Taxa de crescimento e fragmentação Miofibrilar diferenciadas em ratos submetidos a restrição alimentar e realimentação

Feed regimens alter muscle growth rate, hence they might impact the proteolytic system involved in tenderization during meat conditioning. The aim of this project was to verify the effects of feed restriction regimens on muscular and animal growth and their impact on postmortem myofibrillar fragmentation. The regimens were: 1) Feeding ad libitum for 11 d (Al/2); 2) Feed restriction (60% of Net Energy for maintenance - NEm) for 11 d (Rt/2); 3) Ad libitum for 22 d (Al); 4) Ad libitum for 4 d and feed restriction (60% NEm) for 18 d (Rt); 5) Ad libitum for 19 d and 3 d of fast (Ft); 6) Feed restriction (60% NEm) for 11 d and ad libitum until 22 d (Ral). The regimens Al/2 and Rt/2 had different intestine weights (19.3 &plusmn; 1.1 and 15.8 &plusmn; 1.9 g, respectively; P < 0.07). At 22 d, Al animals had higher (P < 0.07) intestine weight (21.8 &plusmn; 3.8). Moreover, Ral animals had heavier intestine (19.9 &plusmn; 1.5) as compared to Rt (16.6 &plusmn; 1.6) or Ft (12.8 &plusmn; 1.9). The intestine/live weight percentage ratio was lower (P < 0.05) for Ft (6.3%) as compared to Al (8.4%) and to Ral (9.2%), but it was similar to Rt (7.6%). Liver weight (g) in the Ral (9.5 &plusmn; 1.1) did not differ from Al (10.7 &plusmn; 2.5) or Rt (8.5 &plusmn; 1.1), although the two latter were different (P < 0.05). There was an effect of feed restriction over muscle protein degradation verified by Myofibrillar Fragmentation Index (MFI). The animals at Rt, Ft or Ral showed the lowest MFI 0d (42 &plusmn; 1.9; 40 &plusmn; 2.7; 40 &plusmn; 3.6; respectively) and MFI 5d (77 &plusmn; 2.7; 74 &plusmn; 3.0; 74 &plusmn; 2.9; respectively) as compared to Al, whose indexes were 54 &plusmn; 3.0 and 82 &plusmn; 3.3. Even though the MFI 5d were lower for the restricted animals, the rates of fragmentation postmortem were higher. Feed restriction altered myofibrillar protein degradation, reflected in lower extended fragmentation of the myofibrils.Regimes alimentares alteram a taxa de crescimento muscular, e podem impactar o sistema proteolítico envolvido no amaciamento da carne durante maturação. O objetivo do trabalho foi verificar a existência de reflexo do regime alimentar sobre crescimento animal e muscular, e o impacto na fragmentação miofibrilar pós-morte. Os regimes foram: 1) Consumo ad libitum por 11 d (Al/2); 2) Restrição alimentar (60% energia de mantença - NEm) por 11 d (Rt/2); 3) Ad libitum por 22 d (Al); 4) Ad libitum por 4 d e restrição alimentar (60% NEm) por 18 d (Rt); 5) Ad libitum por 19 d e 3 d de jejum (Ft); 6) Restrição alimentar (60% NEm) por 11 d e ad libitum até 22 d (Ral). Os regimes Al/2 e Rt/2 apresentaram diferenças no peso de intestino (19,3 &plusmn; 1,1 e 15,8 &plusmn; 1,9 g, respectivamente; P < 0,07). Nos 22 d, o regime Al resultou em intestinos mais pesados (P < 0,07; 21,8 &plusmn; 3,8). Além disso, os animais do regime Ral tiveram maiores pesos de intestino (19,9 &plusmn; 1,5) comparados com Rt (16,6 &plusmn; 1,6) ou Ft (12,8 &plusmn; 1,9). A relação intestino/peso vivo foi menor (P < 0,05) para Ft (6,3%) comparado com Al (8,4%) e com Ral (9,2%), mas foi similar ao Rt (7,6%). O peso do fígado (g) nos animais do regime Ral (9,5 &plusmn; 1,1) não diferiu do regime Al (10,7 &plusmn; 2,5) ou Rt (8,5 &plusmn; 1,1), sendo que os dois últimos foram diferentes (P < 0,05). Houve efeito da restrição alimentar sobre a degradação da proteína muscular verificada pelo Índice de Fragmentação miofibrilar (MFI). Os animais de Rt, Ft ou Ral mostraram os menores valores de MFI 0d (42 &plusmn; 1,9; 40 &plusmn; 2,7; 40 &plusmn; 3,6; respectivamente) e MFI 5d (77 &plusmn; 2,7; 74 &plusmn; 3,0; 74 &plusmn; 2,9; respectivamente) comparados com Al onde os índices foram 54 &plusmn; 3,0 e 82 &plusmn; 3,3, respectivamente. Embora os animais que experimentaram alguma restrição alimentar tenham apresentado menor MFI 5d, as sua taxas de fragmentação pós-morte foram maiores. Restrição alimentar alterou a degradação da proteína miofibrilar, refletida na menor extensão da fragmentação das miofibrilas

