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The enormous variety of substances which may be added to forage in order to manipulate and improve the ensilage process presents an empirical, combinatorial optimization problem of great complexity. To investigate the utility of genetic algorithms for designing effective silage additive combinations, a series of small-scale proof of principle silage experiments were performed with fresh ryegrass. Having established that significant biochemical changes occur over an ensilage period as short as 2 days, we performed a series of experiments in which we used 50 silage additive combinations (prepared by using eight bacterial and other additives, each of which was added at six different levels, including zero [i.e., no additive]). The decrease in pH, the increase in lactate concentration, and the free amino acid concentration were measured after 2 days and used to calculate a "fitness" value that indicated the quality of the silage (compared to a control silage made without additives). This analysis also included a "cost" element to account for different total additive levels. In the initial experiment additive levels were selected randomly, but subsequently a genetic algorithm program was used to suggest new additive combinations based on the fitness values determined in the preceding experiments. The result was very efficient selection for silages in which large decreases in pH and high levels of lactate occurred along with low levels of free amino acids. During the series of five experiments, each of which comprised 50 treatments, there was a steady increase in the amount of lactate that accumulated; the best treatment combination was that used in the last experiment, which produced 4.6 times more lactate than the untreated silage. The additive combinations that were found to yield the highest fitness values in the final (fifth) experiment were assessed to determine a range of biochemical and microbiological quality parameters during full-term silage fermentation. We found that these combinations compared favorably both with uninoculated silage and with a commercial silage additive. The evolutionary computing methods described here are a convenient and efficient approach for designing silage additives.The ensiling of forage crops in order to obtain winter or buffer feed for ruminant livestock is widely practiced in advanced management systems in temperate regions. The aim is to preserve crops having high moisture contents by encouraging rapid fermentation of water-soluble carbohydrates (WSC) in the crops to lactic acid by epiphytic lactic acid bacteria (LAB), which decreases the pH and inhibits the activities of plant enzymes and pathogenic or spoilage bacteria that could decrease the nutritive value of the silage.Grass is the predominant crop ensiled in Europe, and 50 million tons of grass silage are made each year in the United Kingdom alone (23, 61, 62). As with maize, the main crop ensiled in the United States, high WSC levels and a low buffering capacity in this crop are conducive to rapid acidification by epip...

In vitro gas production techniques have become popular for characterizing the rate and extent of digestion of ruminant foods. In a typical gas production study, gas (predominantly carbon dioxide) is produced as particles of substrate are fermented by rumen micro-organisms in a bicarbonate buffered culture medium. Innovations in equipment design, including automated pressure recording systems and mathematical descriptions of the gas production profiles themselves, make the techniques both simple and precise and therefore good as laboratory procedure. The technique of measuring gas is of value in ruminant science because the kinetics of gas production and substrate degradation are very closely correlated. However, although it is relatively easy to measure gas volumes and to determine the kinetics of gas production, the underlying processes that give rise to the gas in the first place are complex and not well understood. Therefore, there is concern about what is being measured in gas production studies and how this relates to the digestion process in the ruminant animal. In this paper we review some of the fundamental properties of gases, describe their behaviour in liquids and consider some of the biological and chemical factors influencing gas production. From a knowledge of how gases behave in liquids and at gas-liquid interfaces, both at ambient and increased temperatures and pressures, it is possible to deduce what is happening in gas production studies. However, although the technique is invaluable for obtaining information about the digestion of particulate substrates in anaerobic ecosystems, we conclude that gas production should be used with caution in routine food evaluation studies.

