Meta-analysis of the impact of white clover inclusion on milk production of grazing dairy cows

There is recent interest in the introduction of white clover (WC) in Ireland to improve the efficiency of pasture-based grazing systems. After a literature review, a meta-analysis was undertaken to investigate the effect of WC inclusion in perennial ryegrass swards on milk production. For analytical purposes two databases were created, containing 15 and 20 papers, respectively, published between 1985 and 2015. Database one, contained experiments comparing milk production from cows that grazed on grass-only (GO) and grass-clover (GC) swards. Database two contained only experiments that had GC swards to investigate the impact of varying sward WC content on milk production. In database one, the mean WC content of the GC swards was 33.6%. Mean daily milk yield was greater (P<0.001) for cows that grazed on GC swards compared with GO swards (18.8 kg vs 17.6 kg, respectively). However, stocking rate and milk yield per hectare were reduced (P