Relationships between morphological and chemical characteristics of perennial ryegrass varieties and intake by sheep under continuous stocking management

Plots of five intermediate-heading varieties of perennial ryegrass (Lolium perenne L.) [AberDove, Belramo and Glen (diploid); Twins (tetraploid); and AberExcel (tetraploid hybrid)] were continuously stocked with sheep to maintain a target sward surface height of 4050 mm. Daily dry matter (DM) intake was significantly different (F-value = 0.032) between the varieties, with the tetraploid hybrid AberExcel having the highest values for daily DM intake and intake rate during eating. Amongst the diploid varieties, intake rate tended to be higher for sheep grazing Glen. The varieties comprised a wide range in potential growth habit, from the relatively prostrate, highly tillered Glen to the more-erect AberExcel and there were differences between them in the vertical distribution of leaves within the sward canopy. The leaves of AberExcel weighed 3.6 mg DM cm(-2) leaf area in contrast to the other varieties (4.3-5.3 mg DM cm(-2) leaf area) resulting in a high leaf area index (LAI) in relation to the green leaf mass. Intake rate was not significantly correlated with extended tiller and sheath tube lengths, partition of herbage mass, number of tillers per square metre or LAI. However, canonical variates analysis showed that there were significant differences between the varieties for the morphological and chemical factors examined. Other factors also need to be explored to explain these differences in ingestive behaviour in order to identify plant traits that are correlated with herbage intake rate. These are needed for varieties destined for grazing use, both during the breeding programme and their subsequent evaluation

Intake Characteristics and Performance of Contrasting Grass Varieties Continuously Stocked with Sheep

Fifteen intermediate-heading perennial ryegrass (Lolium perenne) varieties were grazed by sheep under continuous variable stocking management. Mean daily grass dry matter intake per ewe was positively correlated with liveweight gain per ewe (r = 0.63) and per ha (r = 0.58) over an 8-month grazing season. Daily intake was not correlated with grazing time (r = 0.12) but was positively correlated with instantaneous dry matter intake rate (r = 0.75). Breeding varieties with high intake rate characteristics should allow increases in the contribution of grazed grass to grassland-based livestock farming. There is now a need to identify morphological and chemical characteristics of varieties that are correlated with high intake rate and a need to develop tools, which enable these traits to be identified rapidly in grass breeding programmes

Intake Characteristics of Diploid and Tetraploid Perennial Ryegrass Varieties when Grazed by Simmental x Holstein Yearling Heifers Under Rotational Stocking Management

Orr et al. (2003) measured large differences in dry matter (DM) intake rate between 15 intermediate-heading perennial ryegrass varieties when they were continuously stocked with sheep and subsequently explored the extent to which, for 5 of these varieties, these differences could be explained by chemical and morphological traits (Orr et al., 2004a) which could be targeted in grass breeding programmes. Here, four of the 15 varieties, which within ploidy had low or high intake characteristics when grazed by sheep, were rotationally stocked with cattle and intake and sward factors were measured

Microwave Electronics

Contains reports on four research projects.Lincoln Laboratory (Purchase Order DDL B-00306)United States Navy, Office of Naval Research (Contract Nonr-1841(49))United States Air Force (Contract AF19(604)-5200)United States NavyUnited States Arm

Tryptophan metabolism in the central nervous system: medical implications

The metabolism of the amino acid L-tryptophan is a highly regulated physiological process leading to the generation of several neuroactive compounds within the central nervous system. These include the aminergic neurotransmitter serotonin (5-hydroxytryptamine, 5-HT), products of the kynurenine pathway of tryptophan metabolism (including 3-hydroxykynurenine, 3-hydroxyanthranilic acid, quinolinic acid and kynurenic acid), the neurohormone melatonin, several neuroactive kynuramine metabolites of melatonin, and the trace amine tryptamine. The integral role of central serotonergic systems in the modulation of physiology and behaviour has been well documented since the first description of serotonergic neurons in the brain some 40 years ago. However, while the significance of the peripheral kynurenine pathway of tryptophan metabolism has also been recognised for several decades, it has only recently been appreciated that the synthesis of kynurenines within the central nervous system has important consequences for physiology and behaviour. Altered kynurenine metabolism has been implicated in the pathophysiology of conditions such as acquired immunodeficiency syndrome (AIDS)-related dementia, Huntington's disease and Alzheimer's disease. In this review we discuss the molecular mechanisms involved in regulating the metabolism of tryptophan and consider the medical implications associated with dysregulation of both serotonergic and kynurenine pathways of tryptophan metabolism

A millisecond pulsar in a stellar triple system

Gravitationally bound three-body systems have been studied for hundreds of years and are common in our Galaxy. They show complex orbital interactions, which can constrain the compositions, masses, and interior structures of the bodies and test theories of gravity, if sufficiently precise measurements are available. A triple system containing a radio pulsar could provide such measurements, but the only previously known such system, B1620-26 (with a millisecond pulsar, a white dwarf, and a planetary-mass object in an orbit of several decades), shows only weak interactions. Here we report precision timing and multi-wavelength observations of PSR J0337+1715, a millisecond pulsar in a hierarchical triple system with two other stars. Strong gravitational interactions are apparent and provide the masses of the pulsar (1.4378(13) Msun, where Msun is the solar mass and the parentheses contain the uncertainty in the final decimal places) and the two white dwarf companions (0.19751(15) Msun and 0.4101(3) Msun), as well as the inclinations of the orbits (both approximately 39.2 degrees). The unexpectedly coplanar and nearly circular orbits indicate a complex and exotic evolutionary past that differs from those of known stellar systems. The gravitational field of the outer white dwarf strongly accelerates the inner binary containing the neutron star, and the system will thus provide an ideal laboratory in which to test the strong equivalence principle of general relativity.Comment: 17 pages, 3 figures, 1 table. Published online by Nature on 5 Jan 2014. Extremely minor differences with published version may exis