Effects of polyethylene glycol or activated sodium bentonite supplementation on vital signs, blood biochemical and hematological parameters of Saanen goats fed pistachio by-products under heat stress

Recently, pistachio by-products (PBP) have been used to reduce production costs in ruminant nutrition. However, the tannins and phenolic compounds in PBP as anti-nutritional compounds limit the use of this agricultural by-product in ruminant diets. Therefore, nutritionists recommend the use of tannin-binding compounds such as polyethylene glycol (PEG) in diets with high tannins contain. It has also been shown that sodium bentonite can be used as a tannin inactivator in the diet of ruminants. Therefore, this study was conducted to evaluate the effect of supplementation of polyethylene glycol or activated sodium bentonite (ASB) on feed intake, vital signs, biochemical and hematological parameters of Saanen goats fed pistachio by-products under heat stress.

Fifteen Saanen male goats were assigned to three treatment groups in a completely randomized design. The experimental period lasted 30 days (25 days for the period before heat stress and 5 days for heat stress). Three experimental diets consisted of a diet containing 30% DM pistachio by-products with no additive (control); the control diet supplemented with PEG at 1% of DM (PEG group), and the control diet supplemented with activated sodium bentonite at 1% of DM (ASB group). To measure dry matter intake, the amount of feed residue was recorded daily. Goats were also weighed at the end of each week to examine weight changes. To measure ruminal pH, on the last day of the experiment and 2 hours after morning feed consumption, ruminal pH was recorded with a pH meter. Heart rate, respiration rate (per minute), and rectal temperature were measured during the last three days of the stress period to record vital signs. Also, on the last day of the experiment, two series of blood samples (5 ml) were collected from the jugular vein to determine biochemical and hematological parameters. Data were statistically analyzed using GLM procedure and SAS 9.1 software.

The results showed that the amount of DMI in the control treatment was higher than other groups (P <0.05). Rumen pH was not affected by treatments (P≤0.05). In terms of vital signs, heart rate and respiration in PEG treatment were higher than other treatments (P <0.05). No significant differences were observed between treatments in terms of blood biochemical parameters (P≤0.05). However, according to hematological parameters, the concentration of monocytes, eosinophils, and fibrinogen in PEG treatment were lower than other treatments (P <0.05). Besides, hormonal parameters showed that Cortisol concentration in PEG treatment was significantly higher than other groups (P <0.05).

In conclusion, the use of activated sodium bentonite in diets containing 30% PBP to feed goats under short-term heat stress can increase the monocyte concentration and strengthen the immune system in these animals without adversely affecting DMI, vital factors, and animal welfare.