Experimental infection of slaughter pigs with classical swine fever virus: transmission of the virus, course of the disease and antibody response.

The spread of classical swine fever virus was investigated in an isolation unit containing four pens, each containing six slaughter pigs. One pig in the middle pen of three adjacent pens was inoculated intramuscularly and intranasally with the virus. The fourth pen was located in a separate compartment. The pens were visited in a strict order to study, first, the effect of indirect contact via contaminated clothing and footwear on the spread of the virus to adjacent pens and, secondly, the airborne transmission of the virus between compartments. The pigs were examined and blood samples were taken every other day for 62 days for virological and serological analyses. The virus was highly contagious for the five pigs that were in direct contact with the inoculated pig, but spread to the other pens only after all the pigs in the originally infected pen had become viraemic. The spread of the virus was promoted by contaminated clothing and footwear, but airborne transmission contributed considerably to the spread of the virus within the pighouse. The first clinical signs observed after the virus was introduced into a pen were decreased feed intake, increased mean rectal temperature and apathy. Neither the clinical course of the infection, nor the pattern of seroconversion observed over time, was affected by the differences in the intensity of contact with the virus between the pigs in the different pens.     

Transmission of encephalomyocarditis virus in pigs estimated from field data in Belgium by means of R0

Transmission of encephalomyocarditis-virus (EMCV) has been estimated in experiments, but never using field data. In this field study, a farm in Belgium was selected where the presence of EMCV was confirmed by necropsy and virus isolation. Serology was used to estimate the transmission parameter R0. In one compartment with 630 pigs, 6 pens were fully sampled, in the remaining 38 pens, 2 randomly selected pigs were bled. The 151 pigs were bled twice and their serum was tested in a virus neutralisation test. Seroprevalence at the first and second sampling was 41 and 43% respectively, with a cut off value of 1:40. R0 was estimated for 2 scenarios, in- and excluding mortality based on the final sizes from the serological results of the second sampling. The R0 for the fully sampled pens was estimated between 0.6 and 1.7, the combined estimated R0 of these 6 pens was 1.36 (95%-CI 0.93-2.23). The median of the estimated R0 of the partially sampled pens was 1.3 and 1.4. Sampling two pigs per pen provided insight into the spread of the virus in the compartment, while the fully sampled pens provided an accurate estimation of R0. The low R0 strongly suggests that EMCV is not very effectively transmitted between pigs. The number of seropositive pigs in a pen and the spread in the compartment suggests that other routes of infection are more important, in this case most likely rodents. Preventing viral spread should therefore be focussed on rodent control instead of reduction of contact between pigs.     

An experimental infection (II) to investigate the importance of indirect classical swine fever virus transmission by excretions and secretions of infected weaner pigs

An experiment was set up to investigate the role of excretions and secretions in the indirect transmission of classical swine fever virus (CSFV). In five small pens, 10 weaner pigs (two pigs per pen) were housed and inoculated with CSFV. Experimental infection was successful in all pigs. The infected pigs were kept in the pens for a period of 15 days after which the pens were depopulated and pigs were killed. At the moment of depopulation, all inoculated pigs were visibly clinically diseased and had high fever. Ten hours later the same pens were repopulated with five pairs of susceptible pigs. From inoculation onwards and especially between depopulation and restocking, the pens were neither cleaned nor disinfected. Four days post-repopulation, three of the susceptible pigs were detected positive on virus isolation. A fourth pig was detected positive 2 days later. Later on, the remaining pigs also became infected, most probably due to contact and between pen infections. It can be concluded that transmission of the virus via excretions and secretions succeeded in four of 10 pigs. This result indicates that transmission of CSFV via excretions and secretions can be of importance in a late, clinical stage of disease.     

Contamination of pigs by nose-to-nose contact or airborne transmission of Salmonella Typhimurium.

