243 research outputs found
Selection for growth, muscling and fatness alters the maternal performance and intermediary metabolism of Merino ewes
No full textThere is growing interest in selectively breeding Merinos with higher growth and muscling and lower fatness. The effects of selection for these traits on ewe intermediary metabolism, body composition, reproduction and milk production and on lamb birthweight, survival and growth were studied in a series of experiments and analyses.
Ewes with higher genetic propensity for early growth had higher mature weight, reproductive rate, lamb birthweight, ewe milk production and lamb growth rate. Ewes with higher growth also had a higher circulating level of growth hormone during lactation.
Ewes with higher genetic propensity for muscling had a higher reproductive rate and produced lambs that were lighter at birth, but this did not result in lower lamb survival. Ewes with higher muscling maintained a higher condition score which may be at least partly attributed to a lower response to adrenaline at the level of the muscle in these higher muscled ewes. Similarly higher muscled ewes had lower growth hormone concentration in lactation which would result in lower mobilisation of tissues. In addition peripheral tissues were less responsive to insulin in high muscled ewes and blood glucose levels were also higher during the non-breeding state in high muscled ewes.
The genetic fatness of ewes was positively associated with lamb birthweight but only when nutrition was restricted suggesting that ewes with a higher genetic propensity for fatness can buffer lamb birthweight under periods of poor nutrition. Ewes with higher genetic fatness had lower circulating growth hormone and a greater response to insulin providing potential mechanisms for the observed higher fatness. Furthermore, response to adrenaline at the level of liver was greater in ewes with higher fatness suggestive of a higher capacity for gluconeogenesis. The combined results of this work suggest that actively selecting Merino ewes to have higher growth, muscling and fatness is likely to have positive reproduction and therefore economic outcomes
Selection for muscling affects carbohydrate and fatty acid metabolism in beef cattle
No full textGenetic selection to enhance muscularity in beef cattle is desirable to increase retail beef yield and the profitability of the beef industry. However it is unknown how selection for greater muscling will impact on intermediary and muscle energy metabolism which may influence certain attributes of meat quality. In order to assess these impacts of selection for greater muscling in cattle, the physiological mechanisms that underpin the increase in retail beef yield must be identified. This thesis examined the impact of selection for greater muscling on: retail beef yield; muscle glycogen; whole body insulin responsiveness; adrenaline responsiveness of muscle, adipose and liver tissue; and proportion of glycolytic and oxidative myofibres and enzyme activities. This study used 11 high (High), 10 low (Low) and 3 high muscled steers with a myostatin mutation (HighHet) from an Angus herd which had been visually selected for divergence in muscling over 15 years.
The results of the yield test performed at bone-out showed that the HighHet and High muscled steers were the highest yielding with the lowest proportion of fat, while the Low muscling animals were the lowest yielding with the highest proportion of fat. Muscle glycogen and lactate concentration were analysed from four muscle biopsies, taken between 18 and 24 months of age, from the m. semimembranosus (SM), m. semitendinosus (ST) and m. longissimus thoracis et lumborum (LTL) of each animal. The muscle glycogen concentrations which were 6.1% higher in the High steers compared to the Low animals while the HighHet did not differ from either group.
The effect of selection for muscling on whole body insulin responsiveness was measured using the hyperinsulineamic-euglyceamic clamp technique. Insulin was constantly infused at 2 levels, glucose was concurrently infused to maintain euglyceamia, and the steady-state glucose infusion rate (SSGIR) indicated insulin responsiveness. At the low insulin infusion rate of 0.6 mU/kg/min, the SSGIR was 73% higher for the High muscling genotype animals when compared to the Low. At the high insulin infusion rate of 6.0 mU/kg/min, these differences were proportionately less with the High and the HighHet genotypes having only 27% and 34% higher SSGIR than the Low muscled genotype. The High muscled cattle also had 30% higher plasma IGF-1 concentrations compared to the Low muscled cattle. The increased whole body insulin responsiveness in combination with higher IGF-1 concentrations in the High muscled steers is likely to initiate a greater level of protein synthesis, which may partially explain the increased muscle accretion in these animals. Increased insulin responsiveness in the High steers would also increase glycogenesis in the muscle, aligning with the glycogen results.
