Dissertations / Theses on the topic 'Growing pigs'

The aim of this study was to determine the optimal amino acid balance in dietary protein for the growing pig. The method used was based on the principle that removal of any amino acid in excess of that required in this amino acid pattern should not affect nitorgen retention. A semi-purified diet based on casein and amino acids was used in a series of experiments. A proportion of each amino acid was removed in turn from the control amino acid pattern to determine how much could be removed without affecting nitrogen retention. The effect of changing the ratio of essential: non-essential amino acid was also examined. From these experiments an ideal dietary amino acid pattern for growing pigs was determined. This pattern was utilized significantly better than that proposed by ARC(1981). The property that in such an ideal pattern each amino acid should be equally limiting was tested and confirmed in both short and long term nitrogen balance trials. In the final experiment, the optimum ratios between lysine, methionine, threonine and tryptophan at two different rates of growth were determined using diets based on maize and soya bean meal. It was found that less threonine was needed than was deduced from the experiment with semi-synthetic diets. From the results of all the experiments the following amino acid pattern (g/160gN) is suggested: lysine 65, methionine + cystine 39, threonine 43, tryptophan 12, valine 49, isoleucine 39, leucine 72, phenylalanine + tyrosine 78, histidine 25.

Optimal nutritional management of growing pigs is constrained by lack of quantitative information on the response of animals between 30 and 110 kg live weight to dietary energy content. Under 'ideal' conditions modern genotypes appear to adjust feed intake to maintain a constant DE intake over a much wider range of dietary energy concentrations than previously thought (Mullan et al, 1998). However, under commercial pen conditions, voluntary feed intake is lower, pigs respond in terms of both growth rate and feed conversion to dietary DE density considerably above the levels currently thought to maximise biological and economic responses. The present study was designed to provide information on the response of growing pigs to dietary energy content under ideal and commercial housing conditions for two growth periods 30-60kg liveweight and 60-100kg liveweight. The results of the pigs kept under individual (ideal) housed conditions were consistent with the literature in that they adjusted their voluntary feed intake with digestible energy density to maintain a constant energy intake. The results of the pigs kept in groups (commercial) housing conditions tended to increase their daily energy intake as the energy density of the feed increased. This increase in energy intake improved the growth rate of the pigs and increased the fat deposition of those pigs. Economic analysis of the experiments involving pigs in groups indicates that formulating diets to a least cost per megajoule of digestible energy is not the most profitable point to set the digestible energy density. Modelling programs need to be used to determine where the least cost per unit of growth of the pig occurs. This is the most economical digestible energy density to formulate too. This will have major impact on the cost of production of piggery operations as the cost of energy is the single most important parameter in the cost of producing a pig.

Thesis (M. Sc. Vet. Sc.)--University of Sydney, 2004.
Title from title screen (viewed 14 May 2008). Submitted in fulfilment of the requirements for the degree of Master of Science in Veterinary Science to the Faculty of Veterinary Science. Includes bibliographical references. Also available in print form.

A series of investigations were undertaken to provide information for compounders to consider when including fibrous foods in diets for growing pigs. The work involved measurements of nutrient digestibilities, growth trials and calorimetric studies. The digestibility of the neutral detergent fibre (NDF) fraction of a food was dependent on a number of factors including the source of fibre, the adaptation period and liveweight of the pig, and the protein and lipid contents of the diet. The level of addition of food fibre was not important in determining the digestibility of the NDF component of a fibre source, whereas an inverse relationship was found between the digestibility of nitrogen and energy, and the level of added food fibre. It was concluded that increasing the level of addition of food fibre is more important in determining the depressive effect on the digestibility of non-fibre components than its own. Rapid growth was achieved when young, weaned and growing pigs were given diets containing wheatfeed and sugar-beet pulp. A substantial part of the energy supplied was in the form of VFA produced by the fermentation of non-starch polysaccharides in the wheatfeed and sugar-beet pulp. A growth trial with diets containing sugar-beet pulp and maize revealed that fermented energy from beet pulp was used with an efficiency of 0.72 that of the energy of maize. The apparently digested energy arising from the fermentation of non-starch polysaccharides, therefore, does not correspond directly in terms of potential use to the animal with that obtained by the enzymic digestion of maize starch. A net energy value for sugar-beet pulp was also calculated. This work has shown that wheatfeed and sugar-beet pulp may be useful as dietary ingredients for growing pigs. However, growth rates may be slightly depressed due to a lower efficiency of utilisation of apparently digested energy from the fibrous fraction of the diet. This could lead to on farm problems associated with a decreased throughput eg overstocking. However, the use of a corrected digestible energy value and ileal digestibilities of amino acids for a fibrous food, when formulating rations, could lead to an improvement in the prediction in performance. As well as the nutritional aspects of feeding fibrous foods, there are also a number of non-nutritional factors which will influence the use of fibrous materials and these are discussed in the light of their practical implications for the feeding of fibrous foods to pigs.

Raspberry pomace, consisting of seeds, pulp and added rice hulls, is the residue from the pressing of raspberries for juice and concentrate production. Through the determination of chemical composition by laboratory analyses and the measurement of feeding value in animal trials, the pomace was evaluated as a feedstuff for growing pigs. Pomace contains 11.1% crude fat, 10.0% crude protein, 59.5% total dietary fibre, 7.4% soluble carbohydrates, and a gross energy level of 5220 kcal*kg⁻¹. The acid detergent residue of the pomace contains 11.7% lignin, 6.0% cutin, 2.2% acid detergent ash and 26.0% cellulose (by difference). The digestibility of dry matter, fat, protein and energy was determined. Pomace dried at 60 C, whole and ground (1mm) was fed to growing male pigs (30-35 kg) in a replicated 4X4 Latin Square design with treatments basal (B) , B plus 40% unground pomace, B plus 40% ground pomace and B plus 40% barley. Grinding of pomace significantly improved the digestibility of all parameters measured, however, the barley-soybean meal basal ration was consistently better digested than either of the pomace treatments. The digestibility of whole and ground pomace was respectively: dry matter 10.7% and 20.8% (S.E.M. 1.30), fat 24.1% and 79.7% (S.E.M. 3.47), protein 10.6% and 14.7% (S.E.M. 4.83) and energy 7.9% and 28.4% (S.E.M. 1.80). Protein quality of ground (1mm) and freeze-dried pomace was evaluated with rats in metabolism cages to produce the following values: true protein digestibility 36.0% (S.E.M. 0.66), biological value 91.0% (S.E.M. 3.46), and net protein utilization 32.7% (S.E.M. 1.15). In rat growth trials, where pomace replaced barley incrementally, growth rate was not affected at replacement levels up to 40%, although feed efficiency declined consistently as the level of pomace in the diet increased. It is suggested that raspberry pomace could replace up to 20% of an energy feedstuff in a ration for growing swine without significantly reducing growth rate or feed efficiency.
Land and Food Systems, Faculty of
Graduate

Group housed pigs make less frequent feeder visits of a longer duration, and eat at faster rate than pigs housed individually. They also have lower growth rates which may be due to elevated stress associated with aggression and social stress. The aim of this thesis is to investigate the stability of feeding patterns in individual pigs, the effect of grouping and group composition on feeding patterns and to assess the consequences of this shift in feeding behaviour for the welfare and performance of grouped pigs. The flexibility of feeding behaviour was assessed by restricting the time of access to food of previously ad libitum fed pigs to 2 hours per day and then returning them to 24 hr access. When pigs had restricted access to food they made fewer daily feeder visits, of a longer duration, with a higher food intake per visit than the control pigs that had 24 hour access to food throughout. Flexibility was assessed by comparing feeding behaviour before and after restriction. The pigs that experienced a period of restricted feeding either resumed their previous behaviour or showed the same trend as the controls. It was concluded that feeding behaviour was flexible. A second experiment investigated the effect of grouping on feeding behaviour. Pigs were housed individually for 3 weeks after which they were combined into groups of 4 for 3 weeks, before being returned to individual housing for a further 3 weeks. When grouped, pigs made fewer visits to the feeder of a longer duration than when they were housed individually. Possible explanations for the changes in feeding behaviour are competition, group cohesion, or that the high frequency of feeder visits when the pigs are housed individually is a consequence of a lack of social stimulation. The results suggest that group cohesion is most likely to have been causal in the observed changes in feeding behaviour.