The aim of this study is to assess the risk of contamination by Salmonella Typhimurium of pigs by nose-to-nose contact or the airborne route. Thirty twelve-week-old SPF pigs were divided into 4 groups housed in 4 different rooms: the first room contained Salmonella-free control pigs (n = 4), the second room had 10(3) CFU S. Typhimurium inoculated pigs (n = 5) and non-inoculated "contact" pigs (n = 4), the third room had pigs (n = 8) receiving potentially contaminated air from the following room through a hole (4 pigs housed in the pen situated near the hole and 4 pigs in the pen at the opposite side of the room), and the fourth room had pigs (n = 5) inoculated with 10(6) CFU Salmonella Typhimurium and also non inoculated "contact" pigs (n = 4). The "contact" and the inoculated pigs were housed in adjacent pens allowing nose-to-nose contact. The 5 pigs orally inoculated with 10(6) CFU S. Typhimurium were bacteriologically and serologically positive 1 week later and their environment was contaminated as early as 1 day pi. The faecal samples of 4 nose-to-nose contact pigs were bacteriologically positive and one of them was seropositive 5 weeks pi before the pigs were commingled. The 8 pigs housed in the third room received S. Typhimurium by an active airflow coming from the contaminated room (1000 m3/hour). Their faecal samples remained negative until 8 weeks pi but the environmental swabs taken in the room close to the airinlet were contaminated 2 days pi and positive swabs were found elsewhere in the room 5 weeks pi. Two seropositive pigs were encountered 8 weeks pi in the pen situated near the hole. Only one among the 5 pigs inoculated with 10(3) CFU had bacteriologically positive faeces 1-week pi and the 4 pigs kept in nose-to-nose contact with them remained negative. A dose of 10(3) CFU was too small to induce persistent excretion and to stimulate a humoral immune response. However, the dose of 10(6) CFU induced contamination of nose-to-nose contact pigs and contamination of the environment by airflow.     

Effects of dietary humic substances on pig growth performance, carcass characteristics, and ammonia emission

Five experiments were conducted to test the effects of various dietary humic substances (HS; HS1, 2, 3, and 4, each with different fulvic and humic acid contents) on pig growth, carcass characteristics, and ammonia emission from manure. In Exp. 1, 120 pigs were allotted to 3 dietary treatments without HS (control) or with HS1 at 0.5 and 1.0% (8 pens/treatment and 5 pigs/pen) and fed diets, based on a 5-phase feeding program, from weaning (d 21.3 +/- 0.3 of age) to 60 kg of BW. In Exp. 2 and 3, 384 pigs (192 for each experiment) were allotted to 3 dietary treatments without HS, with HS1, or with HS2 (0.5%) for Exp. 2 and without HS, or with HS3 or HS4 (0.5%) for Exp. 3 (8 pens/treatment and 8 pigs/pen in each experiment). Pigs were fed diets, based on a 6-phase feeding program, from weaning (25.4 +/-0.2 and 23.6 +/-0.3 d of age for Exp. 2 and 3, respectively) to 110 kg of BW. In Exp. 4, 96 pigs were weaned at 22.1 +/-0.2 d of age and allotted to 2 treatments without or with HS1 at 0.5% (6 pens/treatment and 8 pigs/pen), and in Exp. 5 96 pigs were weaned at 20.9 +/-0.3 d of age and allotted to 3 treatments without HS, or with HS3 or HS4 (0.5%; 4 pens/treatment and 8 pigs/pen). Pigs were fed the diets for at least 2 wk before they were moved to an environmental chamber to measure aerial ammonia and hydrogen sulfide for 48 h at 5-min intervals. In Exp. 1, pigs fed diets with HS1 at 0.5% had greater (P < 0.05) ADG during phase 3 and greater (P < 0.05) G:F during phases 3 and 5 than control pigs. In Exp. 2, pigs fed diets with HS1 or HS2 at 0.5% had greater (P < 0.05) ADG and G:F than control pigs during the entire feeding period, whereas in Exp. 3 HS3 or HS4 did not improve pig growth performance. Ammonia emission from manure was reduced by 18 or 16% when pigs were fed diets with HS1 (P = 0.067) or HS4 (P = 0.054), respectively. The results of this study indicate that the effects of dietary HS are variable but may improve growth performance of pigs and reduce ammonia emission from manure. Further research is needed to clarify these effects and the mechanisms by which HS may cause them.     

