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The purpose of this study was to determine the association of production factors with stayability to parity 4 (STAY4) under controlled experimental conditions. Data were from 2,293 female pigs, sampled from 6 genetic lines that were entered into the National Pork Producers Council Maternal Line National Genetic Evaluation Program. Genetic lines evaluated included Newsham (NH), National Swine Registry (NSR), American Diamond Swine Genetics (ADSG), Danbred (DAN), and 2 Dekalb-Monsanto lines (DK44 and GPK347). Stepwise logistic regression was utilized in the analysis of STAY4. All effects were nested within genetic line. Categorical effects in the model were arrival date to the wean-to-finish unit (entry date) and breed-gestation-farrowing facility (farm). Continuous effects in the model were gilt backfat, LM depth, ADG, age at puberty, age at first farrowing, and traits recorded before the last litter of the sow (prefarrow backfat, number born alive, number weaned, litter weaning weight, lactation feed intake, lactation backfat loss, and lactation length). Factors significant for STAY4 included farm, entry date, age at first farrowing, ADG, gilt backfat, and lactation before removal effects, as well as feed intake, number born alive, and lactation length. Age at first farrowing and lactation feed intake affected all genetic lines. Regression coefficients for STAY4 on age at first farrowing were −0.014, −0.022, −0.017, −0.016, −0.011, and −0.021 (all P< 0.05), respectively, for NH, NSR, ADSG, DK44, GPK347, and DAN genetic lines. Regression coefficients for STAY4 on lactation feed intake were 0.043, 0.049, 0.051, 0.061, 0.120, and 0.097 (all P< 0.05), respectively, for NH, NSR, ADSG, DK44, GPK347, and DAN females. Age at puberty, age at first farrowing, and lactation feed intake had the greatest effect on STAY4.

Design of breeding programs requires knowledge of variance components that exist for traits included in specific breeding goals and the genetic relationships that exist among traits of economic importance. A study was conducted to evaluate direct and correlated genetic responses to selection for intramuscular fat (IMF) and to estimate genetic parameters for economically important traits in Duroc swine. Forty gilts were purchased from US breeders and randomly mated for 2 generations to boars available in regional boar studs to develop a base population of 56 litters. Littermate pairs of gilts from this population were randomly assigned to a select line (SL) or control line (CL) and mated to the same boar to establish genetic ties between lines. In the SL, the top 10 boars and 75 gilts were selected based on IMF EBV obtained from a bivariate animal model that included IMF evaluated on the carcass and IMF predicted via ultrasound. One boar from each sire family and 50 to 60 gilts representing all sire families were randomly selected to maintain the CL. Carcass and ultrasound IMF were both moderately heritable (0.31 and 0.38, respectively). Moderate to high genetic relationships were estimated among carcass backfat and meat quality measures of IMF, Instron tenderness, and objective loin muscle color. Based on estimates obtained in this study, more desirable genetic merit for pH is associated with greater genetic value for loin color, tenderness, and sensory characteristics. Intramuscular fat measures obtained on the carcass and predicted using ultrasound technology were highly correlated (rg= 0.86 from a 12-trait analysis; rg= 0.90 from a 5-trait analysis). Estimated genetic relationships among IMF measures and other traits evaluated were generally consistent. Intramuscular fat measures were also genetically associated with Instron tenderness and flavor score in a desirable direction. Direct genetic response in IMF measures observed in the SL corresponded to a significant decrease in EBV for carcass loin muscle area (−0.90 cm2per generation) and an increase in carcass backfat EBV (0.98 mm per generation). Selection for IMF has led to more desirable EBV for objective tenderness and has had an adverse effect on additive genetic merit for objective loin color.

A study was conducted to evaluate the efficacy of selection for intramuscular fat (IMF) in a population of purebred Duroc swine using real-time ultrasound. Forty gilts were purchased from US breeders and randomly mated for 2 generations to boars available in regional boar studs, resulting in a base population of 56 litters. Littermate pairs of gilts from this population were randomly assigned to a select line (SL) or control line (CL) and mated to the same sire to establish genetic ties between lines. At an average BW of 114 kg, a minimum of 4 longitudinal ultrasound images were collected 7 cm off-midline across the 10th to 13th ribs of all pigs for the prediction of IMF (UIMF). At least 1 barrow or gilt was slaughtered from each litter, and carcass data were collected. A sample of the LM from the 10th to 11th rib interface was analyzed for carcass IMF (CIMF). Breeding values for IMF were estimated by fitting a 2-trait (UIMF and CIMF) animal model in MATVEC. In the SL, selection in each subsequent generation was based on EBV for IMF with the top 10 boars and top 75 gilts used to produce the next generation. One boar from each sire family and 50 to 60 gilts representing all sire families were randomly selected to maintain the CL. Through 6 generations of selection, an 88% improvement in IMF has been realized (4.53% in SL vs. 2.41% in CL). Results of this study revealed no significant correlated responses in measures of growth performance. However, 6 generations of selection for IMF have yielded correlated effects of decreased loin muscle area and increased backfat. Additionally, the SL obtained more desirable objective measures of tenderness and sensory evaluations of flavor and off-flavor. Meat quality characteristics of pH, water holding capacity, and percent cooking loss were not significantly affected by selection for IMF. Selection for IMF using real-time ultrasound is effective but may be associated with genetic ramifications for carcass composition traits. Intramuscular fat may be used in purebred Duroc swine breeding programs as an indicator trait for sensory traits that influence consumer acceptance; however, rapid improvement should not be expected when simultaneous improvement in other trait categories is also pursued.

