ABSTRACT Determining what and how much each environmental factor affects pregnancy is crucial to the sustainability and management of beef cow herds. The study evaluated through logistic regression the effect of environmental variables on the increase or reduction in the pregnancy rate of beef cows. The average pregnancy rate in the cows was 73 %, with an average age for the herd of 3.7 years. An increase in age of one year represented a 30 % increase in pregnancy, while a reduction of one year reduced the odds of pregnancy in the cows by 23 %. During the lactation period, an extra seven days’ lactation reduced the odds of pregnancy by 12 %. For every seven days that weaning was brought forward, the cows’ pregnancy odds increased by 14 %. An increase of 0.1 kg in average daily gain represented an increase of 17 % and 15 % in the odds of pregnancy during the first 60 days post-partum and 60 days to the end of the reproductive period. On the other hand, the loss of 0.1 kg in average daily gain resulted in a 14 % and 13 % reduction in the cows’ pregnancy odds, respectively. Factors such as age, the precocity of calving in the calving season, the time the calf remains with the cow and better performance in cows between calving and the end of the mating are strategies that increase the chances of pregnancy in beef cows.

Abstract Potential variables for the reproductive success of beef cows were evaluated. Included in the model were the age of the cow at calving; the interval between the Julian calving date and the end of the breeding season; the body weight and conditions at calving, at 75 days post-partum and at the end of the breeding season; and the mean daily variation in weight between these dates. Logistic regression was used in the analysis, with the parameters evaluated using the odds ratio statistic, estimating the chance of pregnancy. The mean rate of pregnancy was 84% and 55% for early and late-weaned cows, respectively. For early weaned cows, the regression variables were the Julian calving date, age of the cow, weight gain from calving to 75 days post-partum, and from 75 days post-partum to the end of the reproductive period. For late-weaned cows, there were only two regression variables, weight at calving and weight gain from calving to the end of the reproductive period. For every year above the average age of the herd, early weaned cows have an 80.9% greater chance of pregnancy, while a reduction of one year reduces the chance of pregnancy by 44.7%. In early weaned cows, every seven days after the mean Julian calving date reduces the chances of pregnancy by 22.6%, whereas every seven days before the mean calving date increases pregnancy by 29.2%. Greater gains in cow body weight, from calving to the end of the reproductive period, determine a greater probability of pregnancy.

Resumo O período do parto influencia a produtividade e a eficiência reprodutiva dos rebanhos. O objetivo deste estudo foi avaliar dois meses de parto (outubro e novembro) e seus efeitos sobre a eficiência de um rebanho de cria por três anos consecutivos. Foram realizadas 298 avaliações de vacas Braford aos três, quatro e cinco anos de idade, com seus bezerros desmamados aos 148 dias de idade. As características de desempenho dos pares vaca / bezerro foram avaliadas com o mês e o sexo do bezerro como variáveis independentes. Os animais foram mantidos em um único grupo nos três anos de observação. As vacas que pariram em novembro foram mais pesadas e tiveram maior escore de condição corporal no parto. As vacas que pariram em outubro foram mais pesadas e produziram bezerros mais pesados no desmame. Os bezerros machos foram mais pesados ao nascer e ao desmame do que as fêmeas (30,8 vs 28,6 kg e 118,9 vs 114,7 kg, respectivamente). A taxa de prenhez foi de 82,35 e 69,23% para as vacas que pariram em outubro e novembro, respectivamente. Os intervalos de partos foram mais curtos nas vacas paridas em novembro. As vacas que pariram em outubro foram mais eficientes quando comparadas com as que pariram em novembro, com maior taxa de fertilidade real. A produção de quilogramas do par bezerro / vaca foi maior em vacas que pariram em outubro.

