RESUMO
Animals born by embryo transfer (ET) are usually not included in the genetic evaluation of beef cattle for preweaning growth if the recipient dam is unknown. This is primarily to avoid potential bias in the estimation of the unknown age of dam. We present a method that allows including records of calves with unknown age of dam. Assumptions are as follows: (i) foster cows belong to the same breed being evaluated, (ii) there is no correlation between the breeding value (BV) of the calf and the maternal BV of the recipient cow, and (iii) cows of all ages are used as recipients. We examine the issue of bias for the fixed level of unknown age of dam (AOD) and propose an estimator of the effect based on classical measurement error theory (MEM) and a Bayesian approach. Using stochastic simulation under random mating or selection, the MEM estimating equations were compared with BLUP in two situations as follows: (i) full information (FI); (ii) missing AOD information on some dams. Predictions of breeding value (PBV) from the FI situation had the smallest empirical average bias followed by PBV obtained without taking measurement error into account. In turn, MEM displayed the highest bias, although the differences were small. On the other hand, MEM showed the smallest MSEP, for either random mating or selection, followed by FI, whereas ignoring measurement error produced the largest MSEP. As a consequence from the smallest MSEP with a relatively small bias, empirical accuracies of PBV were larger for MEM than those for full information, which in turn showed larger accuracies than the situation ignoring measurement error. It is concluded that MEM equations are a useful alternative for analysing weaning weight data when recipient cows are unknown, as it mitigates the effects of bias in AOD by decreasing MSEP.
Assuntos
Bovinos/genética , Transferência Embrionária/veterinária , Algoritmos , Animais , Bovinos/crescimento & desenvolvimento , Interpretação Estatística de Dados , Feminino , Estudos de Associação Genética , LinhagemRESUMO
The Bayesian approach was implemented for fitting several maternally ancestral models for weaning weight data of Angus calves. The goal was to evaluate to what extent genetic evaluation models with additive grand maternal effects (G), or with an ancestrally structured covariance matrix for maternal environmental effects (E), or with a sire × year interaction (ISY), or combinations thereof (GE, GSY, ESY, GESY), redistribute the additive variability and reduce the negative magnitude of the additive correlation between direct and maternal effects (r(AoAm)), when compared with the regular maternal animal model (I). All animals with records had known dams and maternal granddams. The sampling scheme induced low autocorrelations among all variables and tended to converge quickly. The signs of the estimates of r(AoAm) were consistently negative for all models fitted. The magnitudes of the estimates of r(AoAm) from models E, G, GE, ESY, and GESY were almost one-third of those from models I and ISY. Inclusion of the sire × year interaction had some effect in reducing the negative magnitude of r(AoAm), but also reduced the size of the estimates of direct (h(0)(2)) and maternal (h(m)(2)) heritabilities. In comparison, models E or G reduced the negative magnitude of r(AoAm) by 0.50 units and produced more favorable estimates of H(0)(2) and h(m)(2) than models I and ISY. The estimate of h(0)(2) from G was similar to the one from I; however, the estimated h(m)(2) was 0.04 units greater, whereas the estimate of r(AoAm) was much less negative (-0.21 vs. -0.71) than the respective estimates from I. The environmental correlation between the weaning weights of dams and their daughters (λ) was estimated to be -0.28 ± 0.03 in E and ESY, and -0.21 ± 0.03 in GE and GESY. Inclusion of the sire × year interaction effect by itself did not have much of an impact in the reduction of the estimated magnitude of r(AoAm). Rank correlations among EBV for direct effects were larger than 0.94 and did not show any appreciable difference among models, whereas the rank correlation among maternal breeding values displayed differences in the ranking between I and the other models. Models E and ESY recovered the largest amount of total additive variability with maternal effects.
Assuntos
Teorema de Bayes , Peso Corporal/genética , Peso Corporal/fisiologia , Desmame , Animais , Cruzamento , Bovinos , Feminino , Masculino , Modelos Biológicos , FenótipoRESUMO
Although breastfeeding is an optimal source of nutrition that promotes the health and development of infants, rates of breastfeeding have been declining. International conventions and strategies, such as the Innocenti Declaration and the 10 Steps to Successful Breastfeeding, are helping to educate society about the benefits of breastfeeding and to create supports for mothers and their children, but advocacy and education are still needed
Assuntos
Aleitamento Materno , Saúde Global , Promoção da Saúde/organização & administração , Feminino , Direitos Humanos , Humanos , Lactente , Recém-Nascido , Masculino , Apoio Social , Valores SociaisRESUMO
3-Nitropropionic acid (3-NPA) was identified as the toxic component of several plants and fungi. Recently, it was described that 3-NPA produced hypotension, accompanied by a paradoxical bradycardia. In this study, we identified a possible mechanism of action, explaining the effect of 3-NPA on cardiac tissue. We used isolated, spontaneously beating atria and heart mitochondria to measure electrophysiological properties and mitochondrial oxygen consumption. We also measured Na+/K+ ATPase activity and intracellular ATP levels. In isolated spontaneously beating atria, 3-NPA (10(-4) M) decreased heart rate by 62 +/- 3%. This agent did not affect the amplitude or duration of action potentials. The duration of intervals between two action potentials, however, was prolonged from 530 +/- 285 to 1400 +/- 600 ms after 3-NPA exposure (10(-2) M). Oxygen consumption by heart mitochondria was inhibited by 3-NPA when either malate/glutamate or succinate were used as metabolism substrates. Cytochrome C oxidase activity was not affected by 3-NPA. Finally, atrial ATP content decreased 65 +/- 3% after 3-NPA treatment. In conclusion, we show that 3-NPA decreases atrial rate by increasing the action potential phase 4, probably by inhibition of mitochondrial respiration, thereby decreasing cardiac ATP content. This suggests that 3-NPA-induced bradycardia may be related to intracellular ATP depletion.