Wilted tagasaste ( Chamaecytisus palmensis) forage as a replacement for a concentrate supplement for lactating crossbred Friesian × Zebu (Boran) dairy cows fed low-quality native hay

Abstract

An experiment was conducted with four rumen-cannulated crossbred cows in a balanced 4 × 4 Latin square to study the effect of wilted tagasaste ( Chamaecytisus palmensis) forage on rumen parameters and milk yield. The cows were fed a basal diet consisting of ad libitum native hay, mineral lick and water. Tagasaste forage was used to replace, on a dry matter (DM) weight-for-weight basis, 0, 33, 66 and 100% of 4.5 kg of an air-dry concentrate mix based on noug ( Guizotia abyssinica) cake and wheat middlings that was used to supplement the basal diet. The rumen degradation of nitrogen tagasaste forage was intermediate between that of hay and wilted sesbania ( Sesbania sesban) forage. Contents of tannic compounds were low—lower in tagasaste than in sesbania forage. The cows were healthy throughout the 84 day experiment. However, they refused to eat all the tagasaste forage at the higher levels of replacement (66 and 100%), resulting in significantly ( P < 0.001) lower total DM and crude protein intakes. It was concluded that poor palatability might be the main reason for low intake of tagasaste. Decline in nutrient intakes resulted in a simultaneous linear decrease ( P < 0.01 − 0.05) in milk yield and milk protein content. Replacing concentrate with tagasaste did not have a significant effect on the apparent total tract digestion of dietary DM of organic matter, but it decreased the crude protein digestion ( P < 0.05) and increased ( P < 0.01) cell wall digestion linearly. It also had clear and statistically significant ( P < 0.01 − 0.05) linear effects on rumen fluid parameters. pH and acetic acid increased, while propionic and butyric acids and ammonia decreased, in the rumen fluid. Metabolizable energy supply, calculated from the intake of digestible organic matter, was sufficient on all the diets to maintain the milk production level recorded with 0 or 33% replacement (average 5.2 kg day −1), but the supply of crude protein was insufficient to support this production level when 56 or 100% of the concentrate was replaced by tagasaste. It was concluded that tagasaste forage could not be used to replace concentrate as a supplementary feed for crossbred dairy cows without decreasing feed intake and milk yield. It was, however, also concluded that tagasaste should be evaluated in an environment where practical alternatives for energy or protein supplements are scarce or non-existent.