Effects of fasting prior to slaughter on pH development and energy metabolism post-mortem in M. longissimus dorsi of pigs

The aim of this study was to investigate the effect of pre-slaughter fasting time, sex and feeding regime on the development of energy metabolism and pH in M. longissimus dorsi (LD) post-mortem in pigs. Two hundred and seventy pigs of the commercial Norwegian crossbreed Noroc (LYLD) were used involving two sexes (gilts and castrates), two feeding regimes (restricted and ad libitum) and four different fasting treatments: (F4) 4 h fasting, (F175) 17.5 h fasting on the farm, (FO175) 17.5 h fasting overnight at the abattoir, and (FO265) 26.5 h fasting overnight at the abattoir. Additionally the pigs experienced two different abattoir lairage times as fasting treatment F4 and F175 had a lairage time of 1.5 h, while fasting treatment FO175 and FO265 had a lairage time of 23.0 h. A short fasting time of 4 h led to a delayed degradation of glycogen, slow decline in pH and a lower ultimate pH_{45 h} post-mortem (pHu) in the LD compared with a fasting time of 26.5 h which resulted in a rapid breakdown of glycogen and pH decline early post-mortem and a high pHu. Proglycogen was degraded in favour of macroglycogen under anaerobic conditions post-mortem. Feeding the animals in the morning before delivery if slaughtered the same day, results in low pH reduction rate and a low pHu compared with pigs fasted overnight either on farm or at the abattoir. Aiming a higher pHu in LD it should be recommended not to feed the pigs in the morning at the day of slaughter.     

Bayesian meta-analysis of the effect of fasting, transport and lairage times on four attributes of pork meat quality

Technological meat quality is a significant economic factor in pork production, and numerous publications have shown that it is strongly influenced both by genetic status and by rearing and slaughter conditions. The quality of meat is often described by meat pH at different times postmortem, as well as by color and drip loss. A meta-analysis based on a database built from 27 studies corresponding to a total of 6526 animals classified was carried out. The purpose of this meta-analysis was to study the effect of fasting, lairage and transport durations on four main attributes of the technological pork meat quality. A Bayesian hierarchical meta-regression approach was adopted.The results of our meta-analysis showed that fasting time had a significant effect on pH measured 24 h post-mortem (pHu) and drip loss (DL) measured in longissimus muscle. While, lairage affected only the pHu in semimembranosus muscle. Interestingly, we found that DL was the lone attribute that was affected by transport time and its interaction with fasting time.     

Effects of lairage time on welfare indicators,energy metabolism and meat quality of pigs in Beijing

A total of forty Duroc–Landrace–Large White female pigs (90 ± 5 kg) were used to study the effects of different lairage times (0 h, 3 h, 8 h, 24 h) on welfare, energy metabolism and meat quality. The results showed that lairage time of 3 h led to a lower blood cortisol, a decreased drip loss and a delayed degradation of glycogen in muscles compared with pigs without rest, while lairage times of 8 h and 24 h resulted in a significant increase in pork toughness. It was concluded that three hours of lairage was appropriate to reduce pre-slaughter stress and obtain better meat quality for pigs transported for 4 h in winter, under the most frequent commercial conditions in Beijing, China. No lairage, or excessively long lairage time, might compromise animal welfare and meat quality.     

The effect of transportation on the expression of heat shock proteins and meat quality of M. longissimus dorsi in pigs

This study investigates the effect of different transport times on meat quality and the correlation between meat quality and Hsp expression in M. longissimus dorsi (LD) of pigs. After transportation for 1 h, 2 h or 4 h, respectively, blood plasma creatine kinase (CK) and lactate dehydrogenase (LDH) increased. The LD meat from 1 h and 2 h transported pigs had lower initial and ultimate pH values (pHi and pHu, respectively), higher drip loss and L^∗ values compared to controls, indicating a higher likelihood of pale, soft and exudative (PSE) meat. Meat quality was lower after 2 h compared to 1 h or 4 h of transport. All four Hsps tested (alpha-B-crystalline, Hsp27, Hsp70 and Hsp90) by ELISA in the LD tissue of pigs tended to decrease after transportation. One possible mechanism resulting in poor meat quality in the LD after transport seems to be a decline in Hsp expression.     

