Resumo: Este estudo avaliou o efeito dos níveis de energia (NDT) e proteína bruta (PB) consumidos por vacas de corte durante a gestação sobre o peso dos fetos aos quatro (PF4) e oito meses (PF8) e dos bezerros ao nascimento (PN); sobre o peso pós-natal aos 60 (PV60), 100 (PV100), 180 (PV180) e 205 (PV205) dias de vida; sobre o peso, a idade, o ganho médio diário (GMD), a área de olho de lombo (AOL), o marmoreio e a espessura de gordura (EG) ao abate. Foi conduzida uma revisão sistemática da literatura e uma metanálise (MA) a partir de duas bases de dados eletrônicas (Scopus e Web of Science). A MA para efeitos randomizados foi realizada para cada resultado com as médias do grupo controle e tratado, conduzida com os níveis de NDT e PB em relação às exigências das vacas (NRC, 1996). Foram avaliadas 46 publicações, correspondentes a 50 estudos, 135 ensaios e 9.379 animais. Não houve efeito do consumo de PB e NDT pelas vacas sobre o PF4. Quando as vacas consumiram PB e NDT em níveis iguais às suas exigências, no primeiro (1TRI) e segundo trimestre (2TRI) da gestação, houve redução no PF8 (DM= 2,236kg; P<0,001). O PN reduziu nos bezerros filhos de vacas que consumiram PB igual ou acima das suas exigências no terceiro trimestre da gestação (3TRI) (DM= -2,954kg; P<0,001 e DM= -0,453kg; P=0,045, respectivamente) ou 140% das exigências de NDT (DM= -2,709; P = 0,001). Quando o consumo de NDT foi igual à recomendação do NRC (1996), observou-se aumento de 2,029kg no PN dos bezerros (P<0,001). O PV60 foi inferior quando as vacas consumiram PB (DM= -1,923kg; P<0,001) e NDT (DM= -1,676kg; P<0,001) acima de suas exigências no 3TRI. O PV205 foi 3,122kg inferior (P<0,001) quando as vacas consumiram até 120% de NDT no 2TRI e 3TRI. Os novilhos cujas mães consumiram PB e NDT acima de suas demandas, no 3TRI, foram abatidos 5,5 dias antes (P= 0,015) que os demais. O GMD, o marmoreio e a EG foram superiores em vacas que consumiram NDT e PB acima das suas exigências no 3TRI (P<0,05). Em síntese, os níveis de PB e NDT, consumidos pelas vacas, acima das recomendações do NRC, estão negativamente relacionados com o desenvolvimento dos fetos e com o PN, sendo que esse efeito permanece até os 205 dias de idade. Por outro lado, na fase de terminação o excesso de PB e NDT passa a contribuir com o GMD, o marmoreio e a EG da carcaça das progênies. / Abstract: This study evaluated the effect of total digestible nutrients (TDN) and crude protein (CP) levels, consumed by cows during gestation, on fetal and postnatal development and on carcass traits. We conducted a systematic review of the literature and a metanalysis (MA) on two electronic databases (Scopus and Web of Science). Inclusion criteria were complete studies using pregnant beef cows receiving different diets that analysed fetus weight at four (FW4) and eight months (FW8), and birth weight of calves (BW); postnatal weight at 60 days (PW60), 100 days (PW100), 180 days (PW180) and 205 days (PW205) of life; and on weight, age, mean daily gain (ADG), loin eye area (LEA), marbling and fat thickness (FT) at slaughter. Random effect MA were conducted for each indicator separately with the mean of control and treated group. The analysis was conducted with the TDN and CP levels in relation to cows’ requirements (NRC, 1996). We evaluated 46 publications, reporting 50 studies, 135 trials and 9,379 animals. The CP and TDN level consumed by pregnant cows showed no change on FW4. Cows that consumed CP and TDN in a level equal to their requirements, in the first (1TRI) and second trimester (2TRI) of gestation, showed a reduction in FW8 (DM= 2,236kg; P<0.001). The BW reduced in cows that consumed CP equal to or above their requirements in the third trimester of gestation (3TRI) (DM= -2.954kg, P<0.001 and DM= -0,453kg, P=0.045, respectively), or 140% of TDN requirements (DM= -2.709, P=0.001). The calves of cows that consumed TDN equal to NRC (1996) requirements, increased the BW in 2,029kg (P<0.001). The PW60 was lower when cows consumed CP (DM= -1.923kg; P<0.001) and TDN (DM= -1.676kg; P<0.001) above their requirements in the 3TRI. The PW205 was lower (DM= 3.12kg; P<0.001) when cows consumed 120% of TDN in the 2TRI and 3TRI. Steers whose mothers consumed CP and TDN above their requirements in the 3TRI were slaughtered 5.5 days earlier (P= 0.015) than the others. The ADG, marbling and FT were higher when cows consumed TDN and CP above the NRC (1996) requirements in the 3TRI (P<0.05). In summary, the CP and TDN levels, consumed by cows, above the NRC recommendations, are negatively associated to fetal development and birth calf weight, and this effect remains until 205 days of age. Alternatively, in the feeder phase, CP and TDN in excess contribute to average daily gain, marbling and fat thickness of the progeny.

