Stealing the riches: using the human genome project for livestock research

The document attached has been archived with permission from the Australian Association of Cattle Veterinarians.The human genome project has brought a new era not only to medical genetics, but also to livestock molecular genetics. By 'borrowing' everything from techniques and research strategies to actual data from the human genome project, geneticists are making significant progress in applying DNA biotechnologies to livestock production. These applications include parentage testing, identity testing, and diagnostic testing of genetic disorders. Another important application is selection of superior animals for breeding programs by identifying those carrying specific genes. Examples of these applications will be discussed from our work on cattle and sheep molecular genetics

Evidence of non-additive genetic effects on predicted carcass composition

The document attached has been archived with permission from the World Congress on Genetics Applied to Livestock Production.Genetic effects on pre- and post-weaning body weight and developmental traits of Jersey and Limousin cross cattle has been reported (Afolayan et al., 2001). As in this earlier study which indicated the importance of epistasis at older ages, maternal effects (Meyer, 1992) and heterotic effects (Pitchford et al., 1993) have also been found on post-weaning growth traits of some breed of beef cattle. Genetic improvement programs in beef cattle could be enhanced through understanding of the genetic effects on live animal traits at various ages. However, the value of beef cattle lies better in their ability to efficiently produce a carcass composed of optimal proportions of muscle, bone and fat at market weight (Tatum et al., 1986). In essence, the knowledge of the genetic effects on different carcass components is of more importance to the breeders/producers of livestock. This study, therefore, examines the estimates of four genetic effects on predicted carcass traits using live-animal measurements

Genetics of seam fat in cattle

The document attached has been archived with permission from the World Congress on Genetics Applied to Livestock Production.As far as most consumers are concerned, a good steak is a steak with visibly desirable colour (doneness), a large portion of muscle and a small amount of fat, especially the seam fat located between the muscles. During the intensive growth to commercial slaughter weights in feedlots, there is a distinct change in the composition of the body with the amount of fat increasing and the musculature remaining reasonably constant (Pitchford and Bottema, 2000). Cattle breeds deposit fat at different rates and in different locations (subcutaneous, intermuscular or intramuscular). For example, early maturing Jersey cattle deposit more fat intramuscularly than late maturing Limousin cattle (Pitchford and Bottema, 2000). These differences suggest that there is a genetic basis for fat distribution. The aim of this study was to investigate the genetic variation in seam fat distribution within loin muscles of Jersey and Limousin cross cattle, independent from carcass size and fatness

QTL for feed intake and associated traits

The document attached has been archived with permission from the World Congress on Genetics Applied to Livestock Production.In typical beef cattle production systems, the breeding herd accounts for 65-85% of the total feed requirements (Ferrell and Jenkins, 1984 ; Montaldo-Bermudez et al., 1990) and 65-75% of this is used for maintenance. Primarily, the very large maintenance requirement is because cattle are a large, slowly maturing species with a low annual reproductive rate. Furthermore, only a single product is harvested (meat). Any improvement in the efficiency with which breeding cows maintain body weight, will result in an increase in total meat production for a given amount of feed. The key to selection for increased efficiency is to be able to accurately measure feed intake, a trait that is both difficult and expensive to measure. A less expensive alternative would be to use a DNA test for markers of genes affecting intake. This approach has the potential to significantly reduce the generation interval. The aim of this project is to locate regions (quantitative trait loci, QTL) in the cattle genome that contain genes affecting intake.W.S. Pitchford, M.L. Fenton, A.J. Kister and C.D.K. Bottem

Global Spiral Modes in NGC 1566: Observations and Theory

We present an observational and theoretical study of the spiral structure in galaxy NGC 1566. A digitized image of NGC 1566 in I-band was used for measurements of the radial dependence of amplitude variations in the spiral arms. We use the known velocity dispersion in the disk of NGC 1566, together with its rotation curve, to construct linear and 2D nonlinear simulations which are then compared with observations. A two-armed spiral is the most unstable linear global mode in the disk of NGC 1566. The nonlinear simulations are in agreement with the results of the linear modal analysis, and the theoretical surface amplitude and the velocity residual variations across the spiral arms are in qualitative agreement with the observations. The spiral arms found in the linear and nonlinear simulations are considerably shorter than those observed in the disk of NGC 1566. We argue therefore, that the surface density distribution in the disk of the galaxy NGC 1566 was different in the past, when spiral structure in NGC 1566 was linearly growing.Comment: 41 pages, 20 figures, to be published in the Astrophysical Journa