Effects of feeder-trough space and variation in body weight within a pen of pigs on performance in a wean-to-finish production system

Two studies were carried out with the same group of pigs within a wean-to-finish system. In Study 1 (weaning to wk 8 postweaning), the effect of feeder-trough space in pens that were double-stocked on pig growth was evaluated. In Study 2 (end of wk 8 to 112 +/- 1.5 kg BW), the effect of variation in pig BW within a pen on growth was investigated. In Study 1, a randomized block design was used to compare two feeder-trough space treatments (Double [4 cm/pig] vs Control [2 cm/pig]). Pigs (n = 1,728) were randomly allocated at weaning (5.4 +/- 0.01 kg BW; 16 d of age) to mixed-sex pens (8 pens/treatment) of 108 pigs/pen on the basis of BW. Floor-space (0.30 m2/pig) and drinker allocation (13 pigs/drinker) were the same for both treatments. Two six-place (35 cm/place) feeders were positioned together in the center of each pen and were accessible from both sides. For the Double treatment, both feeders contained feed, whereas for the Control only one feeder contained feed. In Study 2, a randomized block design was used to compare three BW/variation in BW treatments: 1) Heavy BW/Low variation, 2) Light BW/Low variation, and 3) Mixed BW/Normal variation. The double-stocked pens of pigs from within previous feeder-trough space treatment were split into two groups of 54 pigs (equal sex ratio) having either high or low BW variation within pen. Pigs had free access to feed and water throughout the studies. In Study 1, doubling feeder-trough space did not affect (P > 0.05) pig growth from weaning to the end of wk 6. From wk 6 to 8, pigs on the Double treatment compared to the Control treatment had higher (P < 0.05) ADG and were heavier (P < 0.05), but had similar (P > 0.05) ADFI and gain:feed ratio. In Study 2, pen-BW treatment did not impact (P > 0.05) ADG or gain:feed ratio; however, Heavy/Low had greater (P < 0.01) ADFI than Light/Low with Mixed/Normal being intermediate for ADFI. At 112 kg BW, CV of BW within a pen was similar (P > 0.05) across treatments; however, days to market BW was greater (P < 0.001) for Light/Low than Heavy/ Low with Mixed/Normal being intermediate. In summary, increasing feeder-trough space from 2 to 4 cm per pig increased daily gain after wk 6 postweaning in double-stocked pens of pigs; however, sorting pigs on the basis of BW when splitting pens did not impact growth rate or variation in BW within a pen at market BW.     

Factors affecting agonistic interactions of weanling pigs after grouping in pens with a tire

The effects on agonistic interactions of installing a tire in a pen with 24 weanling pigs allocated to six pens, with four animals in each, were determined. At the first grouping, two pigs were transferred from each pen to another pen where non‐littermates existed. Then half of the pens were equipped with a tire (Grouping 1). After one week, the pigs transferred at Grouping 1 were again transferred to other pens were non‐littermates existed (Grouping 2). At Grouping 2, any pen was not newly equipped with a tire and no pig was exposed to a tire for the first time. After another week, the pigs transferred at the previous groupings were once more transferred to other pens where non‐littermates existed (Grouping 3). At Grouping 3, the pigs in the pens with a tire were transferred to pens without a tire, and the pigs in the pens without a tire were transferred to pens with a tire. Then all pens were equipped with a tire. In Grouping 1, the effects on agonistic interactions of installing a tire were not significant. However, the injury score (less the score, less the number and damage of injury) was higher in the pens without a tire than in the pens with a tire (P < 0.05). In Grouping 2, pigs in the pens with a tire were attacked more than pigs in the pens without a tire (P < 0.05). The number of agonistic behaviors positively correlated with access to the tire (r_s = 0.31; P < 0.01). In Grouping 3, the number of attacks received by pigs with no experience in using a tire was larger on the first day after grouping than on the 4th day (P < 0.05). The injury score was higher for pigs being transferred than for pigs not being transferred (P < 0.05). In conclusion: (i) installing a tire in a pen did not reduce the agonistic interactions of pigs, but it could change the style of their attacks, and (ii) initially having pigs experienced in using a tire can be useful for reducing the damage caused by agonistic interactions.     

