Use of Jerusalem artichoke aerial parts as forage in fat-tailed sheep diet

Abstract This study was conducted to evaluate the effects of using different dietary levels of aerial parts of Jerusalem artichoke ( Helianthus tuberosus ) (JAAP) on voluntary feed intake, digestibility, microbial nitrogen (N) synthesis (MNS), and N retention in Iranian fat-tailed sheep. Twenty Chall rams averaging 15-18 months of age, and with an initial live body weight of 66.7 ± 7.01 (SD) kg, were randomly assigned to five dietary treatments (4 sheep/treatment) in which alfalfa hay was replaced with different levels (0, 25, 50, 75, or 100%, respectively) of JAAP. The animals were housed in individual metabolism boxes for a period of 21 days. The diets were mixed and offered two times a day (08.00, and 16.00 h) ad libitum. Feces and total urine production were collected from each ram every day. Daily dry matter intake (DMI), diet digestibility, MNS, and N retention were measured. As JAAP level increased in the diet, dry matter intake (P = 0.03) increased linearly, but organic matter (OM) intake, digestible organic matter intake (DOMI), neutral detergent fibre (NDF), crude protein (CP) intake, and metabolizable energy (ME) intake were not affected (P > 0.05). However, there was a quadratic effect of JAAP level on acid detergent fibre (ADF) intake when it was expressed per kg LW 0.75 . A linear decrease for OM digestibility (P = 0.01), CP digestibility (P = 0.01), ME digestibility (P = 0.01), and NDF digestibility (P = 0.03) was observed with increasing dietary JAAP levels, but dry matter, ADF, and non-fibre carbohydrates (NFC) digestibility were not affected (P > 0.05). Replacing alfalfa hay with JAAP caused a linear decrease in nitrogen balance (P = 0.03). However, no difference was observed in urinary purine derivatives and MNS. This study showed that the aerial parts of Jerusalem artichoke could be used as a valuable forage in the diet of Chall sheep without adverse effects on voluntary feed intake, DM digestibility, and MNS.