Role of endothelin receptor activation in secondary pulmonary hypertension in awake swine after myocardial infarction

Posted in: Welfare by admin on January 1, 2006 | No Comments

Influence of rearing conditions on performance, behavioral, and physiological responses of pigs to preslaughter handling, carcass traits, and meat quality

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Societal concerns about conventional pig production have been increasing for a number of years in Europe. The conventional production system is generally thought to be associated with a negative environmental impact (pollution, offensive odors), and poor animal welfare due to high animal densities and bad housing conditions, and is perceived to result in reduced meat quality (Rainelli, 2001; Ngapo et al., 2003). Thus, in the near future, the pork industry has to propose pig production systems that satisfy consumer and citizen demands for lower environmental impact, improved animal welfare, and better meat quality. In this study a total of 120 crossbred [synthetic line × (Large White × Landrace)] pigs (castrated males and females) were used to evaluate the influence of rearing conditions for growing-finishing pigs on growth performance, carcass, stress reactions at slaughter, and meat eating quality. At approximately 35 kg of live weight (LW), littermates were allocated to either a conventional (fully slatted floor, 0.65 m²/pig, considered as control, CON) or an alternative (sawdust bedding with free access to an outdoor area, 2.4m²/pig, OUT) system, until slaughter at approximately 110 kg of LW. Pigs had free access to standard growing and finishing diets. The trials were conducted in spring, summer, and winter, with each season involving 2 pens of 10 pigs in each system. Compared with the CON, the OUT pigs exhibited a greater growth rate due to their greater feed intake, resulting in a greater body weight at slaughter. The OUT pigs had thicker backfat and lower lean meat content than the CON pigs. The OUT system did not influence the behavioral activities of pigs during lairage at the slaughterhouse, or the urinary levels of catecholamines and cortisol, and plasma levels of ACTH, cortisol, lactate, creatine kinase, and FFA immediately after slaughter. The OUT pigs had similar pH values 30 min postmortem in the lean meat, biceps femoris and semimembranosus muscles, but lower ultimate pH in semimembranosus muscles and in the backfat. Despite nonsignificant effects of production system on stress reactions at slaughter, assessed by urine and plasma indicators and muscle metabolism at 30 min postmortem, meat from OUT pigs had more lean meat drip loss after 2 and 4 days than did meat from the CON pigs. The OUT system slightly increased meat yellowness in the lean meat back fat, and semimembranosus muscles, whereas redness and lightness of the 3 muscles were unaffected. Also, intramuscular fat content was greater in the lean meat, backfat and semimembranosus muscles of the OUT pigs. It was also concluded that outdoor rearing during summer and winter improved meat juiciness, whereas odor, flavor, and tenderness were unaffected. Influence of rearing conditions on all the other traits studied did not depend on the season.

Phenotypic, Genetic and Epigenetic Variation of Immune Response and Disease Resistance Traits of Pigs

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The immune system is composed of integrated, genetically and environmentally regulated sets of cells and molecules that control the response to external and internal stimuli, including pathogenic microorganisms. In terms of infectious organisms, the response of the host largely reflects the relationship or adaptation between the host and agent. The variation in host response is influenced through genotype by environment interactions. Epigenetic effects are also highly sensitive to environmental influence and thus can rapidly alter individual phenotype. These are non-sequence alterations to DNA that cause changes in DNA structure that affect its availability for transcription. Consequently, disease is largely the product of incompatible gene by environmental interactions that include both genetic and epigenetic effects. These interactions vary at both the individual and population level. It is therefore particularly relevant to understand host-pathogen relationships and adaptations under various stress and management conditions. Improved understanding of the biology and genetic relationships between the host and pathogen, particularly those that affect the immune system during periods of production stress, should facilitate implementation of non-traditional approaches to improve the health of intensively reared livestock. This paper will briefly describe some of the genetic and environmental variation documented in immune response and performance traits of pigs, mainly using examples from experiments performed by the authors over the last two decades of research. Integrating quantitative and molecular genetic strategies to enhance the immune performance and improve inherent disease resistance of pigs, as well as other livestock species, has been the focus of much research. The data collected demonstrates that considerable phenotypic variation exists in immune response traits of pigs and that a substantial portion of that variation is due to additive genetic variance allowing for selective breeding of pigs with higher immune responsiveness. The underlying principle being that optimal disease resistance should be a function of optimal resistance-mediating defense mechanisms. Genes that underlie high or low immune responses and disease resistance are beginning to be understood, such as those within the MHC; however, selective breeding for complex disease traits should still be based on estimated breeding values of superior heritable phenotypes. The next step will be to evaluate high and low immune responsiveness and it’s influence on health and production traits in several commercial breeding nucleus herds.

