The objective of this study was to evaluate the effect of including feed intake records of boars on the genetic gain for feed efficiency. Data were obtained from a Duroc nucleus herd within a Chinese company’s breeding system. The data obtained included ADG, feed conversion ratio (FG), ADFI, days to 115 kg, backfat depth, and loin muscle area. The ADG, FG, and ADFI data were obtained from 570 Duroc boars housed in pens with electronic feeders (FIRE, Feed Intake Recording Equipment, Osborne Industries, Osborne, KS). There were 4,984 Duroc boar and 4,809 gilt progeny. Two sets of estimated breeding values for ADG, FG, ADFI, days to 115 kg, backfat depth, and loin muscle area were estimated using a multivariate animal model, with and without data collected from the FIRE feeders. Terminal sire indices were calculated based on the production costs and market prices for the United States and China. A 2-stage selection procedure was applied with the heaviest sound boars (mean age = 130 ± 17 d) being tested in the FIRE feeder and then the top 100 being selected for breeding. The terminal sire index value gain estimated with ADFI data included was 9.3% greater than the estimates that did not include the ADFI data. The estimated genetic gain for FG with ADFI data was 17% greater than the same annual estimated genetic gain without ADFI data. Overall, there is a substantial genetic gain of FG when individual ADFI records of boars were included in the selection index.

The objective was to compare selection indexes based on the production costs and economic values from the United States and China. Indexes including terminal sire (TSI), maternal line (MLI), and sow productivity (SPI) were calculated based on the production costs and market prices for the United States and China. Estimated breeding values for days to 113.5 kg, backfat depth, loin muscle area, number born alive, number weaned, litter weight adjusted to 21 d, days from weaning to estrus, and litter birth weight were provided by a Chinese pig breeding company to evaluate alternative TSI and MLI indexes. The Duroc data included 559 dams, 39 sires, 5,079 boars, and 4,809 gilts. The Landrace data included 199 dams, 83 sires, 2,749 boars, and 2,750 gilts. The Yorkshire data included 1,368 dams, 139 sires, 18,481 boars, and 17,962 gilts. The means, SD, and correlations for the estimated breeding values and indexes were calculated. The Chinese TSI values were more highly correlated (r = 0.97 to 0.99) with the US indexes than the MLI values (r = 0.92 to 0.97). Overall, the Chinese indexes had greater SD (TSI, 58 to 87% greater; SPI, 22 to 26% greater; MLI, 43 to 76% greater). The TSI were all highly correlated (r >0.98) with feed conversion. The Chinese MLI values had greater correlations with TSI and lesser correlations with SPI than the US indexes. The Chinese MLI placed greater emphasis on the postweaning traits but less emphasis on sow productivity traits than did the current US MLI.

Lines of purebred pigs are essential for use in crossbreeding systems within the commercial industry. However, verification of breed purity can be challenging, and using color test matings to confirm white color in the Yorkshire or Landrace breeds is time-consuming and costly. Alternatively, advances in the availability and analysis of genomic data may enable rapid and precise determination of breed composition. Here, we have refined methods for determination of breed composition in U.S. populations of four swine breeds, and white color in Yorkshire or Landrace breeds using SNPs present on the GeneSeek Genomic Profiler for Porcine LD platform. These methods use a linear model in which unknown animal genotypes are regressed on a panel of allele frequencies, derived from reference Duroc, Landrace, Hampshire and Yorkshire purebred animals. Only SNPs that are not fixed across all reference animals and have a genotyping call rate of 90% or greater were used in the model. Model coefficients were constrained to be non-negative and to sum to 1.0, facilitating their interpretation as breed composition coefficients. By simulating 1000 admixed animals of known composition, a strong correlation was observed between the actual and estimated breed proportion of the simulated animals (R2 = 0.94) so long as the actual breed of the simulated animals was reflected in the reference panel. Among a real dataset consisting of 920 Yorkshire sires, 95% of the animals were evaluated to have a Yorkshire breed proportion of 0.825 or greater. Determining that an animal may be highly purebred genome-wide does not preclude from failing a color test mating, in which alleles at particular genes such as KIT play a major role in color segregation patterns. Using seven SNPs flanking KIT (spanning chr8:43Mb– 44Mb), we have demonstrated that SNP haplotypes derived from the reference animals may be used to compute breed composition probabilities for a genomic segment flanking KIT of an unknown test animal. From the real Yorkshire sire dataset, 95% of the animals were estimated to have at least a 0.439 KIT-based breed composition probability of being a white breed. Dual use of genome-wide breed proportions and gene-based breed probabilities has great potential to inform swine breeders of the overall purity of an animal, as well as breed characteristics around particular key genes. Such knowledge may reduce the need to perform color test matings or other time-consuming and expensive procedures for breed verification.

