A meta-analysis of the effects of high ambient temperature on growth performance of growing-finishing pigs

High ambient temperature (T) is one of the most important climatic factors influencing pig performance. Increased T occurs sporadically during summer heat waves in temperate climates and year round in tropical climates. Results of published experiments assessing the effects of high T on pig performance are surprisingly variable. Thus, a meta-analysis was performed to aggregate our knowledge and attempt to explain differences in the results across studies on the effect of increased T on ADFI and ADG in growing-finishing pigs. Data for ADFI and ADG were extracted from 86 and 80 trials, respectively, from articles published in scientific journals indexed in PubMed, Science Direct, and from proceedings of scientific meetings through November 2009. Data on ADFI and ADG were analyzed using a linear mixed model that included the linear and the quadratic effects of T and BW, and their interactions as continuous, fixed effects variables, and the trial as a random effect factor (i.e., block). In addition, the effects of housing type (2 levels: individual and group housing) and the year of publication (3 levels: 1970 to 1989, 1990 to 1999, and 2000 to 2009) on the intercept and the linear regression term for T (i.e., the slope) were also tested. Results showed that high T had a curvilinear effect on ADFI and ADG and that this effect was more pronounced in heavier pigs. Across T, ADFI was less when pigs were group-housed. The intercept and the regression coefficient (slope) for T were significantly affected by the year of publication. The effect of increased T was greater in more contemporary works, suggesting that modern genotypes could be more sensitive to heat stress than older genotypes of lesser growth potential. In conclusion, pig performance decreases at an accelerating rate as T is increased. The large between-study variability on the effects of high T on pig performance is partially explained by differences in pig BW and to a lesser extent by the year the study was published.     

Chronic pleuritis in Danish slaughter pig herds

Respiratory disease is considered the most serious disease problem in modern pig production and the risk has increased with intensification of pig production. We quantified risk factors for chronic pleuritis (CP) in Danish pig herds in terms of herd and herd-owner characteristics, management and neighbourhood factors. The occurrence of CP was investigated in 540,104 slaughter pigs from 259 farrow-to-finish or finishing herds during the mandatory post-mortem meat inspection at 18 Danish abattoirs. The monthly herd- and abattoir-specific prevalences of CP were estimated for the months January through August 2000. Meat-inspection data, herd characteristics and neighbourhood factors were obtained from databases at the Danish Bacon and Meat Council. Data on herd-owner characteristics and management factors were obtained by telephone interviews. Data were analysed using a mixed model accounting for repeated measurements. Four factors were associated with increased herd prevalence of CP: low health status of the herd, pig density within a 5 km radius, mingling of pigs during the production period and the month of slaughter. Two factors protected against CP: feeding with only dry feed and practising all-in-all-out production.     

Within-farm spread of classical swine fever virus--a blueprint for a stochastic simulation model

A stochastic simulation model to investigate the transmission of classical swine fever (CSF) virus within an infected farm is described. The model is structured according to the processes that occur within and between management groups (pig units or houses). It uses the individual pig as the unit of interest and estimates the number of animals in the states 'susceptible', 'infected', 'infectious', and 'removed' for each day of the disease incident. Probabilities are assigned to the transitions between states. The probability of a pig becoming infected is made dependent on the probability of contact between a susceptible and an infectious pig as well as the probability of transmission. The more pigs become infected in one unit, the more likely is subsequent spread to another management group on the farm. Ultimately, the probability that a shipment of pigs from the farm will include at least one infected pig can be estimated in order to identify high-risk movements during a CSF epidemic. The model results were compared with experimental data on CSF transmission within one pig unit (management group). It could be shown that the model was capable of reproducing the experimentally observed infection and mortality rates. To improve the input parameters and for further model validation, more experimental data and field data from CSF outbreaks are needed.     

Risk factors for porcine reproductive and respiratory syndrome outbreaks in Vietnamese small stock farms

AIM: To examine risk factors that could have played a role in the 2010 porcine reproductive and respiratory syndrome (PRRS) outbreak in Yenhung district, Quangninh province, North-Vietnam, with the purpose of establishing why existing control measures implemented after previous outbreaks had failed to prevent further outbreaks.

METHODS: A case-control study was carried out in Yenhung district. Data were obtained by an interview-based questionnaire survey. The sampling unit was households, which equated to small-scale pig farms. A total of 150 case and 150 control households were selected at communes affected by the 2010 PRRS epidemic during April to June. Risk factors were analysed using binary logistic regression and unconditional multiple logistic regression.