Abstract The calving period influences productivity and reproductive efficiency the herds. The objective of this study was to evaluate two calving months (October and November) and their effect on the efficiency of a breeding herd for three consecutive years. A total of 298 Braford cows were evaluated at three, four, and five years of age, with their calves early-weaned at 148 days of age. The performance characteristics of the cow/calf pairs were evaluated with the calving month and calf sex as the independent variables. The animals were kept as a single group for the three years of observation. Cows calving in November were heavier and had a higher body condition score at calving. Cows calving in October were heavier and produced heavier calves at weaning. Male calves were heavier at birth and weaning than females (30.8 vs 28.6 kg and 118.9 vs 114.7 kg, respectively). The pregnancy rate was 82.35 and 69.23% for cows calving in October and November, respectively. Calving intervals were shorter in cows calving in November. Cows calving in October were more efficient compared with those calving in November, with a higher actual fertility rate. The production of kilograms of the calf/cow pair was higher for cows calving in October.

ABSTRACT Two hundred seventeen grass-finished Braford steers were assessed by ultrasonic scanning and subsequently harvested with their pistol hindquarters fabricated into boneless wholesale cuts. The Longissimus thoracis muscle area and subcutaneous fat depths were measured. The objectives of this study were: 1) to develop prediction equations for weights of the pistol hindquarter and high-value commercial cuts, and 2) to estimate sample size needed for experiments comparing pistol hindquarter retail product weight using either physically or ultrasonically measured carcass traits. Carcass measurements explained 44 % to 94 % of the variation in weights of individual cuts, whereas, measurements that were made using ultrasound explained 42 % to 90 % of the variation in the weights. Models used to predict the weight of pistol hindquarter retail product with carcass measures and ultrasound measures showed high coefficient of determination (R 2 = 0.92 and 0.97, respectively). Whether based on carcass or ultrasound measures, models used to estimate weight percentage of fat trimmed from the pistol hindquarter had lack of fit. In general, models for individual cuts weights that used traits measured with ultrasound as independent variables approached the accuracy of models using carcass traits. Thus, only slightly greater samples sizes were required to have equivalent power to detect differences in retail product weights using ultrasound measures. For experiments of equivalent power, differences in the number of animals required may be offset by avoiding costs for slaughter and fabrication.

ABSTRACT Body development and reproductive performance of a hundred forty-two 14 to 15-month-old heifers, classified at weaning according to frame size as small, medium, and large, were evaluated. The parameters evaluated were: body weight, hip height, body condition score, weight gain, ovarian activity, and pregnancy rate. At weaning, body weight and hip height were significantly different among frame scores, (small – 133.0 kg, 92.2 cm; medium – 158.5 kg, 96.6 cm; and large – 185.2 kg; 100.2 cm). After weaning, heifers grazed together on natural pastures during the autumn and on ryegrass (Lolium multiflorum La.) during the winter and spring. Frame score differences remained until the beginning of the breeding season (BS), starting on average at 14 months of age. Weight gain between weaning and the beginning of BS was not different among frame scores (0.740 kg/day, on average). Body weights at the beginning of the BS were significantly different, of 255.7 kg (53.3% of the mature weight) for small heifers, 285.0 kg (59.4%) for medium heifers, and 307.6 kg (64.1%) for large heifers. Ovarian activity at the beginning of the BS was not different among the three groups. The average weight gain values during the BS of 0.492, 0.472, and 0.421 kg/day for small, medium, and large heifers, respectively, were significantly different. Pregnancy rates were not different among groups (small, 71.4%; medium, 76.4%; and large, 76.5%). Frame score did not influence the reproductive performance of heifers, but the small and medium heifers conceived 29 and 20 days earlier, respectively, than the large heifers.

