Comparison of the nutritive value of a turkey native forage, tumbleweed hay (Gundelia tournefortii L.), wheat straw and alfalfa hay using in situ and in vitro measurements with sheep

Hay from native-growing tumbleweed (Gundelia tournefortii L.) was compared with wheat (Triticum estivum) straw and alfalfa (Medicago sativa) hay in terms of chemical composition, in situ dry matter (DM) degradation in vitro gas production and in vitro DM digestibility (IVDMD). Chemical composition of tumbleweed hay was better than wheat straw but comparable to alfalfa hay. Crude protein (CP) concentration of tumbleweed hay was higher (P<0.001) than that of wheat straw but lower than that of alfalfa hay. Crude fibre (CF) concentration of tumbleweed hay was lower (P<0.001) than that of wheat straw but similar to that of alfalfa hay. Mineral concentrations varied among forages. Tumbleweed hay was high in phosphorus (P) and iron (Fe) compared with alfalfa hay and wheat straw. The in situ DM disappearance and corresponding estimated prediction equation parameters of tumbleweed hay were higher (P<0.001) than those of wheat straw but similar to those of alfalfa hay, whereas in vitro gas production at all incubation times and corresponding estimated parameters of tumbleweed hay were higher (P<0.001) than those of alfalfa hay and wheat straw. Metabolizable energy (ME) values of the forages varied between 7.1 and 10.5 MJ/kg DM. The ME value of tumbleweed hay exceeded (P<0.001) those of alfalfa hay and wheat straw. In vitro DM digestibility (IVDMD) of tumbleweed hay was higher (P<0.001) than that wheat straw but similar to that of alfalfa. It was concluded that the nutritive value of tumbleweed hay is better than that of wheat straw and comparable to that of alfalfa hay. Within the confines of this study, tumbleweed hay seems to have potential as a forage crop for smallholder farmers during periods of forage scarcity. (English