Selection of SNP from 50K and 777K arrays to predict breed of origin in cattle.

Reliable breed assignment can be performed with SNP. Currently, high density SNP chips are available with large numbers of SNP from which the most informative SNP can be selected for breed assignment. Several methods have been published to select the most informative SNP to distinguish among breeds. In this study, we evaluated Delta, Wright's FST, and Weir and Cockerham's FST, and extended these methods by adding a rule to avoid selection of sets of SNP in high linkage disequilibrium (LD) providing the same information. The SNP that had a r2 value>0.3 with any of the SNP already selected were discarded. The different selection methods were evaluated for both the 50K SNP and 777K Bovine BeadChip. Animals from 4 cattle breeds (989 Holstein Friesian, 97 Groningen White headed, 137 Meuse-Rhine-Yssel, and 64 Dutch Friesian) were genotyped. After editing 30,447 and 452,525 SNP were available for the 50K and 777K SNP chip, respectively. All selection methods showed that only a small set of SNP is needed to differentiate among the 4 Dutch cattle breeds, whereas comparison of the selection methods showed only small differences. In general, the 777K performed marginally better than the 50K BeadChip, especially at higher confidence thresholds. The rule to avoid selection of SNP in high LD reduced the required number of SNP to achieve correct breed assignment. The Global Weir and Cockerham's FST performed marginally better than other selection methods. There was little overlap in the SNP selected from the 2 BeadChips, whereas the number of SNP selected was about the same.

Longissimus muscle transcriptome profiles related to carcass and meat quality traits in fresh meat Pietrain carcasses.

High quality pork is consumed as fresh meat, whereas other carcasses are used in the processing industry. Meat quality is determined measuring technical muscle variables. The objective of this research was to investigate the molecular regulatory mechanisms underlying meat quality differences of pork originating from genetically different Piétrain boars. Piétrain boars were approved for high meat quality using a DNA marker panel. Other Piétrain boars were indicated as average. Both groups produced litters in similar Piétrain sows. The LM were sampled from 9 carcasses produced by approved boars and 8 carcasses of average boars. Total RNA was isolated, and an equal portion of each sample was pooled to make a reference sample representing the mean of all samples. Each sample was hybridized on microarrays against the reference in duplicate using a dye swaps design. After normalization and subtraction of 2 times the background, only genes expressed in at least 5 carcasses were analyzed. For all analyses the mean of the M-values relative to the reference (i.e., fold change), were used. Sixteen genes showed significant linear or quadratic associations between gene expression and meat color (Minolta a* value, Minolta L* value, reflection, pH 24 h) after Bonferroni correction. All these genes had expression levels similar to the reference in all carcasses. Studying association between gene expression levels and meat quality using only genes with expression statistically differing from the reference in at least 5 carcasses revealed 29 more genes associating with the technological meat quality variables, again with meat color as a main trait. These associations were not significant after Bonferroni correction and explained less of the phenotypic variation in the traits. Bioinformatics analyses with The Database for Annotation, Visualization and Integrated Discovery (DAVID) using the list of genes with more than 2-fold changed expression level revealed that these genes were mainly found in muscle-specific processes, protein complexes, and oxygen transport, and located to muscle-specific cellular localizations. Pathway analysis using the Kyoto Encyclopedia of Genes and Genomes (KEGG) database revealed pathways related to protein metabolism, cellular proliferation, signaling, and adipose development differing between the 2 groups of carcasses. Approved meat carcasses showed less variation in gene expression. The results highlight biological molecular mechanisms underlying the differences between the high meat quality approved and average boars.

Effects of Butafosfan on salivary cortisol and behavioral response to social stress in piglets.

