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Presented at the American Meat Institute Foundation, Animal Handling And Stunning Conference on February 21-22, 2002
Most of those in the production, marketing, transportation and packing sectors of the U.S. meat-animal industry practice good husbandry, have a caring attitude about animals and their welfare, and handle animals appropriately, while a tiny fraction of people do not (Smith and Grandin, (1999a). It is to those few who either do not know, or do not care, that inappropriate/improper handling can cause problems and that proper handling can improve products and profitability, that this paper is directed. Warriss (1992) said “Getting animals from farm to abattoir forms the first link in the chain of meat production and one which is both important and, to some degree, contentious; important because it can influence carcass and lean meat quality, and contentious because the processes of handling and transport provide many opportunities for the animal's welfare to be compromised." If animal handling is exemplary, little or nothing will be gained by attempting to improve it; but, if, in any sector, there is room for improvement in animal handling, attempts to rectify situations that compromise products/profitability will be well worth the effort. Seventeen years ago, Grandin (1981 b) found that quiet, gentle handling of feedlot cattle cut bruises in half at the packing plant.
The 2000 National Beef Quality Audit (Smith et al., 2001) established "Goals, By 2005" for improving the quality and value of fed beef. These goals are: (1) Eliminate USDA Standards. (2) Eliminate Yield Grades 4 and 5 carcasses. (3) Eliminate injection-site lesions from all whole-muscle cuts. (4) Eliminate side branding. (5) Reduce horns to less than 5% in fed cattle. (6) Develop and implement a standardized, electronic, individual animal identification system. (7) Develop an information system that allows producers to benchmark their own herd. (8) Assure seedstock animals are accompanied by meaningful genetic data (EPDs, etc.). (9) Assure that 100% of cattlemen complete BQA training. (10) Eliminate major and critical bruises. (11) Improve the transportation (handling and equipment) of cattle. (12) Continually improve the eating quality of beef. Potential revenue gains, if all steers/heifers had no defects due to Improper Management (no hide defects, no cattle/carcass/offal condemnations, no injection-site lesions, no bruises, no dark-cutters and no grubs/blood- splash/calluses/yellow fat), would be $18.23 (compared to $40.14 in 1995) for each slaughter steer/heifer produced in the U.S (Smith et al., 2001). The 1995 International Beef Quality Audit (Morgan et al., 1995) identified the following principle reasons that foreign importers of beef purchase product from the U.S.: (1) Ability Of The U.S. To Supply Individual Beef Cuts And Offal Items. (2) Tenderness And Flavor Of U.S. Beef Is Exemplary. (3) High Perception Of Value Of U.S Beef. (4) High Overall Product Quality. (5 tie) Image Of The U.S And Its Beef Quality Grading System. (5 tie) Confidence In The Safety Of U.S Beef. Smith (1995) identified, as the primary inconsistencies in the quality of U.S. beef, (a) Insufficient Palatability, (b) Inadequate Marbling, (c) Problems With Color, Water-Loss And Shelflife Of Beef Muscle, and (d) Production/Management Errors Causing Blemishes, Bruises, Defects, Diseases And Condemnations. Smith and Morgan (1995) said that the research needed most to resolve the inconsistencies in beef quality must involve genetic studies and further investigations of the supplemental feeding of Vitamin E to feedlot cattle. National Cattlemen's Beef Association (1998) in its long range plan, identifies as a desired Outcome of the Food Safety, Quality and Consistency Leverage Point, "Reduce carcass defects 50% by the year 2001 ". Using the 1995 National Beef Quality Audit (Smith et al., 1995) as the baseline, the U.S. beef industry reduced defects and recaptured 15.43% ($20.96) of the value lost in 1995 due to production related defects (Smith et al., 2001)
The 1993 National Pork Chain Quality Audit (Morgan et al., 1993) identified, among the greatest pork-quality concerns of packers, three items related to production/management: (2) Elevated Incidence Of Color/Texture Problems Associated With Pale, Soft And/Or Watery Pork, (4) Too High Incidence Of Injection-Site Blemishes And Broken Hypodermic Needles In Carcasses And Cuts, and (6) Excessive Amounts Of Trimming Required On Carcasses. Slaughter-floor audits revealed (Morgan et al., 1993) that 0.2% of all market hogs sent to slaughter were condemned (with 36% of the 0.2% due to dead-on-arrivals or dead-in-pens) and that at least superficial bruising (but usually worse) occurred on 1.9%, 0.4% and 0.9% of hams, loins and shoulders, respectively, of market hogs. Fabrication audits revealed that 9.1 % of all hams and loins had lean that was pale, soft and watery while 2.5% of all hams and loins had lean that was dark, firm and dry (Morgan et al., 1993).
The 1994 International Pork Quality Audit (Morgan et al., 1994) revealed that the top five reasons that foreign importers of pork purchase product from the U.S. were: (1) Confidence In Product Safety. (2) Competitive Prices. (3) Excellent Palatability (Especially, Excellent Tenderness). (4) High Perception/Image Of The United States Of America. (5) Availability Of Individual Pork Cuts. The top five areas in which U.S. pork, for export, needs to be improved (Morgan et al., 1994) were: (1) Variation In Lean Quality Characteristics. (2) Lack Of Customer Service. (3 tie) Abscesses/Bruises/Foreign Materials Occur In Pork, Too Often. (3 tie) Excessive Seam Fat. (5) Cut-Sizes That Are Too Large. Smith (1995) identified, as the primary inconsistencies in the quality of U.S. pork, (a) Insufficient Palatability, (b) Inadequate Color/Firmness/Water-Holding-Capacity Of Muscle, and (c) Production/Management Errors Causing Blemishes, Abscesses, Bruises And Presence Of Foreign Materials In Pork. Smith and Morgan (1995) said the research needed most to resolve the inconsistencies in pork quality must involve genetic studies.