Electrical stimulation of pigs-effect on pH fall, meat quality and Cathepsin B+L activity

This work was performed to evaluate the effect of electrical stimulation (ES) on pH fall and meat quality of LD and BF in Danish halothane free pigs stunned with CO(2). ES resulted in a significant drop in pH of 0.3 units in both LD and BF and 3 h lairage resulted in 0.1 units lower pH at 20 min post mortem. Lairage time did not affect and did not interact with the effect of ES on any of the measured meat quality parameters. ES did not affect the ultimate pH in LD, BF, SM and SC or internal reflection value in LD. However, ES caused higher internal reflection and drip loss in BF and increased the PSE frequency in LD (2 to 7%) and in BF (2 to 49%). The frequency of PSE areas in the centre of SM was 70% for ES pigs compared to 9% for control pigs. ES and ageing improved the tenderness and reduced the hardness in LD as well as shear force of unaged BF. The effect of ES on tenderness and hardness was approximately half the effect of ageing, but the effect of ES and ageing were additive. ES significantly increased the activities of cathepsin B+L in the myofibrillar fraction, but there were no differences in proteolytic activity in the other fractions. It is concluded that ES improves tenderness in LD and BF, but has a negative effect on the quality of BF and SM. Therefore ES is not an economically attractive alternative for improvement of tenderness in LD compared to ageing in Danish pigs. ?     

Effect of lairage duration on rabbit welfare and meat quality

This study determined whether short (2 h) or long (8 h) lairage at an abattoir had an effect on plasma stress indicators (haematocrit, glucose, lactate, creatine phosphokinase and corticosterone), instrumental meat quality (pH24, water holding capacity, colour, raw and cooked texture) and sensory meat quality (using a trained sensory panel) in rabbits. The effect of the position of the animals on a multifloor rolling cage stand during lairage was also assessed. Lairage time had a significant effect on blood stress indicators, but only a slight effect on meat quality traits. A lairage duration of 6–8 h is recommended.     

Consumption of high energy maize diets is associated with increased soluble collagen in muscle of Holstein bulls

The aim was to investigate whether energy supplementation of gazing bulls can influence collagen concentration and solubility in three different muscles: longissimus dorsi (LD), semitendinosus (ST) and supraspinatus (SS). Thirty three Holstein bulls aged 15 months and reared on grass, were randomly assigned to three treatment groups for 85 days: fed grass ad libitum (G1-control); fed grass ad libitum and supplemented with 4 kg day^− 1 of ground maize (G2); fed grass ad libitum and supplemented with 8 kg day^− 1 of ground maize (G3). Total collagen content did not differ (P > 0.05) among treatments, however, soluble (heat-labile) collagen was significantly (P < 0.001) higher in meat from G3 (34%, 23% and 25% for LD, ST and SS, respectively), compared with G1-control (24%, 18% and 17% in LD, ST and SS, respectively). Overall, these results suggest that meat tenderness of grazing bulls may be improved by supplementing with ground maize (8 kg day^− 1).     

Use of infrared ocular thermography to assess physiological conditions of pigs prior to slaughter and predict pork quality variation

Infrared thermography (IRT) body temperature readings were taken in the ocular region of 258 pigs immediately before slaughter. Levels of lactate were measured in blood taken in the restrainer. Meat quality was assessed in the longissimus dorsi (LD), semimembranosus (SM), and adductor muscles. Ocular IRT (IROT) temperature was correlated with blood lactate levels (r = 0.20; P = 0.001), with pH taken 1 hour postmortem (pH1: r = − 0.18; P = 0.03) and drip loss (r = 0.20; P = 0.02) in the LD muscle, and with pH1 in the SM muscle (r = − 0.20; P = 0.02). Potentially, IROT may be a useful tool to assess the physiological conditions of pigs at slaughter and predict the variation of important meat quality traits. However, the magnitude of the correlations is rather low, so a further development of image capture technique and further studies under more variable preslaughter conditions ensuring a larger pork quality variation are needed.     