RESULTS: Households infected with PRRS were significantly associated with multiple variables belonging to three main groups: (1) location of the farms: i.e. farms positioned <1,000?m from a pig abattoir or within 500?m of local markets or 100?m of main roads; (2) farm management: i.e. where there was non-application of weekly farm disinfection, feeding uncooked swill, new introduction of purchased pigs without isolation, or usage of water from irrigation systems for raising pigs; (3) people and animal contact: i.e. where households kept animals with either no confinement or partial confinement, had visits by family members to other affected farms or had frequent visits by neighbours. The use of water from irrigation systems was found to be the risk factor most strongly associated with infected households in the 2010 outbreak (OR=22; 95% CI=12–42).

CONCLUSIONS: The results show that the epidemiology of PRRS in Quangninh province was linked to sociological and cultural practices, and that effective PRRS control needs an integrated approach coupled with behavioural changes in the pig raising practices of the general public. Failure to recognise this could explain why further outbreaks have occurred.     

Genetic determination of mothering ability and piglet growth in indigenous Mukota sows of Zimbabwe

The objective of this study was to determine genetic parameters of individual and sow records on litter size and weights at 21 and 35 days in Mukota pigs. Data gathered from 1961 pigs at the University of Zimbabwe between January 1998 and August 2003, were analysed. Individual pig traits analysed were the weight at 21 days of age (THRWT), weight at weaning (WWT) and average daily gain from birth to weaning (ADGWW). Sow performance traits considered were the litter weight after 21 days (LTHRWT), litter weight at weaning (LWWT), number of pigs weaned (NW) and mothering ability (MA). An animal model was used to estimate genetic parameters using the average information restricted maximum likelihood procedure. Individual pig records were analysed using models with or without litter effects and maternal genetic effects. Incorporating the maternal genetic variance component drastically reduced the standard errors of the heritability estimates. The heritabilities for LTHRWT, LWWT and MA were 0.18, 0.15 and 0.05, respectively. The LWWT and NW were positively correlated. There were no genetic relationships between MA and LTHRWT and LWWT. No antagonisms should be expected when selecting for MA and increasing litter weights in Mukota pigs.     

Intra-unit correlations in seroconversion to Actinobacillus pleuropneumoniae and Mycoplasma hyopneumoniae at different levels in Danish multi-site pig production facilities

In this paper, multilevel logistic models which take into account the multilevel structure of multi-site pig production were used to estimate the variances between pigs produced in Danish multi-site pig production facilities regarding seroconversion to Actinobacillus pleuropneumoniae serotype 2 (Ap2) and Mycoplasma hyopneumoniae (Mh). Based on the estimated variances, three newly described computational methods (model linearisation, simulation and linear modelling) and the standard method (latent-variable approach) were used to estimate the correlations (intra-class correlation components, ICCs) between pigs in the same production unit regarding seroconversion. Substantially different values of ICCs were obtained from the four methods. However, ICCs obtained by the simulation and the model linearisation were quite consistent. Data used for estimation were collected from 1161 pigs from 429 litters reared in 36 batches at six Danish multi-site farms chronically infected with the agents. At the farms, weaning age was 3-4.5 weeks, after which batches of pigs were reared using all-in/all-out management by room. Blood samples were collected shortly before: weaning, transfer from weaning-site to finishing-site, and sending the first pigs in the batch for slaughter (third sampling). Few pigs seroconverted at the weaning-sites, whereas considerable variation in seroconversion was observed at the finishing-sites. Multilevel logistic models (initially including four levels: farm, batch, litter, pig) were used to decompose the variation in seroconversion at the finishing-site. However, there was essentially no clustering at the litter level-leading to the use of three-level models. In the case of Ap2, clustering within batch was so high that the data eventually were reduced to two levels (farm, batch). For seroconversion to Ap2, ICC between pigs within batches was approximately 90%, whereas the ICC between pigs within batches for Mh was approximately 40%. This indicates that the possibility for Mh to spread between pigs within batches is lower than for Ap2. The diversity in seroconversion between batches within the same farm was large for Ap2 (ICC approximately 10%), whereas there was a relative strongly ICC (approximately 50%) between batches for Mh. This indicates that the transmission of Mh is more consistent within a farm, whereas the presence of Ap2 varies between batches within a farm.     

