Effects of Dietary Energy Source and Corn Oil Inclusion on Plasma Metabolite and Lipid Profiles and Intramuscular Adipose and Muscle Accretion in Beef Cattle

The objectives of this research were to evaluate 1) fluctuations in plasma metabolites and lipid profiles and 2) differences in satellite cell differentiation and proliferation in cattle with differences in marbling relative to total fatness. Dietary starch is thought to optimize accumulation of marbling. In this experiment, readily fermentable fiber or corn oil were substituted for starch from corn in an effort to alter adipose tissue accretion. Crossbred yearling steers (n = 144) were used in a 131 d finishing trial. The trial was designed as a 3 x 2 factorial arrangement of dietary energy source by corn oil inclusion. Dietary energy sources were the high starch diet which contained 8.5% roughage and 81.2% corn or a higher fiber diet in which chopped, high moisture ear corn (43.7%) and dried corn gluten feed (18.2%) were substituted for corn. Corn germ was included in the diet to provide 0, 2, or 6% corn oil in both the starch and fiber diets. Growth performance and carcass characteristics were recorded and blood samples were collected from each animal on d 96 and 131 of the feeding trial. Previously reported carcass data indicated that dietary energy source (starch vs. fiber) did not influence carcass characteristics. However, as the percentage of corn oil increased with additional amounts of corn germ, marbling scores decreased (P \u3c 0.05) at a constant subcutaneous fat thickness. Compositional analyses support a tendency (P ≤ 0.10) for decreased marbling relative to total carcass fat. Feeding germ increases (P \u3c 0.05) in all components of serum cholesterol. Earlier in the feeding period, GERM also caused higher (P \u3c 0.05) circulating glucose and NEFA concentrations. A sub‐population of steers that were highest (n = 12) and lowest (n = 12) for the relationship of marbling to total carcass fatness (M2Ratio) were scrutinized more closely. Differences in M2Ratio were not associated with HCW or fatness, but were associated with marbling (P \u3c 0.001). Serum collected early in the feeding period from high M2Ratio steers resulted in higher (P \u3c 0.05) satellite cell proliferation and differentiation rates in vitro than serum from low M2Ratio steers. This response diminished with additional days on feed. These results indicate that dietary carbohydrate source has minimal influence on carcass fat distributions, but that dietary oil dramatically alters circulating metabolites and is antagonistic to the production goal of high marbling‐high cutability carcasses

The Influence of Maternal Energy Status During Mid‐gestationon Beef Offspring Carcass Characteristics and Meat Quality

Research has suggested that maternal under‐nutrition may cause the development of a thrifty phenotype in the offspring, potentially resulting in greater adiposity and reduced muscle mass. These alterations in fat and muscle development could have lasting impacts on offspring growth, carcass characteristics, and meat quality. Thus, the objective of this study was to determine the influence of maternal energy status during mid‐gestation on offspring carcass characteristics and meat quality. To alter maternal energy status, cows either grazed pasture or were fed in a dry‐lot at 80% of the energy requirements for body weight maintenance during a mean period of 109 to 207 d of gestation. Changes in body condition score (BCS), body weight, ribeye area (REA), and 12th rib backfat were measured throughout mid‐gestation and were used to determine cow energy status [Positive (PES) or Negative (NES)]. Cows in the NES group had a significantly greater reduction in BCS, body weight, REA, and 12th rib backfat during mid‐gestation. Maternal energy status had no influence on offspring hot carcass weight, dressing percent, REA, percent kidney, pelvic, and heart fat, marbling score, percent intramuscular fat, objective color, or Warner‐Bratzler shear force. A tendency was seen for NES calves to have improvements in 12th rib backfat and USDA Yield Grade. A greater MRatio and IRatio (calculations used to compare the ratio of marbling (MRatio) and percent intramuscular fat (IRatio) with 12th rib backfat) were discovered in calves from cows experiencing a negative energy status during midgestation. These results suggest that maternal energy status during mid‐gestation may impact fat deposition in intramuscular and subcutaneous fat depots without impacting muscle mass

