Effects of season, truck type, and location within truck on gastrointestinal tract temperature of market-weight pigs during transport.

Two experiments were done to assess the effects of season, truck type, and location in the truck on the gastrointestinal tract temperature (GTT) of market-weight pigs during transport. In Exp. 1, a total of 504 sentinel pigs were selected from a total load of 3,756 pigs over 12 wk in summer or winter and transported in either a double-decked (DD) hydraulic truck or a pot-belly (PB) trailer for 2 h. In Exp. 2, a total of 330 sentinel pigs were selected from a total load of 2,145 pigs over 11 wk in summer or winter and transported in a PB trailer for 8 h. In both experiments, sentinel pigs were equipped with a temperature data logger for the real-time GTT recording from the farm to slaughter. Transport was divided into 8 periods in Exp. 1 (rest, pretravel, initial travel, prearrival 1, prearrival 2, unloading, lairage 1, and lairage 2) and in Exp. 2 (rest, pretravel 1, pretravel 2, travel, prearrival 1, prearrival 2, lairage 1, and lairage 2). A delta GTT (ΔGTT) was calculated as the difference between the measured GTT at any determined event and the GTT measured at rest. In Exp. 1, the ΔGTT of pigs was greater ( < 0.001) in summer than in winter and only during the pretravel and initial travel periods. No difference was observed in the ΔGTT between the 2 truck types ( > 0.10). In summer, pigs located in the front top and rear top compartments of the PB trailer presented greater ( < 0.05) ΔGTT values than those transported in the middle top and front belly compartments during initial travel. In summer, during prearrival 1 and 2, a greater ( < 0.05) loss of GTT was found in pigs located in the rear top compartment of the DD truck compared with the rear lower compartment and in the front middle compartment compared with the rear middle compartment of the PB trailer. In Exp. 2, the ΔGTT of pigs was greater ( = 0.03) in summer than in winter during pretravel 2. Pigs in the front top compartment had a greater ( < 0.05) ΔGTT compared with pigs in the middle top, lower deck, and front belly compartments during the pretravel periods. Based on the results of the 2 experiments, modifications of the PB trailer model are recommended to limit body temperature increase due to physical stress at loading and unloading, and during transport due to inconsistent ventilation rate across vehicle locations.

Changes in serum cortisol reveal functional differences in frustration-induced chain chewing in pigs.

The pituitary-adrenal correlates of oral stereotypes in pigs were studied in two frustration situations of intermittent food distribution in which small amounts of food were given every 4 min (n = 4), and a massed food situation in which the same total amount of food was given in one meal at the beginning of the session (n = 5). Control animals (n = 6) were exposed to intermittent food but without a chain. Both intermittent-food and massed-food pigs developed chain chewing at similarly high rates. Blood samples were taken on days 8 and 21 of the experiment. Serum cortisol decreased between the beginning and the end of session 21 in intermittent-food pigs, but increased in pigs subjected to the massed-food condition. These findings suggest that oral stereotypies elicited by an intermittent schedule of food presentation are not equivalent to those elicited by the massed-food regimen.

Behavioral methods to answer questions about sheep.

Animal behavior has been defined as the interaction of an animal with its environment. During this interaction the animal must make decisions, based on its evaluation of the environment and its needs, of whether or not the environment is adequate or appropriate for specific behaviors. The environment includes both physical and biotic components, so sheep adjust their behavior in response to such diverse characteristics as the thermal conditions of their environment, the flora present, or the characteristics of other sheep. Although an animal's subjective experiences may not lend themselves to direct evaluation, we may be able to address these questions indirectly by using behavior as an indicator of the animal's decisions. This paper reviews research on the use of space, maternal and neonatal recognition, sexual behavior, and aversiveness. The majority of methods involve preference or acceptance tests. Assumptions, which often affect how tests are conducted and results interpreted, should be made only after the alternatives are carefully considered.

Why the study of animal behavior is associated with the animal welfare issue.