The effect of selection for muscling on adrenaline responsiveness was measured using 7 adrenaline challenges ranging between 0.2 to 3.0 μg/kg liveweight. Plasma was analysed for NEFA, lactate, glucose and growth hormone concentration and area under curve (AUC) over time was calculated to reflect the tissue responses to adrenaline. The High steers had 30% lower lactate AUC than the Low steers at challenges greater than 2 μg/kg live weight, indicating lower muscle responsiveness at the highest adrenaline doses causing less glycogenolysis. This result also aligns with these animals having more muscle glycogen, thus more muscular animals may reduce the incidence of dark, firm, dry meat that is caused by low levels of glycogen at slaughter. At all levels of adrenaline challenge the High steers had at least 30% greater NEFA AUC, indicating that their adipose tissue was more responsive to adrenaline, resulting in greater lipolysis. In agreement with this response, the High steers had a higher plasma growth hormone concentration, which is likely to have contributed to the increased lipolysis evident in these animals in response to adrenaline. This difference in lipolysis may in part explain the reduced fatness of muscular cattle. There was no effect of selection for muscling on liver responsiveness to adrenaline.
Contrary to our initial hypotheses, the High steers had less glycolytic type IIX myofibres in the LTL and larger average cross-sectional area of myofibres in the SM and ST than their Low muscled counterparts. This suggests that myofibre hypertrophy may be a possible mechanism leading to greater muscle mass of these High muscled animals. This also indicates that breeding for more muscular cattle can actually maintain the oxidative capacity of the muscle, a finding supported by the enzymatic results showing that the High muscled steers had lower activity of lactate dehydrogenase and higher activity of citrate synthase and isocitrate dehydrogenase. The High muscled cattle also had a higher concentration of iron in the LTL, and selection for increased muscling had no impact on pH decline or retail colour stability, factors which both affect meat quality.
The aim of the second experiment was to determine if phenotypic measurements taken at the time of grading for Meat Standards Australia (MSA) could explain variance in ultimate pH (pHu) of carcasses and the probability of a carcass complying with MSA standards for pHu (≤5.7). Analyses of 204,072 carcass records collated by MSA at a Western Australian processor confirmed that more muscular cattle have a higher compliance rate for pHu. An increase in eye muscle area from 40 to 80 cm2, increased pHu compliance by approximately 14%. Therefore animals with greater muscularity had a lower incidence of dark, firm, dry beef supporting the results that High muscled cattle have increased insulin responsiveness, and reduced adrenaline responsiveness, leading to increased glycogen storage at slaughter. Thus, breeding more muscular cattle with eye muscle area greater than 70 cm2 may help alleviate the problem of dark, firm, dry beef. As rib fat depth increased from 0 to 20mm, pHu compliance increased by around 10%. Heavier cattle also had higher compliance than lighter cattle, and younger cattle also had higher compliance rates. This highlights the importance of good nutrition and high muscle glycogen storage prior to slaughter to maximise compliance rates.
The final study examined 81 commercially managed High and Low muscled steers and showed that the effects of muscularity on muscle glycogen were variable as pasture quality and availability changed however there were no negative effects of selection for greater muscling on muscle glycogen, glycogenolysis pre-slaughter, or on the incidence of dark, firm and dry carcasses. Animal temperament assessed using crush score and flight speed measurements did however affect muscle glycogen with the more flighty animals having lower muscle glycogen concentrations
Amateur: Wendelien van Oldenborgh
No full textEdited by Emily Pethick and Wendelien van Oldenborgh with David Morris
Amateur is the first comprehensive publication about Wendelien van Oldenborgh’s moving image works, and their accompanying installations. Developed over the past ten years of her practice, these works explore communication and interaction between individuals, often against the backdrop of a unique public location, in order to cast attention on repressed, incomplete, and unresolved histories. Through the staging of these encounters on film, van Oldenborgh enables multiple perspectives and voices to coexist, and brings to light political, social, and cultural relationships and how they are manifested through social interactions.
