Selection for Intramuscular Fat in Duroc Swine – An Update

Long-term progress or improvement in many economically important traits is ultimately the responsibility of the seedstock supplier. If selection progress is to be made in traits of economic importance, the trait must: 1) be accurately measurable, 2) show sufficient heritability, and 3) display an adequate level of variation. For such reasons, tremendous progress has been made in the swine industry toward increasing lean meat percentage over the past quarter century. However, in more recent years, meat quality traits have received more attention and have become more important in breeding programs as producers and processors try to meet consumer demands for high quality, nutritious products

Selection for Intramuscular Fat in Duroc Swine

Today’s U.S. pork industry is experiencing phenomenal growth as it continues to meet consumer demand and pork is the most widely eaten meat worldwide. Pork has proven to be a valuable protein source as Americans consume 66 lbs/person/year on a carcass disappearance basis (USDA, 2002 Agricultural Statistics). Pork production in the United States is also a vital part of the economy. Nearly 19 billion pounds of pork, with a retail value of $38 billion, was processed from about 97 million hogs in 2001. The U.S. pork industry is responsible for over$72 billion in total domestic economic activity. In addition, the pork industry adds over $27 billion of value to basic production inputs such as corn and soybeans (NPPC, 2003)

Hair cortisol concentrations in relation to ill-being and well-being in healthy young and old females

Hair cortisol concentration (HCC) provides a retrospective measure of long-term (i.e. over a period of months) cortisol secretion and has been shown to be elevated in relation to chronic stress conditions. However associations in healthy participants with subjective ill-being are less clear and associations with well-being have not been explored. The current study examined HCC in relation to independent comprehensive measures of illbeing (stress, depression, anxiety) and well-being (subjective happiness, life satisfaction, psychological wellbeing) in healthy young and old females (mean ± SD: 19.5 ± 2.2 years and 78.6 ± 6.7 years respectively, total N = 115). The data supported evidence of increased total cortisol secretion with increased age. No association between ill-being and HCC was found in either the young or older group of participants. A positive association between HCC and well-being was found in the older participant group which was independent of ill-being and potential confounds. These findings do not support associations between HCC and ill-being in healthy young or old females. However the results suggest that HCC is able to distinguish levels of well-being in healthy older females

Free-electron Model for Mesoscopic Force Fluctuations in Nanowires

When two metal electrodes are separated, a nanometer sized wire (nanowire) is formed just before the contact breaks. The electrical conduction measured during this retraction process shows signs of quantized conductance in units of G_0=2e^2/h. Recent experiments show that the force acting on the wire during separation fluctuates, which has been interpreted as being due to atomic rearrangements. In this report we use a simple free electron model, for two simple geometries, and show that the electronic contribution to the force fluctuations is comparable to the experimentally found values, about 2 nN.Comment: 4 pages, 3 figures, reference correcte

Quantum Conductance in Semimetallic Bismuth Nanocontacts

Electronic transport properties of bismuth nanocontacts are analyzed by means of a low temperature scanning tunneling microscope. The subquantum steps observed in the conductance versus elongation curves give evidence of atomic rearrangements in the contact. The underlying quantum nature of the conductance reveals itself through peaks in the conductance histograms. The shape of the conductance curves at 77 K is well described by a simple gliding mechanism for the contact evolution during elongation. The strikingly different behaviour at 4 K suggests a charge carrier transition from light to heavy ones as the contact cross section becomes sufficiently small.Comment: 5 pages including 4 figures. Accepted for publication in Phys. Rev. Let

Effects of breed, sex, and halothane genotype on fatty acid composition of pork longissimus muscle

The objective of this study was to estimate the effects of breed, sex, and halothane genotype on fatty acid composition and several fatty acid indices of lipid extracted from porcine LM. Purebred Yorkshire (n = 436), Duroc (n = 353), Hampshire (n = 218), Spotted (n = 187), Chester White (n = 173), Poland China (n = 124), Berkshire (n = 256), and Landrace (n = 187) pigs (n = 1,934; 1,128 barrows and 806 gilts) from 1991, 1992, 1994, and 2001 National Barrow Show Sire Progeny Tests were used. Pigs were classified as the HAL-1843 normal (NN) genotype (n = 1,718) or the HAL-1843 carrier (Nn) genotype (n = 216). For statistical analysis, a mixed model was used that included fixed effects of breed, sex, halothane genotype, test, slaughter date, interaction of breed × sex, and random effects of sire and dam within breed. Breed significantly affected the concentration of individual fatty acids, total lipid content, and the values of several fatty acid indices of LM. Duroc pigs had the greatest (P\u3c 0.01) content of total SFA. Total MUFA concentration in Poland China pigs was greater (P \u3c 0.05) than in all other breeds except the Spotted (P\u3e 0.05). The concentrations of total PUFA were greater (P \u3c 0.01) in Hampshire, Landrace, and Yorkshire pigs compared with those of other breeds. Significant sex differences for individual fatty acids were detected. Compared with gilts, barrows had greater (P \u3c 0.01) concentrations of SFA and MUFA but lower (P \u3c 0.01) total PUFA. Halothane genotype was a significant source of variation for the percentages of some fatty acids. Pigs with the carrier (Nn) genotype had lower concentrations of SFA (P \u3c 0.05) and MUFA (P \u3c 0.01) but a greater concentration of PUFA (P \u3c 0.01) compared with NN pigs. There were significant negative correlations between total lipid content and individual PUFA and significant positive correlations between lipid concentration and most individual SFA and MUFA. In conclusion, the results suggest that breed and sex are important sources of variation for fatty acid composition of LM

