Effect of transport on blood selenium and glutathione status in feeder lambs

Effects of Supranutritional Selenium Supplementation During Different Trimesters of Pregnancy on Humoral Immunity in Beef Cattle at Parturition

Supranutritional Se supplementation may improve immune responses in beef cattle. Immunity is compromised in beef cattle during the periparturient period. This study aims to determine the best time during pregnancy to supplement beef cows with Se-yeast to optimize humoral immunity at parturition. Multiparous, black Angus and Angus cross cows (n = 79) were used in the study. All cows had ad libitum access to a mineral supplement containing 120 mg/kg Se (US FDA regulations) from Na selenite. In addition, all cows except controls (CTR) received Se supplementation of 105 mg Se/week from Se-yeast boluses administered once weekly during their specific treatment trimester of gestation (TR1, TR2, or TR3) for 13 weeks. This dosage was supranutritional equaling 5 × the upper range of US FDA Se administration regulations. Blood was collected at parturition from all cows. Laboratory analyses studied to assess humoral immunity included measuring IBR, BVD types 1 and 2, PI3, and BRSV serum neutralization titers post vaccination, assessing total IgM and antigen-specific IgM concentrations, and determining complement-mediated bacterial killing percentages. Statistical analyses were performed using GraphPad Prism and SAS 9.4. Supranutritional Se-yeast supplementation increased whole-blood (WB) Se concentrations regardless of trimester of supplementation (all P < 0.0001). Supplementation during TR2 and TR3 was more effective in increasing WB-Se concentrations at parturition than during TR1 or CTR (all P < 0.0001). TR2 cows had higher serum neutralization titers for BRSV compared with CRT cows (P = 0.03). Total serum IgM and Vibrio coralliilyticus-specific IgM concentrations were highly correlated (r = 0.78; P < 0.0001). Compared with CTR cows, TR1, TR2, and TR3 cows had similar total IgM concentrations (all P ≥ 0.19) and similar Vibrio coralliilyticus-specific IgM concentrations (all P ≥ 0.47). Complement-mediated bacterial killing percentages were greater in TR2 and TR3 cows (> 99.6%) compared with TR1 (93.9%) and CTR (89.3%) cows, and all Se-supplemented TR groups were greater than CTR cows (all P ≤ 0.05). The significant group differences in the complement-mediated bacterial killing assay reflected WB-Se concentrations. Supranutritional Se-yeast supplementation during TR2 and TR3 is associated with higher serum neutralization titers for some viral antigens, as well as enhanced complement-mediated bacterial killing in cows at parturition. These findings suggest that Se supplementation during later trimesters of pregnancy may help combat infectious disease challenges during the periparturient period in beef cattle.

Impact of selenium biofortification on production characteristics of forages grown following standard management practices in Oregon

INTRODUCTION

Low selenium (Se) concentrations in soils and plants pose a health risk for ruminants consuming locally-grown forages. Previous studies have shown that Se concentrations in forages can be increased using soil-applied selenate amendments. However, the effects of foliar selenate amendments applied with traditional nitrogen-phosphorus-potassium-sulfur (NPKS) fertilizers on forage yields, and nutrient contents, and agronomic efficiencies are unknown.

METHODS

Using a split plot design, we determined the effects of springtime sodium selenate foliar amendment rates (0, 45, and 90 g Se ha^-1) and NPKS application (none, NPK for grasses/PK for alfalfa, and NPKS/PKS fertilization at amounts adapted to meet local forage and soil requirements) on forage growth and N, S, and Se concentrations, yields, and agronomic efficiencies. This 2-year study was conducted across Oregon on four representative forage fields: orchardgrass (Dactylis glomerata L.) in Terrebonne (central Oregon), grass-clover mixture in Roseburg (southwestern Oregon), and both grass mixture and alfalfa (Medicago sativa L.) fields in Union (eastern Oregon).

RESULTS

Grasses grew poorly and were low in N content without NPK fertilization. Fertilization with NPK/PK promoted forage growth, increased forage N concentrations, and had to be co-applied with S when plant available S was low. Without Se amendment, forage Se concentrations were low and further decreased with NPKS/PKS fertilization. Selenate amendment linearly increased forage Se concentration without adversely affecting forage yields, N and S concentrations, or N and S agronomic efficiencies.

DISCUSSION

Importantly, S fertilization did not interfere with Se uptake in Se amended plots. In conclusion, co-application of NPKS/PKS fertilizers and foliar sodium selenate in springtime is an effective strategy to increase forage total Se concentrations, while maintaining optimal growth and quality of Oregon forages.