The publication is generously illustrated and brings together a wealth of texts by artists, curators, and writers who have been key interlocutors with van Oldenborgh, and who each offer in-depth observations and reflections on a work from her oeuvre. These authors include Nana Adusei-Poku, Ricardo Basbaum, Frédérique Bergholtz, Eric de Bruyn, Binna Choi, David Dibosa, Denise Ferreira da Silva, Avery F. Gordon, Tom Holert, Nataša Ilić, Charl Landvreugd, Sven Lütticken, Anna Manubens, Ruth Noack, and Grant Watson
The Physiology of marbling: What is it, and why does it develop
No full textThis review describes our current understanding of the factors affecting growth and development of adipocytes in bovine skeletal muscle and discusses alternative hypotheses to explain intramuscular fat deposition: marbling. While genetic predisposition clearly plays a role in the development of this commercially interesting phenotype, animal age, energy nutrition, vitamin nutrition, compensatory growth and previous growth rate may also contribute to the final outcome. The review briefly analyses the data supporting each hypothesis and attempts a mechanistic description based on the development of tissue precursor cells into mature adipocytes. Properties of the mature adipocyte in the context of whole animal and muscle biochemistry are discussed in the companion paper by Pethick et al. (2001)
Classification of sheep category using chemical analysis and statistical classification algorithms
No full textIn Australia, dentition (eruption of permanent incisors) is used as a proxy for age to define sheep meat quality. Lamb is defined as having no permanent incisors, hogget as having at least one incisor and mutton is defined as having two or more incisors. Classification of the carcase is done at the abattoir prior to the removal of an animal’s head. Recently, an Australian Senate inquiry into meat marketing reported that there was concern that substitution of hogget and mutton for lamb may be occurring in the industry. At present, no objective method is available that can be used for classifying sheep category. The general aims of this thesis were to i) evaluate whether chemical analysis of branched chain fatty acid (BCFA) content could be used as an objective tool to determine sheep age, ii) understand the effect that some production factors had on BCFA concentrations in Australian sheep and iii) develop new approaches (whether chemical and/or statistical) for determining sheep category (age).
BCFAs are implicated as the main contributors to “mutton flavour”, often associated with the cooked meat of older animals. BCFAs are reported to increase with age, which suggests that chemical analysis of these compounds could be used as an objective method. Concentrations of three BCFAs (4-methyloctanoic (MOA), 4-ethyloctanoic (EOA) and 4- methylnonanoic (MNA) acids) were measured in a survey of fat samples taken from 533 sheep carcases at abattoirs in New South Wales, Victoria and Western Australia. This thesis shows that, on its own, chemical analysis of the BCFAs is not sufficient to discriminate lamb from hogget and mutton as pre-slaughter nutrition is a significant factor in classifying sheep using this approach. Uncertainty at the BCFA concentration ranges found in Australian sheep was determined to be high making it difficult to discriminate between sheep carcases of different ages based on the BCFA level.
Fast gas chromatography was evaluated as the basis for a high throughput chemical technique but was not sufficiently sensitive for BCFA measurements. Solid-phase microextraction (SPME) was also found to be suitable for sampling 3-methylindole and p-cresol, compounds responsible for diet-related “pastoral flavour” in sheep fat, but further work is needed to validate this approach for measurement of these compounds in sheep fat.
Statistical classification algorithms, when applied to the chromatograms measured for the 533 carcasses, showed great promise for predicting sheep category. Specifically, the random forests algorithm, when applied to mean-centred data, gave 100% predictive accuracy when differentiating between lamb, hogget and mutton. This approach could be used for the development of an objective method for determining sheep age and category, suitable for use by the Australian sheep meat industry
Sheep Updates 2003 - Meat
No full textThis session covers seven papers from different authors: 1. Economic analysis of using terminal sires in a self replacing Merino flock Lucy Anderton, Department of Agriculture Western Australia, Katanning 2. Is the mating of ewe weaners an option for increasing the numbers of lambs in WA? Rob Davidson University of WA, Crawley and Keith Croker Department of Agriculture Western Australia, South Perth 3.Dehydration of lambs at the time of slaughter Robin Jacob, School of Veterinary and Biomedical Sciences, Murdoch University 4.Feeding prime lambs for slaughter Rachel Kirby, Outback Solutions 5. Live sheep export R&D Steve Meerwald, Wellard Rural Exports 6. Confinement feeding sheep in Western Australia John Milton, The University of Western Australia 7. Sheepmeat eating quality - affects of animal age, finishing and processing David Pethick, School of Veterinary and Biomedical Sciences, Murdoch Universit
Carcass and eating quality of sheep grazing saltbush based saline pasture systems
No full textForage halophytes such as saltbush (Atriplex spp) are being widely used to revegetate Australian saline land and can also provide a medium quality fodder source. There is widespread anecdotal evidence that sheep grazing on saltbush are leaner, tastier and juicer. This thesis investigated the potential to produce a high quality carcass with improved eating quality from grazing sheep on saltbush on saline land.
