A. M. Stelzleni

Chemical properties of cow and beef muscles: benchmarking the differences and similarities.

The objective of this study was to identify muscles from cow populations that are equivalent or may possibly be made equivalent to muscles from A-maturity, Select-grade cattle in terms of chemical, compositional, and color characteristics. Objective color, expressible moisture, proximate composition, pH, heme iron concentration, and total collagen content were determined for 9 muscles (M. gluteus medius, M. infraspinatus, M. longissimus dorsi, M. psoas major, M. rectus femoris, M. tensor fascia latae, M. teres major, M. triceps brachii lateral-head, and M. triceps brachii long-head) from 15 cattle from each of 5 commercially identified populations [fed beef cows (B-F), non-fed beef cows (B-NF), fed dairy cows (D-F), non-fed dairy cows (D-NF), and A-maturity, Select-grade cattle (SEL)]. Muscles from B-F and B-NF populations were more similar to the SEL than were the D-F and D-NF. There were 2 muscles, the M. infraspinatus and M. teres major, from the population of B-F that were similar, physically and chemically, to SEL in most traits. The majority of the 9 muscles from the cows did not differ (P < 0.05) from SEL for percentage expressible moisture, proximate composition, and total collagen content. However, notable differences in pH, objective color L*, total pigment content, and heme iron content existed between cow populations and SEL. The muscles from SEL had significantly (P < 0.05) lower total pigment and heme iron concentrations. These differences likely relate to the visual appearance of muscles from the different populations of cattle. Two of the 9 muscles studied were similar among cow populations and A-maturity, Select-grade beef.

Effect of days on concentrate feed on sensory off-flavor score, off-flavor descriptor and fatty acid profiles for selected muscles from cull beef cows

The effects of short-term realimentation (0, 42 or 84 days) of cull beef cows (n=24) and post-mortem aging (10 or 20 days) of selected muscles on sensory off-flavor score, off-flavor descriptors of m. Gluteus medius (GLM), m. Longissimus lumborum (LOL), m. Triceps brachii-long head (LON) and m. Rectus femoris (REF) and fatty acid profiles (GLM, LOL and LON) were researched. Post-mortem aging did not affect sensory off-flavor detection or the interaction with muscle or treatment (P⩾0.65). Sensory off-flavor scores were lower (P<0.01) for steaks that were derived from cull cows fed a concentrate diet for at least 42days. As well, the number of samples that had detectable off-flavors decreased (P<0.01) when cull cows were fed for 42days. Realimentation did have an effect on fatty acid profiles (P<0.05). However, regression analysis showed changes in sensory off-flavor score were not influenced (P>0.05) by alterations in fatty acid profiles.

Effect of ractopamine-HCl supplementation for 28 days on carcass characteristics, muscle fiber morphometrics, and whole muscle yields of six distinct muscles of the loin and round

This study evaluated the effects of ractopamine-HCl (RAC) supplementation on carcass characteristics, muscle fiber morphometrics, and tenderness. Thirty-four steers (2 groups, 4 replicates) were fed RAC or carrier for 28 days prior to harvest. Seventy-two hours postmortem, the Longissimus lumborum (LL), Gracilis (GRA), Vastus lateralis (VL), Rectus femoris (RF), Semimembranosus (SM), and Adductor (ADD) were dissected from each carcass. Commodity weight, denuded weight, and muscle dimensions were collected. RAC supplementation tended to affect dressing percentage (P=0.15) and muscle firmness (P<0.15), and significantly affected lean maturity (P<0.05) and marbling score (P<0.05). With the exception of the LL and GRA (P<0.05), RAC had no effect on muscle dimensions. RAC did not influence the tenderness of vacuum-packaged, aged steaks as measured by Warner-Bratzler shear force. Muscle fiber size within the six muscles was unchanged (P>0.05) by RAC. Thus, RAC improves carcass parameters without a negative impact on tenderness.

Beta agonists in livestock feed: status, health concerns, and international trade.

