Market Weight Pigs Research Articles

Effects of distance moved during loading and floor space on the trailer during transport on losses of market weight pigs on arrival at the packing plant1

Effects of distance moved during loading and floor space on the trailer during transport on the incidence of transport losses (dead and nonambulatory pigs) on arrival at the packing plant were evaluated in a study involving 42 loads of pigs (average BW = 131.2 kg, SD 5.05). A split-plot design was used with a 2 x 6 factorial arrangement of the following treatments: 1) distance moved from the pen to the exit of the building [short (0 to 30.5 m) vs. long (61.0 to 91.4 m)] and 2) transport floor space (0.396, 0.415, 0.437, 0.462, 0.489, or 0.520 m(2)/pig). Loading distance treatments (sub-plots) were compared within transport floor space treatments (main plot). Pigs were loaded at the farm using sorting boards and, if necessary, electric goads, transported approximately 3 h to a commercial packing plant and unloaded using livestock paddles. The number of nonambulatory pigs during loading and the number of dead and nonambulatory pigs at the plant were recorded. Nonambulatory pigs were classified as fatigued, injured, or injured and fatigued. In addition, the incidence of pigs exhibiting signs of stress (open-mouth breathing, skin discoloration, and muscle tremors) during loading and unloading was recorded. There were no interactions (P > 0.05) between distance moved and transport floor space treatments. Moving pigs long compared with short distances during loading increased (P < 0.001) the incidence of open-mouth breathing after loading (24.9 vs. 11.0 +/- 1.03%, respectively) and tended to increase the incidence of nonambulatory pigs during loading (0.32 vs. 0.08 +/- 0.09%, respectively; P = 0.09) and of nonambulatory, injured pigs at the plant (0.24 vs. 0.04 +/- 0.07%, respectively; P = 0.06). However, distance moved did not affect other losses at the plant. Total losses at the plant were greater (P < 0.05) for the 3 lowest floor spaces compared with the 2 highest floor spaces, and pigs provided 0.462 m(2)/pig during transport had similar transport losses to those provided 0.489 and 0.520 m(2)/pig (total losses at the plant = 2.84, 1.88, 1.87, 0.98, 0.13, and 0.98 +/- 0.43% of pigs transported, for 0.396, 0.415, 0.437, 0.462, 0.489, and 0.520 m(2)/pig, respectively). These data confirm previous findings that transport floor space has a major effect on transport losses and suggest that these losses are minimized at a floor space of 0.462 m(2)/pig or greater.

How many muscle samples are required to obtain reliable estimations of muscle fibre characteristics from pig longissimus muscle?

In order to investigate the reliability of muscle fibre trait estimations of pig longissimus muscle and to derive the minimum number of samples required per muscle cross-section and animal, intraclass correlation coefficients (ICC, ϑ ˆ ) were obtained by one-way analysis of variance. From each of 23 market weight pigs five samples, evenly distributed over the muscle cross-sectional area at the 12th/13th rib level, were taken and analyzed for various muscle fibre traits. The number of samples required per muscle cross-section was found to be different between selected fibre traits, ranging from a minimum of three (for number of muscle fibres) to a maximum of five or more (for mean fibre area, fibre type composition and relative area occupied by each fibre type). These findings should be taken as a recommendation, but their usefulness will depend upon the goal and conditions of future experiments.

Effect of floor space during transport of market-weight pigs on the incidence of transport losses at the packing plant and the relationships between transport conditions and losses1

