biostudies-literatureThompson JPAgri-Food and Biosciences InstituteU.S. Department of AgricultureBiotechnology and Biological Sciences Research Council101698https://www.ebi.ac.uk/biostudies/studies/S-EPMC12708440biostudies-literatureUnknown19(12)Ruminants have poor nitrogen use efficiency, with 70% of total ingested nitrogen (N) excreted. Much of this excreted N is in the form of urinary urea which is easily hydrolysed to ammonia. Increasing ammonia production has negative impacts on environmental and human health. Dietary supplementation with condensed tannins (CTs) could be a solution as they bind to the N source (protein) in the rumen, preventing degradation, allowing more N to reach the abomasum for digestion and absorption. However, if this N is not absorbed, it results in a shift in N excretion from urine to faeces. The aim of this study was to evaluate the effect of willow containing CTs through a 21% DM dietary inclusion of two willow varieties (Salix Beagle: BG and Salix Terra Nova: TN) mixed with grass silage. Willow treAnimal : an international journal of animal bioscienceSupplementation with willow containing condensed tannins shifted nitrogen excretion from urine to faeces in yearling ewes.PMC12708440BB/T008776/1Thompson JPSafoi LZeller WESoutham ADTheodoridou KLudwig CCristobal-Carballo OYan THuws SLloyd GRStergiadis SfalseSupplementation with willow containing condensed tannins shifted nitrogen excretion from urine to faeces in yearling ewes.Ruminants have poor nitrogen use efficiency, with 70% of total ingested nitrogen (N) excreted. Much of this excreted N is in the form of urinary urea which is easily hydrolysed to ammonia. Increasing ammonia production has negative impacts on environmental and human health. Dietary supplementation with condensed tannins (CTs) could be a solution as they bind to the N source (protein) in the rumen, preventing degradation, allowing more N to reach the abomasum for digestion and absorption. However, if this N is not absorbed, it results in a shift in N excretion from urine to faeces. The aim of this study was to evaluate the effect of willow containing CTs through a 21% DM dietary inclusion of two willow varieties (Salix Beagle: BG and Salix Terra Nova: TN) mixed with grass silage. Willow tre2025-01-01T00:00:00Z2025 Dec2026-06-06T04:09:47.277Z2026-05-25T03:12:04.119ZS-EPMC127084404131416210.1016/j.animal.2025.101698