Vansickle (1990) reported results of a 1989 survey of 12 beef, calf and sheep packing plants in seven states by Temple Grandin as follows: (a) Compared to results of surveys conducted in 1972-1974 and in 1986-1988, handling has gotten better because people understand that rough, abusive handling costs money in bruises, sickness and lowered meat quality. (b) Packing plants have good handling when top management personnel insist on it. (c) Successful handling hinges on employee behavior and that has improved in the large packing plants because management personnel are emphasizing and enforcing good handling. (d) Handling ratings for employees in the 12 plants were "excellent" in 5 plants and "acceptable" in 7 plants while no plants had "not acceptable" or "cruelty" ratings. (e) Handling ratings for equipment in the 12 plants were "excellent" in 6 plants, "acceptable" in 4 plants and "not acceptable" in 2 plants while no plant received a "cruelty" rating. (f) The primary reasons the 2 plants were considered "not acceptable" for the equipment rating were broken chutes, slick floors, or of such poor design that quiet, humane handling was impossible.
Appropriate handling of cattle and swine, as contrasted with improper or inappropriate handling, can result in improved productivity of live animals; in higher quality of slaughter livestock, carcasses and cuts; and in greater profitability in the production and packing sectors (Smith and Grandin, 1999b). Improved productivity accompanying more appropriate handling could occur in the form of higher daily gains, improved feed efficiency and greater margins of profit in the livestock production sector. Grandin (1998a) has demonstrated that reducing handling stress improves both productivity and welfare of farm animals. Voisinet et al. (1997b), for example, has determined that feedlot cattle with calm temperaments have higher average daily gains than cattle with excitable temperaments; from those results, it can be extrapolated that keeping cattle calm -- through careful handling -- would likewise improve rate of gain in the feedlot as contrasted with handling cattle in ways that cause them to be frightened or to act aggressively. Feedlot managers have found that reducing electric prod usage in feedlots and increasing quiet handling helps cattle to go back on feed more quickly and reduces death loss due to respiratory sickness (Grandin, 1998d). A recent article by Messenger (1998) describes the importance of handling sows with care because gentle handling can improve a sow's attitude and productivity; from such findings, it can be extrapolated that keeping market hogs calm would likewise improve productivity during the finishing phase as contrasted with handling hogs in ways that cause them to react negatively to such treatment. Messenger (1998) quotes Julie Morrow-Tesch (an animal behaviorist with USDA) as saying "The difference between the best and worst pork operations is the people" and quotes Temple Grandin as saying "Breeding stock reach maximum performance if they are relaxed with their handlers."
Improvements in quality of livestock, carcasses and cuts accompanying more appropriate handling could occur in the form of fewer bruises, improved tenderness, lower incidence of darkcutting beef, and lessened occurrence of pale, soft and exudative as well as dark, firm and dry pork. A conclusion of the 1991 National Beef Quality Audit was that four sectors of the beef industry-producers, feeders, truckers and packers-can work together to eliminate bruises: (a) Producers and feeders can remove horns. (b) Truckers can take care in loading and unloading cattle. (c) Packers can use careful handling practices up to the moment of slaughter (Smith et al., 1992). Excessively long stun-to-stick intervals can cause blood-splash in both cattle and swine. Callused muscles in beef carcasses can result from severe physical trauma and, perhaps, from improper use of pour-on medications (Smith et al., 1992) so care should be exercised to minimize such occurrences in meat animals. Voisinet et al. (1997a) demonstrated that Bos indicus-cross feedlot cattle with excitable temperaments have tougher meat and a higher incidence of borderline dark cutters. Quiet, calm handling of slaughter hogs can reduce the incidence of carcasses with pale, soft and exudative muscle by 10% to 12% based on field studies conducted at two packing plants (Grandin, 1998d).
Appropriate handling of cattle and swine can improve profitability of operations in the production sector (through enhanced performance and higher valuations in merit-pricing systems) and in the packing/processing sector (through higher quality carcasses, fewer condemnations and lessened trim losses). Cattle and swine feeders can realize greater profits if animals, because they are calm and undisturbed, gain more rapidly and efficiently. And, for those cattle and swine feeders who sell animals based on carcass merit-pricing systems, generating carcasses with fewer discounts (due to condemnations; bruise losses; dark-cutting beef; pale, soft and exudative pork; dark, firm and dry pork) and of higher quality. For those in the packing/processing sector, benefits of proper handling of cattle and swine are accumulative-such that prevention of quality/condemnation/trim losses at the production sector, during marketing (e.g., at auction yards and at buying stations), during transport, and during holding, assembling, driving and stunning at the packing plant are additive, and accrue majorally in the packing/processing sector.
Wood et al. (1998) reported that extreme paleness or darkness is sometimes found in pork and beef, due to a combination of environmental and genetic factors; animals which experience stress over a lengthy period (>10 hours), usually because of mixing with unfamiliar animals or poor handling, deplete muscle glycogen stores and can develop high pH meat which is dark, firm and dry (DFD) and has poor keeping quality. Alternatively, in pigs, if the stress is experienced immediately before slaughter, muscle pH falls rapidly as anaerobic metabolism occurs and pale, soft and exudative (PSE) muscle results. Both of these conditions (DFD and PSE) can be avoided on many farms by the application of good management (Wood et al., 1998).
Proper handling of meat animals can improve productivity, quality and profitability; so, it's just good business to do it right. Appropriate handling weakens arguments by animal rightists/welfarists that those in the production and packing sectors do not have a caring attitude about the animals in their charge. Grandin (1998e) concluded that slaughtering, today, is handled more humanely than it was 20 years ago; in 1978, the Humane Slaughter Act of 1958 was expanded to cover all U.S. plants and now (in 1998), USDA is stepping up enforcement of the Act.
Grandin and Smith (2000) said the most important factor determining whether a packing plant has good or bad animal welfare practices is the attitude of management personnel; the best facilities and the latest technology make handling cattle easier but they don't make the manager better. Until the owner or manager is convinced that proper handling practices pay off economically, it is unlikely that employees will follow procedures day-in and day-out. The manager that is most effective in maintaining high humane standards is involved enough in day-to-day operations to know and care, but not so involved that he or she becomes numb and desensitized (Grandin and Smith, 2000).
