Exposure variability of fosfomycin administered to pigs in food or water: Impact of social rank

The objective of this study was to document the effect of social ranking on the internal exposure of pigs to an antibiotic (fosfomycin) administered either in food or in drinking water. Signs of aggression were recorded at the feeder and drinker. The interindividual variability explained by the social rank was even greater when the test antibiotic was given in food despite the fact that the water consumption was less variable than the food intake. The range of plasma concentrations after administration of fosfomycin either in food or drinking water leads to a number of pigs in the treated group being exposed to rather low and highly variable concentrations of fosfomycin and not able to maintain adequate plasma concentrations above the typical minimum inhibitory concentration (MIC). Social rank clearly influences the level of exposure of pigs to fosfomycin both in food and drinking. However, its administration in drinking water is likely to be the best option to optimize antibiotic efficacy.     

Human-directed aggression in miniature pet pigs

OBJECTIVES: To determine whether associations exist between human-directed aggression and sex, neutering status, age of weaning, the presence of other pet pigs, or the presence of environmental enrichment objects in miniature pet pigs. DESIGN: Internet survey. STUDY POPULATION: Responses from 222 owners of miniature pet pigs. PROCEDURES: Pet pig owners were requested to complete a 48-item multiple-choice and short-answer Internet survey for each pig that they presently owned. RESULTS: Among 222 surveys that met enrollment criteria, human-directed aggression that occurred on at least 1 occasion was reported in 64% (n = 142) and aggression that occurred once or more per month was reported in 31% (69). No significant differences were found in the prevalence of human-directed aggression among castrated males, sexually intact females, and spayed females. Ages of weaning and neutering and the presence of objects intended to serve as environmental enrichment were not associated with frequency of aggression. A significant inverse association was detected between presence of other pigs in the same household and human-directed aggression, such that 21% (20/95) of pigs that lived with at least 1 conspecific were aggressive on a frequent basis, compared with 39% (49/126) of pigs that lived with no conspecific. A similar inverse association was evident regarding aggression that occurred on at least 1 occasion. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested that human-directed aggression is a common problem in miniature pet pigs. The presence of a conspecific can be expected to reduce the likelihood of human-directed aggression.     

Time budgets of group-housed pigs in relation to social aggression and production

Commercial producers house growing pigs by sex and weight to allow for efficient use of resources and provide pigs the welfare benefits of interacting with their conspecifics and more freedom of movement. However, the introduction of unfamiliar pigs can cause increased aggression for 24 to 48 h as pigs establish social relationships. To address this issue, a better understanding of pig behavior is needed. The objectives of this study were to quantify time budgets of pigs following introduction into a new social group and how these changed over time and to investigate how social aggression influences the overall time budgets and production parameters. A total of 257 grow-finish Yorkshire barrows across 20 pens were introduced into new social groups at 10 wk of age (~23 kg) and observed for aggression and time budgets of behavior at four periods: immediately after introduction and 3, 6, and 9 wk later. Pigs were observed for the duration of total aggression and initiated aggression (s) for 9 h after introduction and for 4 h at 3, 6, and 9 wk later. Time budgets were created by scan sampling inactive, movement, ingestion, social, and exploration behaviors every 2 min for 4 h in the afternoon and summarizing the proportion of time each behavior was performed by period. The least square means of each behavior were compared across time points. Pigs spent most of their time inactive. In general, the greatest change in pig behavior was observed between introduction and week 3 (P < 0.003), with gradual changes throughout the study period as pigs became more inactive (week 3 vs. week 6: P = 0.209; week 6 vs. week 9: P = 0.007) and spent less time on other behaviors. Pigs’ nonaggressive behavior and production parameters were compared with aggression using generalized linear mixed models. The time pigs spent on nonaggressive behaviors was negatively related to aggression (P < 0.045) with few exceptions. Initiated aggression after introduction was negatively related to loin muscle area (P = 0.003). These results show how finishing pigs spend their time in commercial facilities and indicate that behavior continues to change for up to 9 wk after introduction into a new social group. Efforts to reduce chronic levels of aggression should focus on promoting nonaggressive behaviors, such as exploration and movement, after the initial fighting that occurs immediately after introduction has waned, and should be implemented for up to 9 wk after introduction into new social groups.     

