Effect of stocker management program on beef cattle skeletal muscle growth characteristics, satellite cell activity, and paracrine signaling impact on preadipocyte differentiation

The objective of this study was to determine the effect of different stocker management programs on skeletal muscle development and growth characteristics, satellite cell (SC) activity in growing-finishing beef cattle as well as the effects of SC-conditioned media on preadipocyte gene expression and differentiation. Fall-weaned Angus steers (n = 76; 258 ± 28 kg) were randomly assigned to 1 of 4 stocker production systems: 1) grazing dormant native range (NR) supplemented with a 40% CP cottonseed meal-based supplement (1.02 kg ∙ steer–1 ∙ d–1) followed by long-season summer grazing (CON, 0.46 kg/d); 2) grazing dormant NR supplemented with a ground corn and soybean meal-based supplement fed at 1% of BW followed by short-season summer grazing (CORN, 0.61 kg/d); 3) grazing winter wheat pasture (WP) at high stocking density (3.21 steers/ha) to achieve a moderate rate of gain (LGWP, 0.83 kg/d); and 4) grazing winter WP at low stocking density (0.99 steers/ha) to achieve a high rate of gain (HGWP, 1.29 kg/d). At the end of the stocker (intermediate harvest, IH) and finishing (final harvest, FH) phases, 4 steers / treatment were harvested and longissimus muscles (LM) sampled for cryohistological immunofluorescence analysis and SC culture assays. At IH, WP steers had greater LM fiber cross-sectional area than NR steers; however, at FH, the opposite was observed (p \u3c 0.0001). At IH, CORN steers had the lowest Myf-5+:Pax7+ SC density (p = 0.020), while LGWP steers had the most Pax7+ SC (p = 0.043). At FH, CON steers had the highest LM capillary density (p = 0.003) and their cultured SC differentiated more readily than all other treatments (p = 0.017). At FH, Pax7 mRNA was more abundant in 14 d-old SC cultures from HGWP cattle (p = 0.03). Preadipocytes exposed to culture media from proliferating SC cultures from WP cattle isolated at FH had more PPARγ (p = 0.037) and less FABP4 (p = 0.030) mRNA expression compared with NR cattle. These data suggest that different stocker management strategies can impact skeletal muscle growth, SC function, and potentially impact marbling development in growing-finishing beef cattle

Associations between residual feed intake and apparent nutrient digestibility, in vitro methane-producing activity, and volatile fatty acid concentrations in growing beef cattle

The objectives of this study were to examine the relationship between residual feed intake (RFI) and DM and nutrient digestibility, in vitro methane production, and volatile fatty acid (VFA) concentrations in growing beef cattle. Residual feed intake was measured in growing Santa Gertrudis steers (Study 1; n = 57; initial BW = 291.1 ± 33.8 kg) and Brangus heifers (Study 2; n = 468; initial BW = 271.4 ± 26.1 kg) fed a high-roughage-based diet (ME = 2.1 Mcal/kg DM) for 70 d in a Calan-gate feeding barn. Animals were ranked by RFI based on performance and feed intake measured from day 0 to 70 (Study 1) or day 56 (Study 2) of the trial, and 20 animals with the lowest and highest RFI were identified for subsequent collections of fecal and feed refusal samples for DM and nutrient digestibility analysis. In Study 2, rumen fluid and feces were collected for in vitro methane-producing activity (MPA) and VFA analysis in trials 2, 3, and 4. Residual feed intake classification did not affect BW or BW gain (P \u3e 0.05), but low-RFI steers and heifers both consumed 19% less (P \u3c 0.01) DMI compared with high-RFI animals. Steers with low RFI tended (P \u3c 0.1) to have higher DM digestibility (DMD) compared with high-RFI steers (70.3 vs. 66.5 ± 1.6% DM). Heifers with low RFI had 4% higher DMD (76.3 vs. 73.3 ± 1.0% DM) and 4 to 5% higher (P \u3c 0.01) CP, NDF, and ADF digestibility compared with heifers with high RFI. Low-RFI heifers emitted 14% less (P \u3c 0.01) methane (% GE intake; GEI) calculated according to Blaxter and Clapperton (1965) as modified by Wilkerson et al. (1995), and tended (P = 0.09) to have a higher rumen acetate:propionate ratio than heifers with high RFI (GEI = 5.58 vs. 6.51 ± 0.08%; A:P ratio = 5.02 vs. 4.82 ± 0.14%). Stepwise regression analysis revealed that apparent nutrient digestibilities (DMD and NDF digestibility) for Study 1 and Study 2 accounted for an additional 8 and 6%, respectively, of the variation in intake unaccounted for by ADG and mid-test BW0.75. When DMD, NDF digestibility, and total ruminal VFA were added to the base model for Study 2, trials 2, 3, and 4, the R2 increased from 0.33 to 0.47, explaining an additional 15% of the variation in DMI unrelated to growth and body size. On the basis of the results of these studies, differences in observed phenotypic RFI in growing beef animals may be a result of inter-animal variation in apparent nutrient digestibility and ruminal VFA concentrations

