Neptune's eccentricity and the nature of the kuiper belt

The small eccentricity of Neptune may be a direct consequence of apsidal wave interaction with the trans-Neptune population of debris called the Kuiper belt. The Kuiper belt is subject to resonant perturbations from Neptune, so that the transport of angular momentum by density waves can result in orbital evolution of Neptune as well as changes in the structure of the Kuiper belt. In particular, for a belt eroded out to the vicinity of Neptune's 2:1 resonance at about 48 astronomical units, Neptune's eccentricity can damp to its current value over the age of the solar system if the belt contains slightly more than an earth mass of material out to about 75 astronomical units.     

Effect of dietary fibre on the performance of laying hens

1. In tests to determine whether gizzard weight could be influenced by dietary fibre concentrations, caged layers were fed on diets containing 15, 30 or 60 g pine shavings/kg diet.

2. As dietary fibre content increased, gizzard weight increased, but there was no effect on body weight, hen‐day production, egg weight, efficiency of food conversion, mortality, percentage of liver ether extract or egg shell breaking strength. Percentage of body ether extract tended to be lower when pine shavings were fed.     

Comparison of the antioxidant status in tracheal and bronchoalveolar epithelial lining fluids in recurrent airway obstruction

REASONS FOR PERFORMING STUDY: Following a period of airway inflammation the clearance of inflammatory cells along the mucociliary escalator may impose a considerable oxidant load on the trachea. OBJECTIVES: To determine the degree of oxidative stress in tracheal epithelial lining fluid (ELF) in comparison to that present in peripheral airways after an acute exposure to organic dust. METHODS: Tracheal wash fluid and bronchoalveolar lavage fluid (BALF) were collected for cytology and antioxidant analyses from 6 recurrent airway obstruction (RAO)-affected horses and 6 healthy control horses before and after stabling on straw bedding for 24 h. RESULTS: In RAO-affected horses, organic dust exposure resulted in a significant decrease in ascorbic acid concentration in tracheal ELF (P<0.0001), which was greater than the decrease in bronchoalveolar ELF (P = 0.0003). The percentage decrease in tracheal ELF ascorbic acid correlated with the percentage decrease in bronchoalveolar ELF ascorbic acid (r = 0.76; P = 0.004) following exposure. CONCLUSIONS: Acute organic dust exposure results in significant antioxidant depletion in the trachea, which may reflect inflammation and oxidative processes in peripheral airways. POTENTIAL RELEVANCE: Further work is required to evaluate the role of ascorbic acid depletion in the pathogenesis of RAO.     

Vigor and variation expressed by anther-derived doubled haploids of burley tobacco (Nicotiana tabacum L.). II. Evaluation of first- and second-cycle doubled haploids

Summary First- and second-cycle doubled haploids of burley tobacco (Nicotiana tabacum L.) were examined to ascertain the significance of source genotype on the performance of anther-derived material and to determine the magnitude of changes from the haploid-production and chromosome-doubling stages. The anther-derived lines evaluated in this study did not exhibit siginficant yield reductions. However, significant interactions between the cycle comparison and the source genotypes indicated that source genotype can affect the degree of vigor reduction observed. Significant variation was also observed among the second-cycle doubled haploids examined in this study. Partitioning of this variation indicates that most of it is due to alteration present at the haploid-production step instead of the chromosome-doubling step. In general, the variation present in the second-cycle doubled haploids was distributed around the values observed for the source first-cycle doubled haploids. Even though unexpected variation is often observed in anther-derived materials, these results suggest that reduced vigor is not intrinsically associated with androgenetic lines of burley tobacco. The most plausible explanations for the variation and vigor losses in anther-derived lines propose that natural phenomena, given the opportunity for expression via anther culture, are responsible. Spontaneous variants present in the gametic pool of inbreds or first-cycle doubled haploids offer one possible explanation for the performance observed in anther-derived lines of tobacco.Contribution from the Department of Agronomy, University of Kentucky, Lexington, KY 40546-0091. This research was supported, in part, by a grant from R. J. Reynolds Tobacco Co. This paper (no. 85-3-29) is published with the approval of the Director of the Kentucky Agricultural Experiment Station.     

