The effects of adding aqueous extract and dried aerial part powder of Tribulus terrestris on productive performance and blood parameters of laying hens

Tribulus terrestrisis (TT) is a source for industrial production of medicinal preparations based on its saponin fraction. This plant is extremely rich in substances having potential biological activity, such as saponins, flavonids, alkaloids, glycosides, phytosteroids, and other constituents such as tannins, which influence gastrointestinal microflora and exert astringent effects due to their antibacterial properties. The steroidal saponins, such as dioscin, diosgenin, and protodioscin, are behind the plant's well-known beneficial effects on increasing sex hormones, leading to an increase in reproductive performances. The objective of the present study was to investigate the effects of adding aqueous extract and dried aerial part powder of TT on performance and blood parameters of hens during the laying period (28 to 40 wk of age). A total of 210 Hy-LineW-36 were randomly assigned to 5 treatments, with 6 replicates of 7 hens each. The experiment was a completely randomized design with 5 levels of TT, including zero (T1), 5 mg (A5), or 10 mg/kg BW (A10) aqueous extract added to drinking water and 5 mg (F5) or 10 mg (F10) aerial part powder per kilogram BW added to the feed of laying hens. The results indicated that daily feed intake decreased (P < 0.001) when hens were fed F10; lower feed intake could be attributed to the fiber or saponin content of TT. Feed conversion ratio (FCR) improved (P < 0.05) when F5 was added; lower FCR could be attributed to the active ingredient of TT, protodiosin, which may increase the reproductive activities and production performance of laying hens. Egg production (P < 0.01), egg weight (P < 0.05), and egg mass (P < 0.05) increased when hens were fed F5; increase in these parameters could be attributed to the ovary activity and overall stimulation of vitality and metabolism or to a protodiosine mechanism. However, dietary treatment had no effect (P > 0.05) on egg and yolk index or Haugh unit. Shell thickness and weight were increased (P < 0.01) by the addition of aqueous extract or dried aerial part powder of TT to the diets. TT is a rich source of Ca and this mineral increased eggshell thickness and shell weight. Dietary treatment decreased (P < 0.001) yolk color and egg yolk cholesterol. Cholesterol content of eggs (P < 0.05) and blood triglyceride and glucose content (P < 0.001) decreased with dietary treatments. This plant has no substance that can influence yolk color, and decreasing cholesterol and triglycerides could be attributed to higher egg production and to content of saponine and flavonoids, which block the enzyme system, having a key role in cholesterol synthesis. There was no significant effect of dietary treatments on LDL, HDL, and total protein content of plasma. From the results of this experiment, it can be concluded that TT aqueous extract or powder has beneficial effects on performance and blood parameters of laying hens.