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 LW0.75. 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.