Effects of Acclimate™ on the frequency and duration of aggressive sequence and growth performance in co-mingled, weaned pigs

Co-mingling weaned pigs often results in aggressive behavior which can result in injury and reduced performance. This experiment examined the effect of Acclimate™, a product reported to reduce equine aggression, on weaned pig aggression and growth performance. Weanling pigs (n=214, avg. wt.=5.93 kg) were blocked by weight, sex and litter (n=25) and randomly assigned to either Acclimate™ treatment or a control group. Acclimate™ treated pigs were marked on the nose, face and neck. Pigs were individually identified and videotaped to determine frequency of aggressive sequence (FAS) and duration of aggression (DOA) on an individual pig basis. Pig weights and feed consumption were used to determine feed intake, total weight gain (TWG), average daily gain (ADG) and feed to gain ratio (F/G). Differences between litter, sex and treatment for FAS, DOA, F/G and ADG were tested using GLM, SAS. Neither Acclimate™ treatment or sex had a significant effect on FAS, TWG or F/G. However, there was a trend towards reduced duration and intensity of aggression in Acclimate™ treated pigs (p=0.1). There was a significant effect of litter (p<0.01) and TWG (p<0.001) on FAS at both 1 and 3 weeks. Acclimate™ treatment of weaned pigs does not decrease FAS, but may decrease the intensity and duration of aggression without negatively effecting growth.     

Pharmacokinetics of lithium in the dog

The pharmacokinetics of lithium were determined in eight adult dogs. The data were fitted to a two-compartment model. Single intravenous doses of lithium chloride, and single oral doses of lithium carbonate were used. The mean plasma lithium half-life (t1/2) following the single intravenous dose was 21.6 h, and the mean apparent specific volume of distribution of the central compartment (V'c) was 0.189 l/kg. Mean bioavailability was 78.8% following oral administration.     

Effects of lithium carbonate administration to healthy cats.

Lithium carbonate administration to healthy cats was evaluated in 2 controlled studies (a dose-response study and a bone marrow evaluation study) to determine the effectiveness of lithium as a bone marrow stimulant. Lithium carbonate was administrated at dosage ranging from 300 to 1,050 mg/m2 of body surface/d. Complete blood count, serum lithium concentration determination, serum biochemical analysis, urinalysis, and bone marrow aspiration and biopsy were periodically performed. Serum lithium concentration greater than 2 mEq/L was associated with significant decrease in numbers of circulating segmented neutrophils (less than 1,200 cells/microliter; P less than 0.01) and lymphocytes (less than 1,300 cells/microliter; P less than 0.0001), as well as significant (P less than 0.05) decrease in urine specific gravity. Bone marrow evaluation revealed apparent maturation arrest of the neutrophil cell line. Coincident with the changes in laboratory values, the lithium-treated cats became ill. Changes in behavior and vocalization were seen, followed by anorexia, vomiting, and diarrhea. In later stages of intoxication, cats became hyperexcitable and manifested coarse muscular tremors. It was concluded that lithium carbonate does not have potential value as a bone marrow stimulant and is toxic to cats at serum concentration greater than 2 mEq/L.     

Use of lithium for treatment of estrogen-induced bone marrow hypoplasia in a dog.

Marrow hypoplasia and consequent pancytopenia caused by simultaneous administration of estradiol cyclopentylpropionate and diethylstilbestrol were diagnosed in a 6-year-old Old English Sheep-dog. The dog was treated with lithium carbonate (11 mg/kg of body weight, PO, q 12 h) for 6 weeks. Despite the generally grave prognosis associated with estrogen toxicosis, lithium treatment was apparently successful in inducing regeneration of the bone marrow. Side effects of lithium treatment were not noticed.     

Nutritional value of quality protein maize and food corn for starter and growth pigs

