The effect of a zero-grazed perennial ryegrass, perennial ryegrass and white clover, or multispecies forage on the dry matter intake, milk production and nitrogen utilization of dairy cows in mid-late lactation

•Multispecies increased forage intake and milk production of dairy cows.•Urinary N% was 20% lower when cows consumed multispecies.•Cows offered clover forages had a higher N intake and lower N use efficiency.•Perennial ryegrass resulted in the highest milk and N use efficiency. The objective of this experiment was to assess the impact of forage type on the DMI and milk production of mid-late lactation dairy cows. Perennial ryegrass (Lolium perenne) (PRG), PRG and white clover (Trilfolium repens) (PRGWC) and multispecies forage containing PRG, timothy (Phleum pratense), WC, red clover (Trifolium pratense), chicory (Cichorium intybus), and plantain (Plantago lanceolata) (MULTI), were compared using 24 cows in a three-period Latin square changeover design experiment. Cows were acclimatized to dietary treatments for 14 days, before entering a 21-day sampling period. Animals were housed indoors throughout the experiment, with access to forage treatments via computerized feeding boxes that recorded daily forage fresh weight intake and feeding behavior. Forage was harvested using a zero-grazer and feed boxes filled throughout the day. Forage dry matter was determined daily and forage DMI subsequently calculated. Milk yield (MY) was recorded daily, with milk composition (fat, protein, lactose) measured weekly. Once per sampling period, blood and rumen samples were collected. The partitioning of dietary nitrogen into milk, feces and urine was assessed for 6-days in each sampling period. Data was analyzed in SAS using PROC MIXED and checked for normality using UNIVARIATE. Forage botanical composition changed from period 1 to period 2 and 3, leading to significant differences in chemical composition between periods. Despite this, dry matter intake was consistently higher (P