Effect of a post-lambing nitrogen fertiliser addition on the performance of an intensive lowland sheep breeding operation

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Despite the wealth of knowledge on the tactical use of nitrogen (N) fertilisers on pasture growth to address feed supply shortfall, remarkedly few studies have measured the impact on animal production. This study quantified the effect of a single post-lambing N fertiliser addition to a legume-based pasture on ewe and lamb performance and faecal nematode egg count. By weaning, pasture covers in paddocks receiving N fertiliser were 33% higher than control paddocks (1868 versus 1407 kg DM/ha, respectively) and ewe and lamb liveweights were 5% (76.7 versus 72.9 kg) and 6% (35.4 versus 33.1 kg) higher, respectively. This translated into 65 and 46 kg of additional ewe and lamb liveweight/ha, respectively. There were no significant differences in faecal egg counts (FEC) of either ewes or lambs between treatments. Pasture growth rates, back calculated from animal production and pasture covers translated into a pasture response of 28.5 kg DM/kg N applied. This is nearly twice the value used in feed budgeting by industry. The increase in ewe and lamb performance and higher pasture covers at weaning from the tactical use of N, adds greater flexibility and resilience to the system at a time when there is increasing volatility in weather patterns.