Data on 74 trailer loads of finishing pigs (mean BW = 129.0, SEM = 0.63 kg) from wean-to-finish buildings on 2 farms within 1 production system were collected to investigate the effect of amount of floor space on the trailer (0.39 or 0.48 m2/pig) during transport on the incidence of losses (dead and nonambulatory pigs) at the packing plant and to study the relationships between transport conditions and losses. Pigs were loaded using standard commercial procedures for pig handling and transportation. Two designs of flat-deck trailers with 2 decks were used. Floor space treatments were compared in 2 similarly sized compartments on each deck of each trailer type. Differences in floor space were created by varying the number of pigs in each compartment. The incidence of nonambulatory pigs at the farm during loading and at the plant after unloading, average load weight, load number within each day, event times, and temperature and relative humidity in the trailer from loading to unloading were recorded. Of the 12,511 pigs transported, 0.26% were non-ambulatory at the farm, 0.23% were dead on arrival, and 0.85% were nonambulatory at the plant. Increasing transport floor space from 0.39 to 0.48 m2/pig reduced the percentage of total nonambulatory pigs (0.62 vs. 0.27 +/- 0.13%, respectively; P < 0.05), nonambulatory, noninjured pigs (0.52 vs. 0.15 +/- 0.11%, respectively; P < 0.01), and total losses (dead and nonambulatory pigs) at the plant (0.88 vs. 0.36 +/- 0.16%, respectively; P < 0.05) and tended to reduce dead pigs (0.27 vs. 0.08 +/- 0.08%, respectively; P = 0.06). However, transport floor space did not affect the percentage of nonambulatory, injured pigs at the plant. Nonambulatory pigs at the farm were positively correlated with relative humidity during loading and load number within the day (r = 0.46 and 0.25, respectively; P < 0.05). The percentage of total losses at the plant was positively correlated to waiting time at the plant, unloading time, and total time from loading to unloading (r = 0.24, 0.51, and 0.36, respectively; P < 0.05). Average temperature during loading, waiting at the farm, transport, waiting at the plant, unloading, and average pig weight on the trailer were not correlated to losses. These results suggest that floor space per pig on the trailer and transport conditions can affect transport losses.

Comparison of dietary selenium fed to grower-finisher pigs from various regions of the United States on resulting tissue Se and loin mineral concentrations1,2,3

A study was conducted to evaluate the mineral content of pork tissue with particular emphasis on Se between various states (regions) having different diet (grain) indigenous Se concentrations. The study involved 19 states in the north, central, and southern regions of the United States, with committee members of NCR-42 and S-1012 (formerly S-288). A total of 62 pigs were used, with collaborators sending 100-g samples each of loin, heart, and liver, and a 3- to 4-g sample of hair (collected along the topline) from two to five market-weight pigs to a common laboratory for analysis. Diets at each station were formulated with locally purchased soybean meal and grain that was either grown or normally fed to pigs within their state. Tissues were analyzed for Se, but only the loin was analyzed for the macro- and micromineral elements. Correlation of dietary minerals to the tissue element was determined. The results demonstrated differences in tissue Se among states (P < 0.01), with high correlations of dietary Se to loin (r = 0.84; P < 0.01), heart (r = 0.84; P < 0.01), liver (r = 0.83; P < 0.01), and hair Se (r = 0.90; P < 0.01) concentrations. The correlation of hair Se to the Se concentration of loin, heart, and liver tissues was high (r > 0.90; P < 0.01). States in the west-central region of the United States and west of the Mississippi river had higher dietary Se and tissue Se concentrations than states in the eastern section of the Corn Belt, east of the Mississippi river, and along the East Coast. Generally, states did not differ greatly in their loin macro- and micromineral concentrations. The simple correlation of dietary minerals to their corresponding loin mineral concentration was generally non-significant, but most macrominerals had decreasing mineral concentrations when the dietary mineral level was higher. These results indicate that regional differences in tissue Se were influenced more by the indigenous Se content of the diet (grain) fed to the pigs than from sodium selenite.

Associations between On-Farm and Slaughter Plant Detection of Salmonella in Market-Weight Pigs

Thirty swine production units in the midwestern United States were studied to assess the relationship of herd-level prevalence of Salmonella on the farm prior to slaughter versus at slaughter. Fecal samples were collected from 30 pigs on each farm within 48 h of slaughter, and 30 ileocecal lymph node samples were collected in the same shipment cohort at slaughter. Samples were cultured by conventional methods, and Salmonella identity was confirmed by serotyping. Overall, 11.7% (n = 105) of the fecal samples and 14.9% (n = 133) of the ileocecal lymph node samples were positive for Salmonella. Seventeen of the farms (56.7%) had one or more positive fecal samples, and 24 (80.0%) had one or more positive ileocecal lymph node samples. Twenty-four recognized serotypes and three additional distinct antigenic types were identified. Among all isolates, 56.5% had serotypes that were duplicated both on the farm and at slaughter for a particular cohort, whereas the remaining samples lacked a duplicate serotype in the other sample type. There was a positive correlation in the prevalence of Salmonella between fecal samples and ileocecal lymph node samples (Spearman's ρ = 0.75; 95% confidence interval [CI], 0.62 to 0.89). Linear regression analysis was used to identify two farms that biased the regression estimates. Excluding these farms, 62% of the variance in farm slaughter Salmonella prevalence was accounted for by on-farm prevalence. The analyses suggest that the prevalence of Salmonella spp. at slaughter can be predicted from preslaughter on-farm sampling and vice versa.