Of the various disciplines within the animal sciences, the issue of animal welfare has been most closely associated with ethology, the study of animal behavior. Prior to the modern welfare movement, applied ethology was primarily involved in studies on feeding and reproductive behavior. The emphasis on freedom of movement and mental experiences in animal welfare resulted in the field of applied ethology developing its current welfare interests. During the past 30 yr, applied ethology has been used to gather appropriate information to develop alternate management systems that accommodate normal behavior. The issue of behavioral needs has been addressed and research interest in motivation has developed. Preference tests have been used for their traditional role of improving comfort and have been modified to assess motivation as well. We have used abnormal behaviors as indicators of poor welfare and are shifting our emphasis to causative factors of these behaviors. The emotional states and cognitive abilities of animals have been studied but will become an increasingly important component of behavior research into animal welfare in the future.

Assessment of comfort and well-being in farm animals.

The assessment of comfort and well-being in farm animals is discussed in terms of physical damage, physiological responses and behavior. Injuries may be due to the physical environment or contact, such as aggression, with other animals. Animals may reduce the frequency of injuries by modifying their behavior. Evaluation of injuries requires a methodical assessment of specific areas of the body and examination of the facilities and behavior of the animal to determine cause. The physiological response of an animal is dependent upon its psychological response. The adrenal medullary and cortical responses represent distinct strategies that may occur simultaneously or independently of each other. Stress frequently results in suppression of immune responses, although some aspects of the immune system are enhanced. Inadequate or excessive motivation results in behavioral problems and facilities must accommodate the behavior of the animals. Methods of preference-testing have been improved to evaluate factors in the environment and assess motivation for specific behaviors more reliably. All of the methods used to assess comfort and well-being must consider the animal's ability to adapt to different environments. Although it remains difficult to assess comfort and well-being across systems, improvement within a system can be demonstrated.

Use of lambing cubicles and the behavior of ewes at parturition.

Three trials were conducted involving 393 ewes to determine the feasibility of using cubicles to provide isolation for parturient ewes in lambing pens. The cubicles consisted of an enclosure with 1 m high walls and a small (.6 m wide) opening to allow ewes free access. In trial 1, 42% of the parturitions occurred in the cubicles, which occupied only 19% of the pen area. No preference was noted for large (1.8 x 1.8 m) vs small (1.8 x 1.2 m) cubicles. Use of the cubicles increased from 4% of the time 24 h before parturition to 25% of the time during the 6 h immediately preceding parturition. In trial 2, ewes did not show a preference for open vs covered walls on cubicles or for open vs covered cubicle ceilings. Cubicles were again used to a greater (P less than .01) extent than would be predicted by their relative area (26% use, 18% area). In the final trial, mature ewes used cubicles to a greater (P less than .10) extent than did yearlings (55 vs 38%, respectively). Cubicles and areas of the pen farthest from the working area of the herdsman were most frequently (P less than .001) used during parturition. Cubicles appeared to be effective in preventing separation of newborn lambs from their dam and in reducing interference by other ewes.

Diurnal behavior patterns of feedlot bulls during winter and spring in northern latitudes.

The diurnal behavior patterns of feedlot bulls were investigated at 52 degrees N during winter and spring. Two trials were conducted during periods when the daylight portion of the day increased by over 7 h. In trial 1, 324 bulls were observed hourly for 24 h on nine occasions at 2-wk intervals. The average proportions of bulls eating, drinking, standing and lying were 9.8, 1.9, 27.4 and 60.0%, respectively. Major periods of eating, drinking and standing were associated with the times of sunrise and sunset and shifted with seasonal changes. Initiation and termination of the afternoon period of eating was greatly affected by changing times of sunset and not by the daily addition of feed, which always occurred at approximately 1600 h. A significant period of eating, involving up to 15% of the bulls at one time, occurred near midnight during the longer winter night but decreased in duration and intensity as day-length increased. In trial 2, continuous observations for 24 h were made at 2-wk intervals on two groups of nine bulls. When the spread in time between morning and evening activity increased due to longer daylength, bulls were active at midday. This became more pronounced on days when the photoperiod exceeded 10 h. Minor periods of activity were evident at night. Mounting and agonistic encounters increased dramatically in frequency near sunset and in general were associated with the major periods of eating and standing.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of auditory, visual and chemical stimuli on the ingestive behavior of newly weaned piglets.