ABSTRACT Aiming at breeding heifers with 14-15 months of age, 100 Hereford calves were subjected to different feeding systems. Heifers grazed on a natural pasture in early winter, fed or not a supplement (14% crude protein; 72% total digestible nutrients), were transferred to a ryegrass pasture for 73 days, and then returned to a natural pasture for 15 days until the beginning of the breeding season. During the last 15 days on ryegrass pasture and the 15 days of the return to the natural pasture, half of the heifers of the two previous systems were offered the supplement, thereby establishing four feeding treatments. Heifers supplemented during the second period, independently of supplementation during the first grazing period, presented higher average daily gain and greater backfat values than the non-supplemented heifers. The breeding season extended for 75 days. At the start of the breeding season (November 18), heifers supplemented during both periods presented higher body condition score and body weight. The highest percentage of puberty was determined in heifers supplemented in the early winter. Heifers supplemented during both periods presented the highest pregnancy rate. Pregnant heifers presented higher average daily gain when fed the supplement during the second period, as well as higher relative pelvic area, body weight, and body condition score at the start and end of the breeding season. To an expressive pregnancy in 14- to 15- month-old heifers, higher weaning weights and pasture allowance are required to get a better answer to supplements offered.

This experiment evaluated the performance of 84 Braford steers grazing on summer and winter cultivated pastures fed or not fed an energy-protein supplement. Steers were 10 months old and weighed, on average, 165 kg at the beginning of the trial. Steers grazed on cultivated winter pasture, consisting of black oats (Avena strigosa) and ryegrass (Lolium multiflorum Lam.), and then on cultivated summer pasture, consisting of Napier grass (Pennisetum purpureum). The following treatments were applied: SS - supplement was fed during both seasons; SN - supplement was fed only during the winter; NS - supplement was fed only during the summer; and NN - steers were not fed any supplement. Supplementation resulted in higher body weight and better body condition score (SS: 369.2 and 4.52; SN: 335.2 and 4.01; NS: 352.5 and 4.49; SS: 322.5 and 3.83). Longissimus dorsi area was larger in supplemented steers, which also presented thicker backfat when compared with those not fed any supplement (3.67 and 2.29 mm, respectively).

This study evaluated yearling growth and reproductive performance of Hereford heifers at 24-26 months of age grazing on natural pastures at two stocking rates during winter and spring, associated or not to improved natural pastures. Heifers were classified according to three weight groups (Light, Medium and Heavy) and randomly distributed into four feeding management practices: 0.6 AU (1 animal unit = 450-kg body weight) - heifers on natural pastures at a stocking rate of 0.6 AU/ha; 0.8 AU - heifers on natural pastures at a stocking rate of 0.8 AU/ha; 0.6 AUI - heifers on natural pastures at a stocking rate of 0.6 AU/ha and on improved natural pastures between Sept 1st and Nov 1st; 0.8 AUI - heifers on natural pasture at a stocking rate of 0.8 AU/ha and on improved natural pastures between Sept 1st and Nov 1st. The stocking rate of 0.8 AU resulted in significant weight loss during winter months (-0.138 and -0.356 kg for 0.6 and 0.8 AU, respectively). Heifers grazing during the spring on improved natural pastures presented higher weight gain before the breeding season and higher body weight and body condition score in the beginning and end of the breeding season in relation to those grazing only on natural pastures. Heifers kept at 0.6 AU/ha obtained 69.7% pregnancy rate, which was significantly higher than the 54.2% of those managed at 0.8 UA/ha. Heifers grazing on improved natural pastures during the spring achieved 83.8% pregnancy rate, whereas those maintained on natural pastures achieved only 40.2%. Light and medium heifers lost less weight during the winter as compared with the heavy ones, but weight differences between groups remained until the end of the breeding season. Heavy heifers have higher pregnancy rates. Heifers submitted to lower stocking rate and those grazing on improved natural pastures conceive earlier.