We assessed the efficacy of Butafosfan, a component of Catosal, in the metaphylactic treatment of stress in pigs. Four 6-week-old female littermates were taken from 12 litters. They were confronted with a pig from a different litter for 2 h. There were 24 pairs, each consisting of confronting two unfamiliar pigs in a new pen. This housing of unfamiliar pigs provides a good, but simple, model of the psychosocial stress that pigs experience when housed in large groups on pig farms. Immediately before being housed with an unfamiliar pig, 12 pairs of pigs were injected subcutaneously with Catosal at a dose equivalent to 20 mg Butafosfan per kg body weight; the other 12 pairs received the control solution containing all ingredients of Catosal except Butafosfan. The frequency and duration of aggressive behavior and the salivary cortisol response were measured during the first 2 h of the encounter. No adverse effects associated with Catosal were observed. Subcutaneous injection of Catosal reduced the stress-induced salivary cortisol response and the frequency of aggressive behavior evoked by the social stress of housing two unfamiliar pigs together.

Perspective of NIRS measurements early post mortem for prediction of pork quality.

The potential of near-infrared spectroscopy (NIRS) measurements early post mortem was investigated to predict ultimate drip loss, colour, tenderness and intra-muscular fat of pork. Three locations (M. longissimus thoracis, M. longissimus lumborum and M. semimembranosus) in 102 pig carcasses were tested at the end of the slaughter line. A priori variation in pork quality was introduced using an experimental design covering: genotype, lairage time, pre-slaughter handling and day of slaughter. At 1 h post mortem a diode array VIS/NIR instrument (Zeiss MCS 511/522, 380-1700 nm) equipped with a surface fibre optic probe was used and at 1 day post mortem ultimate pH, drip loss, colour and shear force was measured on similar locations. Results indicated that it was possible to predict intra-muscular fat content (correlation (R(2) of 0.35 with multiple linear regression), standard error of prediction (SEP)=3.6 g/kg), but the configuration has to be refined for on-line application (bigger aperture). For drip loss no correlation was achieved with the PLS method. Even extremes (low drip loss (<2.5%) or high drip loss (>4.5%)) in drip loss were not discriminated. Predicting drip loss with NIRS early post mortem is not successful, although NIRS in the slaughter line has potential as a fast predictor of intra-muscular fat. Possibilities for using the NIRS technique to get to know more about muscle metabolism and post mortem changes are promising.

Relationships between behavioral and meat quality characteristics of pigs raised under barren and enriched housing conditions.

In this study the effects of barren vs enriched housing conditions of pigs on their behavior during the lairage period (2-h holding period before slaughter), carcass characteristics, postmortem muscle metabolism, and meat quality were studied. The barren housing system was defined by common intensive housing conditions (i.e., with slatted floors and recommended space allowances), whereas the enriched environment incorporated extra space and straw for manipulation. Salivary cortisol concentrations were measured before transport and at the end of the lairage period. During the lairage period the percentage of time spent walking and fighting by the pigs was registered. Carcass characteristics such as weight, meat percentage, and backfat thickness were determined. At 5 min, 45 min, 4 h, and 24 h postmortem, pH, temperature, and lactate concentrations were determined in the longissimus lumborum (LL) and biceps femoris (BF) muscles. Capillarization of the muscle, mean muscle fiber area, and color and drip loss after 2 and 5 d of storage were determined for both muscle types. Pigs from the barren environment had a significantly higher increase in cortisol from farm to slaughter, but no differences in behavior were observed during the lairage period. Carcass characteristics did not differ between pigs from barren and those from enriched housing conditions. Postmortem lactate formation was significantly lower in LL muscles of enriched pigs at 4 and 24 h postmortem. Capillary density and mean muscle fiber area did not differ between the groups of pigs. The percentage of drip loss at 2 and 5 d after storage of LL muscle samples from enriched-housed pigs was significantly lower than that of the barren-housed pigs. Similar tendencies were found for the BF muscle from pigs kept in an enriched environment, but these were not statistically significant. The housing system did not affect meat color. It is concluded that on-farm improvement of animal welfare by environmental enrichment can also lead to beneficial economic effects after slaughter by improving the water-holding capacity of pork.

Effects of rate of pH fall, time of deboning, aging period, and their interaction on veal quality characteristics.

