Effects of diet and housing density on growth and stomach morphology in pigs.

Two experiments were conducted to evaluate the impact of housing density on the stomach morphology of growing pigs and determine whether there was an interaction between housing density and diet. All diets were corn-soybean meal based. In Exp. 1, 42 barrows (41.0+/-.95 kg BW) were allotted either individually or three pigs per pen to evaluate the effects of crowding on stomach lesions. Pen space per pig was 1.54 and .51 m2, respectively. All pigs were fed a finely ground and pelleted diet (610 microm) for 6 wk. The ADG decreased (P<.05) for the pigs housed three per pen during wk 4 to 6 only. There was no effect of housing density on feed intake or gain/feed ratio. Neither visual nor histological ulcer score differed between the two treatment groups. No stomachs were graded as normal. In Exp. 2, 80 barrows (39.8+/-.9 kg BW) were allotted either two or four pigs per pen. Pen space per pig was .77 and .39 m2, respectively. Half of the pigs in each housing situation were fed a coarse meal diet (1,050 microm), and half of the pigs were fed a finely ground and pelleted diet (577 microm) throughout the 49-d experimental period. Throughout the trial, pigs housed two per pen gained at a greater rate (P<.05) than pigs housed four per pen. From d 14 to the end of the trial, pigs consuming the finely ground and pelleted diet gained at a greater rate (P<.05) than pigs fed the coarse meal diet. The differences in ADG were reflected in final body weight. Stomach weight as a percentage of body weight was higher for animals on the coarse meal diet. Visual and histological ulcer scores were similar, and both were higher (P<.001) on the finely ground and pelleted diet, indicating greater damage. There was no effect of space restriction on stomach morphology. These data show the major effect of diet type on stomach lesions with no interaction with space restriction.     

Lack of transmission of porcine circovirus type 2 to weanling pigs by feeding them spray-dried porcine plasma

An experiment was conducted to determine whether spray-dried porcine plasma containing 2.47 x 10(5) dna copies of porcine circovirus type 2 (pcv-2) could infect weanling pigs when fed to them. Five specific pathogen-free (spf) weanling pigs were fed ad libitum for 45 days a control diet and six pigs were fed a test diet containing 8 kg sdpp per 100 kg feed. The two groups were housed in separate biosecurity level-3 rooms. None of the pigs in either group developed any clinical signs or became pcv-2 viraemic or seroconverted.     

Liquid diets accelerate the growth of early-weaned pigs and the effects are maintained to market weight

Piglets (n = 240, 11.0+/-0.1 d old, 3.93+/-0.05 kg) were allotted to one of four treatments in a 2 x 2 factorial arrangement to examine the effects of diet physical form and nursery environment during the first 14 d after weaning on growth to market weight. During the treatment period, pigs were housed (10 pigs/ pen) in either a conventional hot nursery (30 degrees C) or a segregated-temperature nursery (cool ambient temp. of 24 degrees C, with enclosed hot-box hovers at 32 degrees C). Pigs in each environment were fed nutritionally identical diets in either liquid or dry-pellet form for 14 d. Subsequently, all pigs were fed identical dry diets and were housed in common grower-finisher facilities (penned by sex, five pigs/pen). At the end of the treatment period (d 14), pigs fed the liquid diet were 21% heavier than pigs fed the dry pellet diet (9.22 vs 7.60 kg; P < 0.001). Similarly, gain, feed intake, and gain/feed of liquid-fed pigs were 44%, 18%, and 22% greater, respectively, than observed for pigs fed the dry pellet diet. No main effect of environment was observed (P > 0.10); however, an interaction with diet physical form occurred during the early-nursery period (P < 0.01). Pigs fed the liquid diet showed better performance in the conventional nursery, whereas pigs fed the dry pellet diet were favored in the segregated-temperature nursery. No major differences in growth performance or in ultrasound carcass measurements were detected during the growing-finishing period; however, the advantage in body weight of liquid-fed pigs gained during the first 2 wk postweaning was maintained to the end of the trial (113.9 vs 110.6 kg; P < 0.05). Pigs that were fed the early-nursery diet in liquid form reached market weight (110 kg) 3.7 d sooner than the dry-fed controls (P < 0.01). Estimates of lean gain (calculated from live ultrasound data) were unaffected, suggesting that composition of growth was not altered. Collectively, these results show that liquid feeding during early life can markedly accelerate piglet growth performance and that the growth advantage is maintained to market weight, with no evidence of compensatory gain in the dry-fed control pigs.     

