Nn Pigs Research Articles

The effect of genotype on feedlot performance, carcass composition, and lean meat quality from commercial pigs

A total of 60 female and 54 castrated male progeny of commercial Landrace × Large White F1 sows, backcrossed to Landrace or Large White boars, were slaughtered at an average liveweight of 102 kg. Four same-sex pigs were penned together. Large White sires were homozygous normal (NN) but Landrace sires were heterozygous carriers (Nn), at the halothane locus. Progeny genotypes at the halothane locus were determined by a DNA probe. Barrows grew 136 g d−1 faster (P < 0.0001), reaching market weight 13 d sooner (P < 0.0001) but with 3.2 mm more average back-fat (P < 0.0001) than gilts. Both sexes had similar feed requirements (P = 0.1221). Landrace and Large White-sired pigs had similar growth rate (P = 0.6458) and feed requirements (P = 0.9354), but Large White-sired pigs had 1.33 mm less grade fat thickness (P = 0.0131) and 1.72 more muscle depth (P = 0.0218) than Landrace-sired pigs. Nn pigs required 7 d longer (P < 0.0001) and 22 kg (P = 0.0393) more total feed to reach market weight than NN pigs, but they had 2.6 mm greater muscle depth (P = 0.0008) and had 1% greater commercial lean yield (P = 0.0291). However, meat quality of Nn pigs was reduced when compared with NN pigs. For example, colour reflectance and drip loss were higher (P < 0.0001) and soluble protein was lower (P < 0.0001) among the Nn pigs which also had less intrasmuscular fat (P = 0.0184). The results emphasize that the increased value of the carcass from Nn pigs may be offset by reduced feedlot performance and reduced meat quality, and questions the merit of the use of halothane gene to improve production efficiency in the commercial market. Key words: Swine production, halothane gene, breed effect, Landrace, Large White

The effect of dietary protein source on biochemical indices of stress in stress-susceptible pigs

The porcine stress syndrome (PSS) is responsible for major economic losses to the swine industry. The present study was performed to determine if 8-wk-old pigs representing each of three genotypes (NN = homozygous noncarrier, Nn = heterozygous carrier, nn = homozygous carrier) with respect to the PSS, differ in selected biochemical indices related to stress (exp. 1), and to examine if these indices are affected during 5 wk of dietary adaptation to a cereal-based swine diet (control diet) or to a feed containing casein, a higher quality protein (exp. 2). The first experiment demonstrated that nn and Nn 8-wk-old female pigs have a significantly greater glycemic response to a blood sampling stressor than do NN female pigs. In contrast, no genotype differences in glycemic response were observed within young male pigs. Pigs of nn genotype also demonstrated a significantly greater plasma dopamine-β-hydroxylase (DBH) activity than did the NN pigs. Results of the second experiment revealed that pigs of the nn and Nn genotypes experienced a greater glycemic response to the initial blood sampling stressor than did the NN pigs. Compared with initial levels, upon the sixth weekly blood sampling stressor the nn and Nn pigs experienced reduced plasma glucose concentration irrespective of diet, while no change in glycemic response was observed in the pigs of the NN genotype. Finally, the DBH activity of the Nn pigs adapted for 2 wk to the casein diet was found to be reduced when compared to control-adapted Nn pigs. This study suggests that in addition to genotype differences, regular exposure to stress combined with dietary adaptation to feed containing a higher quality protein (casein) may confer increased resistance to stress in pigs of the Nn genotype. Key words: Pigs, stress, dietary protein, glycemia, dopamine-β-hydroxylase

Effect of halothane genotype, breed, feed withdrawal, and lairage on pork quality of belgian slaughter pigs.

