A novel model to explain dietary factors affecting hypocalcaemia in dairy cattle

Most dairy cows exhibit different degrees of hypocalcaemia around calving because the gestational Ca requirements shift to the disproportionately high Ca requirements of lactation. Ca homeostasis is a robust system that effectively adapts to changes in Ca demand or supply. However, these adaptations often are not rapid enough to avoid hypocalcaemia. A delay in the reconfiguration of intestinal Ca absorption and bone resorption is probably the underlying cause of this transient hypocalcaemia. Several dietary factors that affect different aspects of Ca metabolism are known to reduce the incidence of milk fever. The present review describes the interactions between nutrition and Ca homeostasis using observations from cattle and extrapolations from other species and aims to quantitatively model the effects of the nutritional approaches that are used to induce dry cows into an early adaptation of Ca metabolism. The present model suggests that reducing dietary cation–anion difference (DCAD) increases Ca clearance from the blood by dietary induction of systemic acidosis, which results in hypercalciuria due to the loss of function of the renal Ca transient receptor potential vanilloid channel TRPV5. Alternatively, reducing the gastrointestinal availability of Ca by reducing dietary Ca or its nutritional availability will also induce the activation of Ca metabolism to compensate for basal blood Ca clearance. Our model of gastrointestinal Ca availability as well as blood Ca clearance in the transition dairy cow allowed us to conclude that the most common dietary strategies for milk fever prevention may have analogous modes of action that are based on the principle of metabolic adaptation before calving

Heat Stress and feeding strategies in meat-type chickens

Heat stress can induce hyperthermia in poultry. A reduction in heat load can be achieved by increasing the possibilities for dissipation, decreasing the level of heat production or by changing the thermal production pattern within a day. Strategies to reduce the negative effects of heat stress can be based on a specific feeding strategy, such as restricted feeding. Feed that is offered long enough before a hot period can ameliorate the harmful effects of high temperature. Another strategy may be to use choice feeding from different feed ingredients, rich in protein or in energy. With such self-selection, the chicken may adjust its intake of individual components, allowing the bird to optimise the heat load associated with the metabolism of the ingested nutrients. Additional promising strategies involve offering a choice between feeds with a different feed particle size or structure. A large particle size contributes to the development of the gastro-intestinal tract (GIT), especially the gizzard and the caeca. A large gizzard will maximize the grinding process and potentially ease digestion down the GIT, thereby reducing heat production associated with digestive processing. Also wet feeding may be profitable under heat stress conditions as well. Feeding wet diets may facilitate an increased water intake and larger particle sizes can limit water excretion in droppings, resulting in more water being available for evaporation during panting, hence cooling the bird. In conclusion, these feeding strategies may help to reduce heat production peaks, facilitate evaporative activity and/or decreases the heat load, resulting in beneficial effects on performance and health of the bird kept in more tropical areas worldwide

Mineral load on the paddock of organic sows in the Netherlands

The main aim of this study was to quantify nutrient deposition on the paddock in Dutch organic pig farms. Observations of excreting behaviour of grazing sows were carried out at three farms in each of two measuring seasons (spring/summer and autumn). The nutrient loads of N, P and K were calculated according to their content in urine and faeces, average weight of urine and faeces per excretion, and number of urinations and defecations done in the paddock. The N and P loads on the paddock varied greatly between the organic pig farms (P<0.01 for N, not significant for P and P<0.05 for K). The total amount of nutrients on two of the farms far exceeded the permitted levels (170 kg.ha-1year-1 for N and 44 kg.ha-1year-1 for P). On all three farms, faeces were unevenly distributed in the paddock. Regular rotation of paddocks resulted in a more uniform distribution

Effect of season and farming system on the quantity and nutritional quality of scavengeable feed resources and performance of village poultry in central Tanzania

2 x 2 factorial study was conducted to assess the effect of season and farming system on the quantity and nutritional quality of scavengeable feed resources and the performance of village poultry in central Tanzania. A total of 648 scavenging chickens purchased from farmers were slaughtered and the crop contents were subjected to physical and chemical analysis. The mean fresh weights of the crop contents were higher (

Intestinal gene expression in pigs: effects of reduced feed intake during weaning and potential impact of dietary components