Assessment of dry-aged beef from commercial aging locations across the United States

Modern dry-aging is a culinary-inspired practice that involves storing meat at refrigerated temperatures without protective packaging. The dry-aging process has been observed to create unique flavors. The objective of the current study was to survey commercial dry-aging facility environments and observe palatability differences related to consumer acceptance. Seventy-two bone-in beef strip loins (Institutional Meat Purchase Specification #175) were acquired. Strip loins were randomly assigned to each of ten commercial dry-aging facilities. Additionally, a set of strip loins were wet-aged at the University of Idaho meat laboratory. Strip loins were shipped overnight to respective aging locations and dry-aged for 45-days then returned overnight to the University of Idaho meat laboratory. Strip loins were fabricated into steaks, vacuum packaged, and then frozen until further analyzed. Commercial dry-aging facility cooler conditions were observed to be different (P 0.05) among treatment-locations. Consumer taste panels indicated a difference (P < 0.01) in acceptability (6.27–7.24), tenderness (6.65–7.54), and flavor (5.58–6.79) based on aging treatment-location. Overall, the findings indicate that conditions within individual dry-aging facilities aid in producing unique dry-aged beef flavors.Funded by the Idaho Beef Council. We gratefully acknowledge Idaho Beef Council’s financial support (AG3963

Survey of beef carcass quality graded in Tabasco State, Mexico

A survey of beef carcass grading included 22 294 carcasses produced in tropical humid (Am) and sub-humid (Aw) climates subjected to the Mexican norm NMX-FF-078-SCFI-2002, between November 2009 and February 2010, at the No. 51 Federal Inspected Abattoir, in Tabasco State. The aim was to identify areas for improvement of carcass quality as influenced by four gender groups (young bull or heifer, up to 2 years of age; mature bull or cow), using five basic evaluation criteria: 1) maturity (age), 2) conformation (muscularity), 3) meat color, 4) fat color, and 5) subcutaneous fat distribution. Quality grades were designated: Supreme, Select, Standard, Commercial and Out of Grade. The effect of gender groups on the final quality grade and on each of the five criteria assessed was expressed as percentage proportions of the total number of observations per gender group. Carcasses with final classification as Select were present only in the young bull (18.7%) and heifer (1.1%) groups. Young bull and heifer carcasses were most frequently Standard grade, while those of mature bulls and cows were mostly Commercial grade and Out of grade. No carcass merited a final grade of Supreme due to inadequate conformation. It may be concluded that this application of the Mexican beef carcass classification norm in question to a sample population of tropically-produced carcasses highlights an industry capable of producing slaughter animals of early age, with carcasses showing adequate meat and fat color and subcutaneous fat distribution, but wanting improved conformation

Evaluation of Strategies to Improve the Environmental and Economic Sustainability of Cow&ndash;Calf Production Systems

