Feed efficiency and performance of cattle grazing tropical grasslands: a meta-analysis

Abstract

Pastures are the main environmentally satisfactory way to increase beef production, especially in tropical areas. To assess the potential of tropical pastures, a meta-analysis of published data with reliable estimates of body weight gain, feed intake and digestibility was performed. In intra-experiment analysis, the available biomass per hectare is positively related to the sward height and to live weight gain. The stocking rate is a major management leverage, which decreases individual live weight gain, but increases it when expressed per hectare. The trials of concentrate intake reveal a positive effect on body weight gain with an average substitution rate of 0.76 with feed intake. Thus at pasture, digestible dry matter intake is the primary factor determining the live weight gain, according to a positive curvilinear relationship, and depends more on the dry matter intake than on its digestibility. Metabolizable energy intake and maintenance requirements were estimated at 5.44 kcal per kg of live weight gain and 180 kcal per kg metabolic weight. Changes in feed efficiency and its components, the digestive and metabolic efficiency have also been calculated. It appears that digestive efficiency is higher than metabolic efficiency, and feed efficiency is more related to metabolic efficiency, the latter two being very positively correlated to body weight gain. The equations established by this meta-analysis could be used for the future construction and evaluation of a mechanistic model of intake and growth of cattle in tropical pastures.