A total of 434 Belgian Landrace (B) or Piétrain x B (PB) pigs, of known halothane genotype (NN, Nn, and nn), were slaughtered in a commercial abattoir. Pigs were either fed until loading or deprived of food overnight before delivery. Upon arrival at the abattoir, pigs were slaughtered after different lairage times (within 1 h after arrival, after 2 to 3 h lairage, or 4 to 5 h lairage). Meat quality traits were measured on the carcass, as well as on a piece of loin. Halothane genotype was the predominant factor determining meat quality traits related to the PSE condition (P < .001 for pH 40 min after death, internal reflectance, color L value; P < .01 for drip losses, transmission value). For these traits, nn pigs were always significantly different from Nn and NN pigs. Depending on the specific trait, Nn pigs were intermediate between NN and nn pigs, or close to NN pigs. For pH 40 min after death and drip losses, Nn and NN pigs were significantly different, whereas the difference between Nn and NN pigs was not significant for internal reflectance, color L value, and transmission value. Shear force and intramuscular fat content were apparently not related to the PSE condition and were not influenced by the halothane genotype (P > .05). Differences in meat quality between B and PB pigs and between gilts and barrows were rather unimportant compared with the effect of halothane genotype. Overnight feed withdrawal had no effect on meat quality (P > .05 for all PSE-related traits). On the other hand, holding pigs a few hours in lairage improved meat quality compared with immediate slaughtering (P < .05 for pH and temperature in the loin 40 min after death, internal reflectance, color L value, transmission value, drip losses). This effect was more pronounced in stress-susceptible pigs than in stress-resistant pigs.

The effects of selection for lean growth and the halothane allele on carcass and meat quality of pigs transported long and short distances to slaughter

Carcass and lean quality traits were studied in two genetic lines of pigs in which the halothane allele n was segregating with the normal allele N. One line had been selected for high growth rate and low backfat depth and the other line maintained as an unselected control. Pigs of the three segregants NN, Nn and nn from both lines were grown at two locations, one near the abattoir (1 h by road) and the other far (10 h) from the same abattoir. Pigs from both locations were fasted for 20 h before slaughter. Relative to control line pigs, those from the selected line had lower backfat depths, greater ham weights, eye muscle areas and carcass lengths but lower dressing percentages. The n allele had little effect on carcass traits but for lean quality traits, the n allele acted additively to increase acidity, paleness, water lost through drip, centrifugation and cooking and to reduce cured yield. Independently of the n allele, selection for lean growth increased the incidence of dark, firm and dry (DFD) pork. This was highest in carcasses of NN pigs from the selected line grown far from the abattoir. nn pigs from the control line grown near the abattoir produced the most pale, soft, exudative (PSE) pork.

Variations in meat quality in live halothane heterozygotes identified by biopsy samples of M. longissimus dorsi

The meat quality of halothane heterozygotes ( Nn) was investigated using British Landrace ( n = 18) and Landrace × Large White pigs ( n = 67). Normal and PSE meat were identified in both breeds using M. longissimus dorsi (LD). In Landrace × Large White Nn pigs, the potential meat quality identified using small biopsy LD samples (500 mg) showed a wide spectrum in water-holding capacity (WHC), ranging from normal (43%) to PSE (57%). Predictions of meat quality in live pigs were confirmed from post-mortem assessments of LD samples based on pH 1 and fibre optic probe measurements. Our results show that Nn pigs have the propensity to produce a higher proportion of PSE than normal carcasses. The predictive meat quality test performed on small biopsy LD samples offers an opportunity not currently available to the pig industry, to select Nn pigs with the potential to produce pork of superior WHC.

Effect of dietary supplementation of vitamin E on pig meat quality

The effect of vitamin E on pig meat quality was investigated using British Landrace (NN and nn), Landrace × Large White (NN and Nn) and Pietrain (nn) pigs. Daily dietary supplementation of 500 mg vitamin E/kg diet for 46 days could reduce drip loss in unfrozen longissimus thoracis (LT) by 45% and 54% in Nn and NN pigs, respectively. In PSE-prone Landrace × Large White Nn pigs, daily supplementation of 1000 mg vitamin E/kg diet for the same period could significantly ( P < 0.001) reduce excess release of Ca 2+ and prevent the formation of PSE carcasses, evaluated from both biopsy and post- mortem LT samples. Experimental evidence from erythrocyte fragility and water-holding capacity of biopsy LT samples suggested that vitamin E improved pig meat quality by its ability to stabilize membranes. Stabilization of membrane integrity in isolated mitochondria of LT by vitamin E was associated with inhibition of phospholipase A 2 activity.

Muscle glycogen level and meat quality in pigs of different halothane genotypes

The halothane genotype of 22 Polish landrace pigs was determined using halothane test and blood typing. Eight homozygous normal (NN), eight hetero-zygotes (Nn) and six homozygous recessive (nn) were identified. The levels of glycogen and lactate were measured in biopsy samples taken from the longissimus lumborum using a shot biopsy technique. pH (pH 1) and IMP/ATP ratio (R) were determined at 30 min after slaughter, while pH, meat colour and water holding capacity were determined on the day after slaughter. The halothane genotype did not affect intra vitam glycogen level. The nn pigs had a higher R value and lower pH 1 than both Nn and NN animals. Heterozygous animals were intermediate between both homo-zygotes for biopsy lactate level and meat colour. The lactate content of biopsy samples was significantly correlated with pH 1 ( r = −0·68; P < 0·01), R ( r = 0·68; P < 0·01), meat colour ( r = 0·57; P < 0·01) and water holding capacity ( r = 0·45; P · 0·05).