Three groups of veal carcasses were selected on the basis of their pH in the longissimus lumborum muscle at 3 h postmortem (pH3) to study the effects and interaction with time of deboning on quality characteristics of veal. The following groups of 10 calves each were selected: 1) fast pH fall, pH3 < 6.2; 2) intermediate pH fall, 6.2 < pH3 < 6.7; and 3) slow pH fall, pH3 > 6.7. Longissimus thoracis et lumborum (LTL) muscles of sides of the selected carcasses were randomly assigned to be excised at either 24 or 48 h postmortem. Color, water-holding capacity, and shear force measurements were determined after an aging period of 2, 3, 4, 7, and 14 d, respectively. Color of longissimus muscle samples from veal calves with similar preslaughter blood hemoglobin values becomes significantly lighter with a faster pH fall. Muscle color was not affected by time of deboning and overall color of all longissimus samples remained stable during storage and was not affected by rate of pH fall and time of deboning. Cooking losses increased with both a faster rate of pH fall and by deboning at 24 h postmortem. Drip losses during vacuum storage were higher for muscles excised at 24 rather than 48 h postmortem. Both when deboned at 24 and 48 h, postmortem veal carcasses with a lower rate of pH fall had higher shear force (SF) values than did carcasses with a higher rate of pH fall. Deboning at 24 h postmortem resulted in higher SF values than deboning at 48 h postmortem. Differences in SF between 24- and 48-h deboning were larger in slower glycolyzing carcasses. Aging improved tenderness but did not fully reduce the difference in SF values between 24- and 48-h deboning. The results suggest that deboning of veal carcasses before the ultimate pH has been reached may result in muscle contraction, which may exert negative effects on tenderness and water-holding capacity of veal. Effects of time of deboning can, at least partly, be explained by differential effects on shortening of the muscle fibers.

Effect of dietary vitamin E supplementation, fat level and packaging on colour stability and lipid oxidation in minced beef.

The effect of addition of vitamin E (2025 IU animal(-1) day(-1)) to the diet of beef bulls on the colour stability and lipid oxidation of minced beef was studied. Control and enriched diets were provided for the last 136 days before slaughter. Batches of freshly minced meat were prepared containing approximately 1.3 and 22.2 wt% fat, respectively. Half of the samples of minced meat from control (CON) and supplemented (SUP) beef were packaged on trays with oxygen-permeable over wraps and half in modified atmosphere (MA) packs (initial gas mixture: O(2)/CO(2)/N(2)=65/25/10). The minced beef was stored for 10 days at 7°C in an illuminated environment. The SUP meat at both fat levels was consistently more resistant to lipid oxidation than was the CON meat. The additional vitamin E had a greater anti-oxidant effect for the lean meat product. MA packaging in comparison to the oxygen-permeable foil over-wrap did increase lipid oxidation, the effect being most pronounced for the CON meat. A sensory panel considered the colour of the lean SUP meat during display as more attractive than that of lean CON meat, irrespective of packaging. A similar effect was observed occasionally for the relatively fat minced meat. These subjective findings were confirmed by objective assessment of colour. The stability of the colour of the MA packed meat was better than that of the oxygen-permeable foil-wrapped meat. Microbial growth patterns of enriched and control meat were similar. MA packaging retards the multiplication of mesophilic aerobic spoilage micro-organisms and Enterobacteriaceae.

Fibre area and capillary supply in broiler breast muscle in relation to productivity and ascites.

The objective in this study was to examine the capillary supply in the broiler breast muscle in relation to productivity and the incidence of ascites. Muscle samples (pectoralis superficialis) were collected from 24 pairs of broilers of a commercial paternal strain. The pairs consisted of full sib broilers (brothers and sisters). Of each pair one broiler had a high arterial pressure index, as an indication of ascites, and the other was a healthy chick of the same sex. Data collected were, among others, body weight, arterial pressure index, haematocrit and weight of breast muscle and lungs. Pectoral muscle samples were histologically analysed with respect to capillary density, fibre area and number of capillaries per fibre. Ascitic chickens (measured as high values for heart hypertrophy) had a lower number of capillaries per fibre and tended to have reduced fibre area, although they had a similar capillary density in the pectoral muscle in comparison with healthy chickens. The expected increase in capillary density was not observed. Normally capillary densities decrease in proportion to the increase in fibre size. So ascites has unfavourable relations with capillary traits. Fast growth was not significantly associated with capillary density. However, chickens with a higher percentage breast muscle had a lower capillary density. This implies that high muscularity might be a risk for a diminished oxygen supply to the breast muscle.

