"December, 2004." / Bibliography: leaves 229-251. / xvi, 265 leaves : ill. (some col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, School of Agriculture and Wine, Disciplines of Animal Science and Biometrics SA, 2005?

A pre rigor cut was made through the 12th thoracic vertebrae of one side of a beef carcass, while the other side, processed conventionally, served as the control. The effect of this cut upon yield grade, sensory attributes and tenderness of Longissimus steaks was determined. The treatment caused no differences (P>0.05) in yield grade or in CIE L* a* b* values and oxymyoglobin, reduced myoglobin and metmyoglobin values measured on samples at the treatment site. Sensory panel ratings of visual attributes of color and overall appearance were less desirable (P<0.05) for the treated sides, while for visible texture ratings, there was no significant difference. Purge, cooking loss, percentage moisture, fat and protein, and total collagen were not affected by the treatment (P>0.05). Sarcomere length, and sensory panel ratings of myofibrillar tenderness, connective tissue, and overall tenderness were significantly more desirable for the treated sides. There was no significant difference in fragmentation index or peak force values between treatments, although these values tended to be lower for the treated sides than for the control sides. / Master of Science

Thesis (MScAgric) -- Stellenbosch University, 2009. / ENGLISH ABSTRACT: The two main determinants of post-slaughter processing outcomes are rates of pH and temperature decline. Muscle pH and temperature interact continuously during rigor development to affect both the muscle contracture and proteolytic enzyme activity. The pH, however, can be manipulated independently of temperature by electrical inputs applied to the carcass. Electrical inputs that should be considered range from electrical stunning to the various forms of electrical immobilisation (EI) and stimulation (ES) that occur during and after the dressing procedures. EI is used to suppress convulsions that occur after electrical stunning to ensure operator safety to maintain high throughputs speeds while ES is used to induce rapid tenderisation, although having other biochemical and biophysical effects on meat. The objective of the study was to supply information on the effect of different EI and ES treatments, frequencies and pulse widths on the meat quality of beef. There are very little data on the effect of EI when it is combined with ES on meat quality. This study used two different EI frequencies (high – 800 Hz; HFI and low – 15 Hz; LFI) combined with either high (1040 V; HVS) or medium (300 V; MVS) voltage ES to study the effect of these treatments on meat quality. In the following experiment the EI waveform and ES was standardised using HFI with MVS with the frequency being changed to either 5, 15 or 50 Hz. Then the pulse width of the waveform was changed to 0.1, 0.5, 1 and 10 ms to optimise the ES system. Meat quality measurements were made from the Longisimmus dorsi (LD) and Semimembranosus (SM) after 1, 5 and 9 days of chilled storage at 0 C. The LD (shear force = 94.3±2.2; cooking loss = 26.85±0.29; retail drip = 0.996±0.037; storage drip = 2.78±0.155; WBC (water binding capacity) = 45.4±0.36) had significantly lower shear force and higher water binding capacity than the SM (shear force = 103.7±2.5; cooking loss = 34.63±0.25; retail drip = 2.12±0.103; storage drip = 3.63±0.245; WBC = 59.3±0.57). Day of assessment (Day 1 = 122.7±2.9; Day 5 = 87.7±2.2; Day 9 = 81.0±2.4) had a significant effect on tenderness of the LD as shear force declined with an increase of day of assessment. The LFI HVS (storage drip = 3.30±0.223; shear force = 102.9±4.5) produced significantly greater drip during storage and shear force values when compared to the HFI followed by either HVS (storage drip = 2.45±0.261; shear force = 85.2±4.0) or MVS (storage drip = 2.60±0.178; shear force = 