Schultz-Kaster (1998) identified the four most important problems associated with improper handling of market hogs as: (1) Dead pigs. (2) Bruising and blood-splashing. (3) Broken bones. (4) Pale/soft/exudative pork and pork muscle with low water-holding capacity. Dead pigs are those DOA (dead on arrival) and those DIP (dead in pens); it is not known how or why such deaths occur but swine of genotypes that are susceptible to stress (e.g., those pigs susceptible to Porcine Stress Syndrome) when subjected to excessively high ambient temperatures and to rough handling are undoubtedly the source of many fatalities. Bruising of swine is caused by animals contacting sharp-edged objects on their own-but exacerbated by rough handling or excitement-or by people striking or kicking animals in efforts to direct or hasten pig movement. Blood-splashing (rupture of capillaries in muscle; occurrence of blood spots in the meat) can be caused by excessively long stun-to-stick intervals or by improper stunning (especially electrical stunning) but can be exacerbated by the hogs being of genotypes that are susceptible to stress and if that is combined with inappropriate animal handling. Broken bones (largely the backbone, femur and rib) largely result from improper handling but such occurrence is exacerbated by lack of sufficient calcium and phosphorus in the finishing diet of pigs (Schultz Kaster, 1998).
Anderson et al. (1998) reported that present problems with excessive drip loss and light color in pork are a consequence of relatively low ultimate pH in the meat; low ultimate pH depends on the initial glycogen level in the muscle at the time of slaughter and the level of stress induced on the animals during transportation and preslaughter procedures. By decreasing the digestible starch content, in a strategic feeding procedure, these researchers were able to reduce muscle glycogen in pigs at the time of slaughter and thereby to produce darker colored meat (superior to that in control pigs) and a tendency toward higher muscle pH (Anderson et al., 1998). Stalder et al. (1998) compared effects of rest (for 16 hours after shipment and prior to slaughter) vs. no rest (slaughter immediately following shipment) and of mixing (with unfamiliar pigs during transport and lairage) vs. not mixing (transported and held with animals with which they were familiar) on muscle quality of carcasses from pigs that were Porcine Stress Syndrome (PSS) normal (genotype NN), PSS susceptible (genotype nn) or PSS heterozygous (genotype Nn). Resting of PSS heterozygous pigs, increased carcass pH values, decreased Minolta-Y and Hunter-L values of loin muscles and lowered muscle glycogen levels; even though 16 hours of rest before slaughter improved the color and water-holding capacity of muscles from PSS heterozygous pigs, effects were small and were much less than those that were due to the PSS gene. Mixing had no effects on muscle pH or color characteristics of loin muscles but did result in higher chewiness scores of cooked loin chops from PSS heterozygous pigs (Stalder et al., 1998).
Tarrant (1998) has concluded that: (a) Greatly improved systems that are compatible with industry needs are required for preslaughter animal handling; such systems should include suitable equipment and the training and supervision of animal handlers at the farm and abattoir. (b) PSE cannot be eliminated by use of the PCR-based halothane gene test, as the halothane gene probably accounts for only 25 to 35% of the PSE meat observed in commercial abattoirs. (c) The most important factors affecting PSE and DFD incidences occur after the animal has left the farm.
The five major causes of pale, soft and exudative condition and low water-holding capacity in pork muscle have been identified by Schultz Kaster (1998), Grandin (1995) and Schwartz (1998) as (1) Genotype of pigs (especially those which carry the Halothane or RN genes and thus are more susceptible to stress). (2) Chilling carcasses too slowly. (3) Improper handling and stunning (especially when using carbon-dioxide immobilization). (4) Inadequate resting time prior to slaughter. Market hogs must be given adequate resting time (I hour must be the absolute minimum) after hauling and prior to slaughter. (5) Excessive "rail-out" time on the slaughtering/dressing floor. Both Schultz Kaster (1998) and Schwartz (1998) agree that, for pigs of genotypes that are susceptible to stress, handling must be exemplary or the incidence of pale, soft and exudative pork will be unacceptably high. Barton Gade (1998) studied quality of meat from Danish pigs and concluded that chilling at -16'C was preferred over chilling at -12'C because there was less PSE meat and eating quality was not compromised. Overnight lairage had a number of advantages compared to slaughter on the day of arrival including slightly higher muscle pH values and less PSE pork.
Inasmuch as there is no way for packing-plant employees to know which market hogs are or are not highly susceptible to stress, extreme care must be taken to handle all pigs carefully as though each was a "ticking time bomb." Careful (proper, appropriate) handling of market hogs requires consideration of adequate resting time; of careful (quiet and calm) assembling and driving; of proper stunning; of expedited slaughtering/dressing, and; of rapid chilling, if incidence of pork muscle with pale/soft/exudative condition and low water-holding-capacity is to be minimized. Messenger (1998) quotes Temple Grandin as saying "It's up to management to train employees right; there are a lot of training videos available but just showing the video is not enough. You have to teach workers and illustrate that you're serious about good handling."
Danish researchers (Barton Gade and Christensen, 1999) compared carcass and meat quality characteristics of pigs placed, before harvesting, in pens of two sizes. There was less skin damage, fewer carcasses with DFD muscle and slightly less blood-splash in carcass muscles when 15 rather than 45 pigs were held in a pen. Incidence of P.S.E. muscle was equivocal with higher percentages of PSE in biceps femoris in pigs held in smaller pens and higher percentages of PSE in longissimus dorsi in pigs held in larger pens. Further Danish research conducted by van der Wal et al (2000) compared the effects of gender (boars vs. gilts) and preslaughter stress on meat quality. Conclusions from this study indicate that boars were two times more likely to exhibit aggressive behavior and more "commotion" than gilts and meat quality (drip-loss and color) was negatively effected when pigs were negatively forced through the handling system compared to pigs moved calmly through the handling system and stunned immediately.