A method of continuously monitoring weight would aid producers by ensuring all pigs are gaining weight and increasing the precision of marketing pigs thus saving money. Electronically monitoring weight without moving the pigs to the scale would eliminate a stress-generating source. Therefore, the development of methods for monitoring the physical conditions of animals from a distance appears as a necessity for obtaining data with higher quality. In pigs\' production, animals\' weighing is a practice that represents an important role in the control of the factors that affect the performance of the herd and it is an important factor on the production\'s monitoring. Therefore, this research aimed to extract weight data of pigs through depth images. First, a validation of 5 Kinect ® depth sensors was completed to understand the accuracy of the depth sensors. In addition, equations were generated to correct the dimensions\' data (length, area and volume) provided by these sensors for any distance between the sensor and the animals. Depth images and weights of finishing pigs (gilts and barrows) of three commercial lines (Landrace, Duroc and Yorkshire based) were acquired. Then, the images were analyzed with the MATLAB software (2016a). The pigs on the images were selected by depth differences and their volumes were calculated and then adjusted using the correction equation developed. Also, pigs\' dimensions were acquired for updating existing data. Curves of weight versus corrected volumes and corrected dimensions versus weight were adjusted. Equations for weight predictions through volume were adjusted for gilts and barrows and for each of the three commercial lines used. A reduced equation for all the data, without considering differences between sexes and genetic lines was also adjusted and compared with the individual equations using the Efroymson\'s algorithm. The result showed that there was no significant difference between the reduced equation and the individual equations for barrows and gilts (p<0.05), and the global equation was also no different than individual equations for each of the three sire lines (p<0.05). The global equation can predict weights from a depth sensor with an R2 of 0,9905. Therefore, the results of this study show that the depth sensor would be a reasonable approach to continuously monitor weights.
Um método de monitoramento contínuo da massa corporal de suínos auxiliaria os produtores, assegurando que todos os animais estão ganhando massa e aumentando a sua precisão de comercialização, reduzindo-se perdas. Obter eletronicamente a massa corporal sem mover os animais para a balança eliminaria uma fonte geradora de estresse. Portanto, o desenvolvimento de métodos para monitorar as condições físicas dos animais à distância se mostra necessário para a obtenção de dados com maior qualidade. Na produção de suínos, a pesagem dos animais é uma prática que representa um papel importante no controle dos fatores que afetam o desempenho do rebanho e o monitoramento da produção. Portanto, esta pesquisa teve como objetivo extrair, automaticamente, dados de massa de suínos por meio de imagens em profundidade. Foi feita, primeiramente, uma validação de 5 sensores de profundidade Kinect ® para compreender seu comportamento. Além disso, foram geradas equações para corrigir os dados de dimensões (comprimento, área e volume) fornecidos por estes sensores para qualquer distância entre o sensor e os animais. Foram obtidas imagens de profundidade e massas corporais de suínos e crescimento e terminação (fêmeas e machos castrados) de três linhagens comerciais (Landrace, Duroc e Yorkshire). Em seguida, as imagens foram analisadas com o software MATLAB (2016a). Os animais nas imagens foram selecionados por diferenças de profundidade e seus volumes foram calculados e depois ajustados utilizando a equação de correção desenvolvida. Foram coletadas, ainda, dimensões dos animais para atualização de dados existentes. Curvas de massa versus volumes corrigidos e de dimensões corrigidas versus massa, foram ajustadas. Equações para predição de massa a partir do volume foram ajustadas para os dois sexos e para as três linhagens comerciais. Uma equação reduzida, sem considerar as diferenças entre sexos e linhagens, também foi ajustada e comparada com as equações individuais utilizando o algoritmo de Efroymson. O resultado mostrou que não houve diferença significativa entre a equação reduzida e as equações individuais tanto para sexo (p <0,05), quanto para linhagens (p <0,05). A equação global pode predizer massas a partir do volume obtido com o sensor, com um R2 de 0,9905. Portanto, os resultados deste estudo mostram que o sensor de profundidade é uma abordagem razoável para monitorar as massas dos animais.

The aim of this study was to evaluate the growth supporting value of DE derived from gut fermentation in growing pigs. Unmolassed sugar beet pulp (SBP) was selected as a model material for fermentation. For a reference material which would be digested in the small intestine by the endogenous enzymes, maize starch (MS) was selected. A cereal-based control diet was formulated to fulfil the needs of pigs for all essential nutrients apart from energy. To this control diet, either SBP (150 & 300 g/kg) or MS (100 & 200 g/kg) were added. The study consisted of two phases. The first phase (digestion trial and growth trial) was devoted to studying the digestion of these diets and to comparing the effects on growth of pigs of the two DE sources (SBP and MS). The second phase was to determine the production of VFA resulting from the fermentation of SBP. Methods used included stoichiometric calculations based on measurements of the molar proportions of VFA combined with CH4 production, and a direct assessment of the true fermented materials using antibiotics to suppress fermentation. The results of the first phase showed that the energy in SBP and MS had an apparent digestibility of 0.74 and 0.98. The DE from SBP was used for supporting carcass gain with an efficiency of 0.57 of the DE from MS. The results of the second phase indicated that measurements of methane production alone or even with inclusion of free hydrogen could underestimate the extent of fermentation in the gut of pigs. The results also suggest that with the cereal-based control diet, fermentation could supply up to 13.6% of the dietary DE in the form of VFA or 18.0% in the form of fermented energy. For this control diet incorporating 30% SBP, the respective values were 25.4% and 33.4%. The absorbed VFA resulting from the fermentation of SBP had a growth supporting value of 0.763 of that of absorbed glucose from MS.

The development of computerised single-space feeding systems, currently used by most breeding companies in their selection programmes, has made it possible to automatically monitor the feeding pattern of individual pigs whilst keeping the animals in a social environment. This thesis examines in detail the feeding pattern of growing pigs and investigates how different components of the social and physical environment affect the feeding behaviour and production performance of the animals. Four experiments were carried out studying the effects of the following factors: Group size, feeder design, trough space, and individual housing. Decreasing the accessibility of the food, either indirectly by increasing pig:trough ratio or directly by fitting an enclosed race in front of the trough, modifies the feeding behaviour of the animals in the direction of fewer, but longer visits to the trough. Increasing the social competition, either directly by increasing the group size or indirectly by offering low levels of protection from other pigs whilst feeding, increases the rate of eating. All pigs succeeded in adapting to the constraint placed on their feeding behaviour and adjusted to the lack of feeding space, as there were no significant effects of social and physical environment on production performance. No correlations were found between social behaviour (aggression level and rank) and any of the feeding behaviour and production variables. A change in the social environment from group to individual housing resulted in only a small increase in feeder visits, regardless of the feeding pattern displayed by the pig whilst group housed. However, this had significant effects on the daily feed intake of those animals with few, long visits, and suggests that these pigs were disadvantaged in terms of daily feed intake rather than number of feeder visits when group housed. The general discussion considers various criteria used in the literature to define 'a meal', briefly discusses the validity of such classifications of visits to the trough, and elaborates on the relationship between food accessibility and feeding pattern. The effects on feeding rate are placed in the context of competition and preferred rate of eating. A large number of additional environmental factors and their influence on feeding behaviour is reviewed.