The impact of short-term feeding of magnesium supplements on the quality of pork packaged in modified atmosphere

This study compared the effect of dietary magnesium (Mg) supplementation on pork quality during 13 days of storage at 4 ± 1 °C under modified atmosphere. The experiment was conducted with 40 gilts (Pietrain × (Landrace × Large White)) which were fed one of four diets five days prior to slaughter: 1) control diet; 2) Mg oxide; 3) Mg sulphate; or 4) Mg chelate. Dietary Mg supplementation did not affect 24-h pH, colour, and Warner-Bratzler shear force values. Pork from pigs fed the Mg chelate‐supplemented diet had the lowest (P ≤ 0.05) drip, exudative, and cooking losses. Furthermore, pork from pig supplemented with Mg oxide had the lowest TBARS values. Visual assessment of pork from pigs supplemented with Mg chelate received higher colour and lower exudative scores, as well as overall acceptability scores, throughout display. Thus, Mg chelated supplementation could be effective in improving pork quality during 13 days of storage under modified atmosphere conditions.     

Effects of long distance transportation and CO2 stunning on critical blood values in pigs

The aim of the study was to evaluate the effect of two stressful stimuli, long transportation and 80% CO₂ stunning on metabolic-physiological variables, hemodynamic and gas exchange in slaughter pigs imported from the U.S. to Mexico City with a journey time of 27 h, with 8 h of lairage at the abattoir. A total of 589 pigs from three genders were monitored. Overall results show that both stimuli caused metabolic and physiological disturbance. Gilts were more efficient in controlling glycemia after a long transport journey (24 h), than castrated males (P < 0.05), whose glucose was increased above the 30 mg/dL basal level. Females on arrival had 23 mg/dL more lactate compared to basal levels (P < 0.05). Stunning caused more physiological effects compared to transportation. Regarding the gender factor, females and entire males were more susceptible to transport stress and stunning compared to the castrated pigs, and entire males showed more complications restoring the gas exchange compared to females and barrows.     

Effect of finishing and ageing time on quality attributes of loin from the meat of Holstein–Fresian cull cows

The effects of finishing time, (T0 = 0, T1 = 30 and T2 = 60 days), on Holstein–Friesian cull cows (n = 18) and post-mortem ageing, (1, 7, 14, 21, 35 and 42 days), under vacuum conditions of Longissimus thoracis (LT) muscles were investigated. The objective of this research was to study how finishing feeding (based on a commercial concentrate and corn silage), following a pasture period of 90 days, affected carcass and meat quality. Ageing time effect was also evaluated on the main quality attribute of added value pieces, such as “striploin of ox” from cull cows. Finishing treatment affected intramuscular fat content (IMF), moisture percentage, water-holding capacity (WHC), colour parameters and shear force of meat at 24 h post-mortem, whereas ageing time enhanced meat tenderness, when this was measured by two textural tests, Warner–Braztler (WB) and textural profile analysis (TPA). A minimum shear force was achieved at 7 and 14 days of ageing for T1 and T2, respectively. No differences (P > 0.05) could be found in colour parameters from 7 to 42 days. The results show that a finishing time of two months is very beneficial, due to the increase in meat fatness, improved overall carcass quality and luminosity (L*). Furthermore, 14 ageing days were sufficient to improved tenderness. Ageing time did not have an effect on lipid oxidation (P > 0.05) and this leads us to conclude that meat shelf life exceeded 42 days under vacuum conditions’.     

Combined effects of pre-slaughter treatments and lairage time on carcass and meat quality in pigs of different halothane genotype

The effect of two different lairage times on meat quality was investigated in pigs with different halothane genotype previously submitted to controlled pre-slaughter treatments. One hundred and ninety nine Italian heavy pigs were loaded by ramp or lift and transported unmixed for 1 h to the abattoir at a stocking density of either <0.4 or >0.6 m(2) per 100 kg pigs. After unloading, an equal number of animals within each previous treatment was held in lairage for 2 h or overnight (22 h) before slaughter. Carcass and meat quality and incidence of skin damage were evaluated. Longer lairage did not negatively affect carcass traits and reduced the incidence of PSE meat without increased DFD occurrence. It also seriously increased the amount of skin damage due to fighting, resulting in long fasting. Pre-slaughter treatments and halothane genotype showed a negligible effect on the response to the resting time.     

Effect of different electrical stimulation and chilling treatments on pork quality

The effect of different chilling and electrical stimulation (ES) treatments on the carcass and eating quality of pork has been examined. Preliminary trials (Study I), with a variety of ES treatments, indicated that, on the basis of pH fall, drip loss and tenderness, the most effective was that using 700 V peak at 12·5 Hz for 90 s applied at 20 min post-slaughter. These ES parameters were used throughout the main study (II) using 80 pigs, one side of which was stimulated and the other not, before being chilled rapidly (10°C in deep loin within 2–3 h of slaughter) or conventionally (10°C in deep loin within 5 h of slaughter).