94.2±4.2) in the LD, probably attributable to different rates of pH decline post mortem. LFI HVS (a* = 20.79±0.31; chroma = 22.92) and LFI MVS (a* = 20.24±0.27; chroma = 22.23±0.30) had a redder and more vivid bloomed colour than HFI HVS (a* = 19.71±0.33; chroma = 21.49±0.37) and HFI MVS (a* = 20.00±0.27; chroma = 21.98±0.31), while LFI HVS (a* = 15.27±0.40) and HFI MVS (a* = 14.64±0.29) had a redder colour compared to HFI HVS (13.85±0.35) at day 9 for the LD. The oxygen consumption rate (MTT assay) correlated inversely linear (r = -0.63 and -0.73) with the a* values 24 hrs post mortem allowing for 3 hrs of bloom. Stimulation with 15 Hz (0.47±0.040) and 5 Hz (0.41±0.045) had a higher pH decline (ΔpH) during stimulation than 50 Hz (0.29±0.027). Shear force measurements and cooking loss percentage were obtained from the LD after 24 hrs of chilled storage at 0 C. There were no difference between the stimulation treatments for shear force (15 Hz = 121.3±3.3; 5 Hz = 123.8±7.6; 50 Hz =114.8±7.94), while cooking loss was higher in 15 Hz (28.8±0.47) than 50 Hz (25.9±0.71) which correlated (r = 0.43; p = 0.01) with ΔpH. There were no differences between 10 ms (0.46±0.020), 1 ms (0.43±0.020) and 0.5 ms (0.44±0.019) pulse widths on the ΔpH while 0.1 ms (0.33±0.020) had a lower decline. Stimulation with a 1 ms (94.6±5.6) pulse width had the lowest shear force that varied from 10 (111.3±3.8) and 0.1 ms (111.3±5.8). While cooking loss (0.1 = 25.3±0.48; 0.5 = 26.9±0.67; 1 = 25.9±0.63; 10 = 25.5±0.66) and water-holding capacity (0.1 = 36.1±1.60; 0.5 = 37.3±1.42; 1 = 37.5±1.15; 10 = 36.9±1.45) was not affected in the LD after 24 hrs of chilled storage at 0 C. Colour measurements on the SM indicated that a 0.1(a* = 19.38±0.50; chroma = 22.70±0.51), 0.5 (a* = 20.89±0.49; chroma = 24.34±0.56) and 10 ms (a* = 19.69±0.46; chroma = 22.98±0.58) pulse width had a deeper red and a more vivid colour than 1 ms (a* = 16.66±0.37; chroma = 19.99±0.32) at day nine of retail display. In conclusion, HFI improves meat quality when combined with either HVS or MVS and that MVS either improves (colour stability) or has no adverse effects on meat quality (tenderness and WBC) in relation to HVS when combined HFI. In addition, it shows that there are alternative electrical parameters to voltage that can be used to change the pH decline and by changing frequency and pulse width, subtle changes can be made to an ES system. Since every abattoir is different due to layout, chiller space and cooling regime these electrical parameters can be modulated to optimise an electrical stimulation system without expensive modification to the whole system. / AFRIKAANSE OPSOMMING: Die tempo van pH en temperatuur daling is die twee hoof bepalings van na-slag prosseserings uitkomste. Spier pH en temperatuur het ’n gedurige interaksie tydens rigor ontwikkeling en beïvloed die spier sametrekking en proteolitiese ensiem aktiwiteit. Die spier pH kan onafhanklik van temperatuur gemanipuleer word, deur elektriese golfvorms deur die karkas te stuur. Die elektriese golfvorms wat in ag geneem moet word varieer van elektriese impulse tydens bedwelming tot die verskeie golfvorms van elektriese immobilisasie (EI) en stimulasie (ES) wat gebruik kan word gedurende en na die slagproses. EI word gebruik om konvulsies te beheer wat onstaan na elektriese bedwelming om werker veiligheid en hoë deurvloei tempos te verseker, terwyl ES die verouderings proses versnel, alhoewel dit ander biochemiese en biofisiese uitwerkings het op vleis. Die studie het verneem om inligting te verskaf oor die effek van verskillende EI en ES kombinasies, frekwensie en puls wydtes op die kwaliteit van beesvleis. Daar is baie min inligting van EI in kombinasie met ES se effek op vleis kwaliteit. Die studie het gebruik gemaak van twee verskillende (EI) frekwensies (hoog – 800 Hz; HFI and laag – 15 Hz; LFI) wat gekombineer is met of hoë (1040 V; HVS) of medium (300 V; MVS) spanning ES se effek op vleis