Auditory, chemical and visual stimuli were used in a factorial trial in an attempt to stimulate feeding in newly weaned piglets. Ninety-six crossbred piglets weaned at 28 d of age were assigned to groups containing four littermates. Each group was placed in a 1.2-m X 1.2-m pen in an isolated room for 48 h. Pens were equipped with nipple waterers and trough-type feeders. The auditory stimulus was piglet and sow nursing vocalizations. A visual stimulus was provided by a lamp that illuminated the feeding area. Auditory and visual stimuli were presented for 5 min once an hour for 48 h. The chemical stimulus consisted of 60 ml of evaporated milk sprayed over the surface of the feed once every 12 h. Water was used in place of milk in control treatments. Piglets were videotaped for 48 h. Frequency and duration of feeding, drinking and lying were recorded for two piglets out of each pen. Auditory stimuli increased (P less than .05) the number of drinking bouts per day from 16.3 to 19.2 and the number of drinking bouts associated with stimulus presentation from 6.2 to 8.0. There also was an auditory X day interaction effect on total time spent feeding. On d 2 postweaning piglets in the auditory treatment group spent more (P less than .05) time feeding than did those without auditory stimulation (127.1 vs 104.2 min, respectively). The relatively simple visual and chemical stimuli tested had no significant effects on ingestive behavior.(ABSTRACT TRUNCATED AT 250 WORDS)

Use of birth fluids and cervical stimulation in lamb fostering.

Jackets soaked in birth fluids (BF) and cervical stimulation (CS) were used in a 2 X 2 factorial arrangement of treatments to determine their usefulness in fostering lambs. Subjects were 39, 3-d-old to 14-d-old lambs to be adopted by 39, 2-d to 7-d postpartum ewes rearing their own single lambs. Birth fluids were collected by drying newborn lambs with cloth jackets. Jackets were frozen for storage and were later thawed and placed on experimental alien lambs. Cervical stimulation was applied by attempting to insert a hand into the cervix of the ewe for 5 min immediately before presentation of an alien lamb. Maternal behavior tests, in both the absence and presence of the ewe's own lamb, were conducted twice daily in a small pen for 2.5 d. On d 3 and 4, lambs were tested in a large pen with three to four other ewes and their lambs. Aggression toward the alien lamb was greater during the first exposure in all treatments. Avoidance and nosing behaviors toward aliens were significantly less, and alien lambs were able to suckle more, when the ewe's own lamb was also present. Lambs receiving BF suckled more and were accepted more often. Cervical stimulation, in the absence of BF, improved acceptance compared with controls. The proportion of ewes accepting alien lambs were 100, 80, 60 and 10% for BF, BF-CS, CS and control treatments, respectively. Alien lambs that were accepted had similar growth rates to weaning as the ewe's own lamb. We conclude that fostering is facilitated by use of jackets soaked in BF and by CS.

Effects of zeranol implantation and late castration on sexual, agonistic and handling behavior in male feedlot cattle.