Effects of Fusarium toxins on growth, humoral immune response and internal organs in weaner pigs, and the efficacy of apple pomace as an antidote

A feeding trial using 220 weaner pigs which comprised two experimental series was conducted to investigate the effects of diets contaminated with the Fusarium toxins deoxynivalenol (DON) and zearalenone (ZON) and to test the hypothesis that apple pomace acts as an antidote to these mycotoxins. Two diets without contaminated wheat, containing either no pomace or 8% pomace, and two diets with naturally contaminated wheat (3.2 mg DON and 0.06 mg ZON, and 2.1 mg DON and 0.25 mg ZON per kg diet in series 1 and 2 respectively), containing either no pomace or 8% pomace were fed ad libitum for 5 weeks. Mycotoxin exposure lowered feed intake (p < 0.01) and growth (p = 0.05), and tended to decrease the energy conversion ratio (p = 0.06). Although the intake of apple pomace did not increase feed intake, it increased the growth rate (p = 0.04), mainly by restoring growth in the presence of mycotoxins (p = 0.08 for the interaction mycotoxin x pomace). In the first experimental series, the animals were immunized with a parvovirus vaccine. The percentage of seroconverting animals did not differ between the treatments (p = 0.56), which indicates that DON did not affect the humoral immune response. In the second experimental series, female piglets fed the contaminated diets had heavier uteri than piglets fed the uncontaminated diets (p < 0.01), regardless of pomace supplementation. The results show that pomace may alleviate the negative effect of DON on growth but does not counteract the hormonal effects of ZON.     

Performance measured in pigs with pneumonia and housed in different environments

During an investigation of poor growth performance, rate of weight gain and feed efficiency were studied in pigs with pneumonia. During the study, pigs either were housed in an improved environment or remained at their home farm. In both environments, rate of gain tended to decrease in association with increasing severity of pneumonia. When pigs with similar extent of lung lesions were compared, growth performance of pigs housed in the improved environment was better than that of pigs on the home farm. However, growth performance of pigs with pneumonia affecting greater than 20% of lung tissue was equally poor in either environment. When type of housing and extent of pneumonia were included in a model for analysis of variance, housing had a highly significant (P = 0.003) effect on rate of gain, and pneumonia had a nonsignificant effect.     

Zinc-amino acid complexes for swine

Two experiments were conducted to determine the effect of sources of dietary zinc on gain, feed conversion and blood and bone traits of swine. In the first experiment 96 pigs were used in a 28-d study. The pigs were fed diets with no supplemental Zn or with either 9 or 12 ppm supplemental Zn from zinc sulfate (ZnSO4), zinc methionine (ZnMet) or zinc methionine with picolinic acid (ZnMet w/PA), each with or without 5% added corn oil. There were differences (P less than .05) in average daily gain (ADG) and average daily feed intake (ADFI) between the pigs fed the two organic Zn sources, with those fed ZnMet w/PA showing the better gains and feed conversion. However, neither organic Zn source resulted in pig performance that was different from either the diet with no supplemental Zn or the diets supplemented with Zn from ZnSO4. In the second experiment the same dietary Zn sources and treatments were fed as in Exp. 1 except that corn oil was deleted as a variable. No differences in ADG, ADFI, feed/gain (F/G) or in changes in serum Zn or Cu were observed among treatments during either the 21-d nursery or the 56-d growing periods. During the subsequent 56-d finishing period ADG and ADFI were greater (P less than .01) for pigs fed the Zn-supplemented diets than for those fed the diets without supplemental Zn. There were no differences among treatments in F/G during the finishing period. Zn content of bone ash was lower (P less than .01) in the non-Zn-supplemented pigs. These data suggest that the Zn sources used are of similar biological value and do not support the theory that picolinic acid aids Zn absorption.     