For economical and ecological reasons, efficiency and profitability ofswine production relies heavily on the way pigs utilize key nutrients such as P,which is considered a potential pollutant of water ecosystems. Although cerealgrains and oilseed meals contain enough P to fulfill the biological needs of pigs,most of this P is tightly bound as phytate. As pigs do not have enough phytase(PHY) to cleave P from phytate, it is excreted in the feces. To prevent adeficiency, diets have traditionally been supplemented with highly availableinorganic sources of P. Today, an environmentally-friendly alternative is tosupplement diets with PHY.Growth promoting antibiotics are also used to enhance the utilization ofdietary components such as energy and N. It has been suggested that theantibiotic virginiamycin (VIR) could also improve phytate-P utilization by pigs.Eight experiments evaluated the effects of VIR and/or PHY amendmentson digestibility, retention, excretion, growth, bone characteristics, meat traits, andileal microflora populations of growing pigs fed corn–soybean meal (SBM) diets(seven experiments) or corn-SBM-rice bran diets (one experiment). Additionally,a comparison between two digestibility procedures was conducted for two of theexperiments.On average, VIR improved P digestibility and total P excretion by 5.0%,and P retention as a percent of absorption by 1.0%. Phytase amendmentsimproved P digestibility between 14 and 27%, and P retention (as a % ofabsorption) between 0.7 and 2.5%. In the growth trial, VIR supplementation wasassociated with numerical differences favoring bone mineralization and ilealphytate-utilizing bacteria populations. These observations demonstrate additionalresearch is warranted with this antibiotic under conditions of higher stress andbacterial load in the environment.According to the comparisons between digestibility methods, a single grabfecal collection was not reliable. Further, a cumulative grab collection for fivedays was not as good an option as the total collection method.It is concluded that VIR does improve P utilization in pigs fed corn-SBMdiets not supplemented with inorganic P. Similar effects, but of greatermagnitude, were confirmed for PHY-amended diets with either normal or highlevels of phytate P.

CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel Superior
Two assays were conducted, the first one to determine the nutrient digestibility and metabolizable energy of fish silage with microbiological inoculum for growing pigs, and the second one to evaluate the addition of fish silage flour, which was obtained from the mixture of 50% of corn and 50% of fish silage in diets for pigs at growing and finishing phases, regarding on performance, carcass characteristics, meat quality, sensorial evaluation of natural meat as well as mortadella and economic evaluation. In the digestibility assay, it was used 16 barrows with an initial average weight of 33.20 Â 4.93 kg, using the method of total collection of feces and urine. The fish silage presented 36.50% of crude protein, 14.45% of mineral matter, 39.78% of ether extract, and 4,032.09 kcal GE/kg. In the performance assay, 32 barrows with an initial average weight of 26.00 Â 1.68 kg were distributed among four treatments, considering the inclusion levels of 0, 25, 50 and 75% of fish silage flour with microbiological inoculum in the feed. For the whole period, there was a quadratic effect about the daily weight gain with increasing additions of fish silage flour to the diets, presenting the best results with the estimated level at 25.83%. With the increasing levels of fish silage flour there was a decrease on the average thickness of back fat, fat depth and loin depth, but carcass yield and the amount of lean meat were not affected. There was no effect on the quality characteristics of meat. Regarding the mortadella, the inclusion of fish silage flour from 25% in the feed resulted in better color attributes and between 25 and 50% for flavor and overall acceptability. The fish silage flour may be included in diets for pigs at growing and finishing phases up to 25% of inclusion, resulting in inclusion of up to 5.87% of fish silage on dry matter basis.
Foram realizados dois ensaios. O primeiro, para determinar a digestibilidade dos nutrientes e a energia metabolizÃvel da silagem de pescado para suÃnos em crescimento; e o segundo, para avaliar a adiÃÃo da farinha de silagem de pescado, obtida a partir da mistura de 50% de milho e 50% da silagem de pescado, em raÃÃes para suÃnos nas fases de crescimento e terminaÃÃo, quanto ao desempenho, caracterÃsticas de carcaÃa, qualidade da carne, anÃlise sensorial da carne in natura e da mortadela e avaliaÃÃo econÃmica. No ensaio de digestibilidade, foram utilizados 16 suÃnos machos castrados com peso mÃdio inicial prÃximo de 33,20  4,93 kg, sendo utilizado o mÃtodo de coleta total de fezes e urina. A silagem de pescado apresentou 36,50% de proteÃna bruta, 14,45% de matÃria mineral, 39,78% de extrato etÃreo e valor energÃtico de 4.032,09 kcal de EM/kg. No ensaio de desempenho, foram utilizados 32 suÃnos machos castrados, com peso inicial mÃdio de 26,00  1,68 kg, distribuÃdos entre quatro tratamentos, considerando os nÃveis de inclusÃo de 0, 25, 50 e 75% de farinha de silagem de pescado nas raÃÃes. No perÃodo total, observou-se efeito quadrÃtico sobre o ganho diÃrio de peso com as crescentes adiÃÃes de farinha de silagem de pescado Ãs dietas, apresentando o melhor resultado no nÃvel estimado de 25,83%. Com os nÃveis crescentes de farinha de silagem de pescado, houve reduÃÃo da espessura mÃdia de toucinho, profundidade de gordura, Ãrea de gordura e profundidade do lombo, porÃm o rendimento de carcaÃa e a quantidade de carne magra na carcaÃa nÃo foram reduzidos. NÃo houve efeitos sobre as caracterÃsticas qualitativas da carne. Em relaÃÃo à mortadela, a inclusÃo da farinha de silagem de pescado a partir de 25% na raÃÃo resultou nos melhores atributos de cor e entre 25% e 50% para sabor e aceitaÃÃo global. A farinha de silagem de pescado pode ser incluÃda em raÃÃes para suÃnos nas fases de crescimento e terminaÃÃo atà o nÃvel de 25% de inclusÃo, resultando na inclusÃo de atà 5,87% de silagem de pescado com base na matÃria seca.