Since the U.S. Food and Drug Administration approved ractopamine hydrochloride and zilpaterol hydrochloride in animal feeds, usage of those compounds has been a topic of worldwide debate. Ractopamine and zilpaterol are β-adrenergic agonists used as veterinary drugs to increase weight gain in certain animals raised for food. The Joint FAO/WHO Expert Committee on Food Additives (JECFA) established maximum residue limits for ractopamine, which were adopted by the Codex Alimentarius Commission (Codex). No maximum residue limits for zilpaterol have been adopted by JECFA, and new reports of animal mobility issues confront the use of this feed additive. However, many countries disagree with the Codex standards and are restricting or banning meat products containing β agonists. The bans by major importers of U.S. meat products have prompted some to advocate that the United States use the World Trade Organization dispute settlement body. This paper looks at the developments to provide a fuller accounting of what the issues may mean to U.S. firms selling meat products containing residues of β agonists.

Realimentation of nutrient restricted pregnant beef cows supports compensatory fetal muscle growth

Drought and other weather-related disasters impact the amount and quality of grains and forages available to beef cattle. The impact of nutrient restriction at specific gestational timeframes on fetal skeletal muscle growth was examined. Crossbred beef cows were fed to NRC recommendations (CCC) or restricted to 60% of said levels for the first 85 or 140 d of pregnancy followed by realimentation to recommended protein and energy levels (RCC and RRC, respectively). Fetal infraspinatus (INF) morphometrics and gene expression analyses were performed at d 85, 140, and 254 of gestation. Results demonstrate that fetal primary myofibers are larger (P < 0.05) after 85 d of maternal caloric restriction by comparison to controls. Realimentation of pregnant dams at d 85 causes an increase (P < 0.05) in RCC INF cross-sectional area (CSA) by comparison to RRC at d 140 but the fibers remain smaller (P < 0.05) than CCC muscle cells. Returning nutrient load to recommended levels at d 140 of pregnancy increases RRC CSA equivalent to CCC fibers at d 254 (343.4 ± 5.2 and 345.2 ± 5.3 μm(2), respectively). Fetal RRC and CCC muscle fibers are smaller (P < 0.05) than RCC fibers at d 254 suggesting the later experienced compensatory growth. Numbers of Paired box 7 (Pax7) immunopositive cells were fewer (P < 0.05) in the nutrient restricted fetuses at d 85 suggesting a loss of muscle progenitor cells. Moreover, mRNA content for the collagen crosslinking enzymes, lysyl oxidase and bone morphogenetic protein 1, were greater (P < 0.05) in the d 85 nutrient restricted fetal INF than CCC suggesting increased connective tissue cell numbers and/or activity. Because myogenesis is acutely regulated by the IGF, mRNA content of these growth factors and their receptors was examined. Fetal IGF1 mRNA content was lower in the d 85 nutrient restriction fetuses (P < 0.05) by comparison to CCC. Levels of INF IGF2 mRNA were greater (P < 0.05) in d 85 NR fetuses than CCC. Continued nutrient restriction through d 140 resulted in a reduction (P < 0.05) in IGF2 expression by comparison to CCC. No treatment effect on IGF1R or IGF2R mRNA content was noted. In summary, NR for 85 d causes an increase in primary INF fiber size that may be a result of increased IGF2 transcription and Pax7-immunopositive cell fusion. Realimentation of NR beef cows supports compensatory growth of the fetal musculature such that normal muscle fiber size and muscle progenitor numbers are achieved before birth.