高活菌发酵饲料对生长肥育猪生产性能的影响

选用240头日龄相近、体况一致的杜×长×大三元杂交肥育猪,随机平均分为3个处理,对照组、试验1组和试验2组。对照组饲喂基础日粮加抗生素,试验1组和试验2组分别在基础日粮中添加4%和8%的高活菌发酵饲料。试验结果表明:在28d的饲养试验中,试验2组饲养效果最好,平均日增重比对照组提高12.34%,采食量增加7.90%,料肉比减少4.0%,腹泻率降低2.89%。应用高活菌发酵饲料饲喂生长肥育猪能起到促进其生长、减少腹泻以及改善仔猪肠道健康的功效。     

Performance of growing-finishing pigs fed diets containing Roundup Ready corn (event nk603), a nontransgenic genetically similar corn, or conventional corn lines

Two studies were conducted at two locations to evaluate growth performance and carcass characteristics of growing-finishing pigs fed diets containing either glyphosate-tolerant Roundup Ready (event nk603) corn, a nontransgenic genetically similar control corn (RX670), or two conventional sources of nontransgenic corn (RX740 and DK647). A randomized complete block design (three and four blocks in Studies 1 and 2, respectively) with a 2 x 4 factorial arrangement of treatments (two genders and four corn lines) was used. Study 1 used 72 barrows and 72 gilts (housed in single-gender groups of six; six pens per dietary treatment) with initial and final BW of approximately 22 and 116 kg, respectively. Study 2 used 80 barrows and 80 gilts (housed in single-gender groups of five; eight pens per dietary treatment) with initial and final BW of approximately 30 and 120 kg, respectively. Pigs were housed in a modified open-front building in Study 1 and in an environmentally controlled finishing building in Study 2. The test corns were included at a fixed proportion of the diet in both studies. Animals had ad libitum access to feed and water. Pigs were slaughtered using standard procedures and carcass measurements were taken. In Study 1, overall ADG, ADFI (as-fed basis), and gain:feed (G:F) were not affected (P > 0.05) by corn line. In Study 2, there was no effect of corn line on overall ADFI (as-fed basis) or G:F ratio. In addition, overall ADG of barrows fed the four corn lines did not differ (P > 0.05); however, overall ADG of gilts fed corn DK647 was greater (P < 0.05) than that of pigs fed the other corn lines. There was no effect (P > 0.05) of corn line on carcass yield or fatness measurements in either study. Differences between barrows and gilts for growth and carcass traits were generally similar for both studies and in line with previous research. Overall, these results indicate that Roundup Ready corn (nk603) gives equivalent animal performance to conventional corn for growing pigs.     

Commercial spray-dried porcine plasma does not transmit porcine circovirus type 2 in weaned pigs challenged with porcine reproductive and respiratory syndrome virus

The objective of this study was to evaluate if spray dried porcine plasma (SDPP) containing porcine circovirus type 2 (PCV2) genome supplemented in feed could transmit PCV2 to pigs challenged with porcine reproductive and respiratory syndrome virus (PRRSV). Twenty-three PRRSV-free pigs, non-viraemic for PCV2, were housed in bio-safety level 3 facilities and assigned to four groups in a 2×2 factorial design consisting of PRRSV challenge and a negative control. The diet contained 0 or 8kg SDPP per 100kg of feed. PRRSV challenge groups were inoculated intranasally with 2mL of a suspension containing 10(6) TCID(50)/mL PRRSV. The SDPP used in the study contained 7.56×10(5) PCV2 genome copies per gram. Dietary treatments were fed from 4days prior to PRRSV inoculation until 28days post-inoculation (PI). All challenged pigs developed PRRSV viraemia by day 3PI and PRRSV antibodies were detected in sera by day 14PI, with no difference between diet treatments. Neither PRRSV viraemia nor seroconversion was observed in non-challenged pigs. PCV2 was not detected in the serum of any pigs throughout the experimental period. SDPP containing the PCV2 genome supplemented in feed did not result in PCV2 transmission to either healthy or PRRSV-infected pigs under these experimental conditions.     

Growth performance of pigs fed diets with and without tylosin phosphate supplementation and reared in a biosecure all-in all-out housing system