Supranutritional Selenium-Yeast Supplementation of Beef Cows during the Last Trimester of Pregnancy Results in Higher Whole-Blood Selenium Concentrations in Their Calves at Weaning, but Not Enough to Improve Nasal Microbial Diversity

We previously reported that feeding Se-biofortified alfalfa hay to weaned beef calves in a preconditioning program increases whole-blood Se (WB-Se) concentrations and nasal microbiome abundance and diversity during the preconditioning period, decreases morbidity and mortality during the feedlot period, and increases carcass weight and quality at slaughter. The objective of the current study was to see whether similar improvements can be achieved through Se supplementation of dams during various pregnancy trimesters. In a two-year experimental study, 80 Angus-cross cows received once-weekly Se-yeast boluses containing 105 mg of Se, during either the first (TR-1), second (TR-2), or third (TR-3) pregnancy trimester, or were not bolused (CTR). Whole-blood Se concentrations were higher from CTR, to TR-1, to TR-2, and to TR-3 in newborn calves (all p < 0.01). At weaning, only calves from TR-3 mothers had higher WB-Se concentrations compared with calves from CTR mothers (p = 0.02), and no significant differences in nasal microbiome abundance and diversity or nasal microbiota were observed. In the feedlot period, morbidity was low, and no differences were observed. At slaughter, no differences in carcass weight and quality were observed. In conclusion, Se supplementation of pregnant cows is effective for increasing WB-Se concentration of newborn calves, and the increase can be sustained until weaning for calves born to TR-3 dams. However, the increase in WB-Se concentrations is small and does not result in beneficial changes in the nasal microbiome. Thus, calves should be fed Se-biofortified forages again at weaning in a preconditioning program in order to diversify the nasal microbiome prior to entering the feedlot.

Effects of Sub-Lethal Doses of Selenium Nanoparticles on the Health Status of Rats

Selenium nanoparticles (SeNPs) are fast becoming a key instrument in several applications such as medicine or nutrition. Questions have been raised about the safety of their use. Male rats were fed for 28 days on a monodiet containing 0.5, 1.5, 3.0 and 5.0 mg Se/kg. Se content in blood and liver, liver panel tests, blood glucose, total antioxidant capacity (TAC), the activity of superoxide dismutase (SOD) and glutathione peroxidase (GPx) were analysed. Liver and duodenum were subjected to histopathology examination. The weight gain of rats showed no differences between tested groups. Se content in blood was higher in all treated groups compared to the control group. The liver concentration of Se in the treated groups varied in the range from 222 to 238 ng/g. No differences were observed in the activity of AST (aspartate aminotransferase), ALP (alkaline phosphatase) and TAS (total antioxidant status). A significant decrease in ALT activity compared to the control group was observed in the treated groups. GPx activity varied from 80 to 88 U/mL through tested groups. SOD activity in liver was decreased in the SeNP-treated group with 5 mg Se/kg (929 ± 103 U/mL). Histopathological examination showed damage to the liver parenchyma and intestinal epithelium in a dose-dependent manner. This study suggests that short-term SeNP supplementation can be safe and beneficial in Se deficiency or specific treatment.

Rumen Microorganisms Decrease Bioavailability of Inorganic Selenium Supplements

Despite the availability of selenium (Se)-enriched trace mineral supplements, we have observed low Se status in cattle and sheep offered traditional inorganic Se supplements. Reasons for this may include inadequate intake or low bioavailability of inorganic Se sources. The objective of this study was to determine whether rumen microorganisms (RMO) alter the bioavailability of Se sources commonly used in Se supplements. Rumen microorganisms were isolated from ewes (n = 4) and incubated ex vivo with no Se (control), with inorganic Na selenite or Na selenate, or with organic selenomethionine (SeMet). Total Se incorporated into RMO and the amount of elemental Se formed were determined under equivalent conditions. Incorporation of Se from Na selenite, Na selenate, or SeMet into RMO was measured as fold change compared with control (no added Se). Incorporation of Se into microbial mass was greater for SeMet (13.2-fold greater than no-Se control) compared with inorganic Se supplements (P = 0.02); no differences were observed between inorganic Na selenate (3.3-fold greater than no-Se control) and Na selenite (3.5-fold greater than no-Se control; P = 0.97). Formation of non-bioavailable, elemental Se was less for RMO incubated with SeMet compared with inorganic Se sources (P = 0.01); no differences were observed between Na selenate and Na selenite (P = 0.09). The clinical importance of these results is that the oral bioavailability of organic SeMet should be greater compared with inorganic Se sources because of greater RMO incorporation of Se and decreased formation of elemental Se by RMO.