Objetivou-se com este trabalho avaliar os rendimentos cárneos total e individual de cortes desossados, retalho comestível, retalho descartado e ossos de carcaças de 38 novilhos Braford castrados abatidos com 22 meses de idade após terminação em confinamento. As carcaças foram classificadas em três categorias, de acordo com cobertura de gordura: uniforme sobre toda a carcaça, com espessura de gordura de aproximadamente 6-8 mm sobre a 12ª costela; desuniforme, com espessura de gordura de 3-5 mm; e escassa, com espessura de gordura de 1-2 mm. A quebra durante o resfriamento diminuiu com o aumento da gordura de cobertura e foi de 2,57; 2,22 e 1,96%, respectivamente, para as carcaças de cobertura escassa, desuniforme e uniforme, ao passo que o rendimento de ponta-de-agulha aumentou, atingindo valores de 13,04; 13,47 e 14,36%. Os rendimentos de desossa foram maiores nas carcaças de cobertura escassa (78,70%) em relação às de cobertura uniforme (77,62%), e isso é resultado do menor percentual de retalhos descartados, que aumentou de acordo com a gordura de cobertura (4,40; 5,14; e 6,01%, respectivamente para as carcaças de cobertura escassa, desuniforme e uniforme). Os rendimentos de costela-janela e de costela-primeiro-corte foram maiores nas carcaças com maior espessura de gordura, enquanto os percentuais de coxão de fora e de coxão de dentro foram maiores nas carcaças de cobertura escassa em relação às de cobertura uniforme. Novilhos castrados Braford podem ser abatidos com menor cobertura de gordura, pois a baixa cobertura de gordura não prejudica o rendimento de cortes secundários. O aumento de gordura de cobertura diminui as perdas durante o resfriamento, principalmente em cortes com pequenas aparas.

The objective of this study was to evaluate total and individual meat yield of boneless cuts, retail cuts, descarded trimmings and carcass bones of 38 Braford castrated steers, slaughtered at 22 months of age after feedlot finishing. Carcasses were classified in three ranks according to fat coverage: even fat coverage over the carcass, with fat thickness of approximately 6-8 mm on the 12th rib; animals with uneven fat cover, with fat thickness of 3-5 mm and steers with insufficient fat coverage over the carcass, with fat thickness of 1-2 mm. Shrinkage losses decreased as fat coverage increased, and it was 2.57, 2.22, and 1.96%, respectively, for insufficient, uneven, and even fat coverage whereas flank yield increased, reaching values of 13.04, 13.47 and 14.36%. Boneless yield was the highest in carcasses with insufficient fat coverage (78.70%) when compared to even fat coverage (77.62%), which is a result of the lowest trimming percentage, which increased according to coverage fat (4.40; 5.14 and 6.01%, respectively for carcass with insufficient fat coverage, uneven fat coverage and even fat coverage). Back rib and short rib yields were the greatest in carcasses with the largest fat thickness, whereas percentage of silverside and topside were the greatest in carcass with insufficient fat coverage compared to the ones with even fat coverage. Braford castrated steers can be slaughtered with the smallest fat coverage because the low fat coverage does not affect negatively yield of secondary cuts. Increase in coverage fat reduces shrinkage losses mainly in cuts submitted to little fat trimming.

O trabalho avaliou o desempenho reprodutivo de vacas primíparas aos três anos de idade, submetidas previamente ou não à suplementação protéica no sobreano sobre pastagens naturais. Após o parto, foram manejadas em pastagens naturais ou naturais melhoradas. Os manejos alimentares foram: em pastagem natural na recria e nos períodos de gestação, pós-parto e reprodutivo; em pastagem natural com suplemento protéico na recria e somente pastagem natural durante os períodos de gestação, pós-parto e reprodutivo; em pastagem natural durante a recria e período de gestação, em pastagem natural melhorada (Lolium multiflorum L., Trifolium repens cv. Yi e Lotus corniculatus L. cv. São Gabriel) nos períodos pós-parto e reprodutivo; em pastagem natural com suplemento protéico na recria, em pastagem natural no período de gestação e em pastagem natural melhorada nos períodos pós-parto e reprodutivo. As vacas não diferiram em peso corporal, porém do parto ao início do acasalamento vacas em pastagem natural melhorada tiveram maiores ganhos de peso do que as vacas mantidas em pastagem natural (0,230 vs 0,109 kg/dia). Vacas no pós-parto em pastagens naturais perderam 1,0 ponto de condição corporal durante o acasalamento, determinante da menor taxa de prenhez e de concepções mais tardias em relação às vacas em pastagem natural melhorada. Vacas que conceberam apresentaram maior peso (440 vs 413 kg) e condição corporal (4,14 vs 3,66 pontos) no final do acasalamento do que as vacas não prenhes.

