Effects of dietary nitrogen levels and carbohydrate sources on apparent ruminal synthesis of some B vitamins in dairy cows

International audienceEffects of nitrogen level and carbohydrate source on apparent ruminal synthesis (ARS) of thiamin, riboflavin, niacin, vitamin B6, folates, and vitamin B12 were evaluated using 4 lactating Holstein cows distributed in a 4 x 4 Latin square design with treatments following a 2 x 2 factorial arrangement. Cows were fitted with cannulas in the rumen and proximal duodenum. The treatments were 2 N levels and 2 carbohydrate sources. The diet with the high N level provided 14% crude protein, calculated to meet 110% of the protein requirements and an adequate supply in rumen-degradable protein, whereas the diet with the low N level contained 11% crude protein, calculated to meet 80% of the protein requirements with a shortage in rumen-degradable protein. Carbohydrate source treatments differed by their nature (i.e., high in starch from barley, corn, and wheat, or high in fiber from soybean hulls and dehydrated beet pulp). All 4 diets were isoenergetic, based on corn silage, and had the same forage-to-concentrate ratio (60:40, dry matter basis). Duodenal flow was determined using YbCl3 as a marker. Each B-vitamin ARS was calculated as duodenal flow minus daily intake. The intake of several B vitamins varied among treatments, but because the animals consumed a similar amount of feed every day (average of 20 kg of dry matter/d) the difference was mostly due to vitamin content of each ingredient and their relative proportion in the diets. Decreasing N concentration in the diet reduced vitamin B6 duodenal flow and increased its apparent ruminal degradation. It also decreased duodenal flow and ARS of folates. The high-starch diets increased duodenal flow and ruminal balance of riboflavin, vitamin B6, and folates, whereas the high-fiber diets increased vitamin B12 ARS and duodenal flow. These effects on apparent synthesis are possibly due to changes in ruminal fermentation

A viability model of farming systems, the case of French West Indies

Compléter avec les actesCompléter affilitationOne the aims of the multidisciplinary research project Gaia-Trop on viability and adaptive management of small tropical islands agro-systems, was to devise a new model of farm system using tools of the mathematical viability theory. It has been constructed in close cooperation with French West Indies farmers to take into account their needs and expectations. The main emerging points focused on soil degradation, pest disease and climatic risks and economic constraints. A specific software is being developed for the viability calculus that will be made available for this community. We present first insights of this model and results obtained for only one parcel and without taking uncertainties at this stage. lt highlights that the objective of restoring the soil quality in the long term can be unstainable for farmers facing with financial constraints. The issue of sharing the costs of the agro-ecological transition must be asked