Conjugated linoleic acid (CLA) during gestation and lactation does not alter sow performance or body weight gain and adiposity in progeny

The objective of this study was to determine the long-term effects of conjugated linoleic acid (CLA) in pigs exposed to CLA during fetal and neonatal growth. Sows were fed a diet with 0.83% soy oil or 0.83% CLA-60 containing 60% active CLA isomers from either d 40 (group 1; CON n = 8, CLA n = 6) or d 75 (group 2; CON n = 8, CLA n = 8) of gestation through weaning on d 28. Within group 1, one male and one female piglet per litter (CON n = 6, CLA n = 5) were sacrificed within 24 hours of birth (d 0) and body weights recorded. Semitendinosus muscle, subcutaneous adi- pose tissue and organs, including heart, liver, lung, kidney, brain were weighed and tissue samples were frozen. Two average weight barrows and two gilts per litter were weaned and fed standard diets without added CLA until market weight. CLA did not alter sow's feed intake during gestation or lactation, body weight or backfat thickness, and litter size and weight at birth (P > 0.05). CLA decreased newborn pig heart, but not backfat or semitendinosus muscle weights relative to their body weights (d 0). CLA decreased pre-weaning weight in selected piglets but this was not maintained post-weaning. CLA decreased total milk fat by 17% (P < 0.01) and resulted in an increase in the relative amount of saturated fatty acids and a decrease in the relative amount of unsaturated fatty acids in milk on d 21 of lactation (P < 0.05). Decreases in growth rates until d 14 may be due to decreased fat in sow's milk since growth rate and body weight of selected progeny did not differ post-weaning. Serum from newborn CLA pigs suppressed relative preadipocyte number and did not change lipid filling in stromal-vascular cell cultures. The response to this serum was greater in females than in males (PDiet = 0.04; PDiet × Gender = 0.04). Thus, there do not seem to be any long-term effects on growth and body composition of market weight pigs given 0.5% CLA through weaning that would be beneficial in a production scheme. conjugated linoleic acid / gestation / lactation / porcine / adipose

The Association between Cleaning and Disinfection of Lairage Pens and the Prevalence of Salmonella enterica in Swine at Harvest

A series of four field trials were conducted to evaluate the ability of a cleaning and disinfection procedure in swine lairage pens to reduce the prevalence of Salmonella enterica in slaughtered pigs. A cleaning and disinfection procedure was applied to lairage pens at a large Midwest abattoir. Each trial consisted of a cleaned (alkaline chloride detergent) and disinfected (H2O2 plus peracetic acid sanitizer) pen (treated) and a control pen, each holding 90 to 95 pigs for 2 to 3 h before slaughter. Ileocecal lymph nodes, cecal contents, and rectal contents were collected from 45 pigs from each study pen at harvest and cultured for S. enterica. In all trials, cleaning and disinfection reduced the prevalence of S. enterica–positive floor swabs in the treated pen (P < 0.05). However, the postharvest prevalence of S. enterica–positive pigs varied between trials. In trial 1, there was no significant difference in the prevalence of S. enterica in pigs between treatment and control groups. In trials 2 and 3, the prevalence of S. enterica was higher in pigs from treated pens versus pigs from control pens (91% versus 40%, P < 0.0001, and 91% versus 24%, P < 0.0001, respectively). In trial 4, the prevalence of S. enterica was lower in pigs from treated pens compared with pigs from control pens (5% versus 42%, P < 0.0001). This study indicates that cleaning and disinfection effectively reduces the amount of culturable S. enterica in lairage pens, but the ability of cleaned and disinfected pens to reduce the prevalence of S. enterica in market-weight pigs remains inconclusive.

