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Environmental effects that occur as a result of the different factors of production are manifested as changes in various components of agricultural systems as well as in their ecological functions, such as nutrient cycling. The degree of intensification of animal production systems can be defined fr...
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| Formato: | Tesis doctoral acceptedVersion |
| Lenguaje: | Español |
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Universidad de Buenos Aires. Facultad de Ciencias Veterinarias
2017
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| Acceso en línea: | http://repositoriouba.sisbi.uba.ar/gsdl/cgi-bin/library.cgi?a=d&c=avaposgra&cl=CL1&d=HWA_2287 https://repositoriouba.sisbi.uba.ar/gsdl/collect/avaposgra/index/assoc/HWA_2287.dir/2287.PDF |
| Aporte de: |
| Sumario: | Environmental effects that occur as a result of the different factors of production are manifested as changes in various components of agricultural systems as well as in their ecological functions, such as nutrient cycling. The degree of intensification of animal production systems can be defined from the relationship between the amount of livestock units and supplies associated, and the area they occupy. From this point of view, beef cattle production on forage qualifies as "extensive system", while the growing and fattening in confinement as "intensive system". The overall objective of this thesis was to identify and build indicators that could be the basis for the development of weighted indices that serve to differentiate beef cattle production systems according levels of intensification in the use of nutrients. Various indicators were identified and built; the information originated by the selected indicators were analyzed and integrated; the different systems were compared according to nutrient management indicators and ranges of variation of the indicators developed for each group of beef cattle production systems were identified. To characterize production systems Static Diagnosis and Flowcharts were used, taking into account the selection of study units, the recognition of ingress/egress of nitrogen and phosphorus pathways to the production systems and the compilation of agro-ecological and productive information. The study area was limited to the locations of Carmen de Areco, Trenque Lauquen, Chascomús, Maipú, Balcarce and Laprida in Buenos Aires province, Argentina. Farms, experimental modules and beef cattle confinements were surveyed and selected to obtain information on the different types of beef cattle production systems: extensive with none or minimal supplementation, semi-intensive (extensive with supplementation) and intensive in confinement corrals (feedlots), some of them with agricultural activity (mixed farms). The information of the 1996-2014 periods was collected to obtain records of various periods of time for the description of the internal nutrient transfers. The information obtained per unit of study and productive period of time was reported as an observation, identified as "Analysis Unit" (UdA). For Extensive system five examined units of study provided 31 UdAs, for Semi-intensive system 13, who contributed 17 UdAs, Intensive system provided 35 UdAs and Mixed farm, 4 UdAs, completing 57 units of study and 87 UdAs. The collection of information was done through semistructured surveys during interviews; zonal statistics; bibliography and laboratory analysis for nitrogen and phosphorus contents in inputs and agricultural products. Descriptive statistical analysis, Spearman correlation, comparison by Median test and Principal Component and Cluster multivariate analysis were performed. For the description and characterization of the three types of beef cattle production systems Agroambiental Sustainability indicators related to the management and use of nitrogen and phosphorus, and feed, were selected, some specifically developed (Increment by Transference, Balance per nutrient in product produced, Difference between balances per nutrient), others adapted particularly for these production systems and others already existing, as Nutrient Balances. In mixed farms with feedlot included, the individual values of the Whole-farm Nutrient Balances and the Corral Nutrient Balances made possible to estimate the nitrogen and phosphorus surplus and their internal transfers via the Increment by Transference index, which contributed to characterize and differentiate the farms according to homogeneity of the distribution of nutrient that entered them. Through a set of five indicators it could be feasible to group Intensive systems(In) and differentiate them from the forage based systems, -Extensive(Ex) and Semi-intensive(Se)-.They were: Nutrient Balance per hectare (Bal/ha), Balance per product Produced (Bal-Prod-Pr), Balance per kilogram of body weight per day (Bal/kgPV), Inefficiency of Nutrient Use (IeUN) and Efficiency of external Nutrient Use by the Production (EUNexS-Pr). The ranges of descriptive values are presented. For Nitrogen, Extensive system had lower values than Semi-intensive for Bal N/ha(kgN/ha/dia): Ex 0,04-0,09 y Se 0,19-0,90; and for Bal/kgPV(gN/kgPV/dia): Ex 0,10-0,23 and Se 0,28-0,98, and better use efficiency, EUNexS-Pr(%): Ex: 9-20 and Se: 6-13. Intensive ones had the highest values for Bal N/ha: 6,50-59 kgN/ha/day and the lowest for IeUN: 21-59%. The lowest value of Bal-Prod-Pr was 65 gN/kgPV-Pr in Intensive systems and the highest, 385 gN/kgPV-Pr in Semi-intensive ones. In relation to Phosphorus, differentiation was less precise and with similar behavior, contributing the same indicators,\nexcept for one, the Bal-Prod-Pr. Instead, Balance per Nutrient in product Produced was significant. In the forage based systems, Bal N was always positive and Bal P with negative cases, especially in Extensive ones with little intensified breeding management. In Semi-intensive systems, higher nitrogen/phosphorous feed incomes resulted in higher Bal N-Bal P with consequent higher beef cattle production. In Intensive ones, these incomes were good predictors of the Corral Balances. It was possible to select indicators that allow a first advance in the characterization of beef production systems for the province of Buenos Aires, Argentina, based on the management of nitrogen and/or phosphorus in relation to environmental sustainability. Contributions were made for future studies with a wider variety of feed resources and/or forms of intensification, or for other areas of the country, and for the systematization of information and development of production models. Among the practical implications, intensification from fertilizers should harmonize productivity with Bal N-P that do not result in significant surpluses, and the increase in production of beef from annual crops should be assessed in line with Bal P values. The Bal/KgPV will allow to compare the effect of diets on environmental excretion, and when related to animal density of the corral it will be possible to have an approximation to the nutrient load that receives them. Knowledge of these indicators in production systems should, if necessary, be in the most advanced conditions to fulfill environmental requirements. |
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