A study was conducted to evaluate differences in performance and in carcass composition and tissue deposition rates between purebred Duroc pigs sired by boars currently available and those sired by boars from the mid-1980s. Two lines were developed by randomly allocating littermate and half-sib pairs of females to matings by current time period (CTP) or old time period (OTP) boars. Pigs from 2 replications were placed on test at a group mean BW of 63.5 kg. Serial ultrasonic measurements of the 10th-rib LM area (LMA), off-midline backfat (BF10), and intramuscular fat percentage (IMF) were collected every 2 wk in the first replication and used to assess deposition rate differences. Off-test ultrasonic LMA, BF10, and IMF measurements from a total of 557 pigs from 23 CTP sires and 232 pigs from 15 OTP sires across 2 replications and at a mean BW of 109 kg were evaluated. All available barrows and randomly selected gilts (n = 277) were sent to a commercial abattoir, and carcass measurements of 10th-rib backfat, last-rib backfat, last lumbar backfat, and LMA were collected. Analysis of serial backfat measurements revealed a linear relationship between back-fat and BW between 73 and 118 kg for pigs from both time periods. Pigs sired by OTP boars deposited more backfat (P< 0.05) at a faster rate than pigs sired by CTP boars over the entire test period. A curvilinear cumulative tissue deposition pattern was revealed for ultrasonically estimated LMA and IMF within both time periods. Significant linear and quadratic regression coefficient differences between lines indicated that pigs sired by CTP boars deposited more LMA and less IMF per kilogram of BW gain than pigs sired by OTP boars. Pigs sired by CTP boars had more LMA and less BF10 (P< 0.05), whereas pigs sired by OTP boars had more IMF (P= 0.04). Carcass evaluation revealed more (P< 0.01) carcass measurements of LMA and less (P< 0.05) carcass measurements of 10th-rib backfat, carcass measurements of last-rib backfat, and carcass measurements of last lumbar backfat for pigs sired by CTP boars. No difference (P> 0.05) between the time periods was found for ADG over the entire test period. Results from this study illustrate that significant progress in carcass composition has been realized within the Duroc breed since the mid-1980s. The long-term selection response in carcass leanness has also resulted in changes in deposition rates of correlated traits such as LMA and IMF.

Data from the National Pork Producers Council Maternal Line National Genetic Evaluation Program were used to compare longevity of sows from 6 commercial genetic lines and to estimate the phenotypic associations of sow longevity with gilt backfat thickness, ADG, age at first farrowing, litter size at first farrowing, litter weight at first farrowing, average feed intake during lactation, and average backfat loss during lactation. The lines evaluated were American Diamond Genetics, Danbred North America, Dekalb-Monsanto DK44, Dekalb-Monsanto GPK347, Newsham Hybrids, and National Swine Registry. The data set contained information from 3,251 gilts, of which 17% had censored longevity records (sows lived longer than 6 parities). The line comparison was carried out by analyzing all lines simultaneously. Because the survival distribution functions differed among genetic lines, later analyses were carried out separately for each genetic line. All analyses were based on the non-parametric proportional hazard (Cox model). Dekalb-Monsanto GPK347 sows had a lower risk of being culled than sows from the other lines. Moreover, the shape of the survival distribution function of the Delkab-Monsanto GPK347 line was different from the other 5 lines. The Dekalb-Monsanto 347 line had lower culling rates because they had lower gilt reproductive failure before the first parity than gilts from the other lines. Within line, sows with lower feed intake and greater backfat loss during lactation had a shorter productive lifetime. Thus, producers should implement management practices having positive effects on sow lactation feed intake. Additionally, the swine genetics industry is challenged to simultaneously improve efficiency of gain of their terminal market pigs and to obtain high feed intake during lactation of their maternal lines for future improvement of sow longevity. Recording sow feed intake and backfat loss during lactation in nucleus and multiplication breeding herds should be considered. Between-line differences in this study indicate that it is possible to select for sow longevity, but more research is needed to determine the most efficient selection methods to improve sow longevity.