This work evaluated the reproductive performance of first-calf cows at three years of age, submitted or not to protein supplementation at yearling on natural pastures. After calving, cows were managed on natural or improved pastures. The feeding managements were the following: on natural pastures as yearlings and during pregnancy, post-calving period and breeding season; on natural pastures with protein supplement as yearlings and only natural pasture during pregnancy, post-calving and breeding season; on natural pastures as yearlings and during pregnancy and on improved natural pastures (Lolium multiflorum L., Trifolium repens cv. Yi and Lotus corniculatus cv. São Gabriel) during the post-calving period and breeding season; on natural pastures with protein supplement at yearling, on natural pastures during pregnancy, and on improved natural pasture during post-calving period and breeding season. Cows did not differ on body weight, but from calving to the beginning of breeding season, cows on improved natural pastures presented higher weight gain than those on natural pastures (0.203 vs. 0.109 kg/day). Cows in post-calving on natural pastures lost 1.0 point of body condition score during mating, determinant of the lowest pregnancy rate and later conception in relation to cows on improved natural pasture. Pregnant cows presented higher body weight (440 vs. 413 kg) and body condition score (4.14 vs. 3.66 points) than open cows at the end of the breeding season.

Esta pesquisa foi realizada com os objetivos de implementar um sistema de indicadores que permita uma visão do desempenho em todos os níveis da empresa e avaliar seu desempenho global por meio de um indicador geral consolidado. Na empresa estudada, foram identificados três ramos de negócio (agricultura, pecuária e vitivinicultura) mais o setor administrativo, para os quais foram determinados objetivos estratégicos. Sequencialmente, foram mapeados os macroprocessos que compõem cada uma das atividades do negócio, num total de 14, e os indicadores críticos de desempenho para o atendimento dos objetivos, perfazendo um total de 50 indicadores, cujas metas foram definidas pela equipe de gestores. É possível a construção de indicadores consolidados utilizando o Analytic Hierarchy Process, o qual permite ponderação da importância relativa dos indicadores em cada nível hierárquico, ou seja, macroprocessos, atividades e desempenho global da empresa em busca dos objetivos traçados.

The objective of this study was to implement an indicator system that allows an overview of the performance at all levels of the company and to evaluate its overall performance using a consolidate general indicator. In the company studied, three business sectors were identified (crops, beef cattle production and viticulture) in addition to management sector, to which strategic objectives were determined. After that, it was mapped the macroprocesses that compose each business activity, a total of 14, and the critical indicators of performance to achieve the objectives, making up 50 indicators whose objectives were definied by the management team. It is possible to build consolidated indicators using the Analytic Hierarchy Process method, which allows weighing the relative importance of the indicators at each hierarchical level, that is, macroprocesses, activities and overall company performance for the achievement of the established goals.