Seventy-two Angus feedlot bulls were observed to determine the effects of implanting with zeranol (0, 36 or 72 mg; four groups of six/level) at 8 mo of age (d 0), and of castration midway through the feedlot period (d 115) vs remaining intact (six groups/treatment) on sexual, agonistic and handling behaviors. All 36-mg-treated cattle were re-implanted (36 mg) on d 112; 72-mg-treated cattle were not re-implanted. Each group was observed for a total of 8 h at the time of sunset +/- 30 min for sexual and agonistic behaviors during the trial. Observations on handling were made during 15 weighings and on seven occasions in the pens of the animals. Zeranol did not affect sexual or agonistic behavior. Before imposition of castration, implanted bulls entered the scales more quickly, took longer to stand still on the scales and were less quiet than non-implanted bulls (P less than .05). Castration decreased the sexual behaviors of masturbation (.75 vs .08 X pen-1 X h-1; P less than .05), attempted mounts (.75 vs .33 X pen-1 X h-1; P less than .05) and chinning (10.70 vs 4.75 X pen-1 X pen-1; P less than .10) and the agonistic behavior of butting (42.42 vs 31.50 X pen-1 X h-1; P less than .01) in contrast to intact bulls. Castrated animals entered (P less than .10) and exited (P less than .05) the scales more quickly than did intact males.(ABSTRACT TRUNCATED AT 250 WORDS)

Attraction of newborn piglets to auditory, visual, olfactory and tactile stimuli.

Newborn piglets were removed from their dam and their responses to a variety of sensory stimuli were tested in four experiments. Test stimuli were presented simultaneously in multiple-choice arenas. Piglets allowed to choose among recordings of sow vocalizations, piglet vocalizations or white noise in a 5-min test spent more time in proximity to vocalizations of sows and piglets than near white noise. This was significant for males (P less than .01) but not for females. Piglets choosing among illumination levels (bright, dim or dark) in a 5-min test showed a strong preference for either dim or dark areas over bright light (P less than .01), with no difference between attractivity of dim and dark areas. Piglets choosing among birth fluids, sow's milk or tap water during a 5-min test spent more time with maternal odors than with water (P less than .05). No difference in attractivity between birth fluids and sow's milk was apparent. Preferences of piglets to move either with or against the direction of hair growth were tested using the mid-back area of the sow as a test surface. Piglets moved with the direction of hair growth twice as often as against the growth of hair (P less than .01). Results of these experiments indicate that piglets can discriminate among auditory, olfactory, visual and tactile stimuli immediately after birth.

Effects of eating space and availability of water in feeders on productivity and eating behavior of grower/finisher pigs.

Three experiments were conducted to determine the effects of eating space and availability of water within feeders on the productivity and behavior of growing/finishing pigs. In Exp. 1, 12 commercial feeders were classified as being either single-space (SS) or multiple-space (MS), and either as dry (D) or wet/dry (WD), resulting in two SS-D, four MS-D, three SS-WD and three MS-WD models. Each model was evaluated using four pens of 12 pigs, which were fed a mash diet throughout the growing/finishing period (25 to 106 kg). Pigs were videotaped when they were approximately 40 and 80 kg in weight to determine eating behavior. The number of feeding spaces did not affect the productivity of the pigs, but the presence of water within the feeder resulted in increases in ADFI (P < .05) and ADG (P < .05) and a reduction in carcass lean (P < .05). Pigs eating from SS feeders spent 15% less time eating than those fed from two-space feeders (P < .05), and occupancy rate for feeding spaces was increased by 75% (P < .05). The WD feeders also resulted in a reduction (17%) in eatingtime compared to D models (P < .01), and occupancy rate for WD feeders was similarly reduced (P < .05). Pigs spent 16% less time eating when they weighed approximately 80 kg than when they weighed 40 kg (P < .01). In Exp. 2, rate of eating was determined during a short test on the same 12 feeder models for both small (48 kg) and large (90 kg) pigs. Large pigs ate faster than small pigs, but eating rate was not affected by feeding space or presence of water in the feeder. In Exp. 3, eating rate was determined for small amounts of dry or wet feed. Premixing water with the feed (1:1 ratio by weight) increased eating speed (P < .01). We concluded that 12 pigs can be fed from a single-space feeder without affecting productivity. The inclusion of water within a feeder decreases time spent eating, but it increases ADFI and ADG. When pigs are small, they spend more time eating, and feeder occupancy rates are higher than when they are large.