Tail-in-mouth Behaviour Among Weaner Pigs in Relation to Age,Gender and Group Composition Regarding Gender

Male pigs are significantly more often found to be tail-bitten at slaughter than are females. Age is also thought to be a crucial factor in relation to the ontogeny of tail-biting among slaughter pigs. Tail-in-mouth behaviour (TIM) among young pigs is probably the precursor of the damaging tail-biting in older pigs. Hence, this experiment aimed to elucidate the frequency of TIM in relation to gender, age and group composition regarding gender in weaner pigs. Pigs were reared in groups of 24 until 5 weeks of age and then divided into three groups: (A) eight female pigs, (B) eight castrated male pigs and (C) four female and four castrated male pigs (mixed pen). Observations was performed through video-recording 12 h per day, 1 day per week, for 4 consecutive weeks. The number of TIM events (counts) as well as the identity of the performer and the receiver of TIM were recorded. The results showed that the level of TIM activity in the single-gender pens was significantly lower than in the mixed pen (P<0.05). In the mixed pen, TIM tended to be more directed towards the opposite gender and female pigs tended to perform more TIM than the males. Finally, the frequency of TIM increased significantly with age in all three pens (P<0.01).     

Effects of increasing dietary L-carnitine on growth performance of weanling pigs

Four experiments were conducted to evaluate the effects of supplementing graded levels (0 to 100 ppm) of L-carnitine to the diet of weanling pigs on growth performance during a 34- to 38-d experimental period. A fifth experiment was conducted to determine the effects of addition of L-carnitine to diets with or without added soybean oil (SBO) on growth performance. In Exp. 1, 128 pigs (initial BW = 5.5 kg) were allotted to four dietary treatments (six pens per treatment of four to six pigs per pen). Dietary treatments were a control diet containing no added L-carnitine and the control diet with 25, 50, or 100 ppm of added L-carnitine. In Exp. 2, 3, and 4, pigs (4.8 to 5.6 kg of BW) were allotted to five dietary treatments consisting of either a control diet containing no added L-carnitine or the control diet with 25, 50, 75, or 100 ppm of added L-carnitine. All diets in Exp. 1 to 4 contained added soybean oil (4 to 6%). There were seven pens per treatment (four to five pigs per pen) in Exp. 2, whereas Exp. 3 and 4 had five and six pens/treatment (eight pigs per pen), respectively. In general, dietary carnitine additions had only minor effects on growth performance during Phases 1 and 3; however, dietary L-carnitine increased (linear [Exp. 1], quadratic [Exp. 2 to 4], P < 0.03) ADG and gain:feed (G:F) during Phase 2. The improvements in growth performance during Phase 2 were of great enough magnitude that carnitine addition tended to increase ADG (linear, P < 0.10) and improve G:F (quadratic, P < 0.02) for the entire 38-d period. In Exp. 5, 216 weanling pigs (5.8 kg of BW) were allotted (12 pens/treatment of four to five pigs per pen) to four dietary treatments. The four dietary treatments were arranged in a 2 x 2 factorial with main effects of added SBO (0 or 5%) and added L-carnitine (0 or 50 ppm). Pigs fed SBO tended (P < 0.07) to grow more slowly and consumed less feed compared with those not fed SBO, but G:F was improved (P < 0.02). The addition of L-carnitine did not affect (P > 0.10) ADG or ADFI; however, it improved (P < 0.03) G:F. Also, the increase in G:F associated with L-carnitine tended to be more pronounced for pigs fed SBO than those not fed SBO (carnitine x SBO, P < 0.10). These results suggest that the addition of 50 to 100 ppm of added L-carnitine to the diet improved growth performance of weanling pigs. In addition, supplemental L-carnitine tended to be more effective when SBO was provided in the diet.     

