Risk assessment of DFD meat due to pre-slaughter conditions in pigs

A polychotomous logistic regression model was used to identify and assess the risk factors for pork becoming dark, firm and dry meat (DFD). A total of 116 deliveries, comprising 3075 commercial pigs delivered from different farms to five commercial Spanish pig abattoirs were surveyed. The DFD condition was described as an ordinal response variable (normal, moderate and serious) based on measurements of pH₂₄ in the Semimembranosus muscle. The abattoir, the floor of the lorry, the season, the gender, and the stocking density during transportation influenced the risk of DFD, as well as on-farm fasting time, lairage time and estimated carcass lean content. No effect of the RYR1 gene in the risk of DFD was found. Abattoirs should be especially careful with females slaughtered in winter, where the risk of serious DFD is 4.6% higher than with males slaughtered in summer. The risk of DFD increased with high stocking density and lairage time, and with on-farm fasting times longer than 22 h. Our results revealed that lowering the stocking density from 0.37 to 0.50 m² per 100 kg pig during transport would increase the risk of DFD pork by 11%.     

The effect of stocking density in transit on the carcass quality and welfare of slaughter pigs: 2. Results from the analysis of blood and meat samples

In a trial involving 2496 pigs, the influences on blood profile and pork quality of stocking densities ranging from 201 to 321 kg m⁻² were examined. The pigs came from four different farms and were killed in 16 weekly batches. They were transported for on average 3 hr and held in lairage for 1 hr. Higher stocking densities resulted in more physical stress to the pigs based on the activity of the enzyme CPK in the blood. Stocking density did not apparently affect psychological stress and high densities did not result in dehydration. The colour, water holding capacity and instrumentally-determined texture of the pork from the carcasses of the pigs were not affected by stocking density. The experimental design and precision of the measurements were sufficient to detect numerous differences in blood profile and pork quality between pigs from the four source farms. These differences probably related to different degrees of stress-susceptibility. The results suggest that the highest stocking density examined (321 kg m⁻²) is unacceptable for the transport of pigs. The second highest density (281 kg m⁻²) produced relatively little evidence of an adverse effect on the welfare of pigs. It may be scientifically acceptable for short journeys (≤3 hr) but not for longer ones where pigs need more space to lie down.     

The effect of stocking density in transit on the carcass quality and welfare of slaughter pigs: 1. Carcass measurements

In a trial involving 2496 pigs, the effect of transport stocking densities of 201, 241, 281 and 321 kg m⁻² on carcass quality and welfare were evaluated. This range encompassed the upper level set for 100 kg pigs in European Union legislation (235 kg m⁻²). Four farms and two lorries were involved over 16 experimental days with an average journey time of 3 hr. Stocking density had no effect on any variables measured. Source farm had a significant effect on ultimate pH, reflectance and electrical conductivity in the m. longissimus dorsi, reflectance in the m. adductor and extent of rigor mortis development in the m. semimembranosus. Overall, the measurements made produced no evidence that transport stocking density had an effect on the carcass quality or welfare of 95 kg pigs on short journeys.     

Influence of loading method and stocking density during transport on meat and dry-cured ham quality in pigs with different halothane genotypes

The effect of loading method and stocking density in transit on meat and dry-cured ham quality was investigated in pigs with different halothane genotypes. A total of 507 Italian heavy pigs, supplied by two farms, were loaded by ramp or lift and transported unmixed for 35–55 min to the abattoir at a stocking density of either <0.4 or >0.6m² per 100 kg pigs. After overnight lairage in separate pens with free access to water, the pigs were slaughtered. Halothane genotype was assessed post mortem. Four hundred and thirty-nine pigs had a homozygous dominant (NN) genotype and 68 pigs were heterozygous (Nn). Carcass skin damage, meat quality traits and ham curing parameters were evaluated. Loading method and stocking density showed a negligible effect on meat and dry-cured ham quality while the predominant factor affecting these was the halothane genotype. Nn pigs produced meat with a faster rate of pH fall and lower water holding capacity as well as ham with higher weight losses in salting and greater incidence of defects in the dry-cured product. There were insignificant interactions between halothane genotype and loading method or stocking density. Overall, irrespective of pre-slaughter treatment, the Nn pigs were less suitable for the production of high quality products such as dry-cured ham.     