Histomorfologia intestinal de Pseudoplatystoma fasciatum alimentado com colostro bovino como fonte de proteína e peptídeos bioativos

Histological responses of the intestine are key for evaluating nutritional value of feed ingredients, since the organ is not only the chief site of feed digestion and nutrient absorption but also plays an important immunological function. Histomorphological alterations were evaluated in the intestine of juvenile striped catfish, Pseudoplatystoma fasciatum, fed diets containing 0 (control), 10 or 20% inclusion of lyophilized bovine colostrum (LBC), as source of protein or bioactive peptides, for either 30 or 60 days. Fish fed 20LBC presented at 60d a distinct pattern of macrophages and, some of them, higher number of vacuoles in rectum mucosa. The thickness of the muscle layer (TML) in fish fed diets with LBC was higher in the first portion of medium intestine than fish fed 0LBC. All fish presented significant increase of TML in the second portion of medium intestine along feeding period, but fish fed 20LBC had smaller values of TML than those of fish fed 0 and 10LBC which might be related to the higher intestinal coefficient found for this group. The TML of rectum was higher just for fish fed 10LBC. Dietary LBC altered morphometrical features of juvenile striped catfish intestine and possibly induced inflammatory reaction in the rectal mucosa, as a function of level of inclusion, feeding period and segment of intestine analyzed.Respostas histológicas do intestino são fundamentais para avaliar o valor nutritivo de ingredientes alimentares, uma vez que o órgão não é só o principal local de digestão e absorção dos nutrientes, mas também exerce uma importante função imunológica. Alterações histomorfológicas foram avaliadas no intestino de juvenis de cachara, Pseudoplatystoma fasciatum, alimentado com dietas contendo 0 (controle), 10 e 20% de inclusão de colostro bovino liofilizado (CBL) como fonte de proteína e peptídeos bioativos, aos 30 e 60 dias. Aos 60 dias, peixes alimentados com 20CBL apresentaram macrófagos de aspecto distinto e alguns, uma grande concentração de vacúolos na mucosa retal. A espessura da camada muscular (ECM) em peixes alimentados com CBL foi maior na primeira porção do intestino médio em relação àqueles alimentados com 0CBL. Ao longo do período experimental, todos os peixes mostraram aumento significativo na ECM na segunda porção do intestino médio, entretanto peixes do grupo 20CBL tiveram menores valores para a ECM do que os demais, o que pode estar relacionado com o maior coeficiente intestinal encontrado para este grupo. A ECM no reto foi maior apenas para os peixes alimentados com 10CBL. A inclusão de CBL na dieta do cachara alterou características morfométricas do intestino e, possivelmente, induziu uma reação inflamatória na mucosa retal em função do nível de inclusão, período de alimentação e porção do intestino analisada.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

Percepção pelos consumidores brasileiros da maciez da carne classificada pela força de cisalhamento e sabor