At the most recent International Congress Of Meat Science And Technology (Barcelona, Spain; August 30-September 5, 1998) there were 20 scientific presentation on Animal Handling And Welfare; nine studies involved "Preslaughter Effects On Welfare And Meat Quality; Interactions Between Preslaughter And Processing Effects," four investigations considered "Free Range (Outdoors) Versus Intensive (Indoors) Rearing Effects On Meat Quality" and seven papers compared "Electricity Versus Carbon Dioxide Atmosphere As Stunning Methods." Animal rights and animal welfare are of much greater concern among residents of countries in the European Union than among people who live in other parts of the world; so, scientists in EU countries are focusing heavily on properties of meat for which effects of improving handling, rearing, and/or well-being are documentable. Conclusions from those 20 scientific presentations, in the composite, were described by Wood (1998) as follows: (1) Differences, both quantitative and qualitative, in the qualities/properties of meat from animals reared under free-range vs. intensive circumstances are "only in the minds of people and have not, as yet, been documented." (2) Effects of differences in preslaughter handling on welfare of animals are temporal; on meat quality are well-documented and easy to demonstrate scientifically, and; on meat-processing attributes are real and verifiable (e.g., differences in yields of PSE, DFD and normal pork cuts, when they are pumped or marinated, are very large). (3) Animal welfarists prefer electrical stunning (because it is sudden) rather than captive-bolt stunning (because it falls too often) or carbon-dioxide immobilization (because animals struggle excessively) while research has demonstrated disadvantages in pork quality from electrically stunning pigs (because it increases the rate of muscle pH decline-sometimes excessively).
Meisinger (1999) identified nine Quality Control Points that are integral parts of "A System For Assuring Pork Quality"; those are: (1) Quality Control Point 2 - Genetic Inputs, (2) Quality Control Point 2 - Nutritional Inputs, (3) Quality Control Point 3 - On-Farm Hog Handling, (4) Quality Control Point 4 - Transporting_Hogs, (5) Quality Control Point 5 - PreSlaughter Handling, (6) Quality Control Point 6 - Stun & Early Postmortem, (7) Quality Control Point 7 - Evisceration, (8) Quality Control Point 8 - Carcass Chilling, and (9) Quality Control Point 9 - Fabrication. Meisinger (1999) further stated that the producer and the packer each contribute about half to potential quality deterioration in fresh pork; whatever is done to pigs, carcasses or pork products can either sustain the inherent genetic quality or degrade it. There is nothing except enhancement (injection of phosphate in water) or further processing that can improve pork quality.
National Pork Producers Council (1999) has developed a "Producer Pork Quality Checklist" which includes the following items related to handling traits and pork quality characteristics: (a) I require that all my breeding stock purchases be certified stress-gene free; I also certify that I do not or will not knowingly market hogs with the halothane (stress or RYR 1) gene. (b) I have considered the advantages and economics of adding vitamins E and D, carnitine, macin and magnesium for their meat quality benefits and have made a decision on that basis. (c) Even though restricting amino acids in late finishing results in dramatic increases in intramuscular fat, I do not practice it due to other negative quality consequences. (d) I do my best to make sure that all my market hogs are without feed for a period of 12 to 18 hours before stick at the plant. (e) I have eliminated (or at least significantly curtailed) the use of electric prods in my operation and I have made my pigs accustomed to human activity during the finishing period. (f) My facilities provide the least resistance and stress for pigs during handling and loading. (g) My trucker has watched the NPPC videotape on "Handling for Transporters." (h) I only hire haulers who have flat-floor trailers or, I am transitioning all my own trailers to flat-floor trailers to enhance pork quality and to reduce the DOAs. (i) I haul no more than 183 head in my 48' by 102' standard flat-floor trailer. j) I give special consideration to market hogs during weather extremes. (k) I ensure my packer is concerned about factors affecting pork quality, has taken the necessary steps to improve the quality of the end-product, and has read the "System For Assuring Pork Quality" booklet or the "Critical Points Affecting Pork Quality In Packing Plants" fact sheet.
Preslaughter stunning of pigs is accomplished most commonly by use of electricity or carbon dioxide; electrical stunning is followed by an acute fall of the muscle pH due to the powerful activation of glycolysis in the muscles (Henckel et al., 1998). The improvement in quality-reduction in both blood splashing and PSE meat incidences-more than outweigh the added financial costs of using C02 anesthetization which is the reason why Denmark uses C02 stunning for pig slaughter (Barton Gade, 1992).
Henckel et al. (1998) compared stunning of pigs with electricity (10 seconds; 250 volts; 1.3 amps; tong with one prong placed behind one ear and the other at the opposite eye) VS. C02 (3 minutes in bottom position; dip-lift installation; CO-, concentration of 90%) and reported that for pigs with similar genetic background (free from the Halothane gene) and with the same environmental exposure prior to stunning, electrical stunning resulted in twice the drip loss in the longissimus dorsi with the same ultimate pH and subjective meat color.
Facco Silveira et al. (1998) compared stunning of pigs with electricity (5 seconds; 220 volts; 1.2 amps applied manually) VS. C02 (60 to 75 seconds; 70% CO, plus 30% air; inhalation) and concluded that C02 stunning was most attractive because of higher 24-hour muscle pH, slightly more desirable muscle color (a* and b* values) and more desirable water-holding capacity of the meat. The latter scientists further concluded that: (a) Any stress placed on pigs immediately before slaughter should be avoided. (b) Unstunned, unrestrained pigs produced longissimus dorsi muscles with lower pH values (at 1 hour and 24 hours postmortem), higher luminosity (L*) values, more extensive blood-splashing and lower water-holding-capacity than pigs stunned with either electricity or carbon dioxide. (c) Considering the functional properties investigated, C02 stunning is favored over electrical stunning; the problem is mainly to avoid frightening the pigs when driving them and thus reduce excitement before they reach the anesthetization plant whether it is operating with electricity or carbon dioxide. These results were confirmed by Channon et al. (2000) who found that genotype (halothane-Nn vs. normal NN), preslaughter handling (minimal vs. stressed) and stunning method (C02 vs. electrical) had an interactive effect on the pH, tenderness and drip-loss of pork. It was concluded that pig processors should optimize their handling systems and techniques, especially if pigs carrying the halothane-n gene are being processed, minimize exposure to unfamiliar, preslaughter stressors and implement a C02 stunning system in order to improve the quality of their pork products.
