Liquid supplementation for ruminants fed low-quality forage diets: a review

Abstract

Forty-three studies involving liquid supplementation of cattle and sheep consuming low-quality forages were identified, summarized in tabular form and reviewed. All studies that could be found containing animal gain, forage intake and (or) supplement consumption with molasses-urea supplements under grazing conditions were reviewed. Seven studies were found which compared forage intake or animal performance by animals fed hay or straw and molasses-urea supplements with unsupplemented animals. Molasses-urea supplements did not increase forage intake or animal performance compared with unsupplemented animals in five of the seven studies. Thirteen studies were identified which evaluated performance of grazing animals receiving molasses-urea supplements compared with unsupplemented animals. Seven of these 13 grazing studies reported improved live weight change when animals received molasses-urea supplements. Only two grazing studies were found which evaluated forage intake by animals consuming molasses-urea supplements and compared it with unsupplemented animals. Both studies found no effect. Five of six studies identified that compared molasses-urea supplements with dry supplements, forage intake or animal live weight change were not increased by molasses-urea supplements over dry supplements. Most authors concluded that feeding molasses-urea supplements to grazing ruminants was not as profitable as feeding dry supplements; however, few studies reported economic data. Studies demonstrated that level of molasses and nitrogen influenced animal performance. Asynchrony between molasses and nitrogen resulted in animal weight loss. Most positive animal responses were seen with a combination of high levels of molasses and nitrogen. However, these results may have been influenced by supplement formulation. Performance and intake results were confounded by pasture condition, forage quality, animal variation and supplement delivery system. In four studies that measured supplement intake by individual animals, between 1 and 20% of experimental animals refused to consume any molasses-urea supplement. Quantification of supplement intake and animal feeding behavior has not been adequately addressed in the literature.