Effect of residual feed intake on hypothalamic gene expression and meat quality in Angus-sired cattle grown during the hot season.

The relationship between heat stress, meat quality, and residual feed intake (RFI) is unknown in growing steers. To address this issue, high RFI (HRFI) and low RFI (LRFI) individuals were compared by assessing RFI in 48 Angus-sired steers during a 70-d feeding trial conducted during July through September to identify steers with calculated RFI at least 2 SD apart. The association of RFI with indices of meat quality and expression of genes within hypothalamic and adipose tissue was then determined in LRFI and HRFI steers. While on test, feed intake was recorded daily with BW and hip heights recorded every 14 d. Ultrasound measurements of rib eye area (REA) and backfat (BF) were recorded initially and before harvest. Carcass and growth data were analyzed using a mixed model with RFI level (LRFI and HRFI) as the independent variable. The least square means for RFI were -1.2 and 0.99 kg DMI/d, respectively, for the LRFI and HRFI cohorts (P < 0.0001). Dry matter intake was higher for the HRFI individuals versus the LRFI steers (P < 0.0001) while on-test gain was not different (P < 0.95). Marbling score was greater in LRFI than HRFI steers (P < 0.05). However, there were no differences in REA (P < 0.53), BF (P < 0.65), yield grade (P < 0.24), or objective Hunter color measures between LRFI and HRFI steers indicating there was no consistent relationship between RFI and indices of meat quality. Hypothalamic neuropeptide Y (NPY), agouti related protein (AGRP), relaxin-3 (RLN3), melanocortin 3 receptor, and relaxin/insulin-like family peptide receptor 1 (RXFP1) mRNA were expressed 280, 185, 202, 183, and 163% greater, respectively (P < 0.01), while proopiomelanocortin (POMC) mRNA was expressed 42% lower in LRFI than HRFI animals (P < 0.05). Hypothalamic GnRH mRNA expression was 67% lower while gonadotropin inhibiting hormone (GnIH) mRNA was 209% higher in LRFI than HRFI animals (P < 0.01). Pituitary expression of FSHß and LHß correlated to hypothalamic GnRH levels (P < 0.05) indicating changes in gene expression within the hypothalamus had functional consequences. Leptin mRNA expression levels were not different between adipose tissue of LRFI or HRFI steers (P < 0.84). These data indicate that animals with superior RFI evaluated during warm conditions have higher expression of orexigenic neuropeptide genes independent of the expression of adipose-derived leptin. Furthermore, the gonadotropin axis may also influence feed efficiency under these conditions.

Residual feed intake studies in Angus-sired cattle reveal a potential role for hypothalamic gene expression in regulating feed efficiency.

Mechanisms underlying variation in residual feed intake (RFI), a heritable feed efficiency measure, are poorly understood while the relationship between RFI and meat quality is uncertain. To address these issues, 2 divergent cohorts consisting of High (HRFI) and Low (LRFI) RFI individuals were created by assessing RFI in 48 Angus-sired steers during a 70 d feeding trial to identify steers with divergent RFI. The association of RFI with indices of meat quality and expression of genes within hypothalamic and adipose tissue was then determined in LRFI and HRFI steers. While on test, feed intake was recorded daily with BW and hip heights recorded at 14 d intervals. Ultrasound measurements of rib eye area (REA) and backfat (BF) were recorded initially and before harvest. Carcass and growth data were analyzed using a mixed model with RFI level (LRFI, HRFI) as the independent variable. The least-square means (lsmeans) for RFI were -1.25 and 1.51 for the LRFI and HRFI cohorts (P < .0001). Dry matter intake was higher for the HRFI individuals versus the LRFI steers (P < .0001) while on test BW gain was not different between the 2 groups (P < 0.73). There were no differences detected in marbling score (P < 0.93), BF (P < 0.61), REA (P < 0.15), yield grade (P < 0.85) or objective Hunter color measures between LRFI and HRFI steers indicating that there was no relationship between RFI and meat quality. Neuropeptide-Y (NPY), relaxin-3 (RLN3), melanocortin 4 receptor (MC4R), and GnRH mRNA expression was 64%, 59%, 58%, 86% lower (P < 0.05), respectively, while gonadotropin inhibiting hormone (GnIH) and pro-opiomelanocortin (POMC) mRNA expression was 198% and 350% higher (P < 0.01) in the arcuate nucleus of LRFI steers. Expression of agouti-related protein (AGRP), relaxin/insulin-like family peptide receptor 1 (RXFP1), and melanocortin 3 receptor mRNA was similar between LRFI and HRFI animals. Pituitary expression of FSHß (P < 0.03) and LHß (P < 0.01) was correlated to hypothalamic GnRH levels suggesting that changes in gene expression within the arcuate nucleus had functional consequences. Leptin mRNA expression was 245% higher in the adipose tissue of LRFI steers consistent with lower levels of NPY and higher expression of POMC in their hypothalami. These data support the hypothesis that differences in hypothalamic neuropeptide gene expression underlie variation in feed efficiency in steers while the gonadotropin axis may also influence feed efficiency.

