finishing cattle diet.

This study evaluated starch dilution with different sources of fiber from terminal implant to harvest on feedlot cattle performance, rumen buffering characteristics, and carcass outcomes. Steers (n = 416) were allocated to 48 pens in a randomized complete block design and assigned to 1 of 4 dietary treatments. Treatments were steam-flaked corn-based diets: CON; 7.5% corn stalks fed for the entire feeding period or CON followed by CS; 14.8% corn stalks, WD; 9.5% wet distillers grains with solubles and 7.5% corn stalks, or NR; 19.0% wet distillers grains with solubles and 0.0% corn stalks fed from terminal implant to harvest. Steers were transitioned to CS, WD, and NR over 6 d using a two-ration system. Within each pen, 2 steers received an indwelling rumen pH bolus and a 3-axis accelerometer ear-tag to quantify rumination. Treatment differences were considered statistically significant when P < 0.10. Dry matter (DM) and metabolizable energy (ME) intake were greatest for cattle consuming CS, intermediate for WD and CON, and least for NR (P < 0.01). The average daily gain (ADG) did not differ among treatments (P = 0.18); however, feed efficiency (G:F) was least for NR, intermediate for WD, and greatest for CS and CON (P = 0.10). Steers consuming CS had more (P = 0.08) 12th rib fat than NR, WD, or CON, but no other differences (P ≥ 0.24) in carcass characteristics were observed. A treatment × day interaction (P < 0.01) was observed for daily rumination time and ruminal pH. Results suggest that increasing the concentration of corn stalks in the diet post-terminal implant increased DM and ME intake and rumination; replacing corn stalks with wet distillers grains with solubles improved G:F and reduced rumination with minimal impacts on ruminal pH.

Objective: This study evaluated the effects of Sweet Bran (SB) and wet distillers grains with solubles (WDGS) in the diet alone or in combination on performance and carcass characteristics of finishing beef cattle. Materials and Methods: For this study, steers (n = 455; 373 +/- 15.5 kg) were stratified by BW and previous antimicrobial treatment to 48 pens in a randomized complete block design (12 blocks, 4 pens per block) using pen as the experimental unit. Within block, pens of steers transitioned over 20 d to 1 of 4 dietary treatments based on steam-flaked corn, containing no corn-milling products (CON), 20% WDGS (WDGS20), 20% SB (SB20), or 20% SB and 10% WDGS (COMBO). Results and Discussion: Final BW and overall (d 0 to final) DMI and ADG were greater (P < 0.01) for WDGS20, SB20, and COMBO than for CON, but overall G:F (P = 0.48) was not different. Hot carcass weight was greatest (P = 0.04) for SB20 and WDGS20, intermediate for COMBO, and least for CON. Dressing percentage, marbling score, QG, 12th-rib fat, LM area, and KPH did not differ (P > 0.21). Yield grade tended (P = 0.09) to be greater for WDGS20 and SB20 than CON. No difference (P > 0.32) was observed between treatments for QG. Liver scores were not different (P = 0.47) among treatments. Empty body fat did not differ (P = 0.25), but empty BW was greater (P = 0.04) for WDGS20 and SB20 than COMBO and CON. No difference (P = 0.13) was observed for performance-calculated NE (Mcal/kg; maintenance or gain). Implications and Applications: The results of this study suggest that addition of WDGS, SB, or both into finishing diets based on steam-flaked corn increases DMI and subsequently improves performance of feedlot cattle.

