Breeding Objectives Indicate Value of Genomics for Beef Cattle

Genomics may have much to offer in the implementation of breeding objectives. Advantages of genomic prediction include increased accuracy of expected progeny differences (EPDs) for traits that have been components of routine genetic evaluations. Perhaps more importantly, genomic prediction makes it possible to include traits that are too costly or too difficult to measure, and traits that are measured too late in life or are sex-limited such that candidates for selection cannot have EBV with high accuracy at the time when selection decisions are made. Genomically enhanced EPDs may also allow for a marked reduction in generation interval, thus accelerating the annual rate of genetic improvement. Here, the value of genomic prediction, on a trait-by-trait basis, is extended to explore the contribution of genomic prediction to selection for a multitrait breeding objective indicative of economic merit. A simple two-trait objective indicative of feed efficiency is illustrated first, followed by objectives for terminal and maternal strains of Angus

Breeding objectives for Angus and Charolais specialized sire lines for use in the emerging sector of South African beef production

Breeding indigenous cows to terminal sires may facilitate production of calves in the emerging sector that better meet commercial feedlot requirements. Thus, the objective of this research was to develop breeding objectives for Angus and Charolais terminal sires to be used in breeding Afrikaner, Bonsmara, and Nguni cows. An aggregated simulation model that is reliant on user inputs for the phenotypic characterization of the germplasm and economic characterization of the production environment was developed. Relative economic values were calculated by approximating partial derivatives of simulated profit with respect to economically relevant traits. Correlations among the breeding objectives calculated from simulations of Angus and Charolais bulls bred to Afrikaner, Bonsmara and Nguni cows were consistently > 0.9. Thus, an average index could be used for all six scenarios with little loss of selection efficiency. On average, relative emphasis given to breeding values for survival, direct weaning weight, postweaning daily gain, postweaning daily feed intake, dressing percent, and fat depth were 31.1, 31.0, 17.3, 1.4, 19.1, 0.2%, respectively. These breeding objectives may be viewed as an appropriate step in the evolution of multi-trait selection to facilitate poverty alleviation among cattle producers in the emerging sector through wealth creation resulting from their production of calves for industrial feeding. Keywords: Beef cattle, genetic evaluation, selection strategy, crossbreeding, cow-calf production system South African Journal of Animal Science Vol. 37 (1) 2007: pp. 1-1

Signatures of Coronal Loop Opening via Interchange Reconnection in the Slow Solar Wind at 1 AU

The opening of closed magnetic loops via reconnection with open solar flux, so called “interchange reconnection”, is invoked in a number of models of slow solar wind release. In the heliosphere, this is expected to result in local switchbacks or inversions in heliospheric magnetic flux (HMF). When observed at 1 AU, inverted HMF has previously been shown to exhibit high ion charge states, suggestive of hot coronal loops, and to map to the locations of coronal magnetic separatrices. However, simulations show that inverted HMF produced directly by reconnection in the low corona is unlikely to survive to 1 AU without the amplification by solar wind speed shear. By considering the surrounding solar wind, we show that inverted HMF is preferably associated with regions of solar wind shear at 1 AU. Compared with the surrounding solar wind, inverted HMF intervals have lower magnetic field intensity and show intermediate speed and density values between the faster, more tenuous wind ahead and the slower, denser wind behind. There is no coherent signature in iron charge states, but oxygen and carbon charge states within the inverted HMF are in agreement with the higher values in the slow wind behind. Conversely, the iron-to-oxygen abundance ratio is in better agreement with the lower values in the solar wind ahead, while the alpha-to-proton abundance ratio shows no variation. One possible explanation for these observations is that the interchange reconnection (and subsequent solar wind shear) that is responsible for generation of inverted HMF involves very small, quiet-Sun loops of approximately photospheric composition, which are impulsively heated in the low corona, rather than large-scale active region loops with enhanced first-ionisation potential elements. Whether signatures of such small loops could be detected in situ at 1 AU still remains to be determined

Evlauation of Breeds and Breed Crosses for the Production of Weaning Weight in South Dakota

Records on 41,403 calves from 324 contemporary groups were studied to determine the effect of a calf\u27s breed background on its weaning weight. Calves with the heaviest weaning weights were crossbred, typically sired by Continental breed bulls and out of crossbred dams

Simulations of a lattice model of two-headed linear amphiphiles: influence of amphiphile asymmetry