Faucitano et al. (1998) compared stunning of pigs with electricity (MIDAS system; 2.4 seconds; 220 volts; 800 Hz; via two electrodes between the eye and ear P us 1.7 to 2.0 seconds; 100 volts; 50 Hz; via one electrode to the chest) VS. C02 (COMPACT system; six-chair conveyor; 83% C02; inhalation) and concluded that the higher degree of muscle activity during the epileptic attack of electrically stunned pigs compared to C02 stunned pigs led to a higher incidence of PSE (8.8% vs. 3.8%, 2 hours postmortem; 18.8% vs. 13.31/0, 7 hours postmortem; head-to-chest electrical stunning VS- C02 Stunning, respectively) and a higher incidence of DFD (16.1% vs. 8.2%, 2 hours postmortem; 8.0% vs. 3.8%, 7 hours postmortem; head-to-chest electrical stunning vs. C02 stunning, respectively). The latter results agree with the report of Barton Gade (1992) who observed a higher incidence of PSE (10% to 19%) in plants equipped with electrical stunning than in plants equipped with C02 stunning (2% to 6%).
Grandin (1998f) concluded that: (a) Ultralean hybrid pigs tend to display higher incidences of bloodsplash and broken backs during slaughter; some plants are considering adopting C02 stunning to lessen such incidences in very lean pigs. (b) C02 stunning will reduce PSE pork incidence and excessive drip loss in pork in pigs that carry the stress gene, especially those that are handled roughly and shocked with electrical prods; unfortunately, though, pigs that are free of the stress gene may produce more PSE pork when stunned with C02. (c) An improved C02 stunning system has been developed that works like a rotary milk parlor, stunning five pigs at a time (90 seconds) at a chain-speed of 1,000 pigs per hour with sufficient exposure to kill the animals while providing both practical, meat quality and humaneness advantage.
Good management combined with modern electronically controlled electric stunning equipment will reduce the advantages of CO2 stunning on pork quality. Electronically controlled systems prevent damaging amperage surges. Short stunning times combined with higher electrical frequencies will reduce both PSE and bloodsplash compared to long stunning times at 50 to 60 Hz. Bloodsplashing can be reduced by avoiding double stunning and keeping the electrode in firm contact with the animal. The electrode must be energized AFTER it is in firm contact with the animal. Sliding of the electrode during the stun must be avoided. In good animal welfare, the electrode must be positioned so that the current will pass through the brain. Many plants have greatly reduced bloodspashing by replacing stunner switches and electrical cords every few weeks. Worn switches or damp cords will cause electrical current fluctuations. Fluctuating current increases bloodspashing. Frequent cleaning of the electrodes is essential.
When CO2 stunning is compared to the very best electrical stunning it may be difficult to justify the high installation cost of CO2 stunning. Operating and maintenance costs are also much higher for CO2 stunning. Pig genetics has a greater effect on PSE than the method of stunning.
The first study reporting the possibility of bruising of cattle occurring at the stunning stage of the slaughtering/dressing process was by the Australian Meat Board (1954). Later, in the United States, Rickenbacker (1959) and Hamdy et al. (1957) established that an animal could be bruised up until its blood pressure approached zero, which indicated that damage could be done and bruises could occur after stunning. Meischke et al. (1974) noticed that carcasses were more bruised on the left side than on the right side; further investigation revealed that the left side was the side cattle fell on after stunning when released from the knocking box. Meischke and Horder (1976) studied bruises on cattle in six abattoirs in Australia and determined that differences in carcass bruises were related to the way in which each carcass was ejected from the knocking box; the site distribution of bruising on each side corresponded with those areas observed to receive the initial impact on release from the knocking box.
Meischke et at. (1974) evaluated presence of horns in cattle on carcass bruising following groups that were hornless, horned or mixed (half hornless; half horned) and reported that the weight of bruised tissue trimmed from the carcasses of horned cattle was approximately twice that trimmed from hornless cattle while the weight of bruise trim from mixed groups was intermediate between that from the hornless and horned groups. Ramsay et al. (1976) found that bruise trim weights for cattle with tipped horns were approximately twice as high as were those for dehorned cattle and that tipping of horns will not reduce the amount of bruised tissue trimmed in comparison to the amount trimmed from carcasses of horned cattle. Shaw et al. (1976) reported that the weight of bruised tissue trimmed from the carcasses of the cattle in the horned groups was significantly greater than that trimmed from the carcasses of the cattle in the hornless groups. When horned and hornless cattle were mixed, the hornless animals in the mixed group sustained significantly more bruising than animals in a group consisting solely of hornless animals while the horned animals in a mixed group have a similar degree of bruising to cattle in a group consisting solely of horned animals (Shaw et al., 1976). Winks et al. (1997) reported that heavy tipping, as a means of reducing bruising trim is of questionable value because, based upon their own study and those of two other researchers, level of bruising trim in steers with tipped horns, was of the same magnitude as that of horned steers. Wythes et al. (1979) compared bruising of cattle with untipped, tipped and no horns and concluded that: (a) Tipped and untipped cattle had similar bruising whether sent for slaughter as separate groups or together. (b) Tipping was ineffective in preventing bruising. (c) Hornless cattle had significantly less bruising than horned cattle when consigned as separate groups; however, this advantage was lost when hornless cattle were mixed with tipped or untipped cattle.
