This study was conducted to determine threshold levels for Warner-Bratzler shear (WBS) force of the beef value cuts. USDA Choice and USDA Select M. biceps femoris, M. gluteus medius, M. infraspinatus, M. longissimus lumborum, M. rectus femoris, M. triceps brachii, and M. vastus lateralis steaks were evaluated for palatability characteristics and tenderness acceptability by a consumer panel (n = 205). Steaks also were evaluated by WBS analysis. The relationship between consumer tenderness-like ratings and WBS was investigated through regression analysis. Threshold WBS levels could not be determined due to the low correlation between consumer tenderness ratings and WBS. Within a muscle, percent tenderness acceptability was determined for each of the tenderness-like ratings. After analyzing the consumer ratings, tenderness acceptability, and WBS values, it was apparent that there may not be a single WBS threshold value suitable for all muscles. Research indicates that there may be muscle-specific WBS threshold levels; these values were not established from this research.

This study was conducted to determine threshold levels for Warner-Bratzler shear (WBS) force of the beef value cuts. USDA Choice and USDA Select M. biceps femoris, M. gluteus medius, M. infraspinatus, M. longissimus lumborum, M. rectus femoris, M. triceps brachii, and M. vastus lateralis steaks were evaluated for palatability characteristics and tenderness acceptability by a consumer panel (n = 205). Steaks also were evaluated by WBS analysis. The relationship between consumer tenderness-like ratings and WBS was investigated through regression analysis. Threshold WBS levels could not be determined due to the low correlation between consumer tenderness ratings and WBS. Within a muscle, percent tenderness acceptability was determined for each of the tenderness-like ratings. After analyzing the consumer ratings, tenderness acceptability, and WBS values, it was apparent that there may not be a single WBS threshold value suitable for all muscles. Research indicates that there may be muscle-specific WBS threshold levels; these values were not established from this research.

O presente trabalho teve como objetivo estimar a variabilidade genética existente entre touros e linhagens da raça Nelore, essas representadas pelos grandes genearcas, no que se refere à qualidade de carcaça e de carne. Os animais utilizados para coleta de dados de carcaça e carne pertenciam ao projeto de melhoramento genético e de avaliação para emissão de CEIP - Certificado Especial de Identificação e Produção, da Agro-Pecuária CFM-Ltda, e tinham idade entre 21 e 28 meses. Foram analisadas as características peso de carcaça quente (PCQ), área de olho de lombo (AOL), espessura de gordura subcutânea (EGS) e marmoreio (MAR). A qualidade de carne foi avaliada para os períodos de 7, 14 e 21 dias de maturação, quanto às perdas por exsudação (PE), perdas por cozimento (PC) e maciez (MAC). A avaliação da variabilidade genética entre linhagens foi efetuada com base em valores das diferenças esperadas na progênie (DEP) para as características PCQ, AOL, EGS, MAR e MAC aos 7, 14 e 21 dias de maturação. Foi encontrada variabilidade entre os touros e as linhagens estudadas sugerindo que um progresso genético pode ser conseguido pela seleção de animais para características de carcaça e carne dentro da raça Nelore. / The present study had as objective to estimate the genetic variability between steers and breed lines of Nellore, these represented by the greatest breeders, referred to carcass and beef quality. The animals used to collect the samples of carcass and beef belonged to the project of genetic improvement and evaluation to emission of CEIP-Special Certificate of Identification and Production of CFM Farm-Ltda. The animals had age between 21 and 28 months. Were analyzed the characteristics of hot carcass weight (PCQ), rib eye area (AOL), backfat thickness (EGS), marbling (MAR).The beef quality was evaluated for the periods of 7, 14 and 21 days of ageing, as reference the drip loss (PE), cooking loss (PC) and tenderness (MAC). The evaluation of the genetic variability between the breed lines was done based in the values of the expected progeny differences (DEP) of the characteristics of PCQ, AOL, EGS, MAR and MAC at days 7, 14 and 21 of ageing. There was found a variability between steers and the breed lines studied, suggesting that a genetic process may be possible by selecting the animals to carcass and beef characteristics in the Nellore breed.

