An evaluation of the relationships between fecal nitrogen and digestibility, crude protein and dry matter intake of forages

Fresh liveoak leaves (Quercus spp)were mixed with fair quality alfalfa hay to form four rations containing o, 25, 50, and 75% livestock leaves on "as fed"weight basis. The rations were fed to four spanish goats in a 4x4 latin square sequence. Relationships betweeen fecel nitrogen and the dry matter intake, total notrogen intake, and dry matter digestibiliyt were evaluated. Daily feed intake fecal output and nitrogen balance were determined for each ration. In vibvo percentage digestibilities of dry matter, organic matter and nitrogen were calculated. In vitro, digestibility coefficients for action organic matter were aslo determined. Feed and fecal samples were analyzed for nitrogen (N), neutal detergent fiber (NDF), acid detergent fiber (ADF), and acid detergent fiber niterogen (ADFN) Fecal nitrogen output expressed as either grams per day or percentage nitrogen, exhibited no significant (p 05) relationship to either percentage digestibility,dietary nitrogen, total nitrogen intake (g/d)or organic matter intake. however, percentage dietary nitrogen (PDN)total nitrogen intake (TNI), and percentage nitrogen digested (PND)decreased significantly (p.05)as the level of livestoak leaves in the diets increased. URINARY NITROGEN (UN)in g/d varied among treatments and decreased with increased in the level of liveoak leaves (p05)as the level of liveoak leaves in the diets increased. Urinary nitrogen (UN)in g/d varied among treatments and decreased with increased in the level of liveoak leaves (P.05) Digestibility values different among treatmentin vitro method gave higher digestibility valuees for rations one (0% liveoak) and two (25% liveoak)and significantly (p.05) lower value for ration foru (75% liveoak). Treatment effects for in vivo organic matter digestibility were only significant at phowever, addition of more than 50% liveoak leaves to the diets resulted in a significant (p.05) decrease in OMI. NDF and ADF of feed and feces were positively related to the level of livestock leaves. However, ADEN showed a positive relationship to OMD. This relationship suggested that by correcting total FN for bound N, then technique may be used to predict digestibilities of browse-containing rations. This approach requires more data for validation.