The effect of three space allowances on the physiology and behavior of weaned pigs during transportation

Stocking density is an important aspect of transport, which could affect animal health and welfare, especially in pigs simultaneously experiencing weaning stress. The objective of this research was to evaluate the effect of three different space allowances on the physiology and behavior of weaned pigs during transport. A commercial semi-trailer with compartments that provided 0.05, 0.06 and 0.07 m²/pig was used throughout the study. All three space allowances were represented on both the upper and lower decks during each replicate. A constant of 100 pigs were loaded into each experimental compartment. Pigs were then transported for 112.5 ± 6.5 min to the wean-to-finishing site using the same route for each replication. This experiment was replicated 4 times. The experimental unit was the compartment. Prior to and after transport, blood samples were taken from a sub-set of pigs (n = 32 pigs/space allowance) for analysis of physiological and immune measures, and body weights and lesion scores were also recorded. Data loggers were fitted inside the trailer to record temperature, humidity, and wind speed. Cameras were placed in each experimental compartment to record behavior and postures of pigs during transport. The frequencies of standing, lying, sitting, standing-rearing on another pig, lying/huddling on top of another pig, total active and total inactive behaviors were recorded using 1-min scan samples during the entire duration of transport. Inside trailer temperature ranged from − 2.4 to 21.7 °C and inside trailer relative humidity ranged from 28.4 to 89.2% during transport. Cortisol, the neutrophil:lymphocyte (N:L) ratio, blood urea nitrogen, total bilirubin, total protein, albumin, aspartate aminotransferase, and creatine kinase were higher (p < 0.05) in pigs after transport regardless of space allowance. Skin lesions were more severe (p < 0.001) in pigs after transport regardless of space allowance. Pigs spent more (p < 0.001) time active during the first 75 min of transport compared with the last 30 min, regardless of space allowance. Pigs spent less (p < 0.01) time standing on another pig during transport at 0.07 m²/pig compared with pigs transported at 0.06 m²/pig. Higher cortisol concentrations and N:L ratio in weaned pigs after transport suggest that these pigs experienced stress, however space allowance did not appear to influence this response. Space allowances of 0.05, 0.06 or 0.07 m²/pig did not differentially influence pig well-being during a 112-min transport period as measured by changes in physiological measures.     

Effects of distance moved during loading and floor space on the trailer during transport on losses of market weight pigs on arrival at the packing plant

Effects of distance moved during loading and floor space on the trailer during transport on the incidence of transport losses (dead and nonambulatory pigs) on arrival at the packing plant were evaluated in a study involving 42 loads of pigs (average BW = 131.2 kg, SD 5.05). A split-plot design was used with a 2 x 6 factorial arrangement of the following treatments: 1) distance moved from the pen to the exit of the building [short (0 to 30.5 m) vs. long (61.0 to 91.4 m)] and 2) transport floor space (0.396, 0.415, 0.437, 0.462, 0.489, or 0.520 m(2)/pig). Loading distance treatments (sub-plots) were compared within transport floor space treatments (main plot). Pigs were loaded at the farm using sorting boards and, if necessary, electric goads, transported approximately 3 h to a commercial packing plant and unloaded using livestock paddles. The number of nonambulatory pigs during loading and the number of dead and nonambulatory pigs at the plant were recorded. Nonambulatory pigs were classified as fatigued, injured, or injured and fatigued. In addition, the incidence of pigs exhibiting signs of stress (open-mouth breathing, skin discoloration, and muscle tremors) during loading and unloading was recorded. There were no interactions (P > 0.05) between distance moved and transport floor space treatments. Moving pigs long compared with short distances during loading increased (P < 0.001) the incidence of open-mouth breathing after loading (24.9 vs. 11.0 +/- 1.03%, respectively) and tended to increase the incidence of nonambulatory pigs during loading (0.32 vs. 0.08 +/- 0.09%, respectively; P = 0.09) and of nonambulatory, injured pigs at the plant (0.24 vs. 0.04 +/- 0.07%, respectively; P = 0.06). However, distance moved did not affect other losses at the plant. Total losses at the plant were greater (P < 0.05) for the 3 lowest floor spaces compared with the 2 highest floor spaces, and pigs provided 0.462 m(2)/pig during transport had similar transport losses to those provided 0.489 and 0.520 m(2)/pig (total losses at the plant = 2.84, 1.88, 1.87, 0.98, 0.13, and 0.98 +/- 0.43% of pigs transported, for 0.396, 0.415, 0.437, 0.462, 0.489, and 0.520 m(2)/pig, respectively). These data confirm previous findings that transport floor space has a major effect on transport losses and suggest that these losses are minimized at a floor space of 0.462 m(2)/pig or greater.     

