The effect of Vitex agnus castus fruit powder on performance, egg quality, blood biochemical parameters, immune response, reproductive system and tibial characteristics of laying hens in the second cycle of production

Introduction: Aromatic plants have been used traditionally in therapy against some diseases for a long time in the world. In different herbs, a wide variety of active phytochemicals, have been identified including the flavonoids, terpeniods, lignans, sulfides, polyphenolics, carotenoids, coumarins, saponins, plant sterols and phthalides (Craig 1999). Vitex agnus-castus (VAC) has been known as a phytoestrogenic herb. Traditionally, VAC fruit extract has been used for the treatment of menstrual disorders (amenorrhoea, dysmenorrhoea), premenstrual syndrome (PMS), corpus luteum insufficiency, hyperprolactinaemia, infertility, acne, menopause, and disrupted lactation (Daniele et al. 2005). Previous studies showed the efficacy of VAC in PMS, cycle disorders, hyperprolactinaemia and mastalgia in human and other animals; but, no study has been published on the effect of VAC on laying hens' performance in second cycle of production so far. Therefore, the aim of the present study was to investigate the effect of dietary supplementation of Vitex agnus castus fruit powder on performance, egg quality, immune responses, blood biochemical parameters, tibial characteristics and reproductive traits of laying hens in second cycle of production.Material and methods: This experiment was conducted to determine the nutritional value of VAC and to investigate its effects on performance and egg quality of laying hens in the second cycle of production. In the first step, AOAC methods were used for determination of the nutritional value of VAC. In the second step, 150 Leghorn Hy-Line (W-36) laying hens (from 80 to 90 weeks of age) were used based on a completely randomized design with 5 treatments, 5 replicates and 6 hens per each replicate. Treatment diets included 0 (control), 0.5, 1, 1.5, and 2 % of VAC powder. The birds received basal diet (corn and soybean based diet with 15.05 % crude protein and 2802 kcal/ kg metabolizable energy) in a mash form and formulized according to the Hy-Line W-36 (2016) nutrient requirements. The diet did not have any antibiotics and coccidiostats. Water and feed were provided ad-libitum during the experiment. Lighting program was 16 hours light and 8 hours darkness during the experiment. Egg weight (EW, gr), egg production (EP, %) and egg mass (EM, gr/hen/day) were recorded daily. Feed intake (FI, gr) was measured weekly and feed conversion ratio (FCR, grams of feed: grams of egg mass) was calculated weekly, too. In the present study, all performance parameters were presented in three periods (first 4 weeks, second 4 weeks, and entire 8 weeks). At the end of 2, 4, 6, and 8 weeks of the experiment, two eggs from each replicate were randomly selected for measurement of the egg qualitative traits and were presented for each periods. For determination of immune response, at 6 and 8 weeks of experiment, 0.5 mL of 20 % sheep red blood cells (SRBC) was injected in to the breast muscle of 2 hens per replicate. Then blood samples were taken from brachial vein 7 days after each injection (Nelson et al. 1995). At the end of experiment, one bird per each replicate were slaughtered for evaluating tibial characteristics (Zhang and Coon 1997) and reproductive traits (Renema et al. 2010).Results and discussion: The results of these experiments showed that crude protein (CP), ether extract (EE), crude fiber (CF), and crude ash were 10.5, 5.6, 56.0 and 12.6 % of dry matter, respectively. Performance parameters such as FI, EP, EM, EW and FCR were not significantly affected by various levels of VAC power (P>0.05). Egg quality factors such as Haugh unit, shell strength, shell percentage, shell thickness, and egg yolk color were not affected significantly by dietary treatments (P>0.05). However, albumin percentage was increased, but yolk percentage was decreased significantly during the first 4 weeks of experiment (P<0.05). In this regard, Karacollokcu et al. (2016) reported that supplementation of myrtus and vitex volatile oil (as alone or combination) in to the laying hen diet did not affect production performance and internal and external quality traits of the eggs, (except for egg specific gravity and yolk color) during the peak of egg production period. Vakili (2011) indicated that, adding essential oils of thyme and fennel into the diet of the laying hens significantly improved Haugh unit scores. This researcher believed that bird’s age and production cycle are the effective factors on eggs' internal and external quality. Vakili (2011) also showed that adding 40 mg/kg of thyme extracts to the diet of laying hens had no significant effects on egg shell quality parameters. Immune responses, tibia characteristics and reproductive traits of laying hens were not significantly affected by various levels of VAC powder (P>0.05). Also, blood concentration of glucose, HDL, ALT and AST enzymes were not affected by dietary treatments (P>0.05), but triglyceride and cholesterol were decreased (P<0.05). A decrease in serum cholesterol concentration could be related to hypocholesterolemic activity of herbal essential oils via the inhibition of hepatic 3- hydroxyl -3-methyl-glutaryl-coenzyme A reductase, the rate-limiting enzyme of cholesterol biosynthesis in smooth endoplasmic reticulum (Srinivasan 2004), and also high levels of VAC fiber. Moreover, previous studies indicated that some steroid like compounds (eg. phytoestrogens and ecdysteroids) have been isolated from VAC, which are capable of binding to estrogen receptors. It is concluded that these compounds can affect lipids’ metabolism in a dose dependent manner. Furthermore, the existence of antioxidant compounds such as flavonoids and iridoids, were beneficial in the normalizing of serum lipid levels (Bahrebar et al. 2010).Conclusion: The results of this experiment indicated that feeding VAC at 0.5-2 % had no significant effect on performance of laying hens, but it could improve lipid metabolism via decreasing the blood concentrations of triglyceride and cholesterol in laying hens.