This study evaluated the impacts of feeding a high-energy finishing diet during both the receiving and finishing period compared with a lower-energy receiving diet with adaptation to the finishing diet on health, performance, serum chemistry, ruminal pH, rumination, and carcass characteristics of high-risk feedlot cattle. Five truck-load blocks of steers (n = 101) and bulls (n = 299) were used in a generalized complete block design and randomly assigned to receive: 1) finishing diet for the entire feeding period (FIN) or 2) receiving diet for the first 56 d, followed by a transition to the finishing diet (REC). All cattle were fed ad libitum and consumed the same diet by day 74. A subset of cattle (n = 48) was randomly selected to quantify ruminal pH, temperature, and rumination time. Ultrasound images were collected on days 0, 74, and 146 to determine fat thickness over the 12th rib and rump, and carcass characteristics were determined after slaughter. Cattle fed FIN had less (P < 0.01) dry matter intake (DMI) from days 0 to 74, but DMI did not differ (P = 0.80) after day 74. From days 0 to final, DMI was 0.26 kg less for FIN compared with REC (P = 0.01). However, calculated metabolizable energy intake was not different from days 0 to 74 (P = 0.19), days 74 to final (P = 0.80), or overall (P = 0.78). Body weight (BW) on day 74 was greater (P < 0.01) and final BW tended to be greater (P = 0.10) for FIN compared with REC. Cattle consuming FIN had greater (P < 0.01) average daily gain and increased (P < 0.01) gain:feed from days 0 to 74. There were no differences (P ≥ 0.31) in health outcomes. On day 74, FIN had greater (P = 0.04) fat thickness over the rump and rib but did not differ (P ≥ 0.52) on day 146. Carcasses of FIN had greater (P = 0.04) hot carcass weight with no difference (P ≥ 0.11) in ribeye area, 12th rib fat thickness, yield grade, or quality grade. There was no difference (P = 0.18) in liver abscess rate. There was a diet × day interaction for blood urea nitrogen (P = 0.02) such that concentration decreased from days 0 to 28 in both treatments, but was less on day 28 for FIN. Ruminal pH was greater on days 2 and 61 and rumination time was less from days 0 to 28 for FIN (diet × day interaction; P < 0.01). Overall, these results suggest that providing a finishing diet fed ad libitum to high-risk calves upon arrival may be a viable alternative to a low-energy receiving diet.

Objective: Our objective was to estimate the effects of changes in feedlot diets and the availability of performance-enhancing technologies on growth performance and the carbon footprint of cattle feeding between 1990 and 2020. Materials and Methods: A model was developed to represent feedlot diets and technologies used in 1990 versus 2020 and evaluate changes in growth performance and carbon footprint. Byproduct feeds became more common between 1990 and 2020; thus, corn and dry roughage inclusion rates decreased. Estradiol-only implants and monensin were the available technologies in 1990, whereas in 2020 use of implants with combinations of trenbolone acetate and estradiol, monensin, and ractopamine hydrochloride (in the final 28 to 42 d) were common. Results and Discussion: In both 1990 and 2020 use of all available technologies increased final BW, ADG, G:F, and hot carcass weight compared with no technology. From 1990 to 2020 initial BW, final BW, ADG, G:F, hot carcass weight, and daily DMI increased. Total days on feed increased by 44 d from 1990 to 2020. Compared with no technology, use of technologies in both 1990 and 2020 decreased total greenhouse gas emissions per animal (CO2 equivalent, CO(2)e). Because cattle had greater days on feed in 2020, all sources of greenhouse gas emissions per animal increased compared with the values estimated in 1990. However, when expressed as CO(2)e/kg of BW gain, emissions have decreased by 4.4% because of greater total BW gain in 2020 versus 1990. Implications and Applications: Feedlot cattle decreased relative emissions from 4.78 kg of CO(2)e/kg of BW gain in 1990 to 4.58 kg of CO(2)e/kg of BW gain in 2020. Overall, feedlots in 2020 produced 47.5% more BW gain with 1.4% less cattle, while only increasing total CO(2)e by 39.5%. Therefore, changes in available technologies and diet formulations have improved efficiency and reduced the carbon footprint of feedlot cattle production in the past 30 yr.