Effects of multiple concurrent stressors on rectal temperature, blood acid-base status, and longissimus muscle glycolytic potential in market-weight pigs

Sixty-four market-weight (130.0 +/- 0.65 kg) barrows (n = 16) and gilts (n = 48) were used in a split-plot design with a 2 x 2 x 2 factorial arrangement of treatments: 1) handling intensity (gentle vs. aggressive), 2) transport floor space (0.39 vs. 0.49 m(2)/pig), and 3) distance moved during handling (25 vs. 125 m) to determine the effects of multiple concurrent stressors on metabolic responses. For the handling intensity treatment, pigs were moved individually approximately 50 m through a handling course with either 0 (gentle) or 8 (aggressive) shocks from an electric goad. Pigs were loaded onto a trailer and transported for approximately 1 h at floor spaces of either 0.39 or 0.49 m(2)/pig. After transport, pigs were unloaded, and the distance moved treatment was applied; pigs were moved 25 or 125 m through a handling course using livestock paddles. Rectal temperature was measured, and blood samples (to measure blood acid-base status) were collected 2 h before the handling intensity treatment was applied and immediately after the distance moved treatment was applied. A LM sample to measure glycolytic potential was collected after the distance moved treatments on a subset of 32 pigs. There were handling intensity x distance moved interactions (P < 0.05) for several blood acid-base measurements. In general, there was no effect of distance moved on these traits when pigs were previously handled gently. However, when pigs were previously handled aggressively, pigs moved 125 compared with 25 m had greater (P < 0.05) blood lactate and less (P < 0.05) blood pH, bicarbonate, and base-excess. Pigs transported at 0.39 compared with 0.49 m(2)/pig had a greater (P < 0.01) increase in creatine kinase values; however, transport floor space did not affect any other measurements. Data were analyzed by the number of stressors (the aggressive handling, restricted transport floor space, and 125-m distance moved treatments) experienced by each pig (0, 1, 2, or 3). As the number of stressors experienced by the pig increased, rectal temperature, blood lactate, and LM lactate increased linearly (P 相似文献   

Effects of season and distance moved during loading on transport losses of market-weight pigs in two commercially available types of trailer

This study evaluated effects of trailer design and season on physical indicators of stress during loading and unloading and transport losses (dead and nonambulatory pigs) in market-weight pigs (BW = 129.6 +/- 0.40 kg). A total of 109 trailer loads of pigs (n = 17,256 pigs) from 1 farm were used in a randomized complete block design with a 2 x 4 factorial arrangement of treatments: 1) trailer design (potbelly vs. straight-deck) and 2) season (spring vs. summer vs. fall vs. winter). A subset of loads (n = 42) was used to examine effect of distance pigs were moved during loading [short (<24 m) vs. long (47 to 67 m)] on physical indicators of stress and transport losses. This study was conducted on 7 d per season at 1 farm with 4 loads (2 on potbelly and 2 on straight-deck trailers) being transported each day to 1 commercial packing plant. Pigs from different farm groups were mixed on the trailer and provided with 0.45 m(2)/pig floor space during an approximately 4-h journey to the plant. The percentage of pigs exhibiting open-mouth breathing, skin discoloration, and muscle tremors was recorded during loading and unloading. Additionally, dead pigs on arrival at the plant and nonambulatory pigs at the farm and at the plant were recorded. Effects of trailer design on open-mouth breathing and skin discoloration during unloading were dependent on season (trailer design x season interaction; P < 0.05). Pigs unloaded from potbelly trailers had a greater (P < or = 0.05) incidence of open-mouth breathing in the spring and summer and a greater (P < 0.05) incidence of skin discoloration in the spring, summer, and winter than pigs unloaded from straight-deck trailers. The incidence of total nonambulatory pigs at the plant was greater (P < 0.05) in the winter than in the spring and summer. The long compared with short distance moved treatment resulted in a greater (P = 0.001) incidence of open-mouth breathing and skin discoloration during loading and tended (P = 0.06) to increase the incidence of nonambulatory pigs at the farm. However, there was no effect of trailer design, season, or loading distance on total losses at the plant. In summary, physical indicators of stress (open-mouth breathing and skin discoloration) were increased with the long distance moved during loading treatment and were greater during unloading for potbelly than straight-deck trailers; however, trailer design, season, and loading distance had minimal effects on total transport losses.     

