Delivery of dietary nitrate to sheep through lick-blocks for enteric methane abatement

Three experiments were undertaken to assess the voluntary intake of lick-blocks containing calcium nitrate by sheep, and the impact on enteric methane production. The effect of calcium nitrate inclusion rate on voluntary intake of lick-blocks was quantified in experiment one. Individually penned Merino sheep (n = 8) adapted to a basal diet were also each offered a lick-block containing either urea (n = 4) or calcium nitrate (n = 4). The blocks were provided for 4 x 8 d periods, with the blocks being replaced at the start of each period with a block of higher nitrogen (N) content (0.78%, 1.41%,2.82%,4.23% N; periods 1 - 4). Block intake showed a N-source x N-level interaction (P < 0.05), such that, while intake of urea containing blocks increased as N content increased (25 to 76 g/d), intake of nitrate containing blocks decreased (81 to 21 g/d).