kwaliteit. In die volgende eksperiment was die EI golfvorm en die ES gestandardiseer en HFI met MVS was gebruik met die frekwensie wat verander is tussen 5, 15 en 50 Hz. Daarna was die pulse wydte van die golfvorm verander tussen 0.1, 0.5, 1en 10 ms om die ES sisteem te optimiseer. Vleis kwaliteit van die Longisimmus dorsi (LD) en Semimembranosus (SM) spiere was bepaal na 1, 5 en 9 dae van verkoelde storing teen 0°C. Die LD (skeurkrag = 94.3±2.2; kookverlies = 26.85±0.29; kleinhandel drup verlies = 0.996±0.037; storing drip verlies = 2.78±0.155; WBV (water bindings vermoë) = 45.4±0.36) het ‘n betekenisvolle laer skeurkrag waardes en hoër water bindings vermoë gehad in vergelyking met die SM (skeurkrag = 103.7±2.5; kookverlies = 34.63±0.25; kleinhandel drupverlies = 2.12±0.103; bergings drupverlies = 3.63±0.245; WBV = 59.3±0.57). Die dag van assesering (Dag 1 = 122.7±2.9; Dag 5 = 87.7±2.2; Dag 9 = 81.0±2.4) het ’n betekenisvolle effek gehad op die skeur krag waardes en het afgeneem met ’n toename in die dag van assesering. LFI HVS (storing drupverlies = 3.30±0.223; skeurkrag = 102.9±4.5) het betekenisvolle hoër vog verliese gehad tydens verkoelde storing en skeur krag wanneer dit vergelyk word met HFI gevolg deur of HVS (storing drupverlies = 2.45±0.261; skeurkrag = 85.2±4.0) of MVS (storing drupverlies = 2.60±0.178; skeurkrag = 94.2±4.2). LFI HVS (a* = 20.79±0.31; chroma = 22.92) en LFI MVS (a* = 20.24±0.27; chroma = 22.23±0.30) het ‘n helder en dieper rooi kleur gehad in vergelyking met HFI HVS (a* = 19.71±0.33; chroma = 21.49±0.37) en HFI MVS (a* = 20.00±0.27; chroma = 21.98±0.31), terwyl LFI HVS (a* = 15.27±0.40) en HFI MVS (a* = 14.64±0.29) ’n rooier en helderer kleur as HFI HVS (13.85±0.35) gehad het in die LD. Die suurstof verbruik tempo (MTT analise) korreleer omgekeerd (r = -0.63 en -0.73) met die a* waardes 24 hr post mortem na 3 hr van blootstelling van lug. Stimulasie met 15 (0.47±0.040) en 5 Hz (0.41±0.045) het ’n hoër pH daling (ΔpH) tydens stimulasie as 50 Hz (0.29±0.027). Skeurkrag waardes en kookverliese is verkry vanaf die LD na 1 dag van verkoelde storing teen 0 C. Daar was geen verskil tussen stimulasie frekwensie se effek of skeurkrag (15 Hz = 121.3±3.3; 5 Hz = 123.8±7.6; 50 Hz =114.8±7.94) nie, terwyl die kookverliese hoër was in die 15 Hz (28.8±0.47) as 50 Hz (25.9±0.71) behandeling wat gekorreleer (r = 0.43; p = 0.01) het met ΔpH. Daar was geen verskill tussen 10 (0.46±0.020), 1 (0.43±0.020) en 0.5 ms (0.44±0.019) puls wydtes se effek op ΔpH nie, terwyl 0.1 (0.33±0.020) ms ‘n kleiner afname tot gevolg gehad het. Stimulasie met ‘n 1 ms (94.6±5.6) puls wydte het die laagste skeurkrag gehad wat verskil het van die 10 (111.3±3.8) and 0.1 ms (111.3±5.8) puls wydtes, terwyl kookverliese (0.1 = 25.3±0.48; 0.5 = 26.9±0.67; 1 = 25.9±0.63; 10 = 25.5±0.66) en waterbindingsvermoë (0.1 = 36.1±1.60; 0.5 = 37.3±1.42; 1 = 37.5±1.15; 10 = 36.9±1.45) nie beïvloed was nie. Kleur metings van die SM het getoon dat ‘n 0.1 (a* = 19.38±0.50; chroma = 22.70±0.51), 0.5 (a* = 20.89±0.49; chroma = 24.34±0.56) en 10 ms (a* = 19.69±0.46; chroma = 22.98±0.58 puls wydtes die helder en dieper rooi kleur gehad het as 1 ms (a* = 16.66±0.37; chroma = 19.99±0.32) teen dag 9 van kleinhandel vertoning. Ter opsomming, lei HFI tot beter vleis kwaliteit wanneer dit gekombineer word met of HVS of MVS. Verder lei MVS tot of ’n verbetering (kleur stabiliteit) of geen nadelige effek op vleis kwaliteit (sagtheid en WBV) in vergelyking met HVS wanneer dit gekombineer word met HFI. Die studie bewys ook dat daar ander elektriese parameters bestaan as spanning, wat verander kan word om die pH daling te beïvloed. Deur die frekwensie en pulswydte te verander, kan klein veranderinge aangebring word aan ’n ES sisteem. Elke abattoir is verskillend as gevolg van uitleg, koelkamer spasie en verkoelings tempo en hierdie elektriese parameters kan verander word om ’n ES sisteem te optimiseer sonder enige duur veranderinge aan die hele sisteem.

