The potential of macroalgae for beef production systems in Northern Australia

The extensive grazing systems across northern Australia support approximately 50 % of the national beef herd. Livestock productivity is affected by seasonal variation in pasture quality and quantity. Intensifying livestock production in the north is a challenge, but has been recognised as priority for the Australian economy. Macroalgae offer a sustainable and novel dietary supplement for cattle due to its high nutrient value and biomass production, which are generally superior to forages used in ruminant production systems. This paper highlights some of the existing literature associated with the use of macroalgae for beef cattle and discusses the potential of green freshwater (Cladophora vagabunda, Oedogonium sp., Spirogyra sp.) and marine macroalgae (Cladophora coelothrix, Derbesia tenuissima, Ulva ohnoi) as feed supplements in northern Australian livestock production systems. Crude protein content of the six species of green macroalgae discussed here ranged from 75.4 to 339.1 g kg(-1) dry weight (DW). Dietary mineral limitations in northern livestock production systems include phosphorous (P), sulfur (S) and nitrogen. Four of the six macroalgae species had high P content, ranging from 1.4 to 5 g kg(-1) DW. Sulfur varied between species, ranging from 2.9 to 57.5 g kg(-1) DW, with marine macroalgae having a higher sulfur concentration than freshwater macroalgae. This review demonstrates that green macroalgae have considerable potential to supply a high-protein, high-phosphorous feed supplement for northern livestock production systems dependent on extensive unimproved pastures.