Lead and Helium Isotope Evidence from Oceanic Basalts for a Common Deep Source of Mantle Plumes

Linear arrays in lead isotope space for mid-ocean ridge basalts (MORBs) converge on a single end-member component that has intermediate lead, strontium, and neodymium isotope ratios compared with the total database for oceanic island basalts (OIBs) and MORBs. The MORB data are consistent with the presence of a common mantle source region for OIBs that is sampled by mantle plumes. 3He/4He ratios for MORBs show both positive and negative correlation with the 206Pb/204Pb ratios, depending on the MORB suite. These data suggest that the common mantle source is located in the transition zone region. This region contains recycled, oceanic crustal protoliths that incorporated some continental lead before their subduction during the past 300 to 2000 million years.     

Characterization of plutonium in maxey flats radioactive trench leachates

Plutonium in trench leachates at the Maxey Flats radioactive waste disposal site exists as dissolved species, primarily complexes of the tetravalent ion with strong organic ligands such as ethylenediaminetetraacetic acid. The complexes are not sorbed well by sediment and are only partly precipitated by ferric hydroxide. These results indicate the importance of isolating radioactive waste from organic matter.     

Maturation of insulin and glucose responses to normal feeding in foals

SUMMARY Postprandial insulin and glucose concentrations were measured in 3 Arabian and 3 Thoroughbred foals at 1 day, 1 week, 1 month and 3 months of age. Prefeeding serum Insulin concentrations were similar in foals at 1 day (25.9 ± 5.1 pmol/L), 1 week (32.4 ± 5.8 pmol/L), and 1 month (38.2 + 7.9 pmol/L), but had Increased significantly to 131.0 ± 20.2 pmol/L at 3 months of age (P < 0.05). There was significantly increased serum Insulin secretion after a feed In foals at 3 months of age (P < 0.05) when compared with that at younger ages. Prefeeding serum glucose concentrations ranged from 6.0 ± 0.7 mmol/L at 1 day, to 5.9 ± 0.9 mmol/L at 1 week, 4.9 ± 1.7 mmol/L at 1 month, and 4.4 ± 1.5 mmol/L at 3 months of age. There were lower postprandial glucose concentrations with advancing age. It appeared that there was a period of maturation in pancreatic β-cell function after birth in foals, which reached adult levels by 3 months of age.     

Changes in inbreeding of U.S. Herefords during the twentieth century

Genetic diversity in the U.S. Hereford population was characterized by examining the level and rate of inbreeding and effective population size. Pedigree records for 20,624,418 animals were obtained from the American Hereford Association, of which 96.1% had both parents identified. Inbreeding coefficients were computed and mean inbreeding (Fx) calculated by year from 1900 to 2001. Inbreeding increased rapidly between 1900 and 1945. From 1946, inbreeding increased linearly to a maximum of 11.5% in 1966. Throughout the 1970s and 1980s, mean inbreeding decreased to mid-century levels. Several alternatives were investigated to explain this decline. The average relationship between prominent sires fell from 20 to 12% during the time that the level of inbreeding decreased, which reflects an increase in the popularity of certain less fashionable sire lines that would have temporarily decreased inbreeding. Pedigrees were constructed for animals born after 1990. This subsample of animals with no missing ancestors in at least 12 generations did not exhibit a decrease in inbreeding. Missing ancestral information therefore contributed to the apparent decline. One cause of missing ancestry results from outcrossing to imported animals. The effect of missing ancestry was investigated by simulating the missing ancestors. In 2001, Fx was 9.8%, and approximately 95% of individuals were inbred. The maximal inbreeding coefficient was 76%. The annual change in mean inbreeding (DeltaFx) was estimated for Herefords born during five time periods from 1946 to 2001, where inbreeding was changing at different linear rates. The DeltaFx for the most recent generation (1990 to 2001) was 0.12%/yr. Assuming a generation interval of 4.88 yr, the estimated effective population size was 85. This study provides a benchmark of current genetic diversity in the Hereford population. Results indicate that inbreeding is accumulating linearly and below critical levels. Increases in the adoption of reproductive technologies could decrease genetic diversity, and in the future, we may need to consider strategies to minimize inbreeding.     

Correlated responses of carcass and reproductive traits to selection for rate of lean growth in swine

Mass selection for an index of increased postweaning average daily gain and decreased backfat thickness was practiced for five generations. Litter size and weight for 221 gilt litters, birth weight and nipple number for 2,242 piglets and weaning weight at 42 d of age for 2,111 pigs were recorded. Carcass measurements were taken on 331 pigs. Differences between means of the lines (select control) were regressed on cumulative selection differential of the index. These regression coefficients were negative (P greater than .10) for total number born, number born alive, number weaned per litter, nipple number and carcass backfat thickness. Coefficients were positive (P greater than .10) for individual pig and litter weights at birth and weaning and for the carcass traits of length, longissimus muscle area and percentage of ham and loin. Absolute values of realized genetic correlations of index with traits evaluated were all .35 or less except the correlation with carcass backfat, which was -.84. None of these was significant; therefore, index selection for lean growth should have little effect on litter size and weight but may have a beneficial effect on carcass backfat.     

The effects of Arctotheca calendula (capeweed) on digestive function of sheep

The effects of Arctotheca calendula (capeweed) on digestive function in the rumen, caecum and colon of sheep were studied. Three groups of 2-year-old Merino wethers were compared: 13 grazing capeweed-free pasture for 23 days; 8 fed 700 g of lucerne hay daily for 18 days, and 13 fed 6 kg of freshly cut capeweed (dry matter 11.3%) daily for 7 days. Capeweed did not cause diarrhoea and based on measurements of products of fermentation in the rumen, the plants were as nutritious as pasture containing grasses and clovers. The main disadvantage of capeweed in this single feeding trial was that sheep eating it lost body weight due to their inability, or lack of incentive, to consume enough dry matter.