Made available in DSpace on 2014-08-13T14:51:00Z (GMT). No. of bitstreams: 0 Previous issue date: 2014-05-30Bitstream added on 2014-08-13T17:59:42Z : No. of bitstreams: 1 000775884.pdf: 269960 bytes, checksum: 462a64df99b4bacd20cb4a95436b7698 (MD5) / O objetivo deste estudo foi verificar o efeito da seleção para peso pós desmame nos parâmetros das curvas de crescimento das características de crescimento e de carcaça. Foram analisados registros de 2404 animais da raça Nelore provenientes de três linhas de seleção: duas linhas de seleção para maior peso pós desmame, denominadas Nelore Seleção (NeS) e Nelore Tradicional (NeT), e de uma linha controle (NeC) em que os animais são selecionados para a média do peso. Foram estudadas as características peso corporal (PC), altura da garupa (ALT), área do músculo longissimus dorsi (AOL), espessura de gordura subcutânea do dorso (EGS) e da garupa (EGG), obtidas dos 8 aos 20 meses de idade para os machos e dos 11 aos 26 meses para as fêmeas. Os parâmetros A (valor assintótico) e k (taxa de crescimento) foram estimados pela técnica de modelos não lineares, incluindo o efeito fixo de rebanho (NeS, NeT e NeC) no modelo de análise, com o objetivo de verificar diferenças nos parâmetros estimados nos diferentes rebanhos. Os animais selecionados (NeS e NeT) apresentaram maior taxa de crescimento em comparação com o rebanho controle (NeC), para todas as características. O efeito de linha de seleção sobre os parâmetros da curva de crescimento foi significativo (<0,001) para PC, ALT e AOL nos machos, e nas fêmeas para EGS e EGG. A seleção para peso pós-desmame é efetiva em alterar as curvas de crescimento, resultando em animais com maior potencial de crescimento. / The purpose of this study was to evaluate the effect of selection for postweaning weight parameters in growth curves of growth and carcass traits. Records of 2404 Nellore animals from three selection lines were analyzed: two selection lines for high postweaning weight (NeS and NeT), Selection Nellore (NeS) and Traditional Nellore (NeT), and a control line (NeC), in which animals are selected for the mean weight. The measurements were performed: body weight (BW), hip height (ALT), Longissimus muscle area (AOL), back fat thickness (EGL) and rump fat thickness (EGG). Records were collected from 8 to 20 months of age for males and 11 after 26 months of age for females. The parameters A (asymptotic value) and k (growth rate) were estimated by technique of nonlinear models using NLIN procedure of SAS, that included fixed effect of herd (NeS NeT and NeC) in the model, with the objective of evaluate differences in the estimated parameters in different herds. The selected animals (NES and NeT) showed higher growth rate than control herd (NEC) for all traits. Herd effect on curves parameters was significant (<0,001) for PC, ALT and AOL in males, and females for EGS and EGG. Selection for postweaning weight was effective in altering growth curves, resulting in animals with greater growth potential.