Three hundred and eighty-four pigs, mean initial live weight of 20.8 kg, were assigned randomly to groups of 24 (12 females, 12 castrated males). Each group was randomly assigned to 1 of 2 dietary treatments consisting of the same commercial barley-based diet, with or without the addition of tylosin phosphate. The barn where the animals were housed operates as an all-in all-out facility, and all pigs arrived on the same day as part of a group of 960 pigs. No new pigs were introduced into the facility during the period of this trial and pigs were sent to market over a 4-week period upon achieving a live weight of 110 kg. The pigs were weighed at the beginning of the trial and when they left the facility for slaughter. Feed consumption and incidence of disease, mortality, or both were recorded daily. At slaughter, carcass backfat depth over the last rib, 6.5 cm ventral to the dorsal midline (P-2 site); loin depth; carcass weight; predicted lean yield; and grade index were recorded. The sow herd supplying pigs to the unit was known to be free of the major swine diseases such as swine influenza, mycoplasma pneumonia, porcine reproductive and respiratory syndrome (PRRS), necroproliferative enteritis, and ascarids. A strict biosecurity protocol was employed to minimize the risk of introducing disease organisms into the unit. Prior to this study, no subtherapeutic antibiotics had been used in this facility. Tylosin phosphate supplementation had no significant effect on final weight, days on test, total gain, and daily gain. In both treatments, the pigs reached a mean market weight of 110.2 kg within 94.1 days, resulting in daily gains of the order of 950 grams per day. Due to the design of the trial, it was difficult to measure significant feed consumption effects. Feed consumption and conversion appeared to be similar for pigs in both treatment groups. At slaughter, tylosin phosphate supplementation appeared to significantly increase lean muscle content of the carcass as measured by loin muscle depth (P = 0.04). Mortality rates and the number of underweight pigs sent to market were low for this trial. Mortality was similar for both treatments; however, more of the control pigs than of the tylosin phosphate fed pigs were underweight when sent to market. From the results of this study, it appears that pigs of fast growing genotypes fed adequate diets and housed in a biosecure environment do not require dietary tylosin phosphate supplementation in order to maximize growth. There is some indication that tylosin phosphate supplementation may improve lean content of the carcass in pigs housed in such an environment.     

Microbial and nutritional aspects of feeding fermented feed (poultry by‐products) to pigs

Summary

Broiler by‐products (heads, feet, and viscera) mixed with 4% dextrose were pasteurized for 4 min at 90°C core temperature, cooled to 20°C, and fermented with Lactobacillus plantarum as starter culture. These fermented poultry by‐products were fed to 12 individually housed fattening pigs as part (17.6% of the dry matter) of their fattening ration, the remainder composed of compound pig feed. Control pigs received a compound pig feed only. Both groups of pigs were fed restrictively on the basis of body weight. The technical results of the pigs fed the experimental diet showed a significantly improved feed:gain ratio (2.46 vs 2.57), a significantly higher carcass weight (86.1 vs 81.8 kg), a lower meat percentage (50.9 vs 52.5%) and an increased backfat thickness (21.5 vs 18.7%). The bacterial flora in the intestinal tract of the pigs fed the experimental diet differed significantly from the control animals. Decreased colony counts of mesophilic aerobic bacteria, Enterobacteriaceae, enterococci and lactobacilli were found in the rectal content and the prevalence of salmonella was lower.

It is suggested that the improved feed:gain ratio and the reduced bacterial activity of the measured groups of bacteria is a result of 1) the higher energy content of the diet, and(or) 2) an assumed enhanced digestibility of nutritional components in the diet, and(or) 3) the lower incidence of diarrhea in the pigs fed with fermented poultry by‐products. This resulted in a lower contamination level of enteropathogenic bacteria like, salmonella and Escherichia coli, in the gastro‐intestinal tract of the pigs fed fermented poultry by‐products.     

Effects of the antimicrobial growth promoter tylosin on subclinical infection of pigs with Salmonella enterica serotype Typhimurium

OBJECTIVE: To determine whether feeding tylosin, an antimicrobial growth promoter, to pigs was associated with increased risk of infection with and excretion of Salmonella enterica serotype Typhimurium. ANIMALS: 17 healthy pigs. PROCEDURE: A commercial pelleted dry feed was given in 2 feeding trials. In trial A, 11 pigs were given feed with tylosin, 11 pigs were given feed without tylosin, and 11 pigs were given feed with tylosin before and feed without tylosin after inoculation with S Typhimurium. In trial B, 44 pigs were given feed that contained tylosin, and 44 pigs were given feed without tylosin. Three weeks after the start of each trial, pigs were orally inoculated with approximately 5 x 10(6) colony-forming units of S Typhimurium. Feces were examined for S Typhimurium, using semiquantitative microbiologic techniques before and for 5 or 6 weeks after inoculation. Serum antibody titers against S enterica were measured by use of ELISA. RESULTS: None of the pigs developed clinical signs of salmonellosis. However, after inoculation, S Typhimurium was isolated from feces of most pigs, and all but 2 pigs developed serum antibodies against S enterica. Significant differences were not detected between experimental and control groups in either trial. CONCLUSIONS AND CLINICAL RELEVANCE: Results indicate that tylosin fed as an antimicrobial growth promoter to pigs may not be an important factor in promoting infection with or excretion of S enterica serotype Typhimurium.     