Successful Non-Surgical Transfer of Horse Embryos to Mule Recipients

Mules, hybrids resulting from the mating of a horse mare (Equus caballus, 2n = 64) to a Jack donkey (E. asinus, 2n = 62), are generally infertile. Five horse embryos were transferred non‐surgically to two cyclic and one acyclic recipient mules. In the mares and cycling mules, oestrus and ovulation were induced with, respectively, d ‐cloprostenol and human chorionic gonadotrophin (hCG). The acyclic mule, on the other hand, received oestradiol benzoate when the embryo donor was showing oestrus and progesterone after the donor had ovulated and until pregnancy diagnosis. Non‐surgical embryo collections were attempted on day 7 after ovulation and recovered embryos were transferred transcervically into the mules’ uteri. Mules that became pregnant were blood sampled serially for equine chorion gonadotrophin (eCG), progestagen and total conjugated oestrogen concentrations until around 6 months of gestation. The three embryos transferred to the acyclic mule did not produce any pregnancies whereas both embryos transferred to the cycling mules resulted in the birth of live foals. The peak concentration and duration of secretion of eCG differed markedly between the two pregnant mules, although both animals appeared to develop secondary corpora lutea beyond day 40 of gestation, as in normal intraspecies horse pregnancy. Moreover, the rise in serum oestrogen concentrations from around day 90 was also similar to that seen in normal pregnant mares. Parturition occurred spontaneously on day 348 of gestation in both mules and the resulting colt foals developed normally to weaning. Thus, cycling mules can carry a horse conceptus after non‐surgical embryo transfer and give birth to a normal mature foal.     

Dental wear and growth performance in steers fed sweetpotato cannery waste

OBJECTIVE: To determine whether feeding sweetpotato cannery waste (SPCW) to cattle had adverse effects on dental wear, growth performance, or ruminal tissues. DESIGN: Clinical trial. ANIMALS: 36 Holstein steers. PROCEDURE: Steers were assigned to 1 of 3 groups. All steers received ryegrass hay ad libitum. In addition, steers in group 1 were fed 3.2 kg of corn and soybean meal/steer/d, steers in group 2 were fed 0.45 kg of soybean meal/steer/d and SPCW ad libitum, and steers in group 3 were fed a mixture of SPCW and broiler litter ad libitum. Samples of rumen fluid were collected on day 56. Steers were slaughtered on day 84, and samples of rumen were submitted for histologic examination. Teeth from control steers were removed, and calcium ion loss in response to etching with 2.28% lactic acid solutions buffered to pH of 3.75, 4.0, 4.25, 4.5, and 4.75 was determined. RESULTS: Average daily gain was lower for steers fed SPCW than for steers in the other 2 groups. Steers fed the SPCW-broiler litter mixture had only mild increases in tooth wear and tooth color scores, compared with control steers, whereas steers fed unbuffered SPCW had substantial increases in tooth wear and tooth color scores. Histologic abnormalities were detected in rumens from steers fed diets containing SPCW. Calcium ion loss decreased as pH of the etching solution increased. CLINICAL IMPLICATIONS: Results indicate that feeding cattle unbuffered SPCW can cause dental erosion, ruminal epithelial changes, and poor growth; however, SPCW buffered with broiler litter can be used as a cattle feed.     

From trees to fleas: masting indirectly affects flea abundance on a rodent host

Mast seeding causes strong fluctuations in populations of forest animals. Thus, this phenomenon can be used as a natural experiment to examine how variation in host abundance affects parasite loads. We investigated fleas infesting yellow-necked mice in beech forest after 2 mast and 2 non-mast years. We tested 2 mutually exclusive scenarios: (1) as predicted by classical models of density-dependent transmission, an increase in host density will cause an increase in ectoparasite abundance (defined as the number of parasites per host), versus (2) an increase in host density will cause a decline in flea abundance (“dilution,” which is thought to occur when parasite population growth is slower than that of the host). In addition, we assessed whether masting alters the relationship between host traits (sex and body mass) and flea abundance. We found a hump-shaped relationship between host and flea abundance. Thus, the most basic predictions are too simple to describe ectoparasite dynamics in this system. In addition, masting modified seasonal dynamics of flea abundance, but did not affect the relationship between host traits and flea abundance (individuals with the highest body mass hosted the most fleas; after controlling for body mass, parasite abundance did not vary between sexes). Our results demonstrate that pulses of tree reproduction can indirectly, through changes in host densities, drive patterns of ectoparasite infestation.