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Kreismane, D., Latvia Univ. of Life Sciences and Technologies, Jelgava (Latvia) | Aplocina, E., Latvia Univ. of Life Sciences and Technologies, Jelgava (Latvia) | Naglis-Liepa, K., Latvia Univ. of Life Sciences and Technologies, Jelgava (Latvia) | Berzina, L., Latvia Univ. of Life Sciences and Technologies, Jelgava (Latvia) | Frolova, O., Latvia Univ. of Life Sciences and Technologies, Jelgava (Latvia) | Lenerts, A., Latvia Univ. of Life Sciences and Technologies, Jelgava (Latvia)

Feeding livestock a balanced diet with a differentiated crude protein (CP) content, depending on the lactation phase, can reduce nitrogen emissions from livestock excrement and urine. A higher content of non-starch polysaccharides in livestock diets improves feed absorption in the livestock body and, consequently, nitrogen is emitted more from protein present in livestock manure than from urea acid present in livestock urine. The aim of the study is to calculate the ammonia emission reduction potential in Latvia by optimizing the feeding of dairy cows and ensuring life longevity, as well as provide justification for ammonia emission reduction in dairy farms. Calculations made by using the NorFor Model for optimization of dairy cow (Bos primigenius f. taurus) diets revealed that compared with lowyielding cows, a higher CP content diet fed to high-yielding cows at the beginning of lactation increased the amount of nitrogen (N) in their excrement and urine by 90–180 g dE−1. Reducing the CP content in the cow diet by an average of 10 g kgE−1 dry matter (DM) during mid-lactation resulted in the same trend. Reducing the CP content in the cow diet during late lactation and the dry period by another 20–30 g kgE−1 of DM, N emissions from excrement and urine significantly decreased. Increasing the lifespan of dairy cows also means reducing ammonia emissions from the farm. By increasing the number of lactations per cow on dairy farm, it is possible to reduce the number of heifers per cow. The total reduction of ammonia emissions in Latvia was calculated based on a long-term projection of a decrease of 0.1 heifer per dairy cow. Ammonia emissions could be reduced by 0.051 kt by decreasing the number of heifers by 12.54 thou. at the planned increase in the lifespan of dairy cows by 2030.

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