Changes in pH and temperature during chilling were observed and, after chilling, quality assessments on LD and Sm muscles included drip loss, muscle opacity and instrumental toughness at 3 days post-slaughter.

Electrical stimulation, 20 min post-slaughter, improved tenderness of the LD and, to a lesser extent, the Sm of rapidly chilled pig sides. This advantage was gained without producing PSE pork. In fact, drip loss from the LD was consistently less from the sides which had been stimulated.     

A survey of pre-slaughter conditions, halothane gene frequency, and carcass and meat quality in five Spanish pig commercial abattoirs

A total of 116 deliveries, comprising 15,695 commercial pigs delivered to five abattoirs, were surveyed during winter and summer. Information about on-farm fasting, transport duration and stocking density, and lairage time was collected. Cortisol, creatine phospho-kinase (CPK), and lactate, and DNA for halothane genotype were analysed in a subsample of pigs at exsanguination in every journey. Electrical conductivity (PQM) in semimembranosus muscle (SM) and carcass characteristics (Fat-o-Meater and skin damage) were measured in each carcass. pHu of SM was analysed in the laboratory in a subsample in every journey. Carcasses were identified as PSE or DFD based on PQM and pHu, respectively. The n gene frequency ranged among abattoirs from 54 to 8%. Mean lean content was 58.9% for nn, 57.3% for Nn, and 55.8% for NN pigs, though a difference of 2.5% lean was observed between two abattoirs with the same n gene frequency. A straight relationship of the incidence of serious PSE carcasses and n gene frequency was found. The overall incidence of serious PSE and DFD carcasses was 6.5 and 12.5%, respectively. A higher incidence of PSE carcasses was found in summer; in deliveries with <12 h on-farm fasting; with transport stocking densities >0.40 m(2)/100 kg pig; and in transports of <2 h duration. A higher incidence of DFD carcasses was found in winter; with transport stocking densities <0.40 m(2)/100 kg pig; transports of >2 h duration; and lairage times >9 h. Cortisol level in blood increased in winter and decreased after 12-18 h fasting time. A rise in the lactate concentration was observed in pigs transported in high stocking density (<0.40 m(2)/100 kg pig) and for a longer time (>2 h). All blood stress indices increase as increasing lairage time. Carcasses with more skin damage had higher levels of cortisol, CPK and lactate, and higher incidence of DFD meat, compared with non and low skin damage carcasses.     

Effect of pre-slaughter management regarding transportation and time in lairage on certain stress parameters, carcass and meat quality characteristics in Kivircik lambs

Thirty Kivircik lambs were used to investigate effect of pre-slaughter treatment on certain haematological and biochemical parameters, carcass and meat quality characteristics. Lambs were divided into three treatments: 75 min transport and lairage for 18 h (TS-L18 h); 75 min transport and lairage for 30 min (TS-L30 min) and no pre-slaughter transport and lairage for 30 min (NTS). Treatment, as a main effect, did not influence haematological and biochemical parameters, but sampling time significantly affected these parameters, except total protein. Plasma cortisol concentration at exsanguination in TS-18 h, TS-30 min and NTS treatments were 117.34, 119.23 and 72.51 ng/ml, respectively. pH of longissimus dorsi muscle was higher in TS-L30 min than other treatments. TS-L30 min lambs had the highest shear force value, the lowest WHC and cooking loss. TS-L30 min treatment yielded the darkest meat immediately after cutting and 1 h later. Meat redness, yellowness and chroma values were similar in treatments.     