Effects of Sex and Market Weight on Performance, Carcass Characteristics and Pork Quality of Market Hogs

An experiment was conducted to examine the effects of sex and market weight on performance, carcass characteristics and pork quality. A total of 224 crossbred pigs (initially 26.64 kg BW) were allotted in a 2×4 factorial arrangement in a randomized complete block (RCB) design. The variables were sex (gilts and barrows) and different market weights (100, 110, 120 and 130 kg). Average daily gain (ADG) and average daily feed intake (ADFI) were significantly higher (p<0.01) in barrows than gilts, ADFI and feed conversion ratio (FCR) increased as body weight increased (p<0.05). Gender differences were observed in carcass characteristics. Backfat thickness and drip loss were greater in barrows (p<0.01), while loin eye area (p<0.01), flavor score (p<0.05) and lean content (p<0.001) were higher in gilts. Carcass grade and water holding capacity were the highest in 110 kg market weight pigs. The 100 kg market weight pigs showed lower juiciness, tenderness, shear forces and total palatability than the other market weights (p<0.01). Hunter values (L*, a* and b*) were increased as market weight increased (p<0.05). Hunter a* value was greater in gilts (p<0.01) but L* value and b* value were not affected by sex of pigs. Net profit ((carcass weight×price by carcass grade)-(total feed cost+cost of purchased pig)) was higher in gilts than barrows (p<0.01), and was higher (p<0.05) in the pigs marketed at 110 and 120 kg market weight compared with 100 kg market weight. These results demonstrated that gilts showed higher carcass characteristics, pork quality, feed cost per kg body weight gain and net profit compared with barrows. Moreover, 110 or 120 kg body weight would be the recommended market weight based on pork quality and net profit for swine producers. (Asian-Aust. J. Anim. Sci. 2004. Vol 17, No. 10 : 1452-1458)

Actinobacillus pleuropneumoniae in Thai pig herds. Prevalence of serum antibodies and relation to performance.

The aim of the study was to investigate the prevalence of Actinobacillus pleuropneumoniae infections in market weight pigs in Thailand. ELISA systems employing purified lipopolysaccharide antigens were used to detect antibodies in 549 serum samples collected from pigs of 22 herds. Relevant cut-off values were established from three herds defined seronegative. Serum antibodies were detected to all serotypes except serotype 10. Almost 60% of the samples were seropositive to at least one serotype and 45% of the pigs were seropositive to more than one serotype. Antibodies to the cross-reacting serotypes 1, 9 or 11 were found in 29% of the pigs. Other common serotypes included the cross-reacting serotypes 3, 6 or 8 (26% seropositive pigs) and serotype 5a (also 26%). Antibodies to serotypes 2, 5b and 12 were low in prevalence (<10%). Three herds were regarded to be seronegative and six to have a low pathogen load with respect to the prevalence of seropositive pigs. The remaining 13 herds had a high incidence of pigs with antibodies to A. pleuropneumoniae, dominated by serotypes 1-9-11 and 5a (n = 6), serotypes 3-6-8, and 5a (n = 4) or 1-9-11, 3-6-8, 5a and 4-7 (n = 3). A low pathogen load with respect to A. pleuropneumoniae, as well as small herd size and age-segregated rearing, tended to improve the performance of growers.

High Prevalence of Viable Toxoplasma gondii Infection in Market Weight Pigs from a Farm in Massachusetts

High Prevalence of Viable Toxoplasma gondii Infection in Market Weight Pigs from a Farm in Massachusetts

High prevalence of viable Toxoplasma gondii infection in market weight pigs from a farm in Massachusetts.

The ingestion of uncooked infected meat is considered important in the epidemiology of Toxoplasma gondii infection in humans and little is known of the prevalence of viable T. gondii in meat used for human consumption in the United States. In the present study, viable T. gondii was isolated from 51 out of 55 pigs destined for human consumption. Hearts and tongues (500 g) from fifty-five 6-mo-old pigs from a farm in Massachusetts were bioassayed for T. gondii by feeding them to T. gondii-free cats. Feces of these cats were examined for shedding of T. gondii oocysts. Fifty-one of 55 cats fed pig tissues each shed 25-810 million T. gondii oocysts in their feces. Two of these cats consumed tissues of pigs that were shown to be seronegative with the Sabin-Feldman dye test, the modified agglutination test, and the Western blot. Results indicate that until examination of meat for T. gondii infection is implemented in slaughterhouses, all meat should be cooked according to industry guidelines before human consumption.