To improve animal performance and modify growth by increasing lean tissue accretion, beef cattle production has relied on use of growth promoting technologies such as beta-adrenergic agonists. These synthetic catecholamines, combined with the variable inclusion of rumen degradable (RDP) and undegradable protein (RUP), may improve feed efficiency and rate of gain in finishing beef cattle. However, the impact of beta-adrenergic agonists and protein level and source on the ruminal microbiome is limited. The objective of this study was to determine the effect of different protein concentrations and beta-adrenergic agonist (ractopamine hydrochloride; RAC) on ruminal bacterial communities in finishing beef heifers. Heifers (n = 140) were ranked according to body weight and assigned to pens in a randomized complete design to 6 different treatments, containing 3 protein treatments (Control: 13.9% CP, 8.8% RDP, and 5.0% RUP; High RDP: 20.9% CP, 13.4% RDP, 6.1% RUP; or High RUP: 20.9% CP, 9.1% RDP, 10.4% RUP) and 2 RAC treatments (0 and 400 mg/day). Rumen samples were collected from heifers by oral lavage 7 days before harvest. The DNA from the samples were sequenced to identify bacteria based on the V1-V3 hypervariable regions of the 16S rRNA gene using the Illumina MiSeq. Sequences and data from the treatments were analyzed using the R environment and PROC MIXED in SAS 9.4 (SAS Inst.; Cary, NC). Beta diversity was analyzed using PERMANOVA based on PCoA Bray-Curtis distances and were significant among the treatments (P < 0.05). Alpha diversity metrics such as Chao1 and Shannon diversity indices were not significantly different (P > 0.05). Differences among treatments at variable taxonomic levels after analyses through DESeq2 were significantly different for the main effects of protein and RAC, as well as their interaction (P < 0.05). These results suggest possible effects on the microbial communities, potentially acting synergistically to improve performance.

This study evaluated the effects of Sweet Bran (SB) and wet distillers grains with solubles (WDGS) in the diet alone or in combination on physically effective neutral detergent fiber (peNDF), ruminal pH, and rumination behavior of finishing beef cattle. For this study, 455 steers (373 ± 15.5 kg) were allocated to 48 pens in a randomized complete block design. Treatments (n = 12 pens per treatment) were one of four steam-flaked corn-based diets containing no corn-milling products (CON), 20% WDGS (WDGS20), 20% SB (SB20), or 20% SB and 10% WDGS (COMBO). Within each pen, two steers were randomly selected to receive an indwelling ruminal pH bolus to quantify ruminal pH and a 3-axis accelerometer tag to measure rumination for the first 92 d of the study. Diet samples were collected weekly to determine particle size, neutral detergent fiber (NDF) concentration, and peNDF. Physically effective NDF was calculated using both the proportion of particles > 4.0 mm (peNDF4.0 ) and the proportion of particles > 8.0 mm (peNDF8.0). The percentage of particles > 4.0 mm was greatest (P < 0.01) for CON, intermediate for SB20, and least for WDGS20 and COMBO. Both NDF (P < 0.01) and peNDF4.0 (P < 0.01) were greatest for COMBO, intermediate for WDGS20 and SB20, and least for CON. The percentage of particles > 8.0 was greatest (P < 0.01) for CON, intermediate for WDGS20 and SB20, and least for COMBO, but peNDF8.0 did not differ (P = 0.40). A diet × day interaction (P < 0.01) was observed for daily rumination minutes per kg of DMI, NDF, peNDF4.0, and peNDF8.0. A diet × hour interaction (P < 0.01) was observed where CON cattle spent less time ruminating at 0800 and 1000 h in a 24 h period. Daily ruminal pH was greatest (P < 0.01) for COMBO, intermediate for SB20 and WDGS20, and least for CON. A diet × hour interaction (P < 0.01) was also observed for circadian ruminal pH, where pH was least for CON from 0800 to 1800 h. Relationships between peNDF, rumination behavior, and ruminal pH observed in this study suggest that SB and WDGS similarly enhance rumen buffering capacity when steam-flaked corn is replaced in the diet.