Salmonella and Campylobacter reduction and quality characteristics of poultry carcasses treated with various antimicrobials in a post-chill immersion tank.

Innovations in poultry processing include implementation of antimicrobials in post-chill decontamination tanks. In this study, a total of 160 broiler carcasses were analyzed to evaluate the efficacy of five post-chill water treatments consisting of 0.004% (40ppm) total chlorine, 0.04% (400ppm) or 0.1% (1000ppm) peracetic acid (PAA), and 0.1% (1000ppm) or 0.5% (5000ppm) lysozyme against Salmonella and Campylobacter spp. In addition, sensory analysis was performed to evaluate any associated effects of the antimicrobials on quality attributes of chicken breast meat. Treatment with 0.04% and 0.1% PAA was most effective (P≤0.05) in reducing populations of Salmonella and Campylobacter as compared to the chlorine treatment at 0.004% and lysozyme treatments at 0.1% and 0.5%, as well as the water treatment and the positive control. Treatment with the various antimicrobials was not found to have negative (P≤0.05) impacts on sensory attributes. Results from this study suggest that utilizing PAA as an antimicrobial in a post-chill immersion tank is an effective application for reducing Salmonella and Campylobacter on carcasses while maintaining product quality.

Correlation analysis of Shiga toxin-producing Escherichia coli shedding and faecal bacterial composition in beef cattle.

AIMS: The objectives of this study were to investigate the correlations between Shiga toxin-producing Escherichia coli (STEC) shedding and faecal microflora in beef cattle and to identify functional species that might be used for STEC control. METHODS AND RESULTS: Faecal samples were collected from 110 calves and 92 dams. The number and prevalence of STEC were determined using CHROMagar™ STEC; denaturing gradient gel electrophoresis (DGGE) was employed to analyse faecal bacterial composition. Six-month-old calves had the highest STEC shedding levels (3.03 ± 1.41 Log CFU g(-1)) and prevalence (95.5%). Both the number and prevalence decreased significantly as the calf age increased (P < 0.05). The DGGE analysis showed that faecal bacterial diversity increased, while cattle ages increased and STEC shedding levels decreased. Significant correlations between STEC shedding, cattle age and bacterial compositions were observed by redundancy analysis (P < 0.05). T-value biplots and sequencing results indicated that butyrate-producing bacteria (BPB) negatively correlated with STEC shedding. CONCLUSIONS: Higher STEC shedding levels and prevalence were associated with younger cattle age, lower faecal bacterial diversity and lower BPB levels. SIGNIFICANCE AND IMPACT OF THE STUDY: Butyrate-producing bacteria in GI tract might serve as an option for the future development of STEC shedding control strategy.

Grain feeding coordinately alters expression patterns of transcription factor and metabolic genes in subcutaneous adipose tissue of crossbred heifers.