Este trabalho propõe uma metodologia para auxiliar o empresário rural no momento de decidir qual a tecnologia menos arriscada para aumentar a taxa de prenhez em seu sistema de produção de bezerros. Para tanto, foram avaliadas as percepções de especialistas quanto a sete fatores a partir dos quais foi desenvolvida uma equação para calcular este risco. Tais parâmetros e suas definições foram apresentados em questionários aos 18 especialistas, selecionados por amostragem não probabilística. Neste documento foram listadas 32 tecnologias, avaliadas de acordo com os parâmetros conforme a escala Likert de cinco níveis. Foram utilizados os parâmetros relacionados diretamente ao risco das tecnologias, atribuindo-se um valor conforme a nota dos especialistas, de forma a ajusta-las conforme sua influência no risco, se positiva ou negativa. Não houve diferença significativa entre o risco calculado e o estimado pelos especialistas, além de ambos apresentarem alta correlação, validando esta metodologia. As tecnologias de insumo se apresentaram mais arriscadas, indicando custo, complexidade operacional e conhecimento técnico mais elevados do que as de processo. Da mesma forma, as tecnologias de manejo demonstraram menor risco em relação às nutricionais e reprodutivas, que não apresentaram diferença entre si. As tecnologias consideradas inovadoras foram mais arriscadas do que as consolidadas, apresentando todos os parâmetros mais elevados, com exceção da flexibilidade. Dessa forma, a metodologia desenvolvida foi capaz de determinar o risco das tecnologias, obtendo resultados semelhantes às percepções dos especialistas. / This study proposes a methodology to assist the farmers in deciding which technology is less risky to reduce the inefficiencies of their cow-calf production. Thus, were evaluated the perceptions of experts about seven factors predetermined from which were developed a formula to calculate this risk. These parameters and their definitions were reported in questionnaires to 18 experts, selected by nonprobability sampling. This document listed 32 technologies evaluated according to the parameters in the Likert scale of five levels. Were used the parameters directly related to the risk, assigning a value to the experts notes, in order to adjust these as their influence on the risk, whether positive or negative. There was no significant difference between the calculated and the estimated risks; they also had a high correlation, validating this methodology. The innovative technologies were more risky, indicating cost, operational complexity and technical knowledge higher than the process technologies. Likewise, the management technologies showed less risk than the nutritional and reproductive ones, which appear to have no difference among them. The innovative technologies were riskier than the consolidated ones, with all the standards higher, with the exception of flexibility. The methodology was able to determine the risk of technologies, obtaining similar results to the perceptions of the experts.

