Abstract

An indoor feeding experiment using 16 late lactation Friesian dairy cows measured effects of increased proportions of birdsfoot trefoil (Lotus corniculatus; Lotus) in the diet on the partitioning of nitrogen (N) between milk, faeces and urine. Cows were housed in metabolism stalls for 12 days and fed diets containing 0%, 15%, 29% or 45% Lotus (% Lotus dry matter (DM) per DM intake (DMI)) with the remainder perennial ryegrass pasture. Increasing the proportion of Lotus in the diet did not affect DMI but increased milk (P <0.001) and milksolids yields (P <0.01). The percentage of N intake partitioned to milk increased from 16% (0% Lotus) to 21% (45% Lotus) (P <0.01) with an increasing proportion of Lotus in the diet. The percentage of N intake excreted as faecal N also increased from 29% (0% Lotus) to 38% (45% Lotus) (P <0.001) while the percentage excreted as urinary N was reduced from 49% (0% Lotus) to 34% (45% Lotus) (P <0.01). Partitioning of N towards faeces has a favourable environmental impact since faecal N is largely retained in soils whereas urinary N is subject to volatilisation as ammonia, losses as nitrous oxides (a greenhouse gas) and leaching into groundwater.

SL, Woodward, GC Waghorn, KA Watkins, and MA Bryant

Proceedings of the New Zealand Society of Animal Production, Volume 69, Christchurch, 179-183, 2009