Effects of housing conditions of slaughter pigs on some post mortem muscle metabolites and pork quality characteristics

The results of two experiments studying the effects of housing conditions on post mortem muscle metabolism and meat quality are presented. In the first experiment slaughter pigs (n=71) from two different crossings, were raised at a density of 0.7 m²/animal (10 pigs/pen) either with (enriched) or without (conventional) a bedding of daily fresh straw. In the second experiment, animals (n=60) were reared under either conventional or free range housing (1.25 m²/animal, 30 pigs per pen) conditions. Main differences between conventional and enriched housed pigs were found in the biceps femoris (BF) muscle, and related to temperature, drip loss and colour. Association studies revealed that there were significant correlations between early (0–4 h) post mortem muscle pH and glycogen and lactate concentrations and between muscle pH measured at 1 h post mortem and muscle rigidity, expressed as the rigor value. There were significant differences with respect to meat quality and post mortem metabolism of the longissimus lumborum (LL), between conventional and free-range pigs. Early post mortem pH (0–4 h) was highest in the free-range pigs, due to low lactate concentrations. The relatively fast pH decline in the conventionally housed group resulted in increased amounts of water exuding from the meat, as measured by the filter paper method. The ultimate pH, was lowest in the free-range animals. The differences in ultimate pH, however, had no effect on drip or cooking losses. It can be concluded from these results that enrichment of the housing system has little effect on the course of the post mortem metabolism and meat quality. However, increasing the freedom of movement by applying lower stocking densities, affects the post mortem muscle metabolism, resulting in reduced water exudation. Correlations up to 0.7 between energetic parameters are not sufficiently high to be useful to predict meat quality of individual carcasses.     

The effect of experimental stress on sarcoplasmic reticulum Ca transport and meat quality in pig muscle

Stress before slaughter affects the meat quality of pigs and a disorder in the Ca²⁺ transport of the sarcoplasmic reticulum (SR) results in inferior meat quality. The object of this work was to determine the impact of stress on SR Ca²⁺ transport in pig muscle in animals with no mutation in the Ca²⁺ release channel. At about 80 kg live weight, pigs were stressed either by running for 4 min (n=9) or by a 5 min application of a nose snare (n=7). Immediately before and after the application of the stress, as well as 4 h after the stress, biopsy samples of the longissimus muscle were taken and the Ca²⁺ uptake of the homogenised muscle samples determined. The nose snare stress reduced the rate of Ca²⁺ uptake by 9% (P=0.02) and running by 18% (P=0.06). Uptake in samples taken 4 h after the stress was at initial levels. The pigs were slaughtered at an average live weight of 109 kg. Half the pigs were stressed just before slaughter for 5 min by the use of a nose snare. Immediately after exsanguination longissimus muscle samples were taken, Ca²⁺ uptake measured, and later standard meat quality parameters were determined. Although the stress reduced the Ca²⁺ uptake rate (61.3 vs. 46.4 nM/min per mg protein for control and stressed pigs; P=0.04), the meat quality was not significantly affected.     

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.     

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.     

Preslaughter handling of pigs and the effect on heart rate, meat quality, including tenderness, and sarcoplasmic reticulum Ca(2+) transport

It is known that stress applied to pigs can be of influence on meat quality combined with disturbed regulation of the intracellular Ca²⁺ concentration. However, the effect on meat tenderness is not sufficiently known.

In an experiment with pigs two kinds of stress (immobilisation by a nose snare (nose) and the use of an electrical goad (goad)) for 5 min just before slaughter were used and the results compared with minimum stress pigs (control). To quantify the level of stress, the heart rate during stress application was determined and it was found that the stress effect was highest in the goad pigs and surprisingly decreasing during the use of a nose snare. The meat quality did not differ between nose and control pigs, but was inferior in the goad group. Also, the goad stress significantly reduced the Ca²⁺ transport of the sarcoplasmic reticulum.

The principal hypothesis, that a disturbed Ca²⁺ transport will affect the tenderness by activating the calpain system, could not be verified. Tenderness did not differ between experimental groups using 24 h post-mortem samples, neither was there a difference in tenderness after storing the meat samples for 6 days.     

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: O₂/CO₂/N₂ = 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.     