The effect of mixing, feed restriction and genotype with respect to stress susceptibility on pork carcass and meat quality

The effects of genotype for stress susceptibility with respect to the halothane gene (PSS genotype: NN = homozygous normal, Nn = heterozygous, nn = homozygous recessive), in combination with fasting and mixing during the 24 h prior to shipping for slaughter upon the carcass traits and quality of the longissimus muscle were investigated using a total of 229 pigs. In comparison to pigs of the NN genotype, pigs of the nn genotype had higher warm carcass yield, cold carcass yield, yield of the major cuts and lean yield of the major cuts by 47, 39, 5 and 15 g kg−1, respectively. Pigs of the Nn genotype had 30 and 8 g kg−1 higher warm carcass yield and yield of major cuts, respectively, than did NN pigs. Pigs of the nn genotype had 178 g kg−1 and pigs of the Nn genotype had 66 g kg−1 more total lean in the major cuts than NN pigs but these differences were not detected by the carcass grading system. Mixing and fasting both caused live-animal weight losses and reduction of warm carcass yield. Fasting had the greater influence, decreasing live animal weight by 54 g kg−1 and the warm carcass yield by 12 g kg−1 in comparison to the unmixed, unfasted pigs. Combined fasting and mixing for 24 h decreased live animal weight by 62 g kg−1 and the warm carcass yield by 19 g kg−1 in comparison to the unmixed, unfasted pigs. Pigs of both nn and Nn genotypes produced poorer muscle quality than did those of the NN genotype. Fasting of pigs for 24 h pre-slaughter alleviated the PSE problem to a small extent. Mixing, with or without fasting, improved muscle quality of pigs of the Nn and nn genotypes. However, such gains in meat quality due to mixing and/or fasting are negated by the decreases in the carcass yield, by the additional carcass damage due to fighting and finally by their possible detriment to animal welfare. Key words: Mixing, fasting, halothane genotype, carcass, pork quality, pigs

Identification of halothane genotypes by calcium accumulation and their meat quality using live pigs

The three halothane genotypes (NN, Nn, and nm) were identified by measuring the capacity for Ca 2+ accumulation by sarcoplasmic reticulum in whole muscle homogenate preparations of M. longissimus dorsi with a Ca 2+ specific electrode at 35°C. Significant differences ( P < 0·001) in deterioration (%) of Ca 2+ accumulation, 12% for NN, 35% for Nn, and 81% for nn pigs, were observed after ageing the whole muscle homogenate preparations for 24 h in ice. Predictions of meat quality in live pigs ( n = 34) based on the values for water-holding capacity, assessed as fluid (g/0·5 g wet wt LD), and pH (fluid) by using small biopsy LD samples (Cheah et al. 1993) were performed on all the halothane genotypes. The halothane genotype NN ( n = 11) showed a fluid value of 0·37 ± 0·01 and a pH (fluid) value of 6·62 ± 0·03 as compared with 0·61 ± 0·02 and 5·84 ± 0·04, respectively, for the halothane genotype nn ( n = 13). The Nn pigs ( n = 10) showed fluid (0·49 ± 0·03) and pH (fluid) (6·19 ± 0·11) values between those values observed for the two homozygotes (NN and nn). Predictions of meat quality in live pigs from biopsy LD muscles were confirmed from assessments on post-mortem LD muscles based on pH 1 and fibre optic probe (FOP) measurements. The extent of deterioration (%) in Ca 2+ accumulation showed high correlations with fluid ( r = −0·861) and pH (fluid) ( r = −0·831) in the biopsy LD samples, and with pH 1 ( r = 0·663), FOP ( r = −0·812), and drip (%) loss ( r = −0·777) in the post-mortem LD samples.

