Methods to associate animals between periods (grouping of records within a calving season into a 60-day interval starting from the date of the first calf born for 400-day weight analysis) within the contemporary group classification on sexmanagement group-date of weighing, using an animal model were compared. The data were derived from ten Angus herds. Assigning animals to more than one period and/or treating period as random or introducing days from start of calving period as a co-variate (linear and quadratic) did little to improve herd mean square error compared to the basic model where there were no associations between periods. The reduction in the standard errors of predictions were significant (p < 0.05) only when period within sex-management group-date of weighing was treated as random. However, the use of a similarity matrix S (which associates periods within the fixed contemporary group classification) in the mixed model equations reduced mean square error by as much as 7%. Using simulated observations for the ten herds, highest correlations between true breeding values and estimated breeding values were obtained only for the model using the similarity matrix. ZUSAMMENFASSUNG: Vergleich alternativer Methoden der Behandlung von Wirkungen kontemporärer Gruppen bei Tiermodellvoraussagen Methoden zur Verbindung zwischen Tieren verschiedener Perioden (Leistungsabschlüsse in 60-Tage-Intervallen einer Abkalbesaison für 400 Tagegewichte ab dem ersten geborenen Kalb) innerhalb kontemporärer Gruppenklassifikation und Geschlechts-Managementgruppen bei Tiermodellen wurden verglichen. Die Daten stammten von 10 Angusherden. Zuordnung von Tieren an mehr als eine Periode als zufällig oder Einbeziehung von Tagen von Beginn der Abkalbeperiode als Kovariable (linear und quadratisch) half wenig zur Verbesserung des Herdenfehlermittelquadrates im Vergleich zu dem Grundmodell, wo keine Verbindungen zwischen Perioden unterstellt wurden. Die Verminderung des Standardfehlers der Voraussage war signifikant (p < als 0,05) nur wenn Perioden innerhalb Geschlechts-Managementgruppen als zufällig betrachtet worden sind. Allerdings hat die Verwendung der Ähnlichkeitsmatrix S (welche Perioden innerhalb einer fixen kontemporären Gruppenklassifikation assoziiert) in der gemischten Modellgleichungen den Mittelquadratfehler um bis zu 7% reduziert. Unter Verwendung simulierter Beobachtungen für 10 Herden haben sich die höchsten Korrelationen zwischen wahren Zuchtwerten und geschätzten nur bei dem Modell ergeben, das die Ähnlichkeitsmatrix verwendet hat.
Background
Maternal hypertriglyceridaemia is associated with an increase in the risk of pre-eclampsia. We evaluated the role of diet and lipid lowering interventions in pregnancy in preventing pre-eclampsia by a systematic review of evidence.
Methods
The major electronic databases were searched (until November 2011) to find relevant citations for interventions. No search restrictions were applied. Interventions included diet control and fibre supplements, physical activity, statins and omega-3 fatty acids. Systematic review of effectiveness was carried out using methodology in line with current recommendations. Results were summarised as pooled relative risks (RR) with 95% confidence intervals (CI) for dichotomous data.
Results
19903 citations were identified. Of these 12 studied the effect of diet, 20 the effect of physical activity and 6 of omega-3 fatty acids on the incidence of pre-eclampsia. Weight management interventions including diet, physical activity and mixed approach (10 RCTs, 3072 women) overall, in pregnancy resulted in a significant reduction in the incidence of pre-eclampsia (RR 0.74, 95% CI 0.59, 0.92; p=0.008). Diet in pregnancy (6 RCTs, 2624 women) resulted in a significant decrease in the risk of pre-eclampsia (RR 0.67, 95% CI 0.53, 0.85; p=0.0009) compared to physical activity and mixed approach. The effect of other lipid lowering interventions like statins, fibre and omega-3 will be provided in detail if selected.
Conclusions
Dietary interventions in pregnancy to manage weight resulted in significant reduction in the risk of pre-eclampsia compared to other interventions.
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