Effect of recombinant DNA-derived bovine alpha-1 interferon on transmissible gastroenteritis virus infection in swine

Recombinant DNA-derived bovine interferon alpha 1-1 (BoIFN) inhibited replication of both vesicular stomatitis virus and transmissible gastroenteritis virus in cultures of swine testicular cells. Newborn pigs were orally inoculated with BoIFN and subsequently had interferon in their gastric contents and serum; however, interferon was found only occasionally in intestinal washings. Incubation of BoIFN with gastric contents from a newborn suckling pig did not affect antiviral activity, whereas intestinal (small intestine) contents from the same animal inactivated BoIFN within 1 minute. Beginning at 6 hours of age, newborn, colostrum-deprived pigs were given 1 mg of BoIFN orally every 12 hours. These pigs were not protected against challenge exposure to virulent transmissible gastroenteritis virus at 48 hours of age; disease and mortality were similar for these pigs and for control pigs not given BoIFN prior to challenge exposure. The BoIFN did not impair growth rate of pigs and did not cause obvious disease or lesions.     

Alternative prediction methods of protein and energy evaluation of pig feeds

Precise knowledge of the actual nutritional value of individual feedstuffs and complete diets for pigs is important for efficient livestock production. Methods of assessment of protein and energy values in pig feeds have been briefly described. In vivo determination of protein and energy values of feeds in pigs are time-consuming,expensive and very often require the use of surgically-modified animals. There is a need for more simple, rapid,inexpensive and reproducible methods for routine feed evaluation. Protein and energy values of pig feeds can be estimated using the following alternative methods: 1) prediction equations based on chemical composition; 2)animal models as rats, cockerels and growing pigs for adult animals; 3) rapid methods, such as the mobile nylon bag technique and in vitro methods. Alternative methods developed for predicting the total tract and ileal digestibility of nutrients including amino acids in feedstuffs and diets for pigs have been reviewed. This article focuses on two in vitro methods that can be used for the routine evaluation of amino acid ileal digestibility and energy value of pig feeds and on factors affecting digestibility determined in vivo in pigs and by alternative methods. Validation of alternative methods has been carried out by comparing the results obtained using these methods with those acquired in vivo in pigs. In conclusion, energy and protein values of pig feeds may be estimated with satisfactory precision in rats and by the two-or three-step in vitro methods providing equations for the calculation of standardized ileal digestibility of amino acids and metabolizable energy content. The use of alternative methods of feed evaluation is an important way for reduction of stressful animal experiments.     

Spatial and temporal investigations of reported movements,births and deaths of cattle and pigs in Sweden

Background

Livestock movements can affect the spread and control of contagious diseases and new data recording systems enable analysis of these movements. The results can be used for contingency planning, modelling of disease spread and design of disease control programs.

Methods

Data on the Swedish cattle and pig populations during the period July 2005 until June 2006 were obtained from databases held by the Swedish Board of Agriculture. Movements of cattle and pigs were investigated from geographical and temporal perspectives, births and deaths of cattle were investigated from a temporal perspective and the geographical distribution of holdings was also investigated.

Results

Most movements of cattle and pigs were to holdings within 100 km, but movements up to 1200 km occurred. Consequently, the majority of movements occurred within the same county or to adjacent counties. Approximately 54% of the cattle holdings and 45% of the pig holdings did not purchase any live animals. Seasonal variations in births and deaths of cattle were identified, with peaks in spring. Cattle movements peaked in spring and autumn. The maximum number of holdings within a 3 km radius of one holding was 45 for cattle and 23 for pigs, with large variations among counties. Missing data and reporting bias (digit preference) were detected in the data.

Conclusion

The databases are valuable tools in contact tracing. However since movements can be reported up to a week after the event and some data are missing they cannot replace other methods in the acute phase of an outbreak. We identified long distance transports of cattle and pigs, and these findings support an implementation of a total standstill in the country in the case of an outbreak of foot-and-mouth disease. The databases contain valuable information and improvements in data quality would make them even more useful.     

Welfare assessment in porcine biomedical research – Suggestion for an operational tool

In recent years, increasing interest in using the pig (Sus scrofa) for biomedical research has become evident. Today, the pig is considered an advantageous alternative animal model for various human diseases and conditions. However, even though a considerable amount of biomedical research has been done on pigs, hardly any studies include systematic welfare assessment. Still, it is essential to assess welfare of laboratory pigs, both domestic pig breeds and smaller purpose-bred breeds, as (1) scientific obligations entail responsibility to ensure and document a fair welfare standard for animals used for experimental purposes; and (2) the scientific outcome can be dependent upon the welfare state of the animals. In order to be able to quantify and control laboratory pig welfare, a practical tool is needed. The purpose of the present paper is to provide an overview of the current status of the extent of welfare assessment in pigs used in biomedical research and to suggest a welfare assessment standard for research facilities based on an exposition of ethological considerations relevant for the welfare of pigs in biomedical research. The tools for porcine welfare assessment presented suggest a method for monitoring the welfare status of individual laboratory pigs, intended to relieve the practical scoring of the welfare of individual pigs as well as the interpretation of the findings.     