O presente trabalho teve como objetivo estimar a variabilidade genética existente entre touros e linhagens da raça Nelore, essas representadas pelos grandes genearcas, no que se refere à qualidade de carcaça e de carne. Os animais utilizados para coleta de dados de carcaça e carne pertenciam ao projeto de melhoramento genético e de avaliação para emissão de CEIP - Certificado Especial de Identificação e Produção, da Agro-Pecuária CFM-Ltda, e tinham idade entre 21 e 28 meses. Foram analisadas as características peso de carcaça quente (PCQ), área de olho de lombo (AOL), espessura de gordura subcutânea (EGS) e marmoreio (MAR). A qualidade de carne foi avaliada para os períodos de 7, 14 e 21 dias de maturação, quanto às perdas por exsudação (PE), perdas por cozimento (PC) e maciez (MAC). A avaliação da variabilidade genética entre linhagens foi efetuada com base em valores das diferenças esperadas na progênie (DEP) para as características PCQ, AOL, EGS, MAR e MAC aos 7, 14 e 21 dias de maturação. Foi encontrada variabilidade entre os touros e as linhagens estudadas sugerindo que um progresso genético pode ser conseguido pela seleção de animais para características de carcaça e carne dentro da raça Nelore. / The present study had as objective to estimate the genetic variability between steers and breed lines of Nellore, these represented by the greatest breeders, referred to carcass and beef quality. The animals used to collect the samples of carcass and beef belonged to the project of genetic improvement and evaluation to emission of CEIP-Special Certificate of Identification and Production of CFM Farm-Ltda. The animals had age between 21 and 28 months. Were analyzed the characteristics of hot carcass weight (PCQ), rib eye area (AOL), backfat thickness (EGS), marbling (MAR).The beef quality was evaluated for the periods of 7, 14 and 21 days of ageing, as reference the drip loss (PE), cooking loss (PC) and tenderness (MAC). The evaluation of the genetic variability between the breed lines was done based in the values of the expected progeny differences (DEP) of the characteristics of PCQ, AOL, EGS, MAR and MAC at days 7, 14 and 21 of ageing. There was found a variability between steers and the breed lines studied, suggesting that a genetic process may be possible by selecting the animals to carcass and beef characteristics in the Nellore breed.

Beef fajitas have become a popular food item, but the supply of traditional muscles is insufficient to meet the growing demand. There is a need for alternative muscles that have similar eating characteristics to those currently marketed as beef fajitas. Four different treatments - papain (P), blade tenderization (B), papain + blade tenderization (P+B), and control (C) - were applied to sixty USDA Choice M. diaphragma pars costalis, M. transversus abdominis, M. obliquus abdominis internus, M. rhomboideus, M. trapezius, M. latissimus, and M. serratus ventralis. Muscles were cut into sections and frozen at -10ºC for evaluation by a trained sensory panel, consumer panel, and Warner-Bratzler shear force (WBSF) measurements. Trained panelists found that regardless of muscle, the addition of papain improved palatability scores. In general, treatment tended not to affect the palatability scores of the M. diaphragma pars costalis and M. serratus ventralis, which tended to receive higher scores in comparison to the other muscles. In general, the control and blade tenderized M. trapezius received the lowest trained and consumer panel palatability scores and had the highest WBSF values (P < 0.05). Regardless of muscle (except for M. diaphragma pars costalis and M. serratus ventralis), P and P+B treatments reduced WBSF values (P < 0.05). Consumers (n=81) gave the M. transversus abdominis, M. serratus ventralis, and M. latissimus similar (P > 0.05) tenderness ratings when the P treatment was applied. Consumers tended to prefer the flavor and tenderness of beef fajita strips that were treated with P and P+B and indicated a preference to purchase muscles with these treatments. Consumers were willing to purchase M. serratus ventralis treated with P+B and M. latissimus treated with P the majority of the time. Papain improved the eating quality of the muscles studied. The M. latissimus and M. serratus ventralis when treated with papain alone or in combination with blade tenderization, performed well enough to be considered as alternatives for traditional beef fajitas.