The knowledge of consumer perception of meat tenderness and taste is essential to forecast a Brazilian quality value-based beef market. This study aimed to verify perception of tender (WBSF ; 4.8 kg) strip loin steak or uncharacteristic (calcium-treated/Ca-IM) and normal (non-calcium/NO-Ca) meat taste by consumers according to gender, age, education and income levels. Steaks were previously classified by shear force measurements as tender or tough. Each consumer was served a paired sample of one tender and of one tough steak, which were either Ca-IM or NO-Ca treated before tenderness classification. Three hundred and eight consumers answered a nine-point intensity (tenderness) and hedonic (taste) scales evaluation questionnaire. Among consumers, 82.2% indicated beef as first choice meat products, 75.3% had beef at least four times a week; 39.3% considered taste as the most important meat attribute and 30.2% considered tenderness; 75.8% were males; 73.6% were 21 to 55 years old; 56.7% had college education; 76.6% had monthly income higher than US $435,00. Tender steaks were scored highest (P ; 4.8 kg), ou ainda com sabor não característico (imersão em Ca/ Ca-IM) ou normal (sem cálcio/ NO-Ca) de acordo com sexo, faixa etária, e nível de escolaridade formal e renda dos consumidores. Os bifes foram pareados em amostras macia/dura e Ca-IM/NO-Ca, e servidos a 308 consumidores que responderam a um questionário apresentando escalas de intensidade (maciez) e hedônica (sabor) de nove pontos. O perfil dos consumidores mostrava que: 82,2$ 1.000,00. De maneira geral, os bifes macios obtiveram notas mais altas (P < 0,01), independente de sexo, faixa etária e nível de renda. Entretanto, os idosos deram notas mais altas que os consumidores de meia idade em avaliações dos bifes macios (P < 0,05). No nível baixo de escolaridade não houve diferença nas notas para bifes macios e duros. Quanto mais alto o nível de renda, menor foram as notas dadas nas avaliações dos bifes macios ou duros (P = 0,10). Diferenças no sabor foram notadas por ambos os sexos, e por todos os níveis de escolaridade e renda. O sexo masculino conferiu notas mais altas (desgostou menos) quando consumia bifes Ca-IM. Consumidores do menor nível de escolaridade atribuiram notas maiores para sabor (gostaram mais) em bifes com sabor normal. Os idosos não diferenciaram sabor entre os bifes Ca-IM e NO-Ca. Estas observações são as primeiras indicações objetivas de que os consumidores brasileiros são capazes de perceber diferenças entre bifes macios e duros ou com sabor amargo e normal. Todavia, a palatabilidade é avaliada de forma diferenciada dependendo do sexo, faixa etária, e níveis de escolaridade e renda

Alterações nas proteínas sarcoplasmáticas e miofibrilares em frangos de corte causadas por estresse térmico agudo

O estresse térmico agudo (ET) causa alterações na estrutura das miofibrilas, afetando propriedades funcionais da carne, principalmente a capacidade de retenção de água. Identificaram-se mudanças na proteólise e migração entre as frações miofibrilar e sarcoplasmática, decorrentes do ET pré-abate, através do índice de fragmentação miofibrilar (MFI), SDS-PAGE para troponina (SDS), imunodetecção de vinculina (IV) e força de cisalhamento (FC). Seiscentos frangos (Gallus gallus) foram abatidos em três dias diferentes (DA). Em cada DA os animais foram colocados em caixas de transporte (10 aves/caixa) e submetidos a ET (35ºC, 75 - 85% UR)por 2 horas. Simultaneamente, o outro grupo de animais (NET) foi mantido em caixas em condição termoneutra (22ºC, 83 ± 6,6% UR) pelo mesmo período de tempo. Após o abate o músculo do peito foi coletado e mantido refrigerado, até a retirada de todas as amostras (0, 1, 2, 6 e 24 horas pós-abate). O valor de luminosidade (L* ; 51, alto), foi o parâmetro utilizado na amostragem para SDS e IV. A cinética do MFI demonstrou que a taxa de fragmentação foi superior nos animais NET, indicando que o estresse térmico pode prejudicar o processo de proteólise. Entretanto, a extensão da fragmentação não variou, bem como os valores de FC. No SDS ocorreram padrões diferenciados de fragmentação entre aves ET e NET. Modificações na fração sarcoplasmática foram observadas em amostras com L*, independentemente da condição ambiental.Acute heat stress (AHS) modifies the structure of myofibrils affecting functional properties of meat, mainly the water holding capacity. This experiment aimed to identify changes in proteolysis and migration between the myofibrillar and sarcoplasmatic fractions due to pre-slaughter AHS. Myofibrillar fragmentation index (MFI), SDS-PAGE, western blot of vinculin (WB) and shear force (SF) were determined. Six hundred broilers (Gallus gallus) were slaughtered in three different days (ST). In each ST, groups of ten animals were placed in transport crates and submitted to AHS (35ºC, 75 - 85% RH) for 2 hours. Simultaneously, the non-stressed broilers (NS) were kept in thermoneutral environment (22ºC, 83 ± 6.6% RH) within the crates in the same density. After slaughter, the breast muscles were kept refrigerated until the withdrawal of all samples (0, 1, 2, 6 and 24 hours after slaughter). Sampling within AHS and NS birds was collected according to lightness value (normal L* ; 51), except for determination of MFI and SF. The lightness was used later to perform SDS-PAGE and WB analyses. MFI kinetics showed that the fragmentation rate was superior in animals NS, indicating that AHS can harm proteolysis and rate of myofibrillar fragmentation. However, the extent of fragmentation did not change, as well as SF values. SDS-PAGE for Troponin fragments indicated a differentiated pattern between AHS and NS. The WB did not show alterations in vinculin fragmentation. Modifications in sarcoplasmatic fraction are observed in meat with high L*values, independent of environmental condition

