Meta-analysis of lamb birth weight as influenced by pregnancy nutrition of multiparous ewes

Abstract

Across the literature, there is large variation in lamb birth weight responses to changes in the ewe pregnancy nutrition. Much of this heterogeneity has been attributed to several factors inherent to each experiment; however, the relative contribution of these experimental factors has not yet been quantified. This meta-analysis aimed to systematically review the variation in lamb birth weight responses across nutritional studies involving adult multiparous ewes. Effect-sizes for individual studies were estimated using the unbiased estimator Hedges' g, whereby positive and negative values indicate heavier and lighter treatment lambs vs. controls, respectively. Heterogeneity varied between early-, mid- and late-pregnancy undernutrition studies (I2total [early pregnancy] = 19.90%, I2total [midpregnancy] = 52.10%, I2total [late pregnancy] = 68.70%). The small average effects for early- (0.04, highest posterior density [HPD] interval = -0.22, 0.28) and mid-pregnancy undernutrition (-0.15, HPD interval = -0.35, 0.05) suggest that if farmers anticipate a potential feed shortage, ewes can be allowed to lose weight providing nutrition is resumed to adequate levels later in pregnancy. On the contrary, late-pregnancy undernutrition was associated with a significant decrease in lamb birth weight (-0.72, HPD interval = -0.86, -0.55). Thus, management practices should focus on ensuring adequate nutrition in late pregnancy. Increasing lamb birth weight could be possible by feeding ewes above their pregnancy maintenance requirement (0.23, HPD interval = 0.002, 0.48), though the number of studies is limited and further research is needed.

Developing a continuous adjustment factor for dry matter intake of gestating and lactating ewes

“…However, a number of studies have focused on the determination of the requirement of a specific race, considering that there is a nutritional difference between them (Ji et al, 2015;Pereira et al, 2017Pereira et al, , 2016Rodrigues et al, 2016). Certain researchers have worked on the effect of maternal nutritional requirement on progeny; these studies are called fetal programming, and are not usually studied in prediction equations (Campion et al, 2016;Hoffman et al, 2018;McGovern et al, 2015;Peine et al, 2018;Roca Fraga et al, 2018). Further investigation is warranted if the adjustments proposed in equations 5 and 6 would still apply to different levels of the plane of nutrition of gestating ewes.…”

Primer Seminario Técnico de Programación Fetal

“…El plano nutricional de las ovejas durante el segundo tercio de gestación no afectó el PN de los corderos, lo cual coincide con lo reportado por , en donde las ovejas tuvieron el mismo nivel y periodo de restricción energética que las de nuestro experimento. La restricción nutricional de la oveja en etapas tempranas y media de gestación parece no tener efecto significativo en el peso vivo al nacimiento de los corderos que sí lo tiene en el último tercio de gestación (Roca Fraga et al, 2018). En nuestro experimento los corderos machos presentaron un PN mayor que las hembras, sin embargo, no se registraron diferencias en el PD entre ambos sexos lo cual coincide con los resultados reportados por .…”

Changes in Digestive Microbiota, Rumen Fermentations and Oxidative Stress around Parturition Are Alleviated by Live Yeast Feed Supplementation to Gestating Ewes

“…It is known that the nutritional status of gestating dams does impact the weight of the offspring at birth, which is associated with their vigor, autonomy, and further survival capacity [66]. In particular, late-pregnancy undernutrition was associated with a significant decrease in lamb birth weight [67]. The importance of adequate maternal nutrition and the prevention of oxidative stress has been stretched, especially for ewes bearing multiple fetuses [68].…”