CNPq / O trabalho foi desenvolvido na Universidade Tecnológica Federal do Paraná, Câmpus Dois Vizinhos, com o objetivo de avaliar o desempenho dos bovinos terminados em pastagem de clima temperado consorciada com leguminosa ou suplementação energética e as características da carne e carcaça desses animais. Foram utilizados 18 novilhos, do grupo genético 1/4 Marchegiana 1/4 Aberdeen Angus 2/4 Nelore, com peso inicial de 360 kg e 19 meses de idade, divididos em três tratamentos: pastagem de aveia branca, pastagem de aveia branca consorciada com ervilhaca e pastagem de aveia branca associada com suplementação energética a base de milho triturado (1% do peso vivo por dia). O pasto apresentou interação significativa entre o período de avaliação e os tratamentos. A participação da ervilhaca aumentou no decorrer do experimento de 3,51% para 12,21%, comportamento inverso observado da participação da aveia. A massa de forragem, carga animal, oferta de forragem e taxa de acúmulo diário não apresentaram diferença entre os tratamentos. Ganho de peso médio diário, peso vivo por hectare e peso vivo total foram melhores para o tratamento de aveia com suplementação quando comparado com o tratamento de pastagem de aveia solteira sendo intermediários para o tratamento de aveia associada com leguminosa. Após a avaliação do desempenho da pastagem e dos bovinos, os animais foram abatidos e avaliados as características de carcaça e carne. O peso de abate dos novilhos mantidos em pastagem de aveia com suplementação foi superior ao dos animais mantidos exclusivamente em pastejo com aveia, porém não diferiram do peso de abate dos animais mantidos na pastagem de aveia associada com ervilhaca. O peso de carcaça quente e o peso de carcaça fria dos animais suplementados foi superior em relação ao peso das carcaças dos animais tratados com aveia ou aveia e ervilhaca. A conformação de carcaça dos novilhos com suplementação foi superior dos animais mantidos com aveia e ervilhaca. Não houve diferença entre os tratamentos para as medidas métricas das carcaças. Para os cortes comerciais, o corte traseiro + costilhar foi mais pesado para os bovinos tratados com suplementação. A carne dos animais terminados com aveia apresentou menor maciez quando avaliada pelo painel dos degustadores, exigindo maior força ao cisalhamento. No presente trabalho os novilhos terminados com suplementação apresentaram melhor desempenho e melhores características de carcaça e qualidade de carne quando comparado com os novilhos terminados na pastagem de aveia solteira, com valores intermediários para os novilhos terminados na aveia associada com ervilhaca. / The work was developed at Federal Technological University of Paraná, Campus Dois Vizinhos, in order to evaluate the performance of cattle finished on pasture temperate intercropped with legumes or energy supplementation and meat characteristics and housing these animals. We used 18 bullocks, the genotype 1/4 Marchegiana quarter Aberdeen Angus 2/4 Nellore with an initial weight of 360 kg and 19 months of age, divided into three treatments: pasture oat, oat intercropped with white vetch and oat pasture supplementation associated with energy-based ground corn (1% body weight per day). The pasture showed significant interaction between the period of evaluation and treatment. The participation of vetch increased during the experiment from 3.51% to 12.21%, an opposite behavior observed for the participation of oats. The herbage mass, stocking rate, forage supply and accumulation rate did not differ between treatments. Average daily weight gain, liveweight per hectare and total live weight were better for treating oats with supplementation compared with the treatment of oat maiden being intermediaries for the treatment of oats associated with legumes.After evaluating the performance of pasture and cattle, the animals were killed and evaluated carcass characteristics and meat. The slaughter weight of steers grazing oats supplementation was superior to animals raised on pasture with oats,but did not slaughter weight of animals kept in oat associated with vetch.The hot carcass weight and cold carcass weight of supplemented animals was higher than the weight of the carcasses of animals treated with oatmeal or oat and vetch.The carcass conformation of the steers was greater with supplementation of animals maintained on oats and vetch. There was no difference between treatments for metric measurements of carcasses.For commercial cuts, cutting back + ribs was heavier for cattle treated with supplementation. Meat from animals finished with oats showed less tenderness as assessed by the panel of tasters, requiring greater shear force. In this study the steers with supplementation performed better and better carcass characteristics and meat quality when compared to steers on pasture single oat, with intermediate values for steers associated with oat with vetch.