This study evaluated the effects of a single slow-release implant compared to two re-implant programs administered at either 120 days on feed (DOF) or 80 days from harvest on performance, carcass characteristics, and activity of serially harvested feedlot cattle. Using a randomized complete block design, steers (n = 4,680) were randomly assigned to 72 pens and 1 of 12 treatments in a 3 × 4 factorial arrangement. Treatments were either a slow-release implant (SR), an initial slow-release implant followed by re-implant at 120 DOF (SR+RI-120), or an initial slow-release implant followed by re-implant 80 days from harvest (SR+RI-80) administered to cattle harvested at 166, 180, 194, or 208 DOF. A 3-axis accelerometer ear-tag was used in a subset (n =1,080) of animals to quantify rumination time and activity. No interactions (P ≥ 0.09) were observed for implant × DOF. Implant did not affect (P ≥ 0.25) final BW, ADG, or DMI, but re-implanted steers had a greater (P < 0.01) G:F ratio than SR. Re-implanted steers also had greater (P ≤ 0.03) HCW, dressed yield, and ribeye area, but less (P < 0.01) backfat, marbling, and empty body fat (EBF) compared to SR. Re-implanted steers had less (P < 0.01) choice and yield grade 4 and 5 carcasses than SR steers. As DOF increased, HCW, dressed yield, backfat, marbling, and EBF increased linearly (P < 0.01). The percentage of choice and yield grade 4 and 5 carcasses also increased (P < 0.01) linearly with additional DOF. An implant × day effect (P < 0.01) for weekly activity minutes suggests re-implanted steers had greater activity after re-implant administration. Re-implanting within the payout period of a slow-release implant increases feed efficiency, HCW, dressed yield, and activity minutes, but decreases carcass fatness and reduces quality grade regardless of timing of secondary implant administration.

Both dietary ingredients and technology used in the feedlot cattle industry have evolved in the past 30 years. As consumer concern for the sustainability of the feedlot cattle production increases, it is important to understand how production efficiency and greenhouse gas emissions have changed in this period. For this study, a model was developed to represent feedlot diets and technologies used in 1990 vs. 2020 and evaluate changes in growth performance and carbon footprint. Dietary changes from 1990 to 2020 included the use of byproduct feeds while decreasing corn and dry roughage inclusion rates. In 1990, available technologies included estradiol-only implants and monensin as a feed additive; whereas in 2020 use of combination implants including both trenbolone acetate and estradiol, monensin, and ractopamine hydrochloride (in the final 28 to 42 d) were common. In both 1990 and 2020 use of available technologies increased final body weight (BW), average daily gain (ADG), feed efficiency, and hot carcass weight (HCW) compared to no technology. From 1990 to 2020 initial BW, final BW, ADG, gain to feed ratio, and HCW increased, and dry matter intake decreased. Total days on feed (DOF) also increased by 43 days from 1990 to 2020. Compared to no technology, use of technologies in both 1990 and 2020 decreased total greenhouse gas emissions per animal (CO2e). Because cattle had greater DOF in 2020 than 1990, all sources of greenhouse gas emissions per animal increased. However, when expressed as CO2e/kg BW gain, emissions have decreased by 12.6% because of greater total BW gain in 2020. Feedlots in 2020 produced 48.15% more BW gain with 6.7% less cattle, while only increasing total CO2e by 23.42%, indicating changes in technologies and diet formulations have improved efficiency and reduced the carbon footprint of feedlot cattle production in the past 30 years.

An experiment was conducted to determine the effect of a concentrate diet containing Reed Sedge Peat (RSP) on nutrient digestibility, and serum glucose and insulin concentrations in mature exercised horses. The addition of RSP to the diet in horses may be beneficial to increasing nutrient digestibility and performance factors of the horse. Six stock-type geldings, ranging from 8 to 19 yr of age, in a duplicated 3 × 3 Latin-square design were fed a diet consisting of Coastal Bermudagrass hay and a concentrate with or without RSP. Three diet treatments consisted of: control, no RSP added (C); 4.5 kg/ton RSP added (RSP10; Kent Nutrition Group, Muscatine, IA); and 9.0 kg/ton RSP added (RSP20). The 12-wk study consisted of 3 21-d adjustment periods followed by 3-d fecal collections. Blood collections were taken pre- and post-prandial, before, and immediately following a Standard Exercise Test (SET) on d 21 of each period. Horses were fed hay at 2% body weight per day and 2.2 kg/d of a concentrate diet with or without added RSP. Representative samples of feed and feces were analyzed for dry matter, crude protein (CP), crude fiber, ether extract, acid detergent fiber (ADF), neutral detergent fiber, and ash content. Serum was analyzed for glucose and insulin concentrations by Michigan State University Veterinary Diagnostic Endocrinology Department. Data for nutrient digestibilities, and serum glucose and insulin concentrations were analyzed using the Proc Mixed Procedure of SAS v. 9.4. Significant differences between means were declared at P < 0.05. There was an effect of period on mean apparent ADF (P = 0.031), CP (P < 0.001), and Ca (P = 0.034) digestibility. There was an effect of treatment (P = 0.035) and period (P < 0.001) pre- and post-prandial serum glucose concentrations. Horses consuming RSP20 had higher (P < 0.05) pre- and post-prandial glucose concentrations as compared with horses consuming RSP10 and C. Post-prandial serum insulin concentrations were higher (P < 0.001) in response to horses consuming the concentrate diet. Immediately following exercise, serum insulin concentrations decreased (P < 0.001). Results from this experiment indicate that mature horses consuming RSP20 had increased post-prandial glucose concentrations as compared with horses consuming C and RSP10 indicating a potential benefit for glucose availability. Further research may be warranted to investigate effects of RSP on glucose and insulin dynamics in horses.