The objective was to associate gilt development traits with genetic line, diet and fertility group (FG). Gilts (n=1225) were reared from 162 to 265 days of age at a gilt development unit (GDU) and sent to sow farms. Females were Landrace (L), Large White (LW), L and LW F1 or L and LW composite. Estrous traits included age at puberty (AGEPUB), length of estrus (LOE), maximum strength of standing reflex with (MSRBOAR) or without (MSRNOBOAR) a boar present, total strength of standing reflex with (TSRBOAR) or without (TSRNOBOAR) a boar present, vulva redness (VR), strength of vulva reddening and swelling (VISUAL VULVA) and vulva width (VW). Growth and body composition traits were puberty weight, days to 114kg and 10th rib backfat (BF) and loin muscle area (LMA) at 114kg and puberty. Structural conformation traits included muscle mass, rib width, front leg side view, rear leg side view, front legs front view, rear legs rear view and locomotion (LOC). Sow farm entry traits were age, weight, BF and LMA. Sow traits included whether or not a gilt farrowed (STAY), age at first farrowing and total number born (TNB). Fertility groups were; FG0=did not reach puberty at the GDU (NOPUB), did not farrow (DNF); FG1=reached puberty at the GDU (YESPUB), DNF; FG2=NOPUB, farrowed; FG3=YESPUB, farrowed. Genetic lines differed (P<0.05) for estrous traits LOE, TSRBOAR, MSRNOBOAR, TSRNOBOAR, VR, VISUAL VULVA and VW. Females fed restrictively vs. ad libitum had a longer (P<0.05) LOE (2.18 vs. 2.03d), higher (P<0.05) TSRBOAR (15.4 vs. 14.0) and younger (P<0.05) AGEPUB (219 vs. 225d). Fertility groups 0, 1, 2 and 3 contained 45 (4%), 255 (24%), 66 (6%) and 698 (66%) gilts, respectively. Gilts from FG3 in comparison to FG1 had a longer (P<0.05) LOE (2.16 vs. 2.06d), greater (P<0.05) MSRBOAR (7.6 vs. 7.4) and greater (P<0.05) TSRBOAR (15.4 vs. 14.6). Fertility group 0 had less (P<0.05) BF, poorer (P<0.05) LOC and was narrower (P<0.05) ribbed compared with the other FG's. Based on these results it was concluded that gilts with LOE ≤1 day or weak standing reflexes were less likely to farrow a litter.

Gilts (n=45) were used in this study to characterize the effect of genotype on loin characteristics and quality over the length of the loin. Three diverse genotypes included a high quality Duroc line (A), a Duroc based composite line selected for lean growth (B), and an F1 cross of the two (C). After harvest, bone-in loins were removed from the carcass and cut perpendicular to the backbone at the 5th/6th rib, 7th/8th rib, 10th/11th rib, last rib, midlumbar, and the loin/sirloin juncture. Quality measurements were obtained at the 5th/6th rib, 10th/11th rib, and the loin/sirloin juncture. Digital images were taken of each surface (n=6) and analyzed for the determination of loin muscle area (LMA), muscle width, muscle depth (at three locations across the loin face), and fat depth. The average loin depth was calculated and used to calculate the loin depth:width ratio as an indication of loin shape or conformation. Loins from line A had the lowest (P<0.05) subjective color score, had the highest (P<0.05) amount of marbling, and were the firmest (P<0.05) of all three lines. There were also differences (P<0.05) between genetic lines for LMA, width, all three depths, fat depth, and depth:depth ratios. The most posterior portions of the loin had the largest (P<0.05) LMA, loin width, fat depth, and muscle depth 1. However, the more anterior portions of the loin had greater (P<0.01) values for the depth:width ratio and muscle depth:depth ratios.