The ability to improve meat quality and production efficiency in cattle is limited by an inability to enhance marbling and simultaneously limit undesirable adipose tissue accretion. The objective of this study was to examine expression of regulatory genes in subcutaneous (SCF) adipose tissue of heifers in response to increasing days on feed (DOF) and finishing strategy. Crossbred heifers (n = 24) were allotted as follows: Group 1 = 0 d, Group 2 = 99 d on winter annual ryegrass (grass; Lolium multiflorum Lam.), Group 3 = 218 g on grass, Group 4 = 99 d on grass followed by 119 d on grain. Adipose tissue samples were collected at time of harvest and frozen. Carcass characteristics were measured 24 h postharvest. As expected, HCW (P < 0.0001), ribeye area (REA; P < 0.0002), backfat (BF; P < 0.0001), KPH (P < 0.0001), and marbling score (P < 0.0009) increased with DOF though frame score was not different (P < 0.95). Average daily gain decreased with DOF (P < 0.0001). Yield grade increased (P < 0.0014) but cook loss percentage decreased (P < 0.001) with DOF without changes in 24-h pH (P < 0.31). Interestingly, Warner-Bratzler shear force (WBS) was decreased with DOF (P < 0.0089). Meanwhile, BF (P < 0.01) and KPH (P < 0.05) were greater, whereas marbling values trended greater in grain versus grass-finished heifers. Neither ADG (P < 0.89), HCW (P < 0.26), frame score (P < 0.85), nor REA (P < 0.38) were different between these groups. Grain finishing increased yield grade (P < 0.001) but did not affect 24-h pH (P < 0.88), cook loss percentage (P < 0.98), or WBS (P < 0.44) compared with grass-finished heifers. The expression of PPARγ, bone morphogenic protein 2 (BMP2), and SMAD family member 1 (SMAD1) mRNA was upregulated in response to DOF and grain finishing, whereas sterol regulatory element binding protein 1c (SREBP-1c), sonic hedgehog (SHH), chicken ovalbumin protein transcription factor 1 (COUP-TF1), chicken ovalbumin protein transcription factor 2 (COUP-TF2), and preadipocyte factor-1 (PREF-1) mRNA was decreased in response to DOF and grain finishing. These changes were associated with increased expression of lipoprotein lipase (LPL), stearoyl-coenzyme A desaturase (SCD), and fatty acid synthase (FAS) mRNA. In summary, increasing DOF was associated with improved meat quality whereas gene expression studies suggest several novel genes are associated with subcutaneous adipose tissue development in growing and finishing cattle.

Effect of liquid smoke as an ingredient in frankfurters on Listeria monocytogenes and quality attributes.

Market trends indicate an increased interest in natural antimicrobials to augment safety of ready-to-eat meat and poultry products against Listeria monocytogenes. Liquid smoke, an all-natural condensate of smoke components, applied as a postprocess treatment on product surface has the potential to exhibit antilisterial properties. Studies on its antimicrobial efficacy and quality attributes as an ingredient are not sufficient. A study was designed to validate the antimicrobial effect of liquid smoke as an ingredient against L. monocytogenes and its effect on the shelf life and quality of frankfurters. Chicken/pork frankfurters were incorporated with 0, 2.5, 5, and 10% liquid smoke (Zesti Smoke, Kerry Ingredients and Flavors, TN). Cooked casing-stripped frankfurters (4 per package) were placed in vacuum-pack bags, spray inoculated with either high (8 log(10) cfu/ mL) or low (4 log(10) cfu/ mL) levels of L. monocytogenes serotype 4b, vacuum packaged, and stored at 4°C for up to 12 wk. Samples were taken every week for 12 wk to estimate growth of L. monocytogenes and spoilage microflora (aerobic plate counts, yeast and molds, lactic acid bacteria, and total coliforms) and properties of sensory scores and texture profile analysis. The experiment was conducted as 3 separate trials and data was analyzed to find significant differences at P < 0.05. Formulation of frankfurters with smoke extract at 2.5, 5, and 10% reduced (P < 0.05) populations of L. monocytogenes as compared with the controls throughout the storage period irrespective of the inoculation levels. Furthermore, incorporation of smoke extract did not affect (P > 0.05) the texture, juiciness, flavor, and overall scores as well as hardness and chewiness of the frankfurters. Zesti Smoke can be effectively incorporated as an all-natural antimicrobial in the manufacture of frankfurters without negatively affecting quality attributes.

