Ivo Martins Cezar

Fatores determinantes do desempenho reprodutivo de vacas Nelore na região dos Cerrados do Brasil Central

The objective of this trial was to evaluate the effects of calving order (CO) and body condition score (BCS), scale 1(thin) to 5 (fat), on reproductive performance of 468 Nellore cows (391 multiparous and 77 primiparous) grazing Brachiaria decumbens Stapf at Brazilian Central West (Cerrados region) during four breeding seasons (from 11/1 to 1/31 of the following year). Calving order quadratically affected pregnancy rate (PR) in this trial; PR of CO1 cows was 69% while that of cows from CO5 to CO8 was 90% followed by a gradual decline until 80% PR in C012 cows. Body condition score at weaning also affected PR. For instance, CO1 cows with BCS of 2.0 and 3.5 had 52.7 and 82.5% of PR, respectively. Cows from CO4 to CO8 and BCS of 3.5 showed 96% of PR. CO1 cows that calved late in the season had 37.7% of PR but independent of CO, cows that calved earlier in the calving season had PR greater than 80%. CO1 cows calved 350.12 days after the start of the mating season while multiparous cows calved earlier (328.32 days). CO1 had the longest calving interval (CI) averaging 392.10 days whereas that from CO5 to CO9 cows averaged 365 days. Calving interval was affected by year, CO, number of days spent to calve in the calving season, and body weight change in the mating season. In addition, cows body weight (BWW) and BC at weaning (BCW) were both affected by CO and year. Body weight of calves at weaning increased from CO1 to CO4/CO5 averaging 159 kg for calves from CO1 cows and 169 kg when all CO levels were included. High production and reproductive performance are obtained from CO3 to CO8 and BCS above 3.0 and 3.5 for multiparous and primiparous Nellore cows, respectively.

Análise bioeconômica da introdução de período de monta em sistemas de produção de rebanhos de cria na região do Brasil Central

Four effects related to the establishment of breeding season in production systems were analysed using a bioeconomic simulation model arise from implantation of breeding season in production systems. The effects were: decrease calfs mortality rate (10 to 4%) (effect A); reduction of bulls:cows relation from 1:25 to 1:33 (effect B); increase reproduction of cows (65 to 75%) (effect C); and reduction of herdsman number (effect D). With these effects were five scenery. The rate increase of present net value and brute margin, in relation to scenery without breeding season (scenery one) were respectively 7.64 and 7.68%; 12,91 and 13.84%; 25.36 and 25.25%; and 30.39 and 31.31%. The breeding season implementation provided increase in economical and biological systems efficiency. The reproductive rate growth was the effect with mayor impact in activity. The accumulate effects of breeding season implantation were able to increase gross margin in 31%.

Produtividade e eficiência de vacas Nelore em pastagem de Brachiaria decumbens Stapf nos Cerrados do Brasil Central

The productivity of Nelore cows on Brachiaria decumbens Stapf pasture was measured during four years, in a soil initially improved with limestone and fertilizer and with free access to a mineral mixture. Pregnancy rate (PR), calving rate (CR), weaning rate (WR), calves weaning body weight (BWC), productivity (P = kg of calf/cow) and efficiency (E= P/100 kg of cow) per cow, productivity per area (AP = calves kg/ha), as well as cow body weight and body condition before the calving season (CLW and CBC), at the middle of the mating season (MLW and MBC) and at weaning (WLW and WBC) were evaluated. Mean PR, CR and WR of 87.5, 81.7 and 77.2%, respectively, were observed. Mean LWC of 170 ± 21.89 kg and mean weaning age of 202 ± 16.48 days were observed. Significant effect of calving order (CO) on LWC was detected. Cows between CO3 and CO9 weaned the heaviest calves. Values of 130 kg and 32.19 kg were observed for P and E, respectively, with AP of 192 kg/ha. The CLW and CBC, MLW and MBC, and WLW and WBC were of 471 + 19.67 kg and 4.45 + 0.30; 405 + 21.48 kg and 3.32 + 0.44; 410 + 9.35 and 3.54 + 0.19, respectively. The correlation between body weight and body condition was of 0.66. Nelore cows maintained on a tropical pastures of Brachiaria decumbens Stapf, in an initial fertilized soil, had high reproduction level and productivity. Cows with medium calving order had higher productivity than primiparous and older cows.

A review of bio-economic simulation models of beef production systems and suggestions for methodological development

Abstract This paper sets out to review eight beef production simulation models constructed over the past decade. All eight models are identified as belonging to a class of bioeconomic model referring to beef grazing systems at the level of the farm firm. Aspects given consideration in the review include model objectives, the handling of biological and economic components of beef production systems, risk and management variables and the uses to which the various models have been put. Various aspects of the development and use of such models are discussed, including alternative future courses for methodological development.

Simulação dos efeitos dos preços de produtos e insumos na avaliação econômica de três sistemas alternativos de bovinocultura de cria

By computer simulation the effect of variation in input and output prices on economic returns from three calf production systems was examined. Production of F1 Holstein × Gir calves was more profitable than Nelore × Nelore or F1 Angus × Nelore calf production, primarily because the market value of F1 Holstein × Gir heifer calves was substantially higher than that of any other calf type. Variation in semen price had little impact on economic efficiency of the F1 Holstein × Gir system. In simulations accounting for capital investment, however, prices of land and of purebred Gir cows had important influences.

Recria de machos Nelore em pastagens cultivadas com suplementação na seca nos Cerrados do Brasil Central

Body weight gain of 103 Nelore calves until 20/21 months old when weaned on cultivated pasture and supplemented during the dry period was evaluated during three years to obtain steers with body weight to be finished immediately at fedlot. At the beginning and end of supplementation period, the animals averaged body weight and age of 189.51± 21.08 kg and 254 ± 29.22 days and 242.38 ± 29.22 kg and 400 ± 31.08 days, respectively. The mean daily feed intake was 1.52 kg/head. The mean daily body weight gain in this period was of 0.377 kg and in the next rainfall season was of 0.534 kg. The correlation of body weight from the beginning to the end of supplementation and to the end of rainfall season was of 0.78 and 0.65, respectively. The highest correlations found among body weights were: at the end of the dry and rainfall period (r = 0.86); body weight and gain at the end of rainfall period (r = 0.62); body weight and gain at the end of rainfall period and total gain (0.75 and 0.71, repectively), gain at dry season and total gain (0.80). After weaning, the calves were classified into three classes: inferior (140 ± 11.37 kg), medium (187 ± 11.09 kg) and superior (219 ± 8.51 kg). The body weights at the end of rainfall season were of 271 ± 9.56 kg, 362 ± 22.75 kg and 425 ± 15.32 kg. At least 54% of the animals remained as inferior, 60% as medium and 54% as superior at the end of rainfall season. At 20/21 months old, the steers averaged body weight of 366 ± 39.04 kg and conditions to be finished in fedlot. However, there are calves weaned at six/seven months old with less than 150 kg of body weight, with lower potential to body weight gain and less conditions to be finished in fedlot even when supplemented previously.