Effect of dietary vitamin E supplementation on beef colour stability.

The effect of dietary vitamin E upon colour, waterholding capacity, bacterial growth and lipid oxidation of beef longissimus thoracis (LT) and psoas major (PM) muscle were examined during aerobic display of fresh muscle and after aging in vacuum for 26 days. Forty crossbred beef bulls received a whole crop corn silage, supplemented with concentrate. Twenty bulls were each supplemented with 2025 mg vit E per day (added to the concentrate) for 136 day prior to slaughter and compared with non-supplemented control animals (n=20). In fresh LT muscle drip loss did not differ between treatment groups, while in PM muscle drip loss was significantly higher for the supplemented group. The treatment did not affect bacterial growth in fresh and aged muscles. Lipid oxidation during 12 day storage of fresh muscle was significantly lower for the supplemented group, as indicated by the lower TBA-values. No effect of the vitamin E treatment was observed on a (∗)-values of both fresh and aged LT muscle during display for 8 and 5 days, respectively. In PM muscle, supplemented beef had lower a (∗)-values in fresh (at day 1) and aged (at days 1 and 2) muscle, due to a lower oxygenation. The reason for this lower oxygenation is unclear. After aging, colour stability was decreased and more variable than in fresh muscle. Similar results were obtained when the difference in reflection values at 630 and 580 nm (R630-580), instead of the a (∗) value, was used as a parameter for colour stability. The absence of an effect of vit. E on the rate of discoloration, might possibly be explained from the observation that α-tocopherol levels in control muscle were relatively high (LT: 2.1 and PM: 3.2 µg/g muscle), compared with data from literature. Analysis of the feed for vit. E suggests that this was due to a relatively high natural vit. E uptake from the feed, which was calculated to be approx. 330 mg vit. E per animal per day for the control group.

Post-mortem variation in pH, temperature, and colour profiles of veal carcasses in relation to breed, blood haemoglobin content, and carcass characteristics.

A total of 1764 male calves of the Meuse-Rhine-Yssel (MRY) and Friesian-Holstein (FH) breeds were slaughtered at two commercial slaughterhouses to investigate the variation in pH, temperature, and colour of Dutch veal carcasses processed without electrical stimulation and with a moderate chilling regimen (average temperature of the longissimus lumborum muscle at 45 min, 3, 24, and 48 h post-mortem was 38.4, 23.3, 3.7 and 1.9°C, respectively). Blood haemoglobin content was determined 2 weeks before slaughter. The efficacy of captive bolt stunning was scored and the carcass movements after shackling registered. Temperature and pH measurements were carried out at 45 min, and 3, 24, and 48 h after slaughter in the longissimus lumborum muscle (LL). Muscle surface colour (CieLAB-values) was measured with a colorimeter at the rectus abdominis muscle at the same times post-mortem. Carcass conformation and visual carcass colour classification were determined at 45 min post-mortem. Carcasses with a better EUROP-conformation score and heavier weight showed a higher rate of pH decline and a slower cooling rate. Slight differences in cooling systems between the slaughterhouses caused marked differences in pH and temperature profiles. Significant differences in carcass weight were observed between the MRY and FH breeds, leading to significant differences in pH and temperature profiles. Carcass colour of the two breeds was similar. Veal carcass colour in general was not related to the observed variation in post-mortem pH and temperature in the longissimus lumborum muscle and was shown to be more associated with the blood haemoglobin content. Haemoglobin content of the blood in the period before slaughter was shown to be related to the visually assessed carcass colour at 45 min post-mortem (using a 10-colour scale), as well as to the instrumentally determined L*-value, with significant correlation coefficients of 0.61 and -0.61, respectively. Repeated captive bolt stunning to obtain unconsciousness significantly decreased pH at 3 h post-mortem. The degree of carcass movement after slaughter did not influence pH, temperature, or colour profiles of the carcasses.