Pork quality and the expression of stress protein Hsp 70 in swine

The expression of heat shock protein with a molecular weight of 70 kDa (Hsp 70) in porcine tissue and its potential relationship to stress susceptibility was studied. Twelve pigs, four of each genotype (NN, Nn, and nn) for halothane sensitivity were slaughtered. At 45 min postmortem, several tissues (liver, kidney, spleen, skeletal and cardiac muscle, and adrenal gland) were sampled for Hsp 70 analysis. At 24 h postmortem, longissimus and semimembranosus muscle were sampled for assessment of meat quality. Water-holding and water-binding capacity, color, and protein denaturation of samples from halothane-positive animals indicated that these animals had been stressed. Homozygous nn pigs demonstrated a lower pH45 and higher L-value at 48 h than their NN and Nn counterparts (P < .05). The longissimus, but not semimembranosus, muscle of nn pigs demonstrated lower water-holding capacity and greater protein denaturation than that of NN or Nn pigs (P < .05). The water-binding capacity of both longissimus and semimembranosus was less in nn than in Nn or NN pork (P < .05). Using one-dimensional PAGE and Western blotting, Hsp 70 was shown to be present in all tissues examined. With two-dimensional PAGE followed by blotting, the presence of the cognate and inducible form of Hsp 70 was investigated. There did not seem to be a relationship between stress (based on meat quality) and expression of either form of Hsp 70.

The effect of the malignant hyperthermia genotype as determined by a restriction endonuclease assay on carcass characteristics of commercial crossbred pigs

In 349 crossbred pigs a restriction endonuclease assay used to detect the malignant hyperthermia genotype determined the presence of 84.5% NN pigs, 14.9% Nn pigs and 0.6% nn pigs. A subsample of 149 pigs demonstrated that Nn pigs had a 1% advantage in carcass yield over NN pigs and that meat color was not affected by genotype. Key words: Pigs, carcass, meat, halothane, restriction endonuclease

The effect of the halothane gene on pork production and meat quality of pigs reared under commercial conditions

Production and meat quality traits were evaluated on 74 commercially raised heterozygous pigs (Nn) and 50 homozygous normal pigs (NN) at the halothane locus, with an average carcass weight of 79.7 kg. Eight-week weight, average daily gain and age to market, as well as measures of carcass quality (i.e., dressing percent, grade site fat and muscle depths and predicted lean yield) did not differ among pigs with Nn and NN genotypes. The longissimus dorsi muscle from Nn and NN pigs had similar subjective colour and structure scores. Reflectance meter readings (CIE L*-values) were significantly higher on chops from Nn than from NN pigs taken from the centre (57.4 vs. 55.6) and from the anterior portion (56.2 vs. 54.5) of the loin. Drip loss among Nn pigs was higher than among NN pigs for chops taken from the centre (4.8 vs. 3.8 g 100 g−1) and from the anterior portion (3.7 vs. 2.9 g 100 g−1) of the loin (P &lt; 0.01). Soluble protein was 1.7% lower (P &lt; 0.001) in Nn pigs compared with the NN pigs. Barrows attained market weight earlier (P &lt; 0.05) than gilts, but they had a lower dressing percentage (P &lt; 0.05) and greater grade fat depth (P &lt; 0.001) and had 1.2% less predicted lean yield of carcass (P &lt; 0.001) than gilts. Since meat quality declined without concomitant increases in growth rate or improvements in carcass quality, it was concluded that the intentional use of the halothane gene should be discouraged. Key words: Swine, production, carcass quality, meat quality, halothane gene

Growth characteristics and carcass composition of pigs with known genotypes for stress susceptibility over a weight range of 70 to 120 Kg

ABSTRACTA total of 805 Lacombe pigs of different genotype with respect to halothane sensitivity (halothane positive, nn = 205; heterozygote, Nn = 214; halothane negative, NN = 386) were slaughtered over a range in live weight (70 to 120 kg) to assess tissue growth patterns using the allometric equation (y = aXh). The nn genotype was older at slaughter than the NN genotype, but pigs from each genotype were killed over a similar weight range. The relative growth of the primal cuts was influenced by genotype, with nn pigs having a lower coefficient for the bottom shoulder (picnic) and a higher coefficient for the belly. The relative growth of bone was similar for genotypes (P &gt; 0·05) but the relative growth of lean was lower and the relative growth of total fat and depot fat (subcutaneous and intermuscular) was higher for the nn genotype compared with the Nn and NN genotypes. On a within-tissue basis, the relative growth of the tissues in each primal was similar, except for the ham, where the relative growth of lean was higher for nn pigs compared with the two other genotypes. Small differences in tissue distribution were evident, but seldom exceeded 30 g/kg. Although nn pigs had a higher lean content and higher lean: bone ratio than Nn or NN pigs at similar live weights, their relative advantage in composition decreased with increasing live weight.

