ABSTRACT
Different strategies have been used to mitigate greenhouse gas emissions from domesticated ruminants, including the removal of protozoa (defaunation). The objective of the present work was to analyze the potential of different N-oxide-containing aromatic heterocycles with known antiprotozoal activity as rumen-gas-abating agents. Nineteen pure compounds, belonging to seven different N-oxide chemotypes from our chemo-library were studied together with monensin in an in vitro rumen simulation assay. Fermentation profiles, i.e., gas production, pH, and short carboxylic acid concentrations, were compared to an untreated control at 96 h post inoculation. In our study, we investigated whole-ruminal fluid, with and without compound treatments, by NMR spectroscopy focusing on concentrations of the metabolites acetate, propionate, butyrate, and lactate. From data analysis, three of the compounds from different N-oxide chemotypes, including quinoxaline dioxide, benzofuroxan, and methylfuroxan, were able to diminish the production of gases such as monensin with similar gas production lag times for each of them. Additionally, unlike monensin, one methylfuroxan did not decrease the rumen pH during the analyzed incubation time, shifting rumen fermentation to increase the molar concentrations of propionate and butyrate. These facts suggest interesting alternatives as feed supplements to control gas emissions from dairy ruminants.
ABSTRACT
ABSTRACT: To study the effect of post-weaning feeding levels on the growth of dairy heifers, 40 animals with 77.7 ± 8.1 days of age and 77.5 ± 9.2kg of body weight were grouped in 10 pens, and each pen was randomly assigned to one of the following treatments for 120 days: feeding level to achieve a body weight gain of 600 (TMEDIUM) or 800 (THIGH) g/day based on a total mixed ration. After this period all heifers were managed as a single group for 150 days. Nutrient intake, behavior, body weight and other morphological measures were recorded in each animal. As a result of the experimental design THIGH heifers had a higher nutrient intake than TMEDIUM heifers, which was reflected in a higher daily weight gain, withers height, heart girth and hip width. However, treatments had no effect on these traits during the residual period.
RESUMO: Para estudar o efeito dos níveis de alimentação pós-desmame sobre o crescimento de novilhas da raça Holandês, 40 animais com 77,7 ± 8,1 dias de idade e 77,5 ± 9,2kg de peso corporal foram agrupados em 10 canetas, sendo que cada caneta foi aleatoriamente designada para um dos seguintes tratamentos por 120 dias: nível de alimentação para atingir um ganho de peso corporal de 600 (TMEDIO) ou 800 (TALTO) g/dia com base em uma ração total misturada. Após este período, todas as novilhas foram tratadas como um único grupo por 150 dias. A ingestão de nutrientes, o comportamento animal, o peso corporal e outras medidas morfológicas foram registrados em cada animal. Como resultado do delineamento experimental, as novilhas TALTO tiveram maior ingestão de nutrientes do que as novilhas TMEDIO, o que refletiu em maior ganho diário de peso corporal, altura dos gomos, circunferência do coração e largura do quadril. No entanto, os tratamentos não tiveram efeito sobre estas variáveis durante o período residual.
ABSTRACT
Metabolism of three different agro-pesticides widely used in Uruguay, the insecticides imidacloprid and thiamethoxam and the antiparasite nitroxinil, by bovine ruminal fluid, as supply of anaerobic microorganims, was studied. Complete ruminal fluid was incubated with each of the agrochemicals in different conditions, varying time, nutrients, and nitroethane supplementation as methanogenesis modificator. Only biotransformation was detected for nitroxinil in some of the studied variables. In the optimized condition only one product was generated and the chemical structure of this main metabolite was elucidated using combined spectroscopies evidencing a structural motive unrelated with the products of the corresponding mammal biotransformation results of reduction, and substitution processes. The ruminal generation of the metabolite was confirmed. In order to employ this anaerobic microbial system as potential bioremediator of agrochemical-contaminated soils, the toxicity, against mammal cells, and the mutagenicity, using Ames test, of the product of biotransformation were studied. The lack of toxic effects encouraged us to propose the ruminal system as a plausible system for agrochemicals bioremediation.
