Journal of Animal and Feed Sciences, 29, 2020, 316–322 https://doi.org/10.22358/jafs/131849/2020 The Kielanowski Institute of Animal Physiology and Nutrition, Polish Academy of Sciences, Jabłonna Ruminal degradability of Virginia fanpetals (Sida hermaphrodita) herbage and silage depending on the harvest time J.P. Michalski 1,4 , M. Borsuk 2 , Z. Nogalski 3 , M. Baranowska 2 , A. Krawczyńska 1 and C. Purwin 2 1 The Kielanowski Institute of Animal Physiology of Nutrition Polish Academy of Sciences Instytucka 3, 05-110 Jabłonna University of Warmia and Mazury in Olsztyn, 2 Department of Animal Nutrition and Feed Science, 3 Department of Cattle Breeding and Milk Evaluation Oczapowskiego 5, 10-719 Olsztyn, Poland KEY WORDS: Virginia fanpetals, silage, ruminal degradability, Sida hermaphrodita Introduction Virginia fanpetals (Sida hermaphrodita L.), also known as Virginia mallow), is cultivated in Europe as a source of biomass used for energy purposes. In terms of protein content, Virginia fanpetals is as good as the legume plants, widely used in ruminant nutrition, or even exceeds them. Moreover, Virginia fanpetals leaves contain a relatively high content of essential amino acids, especially lysine and methio- nine (Tarkowski and Truchliński, 2011). Contrary to legume plants, Virginia fanpetals does not con- tain saponins, phytoestrogens, lectins or cyanogenic glucosides, and antinutritional substances present in Virginia fanpetals are not a threat to animal health (Borkowska, 1994). On the other hand, Virginia fanpetals contains a rutin (Bandyukova and Ligai, 1987), a favonoid that inhibits the growth of many strains of bacteria and fungi (Ganeshpurkar and Saluja, 2017). Silage produced from Virginia fanpetals is a good substrate for biogas production (Oleszek ABSTRACT. Virginia fanpetals (Sida hermaphrodita) as a crop plant is characterized by high biomass yield, high protein content and good fbre composition. The aim of the study was to evaluate ruminal degradability of Virginia fanpetals herbage and silage of frst swath and regrowth. In situ ruminal degradability was determined using 2 rumen fstulated heifers fed standard diet. Degradation was estimated using nylon bags with dried feed placed in the rumen for 2, 4, 8, 16, 24, 48 and 72 h. Ensiling accelerated the dry matter (DM) degradability of frst swath in the frst hours of incubation and slowed down in the following hours. Ensiling the regrowth accelerated DM degradability both in the initial and fnal hours. In the silage from regrowth effective rumen degradability (ERD) of DM and neutral detergent fbre (NDF) were higher than in herbage. Ensiling accelerated crude protein (CP) degradability in both swaths so ERD of CP was higher in both silages. The results of the present study show that Virginia fanpetals green fodder preserved by ensiling can be successfully used as supplementary forage for ruminants. In particular, frst swath silage, due to its high protein content, can be used instead of legume silage in diets for cattle, and also it can reduce the need to use high-protein concentrate. However, ensiling caused signifcant acceleration of rumen protein degradability, which with unchanged DM and fbre degradability rate is not a desirable effect and requires simultaneous delivery of easily digestible carbohydrates into diets. Received: 12 November 2020 Revised: 19 December 2020 Accepted: 21 December 2020 4 Corresponding author: e-mail: j.p.michalski@op.pl