A within-litter comparison of the three halothane genotypes. 2. Performance, carcass quality, organ development and long-term effects of transportation and amperozide

The aim of the investigation was: (1) to compare the three Hal genotypes with respect to performance, carcass quality and organ development at slaughter, (2) to study long-lasting effects of transportation and treatment with amperozide. The study comprised 120 (23 NN, 69 Nn and 28 nn) crossbred pigs, offspring of heterozygous boars and sows. The Hal genotype was revealed by combining the halothane test and blood typing. At an average age of 12 weeks, the pigs were subjected to one of four treatments (with and without transport × with and without amperozide treatment). The pigs were kept in groups of four pigs ( 1 NN, 2 Nn and 1 nn) originating from different litters and were fed individually. Four nn pigs died during the experiment, one owing to fighting on the first day and three on the way to the slaughter house. The nn pigs had higher daily weight gain and lower feed to gain ratio than the NN and Nn animals. Carcass lean content was higher, but meat colour paler for the nn compared with the NN and Nn pigs. The heterozygotes were intermediate to the homozygotes for carcass lean content and meat colour. Organ weights were lower for the nn compared with the NN animals, and those of the Nn pigs were intermediate or close to the NN animals. Pigs subjected to a 5-h transport at 12 weeks had lower carcass lean content than non-transported ones. Amperozide treatment at the same age resulted in increased crude fat content of the liver at slaughter 3 months later. Adrenal weight at slaughter was higher for the amperozide-treated but nontransported animals compared with the other three treatment groups.

A within-litter comparison of the three halothane genotypes. 1. Piglet performance and effects of transportation and amperozide treatment at 12 weeks of age

The aim of the investigation was to compare the three Hal genotypes within litter, with respect to: (1) piglet performance; (2) effects on agonistic behaviour and weight gain of transport and amperozide treatment at 12 weeks of age. The animals were offspring of heterozygous boars and sows, and the Hal genotype was revealed by the halothane test combined with blood typing. One hundred and twenty pigs, kept in groups of four (1 NN, 2 Nn and 1 nn from different litters), were allotted to the four treatments in an experiment with a 2 × 2 factorial design: with and without transport (5 h) × with and without amperozide treatment. Each transport treatment comprised 15 pens and the animals in seven of these were treated with amperozide. Piglet weight at birth and at 9 weeks did not differ between the Hal genotypes. Amperozide treatment decreased the agonistic behaviour, but the effects on weight gain were inconsistent. Overall, daily weight gain in the first 13 days after the transport/amperozide treatments did not differ, neither between treatment groups nor between Hal genotypes, but interactions between Hal genotype, sex and amperozide treatment were found. Gilts attacked more than castrates, and interactions between Hal genotype and sex were indicated for agonistic behaviour. Creatine kinase (CK) activity was higher in nn compared with NN and Nn pigs. Transport increased the CK activity.

BODY PROPORTIONS AND CARCASS COMPOSITION OF PIGS WITH KNOWN GENOTYPES FOR STRESS SUSCEPTIBILITY FASTED FOR DIFFERENT PERIODS OF TIME PRIOR TO SLAUGHTER

A total of 233 pigs from a halothane positive line (genotype nn), from a halothane-negative line (genotype NN) and their cross (genotype Nn) were allocated to three treatments when their liveweight approximated 95 kg. Treatment 1 consisted of immediate slaughter following removal of the pigs from their pens, treatment 2 involved a period of 24 h of feed restriction prior to slaughter and treatment 3 a period of 48 h of feed restriction prior to slaughter. All carcasses were weighed on the slaughter floor and cooled at 1 °C for 24 h prior to dissection of the side into fat, lean and bone. Relative to liveweight, nn pigs had a higher proportion of carcass (41 g kg−1, P &lt; 0.001) and a lower proportion of body organs (8 g kg−1, P &lt; 0.001), body fat depots (7 g kg−1, P &lt; 0.001), alimentary tract (14 g kg−1, P &lt; 0.001) and gutfill (12 g kg−1, P &lt; 0.001) than NN pigs. Nn pigs had values that were generally intermediate to nn and NN pigs. The proportion of carcass (22 g kg−1), body organs (5 g kg−1), alimentary tract (6 g kg−1) and gutfill (21 g kg−1) were reduced (P &lt; 0.05) as fasting increased from 0 to 48 h relative to market weight. Linear fat thickness measurements made on the midline of the warm carcass were similar for nn and NN pigs except for the maximum loin (32.2 vs 28.6 mm for nn vs. NN). However, nn pigs had a lower proportion (P &lt; 0.05) of fat (35 g kg−1), bone (13 g kg−1) and skin (11 g kg−1), and a higher proportion of lean (60 g kg−1) in their carcasses than those from NN pigs. Carcasses from Nn pigs had less skin (4 g kg−1) and bone (7 g kg−1), but more lean (11 g kg−1) and similar fat content to those from NN pigs. It was concluded that fasting for up to 48 h prior to slaughter had a similar effect on the three genotypes, but there were large differences among genotypes in body components and carcass composition. Key words: Stress susceptibility, fasting, carcass, organs, gutfill, composition, pigs