Biochemical changes in muscle postmortem have been associated with initial beef tenderness early postmortem, and with improvements in tenderness during postmortem storage, defined as meat aging. Differences in the initial contractile state of the sarcomere, the ionic environment of the sarcoplasm including pH, the activity of neutral proteolytic enzymes, and collagen content and solubility have been associated with beef tenderness. In Phase I, steaks from four genetic lines of steers and heifers were used to understand the biochemical differences between tough and tender steaks. The most tender (< 30 N Warner Bratzler shear force (WBS)) and toughest Longissimus steaks (< 30 N WBS) from Angus, Braford, Brangus, and Simbrah heifers and steers were used. For Phase II, samples were obtained from a subset of Santa Cruz yearling heifers selected based of genotypes for tenderness (tough and tender) using a commercial genetic marker. Within genotype for tenderness, each animal was randomly assigned to one of four growth enhancement treatments. The most tender (< 30 N WBS) and toughest Longissimus steaks (< 30 N WBS) were selected for use in this study. In Phase I, tough steaks after 3, 10, and 17d postmortem had higher (P < 0.0005) WBS values than tender steaks. Tender steaks came from carcass with slightly higher (P = 0.008) marbling score and (P = 0.01) Quality grade. Sarcomere length, total and soluble collagen, potassium concentration, and m and µcalpain did not differ (P > 0.05) between tough and tender steaks. Sodium concentration at 10 d was higher (P = 0.03) in tough steaks, but only account for 0.05% of the variation in WBS at 3d. Tender steaks had less (P = 0.04) intact desmin at 24h, but intact desmin was not correlated (P > 0.05) with WBS. In Phase II, tough steaks after 3, 10, and 17d postmortem had higher (P < 0.0001) WBS values than tender steaks. Tender steaks came from carcass with slightly higher (P < 0.03) marbling score and (P = 0.02) Quality grade. Tender teaks were slightly lighter (P = 0.02), with more red (P = 0.02) and yellow (P = 0.007) color, and had slightly lower (P = 0.02) pH, compared with tough steaks. Sarcomere length, total and soluble collagen, sodium and potassium concentration, and m and µcalpain did not differ (P > 0.05) between tough and tender steaks. Tender steaks had less (P < 0.0001) intact desmin at 17d postmortem than tough steaks. Intact desmin at 17d was responsible for 4%, 47%, and 30% of WBS variation after 3, 10, and 17d postmortem, respectively. The slight difference in marbling and quality grade did not account for a significant amount of variation in WBS. However, meat color and pH accounted for variation in shear WBS. Calcium flux may have influenced meat tenderness by activation of calpains and may have altered protein to protein interactions. Results suggested that marbling, µ calpain activity, and desmin degradation, and to a lesser extent pH and meat color contributed to meat tenderness.

The objectives of this study were to 1) evaluate marker associations for genomic regions of interest and significant ontology terms, 2) evaluate and compare 4 models for their efficacy in predicting genetic merit, 3) evaluate and compare the impact of using breed-of-origin genotypes in a Bayesian prediction model, and 4) evaluate the effects of data partitioning using family structure on predictions. Nellore-Angus F2, F3 and half-sibling calves were used with records for overall temperament at weaning (OTW; a subjective scoring system; n = 769) and Warner-Bratzler shear force (WBSF; a measure of tenderness; n = 389). After filtering, 34,913 markers were available for use. Bayesian methods employed were BayesB (using ̂) and BayesC (using π = 0 and ̂) in GenSel software, where, after estimation, π ̂ = 0.995 or 0.997 for WBSF or OTW, respectively. No regions associated with either trait were found using π ̂, but when π = 0 associated regions were identified (37 and 147 regions for OTW and WBSF, respectively). Comparison of genomic estimated breeding values from these 3 Bayesian models to an animal model showed that BayesC procedures (using ̂) had the highest accuracy for both traits, but that BayesB had the lowest indication of bias in either case. Using a subset of the population (n = 440), genotypes based on the breed in which the alleles originated from (i.e., breed-of-origin genotypes) were assigned to markers mapped to autosomes (n = 34,449), and incorporated into prediction analyses using BayesB (π ̂ = 0.997) with or without nucleotide-based genotypes. In either case, there was an increase in accuracy when breed-of-origin genotypes were incorporated into prediction analyses. Data partitions based on family structure resulted in 13 distinct training and validations groups. Relationship of individuals in the training with validation individuals did have an impact in some cases, but not all. There was poor prediction of genomic estimated breeding values for individuals in the validation population using BayesB methods, but performed better in all cases than breeding values generated using an animal model. Future studies incorporating breed-of-origin genotypes are of interest to determine if accuracy is improved in these groups.