Comparison of the performances of Nero Siciliano pigs reared indoors and outdoors: 2. Joints composition, meat and fat traits

A study on the effect of rearing system on tissue composition of principal joints and chemical–physical traits of meat and subcutaneous fat, was carried out on a local pig breed. A total of 78 Nero Siciliano pigs was used; 41 pigs were reared in woods, 37 pigs were reared in pens and fed a commercial diet. Weight at slaughter was 101.9 and 88.2 kg for indoor and outdoor pigs, respectively. Means were estimated at 77 kg of live weight. At ham dissection outdoor-pigs showed higher percentages of lean (58% vs. 55%) and lower subcutaneous fat (31% vs. 34%). In Longissimus lumborum outdoor-pigs showed a higher intramuscular fat percentage (4.3% vs. 3.3%), a lower protein content (22.2% vs. 23.4%), and higher free water (9.6 vs. 7.9 cm²). Outdoor pigs produced more light (L^*=50 vs. 46.7) and more yellow (b^*=5.84 vs. 4.88) meat. Subcutaneous fat of outdoor pigs showed higher percentages of MUFA (53.3% vs. 47.2%) and lower percentages of PUFA (10.85% vs. 14.45%), no differences were found for n−3 PUFA. Outdoor-pigs had lower atherogenicity (0.48 vs. 0.53) and thrombogenicity (1.03 vs. 1.21) indices.     

Responses of two genotypes of chicken to the diets and stocking densities typical of UK and 'Label Rouge' production systems: I. Performance, behaviour and carcass composition

‘Label Rouge’ (LR) chickens are reputed to possess improved sensory characteristics compared with birds reared under intensive conditions. The effects on body weight, food utilisation, behaviour and carcass composition, of genotype (Ross I vs ISA ‘657’), diet (conventional UK broiler vs LR) and stocking density (17.0 birds m⁻²,vs 4.25 birds m⁻²) were evaluated in a 2 × 2 × 2 experiment. ISA birds were grown to 83 days, and compared with Ross birds grown to 48 days; additionally ad libitum and control-fed Ross birds were grown to 83 days. Performance and behaviour parameters were assessed empirically. The effects on carcass composition were evaluated using standardised carcass dissection techniques and analysed by analysis of variance.

ISA birds grown under LR conditions to 83 days had similar body weights to Ross birds grown under UK broiler conditions to 48 days, but LR birds consumed more food, and converted food into meat less efficiently. LR birds had no mortality, whilst UK broiler mortality was 11.3%. Under similar conditions, Ross birds had a faster body weight gain, a larger food intake, but more efficient food conversion ratio and higher incidence of mortality. Birds stocked 17.0 m⁻² had lower body weights, consumed less food and, when fed UK diets, converted food less efficiently than birds stocked 4.25 m⁻². Both genotypes had a faster growth rate on UK diets, similar food intakes, and, as a result, better food conversion than birds given LR diets.

LR and UK broiler birds had similar carcass component weights, breast meat yields, and total meat yield, but LR birds had less meat on the frame, larger drumsticks and more meat on the wings. Under similar conditions, ISA birds had a larger percentage of wing and total bone, but a smaller percentage of breast meat and total meat yields. When Ross birds had controlled growth, total meat, bone and skin yields were similar to those of ISA birds. Birds stocked 4.25 m⁻² had more breast meat and larger frames than, but similar meat, bone and skin yields to, birds stocked 17.0 m⁻². Most carcass components were heavier in birds fed UK broiler diets, but, on a percentage basis, these birds had larger thighs, but smaller drumsticks.     

Influence of Pre-Slaughter Process on Pork Quality: An Overview

Handling practices prior to slaughter have significant influence in the stress level and animal welfare of pigs, and consequently, in the final meat quality. This paper reviews current knowledge about ante mortem factors (fasting period, farm handling, mixing, loading, unloading, transport, lairage conditions, and driving to the stunner) related to the live animal that influence pork quality with special emphasis on technological quality attributes. The development in slaughter technologies and their practical applications in pig slaughterhouses are described. In spite of genetic effects and slaughter techniques, poor pre-slaughter operations lead frequently to an increase of physiological and physical stress in pigs. Ante mortem factors, such as lairage time or moving pigs into the slaughter rooms, and inadequate design of slaughterhouse facilities have an important effect on pig stress, affecting meat quality after slaughter. Some recommendations to guarantee animal welfare and obtain the best meat quality are reviewed.     