Call number: LD2668 .T4 1986 H54 / Master of Science / Agricultural Economics

Das Ziel der Untersuchungen bestand darin, die Auswirkungen verschiedener Kälberaufzuchtverfahren, die sich hinsichtlich des Faktors 'Anwesenheit der Mutter' unterschieden, auf die Entwicklung des Sozialverhaltens in der Ontogenese zu bestimmen. Mit den Ergebnissen dieser Untersuchungen sollen die tierseitigen Anforderungen der Kälber an die Haltungssysteme in Hinblick auf die soziale Umwelt deutlicher formuliert werden. Von Mai 1994 bis zum Oktober 1996 wurden zwei Rindergruppen der Rassenkreuzung Schwarzbuntes Milchrind (SMR) x Salers von der Geburt an bis zur Phase der eigenen Reproduktion beobachtet. Gegenstand der Untersuchungen war die ethologische Analyse verschiedener Verhaltensweisen, vor allem des Sozialverhaltens. Die Saugkälber hatten in den ersten acht Lebensmonaten vorwiegend Sozialkontakte mit ihren Müttern, weniger mit den gleichaltrigen Gruppenmitgliedern. Spielerische Kontakte zwischen den Kälbern bezogen sich meist auf Bewegungsspiele und spielerisches Hornen. Rangauseinandersetzungen fanden erst nach dem Absetzen statt. Die Tränkkälber hatten insgesamt weniger Kontakte untereinander, beleckten sich allerdings häufiger. Rangauseinandersetzungen fanden bereits ab dem dritten Lebensmonat statt und führten zur Bildung einer vorläufigen Rangfolge, die von den ältesten und schwersten Tieren dominiert wurde. Gegenseitiges Besaugen wurde oft beobachtet. Es trat sehr häufig während der Haltung am Tränkautomaten auf und konnte bis zum 22. Lebensmonat beobachtet werden. Die Anzahl der Sozialkontakte zu gleichaltrigen Tieren war in der Jungrind- Phase in beiden Gruppen weitgehend gleich. In der Jungkuh- Phase hatten die Jungkühe (S) untereinander signifikant mehr soziale Kontakte, knüpften zu ihren Nachkommen mehr Kontakte und verbrachten auch signifikant mehr Zeit gemeinsam mit ihnen als die Jungkühe (T). Verhaltensrhythmisch traten über den Lichttag hinweg während des gesamten Untersuchungszeitraumes Unterschiede zwischen den Gruppen auf. Zwar glichen sich beide Gruppen in ihrem Tagesrhythmus mit zunehmendem Alter an, aber nicht vollständig. Unterschiede gab es auch bei den Tagessummen für das Fressen, Liegen und Stehen. Schlußfolgernd zeigt sich, daß eine Aufzucht in altersstrukturierten Gruppen wichtige kalb- und kuhseitige Sozialbedürfnisse erfüllt und die sozialen Potenzen adulter Gruppenmitglieder in die Aufzucht einbezieht. Den Jungtieren werden somit Lernprozesse ermöglicht, die von langfristiger Bedeutung sind und sich bei der Aufzucht ihrer eigenen Nachkommen positiv auswirken. Die Umsetzung dieses Grundprinzips im Zuge der Weiterentwicklung der Aufzuchtverfahren kann deren biologische Qualität deutlich verbessern und gestaltet die Erfüllung wesentlicher Anforderungen einer art- und altersgerechten Kälberhaltung. / The aim of the investigation was to determine effects of different calf-rearing conditions with regard to the factor of the presence of the dam on the development of the social behavior during the ontogeny. The results of these investigations should express the animal requirements of the calves to the different keeping systems in view of the social environment. The study was carried out in the time between April 1994 and October 1996, until the age of their own reproduction. Two groups of female calves , containing 11 animals (suckling calves) and 10 animals (watering calves) were observed. The first group was raised by dams (suckling calves). The second one was raised without any contacts to the dams (watering calves). Suckling calves exhibited social contacts preferably to their own mother rather than to the other calves of the group. In most cases the contacts between the calves consisted of play runnings and horning. These calves established the rank order after weaning, i. e. after the ninth month. In the time before weaning the social interactions of the suckling calves exceeded those of the watering calves. Mutual suckling behaviour took place only in the group of the watering calves. Social rank order disputes among calves of the automatically fed group already started in their fourth month. The establishment of ranks was principally determined by age and weight. Mutual suckling behaviour were often observed. It was very often during the time as they were fed by the automatic liquid feeder and it was observed till the 22nd month. The number of social contacts to peers of calves in the age between the 9th and 23rd month was nearly the same. Those mothers that had been raised as suckling calves had more interactions with their own offspring and spent more time with them in comparison to the automatically fed group. The rhythm of behavior of the observation (lightly) day was different between the groups over the full observation period. At the end of the observations in October 1996 the rhythm of behaviour was nearly the same, but not for all specifics. Also, there were differences in the daily sums of feeding, laying and standing. The rearing of calves in groups with their dams fulfills the special social needs of cows and calves. The social potencies of adults improve the rearing of the calves. The young's get the possibility to learn from the adults. This possibility is very important and has a positive influence for rearing of their own offspring. This basic principal is important for the development of rearing methods, for a better biological quality and fulfills the specific requirements of calf-rearing.