The first experimental chapter in this thesis details an animal house experiment investigating the carcass, eating and wool quality and physiological responses of sheep ingesting a 60:40 dried saltbush (Atriplex nummularia):barley grain (S+B), ration verses a 33:25:42 lupin grain:barley grain:oaten hay ration (Control, C) for 10 weeks prior to commercial slaughter (Chapter 4). Subsequently, two field experiments were conducted to examine the effects of grazing saltbush on saline land compared to dry senesced pasture on carcass and eating quality of lambs (Goomalling 2003) and hoggets (Wickepin 2004) (both chapter 6) for 14 weeks. Both chapters demonstrated that the ingestion of saltbush resulted in significantly less fat and in the 2 field experiments the ingestion of saltbush resulted in more lean on the carcass compared to sheep grazing a stubble/pasture (control) ration. These are positive findings for processors as costs of fat denudation are high so the lower the fat content and for farmers because less fat is deposited on the carcass per unit of liveweight gain. The decreased deposition of fat was attributed to the higher protein:energy ratio available for production, secondary compounds in saltbush and lower circulating insulin and higher growth hormone of the S+B fed sheep compared to the control fed sheep. Further work is needed to determine if these beneficial improvements in carcass composition can be achieved without compromising animal production. The long term grazing of saltbush did not result in commercially desirable hot carcass weights unless the sheep were supplemented with a high energy source such as barley. The low growth rates are attributed to a decreased availability of energy substrates, low feed intake and increased energy output of sheep fed high salt diets. The low energy intake of the S+B fed sheep also resulted in an a significantly lower percentage of unsaturated fat and unchanged levels of saturated fat in the fat depots compared to the C treatment.
Consumer taste tests conducted on meat from experiments in both chapter 4 and 6 indicated no difference between the treatments for any of the eating quality traits assessed. This can be considered a positive result as sheep can be finished on saltbush without any detriment to eating quality. High vitamin E levels in the meat may have also prevented the development of rancid flavours and aroma. It can be speculated that saltbush does not impart beneficial flavour and aroma volatiles as previously thought; instead the high vitamin E levels inhibit off-flavour and aroma development compared to meat from sheep grazed on dry pasture.
The long term ingestion of saltbush also resulted in significantly lower urine specific gravity (USG), muscle dry matter and higher urine weights suggesting that the saltbush fed sheep had a better hydration status compared to control fed sheep. However, this finding did not correspond with higher hot carcass weight or dressing percentages. The increases in muscle fluid content of the saltbush fed sheep were attributed to changes in body composition. The saltbush fed sheep had a higher lean and lower fat content which corresponded with a greater body fluid content as found in the animal house study.
Under conditions where the body composition of sheep remains the same, the use of short term strategic feeding of components of saltbush was investigated (mimicked in the form of salt and betaine) to reduce dehydration and subsequent reductions in carcass weight and dressing percentages (Chapter 7). Salt and or betaine were fed for 1 week either prior to a 48 h period of water deprivation or prior to 48 h commercial slaughter process where water was available in lairage from 24-48 h. Under both scenarios the diets did not result in improved dressing percentages, hot carcass weights, muscle dry matter or muscle weights. The ingestion of high salt diet prior to slaughter, did increase fluid retention in the extracellular spaces prior to slaughter however by 48 h both groups were at a similar physiological and therefore similar hydration status. Therefore similar levels of fluid were present in the muscles and no difference in carcass weight or dressing percentage could be expected. An important observation from the second experiment was that the high salt group drunk more water than the low salt fed sheep but the low salt group consumed fluid in lairage also. The low salt fed sheep may have been encouraged to drink water after observing the frequent drinking patterns of the high salt group.
This thesis has also shown that saltbush contains high levels of vitamin E (alpha-tocopherol) (193 mg/kg dry matter). As a result the concentration of alpha-tocopherol in plasma, liver and muscle of the saltbush fed sheep was elevated compared to those grazing dry pasture. The high muscle concentrations of vitamin E in the saltbush-grazed sheep resulted in improved meat colour stability. The high vitamin E levels did not influence the drip and cooking loss of the meat despite a decrease in the muscle dry matter of the meat. The browning of meat and increased drip loss results in large losses to the meat industry due to value deterioration at the supermarket. There is also great potential for the high vitamin E content in saltbush to be used for the prevention of nutritional myopathy instead of using expensive and labour intensive synthetic supplements.
