Navegando por Autor "Tedeschi, Luis Orlindo"
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Item Development of a mathematical model to study the impacts of production and management policies on the herd dynamics and profitability of dairy goats(Agricultural Systems, 2009-07) Guimarães, Vinícius Pereira; Rodrigues, Marcelo Teixeira; Tedeschi, Luis OrlindoThe reduction in goat milk production and the competitiveness of more profitable activities have increased the adoption of measures to enhance goat milk and meat around the world. A simulation model was built to evaluate the dynamics of a dairy goat herd under different scenarios of production. A System Dynamics approach was used to identify management policies that could affect the behaviour of the herd over 10 years of simulation using data from a dairy goat herd in Brazil. The impact of reproductive and mortality rates, one or two annual reproductive cycles on production, and economic health of dairy goats on changes in the herd dynamics were evaluated. Simulations indicated that small changes in reproduction and mortality rates and milk price can considerably affect the dynamics of the herd as well as the financial health of the production system. The interferences created to visualize the effects were not immediately realized because of intrinsic delays in the system. The comparison of models with one or two breeding seasons indicated that the latter was considerably more profitable and had a faster turnover. It was also found that the two breeding season had a greater capacity to support reduction in milk price that could generate financial instability in the production system. It was concluded that mathematical models can be used to predict impacts in management policies on herd dynamics and sensitivity to support the dairy goat activity showing its viability as an agricultural activity that can contribute to the production and incomes in small farms.Item Evaluation of mathematical models to describe growth of grazing young bulls(Revista Brasileira de Zootecnia, 2011-07-08) Fernandes, Henrique Jorge; Tedeschi, Luis Orlindo; Paulino, Mário Fonseca; Detmann, Edenio; Paiva, Luisa Melville; Valadares Filho, Sebastião de Campos; Silva, Aline Gomes da; Azevêdo, José Augusto GomesThe objective of this study was to evaluate the use of different mathematical models to describe growth of grazing beef cattle. Data of 20 Nellore bulls with initial weight of 129±28.1 kg and final weight of 405±62.0 kg were used. The animals were randomly divided into four plots and placed on B. decumbens Stapf pastures. Three plots received concentrate supplement with different protein profiles and the fourth plot received only mineral supplement. Animals were weighed every 28 days to design growth curve of full body weight. Five mathematical models were evaluated to describe animal growth: Multiphase, Linear, Logarithmic, Gompertz and Logistic models. Assessment of adequacy of the models was performed by using coefficient of determination, simultaneous F-test for identity of parameters, concordance correlation coefficient, root of the mean square error of prediction and partition of the mean square error of prediction. The analysis of the pairwise mean square error of prediction and the delta Akaike's information criterion were used to compare the models for accuracy and precision. Evaluation of all the tested models showed that all of them were able to predict variability among animals. However, Gompertz, Logarithmic and Logistic models created individual predictions that were not satisfactory. Models differed from each other concerning accuracy and precision; the best were in the following order: Multiphase, Linear, Gompertz, Logarithmic and Logistic. The Multiphase model was more efficient than the others for description of grazing beef cattle growth.Item The geometry of the lactation curve based on Wood’s equation: a two-step prediction(Brazilian Journal of Animal Science, 2020-10-08) Oliveira, Jhone Gleison de; Sant’Anna, Daniel Furtado Dardengo; Lourenço, Matheus Celestiano; Tavares, Davi Simões; Rodrigues, Marcelo Teixeira; Tedeschi, Luis Orlindo; Vieira, Ricardo Augusto MendonçaLactation records from cows of the southwestern Paraná state, Brazil, form the dataset of this study. We applied the information-theoretic approach to evaluate the ability of the nonlinear Wood, Brody, Dijkstra, and Gamma functions to fit to these data by employing a two-step technique based on nonlinear mixed-effects models and generalized linear mixed-effects models. Wood’s equation was fitted with the combination of a first-order autoregressive correlation structure and a variance function to account for heteroscedasticity. This version was the best choice to mimic lactation records. Some geometric attributes of Wood’s model were deduced, mainly the ascending specific rate from parturition to peak milk yield and the descending specific rate as a measure of the lactation persistence of the milk yield at peak production. Breed and parity order of the cows were assumed