Les acides aminés (AA) sont une composante essentielle du régime alimentaire des animaux de ferme, mais la détermination précise des besoins en AA est un défi. Les besoins en AA peuvent être influencés par de nombreux facteurs, notamment la génétique, la santé, l’âge et, comme récemment montrée, la variabilité individuelle. Dans les systèmes classiques d’alimentation des troupeaux par phase (SATP), tous les porcs reçoivent la même ration pendant de longues périodes. De ce fait et afin de s’assurer qu’ils expriment leur plein potentiel de croissance, la plupart des porcs reçoivent plus d’éléments nutritifs qu’ils n’en n’ont besoin, ce qui engendre des effets nuisibles sur l'environnement par l'excrétion d'azote accrue, et sur les coûts de production. Dans les systèmes d’alimentation individuelle de précision (SAIP), les porcs reçoivent une ration ajustée chaque jour en fonction de leurs besoins nutritifs. Dans ce contexte, il est nécessaire de distinguer les exigences de l’AA d’une population de celles des individus. Les rapports optimaux d’AA entre les différents AA essentiels ont été établis pour les systèmes d’alimentation classiques par phase, mais ces rapports pourraient différer selon qu’il s’agit d’un système d’alimentation classique ou d’un système d’alimentation de précision des porcs. L’objectif principal de cette recherche a été de comparer le rapport optimal thréonine: lysine (Thr: Lys) entre le système d’alimentation classique par phase et le système individuel d’alimentation de précision. À l’aide d’une méthodologie de dose-réponse avec cinq ratios Thr: Lys pour des porcs en croissance dans un SATP ou SAIP la composition chimique et la concentration en AA de la carcasse ont été affectées par le ratio Thr: Lys et l’ampleur ainsi que le type de réponse était dépendant du système d’alimentation utilisé. Il a été possible de confirmer l’hypothèse de départ selon laquelle les ratios optimaux des AA utilisés par le SATP ne sont pas adéquats pour établir les besoins des AA dans les systèmes d’alimentation de précision. Dans une seconde étude de dose-réponse avec des rapports Thr: Lys similaires offerts aux porcs en finition, les besoins de Thr:Lys étaient plus élevés que ceux observés précédemment pour les porcs en croissance suggérant que les besoins en AA pour le dépôt de protéine est dépendant de l'âge. Ces deux études suggèrent que les porcs peuvent moduler leur croissance et leur composition corporelle en fonction du niveau d'apport en AA et peuvent répondre différemment à la même quantité d'AA ingérée. Ces études soulignent en outre la faiblesse de l'utilisation d'un profil protéique idéal en considérant des exigences fixes en AA en raison de la composition en AA de la carcasse supposée constante. L'estimation précise des besoins en AA pour les porcs dans un SAIP semble être limitée par l'utilisation de ratios AA fixes, car les porcs ont des exigences en AA différentes. Enfin, une nouvelle approche basée sur une conception composite centrale avec une configuration factorielle visant à estimer indépendamment les besoins pour la Lys et la Thr en temps réel chez les porcs nourris individuellement a été proposée. Une réponse non unique du dépôt de protéines à diverses combinaisons Thr et Lys a été observée en raison des différences dans les exigences en AA entre les porcs. Cet aperçu de la variabilité entre les porcs est utile pour affiner le système d'alimentation de précision en estimant les besoins en AA de manière plus précise et en nourrissant les porcs selon leurs besoins individuels. De plus, cela permettrait de réduire le gaspillage de nutriments chez les porcs avec moins de dépôt protéique. Les résultats présentés dans cette thèse soutiennent l'idée que les changements dans la composition corporelle chez les porcs sont induits par des changements dans les niveaux alimentaires en AA. Par conséquent, la croissance peut être modulée en fonction de la composition corporelle optimale souhaitée par le consommateur. Cette thèse propose un changement de perspective dans la nutrition animale, où l’AA peut être un déclencheur de la réponse métabolique animale avec des exigences en AA dynamiques et distinctes chez les animaux de manière individuelle.
Amino acids (AA) are essential components of diets but accurate determination of AA requirements in farm animals is a challenge. Requirements for AA in pigs can be influenced by several factors, including genetics, health, age, and, as recently shown, also individual variability. In conventional group-phase feeding (GPF) systems, large groups of pigs receive the same feed during extended periods and most pigs receive more nutrients than required to express their growth potential with potential detrimental effects on the environment through increased nitrogen excretion, and on production costs. In individual precision feeding (IPF) systems, pigs are fed diets tailored daily to their individual nutrient requirements. In light of this, it is necessary to distinguish the AA requirements of a population from those of individuals. Optimal essential AA ratios have been established for pigs in conventional GPF systems, but these optimal AA ratios might differ for pigs in IPF systems. The main research objective was to compare the ideal protein profile in pigs using the optimal threonine-to-lysine (Thr:Lys) ratio between conventional GPF and IPF systems. Based on a dose-response approach with five levels Thr:Lys ratios offered to growing pigs in a GPF or IPF system, it was possible to confirm the initial hypothesis that optimal AA ratios differ between feeding systems. Carcass chemical composition and AA concentration was likewise affected by the Thr:Lys ratio, and the magnitude and type of response depended on the feeding system. In a second dose-response study with similar Thr:Lys ratios offered to late finishing pigs, requirements were larger than to those previously observed for growing pigs, suggesting that AA requirements for protein deposition is age dependent. These two studies suggest that individual pigs can modulate their growth and body composition according to the level of AA intake and can respond differently to same amount of ingested AA. These studies further highlighted the weakness of using an ideal protein profile by considering fixed requirements for AA due the assumed constant AA carcass composition. Accurate estimation of AA requirements for pigs in an IPF system seems to be mainly limited by the use of fixed AA ratios as pigs have different AA requirements. Finally, a novel approach to the dose-response approach based on a central composite design with a factorial design aiming at independently estimating real-time requirements for Lys and Thr in individual pigs was proposed. A non-unique response of protein deposition to various Thr and Lys combinations was observed due to the differences in AA requirements among individual pigs. This insight on variability among individual pigs is useful to fine-tune the precision feeding system by estimating AA requirements more accurately, feeding pigs according to their individual requirements, and, ultimately, reduce waste of nutrients in pigs with lower protein deposition. The results presented in this thesis support the idea that changes in body composition in pigs are induced by changes in dietary AA levels. Therefore, growth may be modulated to the optimal body composition desired by the consumer. This thesis proposes a change of perspective in animal nutrition, where AA may be seen as a trigger for animal metabolic response with dynamic and distinctive AA requirements in individual animals.
Os aminoácidos (AA) são componentes essenciais das dietas, mas a determinação exata das exigências de AA em animais de criação é um desafio. Exigências nutricionais de AA em suínos podem ser influenciadas por vários fatores os quais incluem: genética, estado sanitário, idade, e como recentemente demonstrado, a variabilidade individual. Tradicionalmente animais recebem a dieta usando um sistema convencional de alimentação de grupos por fase (AGF). Nesse sistema todos os suínos recebem a mesma ração durante toda uma fase de crescimento e a maioria dos animais recebem mais nutrientes do que o necessário para expressar o seu potencial de crescimento. Isso vai impactar negativamente no meio-ambiente devido a grande excreção de nitrogênio e nos aumentados custos de produção. Em sistemas de alimentação precisão individual (API), os suinos são alimentados com dietas diariamente adaptadas às suas exigências individuais de AA. Neste contexto, é necessário distinguir as exigência de AA de uma população e de indivíduos. O perfil de proteína ideal foi estabelecido para suínos em sistemas convencionais de AGF, mas estas relações ideais de AA podem ser diferentes para suínos em sistemas API. O objetivo principal da pesquisa foi comparar o perfil de proteína ideal em suínos, usando a relação ideal treonina-para-lisina (Thr:Lys) entre sistemas convencionais de AGF e API. Usando a metodologia de dose-resposta com cinco relações Thr:Lys dentre de um sistema AGF ou API, foi possível confirmar a hipótese inicial que perfil de proteína ideal em suínos diferem entre sistemas de alimentação. A composição química e concentração de AA na carcaça também foi afetada pela relação Thr:Lys, e a magnitude e o tipo de resposta foram dependentes do sistema de alimentação usado. Em um segundo estudo de dose-resposta, com relações de Thr:Lys semelhantes as oferecidas anteriormente aos suínos em crescimento foram oferecidas à suínos em terminação. Foi possivel observar que para estes as exigências de Thr eram maiores do que aquelas observadas anteriormente para suínos em crescimento, sugerindo que as exigências de AA para deposição de proteína é idadedependente. Estes dois estudos sugerem que suínos podem modular a sua taxa de crescimento e composição corporal de acordo com o nível de ingestão de AA e podem responder de forma diferente a mesma quantidade de AA ingerido. Estes estudos destacam a fragilidade do uso do conceito perfil de proteína ideal, considerando exigências fixas de AA devido a assunção de que a composição de carcaça tem concentração de AA constante. A determinação exata das exigências de AA para suínos em um sistema API parece ser limitada principalmente pelo uso de relações fixas e constantes de AA, porém suínos têm exigências de AA diferentes entre eles. Finalmente, propõe-se uma nova abordagem baseada num desenho composto central com uma configuração fatorial visando independentemente estimar as exigências de Lys e Thr em tempo real para suínos em um sistema API. Com esta metodologia, observou-se uma resposta de deposição de proteína não-unica para diferent combinações de Thr e Lys, devido às diferenças nas exigências de AA entre suínos. Essa percepção sobre a variabilidade entre individuos é útil para ajustar o modelo de nutrição de precisão aprimorando as estimativas de exigências AA, nurrindo animais de acordo com suas necessidades individuais possibilitando a redução do desperdício de nutrientes especialmente em suínos com baixa deposição de proteína. Os resultados apresentados nesta tese, apoiam a ideia de que alterações na composição corporal em suínos são induzidas por alterações nos níveis dietéticos de AA. Portanto, o crescimento pode ser modulado para a composição de corporal ideal desejada pelo consumidor. Esta tese propõe uma mudança de perspectiva na alimentação animal, onde AA pode ser visto como um gatilho para desencadear uma resposta metabólica animal ao invés da tradicional visão de AA como exigências nutricionais fixas.