Risk assessment of PSE condition due to pre-slaughter conditions and RYR1 gene in pigs

A polychotomous logistic regression model was used to identify and assess the risk factors for pork meat becoming pale, soft and exudative (PSE). A total of 116 deliveries, comprising 15,695 commercial pigs delivered from different commercial farms to five Spanish pig commercial abattoirs were surveyed. The PSE condition was described as an ordinal response variable (normal, prone to PSE and PSE) based on measurements of electrical conductivity in the Semimembranosus muscle 1-2 h post-mortem. The RYR1 genotype, the abattoir, the season, the gender, the floor surface in the lorry, the loading system, and the stocking density during transportation influenced the risk of PSE condition, as well as on-farm fasting time, loading time, transportation and lairage times. The effect of the RYR1 gene, determined in a subsample of 1331 pigs, was due to nn stress-susceptible pigs, in which the risk of PSE meat (PQM>6 μs) increased fourfold. Abattoirs should be especially careful in summer, when the risk of PSE meat was found to be double that of winter. The risk of PSE meat decreased with the time of transportation, though its effect depended on the stocking density. Thus, our results indicate that, for transits longer than 3 h, the risk of PSE increases with stocking density during transport, while the opposite occurs for shorter transits.     

The effect of two handling and slaughter systems on skin damage, meat acidification and colour in pigs

In order to minimize the high proportion of carcass and meat quality defects recorded in commercially slaughtered pigs, the optimum handling, stunning and bleeding-out conditions must be implemented. In this study improvements in pig handling resulted in the elimination of electric goading within the raceways, which reduced the skin blemish score by 50%. Furthermore, the application of higher stunning voltage (200 V) and the immediate bleeding-out in the prone position improved the post-mortem acidification rate in the Longissimus thoracis (LT) and Semimembranosus (SM) muscles. This resulted in a sharp reduction of the PSE incidence in both muscles. A positive effect on muscle metabolism was also showed by the lower release of CPK into the bloodflow. These results show that, under commercial conditions, the design of slaughter handling systems and the slaughter procedures can have an effect on skin damage and on the quality of the pig meat.     

Influence of lairage environmental conditions and resting time on meat quality in pigs

This study investigated the influence of lairage environmental conditions and resting time on pig carcasses and meat quality. The experimental material consisted of 1001 cross Pietrain-Duroc-Hampshire × Belgium-LR-LW pigs, held in lairage for either ≈30 min (direct slaughter) or between 2-3 h under 12 °C/90% relative humidity (RH), 20 °C/80% or 90% RH and 35 °C/50% or 85% RH. Prior to arrival at the lairage plant they were transported for about 45-60 min and subjected to a fasting period of 36 h before loading. Unloading operation and the driving of pigs to the point of stunning were carried out according to the practices used in the plant (sticks and electrical goads were used). Batches of 20-30 mixed pigs were used in each trial, held at a stocking density of approximately 0.55 m(2)/pig (≈100 Kg live weight). Lairage environmental conditions (LC), significantly affected almost all measurements, but not pH(1), in Semi-membranosus (SM) and Longissimus dorsi (LD) muscles and the carcass damage score. The influence of resting time (RT) was basically exerted on pH(u), deep ham temperature and in pH(1), of SM, the internal muscle reflectance being mostly unaffected. There were also significant batch (B) effects in a large range of parameters. Factors greatly interacted their influence on carcass and meat quality, denoting LC × B, LC × RT × B and LC × RT the most significant effects. RT × B only showed two low significant interactions for rigor value and pH(1), in SM, suggesting that, conversely to the lairage environmental conditions the influence of resting time is practically unaffected by the day of slaughter. The increase of lairage temperature decreased the frequency of normal carcasses, followed by an expressive higher incidence of PSE status. The influence of lairage relative humidity on the PSE/DFD muscle incidence depended on the associated temperature, but the most important detrimental effects were noticed in experiments carried out at 35 °C. In respect to lairage resting time, the influence on meat quality is strictly related to environmental conditions, mainly the temperature. Nevertheless, and excepting the assays at 35 °C/85% RH, direct slaughter of pigs (= 30 min in pens) generally produced less carcasses of normal quality than resting periods up to 2-3 h.     