A study was conducted to evaluate differences in meat and eating quality traits between purebred Duroc pigs sired by boars currently available and pigs sired by boars from the mid 1980s. Two lines were developed by randomly allocating littermate and half-sib pairs of females to matings by current time period (CTP) or old time period (OTP) boars. Matings by CTP boars were made using fresh semen, and matings by OTP boars were via frozen semen. All available barrows and randomly selected gilts were sent to a commercial abattoir and used for meat and eating quality evaluation. A total of 178 pigs from 23 CTP sires and 99 pigs from 15 OTP sires, across 2 replications and at a mean live weight of 109 kg, were slaughtered and analyzed. Chemical intramuscular fat percentage was determined by lab analysis of a slice from the LM at the 10th rib. Additional meat and eating quality traits measured on the LM were Minolta reflectance and Hunter L color (24 h); pH (24 h and 7 d); water-holding capacity; subjective visual scores for color, marbling, and firmness (48 h); Instron tenderness; cooking loss; and trained sensory panel evaluations (7 d). Time period differences were assessed by use of a mixed model that included fixed effects of sire time period, replication, sex, contemporary group, and the interaction of sex × time period. The random effect of dam and the random effect of sire nested within time period were also included. Loins from pigs sired by OTP boars had greater intramuscular fat (3.48 vs. 3.09%) and visual marbling scores (3.54 vs. 3.07), required less Instron force (5.31 vs. 5.98 kg) to compress, and had darker visual color scores (4.09 vs. 3.87) compared with loins from pigs sired by CTP boars (P< 0.05). No differences were observed between time periods for Minolta reflectance, Hunter L (24 h), water-holding capacity, pH (24 h and 7 d), or subjective firmness scores. Trained sensory evaluations revealed more pork flavor and less off-flavor (P< 0.05) for OTP-sired pigs; however, no differences in tenderness score, juiciness score, chewiness score, or cooking loss were found between lines. Long-term selection response in carcass composition has been at the expense of meat and eating quality traits.

A study was conducted to evaluate the effect of dietary grain sources on various compositional and quality characteristics of pork from pigs reared in a commercial environment. Pigs were fed 1 of 5 dietary treatments containing the following single or blended grain sources throughout most of the grow-finish period: 1) yellow corn, 2) white corn, 3) 1/3 yellow corn and 2/3 white corn, 4) 2/3 yellow corn and 1/3 white corn, and 5) barley. Pigs were from 2 sire genetic types, Duroc and Hampshire × Duroc, mated to PIC 1055 females. A total of 1,040 pigs were included in the study in a 2 × 2 × 5 factorial arrangement with 2 genetic types, 2 sexes (barrows and gilts), and 5 dietary treatments. Eight pigs were randomly selected from each pen of 26 (n = 320) for meat and fat quality evaluation. Pigs were 27.6 kg at the beginning of the experiment and were fed to 130.2 kg. All animals were held overnight at a commercial abattoir before slaughter. One whole, skin-on, boneless loin was collected from each carcass and held at −1°C in a cryovac-sealed bag at the Iowa State University Meat Laboratory. At 25 to 27 d postslaughter, loins were evaluated for meat and fat quality. Dietary treatment had no effect (P> 0.05) on 24-h pH, sensory tenderness, sensory chewiness, Instron tenderness, loin purge, or cook loss. At 25 to 27 d postslaughter, pigs fed diet 4 had a greater (P< 0.05) loin pH than pigs fed diet 1, and diets 2, 3, and 5 were not different from all treatment means. Pigs fed diet 4 had a greater (P< 0.05) Japanese color score than pigs fed diets 2, 3, and 5, and diet 1 was not different from all treatment means. Pigs fed diet 3 had a greater percentage of intramuscular fat than pigs fed diets 1 and 2, although diets 1, 4, and 5 and diets 1, 2, and 5 were not different (P> 0.05). No differences among dietary treatments were found for fat color values on a subjective basis. Pigs fed diet 5 had a more desirable objective fat color than pigs fed all white corn, and diets 1, 3, and 4 were not different (P> 0.05). Pigs fed diet 5 had greater levels of SFA and MUFA, and lower levels of unsaturated fatty acids and PUFA, in the subcutaneous fat than pigs fed all other diets. These results indicate that the energy sources evaluated in this study had little effect on eating quality of pork that was held for 25 to 27 d postslaughter.

