SummaryResin acid composition (RAC) has previously been shown to inhibit the growth of the Gram-positive bacterial species Clostridium perfringens in vitro and to modulate the ileal microbiota of broiler chickens. The following trials examined the effect of RAC on broiler chickens in two experiments. In experiment 1, 1400 one-day-old Ross 308 broilers were divided into two coccidiostat treatments: chemical (CC) and ionophore (IC), which were further divided into two RAC dosages: 0 and 0.5 g/kg. All diets were supplemented with xylanase, β-glucanase and phytase feed enzymes. The birds were raised in a commercial-type environment without additional microbial challenge during the 42-day trial. RAC improved the body weight gain by 3.3% and feed conversion ratio by 5.7% with CC, and improved footpad lesion scores with IC but had no effect on the litter quality. Experiment 2 was a 35-day subclinical necrotic enteritis (NE) challenge trial with 510 male Ross 308 chickens. The dietary treatments included a non-challenged, non-supplemented control and four NE challenged treatments with dietary RAC supplementation at 0, 1, 2, and 3 g/kg. The birds were challenged with Eimeria maxima on day nine and C. perfringens on day 14. While RAC at 1 g/kg significantly increased bird weight gain during the challenge, it did not affect the microbial or short chain fatty acid (SCFA) profiles. In contrast, RAC at 3 g/kg reduced the abundance of the Lactobacillus group and tended to reduce the abundance of genus Bifidobacterium and the total numbers of eubacteria. These experiments suggest that dietary RAC at a moderate dose positively affected broiler performance. However, changes in caecal microbiota populations may not have influenced the observed performance effects of RAC.

The present contribution focuses on the feasibility and interest of setting up a multi-disciplinary project in the field of multibody dynamics, as a sequel to the undergraduate course in classical mechanics. The pedagogical objectives of this ''learning layer'' cover various aspects, namely: give the student the opportunity to exploit and analyze the equations of motion for a real application, make them able to formulate consistent hypotheses for such applications and promote an actual multi-disciplinary activity (mechanics, numerical methods, computer science and CAD). The project is performed by groups of students and is organized in the frame of a global active pedagogical process which characterizes our undergraduate engineering program at the Université catholique de Louvain (UCL, Belgium). After more than 10 years of experience, we can claim that this multi-disciplinary project really improves the student's skills in the field of multibody system modeling and computer simulation, including a timid but existing engineering attitude with respect to the results they obtain. Among the educational ingredients that make this project really fruitful educationally speaking, one must emphasize a key point of the approach, relating to the use of the symbolic multibody program ROBOTRAN to assist students in producing their equations of motion. Contrarily to research activities, the use of the ROBOTRAN symbolic models are exploited in such project, more for an educational motivation than for the computer efficiency of the simulation. ß

Over the recent years, there has been an increasing interest in improving pork quality, which at present often fails consumer requirements. Nutritional regime is one of the key environmental factors affecting fattening results, slaughter value and meat quality. The technological and organoleptic properties of pork can be modified through feeding. Numerous studies have been conducted to determine the effect of diet composition on meat quality.Consumers prefer lean pork with a bright reddish-pink color, and they object to muscles that are too pale or too dark. An excess amount of meat juice in the package is also considered unacceptable.The role of vitamins, minerals and feed additives in animal nutrition is an important consideration. Animal production efficiency is dependent upon an adequate supply of nutrients and minerals. Nutrient availability from feedstuffs is a principal factor in improving animal productivity and health as well as meat quality. Organic forms of minerals have been proven to have high bioavailability.Since the magnesium content of standard diets satisfies the needs of animals, pigs are usually not provided with supplemental magnesium. However, research results show that magnesium compounds have a beneficial influence on selected aspects of pig production. Dietary magnesium supplementation positively affects the behavior of animals, decreases their stress sensitivity and improves pork quality by enhancing meat color, reducing drip loss and increasing acidity.

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This paper proposes a formulation for modelling mechanisms with cam/follower type of contact using a multibody approach in relative coordinates. The proposed approach is inspired from the wheel/rail contact model developed in (Fisette, Samin, 1994) but in the present case, possible intermittent contact between the cam and the follower is considered, for generality purposes. Loop kinematic constraints are introduced to satisfy tangent and punctual contact as long as the bodies lean against each other. The effective presence (or not) of the contact is governed by the sign of the normal constraint force which can be computed thanks to the Lagrange multipliers technique. The above-mentioned option to kinematically constraint the bodies in their “contact phase” unavoidably leads to shift from one model to another when a contact disappears (or conversely reappears). Indeed, this increases (or decreases) the number of degrees of freedom of the current system. The control of the variable partitioning is thus absolutely necessary and is all the more complex that practical applications can contain several pairs of bodies in intermittent contact. As regards the applications, a comparison with another multi-body formalism and an experimental validation are discussed at first. Then, the modelling and simulation of universal wheels of an omnimobile mobile robot, developed in our Division, are proposed. The latter model represents a quite original application of the proposed multibody formulation. Computations are now in progress to analyse the complete behaviour of the robot, including control performances.

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