An investigation of the nutritional value of camelthorn (Alhagi maurorum) at three growth stages and its substitution with part of the forage in Afshari ewes’ diets

Abstract

The camelthorn (Alhagi maurorum: AM) is a drought-resistant plant belonging to the Fabaceae family, but its nutritional value has received little attention. First, the nutritional value of AM was investigated at three growth stages (vegetative, flowering, and seeding) by different laboratory and in vitro protocols. Second, the partial replacement of conventional dietary forage with AM on dry matter intake (DMI), milk yield and composition, nutrient digestibility, blood metabolites, and ruminal fermentation parameters of Afshari ewes were examined. Apart from ether extract (EE), other chemical compounds were all affected by three growth stages. Crude protein (CP) content ranged from 100 for the seeding stage to 122 g/kg DM for the vegetative stage. The concentration of minerals in the seeding stage was highest. At the vegetative, flowering, and seeding stages the values for relative feed value (RFV) were 112, 94.6 and 85.3, neutral detergent fiber (NDF) were 449, 495 and 525 g/kg DM, and non-fiber carbohydrates (NFC) were 351, 302 and 263 g/kg DM, respectively. The highest concentrations of total volatile fatty acids (TVFA, P = 0.002) and propionate (P = 0.010) were observed when AM at the vegetative stage incubated in the culture medium. The highest potential gas production (P = 0.002) and acid-base buffering capacity (P < 0.001) were also observed in the vegetative stage. The in vivo study indicated that the some nutrient (DM, OM) digestibility, milk yield and milk composition were unchanged when the conventional dietary forages were partially replaced with AM at the vegetative or flowering stages. Animal performance was affected by the growth stage when ewes fed a diet containing AM at the seeding stage compared to the control group. Ewes receiving AM at the seeding stage exhibited lower body weight change (P = 0.008), EE (P = 0.049), CP (P < 0.001) and NDF (P < 0.001) digestibility in comparison to the control group. The in vitro study showed that the nutritional value of AM at the vegetative stage was higher than the other stages. Partial replacement of dietary forage with AM at the vegetative or flowering stages at a rate of 250 g/day had no adverse effects on the ruminal fermentation, some nutrient digestibility, blood metabolites, and animal performance; however, at the seeding stage, it should be used with more caution.