Three selection models were evaluated to compare selection candidate rankings based on EBV and to evaluate subsequent effects of model-derived EBV on the selection differential and expected genetic response in the population. Data were collected from carcass- and ultrasound-derived estimates of loin i.m. fat percent (IMF) in a population of Duroc swine under selection to increase IMF. The models compared were Model 1, a two-trait animal model used in the selection experiment that included ultrasound IMF from all pigs scanned and carcass IMF from pigs slaughtered to estimate breeding values for both carcass (C1) and ultrasound IMF (U1); Model 2, a single-trait animal model that included ultrasound IMF values on all pigs scanned to estimate breeding values for ultrasound IMF (U2); and Model 3, a multiple-trait animal model including carcass IMF from slaughtered pigs and the first three principal components from a total of 10 image parameters averaged across four longitudinal ultrasound images to estimate breeding values for carcass IMF (C3). Rank correlations between breeding value estimates for U1 and C1, U1 and U2, and C1 and C3 were 0.95, 0.97, and 0.92, respectively. Other rank correlations were 0.86 or less. In the selection experiment, approximately the top 10% of boars and 50% of gilts were selected. Selection differentials for pigs in Generation 3 were greatest when ranking pigs based on C1, followed by U1, U2, and C3. In addition, selection differential and estimated response were evaluated when simulating selection of the top 1, 5, and 10% of sires and 50% of dams. Results of this analysis indicated the greatest selection differential was for selection based on C1. The greatest loss in selection differential was found for selection based on C3 when selecting the top 10 and 1% of boars and 50% of gilts. The loss in estimated response when selecting varying percentages of boars and the top 50% of gilts was greatest when selection was based on C3 (16.0 to 25.8%) and least for selection based on U1 (1.3 to 10.9%). Estimated genetic change from selection based on carcass IMF was greater than selection based on ultrasound IMF. Results show that selection based on a combination of ultrasonically predicted IMF and sib carcass IMF produced the greatest selection differentials and should lead to the greatest genetic change.

Progeny (n = 589) of randomly mated Duroc pigs were used to determine the genetic and phenotypic relationships between individual s.c. backfat layers and i.m. fat percent (IMF) of the longissimus. Five days before slaughter, cross-sectional ultrasound images were collected at the 10th rib by a National Swine Improvement Federation-certified ultrasound technician using an ultrasound machine (Aloka 500 SSD) fitted with a 12-cm linear array transducer. Off-midline backfat (SBF) and loin muscle area (SLMA) were measured. Individual s.c. backfat layers were measured at the same location: outer (OBF), middle (MBF), and inner (IBF). Off-midline backfat (CBF) and loin muscle area (CLMA) were measured on the carcass 24 h postmortem. A slice from the 10th rib of the loin muscle was obtained for determination of IMF. Heritability estimates and genetic correlations were calculated fitting all possible two-trait animal models in MATVEC (Wang et al., 2003). The heritabilities for OBF, MBF, IBF, CBF, SBF, and IMF were 0.63, 0.45, 0.53, 0.48, 0.44, and 0.69, respectively. The genetic correlations of OBF, MBF, and IBF with IMF were 0.36, 0.16, and 0.28, respectively, and the genetic correlations of CBF and SBF with IMF were 0.25 and 0.27, respectively. Genetic correlations between OBF and MBF, OBF and IBF, and MBF and IBF were 0.43, 0.45, and 0.67, respectively. Results demonstrate that individual backfat layers are highly heritable, of similar magnitude to total backfat, and have similar genetic correlations with IMF. Individual backfat layers could become candidate traits for implementation into a multiple-trait genetic evaluation to improve IMF, while minimizing the detrimental effect on total backfat depth.

An evaluation of porcine longissimus myoglobin concentration was conducted to determine breed and gender differences for myoglobin content, estimate genetic parameters for myoglobin concentration, and determine the relationship between myoglobin content and objective measures of muscle color. Data from centrally tested (n = 255), purebred Yorkshire (42), Duroc (61), Hampshire (17), Chester White (28), Berkshire (67), Poland China (28), and Landrace (12) barrows and gilts from the 1999 National Barrow Show Sire Progeny Test were used. Ultimate pH and Hunter L were measured on the 10th-rib face 24 h postmortem. A section of bone-in loin containing the 10th rib was taken to the Iowa State University Meats Laboratory. At 48 h postmortem, Hunter L, CIE L*, a*, and b*, Japanese color score, and water-holding capacity were measured on the face of the 10th-rib loin chop. A slice from the 10th-rib loin section was evaluated for percentage of i.m. fat. The resulting loin chop was used for the determination of soluble myoglobin concentration (mg/g, wet basis). Chester White, Hampshire, and Duroc pigs had the highest (P< 0.05) myoglobin concentration (0.92, 0.95, and 0.85 mg/g, respectively), whereas Landrace had the lowest (0.62 mg/g; P< 0.05). No gender differences were detected for myoglobin concentration. The heritability estimate for soluble myoglobin concentration was 0.27. Residual correlations between soluble myoglobin and CIE L*, a*, b*, Hunter L (24 h), Hunter L (48 h), and Japanese color score were −0.17, 0.23, −0.15, −0.16, −0.13, and 0.13, respectively. These correlations are low but in the desired direction. The residual correlation between soluble myoglobin and intramuscular fat percent was 0.18. Results show that myoglobin concentration has a moderate heritability and could be used in a selection program to make pork loins darker in color.