Using a 2D lattice model, we conduct Monte Carlo simulations of micellar aggregation of linear-chain amphiphiles having two solvophilic head groups. In the context of this simple model, we quantify how the amphiphile architecture influences the critical micelle concentration (CMC), with a particular focus on the role of the asymmetry of the amphiphile structure. Accordingly, we study all possible arrangements of the head groups along amphiphile chains of fixed length $N=12$ and 16 molecular units. This set of idealized amphiphile architectures approximates many cases of symmetric and asymmetric gemini surfactants, double-headed surfactants and boloform surfactants. Consistent with earlier results, we find that the number of spacer units $s$ separating the heads has a significant influence on the CMC, with the CMC increasing with $s$ for $s<N/2$. In comparison, the influence of the asymmetry of the chain architecture on the CMC is much weaker, as is also found experimentally.Comment: 30 pages, 17 fgure

Retained Ownership of Beef Cattle When Considering Production and Price Risk

Livestock Production/Industries,

Economic selection index development for Beefmaster cattle I: Terminal breeding objective

The objective of this study was to develop an economic selection index for Beefmaster cattle in a terminal production system where bulls are mated to mature cows with all resulting progeny harvested. National average prices from 2010 to 2014 were used to establish income and expenses for the system. Phenotypic and genetic parameter values among the selection criteria and goal traits were obtained from literature. Economic values were estimated by simulating 100,000 animals and approximating the partial derivatives of the profit function by perturbing traits one at a time, by 1 unit, while holding the other traits constant at their respective means. Relative economic values (REV) for the terminal objective traits HCW, marbling score (MS), ribeye area (REA), 12th–rib fat (FAT), and feed intake (FI) were 91.29, 17.01, 8.38, -7.07, and -29.66, respectively. Consequently, improving the efficiency of beef production is expected to impact profitability greater than improving carcass merit alone. The accuracy of the index lies between 0.338 (phenotypic selection) and 0.503 (breeding values known without error). The application of this index would aid Beefmaster breeders in their sire selection decisions, facilitating genetic improvement for a terminal breeding objective

Simulations of a lattice model of two-headed linear amphiphiles: influence of amphiphile asymmetry

Using a 2D lattice model, we conduct Monte Carlo simulations of micellar aggregation of linear-chain amphiphiles having two solvophilic head groups. In the context of this simple model, we quantify how the amphiphile architecture influences the critical micelle concentration (CMC), with a particular focus on the role of the asymmetry of the amphiphile structure. Accordingly, we study all possible arrangements of the head groups along amphiphile chains of fixed length $N=12$ and 16 molecular units. This set of idealized amphiphile architectures approximates many cases of symmetric and asymmetric gemini surfactants, double-headed surfactants and boloform surfactants. Consistent with earlier results, we find that the number of spacer units $s$ separating the heads has a significant influence on the CMC, with the CMC increasing with $s$ for $s<N/2$. In comparison, the influence of the asymmetry of the chain architecture on the CMC is much weaker, as is also found experimentally.Comment: 30 pages, 17 fgure

Economic selection index development for Beefmaster cattle II: General-purpose breeding objective

An economic selection index was developed for Beefmaster cattle in a general-purpose production system in which bulls are mated to a combination of heifers and mature cows, with resulting progeny retained as replacements or sold at weaning. National average prices from 2010 to 2014 were used to establish income and expenses for the system. Genetic parameters were obtained from the literature. Economic values were estimated by simulating 100,000 animals and approximating the partial derivatives of the profit function by perturbing traits 1 at a time, by 1 unit, while holding the other traits constant at their respective means. Relative economic values for the objective traits calving difficultly direct (CDd), calving difficulty maternal (CDm), weaning weight direct (WWd), weaning weight maternal (WWm), mature cow weight (MW), and heifer pregnancy (HP) were −2.11, −1.53, 18.49, 11.28, −33.46, and 1.19, respectively. Consequently, under the scenario assumed herein, the greatest improvements in profitability could be made by decreasing maintenance energy costs associated with MW followed by improvements in weaning weight. The accuracy of the index lies between 0.218 (phenotypic-based index selection) and 0.428 (breeding values known without error). Implementation of this index would facilitate genetic improvement and increase profitability of Beefmaster cattle operations with a general-purpose breeding objective when replacement females are retained and with weaned calves as the sale end point

Genetic Correlations of Reproductive and Maternal Traits with Growth and Carcass Traits in Beef Cattle

Some genes may affect more than one trait. Therefore, the traits can be genetically correlated. Knowledge of genetic correlations among traits is useful for efficient selection of replacement bulls and heifers if the breeder considers more than one trait. In designed selection programs, emphasis to be placed on the various traits can depend, in part, on the genetic correlations among them. In addition, genetic correlations can be used to predict what is expected to happen to traits other than those used in selection as a result of that selection. This effect on traits other than those used in selection is referred to as correlated response. The objective of this study was to estimate from experimental data the genetic correlations between reproductive and maternal traits of beef females and growth and carcass traits of paternal half-sib steers. A more detailed account of the methodology and results can be found in the Journal of Animal Science, volume 58, pages 1171 to 1180