Effect of Early Rearing Environment and Tail Docking on Later Behaviour and Production in Fattening Pigs

Abstract

The effect of early rearing environment and tail docking on behaviour and production of fattening pigs was investigated in 576 cross-bred pigs. Half of the pigs came from four commercial pig units with tethered or otherwise confined sows, 4 weeks' weaning, little space per piglet and no use of straw. The other half of the pigs came from another four commercial units with loose-housed sows, 5-6 weeks' weaning and liberal space and use of straw. Half of the piglets from each of the units were tail docked. At an average weight of 33.5 kg the pigs were transferred to environmentally rich experimental pens where they stayed until slaughter at approx. 100 kg liveweight. On 8 observation days evenly distributed during the fattening period the pigs' use of the straw sections of the experimental pens was recorded as well as oral activities directed towards pen mates, including tail biting. The pigs' use of the pen's straw section declined significantly (p < 0.005) during the fattening period. The rearing environment had a significant effect on nibbling on pen mates (p <0.04) but not on tail biting. The nibbling on pen mates decreased (p < 0.02) while tail biting increased (p < 0.03) during the fattening period. The tail status had no significant effect on either of the two behavioural parameters. Neither rearing environment nor tail status influenced the relative growth rate. Pigs recruited from the “barren” environment showed an almost statistically significant higher incidence of chronic pleuritis (p = 0.069).     

Effect of feed withdrawal prior to slaughter on prevalence of gastric ulcers in pigs

OBJECTIVE: To determine whether withdrawing feed from pigs prior to slaughter had any effects on prevalence or severity of gastric ulcers. DESIGN: Split-plot design. ANIMALS: 873 pigs. PROCEDURES: At the finishing barn, pigs were assigned to 30 pens. Feed withdrawal times (0, 12, or 24 hours) were assigned to pens at random, and pigs in each pen were marketed in 3 groups over a period of 4 weeks. The first marketing group consisted of the 10 heaviest pigs in each pen, the second consisted of the next 10 heaviest, and the third consisted of all remaining pigs. Feed was withheld from all pigs in each pen prior to removal of each marketing group. Thus, feed was withheld once, twice, or 3 times for pigs in the first, second, and third marketing groups, respectively. RESULTS: Feed withdrawal time was not significantly associated with ulcer score at the time of slaughter. Ulcer scores and prevalence of chronic damage were higher in the third marketing group, regardless of feed withdrawal time. Prevalence of severe damage, prevalence of chronic damage, and prevalence of esophageal constriction increased as carcass weight decreased. No pigs died of gastric ulceration. CONCLUSION AND CLINICAL RELEVANCE: Results suggest that withdrawal of feed from pigs prior to slaughter does not increase damage to the stomach and that repeated feed withdrawal does not result in fatal gastric ulceration.     

The effect of removing animals for slaughter on the behaviour of the remaining male and female pigs in the pen

The study was performed to investigate changes in the behaviour of male and female pigs when one or more pigs were removed from the pen and sent to slaughter. Twelve pens were included, half of them housed six female pigs each, while the other half housed six male pigs each. Skin lesions and behaviour were recorded on two occasions, four days before and two days after one or more animals per pen were sent to slaughter. On the first occasion the male pigs fought on average about twice as often as the females (2.6 vs. 1.0 per animal per hour) and had twice as many skin lesions (6.7 vs. 3.2). On the second occasion, the frequency of fighting among both males (6.8) and females (1.8) had increased, however, more in males than in females. The number of skin lesions was not significantly higher on the second occasion. In the male group there was also a tendency towards increased mounting on the second occasion (from 2.3 to 3.3 per animal per hour). The study shows that the very common practice of slaughtering pigs from one pen over more than one occasion results in an increase in unwanted behaviour. The effect is more pronounced in groups of entire male pigs than in groups of females.     