Meat quality assessed Ante- and Post mortem by different ryanodine receptor gene status of pigs

Different breeds and crossbreeds (total 63) of pigs with defined genotype (DNA based test on RYR 1 gene status) were divided in normal (non mutant), heterozygotes (carriers, monomutant) and homozygote positive (dimutant) animals. Muscle biopsy samples were taken at approximately 80 kg live weight using an efficient non-stress spring-loaded biopsy instrument. After incubation of muscle samples (39 °C, 1 hr) analyses pH, WHC (fluid), R value (ITP:ATP) were performed. After slaughter, meat quality values (pH₁, pH₂₄, R value, colour, drip loss) were also carried out. Heterozygotes were intermediate and between both homozygote pig groups in most meat quality values analysed. Using WHC (fluid volume) values (0.45 and 0.48 respectively) it was possible to divide heterozygotes into two groups, each closer to homozygotes. The values of pH, WHC (fluid), as measured at definite times on the biopsies, were correlated with the pH₁ post-mortem value (r approx 0.6–0.7). The results support previous findings on the possibility of differentiating pigs within DNA test-defined groups. Introducing the gene into a pig population could be useful, in improving leanness and muscling: but meat quality is certain to deteriorate. Further experiments are needed to support the possibility of identifying PSE-prone pigs from among normal non mutant pigs.     

Effect of Brussels sprouts and inulin/rape seed cake on the sensory profile of pork M. longissimus dorsi

The objective of the present study was to evaluate the influence of two diets containing either Brussels sprouts or inulin/rape seed cake, compared with a standard diet (control) for slaughter pigs on flavour and odour attributes and sensory profile of cooked pork. Three weeks prior to slaughter 24 female pigs were allocated to three diets: (1) a standard grower-finishing diet (control) for slaughter pigs containing barley, wheat and soy-bean meal, (2) the control diet containing 11 energy percent Brussels sprouts and (3) a diet containing 25% inulin and 55% rape seed cake. The odour and flavour of the cooked meat from inulin/rape seed cake-fed pigs differed significantly from the other two diets, showing reduced meat odour, increased pig and acrid odour, increased pig flavour, reduced fresh flavour and total impression. Meat from the Brussels sprouts-fed pigs deviated only slightly from the control-fed pigs.     

A REVIEW OF THE CAUSES OF VARIATION IN MUSCLE GLYCOGEN CONTENT AND ULTIMATE pH IN PIGS

Muscle glycogen at slaughter causes variation in pork technological qualities, since it affects the ultimate pH (24 h postmortem). This review addresses various factors influencing muscle glycogen storage and the ultimate pH of pig meat. Results discussed in this paper indicate that breed and preslaughter handling, i.e., waiting time in lairage, mixing, and to a lesser extent fasting, significantly influence ultimate pH. Furthermore, interactions between handling procedures and breed could be highly significant, as with PSE meat. Since the recent discovery of the major gene rn⁺/RN⁻ which is assumed to influence glycogen concentration in the muscle of live pigs, genotype is considered an important source of variation in ultimate pH. All factors likely to influence glycogen concentration must be considered relative to the metabolic and contractile properties of muscle. These play an important role in the amount of glycogen at rest and in its depletion during chronic stress or muscular exercise.     

The effect of stocking density during 4 hour transport to slaughter on behaviour, blood constituents and carcass bruising in Friesian steers

The aim of this work was to assess the response of Friesian steers to road transportation at low, medium and high (ca 200, 300 and 600 kg/m(2)) stocking densities in terms of physiology, behaviour and carcass bruising. Stocking density was determined by adjusting the number of animals per pen (3 runs) or by adjusting pen size (3 runs). Plasma cortisol and glucose increased (P < 0·001) with stocking density, as did plasma CK activity (P < 0·001) and carcass bruising (P < 0·01) both of which indicate muscle damage. At constant stocking density stress increased with pen location towards the tail of the truck, as reflected by a significant increase in plasma cortisol. Stocking density influenced standing orientation within the truck. At low stocking density animal movement was unrestricted and the preferred orientation was standing parallel to the direction of travel; there was a strong bias against diagonal orientations. Losses of balance were associated with specific driving events, notably braking and cornering. Minor losses of balance were observed at all stocking densities, but major losses of balance including animals going down underfoot were associated with high density. When an animal went down at high stocking density it did so involuntarily and was sometimes trapped down, destabilizing other members of the group in a domino effect. Exploratory, sexual and aggressive behaviours were inhibited at high stocking density, with the exception of mounting and pushing, which increased in frequency with stocking density. It was concluded that the high stocking density adversely affected animal welfare and lowered carcass quality when compared with the medium and low stocking densities.