Effect of floor space during transport of market-weight pigs on the incidence of transport losses at the packing plant and the relationships between transport conditions and losses

Data on 74 trailer loads of finishing pigs (mean BW = 129.0, SEM = 0.63 kg) from wean-to-finish buildings on 2 farms within 1 production system were collected to investigate the effect of amount of floor space on the trailer (0.39 or 0.48 m2/pig) during transport on the incidence of losses (dead and nonambulatory pigs) at the packing plant and to study the relationships between transport conditions and losses. Pigs were loaded using standard commercial procedures for pig handling and transportation. Two designs of flat-deck trailers with 2 decks were used. Floor space treatments were compared in 2 similarly sized compartments on each deck of each trailer type. Differences in floor space were created by varying the number of pigs in each compartment. The incidence of nonambulatory pigs at the farm during loading and at the plant after unloading, average load weight, load number within each day, event times, and temperature and relative humidity in the trailer from loading to unloading were recorded. Of the 12,511 pigs transported, 0.26% were non-ambulatory at the farm, 0.23% were dead on arrival, and 0.85% were nonambulatory at the plant. Increasing transport floor space from 0.39 to 0.48 m2/pig reduced the percentage of total nonambulatory pigs (0.62 vs. 0.27 +/- 0.13%, respectively; P < 0.05), nonambulatory, noninjured pigs (0.52 vs. 0.15 +/- 0.11%, respectively; P < 0.01), and total losses (dead and nonambulatory pigs) at the plant (0.88 vs. 0.36 +/- 0.16%, respectively; P < 0.05) and tended to reduce dead pigs (0.27 vs. 0.08 +/- 0.08%, respectively; P = 0.06). However, transport floor space did not affect the percentage of nonambulatory, injured pigs at the plant. Nonambulatory pigs at the farm were positively correlated with relative humidity during loading and load number within the day (r = 0.46 and 0.25, respectively; P < 0.05). The percentage of total losses at the plant was positively correlated to waiting time at the plant, unloading time, and total time from loading to unloading (r = 0.24, 0.51, and 0.36, respectively; P < 0.05). Average temperature during loading, waiting at the farm, transport, waiting at the plant, unloading, and average pig weight on the trailer were not correlated to losses. These results suggest that floor space per pig on the trailer and transport conditions can affect transport losses.     

Feeder location did not affect performance of weanling pigs in large groups

Crossbred pigs weaned at 17 d of age (n = 1,760; mean initial BW = 5.6 +/- 0.7 kg) were used in two 4-wk trials (four replicates per trial) to evaluate the effects of three pen designs on pig performance. The designs were 1) large group size (100 pigs/pen) with five two-sided feeders in a single, central location in the pen; 2) large group size (100 pigs/pen) with five two-sided feeders in multiple (five) locations in the pen; and 3) small group size (20 pigs/pen) with a single two-sided feeder in a central location in the pen. Each feeder provided two 20.3-cm-wide feeding places on each side. Pigs had free access to feed and water. Feeder-trough space (4 cm/pig) and floor-area allowance (0.17 m2/pig) were the same for all treatments. Pigs in the large-group treatments were lighter (15.6 and 15.6 vs 16.0 kg; P < 0.01) at the end of wk 4 and had lower ADG (358 and 357 vs 373 g; P < 0.01) and ADFI (510 and 521 vs 544 g; P < 0.01) during wk 2 through 4 than pigs in small groups. Gain:feed ratio was similar (P > 0.05) for all treatment groups throughout the study. For large groups, feed disappearance from each of the five feeders was similar (P > 0.05) for both multiple- and single-location treatments. In summary, large group size reduced pig growth performance, but the approach to providing multiple feeding locations that was employed in this experiment did not increase feed intake or growth performance of pigs in the large groups.     

