The objective of this experiment was to study the effects of interactions between lower quality grass silage (GS) dominated by orchardgrass (Dactylis glomerata L.) and maize silage (MS) (Zea mays L.) on ad libitum intake, digestibility and N retention in wether sheep. The study consisted of four feeding treatments involving GS and MS alone, and GS and MS mixtures in ratios of 67:33 or 33:67 (DM basis) fed twice daily. The GS was harvested at the beginning of flowering of orchardgrass (about 35 % of plants were in flower) while the MS used was of lower DM and starch concentration (264 g kg-1 fresh weight and 211 g kg-1 DM respectively). Mean DM content of GS was 408 g kg-1 fresh weight. MS was lower in crude protein (CP) (62 g kg-1 DM) than the GS (98 g kg-1 DM) (P<0.001). GS contained larger quantities of neutral detergent fibre (NDF) and acid detergent fiber (ADF) (P<0.001) than MS. Inclusion of MS in the diet (33 % vs. 67 %) had positive linear effects on fresh matter (FM) voluntary intake (P<0.05), digestibility of DM, organic matter (OM), digestible OM in the DM (D-value) (P<0.05), starch digestibility (P<0.05), N intake (P<0.01), N output in faeces (P<0.05) and absorbed N (P<0.05). A positive associative effect of GS and MS was observed for all intake parameters measured (FM, DM, OM, NDF) (quadratic, P<0.05 to P<0.01), digestibility of DM, ADF (quadratic, P<0.05), CP (quadratic, P<0.01), N intake and absorbed N (quadratic, P<0.01). It was concluded that positive interactions of GS and MS were recorded for a limited number of parameters because of the lower quality MS than required for the full benefit of two forages fed together.Cilj istraživanja bio je utvrditi utjecaj interakcije travne silaže lošije kvalitete (TS) u kojoj su dominirale klupčasta oštrica (Dactylis glomerata L.) i kukuruzna silaža (KS) (Zea mays L.) na ad libitum konzumaciju, probavljivost i balans dušika (N) u hranidbi kastriranih ovnova. Istraživana su četiri hranidbena tretmana: 100 % TS, 100 % KS, te kombinacije TS i KS u omjeru 67:33 ili 33:67 bazirano na suhoj tvari (ST). Životinje su hranjene dvaput dnevno u isto vrijeme. Tratina za proizvodnju TS košena je u početku cvatnje klupčaste oštrice (oko 35 % biljaka u cvatnji), a KS je sadržala 264 g ST kg-1 svježeg uzorka i 211 g škroba kg-1 ST. Sadržaj ST u TS iznosio je 408 g kg-1 svježeg uzorka. Sadržaj sirovih proteina (SP) u KS bio je niži (P<0.001) u odnosu na TS (62 g kg-1 ST i 98 g kg-1 ST, respektivno). Sadržaj neutralnih detergent vlakana (NDF) i kiselih detergent vlakana (ADF) bio je viši u TS u odnosu na KS (P<0.001). Dodatak KS (33 % vs. 67 %) u obrok uzrokovao je pozitivan linearni utjecaja na konzumaciju svježeg obroka (P<0.05), probavljivost ST, organske tvari (OT), probavljivost OT u ST (D vrijednost) (P<0.05), probavljivost škroba (P<0.05), konzumaciju N (P<0.01), količinu N izlučenog fecesom (P<0.05) i količinu apbsorbiranog N (P<0.05). Pozitivan asocijativan utjecaj TS i KS utvrđen je za sve mjerene parametre konzumacije (svježi obrok, ST, OT, NDF) (kvadratni, od P<0.05 do P<0.01), probavljivost ST, ADF (kvadratni, P<0.05), SP (kvadratni, P<0.01), konzumaciju N i količinu apsorbiranog N (kvadratni, P<0.01). Zaključeno je da je pozitivan združeni učinak TS i KS u hranidbi kastriranih ovnova izostao za pojedine mjerene parametre, i to zbog nedostatka energije u obroku, tj. niže kvalitete KS
