Supplementation of cattle browsing tagasaste (Chamaecytisus proliferus) during autumn improves liveweight gain

A study was conducted to determine the response of year ling steers browsing tagasaste in the autumn of 1998 to being fed a daily supplement of either 2 kg lupin grain, 1 kg lupins + 4.5 kg silage or 9.0 kg silage to supply 25% of their metabolisable energy requirement to support a liveweight gain of 1 kg per head day -1. The twenty steers on each treatment were run on similar five-hectare plots contained within a 4-year-old stand of tagasaste on a commercial farm, ‘Cantabilling Springs’. The steers browsing tagasaste without a supplement lost an average of 12.8 ± 3.7 kg whereas steers supplemented with lupins gained an average of 38.0 ± 7.7 kg. Steers supplemented with lupins plus silage gained an average of 29.1 ± 5.8 kg and steers supplemented with silage gained 5.1 ± 2.7kg during the period 4 February to 29 May. The liveweight change of the steers supplemented with lupins was not different (p<0.05) to those supplemented with lupins plus silage and the steers in both of these groups gained significantly more weight (p<0.05) than t hose supplemented with silage or those brow sing tagasaste with no supplement. Ammonia and the profile of volatile fatty acids were determined in rumen fluid collected via a stomach tube. Supplementation with lupins significantly increased the concentrations of ruminal ammonia, and decreased the ratio of acetic acid: propionic acid and the ratio of total volatile fatty acids: branched-chain volatile fatty acids in ruminal fluid. The concentration of metabolites and the activity of enzymes in plasma were within the normal range for each parameter assayed. Steers supplemented with lupins alone had higher (p<0.05) concentrations of urea in plasma than the steers on the other three treatments. The concentration of plasma creatinine for the steers consuming tagasaste without a supplement was higher (p