Effects of floor space during transport and journey time on indicators of stress and transport losses of market-weight pigs

The effects of floor space on the trailer and journey time during transport from the farm to the packing plant on indicators of stress (open-mouth breathing, muscle tremors, and skin discoloration) and on the incidence of transport losses (dead on arrival, nonambulatory, noninjured, and nonambulatory, injured) were evaluated in a study involving 160 loads of market-weight pigs (BW 124.7 ± 4.38 kg) using a split-plot design with a 2 × 6 factorial arrangement of treatments: 1) journey time [main plot; short (<1 h) and long (3 h)] and 2) floor space (subplot; 0.396, 0.415, 0.437, 0.462, 0.489, and 0.520 m(2)/pig, which is equivalent to 0.317, 0.332, 0.350, 0.370, 0.391, and 0.416 m(2)/100 kg of BW, respectively). Two consecutively loaded trailers were randomly allotted to journey time treatment. Floor space treatments were compared in the front 3 compartments on the top and bottom decks of the trailer and were created by varying the number of pigs per compartment, which confounds the effect of floor space with group size. Of the 17,652 pigs transported in 954 test compartments, 0.24% died or became nonambulatory. Neither journey time nor floor space had an effect (P > 0.05) on the incidence of dead and nonambulatory, injured pigs, or on total transport losses. There were interactions (P < 0.05) between journey time and floor space treatments for the incidences of nonambulatory, noninjured pigs and open-mouth breathing. For 2 of the smallest floor spaces (0.415 and 0.437 m(2)/pig), the incidence of nonambulatory, noninjured pigs was greater on short than on long journeys; for the other 4 floor spaces there was no effect (P > 0.05) of journey time. The incidence of open-mouth breathing for the 3 smallest floor spaces was greater (P < 0.05) for short than long journeys, whereas there was no effect (P > 0.05) of journey time for the 3 greatest floor spaces. The frequency of skin discoloration was greater (P < 0.001) for pigs transported at the 2 smallest floor spaces compared with the other 4 floor spaces. In summary, short journey time increased the frequency of indicators of stress after unloading at the plant for pigs transported at smaller floor spaces and also increased the incidence of nonambulatory, noninjured pigs at 2 of the 3 smallest floor spaces. However, neither transport floor space nor journey time had an effect on total losses.     

Relationship between estimated finishing-pig space allowance and in-transit loss in a retrospective survey of 3 packing plants in Ontario in 2003

The objective of this study was to determine the association between space allowance and in-transit loss of finishing pigs going to select abattoirs in Ontario during summer weather conditions. The study included data from 2- or 3-tiered trailers transporting ≥ 130 pigs in June, July, and August 2003 to 3 packers that processed 76% of Ontario market pigs. Daily in-transit loss data were merged with packer data to determine the number of pigs on each trailer. Space allowance (in square meters per pig) was estimated from the percentage of each trailer's capacity that was filled by the load size. Actual pig weights were not available. Hourly temperature and relative humidity were obtained from 2 local Ontario weather stations. In-transit loss increased with environmental temperature, by 6.6 times at temperatures between 28°C and 34.2°C compared with < 17°C. At space allowances between 0.44 and 0.43 m(2)/pig compared with ≥ 0.515 m(2)/pig, in-transit losses increased 2.12 times when environmental temperatures were < 21°C. Temperature is likely a more important determinant of in-transit loss than space allowance. However, in-transit losses in hot weather are likely to be reduced by increasing space allowance or by adding a cooling device.     

Impact of spontaneous exercise on performance,meat quality,and muscle fiber characteristics of growing/finishing pigs

The objective of this experiment was to determine if increased space and exercise for finisher pigs (0.90 vs 9.45 m2/pig) affects performance, meat quality, or muscle fiber characteristics. Newsham barrows (n = 32, 4 pens/treatment) were placed in one of two space allocations: control space allowance (CONT) or in a long pen with increased space allowance (10x). Pigs were weighed every 28 d and feed intake/pen was calculated. Pigs were filmed for behavioral analysis on d 70 and 100 using video recorders to determine walking distances over a 24-h period. After a 5-h transport and 2-h rest period, pigs (approximately 115 kg) were slaughtered on the same day at a commercial facility. Muscle samples were obtained from the longissimus lumborum (LL) and semimembranosus (SM) muscles within 1 h postmortem for muscle fiber typing. Backfat thickness and pH decline were measured on the left side of each carcass. After 24-h chilling, a boneless loin was collected from each pig and stored at 2 degrees C until analyzed. On d 14 postmortem, loins were cut at the 10th rib for color evaluations, and chops were cut for Warner-Bratzler shear (WBS) force and sensory analysis. Histochemical staining methods were used for the detection of type I, IIA, and IIB/X muscle fiber types. There were no significant differences (P > 0.10) in live weight, ADG, ADFI, or G:F ratio of the two experimental groups evaluated. Pigs finished in 10x pens walked a greater (P < 0.01) distance over a 24-h period than pigs finished in the CONT pens. Pigs finished in the lOx pens were fatter (P < 0.05) at the last lumbar vertebra than pigs finished in the CONT pens, but no significant differences were found in loineye area, loin color, marbling scores, WBS, sensory panel scores, retail display measures, or muscle fiber type percentages. Expanded space allowance to increase exercise resulted in no improvements in pig performance, pork loin measures, or muscle characteristics.     