The effects of regrouping on behavioral and production parameters in finishing swine.

Three trials involving 396 pigs were conducted to determine the effects of regrouping finishing swine (83.8 +/- .69 kg) on weight gain and behavior during the subsequent 2-wk period. The methodology between Trials 1, 2, and 3 differed primarily in the total number of pigs tested (72, 144, and 180, respectively) and the number of pigs per pen (3, 3 or 5, and 5, respectively). In all trials, like-sexed pigs were moved into a new pen location and allotted to one of three treatments: 1) a group of familiar pen mates (Control), 2) a group composed of unfamiliar pigs (Mixed), and 3) pigs mixed with strangers for 24 h and then reunited with original pen mates for the duration of the trial (Mixed 24 h). In the pooled analysis, control pigs gained faster (P < .01) than Mixed pigs (.87 and .77 kg/d, respectively) over the 2-wk period. Mixed 24-h pigs were intermediate in gain (.80 kg/d), indicating that the most severe aggression normally observed during the first 24 h accounts for only a portion of the setback. Apparently the negative social stress associated with being in the presence of unfamiliar pigs persisted beyond the first 24 h and was sufficient to limit weight gain over the 2-wk period. Time spent fighting was reduced from 1.72 min/h during a 6-h period on d 1 to .39 min/h during a 3-h period by d 2 in the Mixed group. Fighting was still observed in the Mixed pens 8 d after regrouping (.23 min/h), indicative of ongoing social conflicts.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of floor area allowance and group size on the productivity of growing/finishing pigs.

Six group sizes and three levels of floor area allowance were studied in a 6 x 3 factorial arrangement. Group sizes were 3, 5, 6, 7, 10, and 15 pigs per pen. Floor area allowances were .030, .039, and .048 m2 x BW(.667). All pens were square and equipped with a single space feeder and nipple drinker near one corner. Pigs were fed a pelleted diet. Initial weights averaged 25.0 kg, and pigs remained on test for 12 wk. Pigs were weighed, feed intake was determined, and size of pens was increased at 2-wk intervals. Pen size was adjusted to provide the space required for the midpoint of each weigh period. Two replicates of the study were conducted. The ADG was reduced with increasing group size (899, 851, 868, 872, 857, and 821 g, SEM = 16.4, for 3, 5, 6, 7, 10, and 15 pigs, respectively; P < .05), but the CV for gain (mean = .185) did not differ among group sizes. The ADFI also decreased with increasing group size (2.49, 2.34, 2.32, 2.28, 2.28, and 2.21 kg, SEM = .036, for 3, 5, 6, 7, 10, and 15 pigs, respectively; P < .05). Feed efficiency (gain/intake) was highest for group sizes of 7 and 10 pigs (.381) and lowest for pens of three and five pigs (.363; P < .05). The ADG and ADFI (832 g and 2.25 kg, respectively) for the most crowded space allowance were reduced compared to more spacious allowances (ADG and ADFI of 875 and 877 g, and 2.35 and 2.36 kg, for .039 and .048 m2 x BW(.667), respectively; P < .05). Efficiency did not differ among space allowances. These results confirm previous studies reporting a negative effect of increasing group size on productivity, but our study suggests that gain and intake reach a plateau at less space allowance than previously reported.

Effect of creep partitions on teat-seeking behavior of newborn piglets.