Litter (n = 8,424) and female performance records were collected in two breed-to-wean production units in order to evaluate genetic line differences for sow longevity and maternal performance over four parities. Lines evaluated were American Diamond Genetics, Danbred North America, Dekalb-Monsanto DK44, Dekalb-Monsanto GPK347, Newsham Hybrids, and National Swine Registry. Females within a line were derived from a minimum of 65 sires, 197 dams (three dams per sire), and a maximum of three daughters per dam, except in the GPK347, which were produced using semen from 12 Nebraska Index boars mated with Dekalb-Monsanto Line 34 females. All lines expressed 100% maternal heterosis. Mixed model statistical procedures were used with fixed effects including genetic line, parity, production unit, and two-way interactions. Random effects included a contemporary week of production and female for repeated records. Lactation length (average 15 d) was included as a linear covariate where appropriate. In total, 3,599 females entered as early-weaned pigs, 3,283 entered the breeding herd, 2,592 farrowed at least a single litter, and 1,656 and completed four parities. Line (P< 0.001) and parity (P< 0.001) effects were observed for virtually all traits measured. Ranges of genetic line differences averaged across parities were 1.76 pigs for total born, 1.45 pigs born alive, and 0.31 stillborn pigs per litter. Ranges of line differences in total and live litter weight were 1.4 and 1.3 kg, respectively. Ranges among lines, within Parities 1 through 4, for litter size at weaning were 0.56, 1.08, 0.91, and 0.64 pigs per litter, respectively. Line differences for weight (33.8 kg) and backfat depth (6.4 mm) at farrowing, lactation feed intake (8.7 kg), weight loss (5.0 kg), and backfat loss (0.87 mm) were observed. Extended wean-to-estrus interval was related to variation in weight, feed intake, and backfat loss in all lines except the GPK347. The GPK347 females farrowed and weaned the largest number of pigs, ate less feed in lactation, and lost more backfat and weight during lactation, yet they had the largest litters and the shortest wean-to-estrus intervals. Line × parity interactions existed for many traits due to small rank changes, but in general, the high- and low-ranked lines did not change. Genetic line differences in reproductive efficiency through four parities exist and must be recognized when choosing a female line.

Data from 456 homozygous halothane normal purebred Yorkshire, Duroc, and Other-breed pigs from two national progeny testing and genetic evaluation programs were utilized to estimate genetic parameters for carcass components in pigs. Carcass components were cut and weighed according to Institutional Meat Purchase Specifications. Primal cut weights evaluated included 401 Ham (HAM), 410 Loin (LOIN), 405 Picnic shoulder (PIC), 406 Boston Butt (BB), and 409 Belly (BELLY). Individual muscle weights included the inside (INS), outside (OUT), and knuckle (KNU) muscles of the ham, the longissimus dorsi (LD) and psoas major (TEND) of the loin, and the boneless components of both the Boston Butt (BBUTT) and picnic (BPIC). Muscle weights from each primal were summed to yield a boneless subprimal weight (BHAM, BLOIN, BSHLDR), and all boneless subprimals were summed to yield total primal boneless lean (LEAN). Heritability estimates for HAM, LOIN, and BELLY were 0.57, 0.51, and 0.51, respectively. Heritability estimates for BB and PIC were 0.09 and 0.21, respectively. Heritability estimates for the boneless components of each primal were higher than those for the intact primals. Genetic correlations for HAM, LOIN, and PIC with loin muscle area (LMA) were 0.53, 0.78, and 0.70, respectively, and −0.62, −0.51, and −0.60, respectively, with 10th rib off-midline backfat (BF10). Boneless subprimal components were highly correlated with LEAN. Gilts had heavier weights (P< 0.01) than barrows for all boneless subprimals, individual muscles, LEAN, and for all primal cuts except BELLY. Gilts also had less BF10 and more LMA (P< 0.01) than barrows. Duroc pigs had a heavier (P< 0.01) weight for HAM and PIC when compared to Yorkshires. Yorkshire pigs had more (P< 0.01) LOIN weight than did the Durocs. Results suggest primal, boneless subprimal, and individual muscle weights in pigs should respond favorably to selection.