Effect of the dietary supplementation with vitamin E on colour stability and lipid oxidation in packaged, minced pork.

The effect of supplementation of vitamin E (200 W kg(-1) feed) in the diet of pigs on colour stability and lipid oxidation in minced pork was studied. Control and enriched diets were provided for the last 12 weeks before slaughter. Half of the samples of minced shoulder meat from control and supplemented pigs were packaged on trays with oxygen-permeable overwraps and half in modified atmosphere packs (initial gas mixture: O(2)/CO(2)/N(2) = 66/ 27/7). Meats were stored for 10 days at 7 °C in an illuminated retail display cabinet. The meat from vitamin E-supplemented pigs was more resistant to lipid oxidation than was the control meat. Gas packaging appeared to increase lipid oxidation in control meat, whereas lipid oxidation was stable in meat from vitamin E-supplemented pigs. Colour stability for gaspacked meat was comparable for both dietary groups. However, oxygen-permeable overwraps had a negative effect on colour stability in vitamin E-enriched meat. The reason for this is not known. The shelf-life of enriched and control meat was similar. Thus supplementation of pig feeds with vitamin E is recommended if an improved stability against lipid oxidation of (minced) pork is required.

Effect of pelvic suspension and cooking temperature on the tenderness of electrically stimulated and aged beef, assessed with shear and compression tests.

Electrically stimulated carcass sides of young bulls were suspended at 1 hr post mortem from the aitch bone (pelvic suspension; PS) and Achilles tendon (AT), respectively. After an ageing period of 14 days at 3 °C, shear force (SF) and compression (20 and 80% compression) tests of the Mm. longissimus lumborum et thoracis (LO) and semimembranosus (SM) were conducted in raw muscle and after heating for 1 hr at 55, 60, 65, 70 and 80 °C. Collagen content was higher in SM than in LO, while sarcomere length (SL) of raw muscle were 1.75 and 1.78, for LO and SM. In comparison with the AT-side, PS increased SL by 21 and 47% and cooking loss (at 80 °C) by 2 and 6% for LO and SM, respectively. Drip loss of whole muscles from the PS-side during the ageing period tended to be lower (n.s.). Over the whole cooking temperature range, SF-values were relatively high for the SM in comparison with LO. For both muscles from the AT-side, the lowest SF-values were observed at 60 and 65 °C. The PS-treatment resulted in higher SF- values for raw muscle and after cooking at low temperatures (55 and 60 °C), particularly in the SM. In the intermediate temperature range (65 and 70 °C), PS had no significant effect, while in the higher temperature range (80 °C), SF-values were lower in the PS-side. Similar tendencies were observed in the LO, although the lower SF-values for the PS-side were observed already at 60 °C. In non-destructive compression (20%), there was a gradual increase in stress values with increasing cooking temperature. In comparison with the AT-side, the PS treatment resulted in the LO in similar or higher, and in the SM in lower stress values. With destructive compression (80%), PS resulted in SM in higher stress values in raw muscle and at 55 °C, in accordance with the SF-values. It is suggested that the higher SF- and 80% compression values in raw muscle and at low cooking temperatures, are caused by an increase in collagen strength due to a change in the direction and spatial organisation of the collagen fibres as a result of stretching of the muscle. This study demonstrates that the relative contributions of the collagen and myofibrillar components to the mechanical assessed toughness, as well as the effect of pelvic suspension, is dependent of muscle, cooking temperature and the mechanical test applied.

Effect of dietary vitamin E supplementation on pork quality.