The overall aim was to develop a model of Phosphorous (P) intake, digestion, utilisation and excretion in growing/finishing pigs, and use it to investigate the consequences of different P management strategies. Initially, a dynamic, deterministic model was developed (Chapter 2). It was able to predict the digestible (digP) requirements of pigs of different genotypes and stages of growth, as well as the consequences of different dietary contents of P, Calcium (Ca) and exogenous phytase. The model was also able to predict the excreted amounts of soluble and insoluble P. Subsequently (Chapter 3) the model was evaluated against independent data and a sensitivity analysis of its predictions to model parameters was undertaken. Model outputs were most sensitive to the values of the efficiency of digP utilization and the non-phytate P absorption coefficient from small intestine. The model predicted satisfactorily the quantitative pig responses, in terms of P digested, retained and excreted, to dietary variations. The model performed well with ‘conventional’, European feed ingredients and poorly with ‘less conventional’ ones, such as DDGS and canola meal. In Chapter 4 the model was converted into stochastic, by introducing variation between pig digP requirements and the consequences of two strategies were investigated (phase feeding and sorting). The former was more effective in reducing P excretion than the latter. Finally the model was extended to include uncertainty in feed composition (arising from variability in ingredient nutrient content and mixing efficiency) to investigate how this would affect the outputs of the model. Due to the assumptions made, uncertainty about feed ingredient composition contributed more to performance variation than uncertainty regarding mixing efficiency. When uncertainty about both feed composition and pig characteristics was considered, it was uncertainty about feed composition rather than pig genetic characteristics that proved to have the dominant influence on variability in pig performance.

Title from PDF of title page (University of Missouri--Columbia, viewed on Feb 23, 2010). The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file. Dissertation advisor: Dr. Gary L. Allee. Vita. Includes bibliographical references.

Postnatal skeletal muscle growth occurs through myonuclear accretion and high protein turnover rate. While fiber type composition of the muscle could affect protein turnover rate, less is known about how fiber type influences the regulation of protein synthesis and degradation signaling pathways. Thus, the hypothesis of this work was that variation in fiber type composition will differentially affect the regulation of signaling pathways related to protein turnover in skeletal muscle hypertrophy in growing pigs. Downregulated protein synthesis signaling and reduced expression of type II MyHC isoforms have been reported in skeletal muscles of low birth weight (LBWT) neonatal pigs. Therefore, we sought to determine whether these changes are sustained until weaning and would explain the reduction in LBWT pig growth compared to their normal birth weight (NBWT) sibling at weaning. Another objective was to determine whether the regulation of protein turnover signaling pathways are correlated to fiber type differences in skeletal muscles. Our data suggest that the longissimus dorsi (LD, glycolytic) muscle of LBWT pigs experienced compensatory growth while the soleus (oxidative) remained proportionally smaller. Growth of the LD was accompanied by upregulation of translation initiation. Additionally, there was no difference in expression of MyHC isoforms between NBWT and LBWT pigs. These data suggest the rapid growth of the LD of LBWT pigs may be attributed to an upregulation of protein synthesis signaling and occurred only in glycolytic muscles. A caveat in LBWT pig model is that the reduction in type II MyHC at birth is not the only factor that could influence muscle growth, and that other factors may have confounded our results. This is why we aimed to use β-adrenergic agonist as a means to induce a shift fiber type in muscles to a more glycolytic phenotype. Our objective was to determine the influence of the β-adrenergic agonist Ractopamine (RAC) induced slow-to-fast fiber type transformation on the regulation of protein synthesis and degradation pathways. Although supplementation improved translational capacity, enhanced S6K1 phosphorylation, and reduced the abundance of calcium-dependent proteases, RAC feeding had no effect on body or muscle weights. These results suggest that a fiber type transformation without other physiological influences does not alter protein turnover signaling in favor of hypertrophy in growing pigs.
Master of Science
Skeletal muscles grow by increasing the amount of protein contained within them. The amount of protein deposited is determined by the net balance between the rates at which proteins are synthesized and degraded. However, not all skeletal muscles grow at the same rate. One factor that is thought to influence protein synthesis and degradation rates is the types of muscle fibers that are present within a muscle. These fibers can display a range of contractile and metabolic characteristics, from slow-twitch oxidative fibers to fast-twitch glycolytic fibers. In the presented studies, we sought to determine whether changes in fiber type composition result in difference to the signaling pathways the regulate protein synthesis and degradation, ultimately leading to differences in the muscle growth of young pigs. We have previously shown reduced activation of the protein synthesis pathway in the skeletal muscle of low birth weight (LBWT) newborn pigs. These pigs also had lower expression of glycolytic fibers. In experiment 1, we aimed to compare the signaling pathways regulating protein synthesis and degradation in LBWT and normal birth weight (NBWT) pigs at weaning. We also sought to determine if the regulation of these signaling pathways changed between muscles with differing fiber type compositions. The glycolytic longissimus dorsi (LD) muscle of LBWT pigs grew rapidly between birth and weaning whereas the highly oxidative soleus did not. In addition, the LD of LBWT pigs had greater protein synthesis signaling and similar expression of muscle fibers compared with NBWT pigs, suggesting the improvement in protein synthesis signaling of LBWT pigs between birth and weaning may be related to a shift in fiber type. In experiment 2, we used a compound called ractopamine hydrochloride (RAC) to promote a slow-to-fast fiber type switch in the muscle of young pigs. With this study, we sought to determine the effect of this fiber type transformation, without the influence of birth weight, on the regulation of protein synthesis and degradation pathways. Although RAC-fed pigs showed some minor changes that could improve protein synthesis and decrease protein degradation, RAC feeding had no observable effect on body weight or muscle growth. These results suggest that a fiber type transformation alone is not enough to promote muscle growth in growing pigs.

Kyoto University (京都大学)
0048
新制・課程博士
博士(農学)
甲第13904号
農博第1719号
新制||農||957(附属図書館)
学位論文||H20||N4371(農学部図書室)
UT51-2008-C820
京都大学大学院農学研究科応用生物科学専攻
(主査)教授 松井 徹, 教授 久米 新一, 教授 廣岡 博之
学位規則第4条第1項該当

A study was conducted to evaluate the use of Leucaena leucocephala leaf meal (LLM) as a protein supplement for pigs. In addition, an evaluation of detoxifying LLM, by sun-drying, water-soaking, or treating with ferrous sulphate (FeS04) solution was undertaken. The research involved two experiments; a growth study and a metabolic study. In the growth study sixteen, 12 weeks old Large White x Landrace pigs (average body weight 22.9 ± 2.12 kg) were fed four experimental rations; a commercial grain-based grower /finisher ration (control); or a ration containing 20% of either sun-dried LLM, water-soaked LLM, or FeS04-treated LLM, replacing the basal diet. There was a significant (P<0.05) decrease in liveweight gain, feed intake and feed conversion efficiency in pigs fed the ration containing sun-dried LLM. Growth rate, feed intake and feed conversion efficiency were not affected by the addition of water-soaked and FeS04-treated LLM to the basal diet. Triiodothyronine (T3) and thyroxine (T4) levels in the blood plasma were not affected by the dietary treatments. However, addition of FeS04-treated LLM to the basal diet significantly (P<0.05) decreased the back fat thickness of the pigs. In the metabolic study, the digestible dry matter (DDM) and digestible CP (DCP) were measured as well as mimosine, 3-hydroxy-4-(1H) pyridone (3,4-DHP) and 2,3DHP output in the faeces and urine.Addition of water-soaked LLM to the diet significantly (P<0.05) lowered the DDM of the diet, whereas addition of FeS04-treated LLM significantly (P<0.05) reduced the DCP. Sun-drying, water-soaking and treatment of LLM with FeS04 solution, did not enhance the output of mimosine or 3,4-DHP in the urine and faeces. The results suggest that water soaking or treatment with FeS04 solution reduces the antinutritional factors (presumably including mimosine) and therefore improves the nutritional quality of LLM containing diets for pigs.

A study was conducted to evaluate the use of Leucaena leucocephala leaf meal (LLM) as a protein supplement for pigs. In addition, an evaluation of detoxifying LLM, by sun-drying, water-soaking, or treating with ferrous sulphate (FeS04) solution was undertaken. The research involved two experiments; a growth study and a metabolic study. In the growth study sixteen, 12 weeks old Large White x Landrace pigs (average body weight 22.9 ± 2.12 kg) were fed four experimental rations; a commercial grain-based grower /finisher ration (control); or a ration containing 20% of either sun-dried LLM, water-soaked LLM, or FeS04-treated LLM, replacing the basal diet. There was a significant (P<0.05) decrease in liveweight gain, feed intake and feed conversion efficiency in pigs fed the ration containing sun-dried LLM. Growth rate, feed intake and feed conversion efficiency were not affected by the addition of water-soaked and FeS04-treated LLM to the basal diet. Triiodothyronine (T3) and thyroxine (T4) levels in the blood plasma were not affected by the dietary treatments. However, addition of FeS04-treated LLM to the basal diet significantly (P<0.05) decreased the back fat thickness of the pigs. In the metabolic study, the digestible dry matter (DDM) and digestible CP (DCP) were measured as well as mimosine, 3-hydroxy-4-(1H) pyridone (3,4-DHP) and 2,3DHP output in the faeces and urine.
Addition of water-soaked LLM to the diet significantly (P<0.05) lowered the DDM of the diet, whereas addition of FeS04-treated LLM significantly (P<0.05) reduced the DCP. Sun-drying, water-soaking and treatment of LLM with FeS04 solution, did not enhance the output of mimosine or 3,4-DHP in the urine and faeces. The results suggest that water soaking or treatment with FeS04 solution reduces the antinutritional factors (presumably including mimosine) and therefore improves the nutritional quality of LLM containing diets for pigs.