This study evaluated impacts of feeding a finishing diet throughout both the receiving and finishing period compared to a receiving diet with adaptation to the finishing diet on health, performance, ruminal pH, and rumination of high-risk feedlot cattle. Five truck-load blocks of steers and bulls (n = 400) were used in a generalized complete block design and assigned to receive: 1) finishing diet for the entire feeding period (FIN) or 2) receiving diet for the first 56 d, followed by transition to the finishing diet (REC). All cattle were consuming the same diet on d 74. A subset of cattle (n = 48) were randomly selected to quantify ruminal pH, temperature, and rumination time. Ultrasounds were completed on d 0, 74, and 146 to determine fat thickness. Cattle fed REC had greater (treatment × day; P < 0.01) DMI from d 1 to 67 but less DMI from d 74 to 82, and DMI did not differ from d 83 to 174. Energy intake (treatment × day; P < 0.01) was greater for FIN from d 14 to 75. Cattle consuming FIN had greater (P ≤ 0.01) ADG and BW and improved (P < 0.01) gain:feed from day 0 to 74. At d 174, BW of FIN was 9.6 kg greater (P = 0.02). On d 74, FIN had greater (P ≤ 0.05) fat thickness but did not differ (P ≥ 0.61) at d 146. There was no difference (P ≥ 0.31) in health outcomes. Ruminal pH (treatment × day; P < 0.01) was greater for FIN on d 2 and 61, and rumination time was less (P < 0.01) for FIN from d 0 to 28. Overall, these results suggest providing a finishing diet to high-risk calves upon arrival may be a viable alternative to a traditional receiving diet.

We evaluated the accuracy of acid insoluble ash (AIA) as a digestibility marker in feedlot cattle diets containing corn-milling byproducts and examined the effect of fecal sampling frequency on digestibility estimates. Steers (n = 6) were used in a crossover split-plot design where 3 steers per period were assigned to 1 of 2 diets [receiving (REC) containing 19% roughage and 38% Sweet Bran™ or finishing (FIN) containing 8% roughage and 20% Sweet Bran] typical of those used in the beef feedlot industry. Steers were limit fed at 2.0% of initial body weight. After a 21-d adaptation period, steers were housed in metabolism crates for 7 d of total collection (TC) of feed and feces and simultaneous collection of fresh manure grab samples twice daily to calculate nutrient digestibility from AIA. Grab samples were then averaged to represent 7 (7dAIA), 5 (5dAIA), 3 (3dAIA) and 1 (1dAIA) days of the collection period. No interactions (P ≥ 0.13) were observed for DM, OM or NDF digestibility between diet and method of estimating digestibility. Digestibility of DM and OM were greater (P < 0.01) for FIN than for REC, and NDF digestibility was less (P < 0.01) for FIN than REC. Both DM and OM digestibility were greater (P < 0.01) for AIA estimates than for TC; however, estimates with 7dAIA were less than 3dAIA and 1dAIA, but not different from 5dAIA. Similarly, NDF digestibility was greater (P < 0.01) for all AIA estimates than for TC, but 7dAIA and 5dAIA were less than 1dAIA and not different from 3dAIA. A treatment × method interaction (P = 0.02) occurred for ADF digestibility. These data suggest that AIA over-estimated digestibility of beef feedlot diets containing corn-milling byproducts, but accuracy improved with greater grab sampling frequency.