Using the E. coli vaccine as a case study, this thesis examines the factors affecting the adoption of technologies with positive spillover (externality) effects related to food safety. Positive spillovers occur when the benefits from a technological innovation extend beyond the firm (farm) adopting the technology or they do not flow to the adopter. If there are insufficient incentives for the firm to adopt the new technology, adoption levels are sub-optimal, resulting in forgone benefits to society. These benefits include the avoidance of potential health costs, productivity loss and premature death costs as a result to exposure to E. coli O157:H7. Therefore, if the market incentives to adopt the technology are strengthened, adoption levels of the technology could reach socially optimal levels resulting in an improvement in food safety. This has been the case in the Canadian cattle industry, where the uptake of the E. coli vaccine by cow-calf producers has been very low. As such, a number of potential incentives to increase adoption of the vaccine were identified and assessed through a survey of cow-calf producers on the Prairies. Data from the survey were analyzed using a stated preference methodology, Best-Worst Scaling, and Latent Class cluster analysis. A Binary Probit Model was also used to examine the factors affecting willingness to adopt the vaccine. The results suggest that a significant number of producers were not aware of the existence of the E. coli vaccine. In addition, producers were most likely to be influenced in their adoption decisions by market/supply chain oriented incentives and government intervention incentives in the form of subsidies. On the other hand, incentives that were least likely to influence cow-calf producers’ decisions to adopt included government intervention through recommending use of vaccine and neighbours (other cow-calf producers) adopting the vaccine. The Latent Class cluster analysis revealed the existence of three unique producer clusters with different attitudes towards these incentives. Several socio-demographic variables and individual characteristics utilized in the Probit analysis were found to be determinants of a producer’s willingness to adopt an E. coli vaccine. The implications of this research are such that producer education and awareness campaigns may be utilized as tools for disseminating information on food safety technologies such as the E. coli vaccine. Furthermore, the market/supply chain incentives may be used to form potential market-based solutions to address the current low adoption rates. The existence of three unique producer clusters suggest that a one-size fits all strategy to encourage the adoption of the E. coli vaccine might be difficult to implement and thus a more targeted approach may be a feasible alternative.