Purebred Durocs (n = 207) were used to develop a model to predict loin intramuscular fat percentage (PIMF) of the longissimus muscle in live pigs. A minimum of four longitudinal, real-time ultrasound images were collected 7 cm off-midline across the 10th to the 13th ribs on the live animal. A trained technician used texture analysis software to interpret the images and produce 10 image parameters. Backfat and loin muscle area were measured from a cross-sectional image at the 10th rib. After harvest, a slice from the 10th to the 11th rib loin interface was used to determine carcass loin intramuscular fat percentage (CIMF). The model to predict loin intramuscular fat percentage was developed using linear regression analysis with CIMF as the dependent variable. Initial independent variables were off-test weight, live animal ultrasonic 10th rib backfat and loin muscle area, and the 10 image parameters. Independent variables were removed individually until all variables remaining were significant (P< 0.05). The final prediction model included live animal ultrasound backfat and five image parameters. The multiple coefficient of determination and root mean square error for the prediction model were 0.32 and 1.02%, respectively. An independent data set of Duroc (n = 331) and Yorkshire (n = 288) pigs from two replications of the National Pork Board's Genetics of Lean Efficiency Project were used for model validation. Results showed the Duroc pigs provided the best validation of the model. The product moment correlation and rank correlation coefficients between PIMF and CIMF were 0.60 and 0.56, respectively, in the Duroc population. Results show real-time ultrasound image analysis can be used to predict intramuscular fat percentage in live swine.

Records on 361,300 Yorkshire, 154,833 Duroc, 99,311 Hampshire, and 71,097 Landrace pigs collected between 1985 and April of 2000 in herds on the National Swine Registry Swine Testing and Genetic Evaluation System were analyzed. Animal model and REML procedures were used to estimate random effects of animal genetic, common litter, maternal genetic, and the covariances between animal and maternal for lean growth rate (LGR), days to 113.5 kg (DAYS), backfat adjusted to 113.5 kg (BF), and loin eye area adjusted to 113.5 kg (LEA). Fixed effects of contemporary group and sex were also in the statistical model. Based on the single-trait model, estimates of heritabilities were 0.44, 0.44, 0.46, and 0.39 for LGR; 0.35, 0.40, 0.44, and 0.40 for DAYS; 0.48, 0.48, 0.49, and 0.48 for BF; and 0.33, 0.32, 0.35, and 0.31 for LEA in the Yorkshire, Duroc, Hampshire, and Landrace breeds, respectively. Estimates of maternal genetic effects were low and ranged from 0.01 to 0.05 for all traits across breeds. Estimates of common litter effects ranged from 0.07 to 0.16. A bivariate analysis was used to estimate the genetic correlations between lean growth traits. Average genetic correlations over four breeds were −0.83, −0.37, 0.44, −0.07, 0.08, and −0.37 for LGR with DAYS, BF, and LEA, DAYS with BF and LEA, and BF with LEA, respectively. Average genetic trends were 2.35 g/yr, −0.40 d/yr, −0.39 mm/yr, and 0.37 cm2/yr for LGR, DAYS, BF, and LEA, respectively. Results indicate that selection based on LGR can improve leanness and growth rate simultaneously and can be a useful biological selection criterion.

One side of a triangular molecular tile has been successfully synthesized. The synthesized peptide contains two cysteines (Cys), two glutamic acids (Glu), and a p-aminomethylbenzoyl-p-benzoic acid (AMBBA). The cysteines anchor the peptide to a gold surface by formation of gold−thiolate bonds. The negatively charged glutamic acids should assist in the binding of positively charged proteins to the peptide. The rigid AMBBA provides a benzophenone group for photochemically tethering proteins to the peptide and also acts as the corner for the triangle. Electron spectroscopy for chemical analysis (ESCA) and near-edge X-ray absorption fine structure were used to characterize the composition and orientation of the AMBBA-Cys-Glu-Cys-Glu peptide on the gold surface. Adsorption from 7 μM solutions of the peptide in phosphate-buffered saline produced peptide overlayers with the thiol groups from both cysteines bound to the gold surface. The amide groups of the peptide backbone and the aromatic rings of the AMBBA groups were both oriented parallel to the gold surface. ESCA and fluorescence microscopy demonstrated that albumin could be successfully photoimmobilized to the adsorbed peptide tether. The AMBBA-Cys-Glu-Cys-Glu peptide on gold also could photochemically tether chymotrypsin. The tethered chymotrypsin was active and capable of cleaving a fluorogenic substrate. When the chymotrypsin was tethered as a positively charged protein, it exhibited higher enzyme activity than when it was tethered as a negatively charged protein. However, in all cases the activity of the bound chymotrypsin was lower than its activity in solution.