Fiber-rich (HF) diets are typically supplemented with enzymes to improve their nutritive value and to offset their negative effects on pig growth. However, studies on enzyme effect in pigs have yielded inconsistent results on nutrient digestibility and growth. Although the inconsistencies observed could be explained by differences in substrate and experimental conditions and enzyme characteristics among studies, how enzymes influence metabolic and physiological responses in pigs is still not clear. Therefore, three experiments were conducted, using 3 dietary treatments (control, HF and HF diet supplemented with enzymes), to elucidate the effects of supplementing an HF diet with enzymes in growing pigs. Experiment one investigated HF and enzyme supplementation on energy and nutrient digestibility, digesta volatile fatty acid (VFA) concentrations, and gut microbial profile in pigs. Compared with the HF diet, enzymes improved dry matter, starch, energy and some amino acid (AA), but not nitrogen digestibility. Further, the enzymes stimulated the growth of gut bacterial groups, which have xylanolytic and cellulolytic properties in the HF-fed pigs, but enzymes did not influence digesta VFA concentration or fiber fermentation. Experiment 2 evaluated the effects of enzyme supplementation on growth performance, glucose uptake in jejunum tissue samples mounted in Ussing chambers, and intestinal nutrient transporter mRNA levels in pigs. Diet had no effect on feed intake and jejunal glucose uptake. The enzymes influenced nutrient transporter mRNA levels but did not improve pig growth rate and feed efficiency relative to the HF diet. The third experiment investigated the effect of supplementing the HF diet with enzymes on postprandial portal vein-drained viscera (PDV) nutrient fluxes and energy expenditure (measured as O2 consumption) by the PDV and whole-animal in pigs. Diet had no effect on energy expenditure. The HF diet reduced portal glucose, VFA and essential AA absorption and insulin production. Enzyme supplementation improved portal glucose and VFA absorption, but not essential AA absorption and insulin production. Overall, improvements in nutrient utilization due to enzyme supplementation did not improve the growth rate of pigs, which appears to be due to the lack of enzyme effect on essential AA and energy use by the PDV and insulin production
October 2016

Le phosphore (P) des aliments pour les porcs est partiellement retenu (30-35%) en raison de l’absence de phytase endogène dans leur tube digestif ; le restant étant excrété et potentiellement à risque pour l’environnement par des phénomènes d’eutrophication. Il est ainsi courant d’ajouter des phosphates dans les aliments pour combler les besoins en P, lesquels constituent une ressource naturelle limitée et parfois coûteuse. Ainsi, la réduction du P alimentaire est prioritaire pour la production porcine depuis plusieurs années. Une des voies pour y arriver est l’augmentation de son efficacité d’utilisation par l’animal. Cette augmentation peut être liée aux modifications nutritionnelles (ex. : phytases exogènes) ou aux adaptations digestives et métaboliques de l’animal en réponse à une carence soit par exemple en utilisant des stratégies de déplétion-réplétion. Ceci consiste à alimenter un animal au-dessous de ses besoins en P durant une certaine période (déplétion) et avec un aliment non carencé (réplétion) par la suite. L'impact d’une telle stratégie sur les performances de croissance, la minéralisation osseuse, les propriétés mécaniques des os, la concentration plasmatique de P et Ca et des transporteurs intestinaux et rénaux liées au métabolisme phosphocalcique ont été étudiés dans la présente thèse. Deux essais ont été effectués avec des porcs en croissance recevant un régime témoin (C) avec des apports adéquats de P et Ca ou un régime faible (L) apportant 60% des besoins. Dans le premier essai, 60 mâles castrés [poids vif (PV) initial 14 ± 1,6 kg] ont été alimentés pendant quatre phases de 28 jours avec différentes séquences d’alimentation [CCCC, CLCC, CCLC, CCCL, LCLC ou LLLL]. Dans le deuxième essai, 80 mâles castrés [PV initial 24 ± 3,0 kg] ont été alimentés pendant trois phases de 28 jours avec les séquences suivantes : CCC, CLC, LCC, LLC ou LLL. Dans les deux essais, la consommation journalière individuelle moyenne d’aliment et le poids vif ont été enregistrés et le corps entier et vertèbres lombaires (L2-L4) scannées au début et à la fin de chaque phase de croissance par absorptiométrie aux rayons X (DXA) afin de mesurer leur teneur corporelle en protéines, lipides, P et Ca ainsi que leur contenu minéral osseux (CMO) et densité minérale osseuse (DMO). Des échantillons de sang ont été prélevés pour déterminer les concentrations plasmatiques de P, Ca et vitamine D3 ainsi que des échantillons post-mortem de jéjunum et de rein afin d'étudier l'expression génique et protéique des transporteurs de P, Ca et vitamine D3. Le fémur et le métacarpe ont été aussi collectés pour étudier leurs propriétés mécaniques par des tests de flexion. Le P digestible et le Ca total ont été déplétés respectivement de 36% et 22% dans le premier essai. Dans cet essai, la déplétion a réduit la minéralisation osseuse et les performances de croissance des animaux CCCL et LLLL et les porcs réplétés CCLC ont présenté des performances similaires aux CCCC. Les porcs CCLC et CLCC ont récupéré leur contenu minéral osseux (CMO) à la fin de l'essai grâce à une utilisation plus efficace de P et Ca alimentaires. Dans le deuxième essai, la réduction du P digestible et Ca total alimentaire a été de 35% et 42%, respectivement. La déplétion dans cet essai a réduit les performances de croissance, le CMO et les propriétés mécaniques des os. Dans la dernière période, l’efficacité d’utilisation du Ca alimentaire a été supérieur chez les porcs LLL mais inférieur chez les animaux réplétés (CLC, LCC et LLC) par rapport aux CCC, et donc n’ont pas pu rattraper la minéralisation à la fin de l’expérience. Comparativement aux porcs témoins, les transporteurs intestinaux et rénaux de Ca des porcs déplétés ont été surexprimés dans la deuxième phase, tandis que ceux du P ont été sous-exprimés chez les réplétés, soit une réponse de type parathormone. Les différents os du squelette répondent différemment aux modifications alimentaires de P et Ca, avec notamment les vertèbres qui sont plus sensibles à la déplétion-réplétion en P comparativement au squelette entier. Les performances de croissance, les propriétés mécaniques des os et la concentration plasmatique de P et Ca ne sont pas de bons indicateurs de la minéralisation corporelle. En somme, une déplétion en P alimentaire améliore son utilisation digestive et métabolique, laquelle peut être maintenue même pendant la réplétion. Cependant, une carence similaire ou plus importante en P qu’en Ca semble nécessaire pour engendrer des adaptations menant à une meilleure efficacité d’utilisation de P. En conclusion, la déplétion-réplétion en P est une stratégie prometteuse pour réduire le P alimentaire mais demande d’être encore affinée, notamment par une meilleure compréhension des régulations.
Phosphorus (P) in pig feed is partially retained (30-35%) due to the absence of endogenous phytase in its digestive tract; the remainder being excreted and potentially at risk for the environment by eutrophication phenomena. It is thus common to add phosphates in feed to fulfill P requirements, which constitutes a limited and sometimes costly natural resource. Thus, the reduction of dietary P supply has been a priority for the pig production industry for several years now. One way to achieve this objective is to increase its utilization efficiency by the animal. This increase may be related to nutritional changes (e.g., exogenous phytases) or to digestive and metabolic adaptations of the animal in response to dietary deficiencies such as the depletion-replication strategy. This involves feeding an animal below its P requirements for a certain period (depletion) followed by a non-deficient diet (repletion) thereafter. The impact of this strategy on growth performance, bone mineralization and mechanical properties, plasmatic P and Ca concentration and intestinal and renal transporters related to phosphocalcic metabolism have been studied in this thesis. Two trials were performed with growing pigs receiving a control (C) or a low (L) diet, which supplied 100% and 60% of the P-Ca requirements, respectively. In the first trial, sixty castrated male pigs (initial body weight (BW) 14 ± 1.6 kg) were fed during four 28-days feeding phases with different feeding sequences [CCCC, CLCC, CCLC, CCCL, LCLC or LLLL]. In the second trial, 80 castrated male pigs [initial BW 24 ± 3.0 kg] were fed during three 28-days phases with the following sequences: CCC, CLC, LCC, LLC or LLL. In both trials, individual average daily feed intake and weekly BW were recorded, and whole-body and lumbar vertebrae (L2-L4) were scanned at the beginning and at the end of each growing phase with dual-energy X-ray absorptiometry (DXA) to measure whole-body mineral, protein, lipid, P and Ca contents and bone mineral content and density (BMC, BMD; respectively). Blood samples were collected to determine P, Ca and vitamin D3 plasmatic concentrations, and samples of mid-jejunum and kidney were collected post-mortem to study the gen and protein expression of P, Ca and vitamin D3 transporters. Moreover, femur and metacarpal were also collected to study their mechanical properties by the bending test. In the first trial digestible P and Ca depletion was 36% and 22%, respectively. Depletion of this trial reduced bone mineralization and growth performances of CCCL and LLLL pigs, and CCLC pigs had similar performances than CCCC pigs. Both CCLC and CLCC pigs recovered BMC at the end of the trial as a result of a higher dietary P and Ca utilization efficiency. In the second trial, dietary digestible P and Ca reduction was 35% and 42%, respectively. Depletion in this trial reduced growth performance, BMC and bone mechanical properties. In the last phase and compared to control pigs, the utilization efficiency of dietary Ca was higher in LLL and lower in repleted pigs (CLC, LCC, LLC) which were not able to recover bone mineralization at the end of the trial. Compared to control pigs, the intestinal and renal Ca transporters of depleted pigs were overexpressed in the second phase, whereas those of P were under-expressed in the repleted pigs, probably due to the synthesis of parathormone. The different bones of the skeleton respond differently to dietary P and Ca modifications, where vertebrae are more susceptible to P depletion-repletion compared to the whole skeleton. Growth performance, bone mechanical properties and plasma concentration of P and Ca are not good indicators of body mineralization. In summary, a depletion in dietary P improves its digestive and metabolic utilization, which can be maintained even during repletion. However, a similar or greater deficiency in P than in Ca seems necessary to develop adaptations leading to a better P utilization efficiency. In conclusion, a dietary P depletion-replication is a promising strategy for reducing P supply but further refinement is needed, in particular through a better understanding of the regulations involved.

