Biomedical subjects

S Avendaño

Publications and source records attributed to S Avendaño.

At least 19 recordsLinked to original sources

PubMed2005

Prediction of accuracy of estimated Mendelian sampling terms.

This study describes a general framework for predicting the accuracy of Mendelian sampling terms when truncation selection is applied on best linear unbiased prediction (BLUP) estimated breeding values. A selection index approach is followed. The pseudo-BLUP index is extended to include terms related to the Mendelian sampling term. Predicted accuracies are compared with those obtained through stochastic computer simulation. Good predictions for the accuracy of the Mendelian sampling term were obtained both at selection time and at convergence of long-term contributions of selected candidates for a range of heritabilities and population structures. The prediction approach developed provides a key tool for obtaining predictions of genetic response from quadratic optimization that maximizes the rate of genetic progress while restricting the rate of inbreeding.

Breeding↗

PubMed2005

Effect of gamma irradiation on the microbiological quality of minimally processed vegetables.

The initial microflora of minimally processed celery and cabbage packaged under a modified atmosphere was determined. The samples came from the same producer and were sold in a supermarket chain of Santiago, Chile. Although neither E. coli nor Salmonella spp. were detected, initial total plate and Enterobacteriaceae counts were high (= 10(5) cfu/g), not meeting in most cases the specifications of the Chilean legislation. The D10 value for two strains of E. coli (ATCC 8739 and a wild type) inoculated as indicator microorganisms was determined. After irradiating with 5 D10 doses (1kGy), the variation of the microbial population and sensory quality during a 7 days storage period at 5 degrees C was studied. In irradiated celery, a reduction of 4.7 and 3.8 logs for total plate and Enterobacteriaceae counts respectively was observed. There was a decrease of 3.8 and 3.6 logs in cabbage for total plate and Enterobacteriaceae counts respectively. In both irradiated and non-irradiated vegetables, neither E. coli nor Salmonella spp. were detected. An increase of 1.6 - 1.7 logs in both microbiological parameters in non-irradiated samples was observed during storage. In irradiated products, only celery showed an increase of 1.2 log in total plate count. Both Enterobacteriaceae count in the two vegetables and Total plate count in cabbage presented essentially no variation in time. No significant differences (p = 0.05) were detected in sensory total quality between the control and the irradiated vegetable and between days of storage.

Apium↗

PubMed2004

Mendelian sampling terms as a selective advantage in optimum breeding schemes with restrictions on the rate of inbreeding.

Quadratic indices are a general approach for the joint management of genetic gain and inbreeding in artificial selection programmes. They provide the optimal contributions that selection candidates should have to obtain the maximum gain when the rate of inbreeding is constrained to a predefined value. This study shows that, when using quadratic indices, the selective advantage is a function of the Mendelian sampling terms. That is, at all times, contributions of selected candidates are allocated according to the best available information about their Mendelian sampling terms (i.e. about their superiority over their parental average) and not on their breeding values. By contrast, under standard truncation selection, both estimated breeding values and Mendelian sampling terms play a major role in determining contributions. A measure of the effectiveness of using genetic variation to achieve genetic gain is presented and benchmark values of 0.92 for quadratic optimisation and 0.5 for truncation selection are found for a rate of inbreeding of 0.01 and a heritability of 0.25.

Analysis of Variance↗

PubMed2003

Expected increases in genetic merit from using optimized contributions in two livestock populations of beef cattle and sheep.

The expected benefits from optimized selection in real livestock populations were evaluated by applying dynamic selection algorithms to two livestock populations of sheep (Meatlinc) and beef cattle (Aberdeen Angus). In addition, the effects of introducing BLUP evaluations on the population structure, genetic gain, and inbreeding were investigated. The use of BLUP-EBV accelerated the rates of gain in the Meatlinc, but the effects of BLUP evaluations on Aberdeen Angus are not as evident. Although steady increases in the average coefficient of inbreeding (F) were observed, the inbreeding rates (deltaF) before and after the introduction of BLUP evaluations were not significantly different. The observed deltaF in the last generation was 1.0% for Meatlinc and 0.2% for Aberdeen Angus. The application of the dynamic selection algorithms for maximizing genetic gain at a fixed deltaF led to important expected increases in the rate of genetic gain (deltaG). When deltaF was restricted to the value observed in both populations, increments per year in deltaG of 4.6 (i.e., 17%) index units for Meatlinc and 3.5 (i.e., 30%) index units for Aberdeen Angus were found in comparison to the deltaG expected from conventional truncation BLUP selection. More relaxed constraints on deltaF allowed even higher expected increases in deltaG in both populations. This study demonstrates that the optimization tools constitute a potentially highly effective way of managing gain and inbreeding under a broad range of schemes in terms of scale and inbreeding level. No losses in genetic gain were associated with the use of dynamic optimization selection when schemes were compared at the same deltaF.

Algorithms↗

PubMed1986