The purpose of this experiment was to examine the effect of dietary vitamin E supplementation on pork quality, and in particular on colour stability. Crossbred pigs (n = 72) at a mean weight of 44 kg were assigned to one of two treatments. One group received, during a period of 84 days prior to slaughter, a tapioca based diet, which contained 8 mg vitamin E per kg feed. The other group received during this period the same diet, except it was supplemented with 200 mg vitamin E per kg feed. Muscle samples of longissimus thoracis and lumborum (LL) and psoas (PM) were collected at 24 hr post mortem and meat quality was assessed: pH, drip and cooking loss, shear force and intramuscular fat content. Colour stability was evaluated in fresh muscle (LL and PM) and after freezing (LL only) by measuring redness (a(∗)-values) during 6 days of storage at 7 °C. TBA-values and microbiological counts were also determined during storage. Results showed that extra dietary vitamin E had no effect on pig performance (daily gain, feed efficiency, lean meat percentage) nor on meat quality traits. The vitamin E levels were five times higher in the muscles of the treated group than the control group. In comparison with fresh LL muscle, colour stability was lower in PM and after freezing. In both muscles, the vitamin E treatment reduced TBA-values, in particular after frozen storage. No effect was found on microbiological counts. Colour stability was improved in LL after 6 days of storage, but not in PM. The effect in LL is too late to be of practical significance, since pork is usually sold well before that time in The Netherlands. It is suggested that variation in feedstuff composition of the diet may possibly explain part of the variable results reported in literature for the effect of vitamin E supplementation on colour stability of pork.

Effects of dietary clenbuterol and salbutamol on meat quality in veal calves.

Sixty male calves were assigned to one of four treatments, including (1) an untreated control, (2) clenbuterol; 1·6 mg/(calf.day), (3) and (4) salbutamol: 60 and 100 mg/(calf.day). Animals were milk-fed during 24 weeks, and ß(2)-agonists (BA) treatment occurred during the last 4 weeks including a 3-day withdrawal period before slaughter. Under identical feed intake amongst groups, treatments with BA had significantly positive effects on carcass weights and dressing percentages. BA induced muscle hypertrophy as evidenced by an improved EUROP carcass classification, 1 19-24% higher m. longissimus loin eye area and higher muscle protein/DNA and protein/RNA ratios. Through a dilution effect, this might explain the lower haem content of the m. semimembranosus and m. longissimus lumborum (LL) and diminished Hunter a(∗) value (redness) of the latter muscle. A higher ultimate pH was found in the m. semitendinosus and m. psoas major of BA-treated calves. The m. longissimus thoracis glycogen content appeared to be lowered by salbutamol. No effects of BA were encountered for water-holding properties of this muscle. Significantly higher shear force values (31-45%) for treated animals were measured for the LL which were parallelled by higher initial values for the calpain-inhibiting activity of calpastatin and a decrease of the µ-calpain/calpastatin ratio. EUROP fatness of carcasses and LL intramuscular fat content tended to be lowered by both BA. Effects of clenbuterol and of the higher salbutamol dose, which on a molecular base was administered at a 70 times higher level, were roughly of a comparable order. The lower dose mostly had intermediate effects. This means that in veal calves, clenbuterol is biologically more potent than salbutamol.

The effectiveness of examining early post-mortem musculature to predict ultimate pork quality.

Variations in pork quality reflect value differentials. However, only when they can be easily, accurately, rapidly and cost-effectively detected, can swine producers expect to eliminate poor quality from their herds through genetic selection, and can the industry be expected to take the necessary environmental precautions to prevent poor quality. This study was designed to assess the effectiveness of various techniques thought to predict ultimate pork quality through the examination of the physical and chemical properties of early post-mortem (PM) musculature. Based on stiffness and pH 30, 285 carcasses were selected. This selection procedure ensured a wide variation in ultimate quality. Using 12 instruments simultaneously, temperature, stiffness, electrical properties, lightness properties, and pH 45 of the early PM longissimus thoracis et lumborum were recorded to predict ultimate quality. Based on post-rigor light reflection and water-holding capacity (WHC), quality was assigned to one of five arbitrary groups. Of all techniques tested, the only one with any potential for adequate prediction of quality categories was pH 45. Combination of different techniques did not significantly increase predictive values. For predicting quality of single carcasses, pH 45 should not be considered satisfactory. However, based on our success in selecting carcasses representing quality variation for this study and the results obtained from the study, using pH 45 and muscle stiffness to select groups of carcasses is feasible. We conclude that the techniques used early post mortem are not appropriate for predicting ultimate pork quality for single carcasses. At present we recommend that only post-rigor muscle be considered, and that ultimate pH, light reflection and a measure of WHC should be used.