Influence of lipid content on pork sensory quality within pH classification

The objective of this project was to determine the contribution of lipid content to textural and sensory properties of fresh pork within defined pH classifications. Pigs (n = 1,535; from 248 sires and 836 dams) from the 1991, 1992, and 1994 National Barrow Show Sire Progeny Test were used in this study. The test included purebred Berkshire (107), Chester White (113), Duroc (249), Hampshire (220), Landrace (165), Poland China (101), Spotted (181), and Yorkshire (399) barrows (901) and gilts (634). Diets were uniform across breeds within test. The halothane (Hal 1843) genotype (1346 NN and 189 Nn) was determined. Pigs were slaughtered at 105 kg of BW, and samples of the LM were obtained from each carcass at the 10th rib. Star probe, sensory traits, and lipid content were determined on the LM from each pig. A pH classification of LM was assigned as follows: class A, \u3e5.95, n = 186; class B, ≥5.80 to 5.95, n = 236; class C, ≥5.65 to 5.80, n = 467; class D, ≥5.50 to 5.65, n = 441; class E, \u3c5.50, n = 205. Data were analyzed using a mixed linear model including pH classification, test, sex, halothane genotype, breed, and breed × sex interaction as fixed effects, with sire and dam within breed included as random effects. Correlations were determined within pH class. Lipid content was a significant source of variation for models predicting star probe values in class C and D and for chewiness in class B, C, and D. Increasing lipid content tended to increase sensory tenderness in pH class D. Sensory tenderness was not affected by lipid content in pH class A, B, or E. Lipid content was not a significant source of variation for juiciness scores within any pH class. Intramuscular lipid is correlated with sensory texture traits primarily in classes C and D. Within class C and D, correlations indicate that increasing lipid content is associated with high sensory tenderness, low sensory chewiness, and low star probe values. It is concluded that lipid content is a small source of variation in texture and tenderness of pork loin with pH between 5.80 and 5.50, but not at a greater or lesser pH

The Evolution of the Intracluster Medium Metallicity in Sunyaev-Zel'dovich-Selected Galaxy Clusters at 0 < z < 1.5

We present the results of an X-ray spectral analysis of 153 galaxy clusters observed with the Chandra, XMM-Newton, and Suzaku space telescopes. These clusters, which span 0 < z < 1.5, were drawn from a larger, mass-selected sample of galaxy clusters discovered in the 2500 square degree South Pole Telescope Sunyaev Zel'dovich (SPT-SZ) survey. With a total combined exposure time of 9.1 Ms, these data yield the strongest constraints to date on the evolution of the metal content of the intracluster medium (ICM). We find no evidence for strong evolution in the global (r<R500) ICM metallicity (dZ/dz = -0.06 +/- 0.04 Zsun), with a mean value at z=0.6 of = 0.23 +/- 0.01 Zsun and a scatter of 0.08 +/- 0.01 Zsun. These results imply that >60% of the metals in the ICM were already in place at z=1 (at 95% confidence), consistent with the picture of an early (z>1) enrichment. We find, in agreement with previous works, a significantly higher mean value for the metallicity in the centers of cool core clusters versus non-cool core clusters. We find weak evidence for evolution in the central metallicity of cool core clusters (dZ/dz = -0.21 +/- 0.11 Zsun), which is sufficient to account for this enhanced central metallicity over the past ~10 Gyr. We find no evidence for metallicity evolution outside of the core (dZ/dz = -0.03 +/- 0.06 Zsun), and no significant difference in the core-excised metallicity between cool core and non-cool core clusters. This suggests that strong radio-mode AGN feedback does not significantly alter the distribution of metals at r>0.15R500. Given the limitations of current-generation X-ray telescopes in constraining the ICM metallicity at z>1, significant improvements on this work will likely require next-generation X-ray missions.Comment: 11 pages, 8 figures, 2 tables. Submitted to ApJ. Comments welcome