Welfare assessment in porcine biomedical research - suggestion for an operational tool

In recent years, increasing interest in using the pig (Sus scrofa) for biomedical research has become evident. Today, the pig is considered an advantageous alternative animal model for various human diseases and conditions. However, even though a considerable amount of biomedical research has been done on pigs, hardly any studies include systematic welfare assessment. Still, it is essential to assess welfare of laboratory pigs, both domestic pig breeds and smaller purpose-bred breeds, as (1) scientific obligations entail responsibility to ensure and document a fair welfare standard for animals used for experimental purposes; and (2) the scientific outcome can be dependent upon the welfare state of the animals. In order to be able to quantify and control laboratory pig welfare, a practical tool is needed. The purpose of the present paper is to provide an overview of the current status of the extent of welfare assessment in pigs used in biomedical research and to suggest a welfare assessment standard for research facilities based on an exposition of ethological considerations relevant for the welfare of pigs in biomedical research. The tools for porcine welfare assessment presented suggest a method for monitoring the welfare status of individual laboratory pigs, intended to relieve the practical scoring of the welfare of individual pigs as well as the interpretation of the findings.     

Relations between body weight, feed intake, daily weight gain, and exocrine pancreatic secretion in chronically catheterized growing pigs

The aim of this investigation was to develop models that would make it possible to correct exocrine pancreatic secretion data for the effect of BW and feed intake in growing pigs. In addition, the significance of exocrine pancreatic secretion for daily weight gain (DWG) was studied. Data were used from 10 pigs (16 to 32 kg BW) surgically fitted with chronic pancreatic catheters. The samples were collected under controlled conditions for two to five experimental days per animal (a total of 39 observations), during 2 h preprandially and during 2 h when feeding (postprandially). The exocrine pancreatic secretion traits included the hourly output of volume, the amount of protein, and trypsin and amylase activities. Multiple linear regressions were used to develop models to describe exocrine pancreatic secretion. The individual pig was the most important source of variation in the model. With increasing BW, 7 out of 10 pigs showed an increase in exocrine pancreatic secretion. However, the slopes of the regression lines differed between animals, which made it impossible to develop general models for the correction of secretion data for the effect of BW. Postprandial exocrine pancreatic secretion was always higher than preprandial secretion, but the amount of feed intake per se did not seem to affect secretion. Exocrine pancreatic secretion and DWG were positively correlated. We concluded that, under the present circumstances, expressing secretion per kilogram BW or kilogram feed intake was not feasible. Expressing secretion per hour was the best way to present the data.     

Effect of the Stellamune Mycoplasma vaccine on growth, energy conversion, death, and medication use in fattening pigs on a pig farm chronically infected with Mycoplasma hyopneumoniae

The effect of Stellamune Mycoplasma vaccine, administered to piglets aged 2-15 days and then 13-15 days later, on daily weight gain, energy conversion, and use of medication was examined in fattening pigs on a chronically Mycoplasma hyopneumoniae infected pig farm. Half of the piglets were vaccinated and the other half acted as controls. In the study design, half of the pens in the fattening unit were allocated to vaccinated pigs; the other half to non-vaccinated pigs, pen was the experimental unit. In the fattening pens sows and castrated boars were separated. The study consisted of a total of 37 pens with vaccinated, and 37 pens with non-vaccinated pigs in 12 different compartments within the pig herd. In the finishing period, mean growth performance and mean energy conversion (EV/kg) of vaccinated animals was 65 grams/day higher and 0.07 EV/kg lower than in control pigs. Furthermore, the incidence of individual curative medication against respiratory problems was more than 4 times higher in control pigs than in vaccinated pigs. There was a tendency for a higher number of group medications against respiratory problems in control pigs than in vaccinated pigs. It is concluded that, in this herd, vaccination against M. hyopneumoniae was successful from an economic point of view.     

