An assessment of whether energy was the first factor limiting production of dairy cows grazing kikuyu grass pasture

Abstract

Whole plants of kikuyu grass were taken at intervals over a 9-month period from four commercial dairy farms on which this grass was the predominant species. The plants were separated into leaf and stem fractions and their metabolizable energy (ME) concentrations were estimated from their cell-wall contents. The overall mean ME in the dry matter of leaf and stem on each farm was of the order of 11 and 9 MJ kg DM-1, respectively. From considerations of appetite limits depending upon whether energy was derived mainly from leaf or stem, and taking into account ME supplied from supplementary feeds, and ME requirements for milk production, it was concluded that the production of the herd with the highest mean production cow-1 (4140 kg lactation-1) was limited by dietary energy concentration, although the genetic capacity of the cows to produce milk at the expense of body weight loss overcame this limitation to some extent. On the other farms with low to intermediate levels of productivity, the amount of food on offer was the first limiting factor.