Enhancing pork loin quality attributes through genotype,chilling method and ageing time

The experiment was conducted to examine opportunities for enhancing pork quality through the use of post-mortem ageing when combined with different chilling regimes. Large White (LW, n = 24) and Duroc × Large White (Duroc, n = 24) barrows were slaughtered and alternate carcass sides were either conventionally or blast-chilled. The longissimus thoracis et lumborum muscle was dissected from the carcass sides (24 h post-mortem) and trimmed of cover fat. Three sections (15 cm length) were vacuum packaged and assigned to 2, 7 or 14 days of ageing (2 °C) randomized within muscle location. Blast-chilled meat had lower purge (P = 0.009) and drip (P = 0.0009) losses and higher hue (P = 0.02) than conventionally chilled meat. However chilling by conventional or blast-chilling methods had no effect on sensory characteristics (P > 0.1). When breeds were compared, meat from Duroc barrows had lower moisture (P < 0.0001) and higher intramuscular fat content (P < 0.0001), L∗ (P = 0.0003) and hue (P = 0.007) values than LW. Overall tenderness (P = 0.005), juiciness (P = 0.0007) and palatability (P < 0.0001), as well as flavour intensity (P < 0.0001) and desirability (P < 0.0001) values were higher and undesirable flavours were lower (P < 0.0001) for meat from Duroc pigs, when compared with LW. Ageing increased purge loss (P < 0.0001), L∗ (P < 0.0001), hue (P < 0.0001), chroma (P < 0.0001) and content of protein (P = 0.002), with corresponding decreases (P < 0.0001) in drip loss and moisture content. Instrumental (P < 0.0001) and sensory (initial, P < 0.0001 and overall, P < 0.0001) tenderness increased from day 2 to 14. Therefore independent of chilling method, ageing improved quality of pork loins. Moreover ageing had greater effect on tenderness, while breed had greater effect on flavour which may be related to differences in intramuscular fat content.     

Sensory,physical and chemical characteristics of cooked ham manufactured from rapidly chilled and earlier deboned M. semimembranosus

Effects of rapid chilling of carcasses (at − 31 °C in the first 3 h of chilling, and then at 2–4 °C) and earlier deboning (8 h post-mortem), compared to rapid (till 24 h post-mortem) and conventional chilling (at 2–4 °C, till 24 h post-mortem), on quality characteristics of pork M. semimebranosus and cooked ham were investigated. Quality measurements included pH value, colour (CIEL*a*b* values) and total aerobic count of M. semimebranosus, as well as sensory (colour, juiciness, texture, and flavour), physical (pH value, colour – CIEL*a*b* values and texture – Warner–Bratzler shear and penetration forces) and chemical (protein, total fat, and moisture content) characteristics of cooked ham. The cooked ham was manufactured from pieces of M. semimebranosus with ultimate lightness (CIEL* value) lower than 50. Rapid chilling and earlier deboning significantly increased quantity of M. semimebranosus desirable for cooked ham manufacturing. Earlier start of pork fabrication did not affect important quality characteristics of cooked ham.     

Potential interactions between the effects of preslaughter stress and post-mortem electrical stimulation of the carcasses on meat quality in pigs

The experiment examined the influence on pork quality of the electrical stimulation of carcasses from pigs subjected to different ante-mortem handling treatments. The carcasses were subjected to a slow chilling regimen to reflect less than ideal commercial practice. A total of 288 pigs (mean live weight 89 kg) of both sexes and a range of genotypes were used. They came from the Meat and Livestock Commission 's Pig Development Unit at Stotfold and were processed in 12 equal batches. Prior to slaughter they were transported for 2 h (80 km) at a stocking density of 0.5 m(2)/100 kg live weight. Preslaughter handling included being mixed or not with unfamiliar animals and being given a 3 h rest in lairage or not. One group received handling to simulate that in stunning races immediately before slaughter. There were no material interactions between the effects of ante- and post-mortem handling. Pigs rested 3 h in lairage had lower plasma cortisol levels irrespective of whether mixed with unfamiliar animals. Plasma lactate concentrations increased with greater ante-mortem stress. Pigs subjected to the simulated stunning race treatment had elevated carcass temperature. Greater ante-mortem stress progressively elevated pHu in the muscles and tended to reduce eating quality. Electrical stimulation followed by slow chilling raised initial muscle temperature, reduced pH(45) and pHu, and produced meat that was paler, had higher hue and saturation values and lost more drip during storage. Neither instrumentally-determined texture nor taste panel texture was affected, but electrical stimulation decreased juiciness and increased pork flavour. Overall eating quality was not affected by stimulation.     