Guinea pig protection test as indicator of potency of oil emulsion foot-and-mouth disease vaccines

A vaccine potency test is described involving virus challenge to six groups of 10 guinea pigs at five weeks after vaccination. Sixteen oil emulsion foot-and-mouth disease vaccines were so tested and nine retested after storage at 4 degrees C for up to 28.3 months. The results were compared with those of the routinely used oil emulsion vaccine potency test (protection afforded to eight pigs challenged 21 days after vaccination). When guinea pig estimates of 3 log2 PD50 or more were obtained, then, with one exception, the batches protected all or almost all pigs from challenge, but when the guinea pig estimates were less than 1 log2 PD50, the vaccines failed to protect five out of eight pigs. The sensitivity and reproducibility of the guinea pig method, established by repeated tests on two vaccine batches, seemed acceptable. The results suggested that guinea pig estimates might provide a suitable substitute for pig challenge potency tests because they reflected the potency of the vaccines, were likely to involve smaller standard errors and caused less discomfort to animals.     

Interleukin-6 dynamics as a basis for an early-warning monitor for sepsis and inflammation in individual pigs

Static interleukin-6 (IL-6) levels of pigs contain considerable individual differences, which obstruct the practical use of IL-6 for disease monitoring purposes. It was hypothesised that interleukin-6 (IL-6) dynamics could be used to quantify these individual differences and carries critical information of the individual pig infection status. Time series of IL-6 responses in 25 pigs were analysed before and after infection by Actinobacillus pleuropneumoniae. The results indicated that amplitude increases of IL-6 fluctuations of individual pigs rather than static IL-6 values should be used as indicator of the infection state. This study shows the added value for IL-6 time series analyses of individual pigs. These results are a first step towards the development of objective individualised methods for monitoring and early detection of sepsis and inflammation processes in pigs by integrating animal response dynamics.     

Trichinellosis in Papua New Guinea

OBJECTIVES: To describe the discovery in a domestic pig of the first case of trichinellosis in Papua New Guinea, caused by a new taxon within the genus Trichinella (T papuae). Also, to establish if the disease occurred in the local wild pig population and in domestic pigs elsewhere in the country, and to test if the worm was infective to some other animals. PROCEDURE: Fresh and fixed tissue samples were examined by the digestion method and histologically, respectively, for the non-encapsulated larvae of T papuae. Feeding trials were conducted, using infected tissues and infective larvae, on animals under laboratory conditions. RESULTS: About 8.8% of a wild pig population in Western Province, adjacent to Irian Jaya, Indonesia, was found to be infected. Infection was not found in other local and feral animals or in domestic pigs from other parts of the country. Infection was experimentally established in cats, pigs and laboratory bred mice and rats. CONCLUSION: Trichinellosis is confined to one remote locality in PNG. Domestic pigs in the initial case became infected, probably, by eating infected wild pig meat.     

Trace mineral status and toxic metal accumulation in extensive and intensive pigs in NW Spain

The aim of the present study was to determine trace element status and toxic metal accumulation in extensive and intensive pigs in NW Spain. Soil, feed and animal tissues (liver, kidney and muscle from 112 pigs) were collected from extensive and intensive pig farms across NW Spain and analysed for metals by ICP-MS and ICP-OES. Our results indicate that animals from both extensive and intensive systems showed an adequate mineral status and that toxic metal residues were generally low, no sample exceeding the maximum admissible levels in meat and meat products established by the EU. Trace element concentrations were generally higher in the intensive pigs possibly reflecting mineral supplementation in the concentrate feed. The statistically significantly higher As, Hg and Pb residues as well as the better Fe and Ni status in extensive pigs could be related at least in part with soil ingestion when rooting. On the contrary, the higher Cd accumulation in the intensive pigs can be explained considering Cu and Zn supplementation in the concentrate feed. Our results also seem to indicate that toxic metal accumulation as well as trace element status in different tissues could be related to metabolic aspects (i.e. related to breed and growth rate) as well as certain management practices (i.e. physical exercise when grazing).     

Longitudinal investigation of the age-related bacterial diversity in the feces of commercial pigs

The importance of bacteria in the gastrointestinal tracts of animals is widely acknowledged as important. However, very little is known about composition and distribution of the microbial population in lower intestinal tracts of animals. Because most bacterial species in pig intestines have not been cultured, it has been difficult to analyze bacterial diversity by conventional culture methods. Even with the development of culture independent 16S rRNA gene sequencing, the previous methods were slow and labor intensive. Therefore, high throughput pyrosequencing of 16S rDNA libraries was used in this study in order to explore the bacterial diversity of the pig feces. In our two trials, fecal samples from individual pigs were collected five times at 3-week intervals, and the 16S rRNA genes in the community DNAs from fecal samples were sequenced and analyzed. This longitudinal study design identified that microbial populations in the feces of the each pig continued to change as pigs aged. The variations of bacterial diversity of the animals were affected by less abundant bacterial components of the feces. These results help us to understand the age-related bacterial diversity in the commercial pig feces.