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 11h 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 beat 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.

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 x Duroc, mated to PIC 1055 females. A total of 1,040 pigs were included in the study in a 2 x 2 x 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 degrees 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.

and Implications The purpose of this study was to estimate the heritabilities and genetic correlations for body composition and structural soundness traits using 1449 gilts in a commercial sow unit. Evaluated body composition traits included body weight, loin muscle area, last rib backfat and 10 th rib backfat. Soundness traits consisted of 6 body structure traits, 5 leg structure traits per leg pair and overall leg action. Variance components were estimated using multivariate animal models. The heritability estimates for body composition traits were high, moderate for body size traits, low to moderate for body shape traits and relatively low for leg traits. Across all evaluated traits, only the heritability estimates for turned front legs did not differ significantly from zero. Several high genetic correlations were obtained among the body structure trait group. The majority of genetic correlations between leg structure traits were low and statistically insignificant. The genetic correlations between leg traits and overall leg action were not significant. However, there was a trend for structural defects being related to poorer overall leg action. The genetic correlations between structure traits and body composition traits were primarily low to moderate indicating that even in a case of antagonistic relationship it is possible to achieve genetic improvement in both composition and structural traits. The fact that non-zero heritability estimates were obtained for almost all studied traits warrants further investigations regarding associations of soundness traits with reproductive performance and sow productive lifetime.

and ImplicationsThe purpose of this study was to estimate the genetic parameters for body composition, growth, structural soundness and lifetime reproductive traits in commercial females. The study involved 1,447 females from two commercial genetic lines. Analyzed traits included loin muscle area, backfat, days to 113.5 kg body weight, 6 body structure traits, 5 leg structure traits per leg pair, overall leg action, length of lifetime (L), percentage non-productive from total herd days (NPD%), lifetime number born alive (LBA) and number born alive per lifetime days (LBA/L). The heritability estimates were obtained with multiple trait animal models. The estimates were high for growth and body composition traits and low to moderate for structural soundness traits and lifetime reproductive traits. The genetic correlations were estimated using bivariate animal models. Most of the genetic correlations of growth, body composition and soundness traits with lifetime reproductive traits were low and non-significant (P > 0.05). In general, loin muscle area and body structure traits had a nonsignificant trend of being favorably associated with lifetime reproductive traits, while an unfavorable trend was observed in the associations of backfat and days to 113.5 kg body weight with lifetime reproduction. The strongest associations with lifetime reproductive traits were obtained for days to 113.5 kg body weight, body length, rib shape, turned front legs and upright rear legs. However, these results need to be interpreted within the distributions of observations present in the dataset. Females with closer to intermediate growth rate to 113.5 kg (range 144 -227 days, 84 % of females reaching the weight by 190 days of age), intermediate body length (89% of observations divided into scores 4 -6, 5 describing intermediate length), more shaped ribs (observations close to normally distributed over the 9point scale), slightly outwards turned front legs (after transforming records to deviations from optimum, 79% of observations distributed into two best scores) and less upright rear legs (after separating weak/upright rear legs into two traits, 89% of observations distributed into two best scores) had greater lifetime reproduction.

and Implications Efficient pork production is a necessity for an economically viable swine industry. Number two yellow corn is considered the primary energy source for swine diets in the Midwest. Despite the low protein content, corn is considered one of the most economical feed stuffs available to the swine production system. Barley is a high fiber that has approximately 89% of the energy content of corn. While barley contains a higher protein and amino acid level than corn, animal performance is expected to be depressed due to the high fiber content. Because barley lacks the carotene content that yellow corn possesses, it has been hypothesized that barley-fed pigs will yield higher meat and fat quality that is desired by export markets. White corn was used in this trial to determine its contribution to meat quality and growth traits. An experiment was conducted to evaluate the effect of energy source on performance and carcass traits of pigs. Diet treatments (primary energy source) were: 1) yellow corn, 2) white corn, 3) 1/3 yellow corn, 2/3 white corn, 4) 2/3 yellow corn, 1/3 white corn, 5) barley. Pigs completing the trial were from two sires lines, Duroc (n=500) and Hamp x Duroc (n=499), that were mated to PIC 1055 females. Pigs were randomly allocated to pens based on genetic type and gender using a 2 x 2 x 5 factorial arrangement with two genetic types, two sexes (barrows and gilts) and five treatments Animals fed these diets differing in energy source did not express a difference in average daily gain, average daily feed intake, feed-to-gain ratio, backfat depth or percent fat free lean. However, barley-fed pigs did have a smaller (p < .05) loin muscle area than pigs fed corn-based diets. Diet did not have an effect on sensory panel traits for tenderness or chewiness and limited differences were observed for juiciness, flavor, and off-flavor. Percentage loin purge, and cooking loss did not differ among diets fed to the pigs with minimal difference noted for color values. Pigs fed barley diets did have lower iodine value content within the subcutaneous fat indicating that the fat is of firmer quality. Results of this trial suggest that barley does not have an advantage in meat quality traits when compared to traditional corn-based diets. Barley does however have a significant impact on the hardness of pork fat, but does not have a significant effect on subjective color values.