126 Effect of astaxanthin supplementation on in vitro embryo development and immune response of dairy cows

Abstract

Astaxanthin is a carotenoid antioxidant reported to have beneficial effects on animals, including immune response and reproductive function. This study aimed to determine the effect of daily supplementation of dairy cows with astaxanthin on leukocyte population and oocyte developmental potential in summer. Lactating Holstein cows (n = 45) from a compost barn in Paraná, Brazil, received 0 (control), 0.25 (low AST), or 0.5 (high AST) mg/kg per day of astaxanthin for 75 days in the summer (January to March 2020). Groups were homogeneous according to parity, days in milk, and milk yield. Blood cell count (white blood cells, lymphocyte, neutrophil, monocyte, basophil, and eosinophil) was performed on sodium citrate-treated blood samples collected every 14 days. Ovum pickup (OPU) was then conducted three times at a 20-day interval and oocytes underwent IVF to assess their developmental competence. Data were tested for normality of residues (Shapiro-Wilk test) and homogeneity of variances (F max test), and square root-transformed when premises for ANOVA were not met. One-way ANOVA (embryo development data; effect of astaxanthin) or two-way repeated-measures ANOVA (oocyte quality, and leukogram data; effect of astaxanthin, time, and interaction) followed by Tukey’s multiple comparisons test were performed using GraphPad Prism vs.7.0 (GraphPad Inc.). During the experimental period, animals were exposed to an average air temperature of 29.40 ± 0.20°C and relative humidity of 58.00 ± 0.80%. Physiological parameters were as follows: heart rate of 53.55 ± 0.34 beats/min, respiratory rate of 48.39 ± 0.31 breaths/min, body surface temperature of 32.83 ± 0.11°C, and rectal temperature of 38.77 ± 0.02°C. A higher white blood cell count was observed for the low AST group compared with control (P = 0.0203) and high AST (P = 0.0107) groups after 56 days of supplementation. For lymphocyte quantification, an effect of astaxanthin (P = 0.0440) and astaxanthin × time of supplementation interaction (P = 0.0239) were observed. The lower dose of astaxanthin caused an increase in lymphocyte number, which could be detected after 42 days of astaxanthin supplementation (P ≤ 0.05). No significant differences were detected for other leukocyte types. No effect of astaxanthin was observed on total number of oocytes recovered per cow except for the first OPU, in which more oocytes were retrieved from cows supplemented with 0.5 mg/kg per day of astaxanthin (9.92 ± 1.95) compared with control (3.58 ± 0.73; P = 0.0179) and low AST (4.23 ± 1.18; P = 0.0358) groups. In addition, more viable oocytes (grades 1, 2, or 3 according to cytoplasm homogeneity and cumulus cells layers) were obtained from animals supplemented with 0.5 mg/kg per day of astaxanthin (3.17 ± 0.39) compared with control (1.67 ± 0.31; P = 0.0050) and low AST (1.56 ± 0.26; P = 0.0022) groups. Interestingly, no differences were observed for in vitro developmental potential among groups. These data suggest that a low dose of astaxanthin can affect lymphocyte mobilization, whereas a higher dose is required to improve the number of morphologically viable oocytes obtained by OPU from Holstein cows during summer.