Assessment of a group-housing system for gestating sows: Effects of space allowance and pen size on the incidence of superficial skin lesions, changes in body condition, and farrowing performance

Posted in: Pork Insight Articles, Welfare by admin on May 25, 2005 | No Comments

This study looks at the short term effects of converting a gestation style barn into a group housing barn and how the change in pen size and sow mixing causes or impacts skin lesions, body condition and reproductive performance. 285 sows were put into groups of 11 to 31 sows and held in either large or small pens. Also 98 sows were held in gestation crates. The bodies of the pigs were assessed before  they entered the specific housing unit and after they left. Also recorded was piglet birth weights, liveborn piglets and stillborn piglets. Body condition was not effected by group housing in any pen size or space allowance. Group housed sows initially had more skin lesions but it did not depend of size of the pen or space allowance, and the occurrence of lesions decreased over time. Group housed sows had slightly heavier piglets and larger litter sizes. Switching to sow housing did not effect body condition or effect reproductive performance, skin lesions were a temporary side effect of mixing.

Duration of restraint and isolation stress as a model to study the dark-cutting condition in cattle.

Posted in: Welfare by admin on January 1, 2005 | No Comments

The duration of restraint and isolation stress (RIS) on endocrine and blood metabolite status and the incidence of dark-cutting LM were assessed using Holstein steer calves. Treatments included unstressed controls (NS), or a single bout of RIS for 2, 4, or 6 hours. Serum cortisol and plasma lactate increased during the first 20 minutes after the RIS application and remained high throughout the 6 hours of RIS. Plasma glucose and insulin concentrations were greater for RIS calves than NS calves after 80 and 100 minutes of stressor application respectively. RIS did not affect plasma NEFA concentrations. Slaughter occurred within 20 minutes of completion of RIS. The pH of the LM from calves subjected to 6 hours of RIS was greater than 6.0 and was higher than that of NS calves and 2 and 4 hour RIS calves 24 and 48 hours post mortem. Concentrations of muscle glycogen did not differ between the treatments and the LM lactate concentrations tended to be lower in calves subjected to 6 hours of RIS. The LM of calves subjected to 6 hours of RIS had more bound and less free moisture than the LM from NS calves and calves subjected to 2 or 4 hours of RIS at 48 hours after exsanguination. Furthermore, the LM from RIS calves was darker than the LM of NS calves. Calves subjected to 6 hours of RIS had the greatest visual color scores for the LM and NS calves had the lowest. Cases of dark-cutting resulted from calves in all treatments except the NS treatment. Therefore, RIS may have been proven to be a reliable animal model with which to study the formation of the dark-cutting condition.

Preferences of sheep for different types of pen flooring

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Sheep preference for different types of pen flooring were tested using two lying areas with one of the following flooring materials: 1) solid wood versus rubber mats, 2) expanded metal versus solid wood, 3) solid wood versus straw, or 4) expanded metal versus straw. In experiment one, 16 ewes were divided into four groups to test their preferences. In experiment two, eight ewes were individually tested, first fully coated, then once shorn. In experiment one, the first animal that lay down after feeding preferred to lie on straw over wood or metal, and preferred to lie on wood over metal. Unshorn ewes did not show a flooring preference. In experiment two, individually housed, unshorn ewes preferred wooden flooring to rubber mats, and tended to choose expanded metal flooring to straw. The other treatments did not show any preferences. Once shorn, the ewes preferred wooden flooring to expanded metal, straw to wooden flooring, and straw to expanded metal flooring. A preference between rubber mats and wooden flooring did not exist. For unshorn ewes, the mean lying time (% of observations) for all treatments was 64.7 %. There were no significant differences between treatments. In the first 2-3 days post-shearing, mean lying time (% of observations) was 43 %. The lying times for pre-shearing and post-shearing differed when the ewes were housed in pens with no straw, but not when ewes had access to straw. There was indication that shorn ewes preferred softer floors with low thermal conductivity (straw and wood), but this was not noted for unshorn ewes. Access to straw in the first week after shearing may improve animal welfare, which is concluded from the less dramatic reduction in lying time after shearing when ewes have access to straw.

Cross-sucking and other oral behaviours in calves, and their relation to cow suckling and food provision.

