The effect of perennial ryegrass ploidy and white clover inclusion on milk production of dairy cows.

Grazed grass is considered the cheapest feed available for dairy cows in temperate regions, and to maximise profits, dairy farmers must utilise this high-quality feed where possible. Recent research has reported that including white clover (Trifolium repens L.) in grass swards can have a positive effect on milk production. The aim of the present study was to quantify the effect of tetraploid and diploid perennial ryegrass (Lolium perenne L.; PRG) swards sown with and without white clover on the milk production of grazing dairy cows. Four grazing treatments were used for the study; tetraploid-only PRG swards, diploid-only PRG swards, tetraploid PRG with white clover swards and diploid PRG with white clover swards. Thirty cows were assigned to each treatment and swards were rotationally grazed at a stocking rate of 2.75 cows/ha and a nitrogen-fertiliser application rate of 250 kg/ha annually. There was no significant effect of ploidy on milk production. Over the present 4-year study, cows grazing the PRG–white clover treatments had greater milk yields (+597 kg/cow.year) and milk-solid yield (+48 kg/cow.year) than cows grazing the PRG-only treatments. This significant increase in milk production suggests that the inclusion of white clover in grazing systems can be effectively used to increase milk production of grazing dairy cows. Recent research has reported that perennial ryegrass (PRG) ploidy and white clover inclusion in grazing swards can have a positive effect on milk production. In the present study, cows grazing PRG–white clover swards had greater milk yields than did cows grazing PRG-only swards, while grass ploidy had no effect. This significant increase in milk production from PRG–white clover swards suggests that the inclusion of white clover in grazing systems can be effectively used to increase milk production. [ABSTRACT FROM AUTHOR]