Use of Jerusalem artichoke tops silage to replace corn silage in sheep diet

This study was performed to assess the effects of dietary substitution of different levels of Jerusalem artichoke (Helianthus tuberosus) tops silage (JATS) for corn silage (CS) on feed intake, digestibility, rumen parameters, blood metabolites, microbial nitrogen (N) synthesis (MNS) and N retention in Shal sheep (live body weight of 65.3 +/- 2.3). Four iso-energetic and iso-nitrogenous diets were formulated, in which CS was replaced by different levels (0, 180, 360 or 540 g/kg of diet dry matter [DM]) of JATS. The diets were assigned randomly to one of the groups (5 sheep/group) in a completely randomized design for a 31-days period (21 days for adaptation and 10 days for sample collection). Diets were offered as total mixed ration to ensure 10% orts. Daily feed intake, diet digestibility, rumen and blood parameters, MNS and N retention were determined. The data were analyzed using the PROC MIXED of SAS. The DM intake (DMI) and DM digestibility (DMD) were not affected by dietary treatments. With replacing CS by JATS, the ruminal ammonia-N concentration tended to increase (L, P = 0.088), total volatile fatty acids (WA) tended to decrease (L, P = 0.089), but rumen protozoa, molar proportions of individual WA and pH remained unchanged. Feeding sheep with diets containing JATS instead of CS had no effects on blood parameters, except urea-N, which was increased (L, P = 0.032) as the level of JATS rose in diet. No difference was observed in urinary purine derivatives and MNS. Urinary N tended to enhance (L, P = 0.080) and N retention tended to decrease (L, P = 0.065) when the sheep received diets with the increasing levels of JATS. Overall, the partial substitution of JATS for CS, up to 540 g/kg of DM, was possible in diet of Shal sheep without adverse effects on DMI, DMD, rumen fermentation, blood parameters and MNS, although blood urea-N raised slightly and total ruminal VFA and N retention somewhat declined. The aerial parts of the fresh JA can be preserved as a valuable silage to use in sheep diets.