Orientador: André Mendes Jorge / Coorientador: Maria Eugênia Zerlotti Mercadante / Banca: Otavio R. M. Neto / Banca: Lenira El Faro Zadra / Resumo: O objetivo deste estudo foi verificar o efeito da seleção para peso pós desmame nos parâmetros das curvas de crescimento das características de crescimento e de carcaça. Foram analisados registros de 2404 animais da raça Nelore provenientes de três linhas de seleção: duas linhas de seleção para maior peso pós desmame, denominadas Nelore Seleção (NeS) e Nelore Tradicional (NeT), e de uma linha controle (NeC) em que os animais são selecionados para a média do peso. Foram estudadas as características peso corporal (PC), altura da garupa (ALT), área do músculo longissimus dorsi (AOL), espessura de gordura subcutânea do dorso (EGS) e da garupa (EGG), obtidas dos 8 aos 20 meses de idade para os machos e dos 11 aos 26 meses para as fêmeas. Os parâmetros A (valor assintótico) e k (taxa de crescimento) foram estimados pela técnica de modelos não lineares, incluindo o efeito fixo de rebanho (NeS, NeT e NeC) no modelo de análise, com o objetivo de verificar diferenças nos parâmetros estimados nos diferentes rebanhos. Os animais selecionados (NeS e NeT) apresentaram maior taxa de crescimento em comparação com o rebanho controle (NeC), para todas as características. O efeito de linha de seleção sobre os parâmetros da curva de crescimento foi significativo (<0,001) para PC, ALT e AOL nos machos, e nas fêmeas para EGS e EGG. A seleção para peso pós-desmame é efetiva em alterar as curvas de crescimento, resultando em animais com maior potencial de crescimento. / Abstract: The purpose of this study was to evaluate the effect of selection for postweaning weight parameters in growth curves of growth and carcass traits. Records of 2404 Nellore animals from three selection lines were analyzed: two selection lines for high postweaning weight (NeS and NeT), Selection Nellore (NeS) and Traditional Nellore (NeT), and a control line (NeC), in which animals are selected for the mean weight. The measurements were performed: body weight (BW), hip height (ALT), Longissimus muscle area (AOL), back fat thickness (EGL) and rump fat thickness (EGG). Records were collected from 8 to 20 months of age for males and 11 after 26 months of age for females. The parameters A (asymptotic value) and k (growth rate) were estimated by technique of nonlinear models using NLIN procedure of SAS, that included fixed effect of herd (NeS NeT and NeC) in the model, with the objective of evaluate differences in the estimated parameters in different herds. The selected animals (NES and NeT) showed higher growth rate than control herd (NEC) for all traits. Herd effect on curves parameters was significant (<0,001) for PC, ALT and AOL in males, and females for EGS and EGG. Selection for postweaning weight was effective in altering growth curves, resulting in animals with greater growth potential. / Mestre

CAPES / Avaliaram-se o desempenho produtivo e o rendimento de cortes comercias da carcaça de novilhos não-castrados ou castrados abatidos em idade jovem ou superjovem terminados em confinamento. Os animais foram alimentados com dieta contendo 11,2% de proteína bruta e 3,07 Mcal de energia digestível/kg de matéria seca, composta de 50% de volumoso e 50% de concentrado. A idade inicial no inicio do confinamento dos animais superjovens e jovens foi de 9 e 22 meses, respectivamente. Maior PF foi observado para os animais jovens não castrados (581,11 kg) em relação aos superjovens não-castrados, jovens castrados e não castrados (478,00, 455,22 e 437,29 kg, respectivamente). O GMD foi 31% superior em favor dos novilhos jovens em relação aos superjovens. O CMS foi 27% superior para os novilhos jovens sobre os superjovens e os novilhos não-castrados consumiram 9% mais quando comparados aos castrados. Maior CMS por 100 kg de PV foi observado para os novilhos jovens castrados (2,58 kg). A diferença de peso da meia carcaça entre animais não-castrados e castrados foi de 43% para os jovens e de 18% para os superjovens. Novilhos não-castrados apresentaram maior percentual de dianteiro (8%). Maior percentual do corte serrote foi observado nos novilhos jovens castrados. Novilhos jovens apresentaram maior ganho de peso médio diário, bem como, novilhos jovens não-castrados apresentaram maior peso final. Animais não-castrados apresentam maiores pesos de meia carcaça fria, percentual de dianteiro e porção comestível do dianteiro em relação aos castrados. / It was evaluated the productive performance and the yield of commercial cuts of the carcass of non-castrated or castrated slaughtered at a young age or young steers finished feedlot. The animals were fed a diet containing 11.2% crude protein and 3.07 Mcal of digestible energy / kg of dry matter, composed of 50% roughage and 50% concentrate. The initial age at the beginning of confinement of young steers and steers were 9 and 22 months, respectively. Greater PF was observed for non-castrated young animals (581.11 kg) in relation to young steers non-castrated, steers castrated and non-castrated (478.00, 455.22 and 437.29 kg, respectively). The ADG was 31% higher for the steers in relation to young steers. The DMI was 27% higher for steers on young steers and non-castrated consumed 9% more compared to the castrated. Most DMI per 100 kg of body weight was observed for the castrated steers (2.58 kg). The half-carcass weight difference between non-castrated and castrated animals was 43% for steers and 18% for young steers. Non-castrated showed higher forequarter percentage (8%). Higher percentage hacksaw cut was observed in castrated steers. Steers showed higher average daily gain weight, as well as non-castrated steers showed higher final weight. non-castrated animals have higher half cold carcass weights, front percentage and of edible portion of the front in relation to castrated.