Marination with natural curing ingredients, storage time, and serving temperature effects on the sensory characteristics of forage-finished or commercially-sourced beef roasts.

Beef inside round roasts (n=144) were cut from rounds obtained from both forage-finished cattle (n=72) and commercially-sourced beef (n=72). Roasts were portioned to weigh 0.45-0.68kg each. Each roast was then randomly assigned one of the following treatments: control, injected-no cure, or injected-cured. Additionally, roasts were assigned a serving temperature (hot or cold) and storage treatments (0d or 28d post cooking). Roasts from forage-fed beef had a more red interior color and higher shear values, and also retained more brine than commercially-sourced beef (P<0.05). Curing roasts improved TBARS values in roasts served hot and significantly reduced sensory warmed-over and grassy flavors (P<0.05). Marinating forage-finished beef roasts significantly improves tenderness and flavor characteristics.

Inactivation at various temperatures of bovine viral diarrhea virus in beef derived from persistently infected cattle.

Bovine viral diarrhea virus (BVDV) is a pestivirus that is enzootic in most cattle populations throughout the world. This virus is present throughout the body of persistently infected (PI) cattle. Previous research has not assessed the cooking temperature at which BVDV in meat from PI cattle can be inactivated. Therefore, muscle tissue from 6 PI cattle was harvested, refrigerated, frozen, and heated to various internal temperatures. The concentration of virus present was determined by virus isolation. Average cell culture infective doses (50% endpoint; CCID(50)) of BVDV per gram of frozen, uncooked meat from PI cattle were 10(5.85) CCID(50)/g of whole cuts and 10(6.02) CCID(50)/g of ground meat. The virus in whole and ground meat was consistently inactivated when cooked to temperatures greater than or equal to 75°C. A second objective of this research was to thoroughly reassess if Vero cells were permissive to BVDV infection in our laboratory to provide further indication of whether primates, including humans, might be susceptible to BVDV. Vero cells were not permissive to infection with any of 43 different strains of BVDV that readily replicated in Madin Darby bovine kidney cells. In conclusion, this bovine pathogen, which is not considered to be a human pathogen, can be inactivated by cooking ground or whole cuts of meat to 75°C or higher. Care should be taken to ensure that susceptible hosts such as pigs are not fed improperly cooked meat, meat by-products, or waste food originating from PI cattle.

Texture and acceptability of goat meat frankfurters processed with 3 different sources of fat.

The objective of this research was to evaluate the texture and consumer acceptability of goat meat frankfurter formulations with no added fat (NAF), beef fat (BF), or canola oil (CO). Consumer sensory evaluation, fat, and moisture and texture profile analyses were performed on goat meat frankfurters produced with the fat sources BF, CO, and NAF. For sensory evaluations, NAF was less tender (P = 0.007; 4.90 vs. 4.11 and 4.35 for BF and CO, respectively) and the flavor was liked less (P = 0.004; 4.59 vs. 3.83 and 4.30 for BF and CO, respectively); BF was scored as the juiciest (P = 0.003; 3.86 vs. 4.49 and 4.58 for CO and NAF, respectively); and CO had the least amount of flavor (P = 0.029; 3.65 vs. 3.12 and 3.10 for BF and NAF, respectively). Moisture was least (P < 0.001) in CO (46.59%), followed by BF (48.57%) and NAF (55.80%). The amount of fat was not different (P = 0.761) in BF (24.36%) or CO (24.43%) but was less (P < 0.001) in NAF (9.06%), as expected. The NAF had the most protein (P < 0.001; 34.14%), followed by CO (27.98%) and BF (26.07%). For texture profile analyses, NAF had the least hardness value (P = 0.008; 3.92 vs. 4.48 and 4.40 for BF and CO, respectively) and least chewiness value (P = 0.026; 2.89 vs. 3.39 and 3.29 for BF and CO, respectively). Beef fat and CO were not different for hardness (P = 0.596) or chewiness (P = 0.530). No differences were observed in springiness (P = 0.954) or resilience (P = 0.561). The sensory panelists tended to prefer BF for overall acceptability. Results from these data revealed that value-added goat meat products received acceptable sensory scores; therefore, continued research and development will greatly expand the knowledge of goat meat and increase the acceptance of value-added products.