The Salado region of Argentina covers 9.5 million ha, is located in the centre-East of the Buenos Aires Province, and concentrates about 6.9 million cattle. Cow-calf systems are predominant in the area. A simulation model was developed with the purpose of assisting in the design and evaluation of cow-calf systems in the Salado Region. The model was designed to produce long term simulations of the dynamic interactions between herd structure, climatic variation and farm management over periods of several decades using daily weather data, real or simulated. Existing models were used to describe soil, pasture and animal components of the farm, linked with management actions in a dynamic framework. The model was driven by decision rules entered by the user, which allowed the representation of management options that respond to changing farm conditions according to a predetermined policy. An object-oriented approach (OOA) was used in the design and implementation of the model. In the OOA, objects in the real world (e.g. cows, paddocks) are represented as objects in the computer program. The simulation of individual cows and individual paddocks made it possible to distribute feed resources flexibly among animals and provided many other points of flexibility in management strategies. The management strategies simulated in trying to improve cow-calf systems in the Salado region were based on Reserva 6, an experimental cow-calf farm located at the INTA-Balcarce Experimental Station. Every spring-summer, 30% of the area is devoted to make low quality hay (by cutting at high herbage mass), most of which is destined to provide maintenance feed for pregnant adult cows in winter. Cows are kept on a small paddock from weaning (March) to calving (August-September), during which time they receive 6-9kg DM of hay per day. A set of decision rules was developed to represent (on a 100ha farm) the management applied in Reserva 6 and, using this as a base system, a series of simulation experiments was conducted. Firstly, three preliminary experiments, aimed at gaining insight into the system and testing the model, were carried out. In the first of these, the effect of delaying the breeding season 15 and 30 days was analysed. The model was run over 30 consecutive years using a real weather sequence, 1970-2000, from INTA-Balcarce, for each scenario. It was found that, when the appropriate management variables (i.e. weaning and sale dates) were adjusted accordingly, changing the calving period had little effect on the productivity of a cow-calf system. In the second experiment, the dynamic consequences of three different heifer replacement policies on the production outcomes of the system were explored. The policies produced different patterns of oscillations in key farm outputs as a result of periodic behaviour in the age structure of the herd, and the differences between strategies were shown to be dependent on the environmental variability being simulated. The third experiment analysed different policies for hay use during the autumn-winter period, including a control strategy in which no hay was harvested or used. The results suggested that, provided hay was utilized on the farm, the pattern of use did not make much difference to liveweight production. Secondly, the long term performance, in terms of annual liveweight sold, of a range of hay quantity-quality combinations was compared. Each policy was simulated across a range of cow numbers (170 to 350, cows plus heifers in a 100ha farm) and was replicated 20 times. Each replication consisted of 50 years of random weather sampled from the real sequence (1970-2000). The benefit of using hay and the contrasts between the effects of different haymaking strategies on animal outputs increased as the cow numbers increased. The long term analysis suggested that the liveweight production of cow-calf farms, under a calendar-based haymaking policy like that followed in Reserva 6, would be maximized by harvesting 40-50% (but not more) of the total farm area and aiming to harvest hay at medium herbage mass (therefore medium quality). Therefore, the policy currently followed in Reserva 6 of allocating 30% of the farm to haymaking could be considered as conservative, and its productivity might be increased by making hay at lower herbage mass. Thirdly, the possible advantages of incorporating flexibility into the haymaking policy used in Reserva 6 were evaluated using the same experimental design. The results indicated that controlling haymaking in a flexible fashion, basing the decisions of closing, releasing and cutting paddocks on a simple pasture budget, would give the system productive advantages (i.e. increases in productivity and reductions in variability) in relation to a calendar-based approach. Using a flexible haymaking policy allows the manager to make more hay than required for the next winter, providing a buffer for the system. A flexible haymaking policy permitted significantly greater levels of herbage utilization by making large amounts of hay without negative effects on the carrying capacity of the system. A preliminary analysis of risk and costs highlighted major advantages in using hay in cow-calf systems, especially when a flexible approach to haymaking is implemented.