Avaliou-se o desenvolvimento de bezerros de corte submetidos a duas idades de desmame: precoce, em média com 80 dias de idade; convencional, em média com 152 dias de idade. Foram utilizados 105 bezerros Braford, nascidos nos anos de 2004 e 2005. Após o desmame, os bezerros foram mantidos em pastagens cultivadas de milheto (Pennisetum americanum) no primeiro e segundo verão e, no inverno/primavera, de aveia e azevém (Avena strigosa Schreb + Lolium multiflorum Lam). Foram avaliados os pesos corporais, ganhos de pesos médios diários e condição corporal. Houve interação significativa entre idade de desmame e ano para o ganho médio diário, tanto no desmame precoce como no desmame convencional, na pastagem de aveia e na de azevém. No período entre as duas idades de desmame, o ganho médio diário no desmame precoce foi maior em 2004 que em 2005 (0,499 vs 0,468 kg, respectivamente) e no desmame precoce ocorreu maior ganho médio diário em 2005 (0,493 vs 0,631 kg, respectivamente). Na pastagem de aveia e azevém, o ganho médio diário dos animais do desmame precoce em 2004 (0,666 kg) foi menor que em 2005 (0,760 kg), no entanto, não houve diferença entre os anos no caso dos animais do desmame convencional (0,720 e 0,723 kg, respectivamente). Durante os segundos verões, não houve diferença no ganho médio diário dos animais entre os desmames precoce e convencional. O peso dos animais do desmame precoce (158,2 kg) foi superior ao daqueles do desmame convencional (147,7 kg) no início da pastagem de inverno, porém, não diferiu no final. Ao final do verão, quando os novilhos atingiram 15-16 meses de idade, o peso corporal foi similar entre os desmames precoce (340,1 kg e 4,14 pontos) e convencional (332,8 kg e 4,15 pontos). A condição corporal final em 2004 foi maior (4,34) que em 2005 (3,96 pontos). Bezerros desmamados aos 80 dias de idade e alimentados adequadamente têm desempenho semelhante aos desmamados aos 152 dias de idade, atingindo desenvolvimento e acabamento adequados de abate para mercados específicos aos 15-16 meses de idade.

The performance of beef calves submitted to two weaning ages (early weaning, at an average age of 80 days; conventional weaning, at an average age of 152 days) was evaluated. One hundred and five Braford calves born in 2004 and 2005, after weaning, were kept on pastures cultivated with pearl millet (Pennisetum americanum) in the first and second summer and, in winter/spring, they were kept on pastures with oat and ryegrass (Avena strigosa Schreb + Lolium multiflorum Lam). Body weight (BW), average daily weight gain (ADWG) and body condition (BC) were evaluated. There was a significant interaction among age at weaning and year for daily weight gain for early weaning as well as for conventional weaning on oat and ryegrass pastures. In the period between the two weaning ages, the daily weight gain in early weaning was higher in 2004 than in 2005 (0.499 vs 0.468 kg, respectively) and for early weaning, higher daily weight gain occurred in 2005 (0.493 vs. 0.631 kg, respectively). On oat and ryegrass pasture, average daily weight gain for early weaned animals in 2004 (0.666 kg) was lower than in 2005 (0.760 kg), however, there was no difference among years for conventional weaned animals (0.720 and 0.723 kg, respectively). During second summer periods, average daily weight gain did not differ among early and conventional weaned animals. Weight of early weaned animals (158.2 kg) was higher than conventional weaned animals (147.7 kg) in the beginning of winter grazing; however, it did not differ at the end. In the end of the summer, when calves were 15-16 months of age, body weight was similar among early weaned (340.1 and 4.14 points) and conventional (332.8 kg and 4.15 points) weaned animals. Final body condition, in 2004, was higher (4.34) than in 2005 (3.96 points). Calves weaned at 80 days of age and adequately fed present similar development as those weaned at 152 days of age, achieving development and finishing conditions to be slaughtered for specific markets at 15-16 months of age.