Evaluation of invasive instruments for assessment of veal colour at time of classification.

In a random selection of 480 veal carcasses, invasive measurements were made on the longissimus lumborum (LL) and biceps femoris (BF) with the Colormet, Hennessy Grading Probe (HGP4; LL only) and Invasive Meat Colour Meter. Surface colour of the rectus abdominis (RA) was determined instrumentally with the Minolta Chromameter and Surface Meat Colour Meter and visually by two persons, using a colour standard. All measurements were made at 30-40 min post mortem. Of the measurements made on the RA, the Surface Meat Colour Meter was best related to both visual judgements (r = -0·79; -0·73). The correlation coefficient between both visual judgements was 0·77. Clear differences were found between the invasive instruments in their ability to determine veal colour. The correlation coefficients between the invasive measurements and both visual judgements varied for the Colormet L (∗)-value from -0·18 to -0·35, for the HGP4 from -0·40 to -0·49, and for the Invasive Meat Colour Meter from -0·69 to -0·74. Both for LL and BF the best relationships were found between the Invasive Meat Colour Meter and the Surface Meat Colour Meter (RA).

Effects of feed withdrawal before delivery on pork quality and carcass yield.

A total of 270 pigs from a Yorkshire/Duroc/Landrace 3-way cross, reared under an ad libitum feed regimen, were delivered for slaughter after fasting (with access to water) for 24 and 0 h (Exp. 1), 16 and 0 h (Exp. 2) and 24, 16 and 0 h (Exp. 3). The interval between delivery and slaughter was 4-5 h. Feeding until delivery resulted in a lower pH at 45 min post mortem in the longissimus muscle. Ultimate pH values of longissimus and semimembranosus muscles were higher after feed restriction for 24 h. However, the incidence of dark, firm and dry (DFD) (pH > 6·2) was also increased after fasting in Exp. 1. Assessment of meat quality in samples taken from the longissimus at 20 h post mortem showed that, in comparison with feeding until delivery. Hunter L(∗) (Lightness)-values and drip loss decreased and firmness improved by prolonged fasting (24 h). Fasting for 16 h did not reduce drip loss, but colour was improved (lower Hunter L(∗)-values) in Exp. 3, although not in Exp. 2. Feeding until delivery resulted in better meat quality in Exp. 2 than in Exp. 1 and 3. A significant reduction in dressing percentage as a result of fasting was only found in Exp. 1. There appears no economic disadvantage in restricting feed for 16 h prior to delivery. Although the incidence of DFD may also increase, a fasting period of 16-24 h is recommended to reduce pale, soft and exudative (PSE) muscle, while losses in carcass yield are minimized. Other advantages of fasting are discussed.

Differences in quality characteristics of normal, PSE and DFD pork.

Differences in water-holding capacity, colour and tenderness/toughness were studied in 21 pork loins belonging to three quality categories, i.e. dark firm dry (DFD), normal and pale soft exudative (PSE). The division into the three groups was based upon the ultimate pH-values of the loins (< pH 5·5, pH 5·5-6·0, pH > 6·4). The PSE loins were characterized by a poor waterholding capacity, higher cooking loss and paler colour in contrast to the DFD category. The normal loins took an intermediate position. Neither sarcomere length, determined on fresh muscle tissue, nor Armour tenderometer values showed significant differences between the various quality categories. This was in contrast to the Warner-Bratzler (W-B) shear force values, determined on cooked loins, which had the lowest values in the DFD category. A strong relationship between the W-B values and the cooking losses was found. It was concluded that neither sarcomere length nor Armour tenderometer measurements were able to predict the shear force values of cooked pork loins.