In conclusion, this thesis has provided an insight into the carcass and eating quality of sheep grazed on saltbush based saline pasture systems. The most significant findings were that ingesting saltbush can reduce the carcass fat content, improve meat colour stability and not result in any detriment to eating quality. A potentially useful way to incorporate these results into an Australian farming system may be to use saltbush on a short term basis, not for the length of period grazed in this thesis. The short term use of saltbush should provide sufficient grazing time for an elevation of vitamin E levels in the muscle to improve meat colour stability, increase the amount of lean and decrease fat levels of a carcass all without changing eating quality and decreasing liveweight. Further work is needed to ensure that these benefits can be achieved without compromising animal production. The opportunity to utilise saltbush to produce leaner carcasses with better colour stability may encourage farmers to consider previously unproductive land planted to saltbush to be a highly useful enterprise
Dietary fibre for the newly weaned pig: Influences on pig performance, intestinal development and expression of experimental post-weaning colibacillosis and intestinal spirochaetosis
No full textThe diet fed in the immediate post-weaning phase influences the development of the intestinal tract and the establishment of microflora within the gut of the piglet. This development may prove beneficial to the long-term health of the pig or it may result in growth checks, diarrhoea and excessive growth of intestinal pathogens, depending on the diet fed and the stresses imposed upon the piglet. Post-weaning colibacillosis (PWC) is associated with excessive proliferation of enterotoxigenic Escherichia coli in the small intestine. These bacteria attach to enterocytes and release toxins that cause hypersecretory diarrhoea. Diarrhoea is accompanied by weight loss, anorexia, dehydration and eventually death if infection is severe. The pathogenesis of PWC is complex and multifactorial, and is heavily influenced by weaning-associated factors such as stress and the change in diet at weaning. The primary aim of this PhD study was to investigate the influence of dietary fibre on the intestinal and whole body development of healthy weaner pigs and pigs with experimental PWC. The latter animals were used to investigate the influence of fibre on the incidence of diarrhoea and the proliferation of pathogenic intestinal E. coli in experimentally infected pigs.
Physiologically, the term dietary fibre includes any plant polysaccharides that are resistant to digestion in the small intestine, instead passing into the large intestine where they are fermented. The negative control diet used in all experiments contained cooked white rice as the main ingredient because it is very low in fibre content and is highly digestible. Sources of fibre were added into this diet to create the desired level and type of dietary fibre. In experiments 2, 3 and 4, a hydrolysed rice diet was also tested as a base rice ingredient. As different facilities were used for healthy and experimental infection experiments, Chapter 3 addressed the issue of food intake with regard to the design of experiments within the project. The remainder of the thesis was divided into sections based on the particular type of dietary fibre that was being targeted. Typically, pigs were killed 1-3 weeks after weaning, and intestinal and whole body measurements made. Dietary sources of primarily insoluble fibre were first examined, followed by sources of soluble fibre, and finally purified viscous soluble sources of fibre. Each of these areas was explored with regard to the intestinal and whole body development of the healthy pig before investigating how the type of fibre affected pigs with experimental PWC. As an extension of this work to other intestinal infections, the influence of dietary soluble viscous fibre on the pathogenesis of porcine intestinal spirochaetosis (PIS), a post-weaning large intestinal infection caused by the spirochaete Brachyspira pilosicoli, was also tested.
In the healthy newly weaned pig there was rapid adaptation to the presence of increasing amounts of dietary fibre. Sources of insoluble fibre, particularly wheat and lupins, had the greatest effect on increasing the size of the large intestine and on increasing microbial fermentation, although the addition of soluble fibre (pearl barley) also was capable of significantly increasing large intestinal size and fermentative capacity compared to the base rice diet. As a result of feeding fibre sources, the carcase growth tended to suffer at the expense of intestinal growth, although all pigs expended energy into intestinal growth in the immediate post-weaning period. The ileal digestibility of nutrients at 10 days post-weaning was depressed by addition of fibre to the diet. The digestibility of crude protein and gross energy at the ileum decreased upon addition of insoluble fibre from lupins, and upon addition of resistant starch, whilst addition of pearl barley (soluble fibre) reduced the starch digestibility.
The interaction of diet with the development and expression of PWC differed according to the diet fed. Inoculation with enterotoxigenic E. coli generally reduced the whole body and intestinal growth and intestinal fermentation of all pigs, although the pigs fed the cooked white rice diet suffered the least depression in growth and consistently had drier faeces throughout all trials.