Establishing relationships among specific quality traits is important if significant progress toward developing improved pork quality is to be realized. As part of a study to examine the individual effects of genes on meat quality traits in pigs, a three-generation resource family was developed. Two Berkshire sires and nine Yorkshire dams were used to produce nine F1 litters. Sixty-five matings were made from the F1 litters to produce four sets of F2 offspring, for a total of 525 F2 animals used in the study. These F2 animals were slaughtered at a commercial facility upon reaching approximately 110 kg. Carcass composition traits, pH measurements, and subjective quality scores were made at 24 h postmortem. Loin samples (n = 525) were collected at 48 h postmortem, and meat quality traits were evaluated. These traits included pH (48 h), Hunter L-values, drip loss, glycolytic potential, ratio of type IIa/IIb myosin heavy chains (IIa/IIb), total lipid, instrumental measures of tenderness using the Star Probe attachment of the Instron, cook loss measurements, and sensory evaluations. Significant phenotypic correlations were found between many carcass, instrumental, and biochemical measurements, and sensory quality traits. Star Probe measurements were significantly correlated with drip loss (0.29), glycolytic potential (0.30), pH (-0.29), total lipid (-0.14), and Hunter L-values (0.28). Drip loss was significantly correlated with glycolytic potential (0.36), pH (-0.28), IIa/IIb (-0.10), and Hunter L-values (0.33). Hunter L-values were also significantly correlated with total lipid (0.33) and IIa/ IIb (-0.11). Sensory tenderness, flavor, and off-flavor scores were significantly correlated with drip loss, pH, and glycolytic potential measurements. Marbling score, total lipid, and drip loss were not significantly correlated with sensory juiciness scores, but cooking loss was. Marbling and total lipid were significantly correlated with firmness scores (0.37 and 0.31, respectively). Taken together, the data in this study suggest that changes in some meat quality traits can affect many other meat quality attributes. The correlations yield information that could aid in directing future studies aimed at understanding the underlying biological mechanisms behind the development of many quality traits.

Conjugated linoleic acid (CLA) was supplemented to crossbred growing-finishing barrows (n = 60) at 0.75% of the total diet. Pigs were randomly assigned to the CLA or control diets based on stress genotype (negative, carrier, or positive). Gain:feed was higher for CLA diet animals (350 g/kg feed) than for control diet animals (330 g/kg feed) independent of genotype (P< 0.05). No differences were observed for ADG for the diets (P= 0.71) or genotype classes (P= 0.40). Postmortem pH was lower (P< 0.01) by 3 h for CLA-supplemented pigs, with no differences in ultimate pH. No differences (P= 0.16) were observed for ultimate pH between the three genotypes. Conjugated linoleic acid-supplemented pigs exhibited less 10th rib fat depth (2.34 cm vs 2.84 cm) and last rib fat depth (2.46 cm vs 2.72 cm) than control pigs (P< 0.05). Loin muscle area (LMA) was not affected (P= 0.18) by CLA supplementation, but LMA was different (P< 0.02) for genotype; positive genotype carcasses had the largest LMA (45.02 cm2) and negative carcasses had the smallest LMA (36.44 cm2). Carrier carcasses were intermediate for LMA (40.76 cm2). Subjective scores for color were not affected (P= 0.98) by CLA but color was different (P< 0.01), with scores of 1.50, 2.40, and 3.1 for positive, carrier, and negative genotypes, respectively. Subjective marbling scores were increased (P< 0.03) in all genotypes with CLA supplementation. Subjective firmness scores were higher (P< 0.06) for CLA-supplemented pigs and were highly correlated (0.89) to marbling scores. The L* values were higher (P< 0.01) for stress-positive pigs at 24 h postmortem. Also, L* values were higher (P< 0.01) for CLA-fed pigs over 7 d of shelf storage. Sensory characteristics were not different with CLA supplementation for tenderness (P= 0.24), juiciness (P= 0.35), or flavor intensity (P= 0.14). This study showed that LMA was increased with stress-carrier and stress-positive genotypes, but lean color was negatively affected with the presence of the stress gene. Conjugated linoleic acid supplementation improves feed efficiency, decreases backfat, and improves pork quality attributes of marbling and firmness of the longissimus muscle. Furthermore, there is seemingly no interaction between the stress-genotype status of pigs and the subsequent effect of CLA on their growth and performance.

