Forms of selenium in vitamin-mineral mixes differentially affect serum alkaline phosphatase activity, and serum albumin and blood urea nitrogen concentrations, of steers grazing endophyte-infected tall fescue

Impact of live yeast and selenium supplementation on blood metabolites and rumen pH of young bulls after long-transport to the fattening unit

Long-distance transport and the receiving phase at the fattening unit are sources of stress for young beef cattle. This randomised controlled study involved 80 Charolais young bulls that underwent 12 h of transport from France to Italy and aimed at testing whether the animals have some benefits from the supplementation of live yeast and selenium through slow-release boluses and diet. The bulls were randomly allocated into two supplementation groups of 40 animals each, named Yeast and Control groups. Bulls of the Yeast group received a supplementation of Saccharomyces cerevisiae and selenium-enriched yeast (1.5 × 1010 CFU/bull per day of live yeast and 1.5 mg/bull per day of selenium) by two slow-release ruminal boluses 1 day before leaving France, and a live yeast supplemented diet once in Italy (8 × 109 CFU/bull per day of live yeast). Yeast and control bulls underwent the same manipulations. Individual BW and complete blood metabolic profile were assessed at the arrival to the Italian fattening unit (day 0), after 7 days (day 7), and at the end of the receiving phase (day 30). The rumen environment was continuously monitored through reticulum-rumen sensors that measured several parameters in a subsample of 60 bulls, equally distributed between Yeast and Control groups. Saccharomyces cerevisiae and selenium supplementation did not affect growth performance and metabolic profile. However, the supplementation stabilised the rumen environment by limiting the daily pH amplitude and SD and the inter-animal variability. The Yeast group increased the time spent ruminating (+39 min/day) at day 30 compared to Control group. More stable ruminal conditions are important to support beef cattle health during the receiving period at the fattening unit, when animals face the delicate transition to high-energy diets.

Trace Mineral Supplementation of Beef Cattle in Pasture Environments

The United States Department of Agriculture defines pastureland as "A land cover/use category of land managed primarily for the production of introduced forage plants for livestock grazing." The purpose of this article is to review trace mineral supplementation for beef cattle in this environment. Supplementation of trace minerals in these environments is accomplished with the use of a trace mineralized salt or a complete mineral-vitamin product that contains macrominerals, trace minerals, and vitamins. The form of the supplement may influence uptake and utilization. Supplementation may be augmented with pulse dosing with injectables or oral products.

Pituitary and liver selenoprotein transcriptome profiles of grazing steers and their sensitivity to the form of selenium in vitamin-mineral mixes

Many supplemental Se-dependent metabolic effects are mediated through the function of selenoproteins. The full complement and relative abundance of selenoproteins expressed by highly metabolic cattle tissues have not been characterized in cattle. The complement and number of selenoprotein mRNA transcripts expressed by the pituitary and liver of healthy growing beef steers (n = 7 to 8) was characterized using NanoString methodology (Study 1). Of the 25 known bovine selenoproteins, 24 (all but SELENOH) were expressed by the pituitary and 23 (all but SELENOH and SELENOV) by the liver. Transcript abundance ranged (P ≤ 0.05) over 5 orders of magnitude in the pituitary (> 10,000 for GPX3, < 10 for DIO1 and GPX2) and liver (> 35,000 for SELENOP, < 10 for DIO2). Also unknown is the sensitivity of the selenoprotein transcriptome to the form of supplemental Se. The effect of form of supplemental Se on the relative content of selenoprotein mRNA species in the pituitary and liver of steers grazing a Se-deficient (0.07 ppm Se) tall fescue pasture and consuming 85 g/d of a basal vitamin-mineral mix that contained 35 ppm Se as either ISe (n = 6), organically-bound Se (SELPLEX; OSe, n = 7 to 8), or a 1:1 blend of ISe and OSe (MIX, n = 7 to 8) was determined by RT-PCR after sequence-validating the 25 bovine selenoprotein cDNA products (Study 2). In the pituitary, Se form affected (P < 0.05) the relative content of 9 selenoprotein mRNAs and 2 selenoprotein P receptor mRNAs in a manner consistent with a greater capacity to manage against oxidative damage, maintain cellular redox balance, and have a better control of protein-folding in the pituitaries of OSe and MIX versus ISe steers. In the liver, expression of 5 selenoprotein mRNA was affected (P ≤ 0.05) in a manner consistent with MIX steers having greater redox signaling capacity and capacity to manage oxidative damage than ISe steers. We conclude that inclusion of 3 mg Se/d as OSe or MIX versus ISe, forms of supplemental Se in vitamin-mineral mixes alters the selenoprotein transcriptome in a beneficial manner in both the pituitary and liver of growing steers consuming toxic endophyte-infected tall fescue.