Growth traits with starter and grower pigs and a digestion trial were conducted to compare the nutritional value of Quality Protein Maize (QPM), food corn and conventional feed corn. The QPM, food and feed corn contained .45, .31 and .29% lysine, respectively. The growth trials evaluated a QPM-soybean meal diet formulated on a lysine basis (.96% in starter and .7% in grower diets) and four diets arranged in a 2 (food corn vs feed corn) X 2 (low vs high soybean meal) factorial. Soybean meal was either added in the same amount as in the QPM diet or was added to provide the lysine content of the QPM diet. Performance was similar for pigs fed food corn and feed corn in both trials. The QPM diets resulted in greater performance than food and feed corn diets containing the same level of soybean meal supplementation; starter pigs were more (P less than .10) efficient and grower pigs had a higher (P less than .01) rate and efficiency of gain. However, performance of pigs fed the QPM diets was not equal to that of pigs fed isolysinic food and feed corn diets; growth rate was lower (P less than .05) in starter pigs and gain:feed was lower (P less than .05) in grower pigs. Diets in the digestion trial consisted of the corns plus 3.25% casein. Energy digestibility was similar for all diets. Ileal N and amino acid digestibilities were highest for QPM, intermediate for food corn and lowest for feed corn. In most instances, these differences were significant (P less than .05). Apparent biological value was highest (P less than .05) for QPM. These trials indicate that food corn and feed corn have similar nutritional value, and that starter and grower pigs can benefit from the higher protein quality of QPM.     

Effects of feeding systems on social and feeding behavior and performance of finishing pigs

Two experiments were conducted to study the effects of feeding systems on feeding behavior, aggression, social ranks and average daily gain (ADG) of pigs. In Exp. 1, feed was delivered during the day from 1100 to 1400 and at night from 2300 to 0200. One pen containing 10 barrows and 10 gilts was used. Correlation coefficients were calculated between pairs of traits. In Exp. 2, four feeding systems were tested using similar group composition as in Exp. 1. Two feeding systems were ad libitum, offering either dry or wet feed; the other two used time-restricted feeding from 0900 to 1100 and from 1600 to 1800, but with water supplied either ad libitum or time-restricted. Analyses of variance were used to test feeding system effects; correlation coefficients were calculated for pairs of traits. Results of Exp. 1 indicated that pigs displayed predominantly daytime activities. Frequency of aggressive acts were correlated significantly with feeding frequency (r = .48), time to first feeding (r = -.50) and ADG (r = .56). In Exp. 2, pigs on time-restricted feeding with ad libitum water had significantly depressed ADG and reduced feed intake. A possible association between time-restricted feeding and water intake is postulated. Feeding behavior, aggression and social rank were associated with ADG in time-restricted systems but not in ad libitum systems. There was a tendency in time-restricted-fed pigs for the more aggressive pigs to perform more feeding activities, to rank higher in the social order, and to gain faster.     

Retention of Selenium in Kidneys,Liver and Striated Muscle After Prolonged Feeding of Therapeutic Amounts of Sodium Selenite to Pigs

Sodium selenite was mixed in a commercial pig food so as to increase the original selenium content (0.126 ppm) by 1.2 ppm. The supplemented food was given to 7 pigs during 78 days. A control group of as many pigs was given the non-supplemented commercial food. The pigs were killed, starting 4 hours after the last selenium-supplemented food had been given and then with intervals during the next 14 days. Small but significant increases of tissue selenium were noticed in liver and striated muscle as compared with the control animals. The kidneys showed no increase.     

Aggressive and sexual behaviour of growing and finishing pigs reared in groups,without castration

Abstract

Aggressive and sexual behaviour in entire males and females were studied on 408 pigs. The sum of aggressive interactions in the pen during routine feeding (ALP) was lowest in single-sex pens with females. ALP was higher at 132 than at 155 days. High ALP correlated with high average growth rate. Aggressive interactions in a competition test (IA) increased after slaughter of the three fastest-growing pigs in a pen (at 155 days), although the slaughtered pigs had initiated the most IA earlier (at 132 days). Entire male pigs displayed more sexual behaviour (mounting) than females. In 15% of entire males and 6% of females there were health problems specifically involving lameness or injured legs or feet. Five entire males and one female were euthanized in response to lameness or leg fracture. The rearing of entire male pigs may cause welfare problems, given their higher levels of aggression and sexual behaviour.     