Salmonella enterica infections in market swine with and without transport and holding.

The objective of this study was to compare, by using identical sample types, the Salmonella enterica prevalences and serovar diversities between pigs necropsied on the farm and those necropsied at the abattoir after transport and holding. We necropsied 567 market weight pigs (>70 kg) from six herds. Pigs were alternately assigned to be necropsied on the farm or at the abattoir. One-half of the group was sent in clean, disinfected trailers to slaughter at a commercial abattoir. After transport (mean distance, 169 km) and 2 to 3 h of holding in antemortem pens, these pigs were necropsied. The 50 pigs remaining on the farm were necropsied the following day. The same sample types and amounts were collected for S. enterica culture at both locations. Results show a sevenfold-higher (P < 0.001) S. enterica isolation rate from pigs necropsied at the abattoir (39.9%; 114 of 286) than from those necropsied on the farm (5.3%; 15 of 281). This difference was also observed for each individual herd. All sample types showed a significantly higher prevalence when comparing abattoir to on-farm collection, respectively: lymph nodes, 9.15 versus 3.6%; cecal contents, 13.6 versus 1.8%; 1 g of fecal matter, 25.2 versus 0.7%. Recovery of additional serovars at the abattoir suggests the pigs are receiving S. enterica from extra-farm sources. This study demonstrates that rapid infection during transport, and particularly during holding, is a major reason for increased S. enterica prevalence in swine. This finding identifies the holding pen as an important S. enterica control point in the pork production chain.

Injection of neonatal piglets with dexamethasone stimulates leptin mRNA expression and reduces the stress response in market weight pigs

AbstractNeonatal piglets were given three daily injections of dexamethasone at 1 mg/kg body weight to examine if their stress response and carcass fat distribution at a 120-kg market weight could be altered. The daily acute injections tended to increase the amount of muscle and adrenal leptin mRNA expression (P &lt; 0·1) for 1 and 3 days after the end of the treatment but had no effect on the amount of glucocorticoid receptor mRNA. The treated animals had a 19% lower adult stress response to transport than the controls as measured by salivary cortisol levels. There was no significant change in the treated animals’ carcass and meat quality traits at market weight. However, a trend towards more marbling fat and carcass backfat were seen in the dexamethasone treated pigs at market weight.

Conjugated linoleic acid depresses the δ desaturase index and stearoyl coenzyme A desaturase enzyme activity in porcine subcutaneous adipose tissue

Conjugated linoleic acid (CLA) has been shown to have an effect on subcutaneous fatty acid composition and has been reported to decrease stearoyl coenzyme A desaturase (SCD) activity by decreasing mRNA expression and(or) catalytic activity in rodents and rodent cell lines. This investigation was designed to study the effects of CLA, corn oil, or beef tallow supplementation on s.c. adipose tissue fatty acid composition, adiposity, SCD enzyme activity, and the delta9 desaturase index in piglets. Eighteen crossbred barrows 16 to 18 d of age were adapted to diet for 1 wk and then assigned randomly to one of three treatments: 1.5% added CLA, 1.5% added corn oil, or 1.5% added beef tallow. Barrows were penned individually and fed the supplemental oils for 35 d (to 25.6 +/- 0.6 kg BW). Subcutaneous adipose tissue samples were obtained after slaughter. Fatty acid composition of the s.c. adipose tissue differed for each fatty acid measured due to diet with the exception of 18:3. The concentrations of CLA trans-10, cis-12 and cis-9, trans-11 were elevated from nondetectable to 1.62 and 2.52 g/100 g lipid, respectively (P < 0.001 for both isomers). Conjugated linoleic acid decreased the delta9 desaturase index (P < 0.01) and SCD enzyme activity, expressed as nanomoles of palmitate converted to palmitoleate/(7 min x g of tissue) (P = 0.075) and nanomoles of palmitate converted to palmitoleate/(7 min 105 cells) (P= 0.056). Tallow-fed pigs had a greater proportion of large adipocytes (> 700 pL) and the greatest SCD activity. These data provide the first direct evidence that dietary CLA depresses SCD enzyme activity in porcine adipose tissue, which may in part be responsible for the depression of adiposity by CLA observed by others in market weight pigs.