Effects of dry aging of bone-in and boneless strip loins using two aging processes for two aging times.

This experiment investigated the combined effects of two dry-aging methods (unpackaged and in a bag), two loin-cut styles (bone-in shell loins and boneless strip loins), and two aging times (21 and 28days) on the physical, chemical, sensory, and microbial properties of dry-aged beef. Sections from shell and strip loin were assigned randomly to be aged unpackaged or aged packaged in a bag with high moisture permeability. Weight losses increased with aging time. Shell loins lost more (P<0.05) weight during aging compared with strip loins; dry aging in a bag had less (P<0.05) weight loss than unpackaged aging. There were no differences (P>0.05) in any of the sensory traits between shell and strip loins or dry aging using a traditional method or in a bag. Dry aging in a bag creates positive effects on yields, no negative effects on product quality, and adds flexibility and control of the aging environment.

Enhanced efficiency of a capillary-based biosensor over an optical fiber biosensor for detecting calpastatin.

A capillary-based optical biosensor has been developed to detect calpastatin, an indicator of meat tenderness. Longissimus muscle samples (n=11) were extracted from beef carcasses at 0 and 48h post-mortem. These samples were assayed for calpastatin by traditional laboratory methods and with a newly developed capillary tube biosensor as well as for Warner-Bratzler shear force (WBSF) and crude protein and the responses were compared. Additionally, the response from the capillary-based biosensor was compared to a previously developed optical fiber biosensor. When the 0 and 48h sampling periods were combined, the capillary tube biosensor was moderately accurate in predicting calpastatin activity (R(2)=0.6058). There was less variation in the 0h capillary tube biosensor compared to the 0h pre-column (P=0.006) and post-column optical fiber biosensors (P=0.047), therefore the capillary tube biosensor is a more precise system of measurement. This research further advances the development of a calpastatin biosensor and makes online assessment one step closer to reality.

Correlation between a novel calpastatin biosensor and traditional calpastatin assay techniques.

An optical fiber biosensor to detect calpastatin has been investigated as a preliminary step in developing tenderness detection instrumentation. Longissimus dorsi samples were taken from beef carcasses (n=21) at 0, 24, 36 and 48h postmortem. Muscle homogenates were assayed for calpastatin activity using traditional methods and an optical fiber biosensor. Warner-Bratzler shear force was also performed on a steak from each carcass at 14d postmortem. Results demonstrated that the measurements with highest correlation between traditional calpastatin assays and optical biosensor readings were taken at 48h postmortem (r=0.597, P< or =0.01), suggesting that this is the best time for use of this biosensor in an on-line grading system. This research further advances the development of a calpastatin biosensor and would be useful in laboratory determination of the presence of biologically active calpastatin concentrations.

The effects of quality grade, aging, and location within muscle on Warner-Bratzler shear force in beef muscles of locomotion.

Aging patterns of nine muscles from the chuck and round from two quality classifications of beef: USDA Select and upper 2/3 of USDA Choice grade were determined. The following muscles were evaluated: infraspinatus, triceps brachii - lateral head, triceps brachii - long head, serratus ventralis, complexus, splenius, rhomboideus, vastus lateralis and rectus femoris. Muscles were divided into four portions, progressing from anterior to posterior or dorsal to ventral orientation to the carcass depending on muscle fiber orientation. One steak was removed from each portion and aged for 7, 14, 21, or 28 d postmortem, then Warner-Bratzler shear force (WBSF) analysis was conducted. Consistent aging recommendations can be given for all muscles studied, as there was no aging by muscle interaction. An aging by USDA grade interaction was noted (P<0.05). The upper 2/3 of USDA Choice need not be aged beyond 7 d. USDA Select should be aged at least 14 d. Steak location within muscle had an effect (P<0.05) on WBSF values in four muscles. These data indicate that fabrication and merchandizing decisions should be made on an individual muscle basis.