Influence of hog lice, Haematopinus suis, on blood components, behavior, weight gain and feed efficiency of pigs

Blood components, behavior, weight gain and feed efficiency were studied in 40 weaner pigs infested with lice and 40 left uninfested (controls). Packed cell volumes and concentrations of hemoglobin, serum proteins, leukocytes, serum globulins, and serum albumins increased significantly in both groups. Eosinophil concentrations increased and neutrophil concentrations decreased in the infested group but not in the controls. There was a significant increase in erythrocyte concentrations in the control group while the infested group's erythrocyte concentrations decreased at the middle of the experiment. Blood of infested and uninfested pigs showed no significant differences from pre-infestation values in sedimentation rates and concentrations of fibrinogen, basophils, and monocytes. Control pigs spent more time at feeders and more time active while not at feeders. Nevertheless, average daily gains (ADG) and feed efficiencies (FE) of the two groups were not significantly different. When ADG and FE were grouped by severity of Haematopinus suis infestation, pigs with more H. suis had higher ADG and better FE than pigs with fewer or no lice. The results suggest that a decrease in activity by infested pigs allows them to save energy which is then available for growth.     

Influence of Psoroptes ovis on the energy metabolism of heifer calves

To determine the effect of Psoroptes ovis on the energy metabolism of heifers, 32 calves were randomly assigned to four treatments in a 2 X 2 factorial arrangement. Calves were fed the same diet at two intake levels, high or low, and were either infested or were not infested with P. ovis mites. Calves were housed in antigrooming stanchions. Body composition was determined by urea dilution on Days 0 and 63. Ration digestibility was determined on fecal grab samples using acid-insoluble ash as a marker. Infested calves had developed a severe P. ovis infestation 7 weeks following exposure and had significantly lower daily gain, gain:feed, and energy retention and higher serum glutamic-oxaloacetic transaminase than control calves. P. ovis infestation increased the maintenance energy requirement of calves by greater than 50% (79 vs. 123 kcal of net energy kg-1 body wt.75). For each 10% increase in the body surface affected by P. ovis, maintenance energy requirement increased 0.5 mcal day-1.     

Influence of sarcoptic mange and cold and ambient temperature on blastogenic responses of lymphocytes and serum cortisol concentrations of pigs

Blood samples from sarcoptic mite-infested pigs were evaluated for effects of mite infestation and cold and ambient temperatures on lymphocyte blastogenic responses and for effects of mite infestation on serum cortisol concentrations. In experiment 1, sarcoptic mite-infested and noninfested pigs were housed in cold (5 to 15 C fluctuating) and thermoneural (25 C) environmental chambers for 5 weeks. Differences were not observed (P greater than 0.10) in blastogenic responses to phytohemagglutin or pokeweed mitogen between lymphocytes from infested and noninfested pigs on postinfestation days (PID) 7, 21, 28, and 35 in either environmental chamber. When lymphocytes from noninfested pigs were cultured with sera from infested pigs, alterations of blastogenic responses were not detected. Cortisol values were higher (P less than 0.05) in sera from sarcoptic mite-infested pigs, compared with those from noninfested pigs, at 4 PM on PID 14 and 4 AM and 10 AM on PID 15. Cortisol values were higher (P less than 0.05) in sera obtained at 10 AM on PID 14 and at 10 AM on PID 15 from pigs housed in cold chambers, compared with those from pigs housed in thermoneutral chambers. Interactive effects between sarcoptic mite infestation and cold ambient temperatures were not observed. At 4 AM on PID 15 (experiment 2), cortisol values were higher (P less than 0.05) in sera of infested pigs, compared with those in noninfested pigs. Seemingly, sarcoptic mange in pigs did not alter mitogen-induced lymphocyte blastogenic responses, but did increase serum cortisol concentrations, indicating that sarcoptic mange may be a stressor in pigs.     