The isolation and function of porcine islets from market weight pigs.

The efficacy of clinical islet transplantation has been demonstrated with autografts, and although islet allografts have established insulin independence in a small number of IDDM patients, the treatment is confounded by the necessity of immunosuppression. the lack of donor tissue, and recurring islet immunogenicity. These limitations underscore a need to develop therapies to serve the large population of diabetic patients. Porcine islet xenotransplantation, together with a successful immune intervention strategy, may provide the necessary clinical alternative. However, a major obstacle in evaluating this approach has been the difficulty of obtaining adequate volumes of functional islet tissue from pigs. Donors of market weight are preferable to retired breeders due to their abundance, lower animal and husbandry costs. and are more suitable to meet regulatory guidelines for donor tissue for xenotransplantation. We describe a simple isolation procedure that following purification yields a mean of 350,000 IE, corresponding to 179 units of insulin and 1.8 mg of DNA with an islet purity and viability in excess of 85% (n = 317 isolations). In both short- and long-term cell cultures, porcine islets demonstrated glucose-responsive insulin secretion. However, this secretion is density dependent, which may have significant consequences in the development of immunoisolation technologies to support porcine islet xenotransplantation. Following implantation into diabetic nude mice, porcine islets remained functional in excess of 1 year. Implantation of a bioartificial pancreas containing porcine islets into pancreatectomized dogs provided significant clinical benefit with an improved diabetic condition. Finally, secretagogue-induced insulin release was demonstrated in vitro from these devices after removal from immunocompetent recipients. Immunohistochemical staining identified well-granulated islets following long-term implantation in both the rodent and canine models. This study demonstrates the ability to isolate porcine islets in clinically relevant numbers from market animals, which survive and remain functional for prolonged periods of time in an immune-deficient or immunoprotected environment.

Utilizing infrared thermography to predict pork quality (2001)

Three experiments using 63 pigs were conducted to determine if infrared thermography could segregate pigs based on subsequent pork quality. Pigs were subjectively classified as either “hot” or “normal” based on infrared surface temperature of the loin region prior to slaughter. In the first experiment 18 market weight pigs were transported, imaged by infrared thermography and slaughtered immediately after 1 to 4 h of lairage. Differences in meat quality were detected; hot pigs had lower a* (less red) and chroma (less intense red color) values, and higher hue angle (less red/more yellow) values, all of which indicate paler muscle color. In the second experiment, 27 market weight pigs were transported, held in lairage for 12 to 16 h, imaged by infrared thermography, and then slaughtered. In the third experiment, 18 market weight pigs were transported, imaged by infrared thermography, held in lairage for 12 to 16 h, and then slaughtered. Regardless of the time infrared images were taken, no meat quality differences between hot and normal pigs were detected when pigs were held in lairage for 12 to 16 h. These data suggest that measurement of live animal surface temperature by infrared thermography may allow for detection of poor meat quality if pigs are slaughtered without extended lairage.; Swine Day, Manhattan, KS, November 15, 2001

Analysis and pharmacokinetics of cyclopiazonic acid in market weight pigs.

The pharmacokinetic behavior of cyclopiazonic acid (CPA) was determined in market weight pigs using a competitive indirect ELISA developed for the determination of the mycotoxin in various biological matrices. Sample preparation for corn and skeletal muscle was achieved with a single extraction and recoveries of 53+/-6% over the effective range of the standard curve. The detection limit of CPA was 1 ppb in plasma, which required no extraction, and 20 ppb in corn and skeletal muscle with average intra- and interassay CV of 11 and 23%, respectively. Levels of CPA contamination in corn grown and stored in Michigan were unremarkable compared with published toxicity thresholds; the highest level of CPA found in any sample was 47 ppb. In pigs given a 20-mg i.v. bolus, CPA distributed rapidly among three compartments, with an overall volume of distribution (49 L) nearly equivalent to total body water. Cyclopiazonic acid was eliminated with a half-life of 24 h. Estimates of these pharmacokinetic parameters were supported by the achievement of steady-state plasma CPA levels within 6 d in pigs consuming a diet containing 10 ppm CPA, and by measured concentrations of CPA in plasma (410+/-44 ng/mL) and skeletal muscle (469+/-86 ng/ g). From these and other data, we concluded that the threat of CPA toxicity to livestock from consumption of cereal grains or to humans from consumption of animal products is minimal.

