The Inclusion of Ribwort Plantain (Plantago lanceolata L) Into Perennial Ryegrass (Lolium perenne L) Swards Managed Under Intensive Dairy Cow Grazing: The Impacts on Milk Yield, Milk Quality, Milk Fatty Acids, Milk Nitrogen Use Efficiency and Grazing Behaviour

Abstract

Ribwort plantain is gaining attention as a potential forage species to enhance sustainability in temperate pasture-based dairy systems. This study investigated the effects of moderate plantain inclusion in perennial ryegrass swards on dairy cow milk yield and composition, milk fatty acid profile and nitrogen use efficiency under intensive grazing management in Northern Ireland. Over two grazing seasons, 60 and 44 high-performing Holstein-Friesian cows were allocated to perennial ryegrass (PRG) swards or mixed perennial ryegrass–plantain swards (PRG-PL), respectively in year 1 and 2. Sward composition remained consistent across both years, with PRG-PL swards averaging 30% plantain. Results indicated that inclusion of plantain had no significant impact on milk yield, body condition score, milk nitrogen use efficiency or animal grazing behaviour (p > 0.05). However, mixed perennial ryegrass–plantain swards exhibited improved herbage utilisation (78.9% and 83.1% respectively, for PRG and PRG-PL swards). PRG-PL swards had a higher mineral ash (p < 0.001) and ADF (p < 0.01) content, but a lower NDF (p < 0.001), WSC (p < 0.05), GE (p < 0.001), DOMD (p < 0.001) and DM (p < 0.001) compared to PRG swards. Notably, inclusion of plantain significantly altered the milk fatty acid profile, increasing concentrations of beneficial polyunsaturated fatty acids, including omega-3 (n-3) (p < 0.05) and omega-6 (n-6) (p < 0.001) fatty acids, while decreasing conjugated linoleic acids (p < 0.01). These changes may offer potential nutritional advantages in dairy products. Although persistency of plantain remains a challenge in Northern Hemisphere climates, moderate inclusion in mixed swards proved agronomically viable and did not compromise cow productivity. This study provides evidence that incorporating plantain into PRG swards can enhance certain milk quality traits without negatively impacting milk yield or milk nitrogen use efficiency.