Genetic Correlations Between Body Weight of Cocks and Production Traits in Laying Hens, and Their Possible Use in Breeding Schemes

Genetic and phenotypic (co)variances between body weight of cocks (nm = 1,138), BWM, and production traits of hens (nf = 8,844), i.e., egg number (EN), egg weight (EW), feed intake (FI), and body weight (BWF) were estimated by the restricted maximum likelihood method for an animal model. Six multivariate analyses were carried out to get all desired components. Resulting heritabilities were .292, .754, .682, .732, and .790 for EN, EW, FI, BWF, and BWM, respectively. Estimated genetic correlations between BWM and EN, EW, FI, and BWF, were −.161, .338, .645, and .841, respectively. The corresponding estimates between BWF and EN, EW, and FI, were −.036, .294, and .787, respectively. The additional expected selection response in traits of hens from including BWM into the selection criterion of cocks is given for a particular structure with full- and half-sister information and different correlations between BWM and traits of hen

Phenotypic and Genetic Effects on Feed Intake of Laying Hens in Different Years

Feed intake from 21 to 40 wk and from 41 to 60 wk of age of brown egg layers was analyzed. The full model contained BW, egg mass (EM) output, BW change (BWCH), and age at first egg as covariates in addition to effects of plumage condition class, sire, and dam. A reduced model contained the covariates only. Between 905 and 1,161, and 880 and 1,119 hens were available in the first and second periods, respectively. Averaged over 6 yr the full model explained 84 and 77%, the reduced model 73 and 63%, respectively, of the variance in feed consumption in the two periods. Regression coefficients for BW showed only a small variation between years as well as between periods. Variation was larger for the coefficients of EM and of BWCH. Larger coefficients were observed in the first period for both traits. The sequence of entering the reduced equation in a stepwise procedure was always BW, EM output, then BWCH. Averaged over 6 yr, the relative contribution of BW by its own to the accuracy of the regression model, was 68 and 60% in the two periods. Egg mass output then added 25 and 39%, and BWCH 7 and 2% in the first and second periods, respectively. The predictive value of the covariates changed with increasing age of the hens. A high average heritability of .48 could be estimated for the residual feed intake in both periods. This suggested enhanced selection response for efficienc

Relationships Between Income Minus Feed Cost and Residual Feed Consumption in Laying Hens

Residual feed consumption in laying hens is defined as the difference between observed feed intake and intake estimated from body weight, egg mass produced, and body weight change. Genetic and phenotypic relationships between residual feed consumption in the period of 21 to 40 wk of age (RFC) and income minus feed cost (IFC), egg mass (EM), egg number (EN), egg weight (EW), female body weight (BWF), feed efficiency (FE), age at first egg (AFE), and male body weight (BWM) were investigated on data of 8,844 hens and 1,138 cocks of brown egg layers, offspring of 427 sires and 1,945 dams. Restricted maximum likelihood estimates of the genetic correlations for an animal model among RFC and IFC, EM, EN, EW, BWF, FE, AFE, and BWM were .011, .306, .267, .085, .100, -.317, -.202, and .025, respectively. Heritabilities of .69 and .65 and a genetic correlation of .903 were found for observed feed consumption and estimated feed consumption, respectively. Residual feed consumption was found to be of only limited value as an additional selection trait to improve overall profitability of egg production, defined as income minus feed cost in a specified period of tim

What can be gained by the BLUP procedure under various circumstances?

International audienc

An Integrated Model of Condom Use in Sub-Saharan African Youth: A Meta-Analysis

Objective: We tested an integrated social- cognitive model derived from multiple theories of the determinants of young peoples' condom use in Sub-Saharan Africa. The model comprised seven social- cognitive antecedents of condom use: Attitudes, norms, control, risk perceptions, barriers, intentions, and previous condom use. Method: We conducted a systematic search of studies including effects between at least one model construct and intended or actual condom use in young people from sub-Saharan African countries. Fifty-five studies comprising 72 independent data sets were included and subjected to random-effects meta-analysis. Demographic and methodological variables were coded as moderators. Hypotheses of the integrated model were tested using meta-analytic structural equation modeling. Results: The meta-analysis revealed significant nontrivial sample-weighted correlations among most model constructs. Moderator analyses revealed differences in six correlations for studies that included a formative research component relative to studies that did not. There was little evidence of systematic moderation of relations among model constructs by other candidate moderators. Meta-analytic structural equation models revealed significant direct effects of attitudes, norms, and control on condom use intentions, and of intention, control, and barriers on condom use. Including past condom use increased explained variance in condom use intentions and behavior but did not attenuate model effects. There were also significant indirect effects of attitudes, norms, and control on condom use through intentions. Conclusions: Findings provide preliminary evidence to support the integrated condom use model in sub-Saharan African youth. The model provides guidance on potential targets for improving the effectiveness of condom promotion interventions

On the estimation of genetic parameters via variance components

International audienc

Autonomous and controlled motivational regulations for multiple health related behaviors: between- and within-participants analyses