In the first of two studies on teat-seeking behavior of newborn pigs, latencies from birth to first mammary contact (LMC) and to first suckle (LS) were recorded by live observation (n = 66). LMC accounted for 66% of LS and variances were similar between these two measures, suggesting that LMC is a good predictor of time to first suckle. In a second experiment, 32 litters of pigs were farrowed in crates equipped with either solid, vertically slatted, horizontally slatted or diamond mesh creep partitions. Piglet behavior following parturition was recorded via time-lapse videotape. LMC was determined for each piglet and movements were plotted for four focal pigs/litter. Partition type did not affect LMC (mean = 34 min). LMC was significantly affected by number of littermates present during teat-seeking (P less than .001), birth order (P less than .001) and frequency of position changes by the sow (r = .26, P less than .01). Neither sex nor birth weight affected LMC on a within-litter basis, but across litters smaller pigs had greater contact latencies (r = -.38, P less than .001). Partition type did not affect distance traveled or time spent in contact with the sow, in contact with the creep partitions,, free standing or the total of these. LMC was positively correlated (P less than .05) with contact time with the sow (r = .34) and time behind the sow's back (r = .38) and negatively correlated with time spent free standing (r = -.35, P less than .05) and in contact with the sow's rear legs (r = -.29; P less than .10).

Effects of double decking and space allowance on the performance and behavior of feeder lambs.

A 2 X 2 factorial experiment was conducted using growing lambs to compare single-level vs double-decked pens and high (.32 m2/lamb) vs low (.48 m2/lamb) densities. Three replicates of each treatment combination were involved using 30 lambs/pen. In the double-decked pens, an upper deck located over the rear section of the lower level provided one-third of the total floor area. Feed and water were provided on the lower level only and lambs could move freely between levels by means of a slatted ramp. All floors were of expanded metal. Use of the various areas of the pens was determined during a 24-h observation and by a videotape recording of the double-decked pens during the daylight hours. Fleece contamination was determined by visual observation and standard wool testing procedures. Gain was determined over the 8-wk period of each replicate. The high density treatment resulted in 1.5 kg/lamb (10%) less gain (P less than .01) and, in the case of double-decked pens, different patterns of space utilization compared with the low density treatment. Lambs in the low density pens were able to move more successfully from resting areas to the feeding area in the afternoon (P less than .01). The double-decked system did not significantly affect weight gain, but resulted in dirtier fleeces (P less than .01).(ABSTRACT TRUNCATED AT 250 WORDS)

Wood chewing by stabled horses: diurnal pattern and effects of exercise.

Nine yearling horses, stabled in individual stalls, were used in a trial to determine the diurnal pattern of wood chewing and the effects of exercise on this behavior. The trial was a Latin square design conducted over three 2-wk periods during which each horse was exposed to each of the three following treatments: 1) no exercise (NE), 2) exercise after the morning feeding (AM), and 3) exercise in the afternoon (PM). Horses were fed a complete pelleted feed in the morning and both pelleted feed and long-stemmed hay in the afternoon. Exercise consisted of 45 min on a mechanical walker followed by 45 min in a paddock with bare soil. Each stall was equipped with two untreated spruce boards during each period for wood chewing. Wood chewing was evaluated by videotaping each horse for 22 h during each period, determining the weight and volume of the boards before and after each period, and by visual appraisal of the boards. Intake of trace mineralized salt was also measured. Wood chewing occurred primarily between 2200 and 1200. All measures of wood chewing were correlated when totals for the entire 6 wk were analyzed. When analysis was performed on 2-wk values, videotape results were not correlated with volume or weight loss of boards. Horses chewed more when on the NE treatment (511 s/d) than when on AM or PM (57 and 136 s/d, respectively; P less than .05). Salt intake tended to be greater for NE than for the other treatments (P less than .10).(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of group size on performance of growing-finishing pigs.