Armstrong et al. (1998) compared incidence of bruises on slaughter steers/heifers in the U.S. and in Canada using results of the 1991 National Beef Quality Audit (NBQA-1991), the 1995 National Beef Quality Audit (NBQA-1995) and the 1996 Canadian Beef Quality Audit (CCFA-1996); their conclusions were: (1) Incidence of slaughter steers/heifers that had one or more bruises was 39% for NBQA-1991, 48% for NBQA-1995 and 78% for CCFA-1996. (2) In the CCFA-1996 study, as contrasted with results of the NBQA-1995, there were many more cattle with two bruises (24% vs. 13%), three bruises (16% vs. 4%), four bruises (12% vs. 1%), bruises on the chuck (31% vs. 16%) and bruises on the loin (41% vs. 29%). (3) Value losses due to bruises for each slaughter steer/heifer harvested in Canada was $2.87 (CCFA- 1996) and in the U.S. was $4.03 (NBQA-1995).
Interestingly, in the 1994 National Non-Fed Beef Quality Audit (Smith et al., 1994), the total loss due to bruising for each cull cow/bull harvested in the U.S. was nearly $12.00 (with $3.91 attributed to errors by producers and the remainder attributed to the marketing/transporting sector and the packing sector). Bruises are an especially significant problem for salvage cows and bulls for a number of reasons, many of which are related to management, including: (1) Non-fed cattle have little outside fat cover. (2) Frequency of horns in cows/bulls is higher than in fed cattle. (3) Many non-fed cattle are marketed when they are lame, which substantially increases the numbers of bruises (Smith et al., 1994). The strategies for overcoming bruising problems are simple and straightforward, said Temple Grandin in the 1994 National Non-Fed Beef Quality Audit report (Smith et al., 1994), "Producers should dehorn calves when they are still young and market lame cattle in an expeditious manner-long before their condition progresses to the point where difficulties arise in transporting and harvesting these animals." In the 1995 National Beef Quality Audit it was stated that bruises can easily be addressed by producers, feeders, truckers and packers by working together to eliminate much of the problem (Smith et al., 1995); producers should dehorn cattle and producers/truckers/packers should take care in loading and unloading animals.
Eldridge and Winfield (1988) concluded that space allowance for cattle during truck transport can significantly affect the level of bruising, carcass weight and risk of injury to animals. Bruise scores in the low space (0.89 m 2 /animal) and high space (1.39 M2 /animal) allowance treatments were 4 and 2 times greater, respectively, than in the medium space (1.16 m 2 /animal) allowance treatment, perhaps because more animals at the medium space allowance aligned themselves across the direction of travel than at either of the other space allowances (Eldridge and Winfield, 1988).
Armstrong et al. (1998) studied effects of the Livestock Safety CushionTM which is padding applied around the rear door and in twelve additional places within the trailer, on incidence of bruises on 4,690 slaughter steers/heifers hauled up to 188 miles to the packing plant. For padded vs. unpadded trucks, respectively, total bruises were 30.1% vs. 39.5%, bruises per load were 11.9% vs. 15.9%, animals with one bruise were 8.0% vs. 10.6%, and animals with two bruises were 2.7% vs. 4.1%, respectively. Use of the Livestock Safety CushionTM (a) Significantly reduced loin bruises, and (b) Reduced trim losses from bruises by $0.39/animal which would save $1.05 million per year in Canada (Armstrong et al. (1998). One interesting finding in the Armstrong et al. (1998) study was that "feedlot of origin" was the most important factor determining extent (incidence) of bruising.
Grandin (1992a) made the following observations regarding bruising of slaughter cattle at packing plants: (a) If there is a sudden occurrence of bruises, look for recent changes in personnel and/or for broken equipment. (b) Back bruises almost always are caused by gate, truck deck or personnel problems. (c) Loin bruises result from horns on cattle, narrow entryways, protrusions into alleyways or rough handling. (d) Shoulder bruises are caused by horns on cattle, protrusions into alleyways or rough handling. (e) Cattle can still be bruised after stunning and prior to bleeding. Livestock Conservation Institute (1999) characterizes recommended practices to reduce bruising in cattle as follows: (a) Horns-dehorn all cattle; tipping doesn't help; don't crowd or overload during trucking. (b) Gates - don't throw a gate into an animal's path to stop it; have gates high/wide enough when trucking. (c) Protruding Objects-eliminate board, wire, nail, bolt protrusions; pad sliding gates and corners. (d) Fencing-pad protrusions; install belly rails. (e) Bruise Hazard Zone-the area 28 to 52 inches from the floor. (f) Flooring provides good footing; cut 8-inch diamonds in concrete; grid with 1-inch re-bar; put cleats on inclines; use nonslip material in trucks.
Bauer et al. (1998) compared quality parameters of beef from cattle that were conventionally fattened vs. cattle produced under free-range conditions; these researchers concluded that it was very doubtful that the small differences in beef quality that were observed were related to husbandry practices.
Butchers et al. (1998) studied interactions between preslaughter handling of steers and low voltage electrical stimulation (LVES) of their carcasses as they affected beef quality and concluded that: (a) The stress from trucking a relatively short distance and a 24 hour fast prior to slaughter was sufficient to slow down the rate of postmortem pH decline and avoid toughening of the beef. (b) Steers kept on feed until slaughter had a sufficiently rapid rate of glycolysis so that LVES of the carcass was not necessary to increase the rate of postmortem decline and avoid toughening of the beef.
Tyler et al. (1982) studied incidences of bruising and dark-cutting beef and concluded that the temperament and susceptibility to bruising of individual animals have more influence on the severity of bruising than does type of cattle-Zebu vs. British-and that British cattle had a higher incidence of dark-cutting beef than did Zebu cattle. Grandin (1979) and Price and Tennessen (1981) both reported that fighting among cattle that are strangers would increase the incidence of dark-cutting beef. When cattle that are strangers are mixed together, they fight to determine a new dominance hierarchy (Grandin, 1995). Grandin (1995) believes that 80% of the things that contribute to dark-cutting beef occur prior to the time the cattle reach the packing plant but that it is the plant factors (e.g., rough handling, excessive lairage-starter cattle, weekend cattle) that are the "straws that break the camel's back" and cause dark-cutting beef in carcasses.