Response of growing-finishing pigs to decreasing floor space allowance and(or) virginiamycin in diet

Five hundred forty crossbred pigs were utilized in four trials (10 replications) at two stations to determine the separate and interacting effects of decreasing floor space allowance with or without the addition of virginiamycin to the diet on performance of growing-finishing pigs. Pigs were allowed .37, .33 or .28 m2/pig during the growing phase (23 to 55 kg) and .74, .66, .56 m2/pig during the finishing phase (55 to 100 kg) and fed either a corn-soybean meal control diet or the control diet plus 11 mg of virginiamycin/kg of diet. Floor space allowances were achieved by varying pen size, so the number of pigs and feeder space per pig were constant for all pens. During the growing phase, daily gain (P less than .01) daily feed intake (P less than .05) and feed conversion ratio (P less than .05) decreased as floor space allowance decreased. During the finishing phase and for the total test period, daily gain (P less than .01) and feed conversion ratio (P less than .05) were reduced but daily feed intake was not affected (P greater than .05) by restricted floor space allowance. The addition of virginiamycin to the diet had no effect on pig performance. The virginiamycin X floor space allowance interaction was not significant, suggesting that pigs fed a diet with or without virginiamycin responded similarly to restricted floor space allowance. The data suggest that the addition of virginiamycin to the diet was ineffective in overcoming the decrease in performance of growing-finishing pigs caused by crowded conditions.     

Effect of restricted postweaning growth resulting from reduced floor and feeder-trough space on pig growth performance to slaughter weight in a wean-to-finish production system

The effect of reduced pig growth rate postweaning as a result of restricted floor space and feeder trough space on subsequent growth to slaughter was investigated in a wean-to-finish system. Crossbred pigs (n = 1,728) were used in a randomized block design with a 2 x 2 x 2 factorial arrangement of treatments: 1) floor space (high [0.630 m2/pig] vs. low floor space [0.315 m2/pig]), 2) feeder trough space (unrestricted [4 cm/pig] vs. restricted feeder trough space [2 cm/pig]), and 3) period of imposing floor- and feeder-trough-space treatments (12 vs. 14 wk postweaning). Growth performance was measured from weaning (5.5 +/- 0.01 kg of BW; 17 d of age) to slaughter (the end of wk 25 postweaning). From the end of the treatment period to the end of wk 25, pigs on all treatments had the same floor and feeder trough space. Pigs with low floor space had lower (P < 0.01) ADG, ADFI, and gain:feed ratio than those with high floor space, and were therefore lighter (P < 0.05) at the end of the postweaning treatment period. Pigs given the restricted feeder trough space had lower (P < 0.05) ADFI, similar (P > 0.05) ADG, and higher (P < 0.01) gain:feed ratio than those with unrestricted feeder trough space during the treatment period. Pigs in the 14-wk treatment period had higher (P < 0.01) ADG and ADFI, but lower gain:feed than those in the 12-wk treatment during that period. In the subsequent period, from the end of treatment to wk 25, there was an interaction (P < 0.05) between floor space and treatment period; the difference in ADG and gain:feed for pigs on low vs. high floor space was greater for the 14-wk than the 12-wk treatment period. However, low-floor-space pigs tended (P = 0.06) to be lighter than high-floor-space pigs at the end of wk 25 postweaning. Neither feeder trough space nor treatment period affected pig growth performance during the period from the end of treatment to wk 25. Carcass backfat and longissimus depths at the end of wk 25 were not influenced (P > 0.05) by treatment. In summary, pigs with restricted growth due to low floor space until either 12 or 14 wk postweaning had increased growth and feed efficiency in the subsequent period to wk 25 postweaning, with only a slight effect on BW and no effect on carcass measures.     