CAPES / Avaliaram-se o desempenho produtivo e o rendimento de cortes comercias da carcaça de novilhos não-castrados ou castrados abatidos em idade jovem ou superjovem terminados em confinamento. Os animais foram alimentados com dieta contendo 11,2% de proteína bruta e 3,07 Mcal de energia digestível/kg de matéria seca, composta de 50% de volumoso e 50% de concentrado. A idade inicial no inicio do confinamento dos animais superjovens e jovens foi de 9 e 22 meses, respectivamente. Maior PF foi observado para os animais jovens não castrados (581,11 kg) em relação aos superjovens não-castrados, jovens castrados e não castrados (478,00, 455,22 e 437,29 kg, respectivamente). O GMD foi 31% superior em favor dos novilhos jovens em relação aos superjovens. O CMS foi 27% superior para os novilhos jovens sobre os superjovens e os novilhos não-castrados consumiram 9% mais quando comparados aos castrados. Maior CMS por 100 kg de PV foi observado para os novilhos jovens castrados (2,58 kg). A diferença de peso da meia carcaça entre animais não-castrados e castrados foi de 43% para os jovens e de 18% para os superjovens. Novilhos não-castrados apresentaram maior percentual de dianteiro (8%). Maior percentual do corte serrote foi observado nos novilhos jovens castrados. Novilhos jovens apresentaram maior ganho de peso médio diário, bem como, novilhos jovens não-castrados apresentaram maior peso final. Animais não-castrados apresentam maiores pesos de meia carcaça fria, percentual de dianteiro e porção comestível do dianteiro em relação aos castrados. / It was evaluated the productive performance and the yield of commercial cuts of the carcass of non-castrated or castrated slaughtered at a young age or young steers finished feedlot. The animals were fed a diet containing 11.2% crude protein and 3.07 Mcal of digestible energy / kg of dry matter, composed of 50% roughage and 50% concentrate. The initial age at the beginning of confinement of young steers and steers were 9 and 22 months, respectively. Greater PF was observed for non-castrated young animals (581.11 kg) in relation to young steers non-castrated, steers castrated and non-castrated (478.00, 455.22 and 437.29 kg, respectively). The ADG was 31% higher for the steers in relation to young steers. The DMI was 27% higher for steers on young steers and non-castrated consumed 9% more compared to the castrated. Most DMI per 100 kg of body weight was observed for the castrated steers (2.58 kg). The half-carcass weight difference between non-castrated and castrated animals was 43% for steers and 18% for young steers. Non-castrated showed higher forequarter percentage (8%). Higher percentage hacksaw cut was observed in castrated steers. Steers showed higher average daily gain weight, as well as non-castrated steers showed higher final weight. non-castrated animals have higher half cold carcass weights, front percentage and of edible portion of the front in relation to castrated.

Leptin, a 16 (kilo Dalton) kDa hormone secreted predominantly by white adipocytes, regulates reproduction, energy intake and expenditure, and is involved in immune system function. Previous studies have identified associations between polymorphism E2FB in the leptin gene (lep) of cattle and milk quality and quantity, feed intake, and fat deposition in dairy and beef cattle though further studies have shown inconclusive results. Furthermore, indigenous South African cattle have not been involved in lep investigations or the applicability of the marker in South African beef grading systems. An investigation was conducted into the association of an SNP of a cytosine (C) to thymine (T) SNP (single nucleotide polymorphism) mutation in exon 2 of the bovine lep (leptin) gene with weight gain, body condition, carcass fat content and quality in a population of indigenous Nguni cattle (n = 70) as well as a population of exotic British Hereford cattle (n = 54). The Hereford population had higher T-allele frequencies and a lower P-value (P = 0.172) for the E2FB genotypes than the Nguni population (P = 0.958). The resulting E2FB lep genotypes CC, CT and TT did not show an association with the pre- and post-slaughter traits initial live weight (ILW), body condition score (BCS), slaughter live weight (SLW), carcass fat content (FAT), carcass conformation (CFN) or warm carcass mass (WCM) for either population though t-tests revealed an association with the CT genotype with increased ILW than TT and a significantly higher WG in the TT genotypes than the CT (P<0.05). Subsequently, differences in pre- and post-slaughter traits in both populations were largely attributable to breed differences. The Hereford population exhibited significantly higher WG, CFN, SLW, WCM and CCM (P<0.05) than the Nguni population. The Nguni displayed significantly higher ILW and BCS values when graded in terms of the commercial South African AAA feedlot system. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2010.