as fixed effects to obtain a reliable model fitting process. Regardless of breed, first-order parity cows had greater persistency than their older counterparts, and the greater the ascending rate of milk yield from the parturition to the peak, the sharper the decrease in milk yield post-peak; therefore, the rates (absolute values) of ascending and descending phases correlated positively. Nonetheless, the actual estimated values of the descending phase rates are negative. Wood’s equation was flexible enough to mimic either concave- and convex-shaped lactation profiles. The correlations between both peak milk yield and random estimates for β with total milk yield per lactation were positive. However, peak milk yield might not be the only variable used for ranking cows; the total milk yield integrates all information of the lactation profile through the estimated parameters of Wood’s equationItem Net requirements of calcium, magnesium, sodium, phosphorus, and potassium for growth of Nellore × Red Angus bulls, steers, and heifers(Livestock Science, 2009-09) Valadares Filho, Sebastião de Campos; Chizzotti, Mario Luiz; Tedeschi, Luis Orlindo; Paulino, Pedro Veiga Rodrigues; Paulino, Mário Fonseca; Valadares, Rilene Ferreira Diniz; Amaral, Paloma; Benedeti, Pedro Del Bianco; Rodrigues, Tainnah Ikegami; Fonseca, Mozart AlvesA comparative slaughter trial was conducted to assess the net requirements for gain of Ca, P, Na, K and Mg of bulls, steers and heifers of Nellore and Red Angus crossbreds. Twenty seven F1 Nellore and Red Angus crossbred calves (9 steers, 9 bulls, and 9 heifers), averaging 274 kg BW, were used. At the beginning of the trial, three animals from each gender were slaughtered to determine the initial body composition. The remaining 18 animals (3 animals of each gender) were randomly assigned to two treatments: fed 0.75 or 1.5% of BW of concentrate. The diets were based on corn silage and were isonitrogenous (2% N, DM). After three growing periods of 28 d, all animals were slaughtered. The cleaned gastrointestinal tract, organs, carcass, head, hide, tail, feet, and tissues were weighed to determine the empty BW (EBW). These parts were ground separately and subsampled for chemical analyses. The log of the contents of each mineral in the empty body was regressed on the log of the EBW to estimate the net requirement for each mineral per kg of empty body gain (EBG). There were no differences (P > 0.05) in the net requirements for growth of all macrominerals among genders. The equations of the pooled data of the net requirements for growth (g/kg EBG) were: 332.6 × EBW ^− 0.6367 for Ca, 112.1 × EBW ^− 0.5615 for P, 10.85 × EBW ^− 0.3992 for Na, 4.01 × EBW ^− 0.153 for K, and 3.589 × EBW ^− 0.462 for Mg. Our findings indicated that retained Ca and retained P were poorly related to the retained protein.Item Níveis de inclusão e tempo de exposição da cana-de-açúcar ao óxido de cálcio sobre parâmetros digestivos e o desempenho de novilhas Nelore(Revista Brasileira de Zootecnia, 2010-03-09) Pina, Douglas dos Santos; Tedeschi, Luis Orlindo; Barbosa, Analívia Martins; Azevêdo, José Augusto Gomes; Valadares, Rilene Ferreira Diniz; Souza, Natália Krish de Paiva; Fonseca, Mozart Alves; Valadares Filho, Sebastião de CamposAvaliou-se nesta pesquisa o efeito da inclusão de óxido de cálcio (cal) e dos tempos de exposição da cana-de-açúcar à cal sobre o desempenho de novilhas Nelore, a digestibilidade dos componentes da dieta e a síntese de proteína microbiana ruminal (PBMic) e comparou-se o dióxido de titânio ao óxido crômico para estimar o consumo individual de concentrado. Utilizaram-se 30 fêmeas Nelore com aproximadamente 24 meses de idade e pesos médios de 285 ± 31 kg, alojadas em seis baias coletivas. As dietas foram arranjadas em esquema fatorial 3 × 2, com três níveis de cal (0; 0,5 ou 1% na matéria natural) e dois tempos de exposição (zero e três dias). Os tempos de exposição da cana-de-açúcar à cal não tiveram efeitos sobre as quantidades de nitrogênio microbiano, os consumos de matéria seca (MS) e orgânica (MO), proteína bruta (PB), total de nutrientes digestíveis e o ganho médio diário, porém influenciaram os consumos de extrato etéreo (EE), fibra em detergente neutro corrigida para cinzas e PB (FDNcp) e carboidratos não-fibrosos (CNF). Os níveis de cal influenciaram de forma linear decrescente os consumos de MO, FDNcp, CNF e NDT, e o GMD. Todavia, não foram observados efeitos dos indicadores (dióxido de titânio e óxido crômico) nem interações do tempo de exposição e do nível de cal sobre os consumos de MS, MO, PB, EE, FDNcp, CNF e NDT. Interações significativas do tempo de exposição e do nível de inclusão de cal foram observadas para as digestibilidades aparentes totais da MS, MO, PB e FDN e para o teor de NDT. Os indicadores dióxido de titânio e óxido crômico são igualmente efetivos para estimar os consumos individuais de concentrado de bovinos alimentados em grupo. O fornecimento de cana-de-açúcar armazenada durante três dias sem cal não altera o desempenho de novilhas em crescimento.