Use of Italian ryegrass on seasonal dairy farms in northern New Zealand

Abstract

Milk production from cows grazing existing perennial ryegrass pastures or those direct‐drilled with Italian ryegrass (Lolium multiflorum Lam. cv. Concord) or with new perennial ryegrasses (Lolium perenne L.) was measured over the 1991/ 92 and 1992/93 lactations (July‐April), on intensively managed farmlets. This trial complemented large‐plot grazing experiments, and incorporated similar renovation methods of direct‐drilling (undersowing) and herbicide application before direct‐drilling of grass seed. Twenty Friesian cows rotationally grazed each of the three treatment farmlets; they were milked from July/August until April/May. Average herbage accumulation in late winter/early spring on the Concord farmlet was only slightly greater (+100 kg DM/ha), but in summer/autumn was inferior (‐350 kg DM/ha) to herbage accumulation on the unrenovated perennial ryegrass‐based farmlet (Control). In winter/spring (July‐December) 1991 and 1992, cows on the Concord farmlet produced similar milk yields (about 2800 kg/cow) as those grazing existing perennial ryegrass pastures and existing pastures direct‐drilled with new perennial ryegrasses. Similarly, there were no differences in fat, protein, or lactose yields at 129, 98, and 135 kg/cow, respectively. However, in summer/autumn 1991 (January‐April), cows on the Concord farmlet produced less milk (782 vs 1059 kg/cow), fat (37 vs 54 kg/cow), protein (27 vs 38 kg/cow), and lactose (37 vs 50 kg/cow) than those grazing the Control farmlet; there were no treatment differences during summer/autumn 1992. It was concluded that Concord ryegrass was unable to provide sufficient increases in feed to improve seasonal or total milk production from cows on intensively grazed farms.