Nutrition of the lactating beef cow

The primary purpose of this thesis was to examine the evidence relating to the effect of nutrition on the performance of single - suckled beef cows and to determine experimentally the response of autumn - calving Hereford cross British Friesian cows to three levels of energy intake during lactation.The different methods available for measuring the milk production of beef cows were discussed on the basis of information reported in the literature and two of the methods, machine -milking twice a day and a calf -suckling technique compared experimentally. It was concluded that the calf -suckling technique described is the more reliable and precise method of measuring milk production.Two experiments were reported in each of which 36 beef cows were offered individually either 175 per cent of their estimated energy requirement for maintenance (high), 125 per cent (medium), or 90 per cent (low), during the first 150 days of lactation. The rations offered consisted of grass silage and a barley -based concentrate supplement.The estimated 150 -day cumulative milk yields of beef cows in their second lactation, measured by a calf -suckling technique, were 1385 kg, 1274 kg and 1197 kg (P <0.01) on the high, medium and low planes of nutrition respectively. The corresponding figures for live -weight loss between parturition and 150 days post partum were 31 kg, 87 kg and 139 kg (P <0.001). The results demonstrated that energy deficient beef cows will attempt to sustain milk production by mobilising body reserves. It was also demonstrated that the growth rate of a suckled calf is sensitive to a reduction in milk intake during its first 150 days of life, but the weaning weights of autumn-born calves appeared unaffected by the plane of nutrition received by their dams during the winter.The implications of the results and areas of future research were discussed

Postcard: The Way It Works

This black and white printed postcard contains an illustration of a line of men walking from a Kansas bank to an Oklahoma bank. The crowd has dollar bills and bags of cash in their hand. Printed dialogue is on the top half of the card. Printed text is at the bottom of the card. Handwriting is on the back of the card.https://scholars.fhsu.edu/tj_postcards/1621/thumbnail.jp

Damped Lyman alpha systems and galaxy formation models - II. High ions and Lyman limit systems

We investigate a model for the high-ionization state gas associated with observed damped Lyman-alpha systems, based on a semi-analytic model of galaxy formation set within the paradigm of hierarchical structure formation. In our model, the hot gas in halos and sub-halos gives rise to CIV absorption, while the low-ionization state gas is associated with the cold gas in galaxies. The model matches the distribution of CIV column densities and leads naturally to kinematic properties that are in good agreement with the data. We examine the contribution of both hot and cold gas to sub-damped systems and suggest that the properties of these systems can be used as an important test of the model. We expect that sub-DLA systems will generally be composed of a single gas disk and thus predict that they should have markedly different kinematics than the damped systems. Finally, we find that hot halo gas produces less than one third of Lyman limit systems at redshift three. We model the contribution of mini-halos (halos with virial velocities < 35 km/s) to Lyman limit systems and find that they may contain as much gas as is observed in these systems. However, if we adopt realistic models of the gas density distribution we find that these systems are not a significant source of Lyman limit absorption. Instead we suggest that uncollapsed gas outside of virialized halos is responsible for most of the Lyman limit systems at high redshift.Comment: 12 pages, 8 figures, submitted to MNRA

Understanding the Structural Scaling Relations of Early-Type Galaxies

We use a large suite of hydrodynamical simulations of binary galaxy mergers to construct and calibrate a physical prescription for computing the effective radii and velocity dispersions of spheroids. We implement this prescription within a semi-analytic model embedded in merger trees extracted from the Bolshoi Lambda-CDM N-body simulation, accounting for spheroid growth via major and minor mergers as well as disk instabilities. We find that without disk instabilities, our model does not predict sufficient numbers of intermediate mass early-type galaxies in the local universe. Spheroids also form earlier in models with spheroid growth via disk instabilities. Our model correctly predicts the normalization, slope, and scatter of the low-redshift size-mass and Fundamental Plane relations for early type galaxies. It predicts a degree of curvature in the Faber-Jackson relation that is not seen in local observations, but this could be alleviated if higher mass spheroids have more bottom-heavy initial mass functions. The model also correctly predicts the observed strong evolution of the size-mass relation for spheroids out to higher redshifts, as well as the slower evolution in the normalization of the Faber-Jackson relation. We emphasize that these are genuine predictions of the model since it was tuned to match hydrodynamical simulations and not these observations.Comment: Submitted to MNRA