Six hundred forty growing-finishing pigs (initial BW = 23.2 +/- 4.8 kg) were used in a 12-wk study (final BW = 95.5 +/- 10.2 kg) to quantify the effects of group size (10, 20, 40, and 80 pigs/pen) on performance, tail biting, and use of widely distributed feed resources. One single-space wet/dry feeder was provided for every 10 pigs, and floor allowance was 0.76 m2/pig in all treatment groups. Weight gain and feed intake were measured every 2 wk. At weighing, a tail-biting injury score was given to each pig. Blood samples were collected and analyzed for neutrophil:lymphocyte ratio before regrouping at the beginning of the experiment, 24 to 48 h after regrouping, and on the last day of each trial. The use of feeders by individual pigs was assessed by behavioral observations. Average daily gain for the entire 12-wk trial did not differ among group sizes (861, 873, 854, and 845 g/d for groups of 10, 20, 40, and 80, respectively; P > 0.10). During the first 2 wk, ADG was lower for pigs in groups of 40 (554 g/d) than pigs in groups of 10 (632 g/d; P < 0.05), but not pigs in groups of 20 or 80 (602 and 605 g/d, respectively). Average daily feed intake, feed efficiency, and variability in final BW within a pen also did not differ among group sizes. Tail-biting injury scores increased throughout the study, but did not differ among group sizes. Similar proportions of pigs were removed from the trial for health reasons, primarily due to tail biting, in all treatments. Individual pigs in each group size ate from most, if not all, of the feeders in the pen. There was no evidence of spatial subgrouping within the larger groups. The results suggest that housing growing-finishing pigs in groups of up to 80 pigs is not detrimental to productivity and health if space allowance is adequate and feed resources are evenly distributed.

Effect of excess levels of methionine, tryptophan, arginine, lysine or threonine on growth and dietary choice in the pig.

Six experiments were conducted with newly weaned pigs (8 kg) to evaluate the effects of 4% excesses of DL-methionine, L-tryptophan, L-threonine, L-lysine or L-arginine on growth or "choice" (i.e., self-selection) when added to 20% protein, corn-soybean meal (C-SBM) diets. Arginine was supplied as the free base and lysine as lysine acetate to avoid acid-base problems. In the growth study, gain was reduced 52, 31, 28, 16 and 5% by additions of methionine, arginine, tryptophan, lysine and threonine, respectively. Small decreases in gain/feed occurred in pigs fed diets with excess methionine or lysine. Feed intake depressions were evident in pigs fed excess methionine or excess tryptophan within 1 d after initiation of the growth trial. Self-selection studies revealed that pigs strongly preferred the control diet over any of the diets containing excess amino acids. Further studies indicated that pigs preferred diets with excess threonine, lysine or arginine over those containing an equal excess (i.e., 4%) of methionine or tryptophan. Moreover, there was a tendency for pigs to prefer the diet with excess threonine over the one containing excess lysine or arginine. Also, pigs clearly preferred the diet with excess methionine over the diet containing excess tryptophan. When given a choice between a protein-free diet and a C-SBM diet containing 4% excess tryptophan, pigs initially (d 0 to 4) preferred the protein-free diet, but later adapted to the extent that during the last 4 d of the 12-d trial they consumed more of the tryptophan-imbalanced diet than of the protein-free diet.

Artificial pigs in space: using artificial intelligence and artificial life techniques to design animal housing.

Computer simulations have been used by us since the early 1970s to gain an understanding of the spacing and movement patterns of confined animals. The work has progressed from the early stages, in which we used randomly positioned points, to current investigations of animats (computer-simulated animals), which show low levels of learning via artificial neural networks. We have determined that 1) pens of equal floor area but of different shape result in different spatial and movement patterns for randomly positioned and moving animats; 2) when group size increases under constant density, freedom of movement approaches an asymptote at approximately six animats; 3) matching the number of animats with the number of corners results in optimal freedom of movement for small groups of animats; and 4) perimeter positioning occurs in groups of animats that maximize their distance to first- and second-nearest neighbors. Recently, we developed animats that move, compete for social dominance, and are motivated to obtain resources (food, resting sites, etc.). We are currently developing an animat that learns its behavior from the spatial and movement data collected on live pigs. The animat model is then used to pretest pen designs, followed by new pig spatial data fed into the animat model, resulting in a new pen design to be tested, and the steps are repeated. We believe that methodologies from artificial-life and artificial intelligence can contribute to the understanding of basic animal behavior principles, as well as to the solving of problems in production agriculture in areas such as animal housing design.