The weaning transition is characterised by morphological, histological and microbial changes, often leading to weaning-associated disorders. These intestinal changes can partly be ascribed to the lack of luminal nutrition arising from the reduced feed intake common in pigs after weaning. It is increasingly becoming clear that changes in the supply with enteral nutrients may have major impacts on intestinal gene expression. Furthermore, the major dietary constituents, i.e. carbohydrates, fatty acids and amino acids, participate in the regulation of intestinal gene expression. However, nutrients may also escape digestion by mammalian enzymes in the upper gastrointestinal tract. These nutrients can be used by the microflora, resulting in the production of bacterial metabolites, for example, SCFA, which may affect intestinal gene expression indirectly. The present review provides an insight on possible effects of reduced feed intake on intestinal gene expression, as it may occur post-weaning. Detailed knowledge on effects of reduced feed intake on intestinal gene expression may help to understand weaning-associated intestinal dysfunctions and diseases. Examples are given of intestinal genes which may be altered in their expression due to supply with specific nutrients. In that way, gene expression could be modulated by dietary means, thereby acting as a potential therapeutic tool. This could be achieved, for example, by influencing genes coding for digestive or absorptive proteins, thus optimising digestive function and metabolism, but also with regard to immune response, or by influencing proliferative processes, thereby enhancing mucosal repair. This would be of special interest when designing a diet to overcome weaning-associated problem

Vom Mehrwert digitaler Simulationen dreidimensionaler Bauten und Objekte in der architekturgeschichtlichen Forschung und Lehre

Der Beitrag zeigt den didaktischen Mehrwert auf, der durch den Einsatz digitaler Medien in der architekturgeschichtlichen Lehre gegenüber herkömmlichen Präsentationsformen erreicht werden kann. Anhand von Fallbeispielen werden verschiedene Formen der digitalen Simulation architektonischer Räume vorgeführt und deren Einbindungsmöglichkeiten in Vortrags- und Lehrsituationen erläutert. Abschließend wird darauf verwiesen, welche Konsequenzen diese Entwicklungen hinsichtlich wissenschaftlicher Fragestellungen im architekturhistorischen Diskurs mit sich bringen. Grundriss, Aufriss, Schnitt und Axonometrie haben sich in der Neuzeit nicht nur als Kanon der Architekturdarstellung im Entwurfsprozess herausgebildet, sondern sind neben der fotografischen Erfassung eines Gebäudes gleichermaßen auch die Grundlage für die Dokumentation und Analyse historischer Bauwerke. In der kunsthistorischen Forschung und Lehre bilden sie daher die traditionellen bildlichen Schemata für die Darstellung historischer Bauten in Publikationen und Vorträgen. Sie entsprechen in ihrer Zweidimensionalität und Unbewegtheit insbesondere den medienimmanenten Anforderungen einer Textpublikation, können also gut als textergänzende Abbildungen auf Papier gedruckt werden. Diesem Darstellungskanon sind allerdings zwei Prämissen inhärent: erstens dass sich dreidimensionale Räume über das Hilfsmittel der Projektion als zweidimensionale Flächen abstrahieren lassen und zweitens dass ein architektonischer Raum mit einem Objekt und seinen begrenzenden Flächen identifiziert werden kann. Ein solcher Raumbegriff gerät in der jüngeren Forschung jedoch zunehmend in die Diskussion. Eine architekturgeschichtliche Forschung, die sich in zeitgemäßer Form mit Raumfragen auseinandersetzen will, besitzt mit den digitalen Medien heute erstmals angemessene Visualisierungs- und durch das Potential interaktiver Elemente auch Verifizierungsmöglichkeiten für ihre Thesen. Es ist zu erwarten, dass sich diese visuellen Darstellungsmöglichkeiten auch auf das Publikationswesen wissenschaftlicher Information auswirken werden. Bislang lassen sie sich in das Vortrags-, nicht aber in das gängige Publikationswesen integrieren. (Vortrag am 16.3.2007 beim XXIX. Deutschen Kunsthistorikertag in Regensburg

Canine and feline pregnancy loss due to viral and non-infectious causes : a review.

Among the causes for pregnancy loss, viruses and non-infectious factors are among the most important. In both dogs and cats, research and clinical evidence provide proof that there is an increasing incidence of pregnancy loss associated with infectious diseases like herpesvirus, as well as the presence of toxicants or chemicals in the animal's diet and environment. Endocrine causes must be taken into consideration when dealing with pregnancy loss. This review will cover the most recent knowledge regarding viral and non-infectious of pregnancy losses in the dog and cat