Este trabalho foi realizado com o objetivo de identificar as demandas dos clientes de uma empresa produtora de touros de corte no Rio Grande do Sul por meio de uma metodologia adaptada da ferramenta desdobramento da função qualidade. A adaptação consistiu no fato de que as matrizes são tratadas de forma unificada entre o produto e os serviços, devido à percepção do elevado nível de inter-relacionamento entre esses componentes no negócio. Os resultados evidenciaram que os clientes priorizam as características relacionadas ao produto, especialmente o valor genético dos touros. Os itens de serviços também se destacaram, podendo configurar-se como uma oportunidade de diferenciação entre as empresas fornecedoras. O perfil dos clientes influenciou a ordem de priorização, uma vez que os produtores sem assistência técnica priorizaram as características de desempenho às genéticas, ao contrário dos assistidos e dos consultores técnicos. No tamanho da propriedade, só houve alterações na ordem de priorização no nível terciário das demandas. A adaptação da metodologia para a análise conjunta interferiu no resultado, principalmente na priorização dos serviços. O estudo contribuiu com a formatação de um modelo de uso do desdobramento da função qualidade na produção de touros, auxiliando na identificação da qualidade demandada e no seu nível de priorização para a população e empresa pesquisada, podendo ser utilizado em outros estudos para o produto touro.

The objective of this study is to identify demands of customers of a sire-producing company in Rio Grande do Sul, Brazil, by using a methodology adapted from quality function deployment tool. The adaptation consisted on the fact that matrices are treated in an unified manner among product and services due to the high perception of inter-relationship among these business components. The results evidenced that clients priorize traits related to the product, especially genetic value of the bulls. Service items were also highlighted, and they may be presented as an opportunity of differentiation among suppliers. Customer profile influenced priority order inasmuch as farmers with no technical services prioritized performance traits over genetic traits, opposing to those who were assisted and to technical consultants. Concerning to farm size, there were changes only in the tertiary level of the priority order of the demands. The adaptation of the methodology for joint analysis interfered in the results, especially in service prioritization. This study contributed to formatting a model for using quality function deployment in sire production, helping to identify quality demands and its priority levels for the population and researched company, and it may be used in further studies on the product beef sires.

Durante os períodos pré e pós-parto, foi avaliada a influência de sistemas forrageiros no desempenho reprodutivo de vacas primíparas: pastagem natural nos períodos pré e pós-parto; pastagem natural no pré-parto e pastagem melhorada no pós-parto; pastagem melhorada no pré-parto e pastagem natural no pós-parto; pastagem melhorada nos períodos pré e pós-parto. Os menores pesos e condições corporais foram observados nas vacas mantidas em pastagem natural no pré-parto, (384,3 kg e 3,31; 391,4 kg e 3,60), seguidas daquelas em pastagem melhorada no pré-parto e natural no pós-parto (424,4 kg e 3,60); e, por ultimo, das vacas em pastagem melhorada no pré e pós- parto (421,2 kg e 3,59). As vacas em pastagem melhorada no pré e pós-parto tiveram maior peso e condição corporal ao início do acasalamento (442,1 kg e 3,76), maior taxa de prenhez (82,3%) e emprenharam mais cedo. Os sistemas com pastagem natural no pré-parto e melhorada no pós-parto e aquele com pastagem melhorada no pré-parto e natural no pós-parto não diferiram quanto a peso ao início do acasalamento (417,2 e 409,8 kg) e taxa de prenhez (65,8 e 62,8%), respectivamente. Entretanto, as vacas em pastagem natural no pré-parto e melhorada no pós-parto emprenharam mais cedo. As vacas mantidas em pastagem natural tiveram o menor peso ao início do acasalamento (391,2 kg), a menor taxa de prenhez (52,7%) e emprenharam mais tarde. Pastagens melhoradas no pré e pós-parto melhoraram os pesos e as condições corporais ao parto e ao início da reprodução, possibilitando alto desempenho reprodutivo.