Three balance experiments were conducted to determine the effects of dietary fiber on mineral balance and intestinal.morphology of growing pigs. Fiber sources were added to corn-soybean meal diets at levels which increased neutral-detergent fiber levels by 6 to 8%. In experiment 1, 10% oat hulls (OH) decreased Ca (P<.06) and Zn (P<.01) balances of pigs after a 7 d feeding period. Wheat bran (20%) increased Mg intake and balance (P<.02), but did not affect Ca and Zn balances. In experiment 2, pigs were fed diets (with or without supplements of Zn, Fe and Mg) containing 15% OH or soybean hulls (SH) for 5 d or 26 d. SH increased Fe intake and balance (P<.01) and ( Mg absorption (P<.01). Compared with balances at 5 d, Zn balance was similar, while Fe and Mg balances were higher at 26 d for pigs fed the basal (P<.05) or SH (P<.01) diets. However, Zn balance was lower (P<.05) at 26 d 1 but Fe balance did not change over time for pigs fed the OH diets. At each time period, Zn balance was not different between pigs fed the basal or high-fiber diets. In experiment 3, Ca, Zn and Mg absorption were not affected by 15% OH or SH or 20% alfalfa meal (AM) after 67 d or 39 d, although SH and AM increased Fe balance (P<.01). Intestinal surface morphology of 12 pigs fed in experiment 3 was examined by scanning electron microscopy. Villus morphology was variable in jejunum, ileum and colon, although evidence of villus blunting and folding accompanied by erosion of microvilli and loss of epithelial cells was observed in small intestine of some pigs fed the SH and AM diets. Damage was not consistent in all sites examined in individual pigs, and did not occur in all pigs fed any specific diets. Although Ca and Zn balances were decreased by OH in two of the balance trials, the inability of OH to consistently decrease mineral balance suggests that the ability of the pig to adapt to different diets may be sufficient to overcome the mild inhibitory effect on mineral absorption of some fiber sources. When viewed together, the results of the balance trials indicate that moderate amounts of dietary fiber have a minimal negative impact on mineral balance of pigs fed practical corn-soybean meal diets. However, the results also indicate that fiber sources such as SH and AM, are rich sources of some minerals for the pig, particularly Fe. Evidence of intestinal damage was evident in pigs fed the high-fiber diets. However, not all animals fed a particular diet were affected, which suggests that some pigs within a given population may be susceptible to detrimental effects of dietary fiber on intestinal structure or function.
Ph. D.