Grazing cow&ndash;calf production systems account for 60 to 70% of the greenhouse gas emissions of U.S. beef production. The objective of this analysis was to evaluate the importance of management strategies (cow maintenance energy requirements, reproductive efficiency, forage nutritive value, and forage yield) on the sustainability of cow&ndash;calf production systems using a sensitivity analysis in a production systems model. The Beef Cattle Systems Model was used to simulate a cow&ndash;calf production system in the Kansas Flint Hills using Angus genetics over a 24 year time period. The model was modified to create variation among cow herds in the base net energy for the maintenance requirement (NEm_Req), postpartum interval (PPI), grazed forage digestibility (Forage_TDN), and forage yield per hectare (Forage_Yield). The model was run for 1000 iterations/herds of a 100-cow herd. A stepwise regression analysis in conjunction with standardized regression analysis was used to identify important predictors of an indicator of greenhouse gas (GHG) emission intensity, dry matter intake per kilogram weaned, and two indicators of economic sustainability, winter feed use and returns over variable costs, using R statistical software. The most important predictor of DMI per kilogram weaned was calf weaning weight followed by NEm_Req, whereas returns over variable costs were primarily influenced by kilograms weaned per cow exposed and total purchased feed (supplement + winter feed), which were strongly influenced by NEm_Req and Forage_Yield, respectively. In conclusion, decreasing the net energy required for maintenance improved both economic and environmental sustainability, and increasing forage yield and length of the grazing season improved economic sustainability, implying that these strategies should be primary targets to enhance the sustainability of cow&ndash;calf production systems

Replacing Fertilizer with Dried Distillers’ Grains in Stocker Cattle Systems on Southern Great Plains Old World Bluestem, USA

The objective was to examine the effects of dried distillers’ grains supplementation and fertilization strategies on the cattle performance and resource use efficiency of stocker cattle grazing on Plains Old World bluestem. Over 4 consecutive years, heifers and steers (average n = 239) were randomly assigned to 1 of 4 treatments: (1) low input, low stocking density, and no fertilizer or distillers grains supplementation (LOW); (2) high stocking density and no fertilizer with distillers grains supplementation (DDGS); (3) high stocking density and 90 kg of nitrogen/ha with no distillers grains supplementation (NFERT); (4) high stocking density, 90 kg of nitrogen/ha, and 39 kg of phosphorus/ha with no distillers grains supplementation (NPFERT). Cattle grazed in the pastures from mid-May to mid-September each year, except for 2011, when the experiment ended in July due to lack of forage. Data were analyzed using a linear model with fixed effects of treatment, year, and treatment × year (R software). Nitrogen use efficiency (retained/inputs) was affected by a treatment × year interaction, where LOW had the greatest efficiency in all years and DDGS was greater than NFERT and NPFERT in all years except 2012, with NFERT and NPFERT being not different in all years. The estimated total carbon equivalent emissions were greater for DDGS, NFERT, and NPFERT than LOW, but the carbon footprint (kg CO2eq/kg weight gain) was lesser for LOW and DDGS, which were not different, than NFERT and NPFERT, which were also not different. Replacing nitrogen fertilizer with dried distiller’s grains improved the cattle performance and the efficiency of resource use, and could be a viable economic alternative to traditional systems

Using Genetic Panels to Predict Tenderness in Beef Cattle

Genetic panel use as a selection tool has grown in popularity in the beef industry. The objective of the study was to determine whether beef cattle genetically selected for tenderness generated a tender product. Igenity® (IT) panel results were provided by a cattle producer for 52 steers, which were harvested at a commercial harvest facility. Boneless strip loins (Institutional Meat Purchase Specifications #180; United States Department of Agriculture [USDA] Choice, n = 32; USDA Prime n = 20) were collected from the left side of each carcass and transported to the University of Idaho Meat Science Laboratory. Four steaks were cut from each subprimal and assigned to aging periods of 7, 14, and 21 d for Warner-Bratzler Shear Force (WBSF) analysis or 21 d for consumer sensory analysis. Carcasses were assigned to tenderness groups based on their IT tenderness indexes (Low IT, 3–6, n = 30; High IT, 7–10, n = 22). Data were analyzed using the mixed model procedure of SAS version 9.4 (SAS Institute Inc., Cary, NC). An interaction was observed between tenderness group and USDA quality grade (P = 0.015) when analyzing WBSF. All of the cattle had less than 4.14 kg of WBSF; however, USDA Prime steers that were in the High IT tenderness group produced more tender steaks than High IT USDA Choice, Low IT USDA Prime, and Low IT USDA Choice steers. Consumers were not able to detect tenderness differences between IT tenderness groups (P = 0.11) or USDA quality grades (P = 0.11), but they found USDA Prime steaks to be more acceptable (P = 0.01), juicier (P = 0.01), and more flavorful (P = 0.02) than USDA Choice steaks. In conclusion, regardless of tenderness group, USDA Prime steaks were preferred by consumers over USDA Choice steaks in terms of flavor, juiciness, and acceptability

