Effect of Ajwain essential oil and β-agonist zilpaterol hydrochloride on performance and some enzymatic markers associated with cold stress in paternal line of Arian broiler chickens

This study was conducted to determine the effects of dietary supplementation of ajwain essential oil (EO) and Zilmax® (Zilpaterol hydrochloride) on growth performance and some blood parameters associated with cold stress in male chicks belong to paternal line of Arian broiler chickens. Cold environmental temperatures tend to increase blood triiodothyronine (T3) levels, required for the generation of additional metabolic heat to maintain body temperature in colder environments. The subsequent increase in basal metabolic rate results in an increase in oxygen demand and the heart attempts to maintain oxygen supply to the organs and muscles, thus chronically leading to pulmonary hypertension syndrome (PHS), right ventricular hypertrophy, ascites and eventually death (Gupta 2011). According to Currie (1999) the main reasons of the etiology of ascites could be classified as: pulmonary hypertension, cardiac pathologies, and cellular damage due to oxidative stress caused by increased reactive oxygen species (ROS) production. Enkvetchakul et al. (1993) verified that chickens with ascites suffered from high oxidative stress. Therefore, ROS production is increased during hypoxia and ascites (Dawson et al., 1993). As a result of oxidative stress, major antioxidants, such as glutathione, α-tocopherol, and ascorbic acid are reduced in the liver and the lungs of broilers with PHS (Bottje and Wideman 1995). Vitamin E, vitamin C, and other antioxidants have beneficial effects as they scavenge free radicals (Gupta, 2011, Ruiz -Feria, 2009) .
It has been reported that supplementation of vitamin C (Nemati et al. 2017) in diet of broilers and herbal essential oils as natural antioxidants in the diet of laying hens (Torki et al., 2015) under cold stress conditions resulted improved performance parameters (body weight and feed conversion ratio). Ascites related traits (low red blood cell count, hematocrit, T3, heart weights and high T4) were also improved due to antioxidant (Coenzyme Q10 and vitamin C) supplementation in the diet of broiler chickens (Nemati et al. 2017).
Various β-adrenergic agonists have been shown to be capable of improving weight gain when added to the feed of various domestic species (Malucelli et al., 1994). Moreover it was eported that, the use of clenbuterol at 0.25 ppm to reduce mortality due to the ascites syndrome in broilers (Ocampu et al. 1998) .We hypothesized that dietary addition of C. copticum and Zilpaterol hydrochloride in chicks diet could attenuate cold stress effects with respect to mortality, serum enzyme activity and plasma levels of thyroid hormones.
Material and A total of 196 day-old male chicks were purchased from Babolkenar Arian Line Breeding Center, Babolkenar, Iran. Birds were divided into cold and normal temperature groups after rearing until 13 d. Four dietary treatments (basal diet, dietary addition of ajwain EO at 150 and 450 ppm and zilmax® at 1.6 ppm) each with corresponding replicates (24 replicate; n=192; one male chick in each individual cage as a replicate) were fed to chicks at two different thermal programming environment at the grower phase. At the end of the grower phase, cold thermal program was stopped and ambient temperature became the same and normal through the finisher phase for all chicks. This study was done according to a Complete Randomized Design with 8 treatments. Feed intake (FI) and body weight gain (BWG) were measured at the end of each rearing phase. At the end of experiment (42 days of age), eight birds per treatment were sacrificed, and their RV: TV ratios calculated. At 13, 29 and 36 days of age four birds of each treatment were randomly taken for blood collection from wing vein and the assay of serum Alkaline Phosphatase (ALP), Alanine Transaminase (ALT), Aspartate Aminotransferase (AST) and thyroid hormones levels using commercial kits. Heterophyl to lymphocyte ratio as a measure of stress and hematocrit as a measure of PHS were also assessed in blood samples.
Dietary addition of 150 ppm ajwain EO decreased body weight gain (P≤0.05) but has no significant effect on feed conversion ratio (FCR) of chicks at growing phase (P>0.05), and did not affect overall performance at the end of the experiment as well. The main effect of cold exposure was significant (P The use of zilpaterol hydrochloride at 0.3 ppm, in the diet did not affect significantly daily weight gain (DWG) and feed conversion ratio (FCR) and had no ascites attenuating effects on paternal line of broiler breeders. Dietary supplementation of ajwain essential also did not affect significantly performance of birds, but may be effective in attenuating cold stress due to its illustrated antioxidant (according to MDA concentration) and anti-stress effects (Decreasing effect on H:L ratio and some enzymatic assays) at the present study. Further research in still required to confirm this hypothesis.