A comparison of halothane homozygous negative and positive pietrain sire lines in relation to carcass and meat quality, and welfare traits

Barrows (n=164) and gilts (n=249) from crosses of a Pietrain homozygous halothane recessive (Pi nn) and two Pietrain homozygous dominant (Pi NN-a and Pi NN-b) sire lines with Landrace×Large White NN sows, were used to study the effect of terminal sire and pre-slaughter treatment on meat quality and animal welfare. The pigs from each of the two farms where they were finished were delivered to the abattoir in two batches differing in the pre-slaughter conditions. A total of 90 pigs (54 NN and 36 Nn) were assigned to a long pre-slaughter treatment (6 h transport and 14.5 h lairage) and 89 (57 NN and 33 Nn) to a short pre-slaughter treatment (4.5 h transport and 2.5 h lairage) in Farm 1, and 118 (65 NN and 53 Nn) to the long (7 h transport and 14 h lairage) and 114 (66 NN and 48 Nn) to the short pre-slaughter treatment (1.5 h transport and 2 h lairage) in Farm 2. In Farm 1, heart rate of 3 NN and 3 Nn gilts was recorded throughout loading and transport and blood samples from 5 NN and 5 Nn were collected before loading and after transport to measure cortisol, creatine phosphokinase (CPK) and lactate dehydrogenase (LDH). Carcasses were classified and commercial cutting was carried out. At 24 h, meat quality was assessed on the Longissimus thoracis muscle by measuring electrical conductivity (PQM), colour (Minolta CR 200 and Japanese scale), pHu and drip losses. Halothane carriers showed a higher mean heart rate and higher increase in CPK levels (P<0.05) after transport in the short pre-slaughter treatment than halothane free pigs. No effect was observed in cortisol or LDH values. Pi NN-a sired pigs had a higher live and carcass weight (P<0.001) and loin depth (P<0.05), but lower killing out percentage (P<0.01) and leg yield (P<0.01) compared with the progeny of the other two terminal sires. Gilts were leaner (P<0.001), had a higher killing out percentage (P<0.001) and higher yields of primal cuts (P<0.001) compared with barrows. Pi nn sired pigs had poorer meat quality (higher PQM values in both farms, P<0.01) than Pi NN-a sired pigs. Long pre-slaughter treatment resulted in darker meat (P<0.01) in both farms and in higher pHu (P<0.001) in Farm 1 than short pre-slaughter treatment. Conversely, pigs subjected to the short pre-slaughter treatment showed higher PQM values (P<0.01) in Farm 1 and higher PSE percentage (P<0.05) in both farms compared to the ones subjected to the long pre-slaughter treatment. These results suggest that Pietrain halothane free sire lines could produce similar results on carcass quality to halothane carriers, without compromising meat quality and welfare.     

Effect of antemortem feeding regimes on bacterial numbers in the stomachs and ceca of pigs

Three groups, each of 45 pigs, were either not fasted, fasted for 15 h during lairage at the abattoir, or fasted for 15 h before dispatch from the piggery to the abattoir. Three subgroups, each of 15 pigs from each group, were held at the abattoir for additional times of either 0 to 1 h, 2 to 3 h, or 4 to 5 h. Immediately after slaughter, stomach and cecal contents were collected for pH measurement and enumeration of coliforms, Escherichia coli biotype 1 and lactic acid bacteria (LAB). Stomach pH changed from 4.1 to 3.1 as additional abattoir holding time increased from 0 to 1 h to 4 to 5 h but was unaffected by feed withdrawal (mean pH, 3.5). Cecal pH (range 6.4 to 7.2) increased in response to both treatments. Coliform and E. coli biotype 1 numbers in the stomach, means 4.6 and 4.5 log CFU/g, respectively, were not affected by feed withdrawal but decreased 0.8 log units as additional abattoir holding time increased from 0 to 1 to 4 to 5 h. LAB in the stomach decreased in response to both feed withdrawal and holding at the abattoir. Cecal numbers of coliforms and E. coli biotype 1 increased 0.8 and 1.0 log units to 7.8 and 7.6 log CFU/g, respectively, as a result of feed withdrawal, and 0.6 log units to 7.6 and 7.5 log CFU/g, respectively, as additional abattoir holding time increased to 4 to 5 h. The LAB in the cecum (mean 9.4 log CFU/g) increased slightly with increasing abattoir holding time. In the event of release of stomach or cecal contents onto the meat during carcass dressing, larger numbers of E. coli per g would be released from the ceca and fewer per g from the stomachs of pigs that have had feed withdrawn as compared to pigs not subjected to feed withdrawal.