Made available in DSpace on 2014-06-11T19:26:07Z (GMT). No. of bitstreams: 0 Previous issue date: 2008-03-28Bitstream added on 2014-06-13T20:33:50Z : No. of bitstreams: 1 monsalves_fm_me_jabo.pdf: 241550 bytes, checksum: 6693d5417f93dcd0ccd8d78b3166fcd2 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Os objetivos do presente trabalho foram calcular o valor econômico (VE) da característica taxa de prenhez de novilhas precoces e não precoces, em sistemas de produção de carne, com diferentes idades à primeira cobertura (14, 18 e 24 meses), supondo-se diferentes taxas de prenhez (20%, 30% e 40%) e diferentes épocas de descarte, além de, mediante a metodologia do fluxo de genes, avaliar o impacto do melhoramento desta característica em um rebanho, na obtenção de ganho genético para outras características. Foi utilizado um modelo bio-econômico para o cálculo do desempenho do rebanho, das receitas e custos de um sistema de produção utilizando animais da raça Nelore. O VE foi obtido aumentando-se em 1% a taxa de prenhez das novilhas precoces e não precoces, mantendo-se os níveis das demais características constantes. O fluxo gênico foi calculado considerando que a) as fêmeas entraram em reprodução entre 24 e 36 meses de idade e b) as fêmeas entraram em reprodução entre 12 e 24 meses de idade. Expressos com base no rebanho, os VE para a taxa de prenhez de novilhas variou de - R$ 3.652,17 a R$ 7.353,33. O VE foi maior quando as novilhas foram expostas aos touros aos 14 meses, indicando que a adoção desse manejo reprodutivo pode ser financeiramente compensadora. Quando as fêmeas entraram em reprodução entre 12 e 24 meses, a estabilização da proporção dos genes oriundos das fêmeas selecionadas ocorreu após 34 anos, fixando-se em 0,1322, enquanto que, se estas fêmeas tivessem iniciado a reprodução entre 24 e 36 meses, este tempo aumentaria para 44 anos fixando-se em 0,1045... / The aim of the present work was to calculate economic values for the pregnancy rate of Nellore heifers (precocious and not precocious), for cowcalf production systems, starting reproductive life at 14, 18 and 24 months, assuming differents pregnancy rates (20%, 30% and 40%) and differents culling periods. It was also evaluated the impact of improvement of this trait on the genetic and economic gain of other hipothetical traits in a population, using the gene flow methodology. A bio-economic model was used to calculate herd performance, revenues and costs of the beef production system. The economic values (EV) were obtained by increasing in 1% the original pregnancy rate of precocious and not precocious heifers, keeping the level of the other traits constant. The gene flow were calculaded considering the precocious and non precocious heifer production systems. When expressed on herd basis, the EV ranged from - R$ 3652.17 to R$ 7353.33. The highest EV was obtained when heifers were exposed to sires at 14 months of age. This result suggests that the adoption of such reproductive management may be economically compensating. The gene flow study showed that when females entered in reproduction between 12 and 24 months, gene proportions were estabilized after 34 years, fixing in 0.1322. If these females had started reproduction between 24 and 36 months, this estabilization period would be increased to 44 years, fixing in 0.1045. Assuming a genetic-economical superiority for a given trait of interest, expressed in both males and female of R$ 30.00, the genetic economical gain would be obtained in a shorter time and the expected response after one round of selection would have a greater magnitude in the first case (R$ 3.97) when compared with the second case (R$ 3.13)... (Complete abstract, click electronic access below)