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 housing finishing pigs in two group sizes and at two floor space allocations on production, health, behavior, and physiological variables

With the current shift in the industry toward housing pigs in groups of 100 to 1,000 per pen have come questions as to whether pigs can perform as well in large groups as they do in small and whether large groups of pigs can use the space provided more efficiently. This study examined effects of small (18 pigs) vs. large (108 pigs) group sizes provided 0.52 m(2)/ pig (crowded) or 0.78 m(2)/pig (uncrowded) of space on production, health, behavior, and physiological variables. Eight 7-to 8-wk-long blocks, each involving 288 pigs, were completed. The average BW at the beginning of the study was 37.4 +/- 0.26 kg. Overall, ADG was 1.032 kg/d and 1.077 (+/-0.015) kg/d for crowded and uncrowded pigs, respectively (P = 0.018). Differences between the space allowance treatments were most evident during the final week of study. Overall G:F was also reduced (P = 0.002) in the crowded treatment. Pigs in the crowded groups spent less (P = 0.003) time eating over the 8-wk study than did pigs in noncrowded groups, but ADFI did not differ (P = 0.34) between treatments. Overall, ADG of large-group pigs was 1.035 kg/d, whereas small group pigs gained 1.073 kg/d (+/-0.015; P = 0.039). Average daily gain differences between the group sizes were most evident during the first 2 wk of the study. Over the entire study, G:F also differed, with large groups being less efficient (P = 0.005) than small groups. Although large-group pigs had poorer scores for lameness (P = 0.012) and leg scores (P = 0.02) throughout the 8-wk period, morbidity levels did not differ (P = 0.32) between the group sizes. Minimal changes in postural behavior and feeding patterns were noted in large groups. An interaction (P = 0.04) of group size and space allowance for lameness indicated that pigs housed in large groups at restricted space allowances were more susceptible to lameness. Although some behavioral variables, such as lying postures, suggest that pigs in large groups were able to use space more efficiently, overall productivity and health variables indicate that pigs in large and small groups were similarly affected by the crowding imposed in this study. Broken-line analysis of ADG indicated no difference in the response to crowding by pigs in large and small groups. Little support was found for reducing space allowances for pigs in large groups.     

Synthetic maternal pheromone stimulates feeding behavior and weight gain in weaned pigs

One hundred and forty-four pigs were used to determine the effects of a putative synthetic maternal pheromone on behavior and performance of weanling pigs. Each pen of weaned pigs contained three pigs that were given free access to water and feed. Pigs were videotaped in time lapse for 48 h after weaning and weekly body weights and feed disappearances were recorded for 4 wk. Treatments included: a) control (vehicle applied), b) 30 mL of synthetic pheromone applied to the feeder, or c) 10 mL of synthetic pheromone applied to each of three pigs' snouts. Pigs exposed to the synthetic pheromone spent more (P < 0.05) time with their heads in the feeder and less (P < 0.05) time drinking, lying down, or engaged in agonistic behaviors than control pigs. Pigs exposed to the synthetic pheromone were more (P < 0.05) active during the 48-h period of video taping than control pigs. Pigs exposed to the synthetic pheromone (either on the feeder or their snout) had increased (P < 0.01) average daily gain (ADG) and better (P < 0.01) feed:gain ratio than control pigs over the 28-d postweaning period. In conclusion, the putative synthetic pheromone, applied once at weaning, stimulated apparent feeding behaviors, and reduced fighting and apparent drinking behaviors during the first 48 h after weaning. ADG and feed:gain ratio were improved by application of the putative synthetic pheromone either directly on the feeder or when painted on the pigs' snouts. Olfactory signals can modulate adaptation to the postweaning environment in ways that may improve pig performance and welfare.     

The growth performance of the progeny of two swine sire lines reared under different floor space allowances

A total of 736 pigs was used in a study with a 2 x 2 x 2 factorial arrangement to investigate the effects of and interactions between sire line (Line A vs. B), floor space (unrestricted vs. restricted), and gender (barrow vs. gilt) on growth performance, BW, and protein and estimated lipid accretion curves from 40 to 120 kg of BW. Pigs were by eight Line-A and nine Line-B sires mated with PIC C22 dams. Line A was of Pietrain ancestry and Line B was a synthetic line. The unrestricted floor space treatment consisted of small groups (four pigs) with 0.93 m2/pig of floor space for the entire grow-finish period. Pigs in the restricted floor space were in larger groups (12 pigs) with 0.37 and 0.56 m2/pig of floor space for the grower and finisher phases, respectively. Pigs were given ad libitum access to a three-phase dietary program, and one and three nipple waterers were available in the groups of 4 and 12 pigs, respectively. No sire line x floor space interactions were found for any of the traits measured. Line A pigs grew more slowly (50 g/d, P < 0.05), took longer (4.1 d, P < 0.05) to reach harvest weight (120.3 kg), and had similar feed intakes, but a lower gain:feed ratio (2.8%, P < 0.05) than Line B pigs. Line A pigs had greater longissimus muscle depth (P < 0.05) and estimated protein accretion rate (P < 0.05) than Line B pigs, but Line A and Line B pigs had a similar estimated percentage of lipid-free soft tissue. Pigs reared in the restricted floor space grew more slowly (105 g/d, P < 0.05) and consumed less feed (280 g/d, P < 0.05) but had a similar (P > 0.05) gain:feed ratio to pigs reared in the unrestricted floor space. Pigs reared in the unrestricted floor space had greater (P < 0.05) predicted protein and lipid accretion rates throughout the growth period than pigs reared in the restricted floor space. Differences between genders for growth traits and carcass measurements were in agreement with previous research. The differences in growth performance, carcass measures, and compositional growth curves between these two sire lines were similar in the two floor spaces.     