Consumer evaluation, proximate data, Warner-Bratzler shear force (WBSF), fatty acid (FA) composition and volatile compounds were analyzed from the Longissimus thoracis (LT), Tricep brachii (TB) and Gluteus medius (GM) muscles finished on conventional feedlot (FL) and forages, including a perennial legume, birdsfoot trefoil (BFT; Lotus corniculatus), and a grass, meadow brome (Bromus riparius Rehmann, Grass). Representative retail forage (USDA Certified Organic Grass-fed, COGF) and conventional beef (USDA Top Choice, TC) were investigated (n = 6) for LT. Additionally, the effects of diet on Gluteus medius (GM) and Tricep brachii (TB) muscles were explored. Forage-finished beef scored lower (P < 0.05) in most of the affected sensory attributes except BFT which was similar to grain-finished beef. In forage-finished beef GM was more liked and in FL, TB was similar to GM except juiciness where it scored greater. The fat percent was found to be greatest (P < 0.05) in TC followed by BFT and FL. Nutritionally beneficial ratios of FAs were observed in forage-finished diet. Fatty acid concentrations were majorly affected (P ≤ 0.046) by diet. Few long-chain PUFAs were affected (P ≤ 0.015) by muscle type. No FA was a effected (P > 0.05) by the interaction of muscle and diet. 3-hydroxy-2-butanone, known to evoke a buttery sensation was affected (P = 0.011) by diet with greater (P < 0.05) concentration in GM across all diets. Strecker degradation products were affected (P ≤ 0.014) by muscle type being prominent in GM. Meanwhile, 2-ethyl-3,5-dimethyl-pyrazine was greatest (P < 0.05) in BFT. All pyrazine compounds were (P < 0.05) greater in GM. These results indicate that when consumer evaluated beef of finishing diets, FL beef was rated highly. Additionally, not all forages produce similar beef. There were similar ratings for BFT for all attributes except flavor having lower values compared with FL. The chemical composition of BFT beef was found to be intermediary and similar to both FL and Grass beef in many cases. Diet was found to interact with muscle for sensory and chemical measures. The GM and TB of FL did not differ (P < 0.05), while within forage treatments sensory response and chemical composition varied. These results indicate the meat quality of secondary beef muscles is more greatly impacted by forage diets.

Master of Science / Department of Animal Sciences and Industry / Michael E. Dikeman / The longissimus lumborum (LL) muscle from 117 steers and the LL, gluteus medius (GM), and triceps brachii (TB) from 132 heifers were obtained to evaluate the effects of feeding zilpaterol hydrochloride (Zilmax®; ZH) (7.56g/907kg on a 100% DM basis) on tenderness. Both genders were blocked by initial weight into 6 blocks of 4 pens. Pens were assigned to treatments of either 0, 20, 30 or 40 d on ZH, with a 3 d withdrawal. One steak was removed from each muscle for proximate analysis and three 2.54 cm thick steaks were vacuum aged for either 7, 14 or 21 d. Steaks were cooked to 70 ˚C and six 1.27 cm diameter cores were removed for Warner-Bratzler shear force (WBSF) determinations. All muscles from steers and heifers fed 30 and 40 d with ZH, had higher (P < 0.05) WBSF compared with controls. The WBSF of steer LL and heifer TB from the 20 d treatment was higher (P < 0.05) than controls. There were no treatment by aging interactions (P > 0.05) for WBSF of steaks from steer LL, heifer LL or heifer TB, but there was a treatment by aging interaction (P < 0.05) for WBSF of steaks from heifer GM. There were no differences (P > 0.05) in percent intramuscular fat for any muscle due to treatment. When using percent intramuscular fat as a covariate, differences in WBSF of steer LL and heifer TB were not altered, but there were slight differences in heifer LL and GM WBSF due to treatment when compared with not using percent fat as a covariate. Percentages of steaks with WBSF ≥ 5 kg increased as days on ZH increased and decreased as days of aging increased. Warner-Bratzler shear force values among the three aging times for steer LL control, 20 and 40 d treatments; all heifer LL treatments, and heifer TB 20 d were all positively correlated (P < 0.01) with each other. Feeding ZH for 20 d generally increased WBSF values, but means were still acceptable. Feeding ZH for 40 d was very detrimental to tenderness.