Jones and Tong (1987) reported that: (a) The frequency of dark-cutting beef increased as transportation distance from the farm to the slaughter plant changed (from less than 60 miles to more than 180 miles). (b) Steers had a higher incidence of dark-cutting beef than did heifers. (c) Mixed loads of cattle had a significantly higher frequency of dark-cutting beef than unmixed loads. (d) The frequency of dark-cutting beef differed widely among packing plants-from a low of 0.26% to a high of 1.79%. (e) The highest monthly frequencies of dark-cutting beef were in March and April while the lowest frequency was in December.
The transport and handling procedures imposed on beef cattle during the normal course of marketing can be a significant stressor with factors like time off feed, water deprivation, mixing and the resulting behavioral problems, transport movement, unfamiliar noise, and inclement weather are often present and collectively result in live weight and carcass losses as well as degraded meat quality (Schaefer et al., 1997). Schaefer et al. (1997) studied the role of oral electrolyte therapy in attenuating transport and handling stress in cattle and reported improvements in both live and carcass weights (less shrink) of up to several percent in treated animals as well as a reduction in meat quality degradation (reduced dark cutting). Wilson (1999) found that providing livestock with electrolyte-restoring liquids (similar to sports drinks for humans) before and during transport can reduce shrinkage in pigs, lambs and calves. While all animals lost weight during transport, electrolyte-fed animals lost less weight than water-fed animals (Wilson, 1999).
Scanga et al. (1998) reported that dark-cutting beef results from preharvest stress, which depletes muscle glycogen stores and thus reduces the glycogen needed to produce the lactic acid that reduces the pH of postmortem muscle. Hedrick et al. (1959), Grandin (1992), Smith et al. (1993), Shackelford et al. (1994) and Voisinet et al. (1997a) have identified antemortem stress, weather (dark-cutting beef incidence is highest during very cold weather combined with precipitation-which induces "shivering"), genetics (largely related to temperament), fright (which induces "shivering"), gender, growth promotants and handling practices. Scanga et al. (1998) said that incidence of dark-cutting beef was affected by differing management philosophies, facilities construction and cattle-handling practices at specific feedlots; those findings agreed with Hedrick et al. (1959), Grandin (1992) and Smith et al. (1993) who determined that production/management practices such as handling and working procedures can be stressful to cattle and thus can cause increased occurrence of dark-cutters in slaughter steers/heifers.
Scanga et al. (1998) used feedlot data from a three-year period of time from nine commercial feedyards (15,439 pens of cattle; 2,672, 233 total cattle) to study factors contributing to the incidence of dark-cutting beef. The primary findings of the Scanga et al. (1998) study are as follows: (1) Heifers yielded a higher percentage of dark cutters than steers. (2) Management practice, structure and handling policy differences among feedyards generated large differences in incidence of dark-cutting beef. (3) Mean incidence of dark-cutting beef, as related to use of growth promotants, was highest in heifers given a combination (androgen plus estrogen) implant at the start of finishing and in heifers given an estrogen implant as re-implantation prior to harvest. (4) Mean incidence of dark-cutting beef, as related to use of growth promotants, was highest in steers given a combination (androgen plus estrogen) implant at the start of finishing and in steers given a combination (androgen plus estrogen) implant as re-implantation prior to harvest. (5) Occurrence of dark-cutter epidemics ("blow-outs"; incidence of 6% or more of animals in a pen) in heifers was highest in heifers given an estrogen implant at the start of finishing and in heifers given an estrogen implant as re-implantation prior to harvest. (6) Occurrence of dark-cutter epidemics ("blow-outs"; incidence of 6% or more of animals in a pen) in steers was highest in steers given a combination (androgen plus estrogen) implant at the start of finishing and in steers given a combination (androgen plus estrogen) implant as reimplantation prior to harvest. (7) Ambient temperatures higher than 95 F during 24 to 48 hours prior to shipment for harvest increased incidence of dark-cutting beef in both steers and heifers. (8) Ambient temperatures lower than 32 F during 24 to 48 hours prior to harvest increased incidence of dark-cutting beef in heifers but not in steers. (9) Fluctuations greater than 10 F between the high and the low ambient daily temperature in 24, 48 or 72 hours prior to shipment for harvest increased incidence of dark-cutting beef in both steers and heifers. (10) Holding cattle on-feed for 100 days or more past re-implantation reduced the incidence of dark-cutters per pen by an average of 38% among heifers and of 69% among steers. (11) Dark-cutting beef can be minimized further by employing feedlot management practices that incorporate seasonal climatic trends (hot weather and large temperature changes) at the time of harvest when determining implant administration, by using good handling practices, by having well-designed facilities and by promoting use of proper shipping practices (Scanga et al., 1998).
Smith and Wilson (2000) used lambs, pigs and calves to determine effects of transportation (2 trips of 45 miles each) and of administering water alone or water plus electrolytes on behavior, distress and performance traits. Weight loss was reduced substantially, very slightly and not significantly, for pigs, calves and lambs, respectively, that were given water plus electrolytes rather than water alone. Differences in behavioral traits and activities were substantially in favor of calves given water plus electrolytes versus water alone in the proportion of time spent '41ying"; all other behaviors/activities ("lying,” “drinking," "eating") were not different in any meaningful fashion for pigs, lamb or calves administered water alone versus water plus electrolytes.
Hanson et al. (2000) proposed that the feeding of supplemental chromium (an essential mineral that plays a role in glucose metabolism and which may increase glycogen deposition by increasing the efficiency of insulin) to cattle may aid in increasing glycogen reserves and which, in turn, may reduce the depletion of glycogen prior to slaughter. Heifers subjected to induced stress (estrus and social interaction) were fed or not fed a high-chromium yeast product (400 ppb of chromium for 62 days prior to slaughter) but the stress treatments were insufficient to generate dark-cutting beef, so the benefits of chromium feeding could not be assessed. Stress, though, reduced tenderness and redness of the ribeye muscles from these heifers (Hanson et al., 2000)
It has been documented in slaughter steers/heifers, that the more animals are stressed, the more likely they are to shed bacterial pathogens (e.g., Salmonellae, E. coll 0157:H7) in their feces; and, their feces contaminates them as well as other cattle in the same pen or truck. Unsanitary handling facilities, alleyways, sideboards of trucks, chutes and restrainers contribute bacterial pathogens to the external surfaces of animals. Research has determined that external animal surfaces (hide, hair, hooves, switches, etc.) are a much more important source of contamination on cattle than are the contents of the gastrointestinal tract with respect to the bacterial contaminants that are likely to be transferred from cattle, to carcasses.