Evaluation of aerosol transmission of porcine reproductive and respiratory syndrome virus under controlled field conditions

The aim of this study was to determine whether porcine reproductive and respiratory syndrome virus (PRRSV) could be transmitted by aerosol under field conditions. A total of 210 five-month-old PRRSV-negative pigs were housed in a mechanically ventilated finishing facility containing 11 pens. Pen 1 contained 10 pigs (indirect contact controls) and pen 2 remained empty, providing a barrier of 2.5 m from the remaining pigs in pens 3 to 11. Fifteen or 16 of the pigs in each of pens 3 to 11 were infected experimentally with a field isolate of PRRSV and the other six or seven pigs served as direct contact controls. Five days after the pigs were infected, two trailers containing 10 five-week-old PRRSV-naive sentinel pigs were placed along each side of the building; one was placed 1 m from the exhaust fans on one side of the building, and the other was placed 30 m from the fans on the other side, and the sentinel pigs remained in the trailers for 72 hours. They were then moved to separate buildings on the same site, 30 and 80 m, respectively, from the infected barn, and their PRRSV status was monitored for 21 days. The direct and indirect contact control pigs became infected with PRRSV but the sentinel pigs did not.     

Transmission of classical swine fever virus within herds during the 1997-1998 epidemic in The Netherlands

In this paper, we describe the transmission of Classical Swine Fever virus (CSF virus) within herds during the 1997–1998 epidemic in the Netherlands. In seven herds where the infection started among individually housed breeding stock, all breeding pigs had been tested for antibodies to CSF virus shortly before depopulation. Based upon these data, the transmission of CSF virus between pigs was described as exponential growth in time with a parameter r, that was estimated at 0.108 (95% confidence interval (95% CI) 0.060–0.156). The accompanying per-generation transmission (expressed as the basic reproduction ratio, R₀) was estimated at 2.9. Based upon this characterisation, a calculation method was derived with which serological findings at depopulation can be used to calculate the period in which the virus was with a certain probability introduced into that breeding stock. This model was used to estimate the period when the virus had been introduced into 34 herds where the infection started in the breeding section. Of these herds, only a single contact with a herd previously infected had been traced. However, in contrast with the seven previously mentioned herds, only a sample of the breeding pigs had been tested before depopulation (as was the common procedure during the epidemic). The observed number of days between the single contact with an infected herd and the day of sampling of these 34 herds fitted well in the model. Thus, we concluded that the model and transmission parameter was in agreement with the transmission between breeding pigs in these herds.

Because of the limited sample size and because it was usually unknown in which specific pen the infection started, we were unable to estimate transmission parameters for weaned piglets and finishing pigs from the data collected during the epidemic. However, from the results of controlled experiments in which R₀ was estimated as 81 between weaned piglets and 14 between heavy finishing pigs (Laevens et al., 1998a. Vet. Quart. 20, 41–45; Laevens et al., 1999. Ph.D. Thesis), we constructed a simple model to describe the transmission of CSF virus in compartments (rooms) housing finishing pigs and weaned piglets. From the number of pens per compartment, the number of pigs per pen, the numbers of pigs tested for antibodies to CSF virus and the distribution of the seropositive pigs in the compartment, this model gives again a period in which the virus most probably entered the herd. Using the findings in 41 herds where the infection started in the section of the finishers or weaned piglets of the age of 8 weeks or older, and of which only a single contact with a herd previously infected was known, there was no reason to reject the model. Thus, we concluded that the transmission between weaned piglets and finishing pigs during the epidemic was not significantly different from the transmission observed in the experiments.     

The effect of air movement on the activity, lying position and huddling behaviour of weaned piglets

An experiment was carried out in a 55-sow, specific pathogen-free commercial unit, to observe the behavioural adaptation of newly weaned pigs (7 to 10 kg) to air movement in a typical weaner pen. Direct air currents were generated by a fan placed at 4 positions around the pen. Observations were made of activity, lying position, huddling and orientation. Increased activity was observed when the wind was directed on to the preferred lying area of the pigs. The pigs usually moved out of the region of greatest air movement and indirect currents appeared to be more favourable. Wind inhibited huddling in the pigs when it was directed over the lying area but orientation was unaffected. Social factors were important in the choice of lying position. The percentage of pigs huddling gave a behavioural indication of the suitability of the husbandry environment for production and welfare.     