CAPES / O trabalho foi conduzido para avaliar a terminação de bovinos de corte em pastagem de Capim Aruana sobressemeado com aveia e azevém associados à leguminosa e/ou adubação nitrogenada. O delineamento foi inteiramente casualizado, com três tratamentos e três repetições. Foram testados três sistemas forrageiros no período de inverno,tendo como base a pastagem de Aruana (Panicum maximum, cv.Aruana) sobressemeado com aveia e azevém: ‘Nitrogênio’ (N) –200 kg de N ha-1; Amendoim forrageiro e 100 kg de N ha-1; Ervilhaca e 100 kg de N ha-1. A adubação foi dividida em cinco aplicações, o período experimental foi de 127 dias. Foi utilizado o sistema de lotação continua, com carga animal variável, a oferta de forragem preconizada de 9,0 kg/100 kg de peso vivo. A pastagem foi manejada utilizando-se de 24 animais castrados de 21 meses, com peso vivo médio inicial de 425 kg, destes 18 foram teste e seis reguladores. As avaliações da forragem e do desempenho animal foram realizadas a cada 21 dias. A avaliação do comportamento animal foi realizada duas vezes por período, durante 24 horas em cada avaliação. O maior nível de adubação nitrogenada proporcionou diferenças na estrutura da pastagem, porém a produção diária de forragem foi semelhante entre os tratamentos. O tempo de pastejo na consorciação com ervilhaca foi superior ao amendoim forrageiro e semelhante aos demais na adubação com 200 kg de N ha-1, no entanto, o ganho médio diário foi semelhante para os tratamentos. O tempo de 20 bocados e o número de passos por minuto foram superiores na maior adubação nitrogenada quando comparado a consorciação com amendoim,e semelhante à estes na consorciação com ervilhaca. Embora o consórcio com amendoim associado a 100 kg de N ha-1 tenha causado redução no tempo de pastejo e apresentado maior tempo de ruminação, não ocorreram diferenças no desempenho produtivo e nas características de carcaça dos animais em terminação. / The objective was to evaluate finishing of beef steers in Aruana pasture overseeded with oats and ryegrass and mixed with legume with or no nitrogen fertilization. The design was completely randomized, with three treatments and three replications. Three forage systems have been tested tested in winter, based on Aruana fodder (Panicum maximum, cv. Aruana) mixed with oats and ryegrass: 'Nitrogen' (N) -200 kg of N ha-1; Forage peanut and 100 kg of N ha-1; Vetch and 100 kg of N ha-1. The fertilization was shared in five applications, for 127 days. The continuous stocking system was used, with variable stocking rate, and forage on offer of 9,0 kg/100 kg of live weight. The grazing was managed with 24 castrated animals of 21 months,425 kg of initial avarage live weight. Being 18 testers and six regulators. Evaluations of forage and animal performance were made every 21 days. For animal behavior, the evaluations were done twice in each period, for 24 hours. The highest level of nitrogen fertilization showed differences in pasture structure, however, the forage daily production was similar between the treatments. The grazing time on mixture with vetch was superior for Forage peanut and similar to the others when fertilization was 200 kg of N ha-1, although, the average daily gain was similar for both treatments. The time of 20 bites and the number of steps per minute were higher for higher nitrogen fertilization, when compared to the peanut intercropping, and similar to those when mixed with vetch. Although the peanut consortium associated with 100 kg of N ha-1 caused a reduction in grazing time and presented a longer rumination time, there were no differences in the productive performance and carcass characteristics of the finished animals.