Raw wheat, as a primary dietary ingredient and source of insoluble fibre and resistant starch, did not significantly alter the proliferation of intestinal enterotoxigenic E. coli. However, extrusion of the wheat resulted in an increase in the proliferation of E. coli, as did hydrolysing the rice. Addition of pearl barley (soluble fibre source) to the cooked rice diet significantly increased the proliferation of enterotoxigenic E. coli as well as increasing the viscosity of the intestinal contents of healthy and experimentally infected pigs. Feeding a diet containing the viscous, purified polysaccharide carboxymethylcellulose (CMC) at 4% of the diet induced a natural infection of PWC without requiring experimental inoculation with enterotoxigenic E. coli. This effect was repeatable in the immediate post-weaning period but did not occur a few weeks after weaning.
This study showed that dietary fibre affects the rate of development of the intestines and the pig’s ability to utilise dietary nutrients immediately after weaning. Although increasing the amount of dietary fibre was not always detrimental to the live weight growth of the pig, the experimentally infected pigs fed the cooked rice diet (low fibre) were the only infected animals to maintain positive growth rates. The expression of PWC was increased by the addition of soluble fibre and by increasing the viscosity of the intestinal contents. This work illustrates the complex interaction of diet with the microflora of the pig’s intestinal tract, and suggests that a highly digestible, low fibre diet may be most suitable for growth and prevention of intestinal disorders in the first one to two weeks following weaning
Fugitive Direction: Reflections on the Troppen Museum
No full textThis text discusses the efficacy of performance as a research tool within the context of museological practice. Situated within Amsterdam’s Troppen Museum, the performance formed part of a moving-image piece, La Javanaise (2012. Dir. Wendelien van Oldenborgh. The Netherlands). The analysis of the performance and its context within the Fugitive Directions text contrasted the use of modalities of visibility within curatorial practice with their deployment in moving-image production. The positioning of museum practice alongside moving-image as contemporary technologies of visibility, particularly as regards racialized objects, becomes a key point. It refuses the positioning of the museum as only occupying an historicizing function, presenting it as subject to analytical devices as applied to other visual media
Evaluation of dietary fibre as contributing factor in the development of swine dysentery
No full textDiets that alter fermentation in the hindgut of pigs have been shown to influence the incidence of swine dysentery (SD), an infectious mucohaemorrhagic colitis in pigs caused by infection with the bacterium Serpulina hyodysenteriae. Reducing fermentation can help protect pigs from developing the disease, whilst the fully protective diet, based on cooked white rice, has been described. The aim of this study was to determine links between the diet fed to pigs, hindgut fermentation, and the incidence of SD, and then to develop a commercially applicable diet that would protect pigs against SD.
In this study, the first procedure was to estimate pig performance and the hindgut fermentation that occurred when pigs were fed different diets. This was followed by infection trials to provide information on the incidence of SD when these diets were fed. These results were brought together to provide the required information. Overall 246 weaner pigs were fed one of 20 diets in six experiments. Diets were formulated either to investigate the role of different types and levels of dietary fibre on susceptibility to SD, or to test some dietary treatments (dietary extrusion, addition of exogenous enzymes, application of a protective diet after experimental infection) designed to help prevent or reduce the expression of SD. All pigs were fed the experimental diets for four to eight weeks, and then half of the pigs on each diet were killed and their large intestines collected to assess hindgut fermentation. The remaining pigs on each diet were infected with a virulent strain of S. hyodysenteriae and monitored for SD.
Hindgut fermentation was suppressed in pigs consuming diets with low levels of fermentable fibre (resistant starch, RS, and soluble non-starch polysaccharides, sNSP), and these pigs did not develop SD. The dietary inclusion of either RS, sNSP, or both to an otherwise protective diet based on cooked rice, resulted in increased hindgut fermentation and a high incidence (80 - 100%) of iv SD. Extrusion of wheat reduced hindgut fermentation and the incidence of disease in experimentally infected pigs in one experiment, but not in the other. Dietary addition of an sNSP-degrading enzyme reduced hindgut fermentation and the incidence of SD only when added to a raw wheat diet, or when combined with an RS-degrading enzyme in an extruded wheat diet. Finely ground sorghum-based diets caused a substantial decrease in fermentation, also achieving a considerable reduction in the disease. Further extrusion and/or addition of RS-degrading enzymes did not improve this effect.
The present study confirmed that diets varying in their RS and sNSP content affect several events in the large intestine, with diets having low levels of these ingredients having a capacity to reduce the incidence of SD. This study however failed to identify a diet which would be fully protective as well as commercially applicable and financially viable in farmed pig production. Although protection against SD in pigs by dietary treatments was imperfect, some of these treatments might still be useful if undertaken in combination with other methods for the prevention and control of SD
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