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.     

Interaction of swine nursery and grow-finish space allocations on performance

Two experiments were conducted to evaluate the possible interaction of nursery space allocations and grow-finish space allocations in swine. In Exp. 1, crowding was achieved by varying the number of pigs per pen. During the nursery phase, decreasing the space allocation (0.16 m2/pig vs 0.25 m2/pig; 8 and 12 pens per treatment, respectively) by increasing the number of pigs per pen (18 vs 12) resulted in a decrease in daily feed intake (0.609 vs 0.683 kg/d; P < 0.001) and daily gain (0.364 vs 0.408 kg/d; P < 0.001). Pigs were mixed within nursery treatment groups and reassigned to grow-finish pens (6 pens per treatment) at the end of the 35-d nursery period providing either 0.56 m2/pig (14 pigs/pen) or 0.78 m2/pig (10 pigs/pen). Crowding during the grow-finish phase decreased daily feed intake (P < 0.003) and daily gain (P < 0.001). In Exp. 2, space allocations of 0.16 m2/pig vs 0.23 m2/pig during the nursery phase (24 pens per treatment) resulted in a decrease in daily feed intake (0.612 vs 0.654 kg/d; P < 0.005) and daily gain (0.403 vs 0.430 kg/d; P < 0.001). Pigs remained in the same (social) groups when moved to the grow-finish phase. Unlike Exp. 1, there was no effect of crowding during the grow-finish phase (0.60 m2/pig vs 0. 74 m2/pig) on daily feed intake or daily gain. The difference in results between experiments suggests that the response to crowding during the grow-finish phase may depend in part on whether pigs are mixed and sorted following movement from the nursery.     

Effect of group size on pig performance in a wean-to-finish production system

Crossbred pigs (n = 1,400) were used to evaluate the effect of group size (25 vs 50 vs 100 pigs/pen) in a wean-to-finish production system on growth performance and carcass measures. Pigs were weaned at 17 d (range = 15 to 19) of age with a mean initial BW of 5.9 +/- 0.02 kg and taken to a final mean pen weight of 116 +/- 0.9 kg. A 10-phase dietary regimen was used, and pigs had free access to feed and water. Feeder-trough space (4.3 cm/pig) and floor-area allowance (0.68 m2/pig) were the same for all group sizes. Compared to groups of 25, pigs in groups of 50 and 100 animals were lighter (P < 0.001) at the end of wk 8 after weaning and had lower (3%, P < 0.01) ADG and gain:feed (G/F) but similar (P > 0.05) ADFI during the first 8 wk of the study. At the end of the study, pig weight and the coefficient of variation in pig weight within a pen were similar (P > 0.05) across group sizes. During the period from 8 wk after weaning to the end of the study, pigs in groups of 100 compared to 50 animals had greater (3%, P < 0.01) ADG, and pigs in groups of 25 were intermediate for ADG. Average daily feed intake during this period was similar (P > 0.05) for all group sizes; however, G/F was greater (3%, P < 0.01) for groups of 100 compared to 25 or 50 animals. For the overall study period, ADG, ADFI, and G/F from weaning to slaughter weight were similar across group sizes (P > 0.05; 655, 648, and 658 g; 1,759, 1,755, and 1,759 g; and 0.37, 0.37, and 0.37; for ADG, ADFI, and G/F, respectively, for groups of 25, 50, and 100 pigs, respectively). Mortality was similar (P > 0.05) across group sizes; however, morbidity (pigs removed due to poor health or injury) was higher in groups of 25 pigs compared to the other two group sizes (7.0, 3.5, and 3.9% for groups of 25, 50, and 100, respectively; P < 0.05). Group-size treatment did not affect (P > 0.05) carcass dressing percentage, backfat thickness, or loin-eye depth. In summary, growth performance from weaning to market weight was not affected by group size.     