Performance and endocrine responses of group housed weaner pigs exposed to the air quality of a commercial environment

The growth performance and endocrine responses of male weaner pigs (3 to 8 weeks of age) was evaluated in two different environments (clean and dirty) and housing (single or groups of 10 pigs/pen) conditions. The dirty environment contained significantly elevated ammonia, carbon dioxide and dust levels compared with the clean environment. Pigs grew faster and consumed more feed in the clean environment and this was associated with reduced plasma cortisol concentrations compared with pigs in the dirty environment. Pigs housed in groups in the dirty environment had increased β-endorphin and decreased IGF-I concentrations compared to group housed pigs in the clean environment. Feed conversion efficiency did not differ due to environment or group housing. Plasma concentration of cortisol, β-endorphin, IGF-I and IGF-II did not differ between single and group housed pigs. Activity of the hypothalamic-pituitary-adrenal (HPA) axis was greater in response to environmental conditions than group housing, and this was associated with reduced growth in weaner pigs.     

Effects of restricted feed intake on finishing pigs weighing between 68 and 114 kilograms fed twice or 6 times daily

In a previous study with limit-fed gestating gilts, we observed that gilts fed 6 times/d had greater ADG than those fed the same amount over 2 feedings. To confirm these earlier responses, we used finishing pigs as a model in two 42-d trials and two 28-d trials to evaluate the effects of restricted feed intake and feeding frequency (2 vs. 6 times/d, floor fed) on pig performance between 68 and 114 kg. In all experiments, pigs (10/pen) were housed in 1.8 × 3.1 m pens with a half-solid, half-slatted concrete floor. Pigs were fed a corn- and soybean meal-based diet formulated to 1.15% standardized ileal digestible Lys and 3,294 kcal of ME/kg. In Exp. 1 to 3, energy and Lys were supplied to pigs according to NRC (1998) calculations to target an ADG of 0.80 kg. In Exp. 4, the diet was supplied to pigs to target an ADG of 0.80 kg (low feed intake) or 0.95 kg (high feed intake) to determine if the amount of energy above the maintenance requirement and feeding frequency affected pig performance. Pigs were fed by dropping similar amounts of feed onto the solid concrete floor either 2 (0700 or 1400 h) or 6 times (3 meals within 2 h at the morning and afternoon feedings) per day with an Accu-Drop Feed Dispenser (AP Systems, Assumption, IL). In Exp. 1 and 2, pigs fed 6 times daily had increased (P < 0.02) ADG and G:F compared with pigs fed 2 times per day. Greater feeding frequency increased (P < 0.05) the duration of time spent feeding and standing and reduced the lying time. In Exp. 3, a third treatment was included to determine whether the improvements in performance were due to decreased feed wastage. This treatment was designed to minimize feed wastage by dropping feed closer to the floor for pigs fed 2 times per day. Pigs fed 6 times daily had improved (P < 0.05) ADG and G:F compared with pigs in either treatment fed 2 times per day. No difference (P > 0.05) in performance was observed between pigs fed 2 times per day when feed was dropped from the feed drop or by the modified method. In Exp. 4, increasing the feeding frequency from 2 to 6 times per day improved (P < 0.01) ADG and G:F for pigs fed the low feed intake and tended to increase (P < 0.06) ADG and improved (P < 0.05) G:F for pigs fed the high feed intake. In limit-feeding situations, increasing the frequency of feeding from 2 to 6 times per day improved pig performance, which confirmed our earlier findings in gestating gilts.     

Effect of housing conditions (clean vs. dirty) on growth performance and feeding behavior in growing pigs in a tropical climate

The effect of bad sanitary conditions on growth performance and feeding behaviour were studied on a total of 48 Large White pigs between 95 and 130 d of age. This experiment carried out during the hot season in a tropical humid climate. Two groups of 12 pigs each were housed in a clean environment in which the pens were disinfected thoroughly prior to stocking and maintained in a clean state by daily washing the pens and by weekly emptying the manure stored beneath the partial concrete floor. The dirty environment was achieved by not cleaning the pens prior to stocking or throughout the experiment and by storing the manure beneath the floor slats throughout the experimental period. The microbial pressure was increased by introducing 5 additional non experimental pigs near each experimental dirty pen. Feeding behaviour parameters were measured using automatic feed dispensers. Pigs housed in a clean environment consumed more feed (2.283 vs. 1.953 kg/d; P < 0.001) and grew faster (871 vs. 780 g/d; P < 0.05) than those housed in the dirty environment. No significant effect on treatment was reported for the feed conversion efficiency (2.70 kg/kg on average). The reduced average daily feed intake in dirty pens was associated with a reduction of the meal size (334 vs. 282 g/meal; P = 0.10) whereas the meal frequency was not affected by treatment (7.5 meals/d on average). The rate of feed intake was significantly higher in the clean than in the dirty environment (34.0 vs. 29.9 g/min; P < 0.05).     