During pre and post calving periods, it was evaluated the influence of the following forage systems on reproductive performance of primiparous cows: natural pasture during pre and post-calving periods; natural pastures during pre-calving period and improved pastures during post-calving period; improved pastures during pre-calving and natural pasture during post-calving; improved pasture during pre- and post-calving periods. The lowest body weights and body condition scores were observed on cows kept on natural pastures pre-calving (384.3 kg and 3.31; 391.4 kg and 3.60), followed by those on improved pastures during pre-calving and on natural pasture during post-calving period (424.4 kg and 3.60), finally, cows on improved pasture during pre- and post-calving period (421.2 kg and 3.59). Cows on improved pastures pre and post-calving showed higher body weight and body condition score in the beginning of the breeding season (442.1 kg and 3.76), higher pregnancy rate (82.3%) and they conceived earlier. Natural system during pre-calving and improved on post-calving and that with improved pasture in pre-calving and natural in post-calving did not differ on weight at the beginning of breeding season (417.2 and 409.8 kg) and on pregnancy rate (65.8 and 62.8%), respectively. However, cows on natural pasture in pre-calving and on improved pasture in post-calving conceived earlier. Cows on natural pastures showed lower weight in the beginning of breeding season (391.2 kg), the lowest pregnancy rate (52.7%), and they conceived later. Cows maintained on improved pastures pre- and post-calving improved weight and body condition score at calving and beginning of the breeding season making high reproductive performance possible.

A produtividade e a eficiência de vacas de corte submetidas ao desmame de seus bezerros aos 76 dias (desmame precoce) ou aos 148 dias (desmame à idade convencional) pós-parto foram medidas durante três anos consecutivos. Avaliaram-se as taxas de prenhez, natalidade e desmama, o ganho de peso de bezerros e de vacas do parto ao desmame convencional, o peso à desmama convencional de bezerros e vacas, a produção de bezerros desmamados por vaca e o índice de produção de bezerros. A taxa de prenhez no rebanho submetido ao desmame precoce (86,4%) foi superior à do desmame convencional (55,5%). Vacas do desmame precoce tiveram maiores taxas natalidade e de desmame em comparação às do desmame convencional (83,6 e 83,6% vs 47,5 e 44,5%, respectivamente), além de maior produção de bezerros (183 vs. 114). As vacas do desmame precoce produziram 60,5% a mais de bezerros que as vacas do desmame convencional. Os bezerros de desmame convencional foram os que ganharam mais peso desde o nascimento até o desmame (97,9 vs 83,4 kg, respectivamente). As vacas do desmame precoce tiveram maior ganho de peso do parto até o desmame (42,5 vs 18,7 kg, respectivamente) e foram mais eficientes quanto ao índice de produção de bezerros (eficiência dos rebanhos). Na média dos três anos, o desmame precoce dos bezerros permite às vacas maiores taxas de prenhez e de desmame, além de maior índice de quilos de bezerro produzido em relação ao desmame em idade convencional.

It was aimed in this work to evaluate the productivity and efficiency of beef cows submitted to weaning of their calves at 76 days (early weaning) or at 148 days (weaning at conventional age) after calving during three consecutive years. It was evaluated pregnancy rate, birth and weaning, gain weight of the calves and cows at conventional weaning, weight at conventional weaning of calves and cows, production of weaned calves per cow and calf production index. Pregnancy rate in the herd submitted to early weaning (86.34%) was higher than in the conventional weaning (55.5%). Early weaning cows showed higher birth and weaning rates when compared to conventional weaning (83.6 and 83.6% vs. 47.5 and 44.5%, respectively) besides a higher production of calves (183 vs. 114). Early weaning cows produced 60.5% more calves than the conventional weaning cows. Conventional weaning calves gained more weight from birth to weaning (97.9 vs. 83.4 kg, respectively). Early weaning cows had more weight gain from calving to weaning (42.5 vs. 18.7 kg, respectively), and regarded to calf production index, they were more efficient (efficiency of the herds). At the average of the three years, the early weaning of the calves allows higher calving rates and weaning to the cows, in addition to a higher index of calf kilogram index produced in relation to weaning at conventional age.