Effects of transport stress on concentrations of cortisol, corticosteroid-binding globulin and glucocorticoid receptors in pigs with different halothane genotypes.

Effects of stress on concentrations of cortisol and corticosteroid-binding globulin (CBG) in blood plasma and on glucocorticoid receptor concentrations in muscle cytosol were studied in pigs representing three Halothane (Hal) genotypes (NN, Nn, nn). At 12 wk of age, animals were divided into four groups: pigs subjected to transport (5 h in a truck), pigs treated with amperozide prior to transport, pigs not transported but treated with amperozide and pigs neither transported nor given amperozide. Animals were slaughtered the week they reached 100 kg live weight (3 mo later). The Hal gene showed no major influence on the variables studied except for cortisol concentrations (P = .06) measured directly after transport at 12 wk of age (NN = 66.8 nM, Nn = 61.4 nM, nn = 69.4 nM). However, the response in each Hal genotype differed, depending on whether or not the pigs had been exposed to transport. Two weeks after transport, NN pigs developed higher cortisol concentrations than untransported animals, whereas the response was reversed in nn animals; Nn pigs showed no difference in this regard. At slaughter, the effect of transport (12 wk of age) on cortisol and CBG was still apparent. In NN pigs cortisol and CBG concentrations were elevated (P less than or equal to .05, P = .08, respectively), whereas concentrations tended to be lower in nn pigs (P = .17, P = .07, respectively) when compared with untransported pigs. Transported pigs had lower receptor concentrations at slaughter (P less than or equal to .01) than untransported pigs. However, pigs given amperozide in connection with transport had a receptor concentration comparable to that in untransported pigs. Our study shows conclusively that transport stress had long-term effects on cortisol, CBG and glucocorticoid receptor concentrations. In addition, amperozide had long-term effects on cortisol and receptor concentrations.

Influence of the Hal locus and standardized stress on antibody response and in vitro reactivity of peripheral blood lymphocytes in pigs

The antibody response to two Escherichia coli antigens (0149 and K88) and the in vitro reactivity of peripheral blood lymphocytes (PBLs) to pokeweed mitogen was studied in growing pigs after exposure to varying degrees of stress. Three experimental groups were used; transportation by lorry, transportation by lorry after a previous injection of a tranquillizing drug (amperozide), no transportation but an amperozide injection. Another group was used as a control group. This group was not transported and received no amperozide injection. The animals were the offspring of boars and sows heterozygous ( Nn) for the Hal gene, and all 3 Hal genotypes ( NN, Nn, nn) were identified and could thus be compared within litters. Immediately after the experimental treatment, the highest PBL reactivity was found for the amperozide-treated animals and for the non-transported animals, with no differences in reactivity between Hal genotypes. Two weeks later, the treatments caused different effects on pigs of the 3 Hal genotypes, both with regard to the PBL reactivity and the IgG response to 0149. The NN pigs had a higher PBL reactivity than the nn pigs for all treatments except the ‘drug + transport’ class where the reverse rank order was found. The NN pigs also had a higher IgG response to 0149 than the nn pigs in the ‘drug + no transport’ class. The amperozide treatment was followed by a higher PBL reactivity in non-transported NN pigs and in transported nn pigs. The amperozide-treated non-transported NN pigs also had a higher IgG response to 0149. The highest PBL reactivity and IgG response to 0149 were found mainly in pigs with the lowest cortisol levels. Pronounced differences between litters were found for both the antibody response and the PBL reactivity.