Resumo: Os objetivos do presente trabalho foram calcular o valor econômico (VE) da característica taxa de prenhez de novilhas precoces e não precoces, em sistemas de produção de carne, com diferentes idades à primeira cobertura (14, 18 e 24 meses), supondo-se diferentes taxas de prenhez (20%, 30% e 40%) e diferentes épocas de descarte, além de, mediante a metodologia do fluxo de genes, avaliar o impacto do melhoramento desta característica em um rebanho, na obtenção de ganho genético para outras características. Foi utilizado um modelo bio-econômico para o cálculo do desempenho do rebanho, das receitas e custos de um sistema de produção utilizando animais da raça Nelore. O VE foi obtido aumentando-se em 1% a taxa de prenhez das novilhas precoces e não precoces, mantendo-se os níveis das demais características constantes. O fluxo gênico foi calculado considerando que a) as fêmeas entraram em reprodução entre 24 e 36 meses de idade e b) as fêmeas entraram em reprodução entre 12 e 24 meses de idade. Expressos com base no rebanho, os VE para a taxa de prenhez de novilhas variou de - R$ 3.652,17 a R$ 7.353,33. O VE foi maior quando as novilhas foram expostas aos touros aos 14 meses, indicando que a adoção desse manejo reprodutivo pode ser financeiramente compensadora. Quando as fêmeas entraram em reprodução entre 12 e 24 meses, a estabilização da proporção dos genes oriundos das fêmeas selecionadas ocorreu após 34 anos, fixando-se em 0,1322, enquanto que, se estas fêmeas tivessem iniciado a reprodução entre 24 e 36 meses, este tempo aumentaria para 44 anos fixando-se em 0,1045...(Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The aim of the present work was to calculate economic values for the pregnancy rate of Nellore heifers (precocious and not precocious), for cowcalf production systems, starting reproductive life at 14, 18 and 24 months, assuming differents pregnancy rates (20%, 30% and 40%) and differents culling periods. It was also evaluated the impact of improvement of this trait on the genetic and economic gain of other hipothetical traits in a population, using the gene flow methodology. A bio-economic model was used to calculate herd performance, revenues and costs of the beef production system. The economic values (EV) were obtained by increasing in 1% the original pregnancy rate of precocious and not precocious heifers, keeping the level of the other traits constant. The gene flow were calculaded considering the precocious and non precocious heifer production systems. When expressed on herd basis, the EV ranged from - R$ 3652.17 to R$ 7353.33. The highest EV was obtained when heifers were exposed to sires at 14 months of age. This result suggests that the adoption of such reproductive management may be economically compensating. The gene flow study showed that when females entered in reproduction between 12 and 24 months, gene proportions were estabilized after 34 years, fixing in 0.1322. If these females had started reproduction between 24 and 36 months, this estabilization period would be increased to 44 years, fixing in 0.1045. Assuming a genetic-economical superiority for a given trait of interest, expressed in both males and female of R$ 30.00, the genetic economical gain would be obtained in a shorter time and the expected response after one round of selection would have a greater magnitude in the first case (R$ 3.97) when compared with the second case (R$ 3.13)... (Complete abstract, click electronic access below) / Orientadora: Lúcia galvão de Albuquerque / Coorientadora: Vera Lúcia Cardoso / Banca: Henrique Nunes de Oliveira / Banca: Maria Eugênia Zerlotti Mercadante / Mestre

Call number: LD2668 .T4 1986 N44 / Master of Science / Agricultural Economics

O objetivo deste trabalho foi estimar as exigências e a eficiência energética de vacas de corte lactantes e não gestantes, bem como do par vaca/bezerro. Posteriormente foi correlacionada a eficiência do par vaca/bezerro durante a lactação com a eficiência das mesmas vacas durante a terminação. Na fase de lactação os pares vaca/bezerro foram avaliados desde após o nascimento (17±5, d DP) até a desmama (210 d). Após a desmama foi conduzido o ensaio de terminação (67 d) e abate somente das matrizes. Foram avaliadas 10 vacas adultas ½ Caracu x Nelore (CN) e 10 ½ Angus x Nelore (AN), acasaladas com touros Red Angus (RA) e Canchim (CC), respectivamente. Na lactação o oferecimento da dieta (2,30 Mcal EM/kg e 12,4% PB) variou individualmente ao longo do período com objetivo de manter constante o peso das matrizes ao longo da lactação. A mesma dieta foi oferecida a vontade para a progênie. Durante o ensaio de terminação em confinamento a dieta (2,37 Mcal EM/kg e 10,5% PB) foi fornecida à vontade. A ingestão de matéria seca das matrizes foi de 92,4 g MS/kg PM0,75 (CV=3,2%; P=0,458). Vacas AN apresentaram produção de leite corrigida para gordura 12% superior (P<0,05). A concentração energética do leite (Mcal/kg) das vacas