The Agricultural Research Council (1980, 1984) protein recommendation for dairy cows was designed to ensure that total amino acid nitrogen (TAA-N) entering the duodenum is sufficient to provide TAA-N for production. Essential amino acid (EAA) supply and demand, although recognised as important, was not an integral part of the scheme.
These trials were designed to test the feasibility and efficacy of formulating compound feeds to complement and improve the duodenal EAA supply from the basal diet of lactating cows.
The experimental aim was to formulate compound feeds on the basis of undegradable EAA (UEAA), to compare the performance of dairy cows fed these rations and to relate performance to measurements of nutrient supply to the duodenum. The trials took the form of two production trials (years 1 and 2) and one digestibility trial (year 2). Estimates of the supply of EAA to the duodenum were obtained by in vivo measurements in cannulated cows (year 2).