Group size and floor-space allowance can affect weanling-pig performance

Crossbred weanling piglets (n = 1,920; mean initial BW, 5.3 +/- .7 kg) were used in two 9-wk trials employing a randomized block design in a 2 x 2 factorial arrangement of treatments to determine effects of group size (20 [Small = S] or 100 [Large = L] pigs/pen) and floor-space allowance (calculated requirement [CR] or calculated requirement less 50% of estimated "free space" [CR-50]) on growth performance. Free space was estimated for each group size. From wk 1 through 4 after weaning, S and L groups at CR were allowed a floor space of .17 m2/pig, and at CR-50, S and L groups were allowed .15 m2/pig and .13 m2/pig, respectively. From wk 5 through 9 after weaning, all CR treatment pigs were provided a floor space of .38 m2/pig, and for the CR-50 treatment, S and L pigs were allowed .32 m2/pig and .28 m2/pig, respectively. Piglets had free access to feed and water. Feeder-trough space per pig was the same for both group sizes. Feed-intake data were collected for only wk 1 through 4. Group size by floor-space allowance interactions (P < .05) were found for gain/feed ratio (G/F) for wk 1 and wk 2 through 4, but not for wk 1 through 4. Piglets in L groups were lighter (P < .001) at the end of wk 1, 4, and 9 by 2, 4, and 5%, respectively, and had lower ADG (6%; P < .001) throughout the trial than S piglets. During wk 1 through 4, feed intake was lower (7%, P < .001) in L piglets than in S piglets, but G/F was similar (P > .05). Piglets in CR groups had greater ADG (5%; P < .01) throughout the trial, with a greater G/F (P < .05) for wk 1 through 4, and were heavier (P < .01) than those in CR-50 groups at the end of wk 4 (3%) and 9 (4%). Pigs in L groups had a greater within-pen coefficient of variation in BW at the end of wk 9 than pigs in S groups. Large groups and reduced floor-space allowance reduced piglet growth performance in the nursery.     

Effects of beta-glucan obtained from the Chinese herb Astragalus membranaceus and lipopolysaccharide challenge on performance, immunological, adrenal, and somatotropic responses of weanling pigs

A total of 108 crossbred piglets (7.75 +/- 0.24 kg of BW) weaned at 28 d was used to study the interactive effects of beta-glucan obtained from the Chinese herb Astragalus membranaceus (AM) and Escherichia coli lipopolysaccharide (LPS) challenge on performance, immunological, adrenal, and somatotropic responses of weaned pigs. The treatments were in a 2 x 3 factorial arrangement; main effects were level of Astragalus membranaceus glucan (AMG; 0, 500, or 1,000 mg/kg; as-fed basis) and presence of immunological challenge (with or without LPS). The experiment included six replicate pens per treatment and three pigs per pen. Lipopolysaccharide challenges were conducted on d 7 and 21 of the trial. Blood samples were obtained from the vena cava from one pig per pen at 3 h after LPS challenge to determine plasma responses. Weight gain and feed:gain ratio were unaffected by glucan. However, there was a quadratic effect on feed intake (P < 0.05): pigs fed 500 mg of glucan/kg had the highest feed intake. Immunological challenge with LPS decreased weight gain (P = 0.02). An interaction (P = 0.01 to 0.09) between AMG and LPS was observed for glucose, IL-1beta, PGE2, and cortisol. Astragalus membranaceus glucan had a quadratic effect on the plasma concentrations of glucose, IL-1beta, PGE2, and cortisol (P < 0.05) after both LPS challenges. Plasma concentrations of glucose, IL-1beta, PGE2, and cortisol (P < 0.05) were all increased in LPS-challenged pigs compared with the control pigs after both LPS challenges. The IGF-I concentrations were less for LPS-challenged pigs than for unchallenged pigs. The lymphocyte proliferation response of peripheral blood induced by 5 microg of concanavalin A/mL (P < 0.01) and IL-2 bioactivity (P < 0.05) increased linearly with increasing addition of glucan. Pigs challenged with LPS had greater T-lymphocyte proliferation (P = 0.06) and IL-2 bioactivity (P = 0.07) than unchallenged pigs after the first immunological challenge but not after the second. In conclusion, although glucan did not improve pig performance under the conditions of the present experiment, when included at 500 mg/kg, it decreased the release of inflammatory cytokine and corticosteroid and improved the lymphocyte proliferation response of weanling piglets via enhanced IL-2 bioactivity.