Use of supplementary tryptophan to modify the behavior of pigs

Three experiments were conducted to investigate the short-term use of supplementary Trp on the behavior of grow/finish pigs. Three levels of dietary Trp were used, representing the standard requirement for growth (control), twice (2x), and 4 times (4x) the control amount. In Exp. 1, pigs were fed the diets for 7 d, during which observations were made of their general behavior (time budget), aggression within the group of familiar pigs, and response to a startling auditory stimulus. Behavior effects were evident during the period of supplementation for both the 2x and 4x diets. During the treatment period, pigs fed supplemental Trp spent more time lying (P = 0.04) and less time eating (P = 0.05) than pigs fed the control diet. Although the response of the animals to the startling stimulus was to become alert and stand, similar behavioral effects caused by supplemental Trp also were evident after the startling stimulus (P < 0.01). Based on these observations, the subsequent studies retained the same dietary levels of Trp and incorporated a 3-d feeding of diets before behavior testing. In Exp. 2, pigs were fed the experimental diets for 3 d before being regrouped with unfamiliar pigs on the same diet. Subsequent aggression was affected by Trp supplementation, in that high levels of dietary Trp decreased the total duration of fighting by approximately 50% (P = 0.03). Supplemental Trp had no effect on the number of fights, and there were no differences between the 2 levels of supplemental Trp on any behavior. In Exp. 3, pigs were exposed to specific handling tests on the farm and meat quality assessments after being fed the experimental diets for 3 d. There were no differences among dietary treatments for any of the meat quality characteristic variables measured. The only behavioral or physiological difference observed among the treatments was a slower movement of pigs fed the 4x Trp treatment than control or 2x Trp-fed pigs in a minimal-forced situation (P = 0.04). Response to confinement on a scale, an electric prod, and movement in general did not differ among treatments. High levels of Trp may result in animals avoiding stressful situations if possible, but they seem to have no effect on responses to stressors that animals may experience in a forced situation.     

生产性能测定站对生长猪生产性能和行为的影响

本试验旨在研究生产性能测定站对猪生产性能和行为的影响。选用平均体重为28.2 kg的大白猪122头,公、母各半,按圈随机分成3组,分别为试验1组(普通料槽15头组)、试验2组(测定站15头组)及试验3组(测定站8头组),试验1、2组各3个重复,试验3组4个重复,试验期44 d。试验前对测定站精准性进行评价;试验期间测定猪生产性能和皮肤损伤,并对猪行为进行录像。结果表明,测定站料槽和体重称量秤精准性符合其技术参数;3组之间猪生产性能均无显著差异(P>0.05),试验3组猪的末重变异系数呈下降趋势(44.48%),试验1组猪的末重、平均日增重和平均日采食量略高于试验2组;测定站极显著增加了猪的皮肤损伤评分(P<0.01),极显著增加了试验2组第1天时的攻击行为(P<0.01),极显著降低了第7天的攻击行为(P<0.01),但采食猪所占比例相对较低,试验2组显著(P<0.05)或极显著(P<0.01)提高了猪的圈友操纵行为。     

Behavioral changes in neonatal swine after an 8-hour rest during prolonged transportation

Long distance transportation of weaned piglets (Sus scrofa) is increasingly common in the united states and may result in delayed eating, drinking, or normal social behaviors. A potential solution is a mid-journey rest (lairage). The objective of this study was to determine if a lairage altered behavior after a 16-h transport. Pigs that weighed approximately 18 kg each (n = 894) were housed in 16 pens with 8 pens per treatment. Lairaged pigs were transported for 8 h and given an 8-h rest with food and water, whereas control pigs were transported continuously for 16 h. The heaviest, the lightest, and 2 average-BW pigs relative to the average weight of the pen were observed by video recording for 24 h immediately before and after transport, and during d 6 and 13 after transport. Postures (lying, sitting, and standing) were recorded using 10-min-interval scan sampling, and behavioral categories included inactivity, activities (eating, drinking, alert, manipulating pen, rooting, and walking) and social interactions (aggression, belly nosing, playing, tail biting, and positive social behaviors). In both treatments, sitting occurred most before transport (P < 0.01) than at other times, but did not differ between treatments. Standing increased (time effect; P < 0.01) for both treatments immediately after transport through d 6, but returned to pre-transport values by d 13. In contrast, lying decreased (time effect; P < 0.01) after transport, but returned to above pre-transport values by d 13. Time effects were evident for activity (P < 0.01), pen manipulation (P = 0.05), rooting (P < 0.01), initiation of belly-nosing (P = 0.01), and receiving belly-nosing (P = 0.03); however, initiation of aggression did not differ for day (P = 0.19) or treatment (P = 0.56). Lairaged pigs initiated more (P = 0.05) play than continuously transported pigs, but no differences (P = 0.84) were seen in receipt of play behavior. Pigs that were to be transported for 16 h continuously walked less pre-transport, walked more post-transport (treatment × time interaction; P = 0.02), and drank less pre-transport, but drank more on all days post-transport compared with the lairage group (treatment × time interaction; P = 0.001). This study indicated that extended transport without lairage alters some swine behaviors relevant to production (water consumption) and demonstrated that a long-duration transport, regardless of the mid-journey lairage treatment, affects a number of behaviors up to 13 d after transportation.     

