Abstract #M289

# M289
Effects of selenium source on, performance and antioxidant status in lactating dairy cows during oxidative stress-inducing conditions.
Lingling Sun1, Shengtao Gao1, Kun Wang1, M. V. Sanz Fernandez4, L. H. Baumgard5, Dengpan Bu*1,2, 1State Key Laboratory of Animal Nutrition, Institute of Animal Science, Chinese Academy of Agricultural Sciences, Beijing, China, 2CAAS-ICRAF Joint Lab on Agroforestry and Sustainable Animal Husbandry, World Agroforestry Centre, East and Central Asia, Beijing, China, 3Hunan Co-Innovation Center of Safety Animal Production, Changsha, Hunan, China, 4Comparative Physiology Group, SGIT-INIA, Madrid, Spain, 5Department of Animal Science, Iowa State University, Ames, IA.

In the current study, we utilized heat stress (HS) as an oxidative stress model to examine the effects of hydroxy-selenomethionine (HMSeBA). A novel dietary organic selenium (Se) source was compared with sodium selenite (SS) on performance, antioxidant status, and Se concentrations in serum and milk of dairy cows. Eight mid-lactation Holstein dairy cows (141 ± 27 DIM, 35.3 ± 2.8 kg of milk/d, parity 2 or 3) were individually housed in environmental chambers and randomly assigned to 1 of 2 treatments: SS supplementation (0.3 mg Se/kg DM; n = 4) or HMSeBA supplementation (0.3 mg Se/kg DM; n = 4). The trial was divided into 3 continuous periods: covariate period (9 d), thermal neutral (TN) period (28 d), and a heat stress (HS) period (9 d). During the covariate and TN periods, all cows were housed under TN conditions (20°C, 55% humidity). During HS, all cows were exposed to cyclical HS conditions (32–36°C, 40% humidity). All cows were fed SS during the covariate period, and dietary treatments were implemented during the TN and HS periods. The statistical model used to analyze the effect of treatment on the parameter was: Yijkl = µ + Ti + Pj +TPij + bXjk + C(TP)ijk +Dl + DTil +DPjl + DTPijl + εijkl. Compared with SS controls, cows fed with HMSeBA had higher total Se concentrations in serum (25.5%, P < 0.05) and milk (71.4%, P < 0.0001 = and total Se milk:serum concentration ratio (35.7%, P < 0.01). During HS, supplementing HMSeBA tended to increase milk yield (9.3%, P < 0.1) and decreased milk fat content during HS (18.1%, P < 0.05). There were no significant treatment effects on blood biochemistry, except for a lower alanine aminotransferase activity in the HMSeBA treatment (24.4%, P < 0.05). Glutathione peroxidase and superoxide dismutase activity did not differ between treatments, but cows supplemented with HMSeBA had higher total antioxidant capacity (20%, P < 0.05), and lower malondialdehyde (15.1%, P < 0.05), hydrogen peroxide (22.5%, P < 0.05), and nitric oxide (29.6%, P < 0,05) concentrations in serum. These results demonstrate that HMSeBA dietary supplementation effectively reduces HS-induced oxidative stress.

Key Words: dairy cow, hydroxy-selenomethionine, sodium selenite