Background: Marketing, including the use of cartoon animations on packaging, has been shown to influence the food children choose to eat. This paper aims to determine the nutritional quality of UK food and drink products featuring child-friendly characters on pack. Methods: A comprehensive cross-sectional survey of food and drink with packaging appealing to children available in the UK. Products were classified high in fat, salt and/or sugar (HFSS) according to the UK nutrient profiling model and guidance for front of pack nutrition labelling. Logistic regression was used to determine whether there was a significant relationship between nutritional quality of products, and animation type. Results: Over half (51%) of 532 products with animations on packaging were classified as HFSS. Food products featuring unlicensed characters were significantly more likely to be deemed HFSS than those with licensed characters, according to both the nutrient profiling model (odds ratio (OR) 2.1, 95% CI: 1.3 to 3.4) and front of pack nutrition labelling system (OR 2.3, 95% confidence interval CI: 1.4 to 3.7). Conclusions: The use of cartoon characters on HFSS products is widespread. Policies to restrict the use of such marketing tactics should be considered to prevent children being targeted with unhealthy foods and drinks.

White clover nitrogen N content is generally high and constant throughout the growing season. It is also difficult to manipulate, as N 2 fixation tends to maintain a high N supply to the plant. White clover is a highly heterozygous, natural out-breeder, but self-fertile lines have recently been developed, including one which fails to develop nodules when grown under appropriate physiological conditions. An advantage of this line is that leaf protein content can be manipulated by altering the N supply to the plant and, in addition, it offers the opportunity to examine the effect of protein content on silage quality. This line was grown under varying levels of nitrate-N, giving rise to plants with a range of protein contents which were subsequently conserved as silage in two separate experiments. In experiment 1, both herbage protein and water-soluble carbohydrate (WSC) content varied, with values ranging from 17 to 31 g/kg dry matter (DM) and 52 to 72 g/kg DM, respectively. Protein content also varied in herbage grown for experiment 2, ranging from 20 to 33 g/kg DM, but variation in WSC content (91-101 g/kg DM) was not statistically significant. Silage quality was dependent on the protein content of the fresh herbage in both experiments. A comparison of herbages with high and low initial protein content, from experiments 1 and 2, respectively, revealed that a high protein content resulted in silages with a higher pH .L. Winters et al. / Animal Feed Science and Technology 116 (2004) 319-331 versus 659 g/kg TN), and an increase in free amino acid content when expressed as a proportion of total N (267 g/kg versus 90 g/kg and 323 g/kg versus 200 g/kg TN). A higher initial protein content results in a higher proportion of protein degradation during ensiling.

Gas production from the in vitro digestion of forage with buffered rumen fluid can be measured and used to determine forage digestibility and fermentation kinetics. Rumen micro-organisms ferment carbohydrate to gases (CO2 and CH4) and volatile fatty acids (VFA). The VFA produced also cause CO2 to be released from the C02-bicarbonate buffer. Theodorou et al. (1994) introduced the principle of measuring gas production by pressure increase using an electronic pressure transducer and sealed gas-tight culture bottles. Gases accumulate in the head space of the culture bottles as fermentation proceeds. The gas is measured and then released at regular intervals throughout the fermentation. This procedure was automated (Davies et al., 1995). The automated pressure evaluation system (APES) has advantages over the manual pressure transducer technique (Theodorou et al., 1994) in that it is less labour intensive and has been shown to be more sensitive to food characteristics (Davies et al., 1995). The APES, used in this work, has been improved to include new switches and a filtering system. It has been used here to determine the fermentation characteristics of various ruminant foods: ryegrass, wheat grain and ryegrass silage.

Inoculants containing lactic acid bacteria, added to herbage at time of cutting, aid the natural process of fermentation to produce lactic acid during ensilage. This lowers the pH and preserves the silage. It is also claimed that enzyme additives break down polysaccharides in plant cell walls, releasing fermentable sugar to stimulate fermentation and increase the digestibility of the silage. This study was carried out to investigate the effects of inoculants and enzymes on silage fermentation characteristics and gas production during in vitro fermentation.A second cut of perennial ryegrass (Lolium perenne) was mown, chopped to 2 – 4 cm lengths, divided into aliquots and treated at a rate of 10 ml kg-1. The treatments were: 1) control (water), 2) inoculant (Pediococcus pentosaceus, Lactobacillus plantarum and Propionibacter jensenii at 1.6 x 105 cells g-1 herbage) 3) enzyme (xylanase, β-glucanase and amylase, applied at a rate of 0.001 g kg-1 herbage) and 4) inoculant + enzyme.

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