Net Conversion of Human-Edible Vitamins and Minerals in the U.S. Southern Great Plains Beef Production System

Beef is a good source of several vitamins and minerals but data on the net contribution to the human diet is lacking. The objective was to quantify the net nutrient contribution of the beef supply chain to provide vitamins and minerals to the human diet. Beef cattle production parameters for the beef supply chain were as described by Baber et al., 2018 with the red and organ meat yield from each production segment estimated using literature values of serially-harvested beef cattle. Nutrient concentration of feeds was acquired from feed composition tables in nutrient requirement texts, and the nutrient concentration of beef and organ meats was based on 2018 USDA Food and Nutrient Database for Dietary Studies. The nutrient absorption coefficients of feeds, red meat, and organs were acquired from the literature. The human-edible conversion ratio was &gt;1.0 for phosphorus when only red meat yield was considered indicating that the beef supply chain produced more human-edible phosphorus than it consumed. When organ meats were included, riboflavin, niacin, choline, and phosphorus had conversion ratios &gt;1.0. After adjusting for the absorption of nutrients, the beef supply chain was a net contributor of niacin and phosphorus in the human diet when accounting for red meat yield only, but when including organ meats, iron, riboflavin, and choline also had conversion ratios &gt;1.0. The maximum proportion of corn in the corn grain plus distillers&rsquo; grains component of the feedlot diets for the absorbable conversion ratio to be &ge;1 ranged from 8.34 to 100.00% when only red meat yield was considered and from 32.02 to 100.00% when red and organ meats were considered. In conclusion, the current beef production system in the Southern Great Plains produces more human-absorbable iron, phosphorus, riboflavin, niacin, and choline to the human diet than is consumed in the beef supply chain

Assessing outcomes of genetic selection panels to predict marbling in crossbred beef cattle

The objective of this study was to evaluate the effectiveness of genetic panel marbling indexes [Igenity (IT) and PredicGEN (PG)] to predict marbling and tenderness of crossbred cattle. Steers (n = 23) were harvested at the University of Idaho Meat Science Laboratory, and blood samples were submitted to Neogen and Zoetis for genetic panel analysis. Forty-eight hours postharvest, one boneless strip loin was collected from each carcass, and six 2.54-cm thick steaks were cut from each strip loin. Steaks were aged for 14 and 21 d and assigned to consumer sensory evaluation or Warner–Bratzler Shear Force (WBSF) analysis. Results were analyzed using the Mixed Model procedure of the Statistical Analysis System (SAS Institute, Inc., Cary, NC). Carcasses were grouped by marbling index score into Low IT (IT indexes 3–6; n = 16; marbling score (MS) = 410), High IT (IT indexes 7–10; n = 7; MS = 496), Low PG (PG index \u3c50; n = 9; MS = 398), or High PG (PG index ≥50; n = 14; MS = 458). Mean MS was observed to be greater in High IT steaks than Low IT (P \u3c 0.01) and greater in High PG steaks than Low PG (P = 0.01). There was a trend observed in WBSF between IT marbling groups (P = 0.06); however, no difference in WBSF was observed between PG marbling groups (P = 0.83). Consumers did not report differences between IT marbling groups in terms of acceptability (P = 0.99) or tenderness (P = 0.24). Additionally, consumers could not detect differences between PG marbling groups in terms of acceptability (P = 0.75) or tenderness (P = 0.40). Consumers consistently preferred Choice steaks over Select steaks in terms of acceptability (P = 0.02) and tenderness (P = 0.02). In conclusion, though consumers were not able to tell the difference between steaks from each of the genetic panels, using genetic panels to predict marbling, in conjunction with proper nutrition and handling practices, could be a beneficial tool to producers making decisions about retaining ownership at the feedlot