Saving the Planet, Feeding the World Methane emissions and feeding behavior of feedlot cattle supplemented with nitrate or urea J Velazco, D Cottle and R Hegarty Canberra ISRP/ISNH 2014

Introduction Nitrate may serve as a NPN source in ruminant diets in place of urea Nitrate can produce toxicity (methaemoglobinemia) Nitrate inclusion reduces methane production in a predictable manner Saving the Planet, Feeding the World

The study was conducted to verify that nitrate salts can safely replace urea in the TMR of feedlot cattle and will reduce daily methane emissions as expected from published literature. Saving the Planet, Feeding the World Aim of the study

Materials and Methods 20 Angus steers (353 kg ±18 kg) were randomly allocated to two treatment groups (Iso-N; 0.9% Urea v 2.6% CaNitrate) Adapted to increasing levels of grain and NPN over 30 d. A single Methane Emissions Monitor (GEM; short-term methane measurement device) was then moved weekly between groups (2 x 1-week periods per treatment). Saving the Planet, Feeding the World

Measurements – Methaemoglobin (spectroscopic method, Hegesh 1970) – Methane production (GreenFeed, C-Lock inc) – Feed Intake (automatic feeders, Bindon 2001) – Feeding behavior (number and weight of individual meals) Materials and Methods

Results Methaemoglobin Saving the Planet, Feeding the World

Results UreaNitrateP-value Dry matter intake (kg/d) Daily methane production (gCH 4 /d) Methane yield (g CH 4 /kg DMI) Delay between feeding and CH 4 measure (h) Number of meals per day (meals/d) Meal weight (kg/meal) <0.001

Results UreaNitrateP-value Dry matter intake (kg/d) Daily methane production (gCH 4 /d) Methane yield (g CH 4 /kg DMI) Delay between feeding and CH 4 measure (h) Number of meals per day (meals/d) Meal weight (kg/meal) <0.001

Feeding pattern and CH 4 measurements Feed intake and time after feeding affect momentary CH 4 emission rate (Crompton 2011) A linear Consumption Index was developed attempting to adjust DMP estimates for feeding pattern???  ??? Saving the Planet, Feeding the World

Dietary nitrate tended to reduce emissions and change feeding pattern of feedlot cattle. While emission estimates based on short-term measures were comparable with predicted emissions, need to clarify if timing and size of meals needs consideration. Saving the Planet, Feeding the World Conclusion

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