Quality, nutrient and sensory characteristics of aged meat from lambs supplemented with selenomethionine.

Selenium (Se) as a co-factor of antioxidant enzymes is metabolically essential for animals. Its presence in muscle can improve the oxidative stability of meat and is a desirable nutrient for consumers. A novel approach to Se supplementation for meat-producing livestock was demonstrated in a 95-day study of young lambs. DL-selenomethionine (SeMet) was administered by subcutaneous injection at day 0 (3-4 weeks of age) and again at day 54. A Control group (n = 9) received carrier only, whilst Medium and High groups (n = 10) received graded levels of Se. Physicochemical attributes of meat quality and sensory characteristics were measured at 1, 3, 14 and 42 days of ageing (vacuum packaged at -1.5 °C), followed by instrumental colour measurements after 7 days of simulated retail display. There were no significant interactions between SeMet treatment and ageing. Muscle pH, drip and cooking losses, initial display colour and sensory evaluations by trained and consumer panels were unaffected by treatment. Smaller changes in colour during display were observed for the Medium group compared to Control (P < 0.05). The shorter range of ageing times improved meat tenderness however extended ageing decreased colour stability. SeMet markedly increased Se concentrations in muscle, blood, kidney and liver (P < 0.05), resulting in Se enriched meat without appreciable changes in meat quality.

Selenomethionine as a Safer Substitute for Barium Selenate in Long-Acting Injectable Se Supplements for Food-Producing Animals.

Nutritional supplementation with selenium (Se) can prevent Se deficiency in food-producing animals. Injection with slow-release formulations is a preferred method for free-range grazing sheep and cattle, and barium selenate (BaSeO4) provides optimal efficacy. This chemical can become a health risk to humans if the concentrated depot of an injection site is consumed, and consequently such use is recently banned in the EU. A possible replacement is selenomethionine (SeMet), a naturally occurring form of Se supplementation hitherto only administered orally. In four animal studies we found that injection with SeMet maintained nutritionally adequate concentrations of Se in blood and tissues of lambs for at least 191 days and in blood and milk of dairy cows for at least 95 days. Stereoisomer forms L- and DL-SeMet were functionally equivalent. This is the first demonstration that injectable SeMet can deliver efficacy similar to BaSeO4 but with less risk of undesirable residues in edible tissues.

Trace element supplementation of livestock in new zealand: meeting the challenges of free-range grazing systems.

Managing the mineral nutrition of free-range grazing livestock can be challenging. On farms where grazing animals are infrequently yarded, there are limited opportunities to administer trace element supplements via feeds and concentrates. In New Zealand, where the majority of sheep, cattle, and deer graze pasture year round, inadequate intake of cobalt, copper, iodine and selenium is prevalent. Scientists and farmers have developed efficient strategies to monitor and treat these dietary deficiencies. Supplementation methods suited to grazing livestock include long-acting injections, slow-release intraruminal boluses, trace element-amended fertilisers, and reticulated water supplies on dairy farms.

Pasture soils contaminated with fertilizer-derived cadmium and fluorine: livestock effects.

Fertilizers are indispensable for ensuring sustainability of agricultural production, thereby achieving food and fiber security. Nitrogen, sulfur, and potassium fertilizers are relatively free of impurities, but phosphorus (P) fertilizers, the main fertilizer input for the economic production of legume-based pastures, contain several contaminants, of which F and Cd are considered to be of most concern because they have potentially harmful effects on soil quality, livestock health, and food safety. Incidences of fluorosis in grazing livestock, and accumulation of Cd in the edible offal products of livestock, above the maximum permissible concentration set by food authorities have been reported in many countries. The majority of Cd and F applied to pastures in many countries continues to accumulate in the biologically active topsoil due to strong adsorption to soil constituents. However, the rate of Cd accumulation in the last decade has slowed as a result of selective use of low-Cd fertilizers. Cd and F adsorption in soils increase with increased contents of iron and aluminium oxides, layer silicates and allophane in soils, and increased soil pH. Cadmium adsorption also increases with increased Mn oxides and organic matter in soil. However, some Cd will be released during decomposition of plant and animal remains and organic matter. In most pastoral soils the majority of Cd and F added in fertilizers remains in the topsoil and little moves below 20-30 cm, and therefore these are unlikely to contaminate groundwater. However, F may pose a risk to shallow groundwater in very acidic low-P-fixing soils, and Cd may pose a risk in very acidic soils containing low organic matter and clay contents, or in soils with high chloride concentrations. Research is required both to test whether groundwater beneath farms with long histories of P fertilizer use is contaminated by these elements and also to examine their mechanisms of movement. Cd intake by grazing livestock occurs mostly by ingestion of pasture, and therefore measures to decrease plant availability of Cd in soils (e.g., maintaining high organic matter, reducing soil acidity and salinity, alleviating zinc deficiency, reducing weed) can reduce Cd accumulation in livestock. F intake by grazing livestock is mostly by soil ingestion; therefore, reducing soil ingestion by maintaining good pasture cover especially during winter periods can reduce F accumulation in livestock. In grazing livestock, Cd accumulates in kidney and liver, whereas F accumulates mainly in bones. Very little research has been carried out to study the effects of sustained but low levels of Cd and F additions on soil microbial activity, especially on the economically important N-fixers in symbiosis with pasture legumes and mycorrhizae. This subject also needs to be researched. The impact of F accumulation in bones of animals as influenced by the alternative low and high soil F intake between seasons and the effect of increasing age of animals needs further study to more accurately determine the potential risk of fluorosis and elucidate potential solutions to minimize F accumulation in bones and teeth of aged breeding stock. Computer-based models are required to identify farming systems that present a high risk of Cd concentrations in edible offal exceeding the MPC and livestock at risk of chronic fluorosis. A decision support model of this kind may be useful in developing management strategies capable of reducing Cd and F accumulation in animals. Preliminary empirical models have been developed for Cd (Loganathan et al. 1999) and F (Bretherton et al. 2002) accumulation in sheep grazing New Zealand pastures. Further development of these models is required for their wider applicability.