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When calves are unable to suckle, it is thought that they begin to develop abnormal oral behaviour, although it is not known whether this behaviour occurs because the calf needs access to its dam or whether a multiple suckling system would suffice to prevent the behaviour from developing. An initial experiment examined the behaviour of calves that suckled their own dam or another cow for 15 minutes each day and compared that to the behaviour of artificially-reared calves that had no opportunity to suckle. Calves that were allowed to suckle consumed more milk than calves that were reared artificially. Cross-sucking behaviour was greater in non-suckled (artificially reared) calves than in suckled calves. Cross-sucking was at its highest frequency 1 minute after the end of milk feeding in the non-suckled calves, and declined linearly to negligible levels at 13 minutes after milk feeding had occurred. Most of the cross-sucking behaviour (78 %) was directed at the inguinal (udder/scrotal) region of other calves. For suckled calves, however, more of the cross-sucking behaviour (81 %) was directed at the mouths of other calves. Calves that had been artificially reared spent more time consuming concentrate feed and consumed more feed than suckled calves, suggesting that food ingestion could provide a replacement stimulus. A second experiment found that before weaning, the time calves spent licking their pen or bucket increased until feed intake was sufficient to stimulate significant amounts of rumination. After weaning, the behaviours decreased. Conclusions stated that cross-sucking of artificially-reared calves could be prevented by providing short access to either the calf’s dam or another cow for two short periods each day. When a cow was absent and no suckling could occur, the calves licked inanimate objects repeatedly until the consumption of solid feed was sufficient to stimulate rumination.

Repeated transport and isolation during pregnancy in ewes: Effect on the reactivity to humans and to their offspring after lambing

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The reactivity of ewes to their lambs and to humans after lambing was examined. Six weeks prior to lambing, the ewes were repeated exposed to several stressors that varied in intensity. The ewes were stressed by transporting them alone, isolating them or isolating them with a dog. The ewes were underwent a stressful session twice a week. Each session last one hour, and in total, each ewe underwent 10 sessions. The control ewes were not disturbed. Blood samples were collected during the first, fifth and ninth stress sessions, in order to measure their cortisol response. The ewe’s maternal reactivity and fear of humans was measured in seven scenarios. One hour after birth, a human approached the lambing site and the lamb. Five minutes after tagging someone held the lamb. Six hours after birth the ewe was forced across a hallway to reach her lambs. Six hours after birth, in order for the ewe to remain close to her lamb, she was forced to tolerate the presence of a human. The ewe was also separated from the lamb and forced to enter the lamb box. One month following birth, a human approached the ewe, and then measured the flight distance of the ewe. The highest cortisol response was measured in ewes that were transported, during the first and ninth sessions. The ewes did demonstrate habituation to every treatment over time. During the tests conducted one and six hours after birth, ewes that were isolated attempted to maintain contact with their lambs, while the ewes that were transported did not. The control ewes response was moderate compared to the transport and isolation treatment ewes. One month after birth, the isolated ewes continued to show less avoidance of humans than transported ewes, while the control ewes remaining intermediate between the responses of the other two treatments. There were also correlation found between the cortisol response during the stress and the responses made 1 hour, 6 hours and 1 month after birth. The variation in the ewes’ behaviour after lambing was likely due to the different stressors causing varying degrees of fear towards humans. The behaviour is not related to the ewe developing a weaker mother-young bond. Hence, repeated isolation reduced the ewe’s fear of humans, while repeated isolated transportation increases a ewe’s fear of humans.

Nitric oxide blunts the endothelin-mediated pulmonary vasoconstriction in exercising swine

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Nutritional and physiological responses of growing pigs exposed to a diurnal pattern of heat stress

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Understanding the impact of changes in the environment on the nutritional and physiological status of the pig will facilitate development of appropriate environmental management and feeding strategies (DeShazer, 1982). The objective of this study was to characterise the nutritional and physiological responses of growing pigs, with particular emphasis on effects on acid–base and thermal homeostasis, when exposed to a diurnal pattern of heat stress. It was found that a diurnal pattern of heat stress fluctuating between 20°C and 38°C within 24 h did not affect mineral
metabolism in growing pigs and had limited effect on acid–base balance. Therefore, pigs have the ability to recover from the effects of heat stress if periods of heat stress are followed by periods of thermal comfort. The diurnal pattern of heat stress had an effect on the physiological status of pigs resulting from the mechanisms (e.g., increased respiration rates) used to maintain thermal homeostasis and associated renal compensation. Therefore, strategies for managing pigs exposed to heat stress should focus on ways (e.g., provision of cool drinking water) of enhancing the pig’s ability to dissipate excess body heat, and should recognise the impact of thermal stress on acid–base parameters.