Structurama: Bayesian Inference of Population Structure

Structurama is a program for inferring population structure. Specifically, the program calculates the posterior probability of assigning individuals to different populations. The program takes as input a file containing the allelic information at some number of loci sampled from a collection of individuals. After reading a data file into computer memory, Structurama uses a Gibbs algorithm to sample assignments of individuals to populations. The program implements four different models: The number of populations can be considered fixed or a random variable with a Dirichlet process prior; moreover, the genotypes of the individuals in the analysis can be considered to come from a single population (no admixture) or as coming from several different populations (admixture). The output is a file of partitions of individuals to populations that were sampled by the Markov chain Monte Carlo algorithm. The partitions are sampled in proportion to their posterior probabilities. The program implements a number of ways to summarize the sampled partitions, including calculation of the ‘mean’ partition—a partition of the individuals to populations that minimizes the squared distance to the sampled partitions

Relationship of Circulating Ghrelin and Leptin Concentrations in Beef Cattle ExhibitingDifferences in Composition of Gain

Beef steers (n = 72) of similar age, weight (651 ± 3.1 lb), and genetic background (Angus crossbred) were used to determine the effects of growing period diet on the relationship of plasma ghrelin and leptin concentrations with growth performance and carcass composition. At trial initiation (d 0), 8 steers were harvested for initial carcass composition. The remaining 64 steers were allotted, by weight, to pen and treatment was assigned randomly. Treatments were 1) a high‐forage diet fed during the growing period (0‐116 d) followed by a high‐concentrate diet during the finishing period (117‐209 d; GRW‐FNSH) or 2) a high‐concentrate diet fed for the duration of the trial (0‐209 d; FNSH‐FNSH). Steers were allowed ad libitum consumption regardless of dietary treatment. Eight steers per treatment (1 pen) were harvested on d 88, 116, 165, and 209. At each harvest date, 9‐10‐11th rib sections were dissected for chemical composition, and carcass characteristics were recorded. Replicate blood samples were collected from every steer prior to each harvest, and assayed for ghrelin, leptin, GH, insulin, and NEFA concentrations. Hormone, growth performance, and carcass composition were analyzed statistically using the GLM procedure of SAS to evaluate diet, harvest date, and their interaction. Linear, quadratic, and cubic contrasts were performed. Percent carcass protein decreased linearly (P \u3c 0.001) and percent carcass fat increased linearly (P \u3c 0.001) in both treatments. At each harvest day, FNSH‐FNSH steers had greater carcass fat (P \u3c 0.01) compared with GRW‐FNSH steers. Plasma ghrelin concentrations for FNSH‐FNSH increased quadraticly (P \u3c 0.001) over time, whereas plasma ghrelin concentrations were not different over time for GRW‐FNSH. Plasma leptin concentrations for FNSH‐FNSH increased (P \u3c 0.001) from d 0 to 88 and then plateaued, whereas plasma leptin concentrations increased linearly (P \u3c 0.001) for the GRW‐FNSH. Plasma ghrelin and leptin concentrations fluctuated relative to nutritional status, and plasma ghrelin concentrations were highest in excessively fat cattle. The role of ghrelin during fat accumulation warrants further investigation

Morphological and Chemical Mechanisms of Elongated Mineral Particle Toxicities

Much of our understanding regarding the mechanisms for induction of disease following inhalation of respirable elongated mineral particles (REMP) is based on studies involving the biological effects of asbestos fibers. The factors governing the disease potential of an exposure include duration and frequency of exposures; tissue-specific dose over time; impacts on dose persistence from in vivo REMP dissolution, comminution, and clearance; individual susceptibility; and the mineral type and surface characteristics. The mechanisms associated with asbestos particle toxicity involve two facets for each particle's contribution: (1) the physical features of the inhaled REMP, which include width, length, aspect ratio, and effective surface area available for cell contact; and (2) the surface chemical composition and reactivity of the individual fiber/elongated particle. Studies in cell-free systems and with cultured cells suggest an important way in which REMP from asbestos damage cellular molecules or influence cellular processes. This may involve an unfortunate combination of the ability of REMP to chemically generate potentially damaging reactive oxygen species, through surface iron, and the interaction of the unique surfaces with cell membranes to trigger membrane receptor activation. Together these events appear to lead to a cascade of cellular events, including the production of damaging reactive nitrogen species, which may contribute to the disease process. Thus, there is a need to be more cognizant of the potential impact that the total surface area of REMP contributes to the generation of events resulting in pathological changes in biological systems. The information presented has applicability to inhaled dusts, in general, and specifically to respirable elongated mineral particles