This study was designed to observe the effects of conjugated linoleic acid (CLA) supplementation on lean content of pork carcass primal cuts (hams, loins, and bellies) and to determine the ability of total body electrical conductivity (TOBEC) to predict lean content. A total of 64 crossbred growing-finishing barrows were placed on a control (soybean oil) or CLA (0.75%) diet at an average weight of 40 kg. Pigs were penned in pairs according to diet and stress genotype (negative, carrier, and positive) and slaughtered at 115 kg. Stress genotype was included because of known variations in lean content. Hams (IMPS 401A; n = 64), loins (IMPS 410; n = 24), and bellies (IMPS 408; n = 63) were fabricated from carcasses at 24 h postmortem and scanned for electromagnetic (EM) absorption by a MQ-25 EM scanner. Each wholesale cut was scanned in triplicate at 2.5 MHz to yield a peak mean average (PMA) value then separated into lean, fat, bone, and skin components. Bellies were skinned prior to scanning then subjected to a belly bar firmness test before dissection. Supplementation with CLA had no effect (P> 0.05) on lean ham composition. Regression analysis was used for lean weight prediction using primal weight and PMA value as predictors. Lean content prediction of hams by TOBEC resulted in an R2of 0.80. Loins from CLA-supplemented pigs exhibited increased lean weight (P< 0.05) and PMA values (P< 0.05) compared to controls. Lean prediction of loins by TOBEC resulted in an R2 of 0.66. Bellies from CLA-supplemented pigs had a higher percentage of moisture (P< 0.03) and protein (P< 0.01) and decreased percentage of lipid (P< 0.01). The R2values from the regression analysis predicting protein, moisture, protein + moisture, and fat-free soft tissue composition of the skinless bellies were 0.67, 0.68, 0.71, and 0.78, respectively.

Hampshire and Landrace sows and crossbreds of the two breeds were used to determine heterosis and recombination effects for milk production, milk composition, and litter traits at birth and d 21. Twelve mating types were represented in this study: two purebred, two F1two F2, two F3, and four backcross. Information was gathered on a total of 358 litters over four farrowing seasons. Milk production was measured at d 10 and 20 of litter age according to the weigh-suckle-weigh procedure. Milk samples were collected at d 10 and 20 of litter age and evaluated for percentages of fat (PCFA), protein (PCPR), lactose (PCLA), and solids-not-fat (PCSN). The model used to evaluate litter traits at birth included main effects of mating type, parity, and farrowing season. The model used for milk production and milk composition traits included these main effects and number of pigs nursed as a covariate. Estimates of maternal genetic effects showed that Landrace females were superior to Hampshire females for number born (NB), number born alive (NBA), litter birth weight (LBW), adjusted 21-d litter weight (ALW), and milk production at d 10 of litter age (WT10). Hampshires were superior to Landrace for PCPR at d 10 of litter age and PCSN at d 10 and 20 of litter age. Heterosis effects were significant (P< .05) for NBA (.97) and LBW (1.46 kg). Maternal heterosis effects were significant for LBW (3.94 kg; P< .01). Epistatic recombination losses in the offspring were significant for LBW (6.80 kg; P< .05). Differences in maternal performance of reciprocal F1dams were generally not significant. Heterosis and recombination effects were not significant for milk production or milk composition.

Twelve different mating types among the Hampshire and Landrace breeds were used to determine direct, maternal, heterosis, and recombination effects for performance and carcass traits. Mating types used were two purebred, two F1, two F2, two F3, and four backcross. Carcass data were collected on 238 barrows and 262 gilts over four replications. Traits measured were length (LENG), 10th rib off midline backfat (BF10), longissimus muscle area (LMA), and dressing percentage (DRS%). Average backfat (AVBF) was calculated as the mean of three midline fat depths measured opposite the first rib, last rib, and last lumbar vertebra. The model used to evaluate the carcass traits included main effects of mating type, farrowing season, and sex and included slaughter weight as a covariate. The performance traits of ADG, feed efficiency (FE), daily feed consumption (DFC), lean gain per day (LNGN), and lean efficiency (LNEF) were measured on a pen basis. Comparisons of reciprocal F1crosses showed that carcasses from pigs sired by Hampshire boars were leaner and had more LMA than those sired by Landrace boars. Heterosis percentages were significant for AVBF (7.2%; P< .01), BF10 (8.8%; P< .01), DRS% (1.5%; P< .01), ADG (11.5%; P< .01), DFC (10.2%; P< .01), LNGN (10.6%; P< .01), and LNEF (6.0%; P< .05). Epistatic recombination losses in the offspring were significant for LENG (3.6 cm; P< .05) and approached significance for BF10 (6.1 mm; P< .10).

Protein layers are deposited on the surface of implanted biomaterials. Better understanding of the interaction between the surface protein layers and the biological system would lead to the development of future biomaterials with superior biocompatibilities. Well-organized biorecognizable surfaces can be formed with various template molecules that provide an appropriate spacing for the attachment of recognition groups to the modified surface. Silane coupling reagents, porphyrin thiols, and cyclic peptides are being used as templates to introduce nano-scale patterns on solid surfaces. Synthesis of these templates and characterization of the modified surface are described. © 1998 John Wiley & Sons, Inc. Biopoly 47: 185–193, 1998