Farm Table says:
What is the problem?
Nitrate has been shown to be a methane mitigating feeding strategy – it, however, has also been linked to decreased feed intake and live weight gain. The effect of replacing dietary urea with nitrate (NO3) on wool growth, methane production and the response to additional sulfur (S) in the diet in relation to NO3 uptake was investigated in this study.
What did the research involve?
Forty-four weaned Merino wether lambs from Armidale NSW were fed four different diets with varying nitrate, urea, and elemental sulfur levels.
Methaemoglobin (MetHb) concentration in blood was measured at 4-time points throughout the study. Five lambs on day 43 were selected and used to measure dry matter, nitrogen, and sulfur utilization up until day 53. From days 67-39, 24 lambs (6 per diet) were used to measure methane production.
Clean wool growth rate and skin surface temperature were measured between day 24 and day 60 by clipping a 10 cm by 10 cm mid-side patch on the left and right side. Greasy wool was processed by a third party and washing yield calculated.
What were the key findings?
Replacing dietary urea with NO3 increased the rate of clean wool growth by 37%. Clean wool growth was increased by 26% when the elemental S content of the NO3 diet was increased to 0.18%. Dry matter intake, live weight gain, and feed conversion ratio did not differ the different levels of N and S in the diets. Sulfur supplementation did not affect N retention or the N and S content of wool.
The addition of 1.88% NO3 and 0.18% elemental S to a total mixed diet increased clean wool production and reduced methane production.