For cull cows/bulls-too-the greater the stress, the more likely will be the shedding of enteric pathogens in the feces; and the greater the extent of bacterial pathogen shedding, the more likely will be the contamination of external animal surfaces. Again, subjecting slaughter animals like cull cows/bulls to more heavily contaminated facilities-as they move from the farm to the auction market and subsequently to the packing plant-will increase the likelihood that a given animal has bacterial pathogens on its hide, hair or hooves. Lameness, especially if an animal is a "downer," further increases the probability of occurrence of pathogens on external animal surfaces.
Colorado State University and Cornell University conducted a study entitled "Detection And Control Of External Pathogens: Microbial Mapping In The New York Cull Dairy Cow Project" (Kam et al., 1997) in which 80 dairy cows were selected for differences in condition, lameness and hide cleanliness. The incidences of E. coll 0157:H7 and Salmonellae, in fresh feces were 0% and 0%, on hide surfaces were 0% and 13.8%, and on carcass surfaces were 0% and 1.2%, respectively. Significant correlations with Aerobic Plate Counts were with lameness and hide cleanliness but not with condition, with Total Coliform Counts were with lameness but not condition or hide cleanliness, and with Escherichia coll Counts were not with any of the factors -- condition, lameness or hide cleanliness (Kam et al., 1997).
Clapp (1999), discussing "areas for consideration" as FSIS reformulates its policy, says the agency must consider these two (among six) queries: (a) If FSIS finds that E. coli 0 1 57:H7 occurs with some regularity on hides and carcasses of feedlot cattle but not on cattle raised under different production practices, should the pathogen be considered a hazard "reasonable likely to occur" only in slaughter and processing operations that use feedlot cattle- (b) How effective are voluntary producer actions in providing animals with reduced levels of E. coli 0157:H7 to plants, and should these voluntary activities, if effective, affect slaughter plants' strategies and FSIS policy-
For market hogs and for cull sows/boars it is presumed, but not known, that similar relationships hold-between handling conditions, stress, shedding (in this case, of Salmonella, Campylobacterjejuni and Yersinia entercolitica) and contamination of external animal surfaces and carcass surfaces-as have been documented for slaughter steers/heifers and for cull cows/bulls. EVALUATION OF ANIMAL HANDLING UNDER PRACTICAL CONDITIONS If a problem is occurring with animal handling at a packing plant, the exact cause of the problem needs to be determined so that the problem can be easily corrected. There are five basic causes of animal handling problems. If the exact cause of an animal-handling problem is known, it can be easily remedied: (1) Distractions which impede animal movement (e.g., sparkling reflections on a wet floor, high pitch noises or seeing people up ahead) can ruin the performance of a well-designed system (Grandin, 1996). (2) Equipment design problems (e.g., a stunning box that is too wide). (3) Lack of employee training or poor supervision of employees. (4) Poor maintenance of equipment (e.g., stunners) or worn, slick floors. (5) Poor condition of animals arriving at the plant (e.g., cripples or non-ambulatory animals). Grandin (1998b,c; 1997) has developed an easy-to-use system for objectively scoring animal handling in slaughter plants; this system can be used to assess animal welfare and handling to maintain good meat quality. One of the most important measurements is scoring of vocalization (Grandin, 1998b,c; 1997). Several studies have shown that squealing in pigs and bellowing in cattle is correlated with physiological stress (Warris et al., 1994; Dunn, 1990). The variables that are scored in the Grandin (1998b,c; 1997) system are: (1) Percentage of animals stunned correctly on the first attempt. (2) Percentage of animals rendered insensible on the bleeding rail. (3) Percentage of animals slipping and falling during handling. (4) Percentage of cattle or swine vocalizing during handling and stunning. (In a pork plant, the percentage of pigs squealing can be estimated and efforts can then be made to make changes that will reduce squealing). (5) Percentage of animals prodded with an electric prod.
Trucking tips to cut cattle bruising, based on material gathered from Beef (1997), Livestock Conservation Institute (1999) and Mies (1999) include: (a) More than 50% of all bruises are due to rough and careless handling. (b) Two-thirds of loin bruises result from loading/unloading from trucks. (c) 7 to 9% of fed cattle have severe (resulting in $20 trim losses) loin bruises. (d) The most common cause of bruising is a hard bump from a protruding object or cattle horn. (e) Cows bruise more easily than do fed steers/heifers. (f) Cattle that go through stockyards have more bruises than do those sold directly to packing plants. (g) Cattle sold on-the-rall have one-half as many bruises as those sold on a liveweight basis. (h) A study of market cows/bulls, at three plants in Texas, revealed that truck driver differences (stops, starts, speeds, cornering) accounted for most of the variability in bruise incidence/severity.
To reduce shrink and stress of cattle during trucking, Livestock Conservation Institute (1999) recommends following these guidelines: (a) During hot weather, haul at night or in early morning. (b) Try not to mix strange animals; fighting during the 24-48 hours prior to slaughter can increase "dark-cutters" in steers and mixing strange bulls can cause "dark cutters" in 90 minutes. (c) Don't ship wet animals when weather is cold, to prevent death due to wind chill. (d) Don't ship animals full of green feed. (e) Provide water up to the time of trucking and upon arrival at the packing plant; half of the shrink of cattle hauled 373 miles is actual carcass (tissue) shrink. (f) Rest-stop cattle if the trip exceeds 48 hours.
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