Effect of dietary tannins on milk yield and composition, nitrogen partitioning and nitrogen use efficiency of lactating dairy cows: A meta‐analysis. Issue 5 (12th March 2020)

• Record Type: Journal Article
• Authors: Herremans, Sophie; Vanwindekens, Frédéric; Decruyenaere, Virginie; Beckers, Yves; Froidmont, Eric
• Is Part Of: Journal of animal physiology and animal nutrition. Volume 104:Issue 5(2020)
• Page Start: 1209
• Page End: 1218
• Publication Date: 2020-03-12
• Subjects: polyphenols -- protein -- ruminant -- secondary plant metabolites; Animal nutrition -- Periodicals; Feeds -- Periodicals; 636.085
• DOI: 10.1111/jpn.13341
• Languages: English
• ISSNs: 0931-2439

Abstract

Abstract: Tannins are secondary plant compounds which have been extensively studied in order to improve the nitrogen use efficiency (NUE) of ruminants. A meta‐analysis was performed of 58 in vivo experiments comparing milk yield, composition and nitrogen metabolism of lactating dairy cows fed diets with or without tannins. The meta‐analysis shows that tannins have no impact on corrected milk yield, fat and protein content or NUE ( p > .05). However, tannins reduce ruminal ammoniacal nitrogen (N) production by 16% (from 10.95 to 8.47 mg/dl on average), milk urea by 9% (from 15.82 to 14.03 mg/dl) and urinary N excretion (−11%; p < .05). This is compensated for by a lower apparent N digestibility (61.51% with dietary tannins compared to 66.17% without). The effect of tannin on N metabolism parameters increases with tannin dose ( p < .05). The shift from urinary to faecal N may be beneficial for environment preservation, as urinary N induces more harmful emissions than faecal N. From a farmer's perspective, tannins seem unable to increase fat‐ and protein‐corrected milk yield or reduce feed protein requirements and thus have no direct economic benefit. Potentially less costly than tannin extracts, forage or by‐products naturally rich in tannins could still be useful to reduce the environmental impact of ruminant protein feeding.