Kinematics and dynamics of the "superthin" edge-on disk galaxy IC 5249

We present spectroscopic observations of the stellar motions in the disk of the superthin edge-on spiral galaxy IC 5249 and re-analyse synthesis observations of the HI. We find that the HI rotation curve rises initially to about 90-100 km/s, but contrary to the conclusion of Abe et al. (1999) flattens well before the edge of the optical disk. Over most part of the optical disk we have been able to establish that the (tangential) stellar velocity dispersion is 25-30 km/s. From earlier surface photometry we adopt a value for the radial scalelength of the disk of 7 +/- 1 kpc, a vertical scaleheight of 0.65 +/- 0.05 kpc and a disk truncation radius of 17 +/- 1 kpc. The very thin appearance of IC 5249 on the sky is the result of a combination of a low (face-on) surface brightness, a long scalelength and a a sharp truncation at only about 2.5 scalelengths. From various arguments we derive the stellar velocity dispersions at a position one radial scalelength as sigma_R about 35 km/s, sigma_{theta} about 30 km/s and sigma_z about 20 km/s. This is comparable to the values for the disk of our Galaxy in the solar neighborhood.Comment: 11 pages and 8 figures. Accepted for Astronomy and Astrophysics (September 2001

Galaxies with Spiral Structure up to z = 0.87 --Limits on M/L and the Stellar Velocity Dispersion

We consider seven distant galaxies with clearly evident spiral structure from HST images. Three of these were chosen from Vogt et al. (1996) (VFP) and have measured rotational velocities. Five were chosen from the Medium Deep Survey and are studied in Sarajedini et al. 1996 (SGGR), and one galaxy is found in both papers. We place upper limits on their mass-to-light ratios (M/L) by computing M/L_B for a maximal disk. We find that these galaxies have maximal disk mass-to-light ratios M/L_B = 1.5 - 3.5 M_sol/L_Bsol at the low end, but within the range seen in nearby galaxies. The mass-to-light ratios are low enough to suggest that the galaxies contain a young, rapidly formed stellar population. By using a Toomre stability criterion for formation of spiral structure, we place constraints on the ratio of M/L to the stellar velocity dispersion. If these galaxies have maximal disks they would have to be nearly unstable so as to have small enough velocity dispersions that their disks are not unrealistically thick. This suggests that there is a substantial amount of dark matter present in the luminous regions of the galaxy.Comment: AAS Latex + PS Figure, accepted for publication in A

Truncations of stellar disk and warps of HI-layers in edge-on spiral galaxies

Edge-on spiral galaxies often have stellar disks with relatively sharp truncations and warped HI-layers in the outer parts. Warps appear to start preferentially near the optical boundaries of the disks. Here we make a comparative study of warps and truncations in edge-on galaxies. The Garc\'{\i}a-Ruiz et al. (2002) sample with extensive HI-mapping is complemented with luminosity distributions from the Sloan Digital Sky Survey. The method to identify truncations has been tested using the sample of edge-on galaxies of van der Kruit & Searle. Results are: (i.) The majority (17 out of 23) of the galaxies show evidence for truncations. (ii.) When an HI-warp is present it starts at 1.1 truncation radii. (iii.) This supplements the rules for warps formulated by Briggs (1990), if the Holmberg radius is replaced for edge-on systems with the truncation radius. (iv.) The truncation radius and the onset of the warps coincide radially with features in the rotation curve and the HI surface density. The latter is also true for less inclined systems. (v.) Inner disks are very flat and the onset of the warp just beyond the truncation radius is abrupt and discontinuous. These findings suggest that the inner flat disk and the outer warped disk are distinct components with quite different formation histories, probably involving quite different epochs. The inner disk forms initially and the warped outer disk forms as a result of much later infall of gas with a higher angular momentum in a different orientation. In an appendix the Holmberg radius is discussed. Contrary to what is often assumed Holmberg radii are not corrected for inclination.Comment: Accepted for pubication by Astronomy & Astrophysic