The objective was to estimate correlations of gilt estrus, puberty, growth, composition, and structural conformation traits with first-litter reproductive measures. Four groups of gilts (n = 1,225; Genetic Improvement Services of NC, Newton Grove, NC) entered the NC Swine Evaluation Station (Clayton, NC) averaging 162 d of age and were observed daily for symptoms of estrus. Once symptoms of first estrus were observed in 70% of gilts, recording of symptoms of estrus in all gilts occurred every 12 h for 30 d, utilizing fence-line boar contact. Subjective estrous traits were maximum and total strength of standing reflex, as observed with and without the presence of a boar, and strength of vulva reddening and swelling. Objective estrous traits consisted of vulva redness, vulva width, length of estrus, and age at puberty. Growth and composition traits included BW at puberty, days to 114 kg, and 10th rib backfat and LM area at 114 kg and at puberty. Subjective structural conformation traits were muscle mass, rib width, front leg side view, rear leg side view, front legs front view, rear legs rear view, and locomotion. First-litter sow traits included if gilt farrowed (Stay), age at first farrowing (AFF), total number of piglets born (TNB), and weaning to conception interval (WCI). Variance components were estimated using an animal model with AIREMLF90 for linear traits and THRGIBBS1F90 for categorical traits. Heritability estimates for Stay, AFF, and TNB were 0.14, 0.22, and 0.02, respectively. Genetic correlations between length of estrus, the standing reflex traits, and age at puberty with Stay were 0.34, 0.34 to 0.74, and -0.27, respectively, and with AFF were -0.11, -0.04 to -0.41, and 0.76, respectively. Days to 114 kg had genetic associations with Stay, AFF, and TNB of 0.52, -0.25, and -0.08, respectively. Backfat at 114 kg had genetic correlations with Stay, AFF, and TNB of -0.29, 0.14, and 0.47, respectively. Vulva redness and TNB were negatively correlated phenotypically (r = -0.14) and genetically (r = -0.53). Associations between structural conformation traits with Stay, AFF, TNB, and WCI were generally low to moderate and favorable. Selection for longer length of estrus, stronger standing reflex, or younger age at puberty would increase the proportion of gilts that farrow and reduce age at first farrowing.

Variance components and genetic correlations were estimated among estrus, puberty, growth, and composition traits in Landrace-Large White gilts (n = 1,225; Genetic Improvement Services, Newton Grove, NC) from 59 sires and 330 dams. Four groups of gilts entered the North Carolina Swine Evaluation Station in Clayton at an average age of 162 d and were checked daily for estrus. Once 70% of gilts had reached puberty, recording of estrus symptoms occurred every 12 h for 30 d, using fence-line boar contact. Subjective estrus traits were maximum strength of standing reflex with or without a boar present, total strength of standing reflex with or without a boar present, and strength of vulva reddening and swelling. Objective estrus traits consisted of vulva redness, vulva width, length of estrus in consecutive days based on 12-h observations, and age at puberty (AGEPUB). Growth and composition traits included puberty weight, days to 114 kg (DYS), 10th-rib backfat, and 10th-rib LM area at 114 kg (BF, LMA) and puberty. Variance components were estimated using AIREMLF90 with an animal model. All models included gilt development diet class and breed composition as fixed effects, entry age as a covariate (except DYS, BF, and LMA), a random common litter effect, and a random animal genetic effect. Heritability estimates for length of estrus, maximum strength of the standing reflex with a boar, total strength of the standing reflex with a boar, maximum strength of the standing reflex without a boar, total strength of the standing reflex without a boar, vulva redness, strength of vulva reddening and swelling, and vulva width were 0.21, 0.13, 0.26, 0.42, 0.42, 0.26, 0.45, and 0.58, respectively. Heritability estimates for AGEPUB, puberty weight, 10th-rib backfat at puberty, 10th-rib LM area at puberty, DYS, BF, and LMA were 0.29, 0.39, 0.41, 0.38, 0.24, 0.47, and 0.39, respectfully. Common litter effect estimates ranged from 0.01 to 0.09. The estimated genetic correlation between length of estrus and maximum strength of standing reflex with a boar was 0.99. Genetic correlations between AGEPUB and length of estrus, maximum strength of standing reflex with a boar, and vulva redness were -0.23, -0.32, and 0.20, respectively. Length of estrus had positive genetic associations with DYS and BF (0.30 and 0.29, respectively). It was concluded that past selection for lean BW gain may have weakened the strength of the standing reflex and that sufficient genetic variation exists to make selection for improved swine estrus traits effective.

Sisalto: CD-rom, Proceedings of the 8th World Congress on Genetics Applied to Livestock Production.

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 (r(g) = 0.86 from a 12-trait analysis; r(g) = 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 cm(2) per 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.

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.

Recommended Citation Burkett, J. L.; Newcom, D. W.; Baas, Thomas J.; Schwab, Clint R.; and Stalder, Kenneth J. (2004) "Effect of Technician, Machine, and Animal Body Composition on Accuracy of Ultrasonic Measures of Backfat and Loin Muscle Area in Swine," Animal Industry Report: AS 650, ASL R1941. DOI: https://doi.org/10.31274/ans_air-180814-933 Available at: https://lib.dr.iastate.edu/ans_air/vol650/iss1/100