Meta-analysis of the effect of oral selenium supplementation on milk selenium concentration in cattle

Abstract

Soils in many regions of the world have a low Se content. Consequently, forages and crops grown on these soils may provide inadequate dietary Se for humans and grazing animals. Selenium supplementation has been used to enhance Se status and milk Se concentration, but results conflict. Milk Se concentration appears to be a useful indicator of animal and herd Se status, and reflects the responsiveness to supplementation. A systematic review and meta-analysis were carried out to summarize all available scientific evidence for the effect of oral Se supplementation on milk Se concentration in cattle. The literature search was based on electronic and nonelectronic databases. Fixed- and random-effects models of meta-analysis were used, and a meta-regression was carried out to evaluate heterogeneity among studies. Random-effects meta-analysis was performed on 42 studies published between 1977 and 2007. Oral Se supplementation resulted in an average increase in milk Se content of 0.16 (95% confidence interval: 0.117, 0.207) micromol/L, with a significant heterogeneity among studies. Weak publication bias was evident, but it did not change the average effect. The continent where the study was performed, Se source, Se dose, and the interaction between source and dose explained 71% of the between-study variance. On average, American cows supplemented with Se yeast (e.g., 6 mg/h per day) had greater milk Se concentrations (approximately 0.37 micromol/L) 75 d after the beginning of supplementation when compared with those supplemented with inorganic forms of Se. This information provides a basis for tailoring daily animal requirements and for enhancing the Se intake of consumers of dairy products.

Effect of Selenium injection in pregnant camels on selenium status of their new-born and milk

“…In our results, the correlation was not significant (P=0.06), even if a tendency was observed. However, by comparing to the literature data in other dairy species (Ceballos et al, 2009;Davis et al, 2006), and in spite of the relative low Se status in serum, camel milk seems richer in selenium (Faye et al, 2011).…”

“…The selenium (Se) in milk was regularly investigated in cattle (Ceballos et al, 2009) or in ewe (Davis et al, 2006), but in camel, the references remain scarce. Previous studies were mainly limited to blood status and only 3 references are available on the selenium quantity transferred through milk to the camel calf (Al-Qarawi et al, 2001;Seboussi et al, 2009a;Faye et al, 2011).…”

Efeito da suplementação in vitro de selênio sobre neutrόfilos do leite e sanguíneos em vacas leiteras

“…Silvestre et al (2007) showed an improvement in blood neutrophils phagocytosis and killing activities in dairy cows supplemented with Se-yeast (an organic source of Se) compared with those given an inorganic source of Se. It should be noted that cattle supplemented with Se-yeast had an increase in serum and milk Se concentrations in comparison with those given sodium selenite (Weiss et al 2005, Ceballos et al 2009, Cortinas et al 2010) and also lower SCC and new cases of subclinical mastitis (Cortinas et al 2010). In face of, the improvement in the microbicidal activity of milk and blood PMNL even in dairy cows with a Se-adequate status, as encountered here, is probably one reason that explain the lower incidence of mastitis and also lower SCC described by others studies.…”

Selenium in Soil-Crop-Animal System: A Holistic Perspective to Manage Animal and Human Health

“…The response to supplementation of animal diets depends on the source and dose of Se [140]. Selenium can be supplied in animal diets either as the organic or inorganic form.…”