Self-determination theory has been applied to the prediction of a number of health-related behaviors with self-determined or autonomous forms of motivation generally more effective in predicting health behavior than non-self-determined or controlled forms. Research has been confined to examining the motivational predictors in single health behaviors rather than comparing effects across multiple behaviors. The present study addressed this gap in the literature by testing the relative contribution of autonomous and controlling motivation to the prediction of a large number of health-related behaviors, and examining individual differences in self-determined motivation as a moderator of the effects of autonomous and controlling motivation on health behavior. Participants were undergraduate students (N = 140) who completed measures of autonomous and controlled motivational regulations and behavioral intention for 20 health-related behaviors at an initial occasion with follow-up behavioral measures taken four weeks later. Path analysis was used to test a process model for each behavior in which motivational regulations predicted behavior mediated by intentions. Some minor idiosyncratic findings aside, between-participants analyses revealed significant effects for autonomous motivational regulations on intentions and behavior across the 20 behaviors. Effects for controlled motivation on intentions and behavior were relatively modest by comparison. Intentions mediated the effect of autonomous motivation on behavior. Within-participants analyses were used to segregate the sample into individuals who based their intentions on autonomous motivation (autonomy-oriented) and controlled motivation (control-oriented). Replicating the between-participants path analyses for the process model in the autonomy- and control-oriented samples did not alter the relative effects of the motivational orientations on intention and behavior. Results provide evidence for consistent effects of autonomous motivation on intentions and behavior across multiple health-related behaviors with little evidence of moderation by individual differences. Findings have implications for the generalizability of proposed effects in self-determination theory and intentions as a mediator of distal motivational factors on health-related behavior

Transferring motivation from educational to extramural contexts: A review of the trans-contextual model

A key question for educators is whether teaching styles, methods, and practices not only foster motivation toward, and persistence with, learning activities in the classroom but also in contexts outside of school (Ciani et al. 2010). There is a wealth of evidence in the social psychological literature applied to educational contexts that has indicated that teaching styles and other motivational strategies adopted by social agents like teachers and educators lead to adaptive outcomes within the school context. For example, adopting democratic teaching styles (Tomasetto 2004), fostering mastery oriented motivational climates (Barkoukis et al. 2008), and providing autonomy support (Reeve 2002) are strategies that have been utilised by social agents in educational contexts to promote increased motivation among pupils and students. Overall, the support offered by teachers in the classroom has been shown to have direct effects on pupils’ emotional and motivational responses (e.g. Covington and Dray 2002). Furthermore, the adoption of autonomy-supportive strategies has been associated with numerous adaptive outcomes such as academic achievement (Deci et al. 1991), perceived competence (Harter 1985), deep learning of concepts (Lau et al.2008), and selection of tasks of optimal challenge (Murphy and Thomas 2008). There is also some evidence that such strategies also foster desirable outcomes beyond the classroom, such as engagement in extra-curricular activities (Tomasetto 2004) and studying behaviour (Kolic-Vehovec et al. 2008). This indicates that social agents’ behaviours in educational settings may motivate students to engage in behaviours and activities outside of school that are adaptive in terms of learning and skill development. Such influences likely fulfil a key goal of education to influence educational activities beyond the classroom.In addition, motivating students outside of the classroom will meet educational aims to promote increased transformative experiences (Pugh et al. 2010) and inquisitive behaviours (Yoon 2009) among pupils that assist in the development of flexible, critical, and analytic thinking skills that are generalizable and transferable. It must, however, be stressed that little is known of the processes by which teacher behaviours in educational contexts impact on students motivation and behaviour within the school and, most importantly, outside school. The aim of the present review is to provide an overview of a recently developed motivational model that outlines the processes by which perceptions of social agents’ behaviours that support motivation and learning affect motivation to engage in educational activities in both the classroom and extramural contexts. The model is based on the integration of leading social psychological and motivational theories and not only identifies the important factors and processes involved in trans-contextual motivation, but also provides an impetus for the development of interventions to promote motivation for learning activities in both educational and extramural contexts. After outlining the conceptual and theoretical bases of the model, we review a series of prospective and intervention studies from our laboratory that provides evidence to support its core trans-contextual premises. We also outline how the model serves as a novel basis for educational interventions to enhance motivation among pupils in educational and extramural contexts and the potential of the model to be applied to interventions in diverse educational contexts to promote general educational aims of fostering adaptive outcomes in students outside the classroom

The trans-contextual model: Perceived learning and performance motivational climates as analogues of perceived autonomy support

The trans-contextual model of motivation (TCM) proposes that perceived autonomy support in physical education (PE) predicts autonomous motivation within this context, which, in turn, is related to autonomous motivation and physical activity in leisure-time. According to achievement goal theory perceptions of learning and performance, motivational climate in PE can also affect autonomous motivation in PE. The purpose of the present study was to examine the influence of an integrated approach of perceptions of motivational climate in PE by incorporating aspects of perceptions of motivational climate from achievement goal frameworks on autonomous motivation in PE within the TCM. High school students (N = 274) completed self-report measures of perceived autonomy support, perceived learning, and performance motivational climate and autonomous motivation in PE. Follow-up measures of autonomous motivation in a leisure-time context were taken along with measures of attitudes, subjective norms, perceived behavioural control and intentions from the theory of planned behaviour 1 week later. Self-reported physical activity behaviour was measured 5 weeks later. The results of the path analyses indicated that perceived learning climate was the strongest predictor of autonomous motivation in PE and leisure-time contexts and mediated the effect of perceived autonomy support on autonomous motivation in PE. Perceived performance climate showed no significant effect on autonomous motivation in PE and leisure-time. Results also confirmed the premises of TCM regarding the effect of autonomous motivation in leisure-time on leisure-time physical activity and the mediating role of the planned behaviour theory variables