CN foi 9,4% superior (P<0,05). A eficiência (Mcal leite/Mcal EM ingerida) não foi diferente. A exigência de energia metabolizável de lactação (EMl) foi maior (P<0,05) para vacas AN em relação as CN, 90,1 e 74,2 (EMl, kcal EMl/kg PM0,75), respectivamente. Bezerros ½CC¼AN¼NE apresentaram ingestão de energia metabolizável (IEM) proveniente do leite 11,3% (P<0,05) superior. Bezerros ½RA¼CR¼NE foram 10,7% mais eficientes (g GP210d/Mcal IEM leite+dieta sólida). Não houve diferença para eficiência dos pares vaca/bezerro, contudo houve considerável variação individual, onde a eficiência média foi 35,3 g GP210d/Mcal IEM par (CV=11,5%). A eficiência do par foi positivamente relacionada ao ganho do bezerro (r=0,79; P<0,01) e negativamente relacionada à IEM do par (r=-0,58; P<0,05). Vacas CN ao abate apresentaram EGS 29% menor, AOL 13% maior e maior proteína no corpo vazio (P<0,05). Vacas AN apresentaram 14,7% maior proporção de órgãos internos relativo ao peso vazio e maior peso dos intestinos (P<0,01). As correlações fenotípicas demonstraram associação entre as eficiência de secreção do leite das vacas nas fase de lactação e de ganho de peso na fase de terminação (r=0,43; P=0,09). A eficiência de secreção de leite das vacas na lactação apresentou correlação com a eficiência do par (r=0,68; P<0,01). O consumo alimentar residual (CAR) das vacas na terminação foi correlacionado com o CAR das vacas em lactação (r=0,53; P<0,05) e com o CAR dos pares (r=0.62; P<0.01). Isso indica que vacas de corte mais eficientes durante a terminação são também mais eficientes no período de cria. / This study estimated the requirements and feed efficiency of non-pregnant lactating beef cows, as well as cow calf pairs. It also correlated the efficiency of the cows and their progeny during lactation to efficiency determined for the same cows in a finishing trial after weaning. In the lactating phase cow calf pairs were evaluated from just after birth (17±5, d) to weaning at 210 d. The finishing trial for the mature cows started after weaning and lasted 67 d after wich cows were slaughtered. Twenty adult cows were evaluated, 10 ½ Caracu x Nelore (CN) and 10 Angus x Nelore, bred to Red Angus (RA) and Canchim (CC) bulls, respectively. During lactation the diet (2.30 Mcal ME/kg and 12.4% CP) was offered in variable amounts to maintain individual live weight and condition score constant. The same diet was offered ad libitum to the calves. During the finishing phase cows were fed ad libitum (2.37 Mcal ME/kg e 10.5% CP). The dry matter feed intake of cows was 92,4 and SD 2,9 g DM/kg BW0,75. AN cows had fat corrected milk 12% higher compared to CN cows (P<0.05). However, milk energy content (Mcal/kg) was 9.4% higher (P<0.05) for CN cows. Efficiency of milk production (Mcal milk/Mcal ME intake) was not different. Metabolizable energy for lactation (MEl) was higher (P<0.05) for AN cows in comparison to CN, respectively 90.1 and 74.2 (MEl, kcal MEl/kg BW0,75). ME milk intake was 11.3% (P<0.05) higher for ½CC¼AN¼NE calves. Rates of gain were not different between calves, but ½RA¼CR¼NE were 10.7% more efficient (g LWG210d/Mcal MEI milk+solid diet). There was no difference in cow calf pairs efficiency, but there was a great individual variability with a mean of 35,31 g and SD of 4,08 g LWG210d/Mcal EM for the pair. Cow/calf pair efficiency was positively related to calf weight gain (r=0.79; P<0.01) and negatively to the pair metabolizable energy intake (r=-0.58; P<0.05). At slaughter CN cows presented backfat thickness 29% lower, longissimus muscle area 13% higher and higher empty body weight protein (P<0,05). AN cows had 14.7% higher relative internal organ weight and higher total intestine weight (P<0.01). The phenotypical correlations between efficiency indexes indicate moderate association between cow efficiency measured during lactation and in a short finishing period after weaning (r=0.43; P=0.09). Exist correlations between cow efficiency lactation and efficiency of the pair (r=0.68; P<0.01). Residual Feed Intake (RFI) during the finishing phase was moderately correlated to the RFI calculated during the lactation period for the cow calf pairs RFI (r=0.62; P<0.01) and the cows (r=0.53; P<0.05) indicated that beef cows more efficient in feed conversion during the finishing phase are more efficient during the lactation period.