Responses to dietary additions of fiber (alfalfa meal) in growing pigs housed in a cold, warm or hot thermal environment

Five trials involving 112 individually-penned animals were conducted to determine the effects of dietary fiber additions (0 or 10% dehydrated alfalfa meal) on the rate and efficiency of growth and carcass characteristics of growing pigs housed in a cold (10 C), thermoneutral (22.5 C) or hot (35 C) thermal environment. Cold exposure (10 C) depressed efficiency of feed and energy utilization, carcass length, backfat, cold carcass dressing percentage and percentage lean cuts. Exposure to the hot environment resulted in depressed live weight gains but did not alter the efficiency of feed utilization. Dietary additions of alfalfa meal depressed daily gains by 1, 3 and 5% in pigs housed in the cold, warm and hot environments, respectively, and gain:feed ratios by 1, 7 and 10%. Ingestion of the fibrous alfalfa meal depressed cold carcass dressing percentage in the 10 and 22 C environments as compared with the basal diet. Based on these data, the nutritional value of fibrous feedstuffs (15% total dietary neutral detergent fiber or less) for growing pigs allowed to consume feed ad libitum is greater in animals housed in a moderately cold vs a warm or hot thermal environment.     

Influence of dietary protein level, amino acid supplementation, and dietary energy levels on growing-finishing pig performance and carcass composition

Two experiments were conducted to determine the effects of feeding reduced-CP, AA-supplemented diets at two ambient temperatures (Exp. 1) or three levels of dietary NE (Exp. 2) on pig performance and carcass composition. In Exp. 1, 240 mixed-sex pigs were used to test whether projected differences in heat increment associated with diet composition affect pig performance. There were 10 replications of each treatment with four pigs per pen. For the 28-d trial, average initial and final BW were 28.7 kg and 47.5 kg, respectively. Pigs were maintained in a thermoneutral (23 degrees C) or heat-stressed (33 degrees C) environment and fed a 16% CP diet, a 12% CP diet, or a 12% CP diet supplemented with crystalline Lys, Trp, and Thr (on an as-fed basis). Pigs gained at similar rates when fed the 16% CP diet or the 12% CP diet supplemented with Lys, Trp, and Thr (P > 0.10). Pigs fed the 12% CP, AA-supplemented diet had a gain:feed similar to pigs fed the 16% CP diet when housed in the 23 degrees C environment but had a lower gain:feed in the 33 degrees C environment (diet x temperature, P < 0.01). In Exp. 2, 702 gilts were allotted to six treatments with nine replicates per treatment. Average initial and final BW were 25.3 and 109.7 kg, respectively. Gilts were fed two levels of CP (high CP with minimal crystalline AA supplementation or low CP with supplementation of Lys, Trp, Thr, and Met) and three levels of NE (high, medium, or low) in a 2 x 3 factorial arrangement. A four-phase feeding program was used, with diets containing apparent digestible Lys levels of 0.96, 0.75, 0.60, and 0.48% switched at a pig BW of 41.0, 58.8, and 82.3 kg, respectively. Pigs fed the low-CP, AA-supplemented diets had rates of growth and feed intake similar to pigs fed the high-CP diets. Dietary NE interacted with CP level for gain:feed (P < 0.06). A decrease in dietary NE from the highest NE level decreased gain:feed in pigs fed the high-CP diet; however, gain:feed declined in pigs fed the low-CP, AA-supplemented diet only when dietary NE was decreased to the lowest level. There was a slight reduction in longissimus area in pigs fed the low-CP diets (P < 0.08), but other estimates of carcass muscle did not differ (P > 0.10). These data suggest that pigs fed low-CP, AA-supplemented diets have performance and carcass characteristics similar to pigs fed higher levels of CP and that alterations in dietary NE do not have a discernible effect on pig performance or carcass composition.