O objetivo do presente trabalho foi determinar a força de cisalhamento Warner-Bratzler do músculo Longissimus lumborum de animais zebuínos machos inteiros (Bos indicus) durante o período de maturação, nas faixas de pH final (pHf 48 horas post mortem) normal (pH entre 5,5 e 5,8) e anormal (pH entre 5,81 e 6,19) e temperaturas internas de cozimento. Concomitante com a avaliação de força de cisalhamento, foram avaliadas também a degradação da desmina e troponina T, o comprimento do sarcômero, o teor de colágeno total e solúvel, as temperaturas máximas de desnaturação das proteínas e a morfologia geral de agregação das fibras do músculo no cozimento. A degradação da desmina e troponina T foi maior no pHf normal, aparecendo produtos de degradação a partir do dia 7 nessa faixa de pHf. Não houve diferenças nos valores de comprimento do sarcômero, descartando-se assim, a contribuição desse parâmetro sobre a temperatura máxima de desnaturação (Tmáx) das proteínas, determinada utilizando calorímetro exploratório diferencial (DSC). Similarmente, não foram encontradas diferenças para os teores de colágeno total e solúvel, e os valores de colágeno total foram baixos, sugerindo que sua contribuição na segunda transição térmica e nos valores de força de cisalhamento foi mínima. As Tmáx1 e Tmáx2, correspondentes à desnaturação da meromiosina leve e pesada, respectivamente, foram menores no pHf normal, mas o efeito foi maior para a Tmáx2. A Tmáx3 da actina e titina aumentou até 14 dias post mortem na faixa de pHf normal, e posteriormente diminuiu significativamente após 21 dias, sugerindo possível degradação dessas proteínas nesse período de dias. Não foram encontradas diferenças nos valores de Tmáx no pHf anormal, em todos os dias post mortem, o que sugere a contribuição de um possível mecanismo de proteção que estabiliza as miofibrilas no aquecimento. Houve maior agregação das fibras do músculo no pHf normal nas temperaturas internas de cozimento de 65 e 80°C, provavelmente devido à maior desnaturação térmica das miofibrilas. Os valores de força de cisalhamento foram maiores com o aumento da temperatura interna de cozimento, devido ao aumento da desnaturação térmica das miofibrilas do músculo. Independente da temperatura interna de cozimento, os valores de força de cisalhamento foram altos em quase todos os dias post mortem para ambas as faixas de pHf, o que sugere a necessidade de utilizar métodos físicos ou químicos para aumentar a maciez do músculo Longissimus lumborum de animais zebuínos. / The aim of this work was to determine the Warner-Bratzler shear force of Longissimus lumborum muscle of Zebu bulls during ageing, at the normal (pH between 5.5 e 5.8) and abnormal (pH between 5.81 e 6.19) ultimate pH (pHu) groups (pH 48 hours post mortem) and internal temperatures of cooking. Concomitant with the Warner-Bratzler shear force evaluation, the degradation of desmin and troponin T, sarcomere length, total and soluble collagen content, maximum temperature of proteins denaturation, and aggregation of muscle fibers during cooking were also evaluated. The degradation of desmin and troponin T was higher in the normal pHu, appearing degradation products at day 7. There were no differences in the sarcomere length values, discarding the contribution of this parameter on the maximum temperature of proteins denaturation (Tmax) determined by differential scanning calorimeter (DSC). Similarly, no differences were found for total and soluble collagen contents, and the total collagen values were low, suggesting that its contribution in the second thermal transition and in the shear force values was minimal. The Tmax1 and Tmax2, corresponding to the denaturation of light and heavy meromyosin, respectively, were lower in the normal pHu group, but the effect was higher for Tmax2. The Tmax3 of actin and titin increased up to 14 days post mortem in the normal pHu group, which subsequently significantly decreased after 21 days, suggesting the possible degradation of these proteins in that period of time. No differences were found in the Tmax values for the abnormal pHu group at all days post mortem, suggesting the contribution of a possible protective mechanism that stabilizes the myofibrils during heating. There was higher aggregation of muscle fibers in the normal pHu, at internal temperatures of cooking of 65 and 80°C, probably due to a higher thermal denaturation of myofibrils. The shear force values were higher with the increase of the internal temperature of cooking due to the increased denaturation of the muscle myofibrils. Regardless of internal temperature of cooking, the shear force values were higher in almost all days post mortem for both pHu groups, which suggest the need of physical or chemical methods to increase the tenderness of Longissimus lumborum muscle of Zebu bulls.