Genetic Characteristics Required in Dairy and Beef Cattle for Temperate Grazing Systems

Key points Only about 10% of the world’s milk is produced from grazing systems. Consequently the majority of dairy cattle have not been selected under grazing, nor on seasonal systems. This is not true for beef cattle, for which the majority, especially the dams, are managed under seasonal grazing systems. In grazing systems daily feed intake is limited to lower levels than are achievable on concentrate plus conserved forage rations. Consequently, cows most suited to grazing environments are likely to have a lower genetic potential for milk production than cows selected in high concentrate systems, to minimise their relative energy deficit. The traits required under grazing will include those for other systems; high yields of milk with high milk solids, efficient converters of feed to product, functionality, good fertility, health and longevity. Successful grazing systems require dairy cows that are adapted to achieving large intakes of forage relative to their potential milk yields, and therefore able to meet production potential exclusively from forage. Grazing cattle must also be able to walk long distances, and in seasonal systems, must be able to conceive and calve once every year. The ability to be productive when milked once daily may also be desirable in low cost grazing systems in the future. Intensive selection for milk production within the Holstein-Friesian breed on high concentrate diets has generally resulted in a genotype that is not well suited to grazing (high forage) systems, in which these cows exist in permanent energy deficit. This unsuitability is particularly true for seasonal systems, for which good fertility is an essential trait. There is now strong evidence for the existence of interactions between genotype of dairy cattle and feeding system, where the genetics and the systems differ widely. Therefore mutual compatibility between the cow and the system must be optimised for production and profit. The New Zealand Friesian and New Zealand Jersey, and crosses between them, or with other dairy breeds, including the North American Holstein-Friesian, have been shown to be well suited to grazing systems. Increasing evidence suggests that genetics from some Scandinavian breeding programs, e.g. the Norwegian Red, may also be suited to grazing systems, where good fertility is essential. Developments in international sire evaluation (adaptations of multiple across country evaluation (MACE)) that enable differences in management systems to be taken into account will provide different breeding values for different conditions. Until then, sires should be proven in the same general management conditions in which the daughters are to be managed. There is little evidence of important G x E interactions in beef cattle, for growth rate, food intake or carcass traits. But beef cows from large, late maturing breeds are relatively more restricted by inadequate nutrition than smaller early maturing types. As a result both their fertility and milk production can be impaired leading to a lower weaning percentage and lighter weaning weight. Interactions between the effects of genotype and nutrition on carcass composition can occur where the level of energy intake is above the muscle deposition capacity of some breeds

Are the distributions of Fast Radio Burst properties consistent with a cosmological population?

High time resolution radio surveys over the last few years have discovered a population of millisecond-duration transient bursts called Fast Radio Bursts (FRBs), which remain of unknown origin. FRBs exhibit dispersion consistent with propagation through a cold plasma and dispersion measures indicative of an origin at cosmological distances. In this paper we perform Monte Carlo simulations of a cosmological population of FRBs, based on assumptions consistent with observations of their energy distribution, their spatial density as a function of redshift and the properties of the interstellar and intergalactic media. We examine whether the dispersion measures, fluences, inferred redshifts, signal-to-noises and effective widths of known FRBs are consistent with a cosmological population. Statistical analyses indicate that at least 50 events at Parkes are required to distinguish between a constant co-moving FRB density, and a FRB density that evolves with redshift like the cosmological star formation rate density.Comment: 11 pages, 7 figures, 3 table

Relativistic spin precession in the binary PSR J1141−-6545

PSR J1141$-$6545 is a precessing binary pulsar that has the rare potential to reveal the two-dimensional structure of a non-recycled pulsar emission cone. It has undergone $\sim 25 \deg$ of relativistic spin precession in the $\sim18$ years since its discovery. In this paper, we present a detailed Bayesian analysis of the precessional evolution of the width of the total intensity profile, to understand the changes to the line-of-sight impact angle ($\beta$) of the pulsar using four different physically motivated prior distribution models. Although we cannot statistically differentiate between the models with confidence, the temporal evolution of the linear and circular polarisations strongly argue that our line-of-sight crossed the magnetic pole around MJD 54000 and that only two models remain viable. For both these models, it appears likely that the pulsar will precess out of our line-of-sight in the next $3-5$ years, assuming a simple beam geometry. Marginalising over $\beta$ suggests that the pulsar is a near-orthogonal rotator and provides the first polarization-independent estimate of the scale factor ($\mathbb{A}$) that relates the pulsar beam opening angle ($\rho$) to its rotational period ($P$) as $\rho = \mathbb{A}P^{-0.5}$ : we find it to be $> 6 \rm~deg~s^{0.5}$ at 1.4 GHz with 99\% confidence. If all pulsars emit from opposite poles of a dipolar magnetic field with comparable brightness, we might expect to see evidence of an interpulse arising in PSR J1141$-$6545, unless the emission is patchy.Comment: Accepted for publication in Astrophysical Journal Letter

On embedding of the Bratteli diagram into a surface

We study C*-algebras O_{\lambda} which arise in dynamics of the interval exchange transformations and measured foliations on compact surfaces. Using Koebe-Morse coding of geodesic lines, we establish a bijection between Bratteli diagrams of such algebras and measured foliations. This approach allows us to apply K-theory of operator algebras to prove strict ergodicity criterion and Keane's conjecture for the interval exchange transformations.Comment: final versio

Effects of Supplementary Concentrate Level and Separate or Mixed Feeding of Grass Silage and Concentrates on Rumen Fluid Composition in Steers

The effects of dietary concentrate level and method of feeding (separate or mixed) on performance and carcass traits of steers may be mediated through changes in rumen fluid composition. The objectives of this study were to determine the effects on rumen fluid composition of (1) supplementary concentrate level with grass silage, and (2) separate or mixed feeding of silage and concentrates

Effects of Supplementary Concentrate Level and Separate or Mixed Feeding of Grass Silage and Concentrates on Carcass Tissue Composition in Steers

Supplementary concentrate level may affect carcass composition in steers. Feeder wagons facilitate feeding and management. The objectives were to determine the effects of (1) supplementary concentrate level with grass silage, and (2) separate or mixed feeding of silage and concentrates, on ribs joint composition