Effects of amperozide and azaperone on aggression and productivity of growing-finishing pigs

Levels of aggression, activity and performance were determined in 270 pigs (initial wt 29.8 kg) injected with amperozide (1.0 mg/kg i.m.), azaperone (2.2 mg/kg i.m.) or saline (.1 ml/kg i.m.) immediately prior to mixing. Pigs had ad libitum access to feed in pens of 15, and six pens were allotted to each treatment. Each pen was video-taped for 48 h after injection. Aggression was determined by continuous observation and summarized for each 2-h period. Injuries on the ears and shoulders of each pig were scored prior to injection and 1, 2, 3 and 7 d after treatment. Eating, drinking and lying were determined by scan sampling at 2-min intervals and summarized for each 2-h period. Weight gain, feed consumption and efficiency were determined for periods ending on d 3, 7, 14, 28, 42, 56, 70 and 84. Both drugs reduced total fighting from 309.8 min for saline to 190.7 and 189.6 min for amperozide- and azaperone-treated pens, respectively (P less than .01). Treatment differences in aggression and lying were evident during the initial 6 h only. Amperozide resulted in fewer fights involving two pigs (197.3/pen) than did azaperone (260.2/pen) or saline (298.3/pen) (P less than .05). Injuries to the ears (P less than .01) and total injuries (P less than .05) were less severe in amperozide-treated pigs than in pigs on the other treatments.(ABSTRACT TRUNCATED AT 250 WORDS)     

On the effect of food magnesium level on the activity of BASP, ALAT, ASAT and LD in pig serum

Studies were made to investigate the effect of food Mg level on ALAT, ASAT, LD and BASP values in pigs. The following conclusions were drawn:--a high food Mg level (0.31% in ordinary pig food) can cause an increase in serum BASP values.--leg weakness, at the primary stage, is hardly caused by disturbances in bone.--an ordinary diet low in Mg may cause an abnormal rise in ALAT values in pigs.--when feeding pigs on an ordinary diet, pigs may suffer from Mg deficiency despite the fact that the food Mg content is distinctly higher than that recommended by international norms for feeding.--a prompt lowering of food Mg level can cause a manifest increase in ASAT, LD and BASP values within 2 to 3 days in pigs. Heart and liver injuries caused by low Mg diets and the individual ability of pits to utilize magnesium were discussed.     

THE EFFECT OF PEN DESIGN AND THE TRANQUILISING DRUG, AZAPERONE, ON THE GROWTH AND BEHAVIOUR OF WEANED PIGS

SUMMARY Two experiments were carried out in a 55-sow, specific pathogen free commercial unit, to assess the effects of the tranquilising drug, azaperone, on pigs mixed at weaning. The drug is claimed to inhibit aggression in pigs mixed at weaning, and also to increase the average weight gain in groups of growing pigs. The first experiment used a single test and control group, and the second experiment was a 2 times 2 factorial design, the variables being the presence or absence of the drug, and the presence or absence of a box used to modify the weaner pen environment. In both experiments there were no significant differences in rates of agonistic interactions between treated and untreated groups, although the drug delayed the first agonistic encounters for about 8 hours. Nor was there any difference in the relative growth rate between treated and untreated groups in either experiment.     

Energy balance and growth rate of outbred and inbred male guinea pigs

Water intake, food consumption, growth rate, and rectal temperature were measured daily for 14 days and oxygen uptake was determined weekly for 3 weeks in healthy outbred (Hartley stock) and inbred (strains 2 and 13) male guinea pigs. Body weights ranged from 300 to 465 g, and ages were approximately 6 to 10 weeks. Strain-13 guinea pigs had the lowest daily body weight gain (3.27 +/- 0.33 g), when compared with strain-2 (4.04 +/- 1.21 g) and Hartley guinea pigs (5.72 +/- 1.08 g). Outbred guinea pigs also had highest values of water intake and water/food intake ratio(s), and had significantly (P less than 0.05 and 0.01) lower oxygen uptake values than did inbred guinea pigs. The ratio of daily average body weight gain to the corresponding daily retained calories, with or without corrections of body surface area (0.05 m2), was higher in Hartley stock than in the strain-13 guinea pigs. Rectal temperatures and food consumption were similar in all guinea pigs. Data indicated that the outbred Hartley guinea pig had a faster growth rate and appeared stronger physiologically, compared with inbred strains.     