Sex effects on fat hardness meter readings of market weight pigs

A portable fat hardness meter (FHM) was used to measure the firmness of the inner fat layer on a cross sectional surface over the second thoracic vertebra of pork carcasses. This was a 4-yr study with data collected on 141 barrows, 214 gilts and 270 boars. A statistical model, after adjusting for year and breed of sire (i.e., Lacombe, Landrace, Yorkshire), included sex, linear and quadratic covariates for carcass growth rate (i.e., carcass weight per day of age), a linear covariate for leanness (i.e., carcass fat thickness or dissectible lean) within sex, and a linear by linear covariate of growth rate by leanness, and was used to describe a response surface with fat hardness. No pigs in this study had extremely soft fat (i.e., FHM &lt; 420). However, 4, 2 and 0% of the boars, gilts and barrows had very soft fat (i.e., FHM 420–619). While 10% of the barrows had extremely hard (i.e., FHM &gt; 970) or very hard fat (i.e., FHM 930–970), only 1% of the gilts had very hard fat, and no boars were included in these classes. Relative to the FHM readings of gilts (i.e., 805 ± 6.2), boars (i.e., 780 ± 5.6) had softer fat (P = 0.0002) while barrows (i.e., 835 ± 7.4) had harder fat (P = 0.0001). The majority of boars had slightly soft fat (i.e., FHM 750–829) while gilts and barrows had slightly hard (i.e., FHM 830–889) fat. Regression coefficients for growth rate on fat hardness were homogeneous among the sexes. As growth rate increased fat hardness increased, but was attenuated by a negative quadratic term. Increased leanness was linearly antagonistically related with fat hardness. There were differential effects across sexes (P = 0.0261). As leanness increased, fat became softer among boars and gilts compared with barrows. A linear by linear interaction of growth rate with leanness attenuated this effect. Holding growth rate constant, a 25% reduction of carcass fatness would be expected to reduce fat hardness by 40, 35 and 20 points in boars, gilts, and barrows, respectively. While selection for increased lean growth may result in some degradation in fat quality, the trend towards marketing heavy pigs as they become leaner should be sufficient to offset this effect. Key words: Swine, carcass, grading, growth rate, fat, lean

The effect of daily injections of prolonged-release implants of recombinant porcine somatotropin on behaviour in market-weight pigs

Animal behaviour frequency data were collected on 92 ad libitum fed Yorkshire pigs (96 kg) allocated to one of three recominant porcine somatotropin (rpST) treatment groups (36 prolonged-release rpST implants at 2 mg d−1 pig−1, 40 daily injection rpST pigs at 2 mg d−1, and 16 control or sham-injected pigs). From time-lapse recordings of animal behaviour, ethogram analysis revealed that of the 10 behaviours studied, investigative behaviour, was the only trait affected by rpST treatment, with the daily injected pigs showing a slightly lowered percentage of time (P &lt; 0.05) spent investigating their pen (7.3% d−1 vs. 13.6% d−1 in control and 10.1% d−1 in prolonged-release treatment group). Key words: Behaviour, porcine somatotropin, pigs

Association between growth indicators and volume of lesions in lungs from pigs at slaughter

Summary Conflicting findings exist among studies on the effect of pneumonia on growth in pigs. We determined the extent of pneumonia in market-weight pigs by use of an objective, volumetric method and linear regression analyses of mean daily gain and days-to-slaughter weight on the percentage of pneumonic lung. In a range of extent of pneumonia between 1.33 and 70.44%, a 10% increase in the volume of pneumonic lung was associated with a decrease in mean daily gain by 41.1 g and a 16.7-day increase in number of days to a slaughter weight of 104.5 kg.