The calpain system and postmortem tenderization in ovine meat from callipyge and normal phenotypes

In an attempt to further our understanding of the relationship between the calpain system and postmortem tenderization, three muscles [biceps femoris (BF), infraspinatus (IS), and longissimus (LD)] from normal (N = 6) and callipyge (N = 6) sheep were studied. Callipyge is a genetic phenomenon where carriers of the callipyge gene present a hypertrophy of pelvic and torso muscles, such that BF and LD are affected while IS is not. It has been observed characteristically that calpastatin and m-calpain activities are increased in muscles of animals affected by the callipyge phenotype. Soluble calpain and calpastatin, and myofibril-bound μ-calpain activities, and myofibrillar fragmentation index (MFI) were determined at death, 1d, 3d and 10d postmortem. Sarcomere length was determined at 1d and 10d postmortem. Shear force of the longissimus muscle was determined at 1d, 3d and 10d postmortem. Western blots for calpastatin, μ-calpain, desmin, nebulin, titin, troponin-T and α-actinin were performed to follow the degradation pattern of those proteins. The calpastatin and m-calpain activities were more than two-fold greater in BF and LD muscles from callipyge than in the same muscles from normal animals. Calpastatin activities in infraspinatus muscle from normal animals were higher than in the other two muscles of this phenotype. Soluble μ-calpain activities were higher at death for normal phenotype in BF and IS muscles and it decreased rapidly during postmortem storage. However, the rate of this decrease in that activity was faster in normal than in callipyge phenotype. Myofibrils contained calcium dependent protease activity and this activity was inhibited by cysteine proteases inhibitors and by calpastatin to some degree. There was no difference in the myofibril-calcium dependent protease activity between phenotypes at any time postmortem, presenting lower activity at death. The magnitude of protein degradation and tenderization were assessed by MFI and shear force, respectively. Neither the MFI nor shear force changed appreciably during storage of the callipyge affected muscles. Calpastatin level seems to determine the rate of postmortem tenderization

Pork loin two-toning and drip loss in relation to steak cross-section anatomical position, plasma and exudate glucose

Perception of color and its relationship to water holding capacity are important for defining the yield and quality of the pork production process. The aim of this study was to identify the relationship among color measurements taken at various anatomical positions in the cross-sectional surface of pork loin steak, and measurements of fluid exudation and its glucose concentration, as well as the impact on these attributes due to plasma glucose at slaughter. Two assays were conducted sequentially: i) investigation of the surface color parameters at different anatomical positions in the pork loin cross-section and their relationship to general exudation; and ii) the effect of plasma glucose levels on surface color variables, drip loss and glucose exudate concentration in three anatomical regions in the steak. The L* value of the ventro-lateral region, in the first assay, had the highest correlation with average steak drip loss at all anatomical points, exudation increasing proportionally between 48 and 72 h. The hue angle was also positively correlated with drip loss and lightness. The drip loss was greater when the animals had high plasma glucose, especially in the intermediate and lateral regions of the steak surface. The intermediate region presented greater lightness and lower redness. The plasma and glucose exudate concentrations, potential indicators of the muscle glycolytic metabolism, were related to color and drip loss. These variables can be influenced by the anatomical region inside the muscle, impacting the ability to retain water, two-toning occurrence and overall pork loin quality

Reatividade em teste comportamental e impacto nos indicadores de estresse de suínos

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