Meta-analyses comparing the nutritional composition of perennial ryegrass (Lolium perenne) and plantain (Plantago lanceolata) pastures
Studies comparing livestock responses to diets containing plantain with traditional ryegrass/clover diets suggest differences in the nutritional composition between the species might explain some of the variation in results. To explore this theory, a meta-analysis was performed to compare the nutritional composition of plantain and perennial ryegrass pastures, and define key differences between the species. Standardised effect sizes (plantain vs ryegrass pastures), expressed as correlation coefficients (r) with values from -1 to +1, and treatment means from 34 studies were determined using a weighted random effects model. Pastures containing plantain had lesser herbage dry matter content than ryegrass pastures across all seasons (mean 13.4 vs. 19.4%, P<0.001; r<-0.65). Structural fibre content was consistently smaller (mean 32.1 vs. 43.4% DM), but non-structural fibre content larger in plantain compared with ryegrass pastures (large effect sizes of r>0.70). There was no difference in total herbage nitrogen concentration (g/100 g DM; r<0.03). However, plantain pastures contained less soluble and degradable nitrogen compared with ryegrass pastures (r<-0.78). Herbage digestibility did not differ significantly between pastures (r=-0.13; P=0.168). Generally, the effect of plantain on nutritional composition was consistent across seasons. Experiments and models investigating the effects of pasture mixes on environmental nitrogen losses ought to include detailed nitrogen and carbohydrate fractions data for accurate interpretation and prediction.
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