Effect of mixed rearing of barrows and gilts on backfat thickness and serum metabolite profiles of the Kagoshima-Kurobuta (Berkshire) pig

We investigated the effect of mixed rearing of barrows and gilts on the backfat thickness and the serum metabolite profiles of Kagoshima-Kurobuta (Berkshire) pigs. A total of 149 pigs with an average body weight of 35 kg were divided into the following groups: 100%, 90%, 70%, 50%, 30%, 10%, and 0% groups consisting of 10 barrows (1 pen), 9 barrows + 1 gilt (3 pens), 7 barrows + 3 gilts (2 pens), 5 barrows + 5 gilts (3 pens), 3 barrows + 7 gilts (2 pens), 1 barrow + 9 gilts (3 pens), and 9 gilts (1 pen), respectively. All pigs were raised to a shipping weight of 120 kg. Mixed rearing significantly reduced (p < 0.001) backfat thickness, and the optimum mixing ratio of barrows and gilts was 7:3 (the 70% group). Four types of circulating sex steroids were found in both the barrows and gilts in the 50% group but were not detected in barrows from the 100% group. These results indicated that mixed rearing of barrows and gilts was effective for reducing the backfat thickness of barrows, and induced sex steroid hormones may influence the backfat thickness of barrows in mixed-reared groups.     

Reduced diet crude protein level, benzoic acid and inulin reduced ammonia, but failed to influence odour emission from finishing pigs

Intensified pig production is associated with odour and ammonia emissions causing nuisance and environmental concerns. The aim of four experiments was to investigate the effect of different dietary interventions on odour and ammonia emissions from finishing pigs. In exp. 1, diet crude protein levels of 16% and 14% were compared. In exps. 2 and 3, the effect of adding 1% and 3% benzoic acid, respectively, to the diets was studied. In exp. 4, inclusion of 15% inulin in the diet was investigated. All experiments were carried out in two identical climate chambers with three pens. There were 12 pigs per pen in total 36 pigs per chamber. Each dietary treatment was repeated two times. The temperature, ventilation rate and concentrations of NH₃ in the exhaust air were measured every hour. Odour concentration was measured in samples of the exhaust air by olfactometry. Reduced diet crude protein, the addition of 3% benzoic acid and inclusion of 15% inulin reduced ammonia emission by 30%, 57% and 34%, respectively. It was not possible to influence odour emission in any of the experiments.     

Association between the existence of calves persistently infected with bovine viral diarrhea virus and commingling on pen morbidity in feedlot cattle

OBJECTIVE: To determine the association between the existence of a calf persistently infected (PI) with bovine viral diarrhea virus (BVDV) and pen morbidity. ANIMALS: 5,041 calves in 50 pens at a feedlot in Iowa. PROCEDURE: In a longitudinal study, ear notches were collected from cattle and tested for BVDV antigen. Characteristics of each pen (owner, sex, disease rate, number of groups, and source) were recorded. The association between the existence of a BVDV-PI calf and morbidity in each pen was examined. RESULTS: Commingling was associated with an increase in respiratory tract disease (odds ratio [OR], 3; 95% confidence interval [CI], 2.5 to 3.6). Ten BVDV-PI calves (10/5,041 [0.2%]) were identified in 8 of 50 pens. A BVDV-PI calf was associated with reduced pen-level respiratory tract disease (OR, 0.7; 95% CI, 0.5 to 0.9). Disease prevalence (mean +/- SD morbidity, 7.9 +/- 3.1%) was lowest in pens containing single-source cattle and a BVDV-PI calf (4 pens containing 302 cattle), compared with single-source cattle with no BVDV-PI calf (mean morbidity, 11.89 +/- 9.7%; 31 pens containing 3,093 cattle), commingled cattle with no BVDV-PI calf (mean morbidity, 29.3 +/- 16.22%; 11 pens containing 1,127 cattle), and commingled cattle with a BVDV-PI calf (mean morbidity, 28.6 +/- 10.1%; 4 pens containing 519 cattle). CONCLUSIONS AND CLINICAL RELEVANCE: Commingling was the greatest risk factor associated with morbidity in each pen. A BVDV-PI calf in a pen was not associated with increased disease prevalence in commingled groups.     

