Abstract
This study aimed to investigate the effects of grape seed extract (GSE) supplementation on antioxidant activity, inflammatory markers, hematological and physiological responses during the suckling period in heat-stressed calves. Sixty Holstein female calves (3 d of age, 40.6 ± 2.17 kg of BW) were randomly divided into four dietary groups. Each group consisted of 15 calves; the milk was supplemented with 0 (CON) 25 (GSE1), 50 (GSE2), and 100 (GSE3) mg/kg BW/day of GSE. On d 3, 33, and 63 blood samples were collected, rectal temperatures (RT) and respiratory rates (RR) were measured three days a week. Calves were exposed to chronic heat stress during the study period and were weaned on d 63. Plasma malondialdehyde (MDA) and tumor necrosis factor-alpha (TNF-α) concentrations decreased (P < 0.01) in all GSE supplemented groups compared to the CON group. Also, interferon-gamma (IFN-γ) concentration decreased (P = 0.03) only in calves fed GSE1. Plasma total antioxidant capacity (TAC) concentration increased (P = 0.02) in calves fed GSE3 on d 33 compared to the CON group, while the concentration of superoxide dismutase (SOD) was higher (P < 0.001) in the GSE2 and GSE3 groups compared to CON and GSE1. The hematocrit percentage, hemoglobin value, RBC, and eosinophil counts were higher (P < 0.01) in all GSE supplemented groups compared to CON. Calves fed GSE1, GSE2 and GSE3 had lower (P < 0.001) neutrophil count compared to CON on d 63. All GSE-supplemented groups had a decreased (P < 0.001) RR compared to CON, while calves fed GSE2 had a tendency to decrease (P = 0.10) in RT. It was concluded that supplementation with 50 and 100 mg/kg BW/d GSE could improve antioxidant, anti-inflammatory activities, and hematological parameters of calves against oxidative stress, and also reduce the effect of heat stress by reducing the respiratory rate.
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