Relationship between food deprivation before transport and aggression in pigs held in lairage before slaughter

Pigs from three farms were deprived of food for up to one hour, 12 hours or 18 hours before being sent for slaughter. In lairage, the animals' behaviour was monitored, and at slaughter a blood sample was collected and analysed for cortisol, lactate and creatine phosphokinase, potential indicators of stress and physical activity. The carcases were assessed for skin damage as an index of fighting, and rigor in the hind leg as an indicator of stress and/or fatigue. Measurements were also made of cold carcase weight, backfat thickness and liver glycogen concentration. General activity was very high on entry to the lairage pen. Drinking and mounting occurred almost immediately. Fighting developed after an exploratory period, and could last up to 60 minutes. There were large differences in the behaviour of pigs from the three farms. Pigs from farm A fought frequently but showed little mounting activity, whereas pigs from farm C were involved in mounting but little fighting. The period of food deprivation had no effect on average skin damage or rigor score, but the frequency of carcases with the highest scores was different The pigs deprived of food for up to an hour had the lowest incidence of severe skin damage and high rigor scores. Boars had a higher incidence of severe skin damage but a lower incidence of carcases with a high rigor score than gilts. Liver glycogen was almost completely depleted in the pigs deprived of food for 12 and 18 hours and was lower in the pigs deprived for up to an hour than in animals fed immediately before slaughter. The period of food deprivation had no effect on the levels of cortisol, creatine phosphokinase or lactate in the blood.     

Effects of tryptophan supplementation on aggression among group-housed gestating sows

The objective of this study was to determine the effects of dietary Trp supplementation on mixing-induced aggression and the associated stress, and on reproductive performance in gestating sows. After weaning, sows were mixed in pens with electronic sow feeders on concrete-slatted floors. Each pen housed 21 ± 2.8 sows, with approximately 2.7 ± 0.43 m(2)/sow of floor space allowance. Multiparous sows (n = 168) from 8 breeding groups were used, with 4 groups assigned to a control diet and 4 groups assigned to a high-Trp diet. Control sows received corn- and soybean meal-based diets throughout gestation (0.15% Trp) and lactation (0.21% Trp). Three days before and after mixing, sows assigned to the high-Trp treatment received approximately 2.3 times the dietary Trp (0.35% in the gestation diet and 0.48% in the lactation diet) fed to control sows. Six focal sows (2 sows from each of parity 1, 2, and 3 or greater) in each pen were designated and videotaped for 72 h after mixing to determine the type and number of aggressive interactions among sows. Before and 48 h after mixing, saliva samples were collected from focal sows, and scratches were assessed on all sows. Data were analyzed using the FREQ and GLIMMIX procedures (SAS Inst. Inc., Cary, NC). Aggression among sows was intense during the initial 6 h and decreased between 6 and 72 h after mixing. The initial aggression caused scratches and increased cortisol concentrations (P < 0.05). Mature sows tended to fight for longer periods (112 vs. 52 s/h per sow, SE = 23.8; P < 0.10) but had fewer scratches caused by aggression (injury score = 4.3 vs. 6.5, SE = 1.13; P < 0.01) than parity-1 sows. Supplementation of dietary Trp reduced the total duration of head-to-head knocking (P < 0.05) but did not affect other aggressive behaviors. There was no difference between dietary treatments in injury scores or saliva cortisol concentrations. Sows in the high-Trp treatment had more total piglets born (12.5 vs. 10.5 pigs/litter, SE = 0.55; P < 0.05) and more stillborn piglets (1.5 vs. 0.8 pigs/litter, SE = 0.20; P < 0.05), but had no significant change (P = 0.12) in piglets born alive (10.8 vs. 9.7 pigs/litter, SE = 0.42) compared with control sows. The results indicate that the initial aggression after mixing caused more injuries in young sows than in mature sows. Supplementation of dietary Trp at 2.3 times the control amount for a short period did not effectively reduce aggression and the associated stress in sows at mixing.