The effects of ractopamine on the behavior and physiology of finishing pigs

The objectives of this study were to examine the effects of ractopamine (RAC) on the behavior and physiology of pigs during handling and transport. Twenty-four groups of three gilts were randomly assigned to one of two treatments 4 wk before slaughter: finishing feed plus RAC (10 ppm) or finishing feed alone. Pigs were housed in the same building in adjacent pens with fully slatted floors and ad libitum access to feed and water. Behavioral time budgets were determined in six pens per treatment over a single 24-h period during each week. Behavioral responses of these pigs to routine handling and weighing were determined at the start of the trial and at the end of each week. Heart-rate responses to unfamiliar human presence were measured in all pigs and blood samples were taken from a single pig in each pen on different days during wk 4. At the end of wk 4, all pigs were transported for 22 min to processing. Heart rate was recorded from at least one pig per pen during transport and a postmortem blood sample was taken from those pigs that were previously sampled. During wk 1 and 2, RAC pigs spent more time active (P < 0.05), more time alert (P < 0.05), and less time lying in lateral recumbency (P < 0.05). They also spent more time at the feeder in wk 1 (P < 0.05). At the start of the trial, there were no differences in behavioral responses to handling. However, over each of the next 4 wk, fewer RAC pigs exited the home pen voluntarily, they took longer to remove from the home pen, longer to handle into the weighing scale and needed more pats, slaps, and pushes from the handler to enter the scales. At the end of wk 4, RAC pigs had higher heart rates in the presence of an unfamiliar human (P < 0.05) and during transport (P < 0.05), but not during loading and unloading. Also at the end of wk 4, RAC pigs had higher circulating catecholamine concentrations (P < 0.05) than control pigs. Circulating cortisol concentrations and cortisol responses to transport did not differ between treatments. The results show that ractopamine affected behavior, heart rate, and catecholamine profile of finishing pigs and made them more difficult to handle and potentially more susceptible to handling and transport stress.     

Effect of withdrawing feed from swine on meat quality and prevalence of Salmonella colonization at slaughter

OBJECTIVE: To determine whether withholding feed from pigs prior to slaughter had any effects on meat quality, percentage of pigs with Salmonella spp in cecal contents during slaughter, or percentage of pigs with lacerations of the gastrointestinal tract during slaughter. DESIGN: Split-plot design. ANIMALS: 873 pigs. PROCEDURES: At the finishing barn, pigs were assigned to 30 pens. Feed withdrawal times were assigned to pens at random, and pigs in each pen were marketed in 3 groups. The first marketing group consisted of the 10 heaviest pigs in each pen, the second consisted of the next 10 heaviest pigs, and the third consisted of all remaining pigs. RESULTS: Withdrawing feed improved the redness score assigned to the meat but did not have any other significant effects on carcass composition or meat quality. The percentage of pigs with Salmonella spp in the cecal contents decreased from the first (73%) to the second (64%) to the third (52%) marketing group. However, isolation of Salmonella spp from cecal contents was not associated with feed withdrawal time or with pen prevalence of Salmonella shedding during the 2 months prior to slaughter. Feed withdrawal time and marketing group did not have any significant effects on overall prevalence of gastrointestinal tract lacerations. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that withdrawal of feed from pigs prior to slaughter does not increase the prevalence of Salmonella colonization or the risk of carcass contamination associated with gastrointestinal tract lacerations during slaughter but only slightly enhances meat quality.