Minimising variability in carcass quality to better meet market specifications is a priority for Australian pig producers, however issues with variability in carcass fat distribution have recently been raised, particularly in the belly primal. There has been a rapid increase in the use of low-cost, deep-litter (DL) housing systems in Australia over the past 15 years for rearing pigs. The inherent differences between the physical, thermal, and social environments of conventional (C) and DL production systems may well alter the growth path of the pig and subsequently alter fat metabolism and hence fat deposition and distribution. The general industry view is that pigs finished in DL housing are fatter and grow less efficiently than pigs finished in C housing, however contrasting carcass and growth performance results have been reported between housing systems. It is likely that the different housing environments affect the maintenance energy requirements of the growing pig, thereby affecting the availability of substrates for fat deposition and/or the requirements for fat mobilisation. Hence, raising pigs in C and/or DL production systems was identified as a likely contributor to variability in carcass fat distribution via the effects of the disparate environments on fat metabolism. The overall purpose of this thesis was to establish the effect of keeping pigs in C and/or DL housing systems on fat metabolism, and therefore fat deposition in the growing pig and fat distribution in the finished carcass. Industry considers that finishing pigs in C facilities allows greater flexibility in feeding and marketing decisions, allowing growth efficiency and backfat to be managed more effectively than in a DL system. Therefore an aspect of this thesis was to also examine the effects of an alternative management strategy, raising pigs in a combination of DL and C housing, on growth performance and fat deposition and distribution in the carcass. The presence of straw bedding is a major difference between C and DL housing systems. This was identified as a probable contributor to the differences in growth performance and carcass fat distribution found between pigs raised in the different housing systems, via its thermal properties and/or the ingestion of the straw on pig growth. Experiment 1a and 1b were designed to test the hypothesis that the growth path differs for pigs raised in C and DL housing systems, affecting biochemical indicators of fat metabolism and therefore fat accretion and distribution in the carcass. The study was conducted as a serial slaughter of pigs housed in C and DL systems allowing the pattern of fat accretion, and therefore the distribution of fat in the carcass, to be determined from 15¨C185 kg live weight (LW). The results confirmed the hypothesis that the growth path, fat accretion and fat distribution in the carcass differed for pigs raised in C and DL housing systems. In Experiment 1a, elevated lipogenic enzyme activities, higher percentages of saturated fatty acids (SFA) and higher concentrations of plasma glucose and lactate indicated lipogenesis was elevated in C pigs to 13 weeks of age, compared to young DL pigs, suggesting that fat accretion was higher in young C pigs. At 24 weeks of age however there was a shift in lipogenic enzyme activities, the percentage of SFA in backfat and the concentration of plasma glucose were higher in DL-housed pigs than C-housed pigs, indicating higher rates of lipogenesis. Elevated concentrations of plasma non-esterified fatty acids (NEFA) and glycerol in DL pigs indicated that lipolysis, or fat mobilisation, was higher in DL-housed pigs for the entire growth period. The results from Experiment 1b clearly indicated that during early growth, C pigs grew faster than DL pigs (0.71 vs 0.66 kg/day, P¡Ü0.05) and were heavier between 8-23 weeks of age (P¡Ü0.05). Therefore in conjunction with the results of Experiment 1a, it was expected that young C pigs would be fatter than DL pigs of the same age. However, dissection indicated no treatment differences in total carcass composition, although there was an effect of housing on carcass fat distribution with a trend (P=0.087) for a lower ratio of fat:lean in the belly primal of DL pigs compared to C pigs at 13 weeks of age. After 20 weeks of age however, growth rates were similar for pigs in both housing treatments and by 26 weeks of age there were no treatment differences in live weight (LW) but the rate of fat accretion in DL pigs, particularly in the loin and belly primals, increased rapidly. Differences in the thermal environments of C and DL housing, and therefore differences in the energy demand for thermoregulation, were likely to have contributed to the differences measured in lipogenesis, growth performance and carcass fat distribution. Experiment 2a and 2b tested the hypothesis that moving pigs from DL to C housing for finishing would improve overall growth performance and reduce carcass fatness compared to pigs raised in wean-to-finish DL housing. The biochemical measurements indicated few differences in the rate of lipogenesis between 13-week-old C and DL pigs. However, and in agreement with the findings from Experiment 1a, elevated plasma NEFA concentrations in DL pigs suggested higher rates of lipolysis. Up to 13 weeks of age, pigs in the DL housing system grew faster than C pigs, however similar to the findings of Experiment 1b, DL pigs were less efficient. In addition, P2 backfat depth was less in DL pigs, indicating they were leaner than C pigs, and though not reflected in total carcass composition, again there was an effect of housing on fat distribution. The move to an unfamiliar housing environment affected growth performance, reduced enzyme activity in backfat and the ratio of SFA in belly fat, suggesting these pigs had lower rates of lipogenesis. However in contrast to Experiment 1a, where lipogenesis was higher in older DL pigs compared to older C pigs, pigs finished in the DL housing had a trend for lower enzyme activity in belly fat (P=0.063), suggesting lower rates of lipogenesis, and higher plasma glycerol concentrations, suggesting a higher level of lipolysis compared to C-finished pigs. The carcass composition data (Experiment 2b) found that though there were no differences indicated by differences in P2 depth, there was a strong trend (P=0.057) for DL-finished pigs to have 2-6% less fat in the carcass as a result of significantly less fat in the shoulder (15% vs 17%) and belly (29% vs 33%) primals compared to C-finished pigs. The difference in belly primal composition was a reflection of the lower enzyme activities in belly fat and higher plasma glycerol concentrations in DL finished pigs. The results suggest that the type of housing during the finishing growth period has a greater impact on fat accretion and carcass composition than the type of housing during the grower period, or changing housing environment during growth. However, changing housing environment at 13 weeks of age affected growth, where there was a temporary reduction in daily LW gain, and therefore significantly lower (P¡Ü0.001) LW at slaughter (117 kg LW), compared to pigs that had remained in C or DL housing from wean-to-finish (123 kg LW). Moving pigs from DL to C housing to control carcass fat and improve growth performance compared to pigs grown wean-to-finish in DL housing, was not successful, and had a negative impact on performance and carcass quality by reducing growth efficiency and LW and increasing carcass fatness. The results also showed that contrary to the industry view that DL raised pigs are fatter, pigs in this experiment finished in DL housing had a lower fat:lean ratio in the carcass than pigs finished in the C system (P¡Ü0.05). The effects of straw on growth performance and carcass composition were evaluated in Experiment 3a and 3b by including straw in the grower and finisher diets (St+) and/or providing straw bedding (Bed+) to C-housed pigs. The experiment tested the hypothesis that the presence of straw alters the growth paths of pigs, affecting fat distribution in the carcass. Straw, as bedding and in the diet, affected pig growth paths and altered carcass fat distribution and, consistent with the findings for DL pigs in Experiments 1b and 2b, there was a trend for pigs with access to straw to have less fat in the belly (P=0.072). Elevated activity of key enzymes involved in lipogenesis, measured in Experiment 3a in belly fat and backfat from pigs fed the St+ diet, and a higher ratio of SFA in belly fat of pigs housed on concrete without straw bedding, suggested that in this experiment straw ingestion increased lipogenesis in belly fat and backfat of the growing pig, whilst straw bedding reduced lipogenesis in belly fat. Experiment 3b demonstrated an additive effect of straw on growth where average LW at slaughter for pigs without access to straw was significantly lower (110 kg), compared to pigs with access to one source of straw either via the diet or bedding (115 and 114 kg LW respectively), and pigs that had two sources of straw available (119 kg LW) (P¡Ü0.05). Although LW differed between treatments there were no differences in total carcass fat (P>0.10), yet there was an effect of straw on fat distribution. Pigs with access to straw had a lower ratio of fat and a higher ratio of lean tissue in the belly primal (P=0.072) compared to pigs that did not have straw. The effect of straw ingestion on lipogenesis and fat deposition may have occurred via the effects of dietary fibre (DF) on the dilution of dietary energy density. Pigs were able to compensate for the energy/nutrient dilution by increasing VFI and therefore growth was not affected, however fat acts as an insulator, and localised differences in fat distribution may have been related to increased heat production (HP) from the digestion of greater volumes of feed. In response, fat deposition may have been directed away from the belly location in order to facilitate heat loss. Floor type may have also affected fat distribution via differences in thermal conductivity. Straw has a lower thermal conductivity than concrete, hence pigs housed on concrete flooring may have a greater requirement for fat in the belly to reduce conductive heat loss. Results from Experiment 3a and 3b provided evidence that pigs housed on bedding consume straw in sufficient quantities. Pigs fed the straw diet had significantly higher concentrations of plasma acetate than pigs fed the control diet (P¡Ü0.001), and there was a trend for pigs housed on straw bedding to have higher levels than pigs without access to straw. An increase in plasma acetate can indicate increased microbial activity in gut, which occurs in response to higher levels of DF. In addition, pigs bedded on straw had higher gastrointestinal tract weights, which can also indicate higher levels of DF intake. Regression analyses of data across experiments showed that P2 backfat depth, the primary carcass composition prediction tool, accounted for less than 50% of the variation in percent carcass fat (R2=0.41). Furthermore, across experiments, P2 accounted for very little of the variability in percent belly fat (R2=0.01). These results highlight the inconsistency of P2 depth as a reliable indicator of carcass composition and the need for the development of additional criteria to be used in the selection of carcasses for specific markets as the composition of the belly primal was not indicated by the current carcass measurement system. From the results obtained in this thesis, it was proposed that: 1) The growth path of pigs is altered by the housing system in which they are reared and the more variable ambient temperature of the DL housing system would increase the energy requirement of young pigs for thermoregulation. As a consequence of the altered growth paths, fat metabolism differs for pigs raised in DL and C production systems. Lower rates of lipogenesis may occur in young DL pigs compared to C pigs and this can change as pigs grow, however fat mobilisation remains higher in DL pigs during growth. 2) Differences in the rate of lipogenesis, indicated by the biochemical measures, were generally not reflected in total carcass composition, however there were differences in carcass fat distribution where pigs raised in DL systems consistently had less fat in the belly primal. Rearing environment may provide an additional criterion when selecting carcasses for specific markets where variability in belly composition is an issue. 3) Pig raised in the DL environment are not always fatter than pigs housed in C facilities, and moving pigs from one housing environment to another during the growing-finishing period disrupts the growth path reducing growth performance and can increase carcass fatness. 4) Straw bedding, via ingestion and via its physical thermal properties, affects pig growth and fat distribution and may explain in-part the differences in pig growth performance and carcass quality found between C and DL housing systems.