Effect of long-term corn by-product feeding on beef quality, strip loin fatty acid profiles, and shelf life

The objective of this study was to evaluate the meat quality and shelf life of steaks from steers fed dried distillers grains with solubles (DDGS) or dried corn gluten feed (CGF) compared with soybean meal with corn (SBM) as a protein supplement from weaning to slaughter. Angus cross steers (n = 81; BW = 306 ± 26.1 kg) were randomly assigned to pens (n = 9) and fed a stocker diet of corn silage (75% of DM) with DDGS, CGF, or SBM and ground ear corn. After 84 d of stockering, 12 steers (BW = 397 ± 15.3 kg) were randomly selected from each treatment and finished using the same protein supplement at 25% of DM for 100 d. Carcass data were collected (24 h) and the longissimus lumborum was fabricated into steaks at 48 h postmortem. Steaks were assigned to proximate analysis, Warner-Bratzler shear force (7-, 14-, or 21-d aging), and retail display (1, 3, 6, or 9 d). Protein source did not affect carcass yield, quality, or longissimus lumborum composition (P > 0.05). After 7 d of aging, DDGS and CGF steaks were more tender (P < 0.01) than SBM, but were similar (P = 0.30) after 14 and 21 d of aging. Feeding corn by-products did not influence subjective overall color acceptance (P = 0.17) in this study, but acceptance declined over time (P < 0.01). Subjective redness was similar (P > 0.05) among diets except SBM steaks were more red (P < 0.01) than DDGS after 9 d. On d 3 and 6 of retail display, CGF steaks exhibited more discoloration (P < 0.04) than SBM or DDGS steaks. However, after 9 d DDGS steaks were more discolored (P < 0.01) than CGF or SBM. Objective L* was lighter for CGF (P < 0.04) over 9 d of display, and all treatments became darker (P < 0.01) as time increased. Redness (a*) declined (P < 0.01) over time with SBM steaks maintaining more color in the red spectrum than CGF and DDGS after 6 d of display. Protein source did not affect (P > 0.05) the rate of lipid oxidation. Total SFA concentrations were similar (P > 0.05) among treatments; however, total MUFA were less (P < 0.05) and total PUFA concentrations were greater (P < 0.05) in DDGS steaks compared with SBM or CGF steaks. These data show that DDGS or CGF can be fed as a protein supplement at 25% DM from weaning until slaughter while maintaining meat quality when compared with steers fed soybean meal as a protein supplement.

Effects of ovariectomization and ractopamine hydrochloride inclusion on heifer feedlot performance, meat yield, and tenderness of select muscles

Forty-eight British cross heifers were used to examine the effects of ovariectomization (OVX v. intact; INT) and ractopamine-HCl inclusion (0 or 0.41 mg/kg of BW day(-1); NORAC or RAC) for the final 31 days on performance, meat yield, and tenderness of select muscles. Ractopamine supplemented heifers had heavier BW (P≤0.05) and greater dressing percent than NORAC. Dressing percent was also greater (P<0.01) for INT v. OVX. LM area tended to be larger for RAC (P=0.07) and was larger for INT (P=0.05). Neither ractopamine inclusion nor sex class affected (P>0.08) organ weights or percent intramuscular fat. Ractopamine inclusion increased (P≤0.05) subprimal weight for the shoulder clod and bottom round. However, ractopamine inclusion and sex class had minimal effects on subprimal yields or slice shear force. Heifers receiving ractopamine had increased BW, DP, carcass weight and select subprimal weights without impacting meat quality. Ovariectomization did not influence the affects of ractopamine supplementation.

Use of corn gluten feed and dried distillers grains plus solubles as a replacement for soybean meal and corn for supplementation in a corn silage-based stocker system

Corn gluten feed and dried distillers grains plus solubles (DDGS) were evaluated as replacements for soybean meal and ground ear corn when supplemented with corn silage during 2 yr of a beef cattle stockering program. Experiment 1: In YR 1, 104 steers (initial BW = 305 ± 30 kg), and in YR 2, 56 steers and 38 heifers (initial BW = 301 ± 32 kg) were stratified by weight and assigned to 1 of 9 groups. Each group was randomly assigned to 1 of 3 corn silage-based (75% of DM) diets supplemented with: i) corn gluten feed (CGF), ii) DDGS, or iii) soybean meal and ground ear corn (CSBM) at 25% of DM. On d 0, 28, 56, and 84, BW and BCS were recorded. Additionally, ribeye area, 12th rib fat thickness, intramuscular fat, and rump fat thickness were assessed via ultrasound on 9 (YR1) and 4 (YR 2) steers per pen that were randomly assigned as observational units. Average daily gain was greater (P < 0.05) for steers fed DDGS and CSBM compared with CGF (1.08, 1.08, and 0.94 kg/d, respectively). Average DMI (P < 0.05) was less for DDGS compared with CSBM with CGF intermediate (18.1, 18.8, 20.2 g/kg BW, respectively), and the resulting G:F was greatest for DDGS (P = 0.01). Cost per kilogram of BW gain was least for DDGS (P > 0.05). Ultrasound data indicated no differences (P ≥ 0.13) in predicted carcass traits among treatments. Experiment 2: Diets from Exp. 1 were subjected to in vitro digestion for incubation times of 0, 2, 4, 8, 16, 24, 48, and 72 h to estimate DM degradation, gas production kinetics, and CP fractions. The potentially degradable DM fraction was greater (P = 0.01) for CSBM compared with CGF and DDG. Total gas production and rate of gas production was not different among treatments (P > 0.42). Rumen degradable protein was greatest for CSBM and least for DDG (P = 0.001). These data indicate that DDGS can be used to replace soybean meal and corn in silage-based stocker systems to decrease feed costs without compromising animal performance and CGF may decrease animal performance.

Effects of sodium citrate plus sodium diacetate and buffered vinegar on Escherichia coli O157:H7 and psychrotrophic bacteria in brine-injected beef.

The objective of this research was to examine the effects of sodium citrate plus sodium diacetate or buffered vinegar on Escherichia coli O157:H7 and psychrotrophic bacteria when incorporated in brine solutions for injected beef. Two experiments were conducted in which 30 top rounds and 30 top sirloins were injected (110%) to contain (i) 0.5% sodium chloride and 0.4% sodium tripolyphosphate as the control (CNT); (ii) CNT with a 1% solution of 80% sodium citrate plus 20% sodium diacetate (SC + D); or (iii) CNT with 2% buffered vinegar (VIN) in the final product. For the E. coli challenge, muscles were surface inoculated to target 6 log CFU/cm(2). After injection and 10 days of storage in a vacuum package (4°C), one half of each muscle was sampled raw and the other half was cooked to an internal temperature of 60°C with a 12-min hold. For raw samples, a significant reduction of 0.6 and 1.0 log CFU/g of E. coli O157:H7 was observed in both SC + D- and VIN-injected top rounds and sirloins, respectively. All cooked samples were E. coli O157:H7 negative. For psychrotrophic analysis, subprimals were injected and vacuum packaged for 10 days at 0 ± 1°C. After 10 days of storage, steaks were fabricated and placed in aerobic display (4 ± 1°C) for 1, 7, 14, and 21 days. Psychrotrophic organism growth was restricted in SC + D and VIN samples when compared with CNT on all days except day 1. Sodium citrate plus sodium diacetate or buffered vinegar may improve the safety and shelf life of multineedle brine-injected beef.

Effects of Days on Concentrate Feed and Postmortem Aging on Carcass and Palatability Characteristics of Selected Muscles from Cull Beef Cows1

Twenty-four beef cows were selected to examine the effects of concentrate feeding on performance and to examine the effects of concentrate feeding and postmortem aging (10 or 20 d) on the triceps brachii lateral and long heads, infraspinatus, longissimus lumborum, psoas major, gluteus medius, tensor fascia latae, rectus femoris, and vastus lateralis. Cows were randomly assigned to a concentrate diet for 0, 42, or 84 d. Carcass characteristics were measured and Warner-Bratzler shear force, sensory evaluation, and collagen analyses were performed on selected muscles. Cow BW, ADG, and BCS increased (P 0.05) sensory off-flavor detection. Concentrate feeding of cull cows for 84 d improved carcass characteristics and the tenderness of several muscles. These muscles may be aged for 20 d postmortem to achieve maximal tenderness without detrimental off-flavor production.