Comparisons of Selenite and Selenium Yeast Feed Supplements on Se‐incorporation, Mastitis and Leucocyte Function in Se‐deficient Dairy Cows

Abstract

Summary The dairy cows at the Estonian Agricultural University appeared to have an extremely low selenium status. The selenium level was 5.6 μg/l in whole blood and 3.2 μg/l in milk, on average. The blood glutathione peroxidase was consequently extremely low. The effects of organic selenium (selenized yeast) and sodium selenite were compared in a feeding experiment on 100 dairy cows. Selenium incorporation, udder health and the in vitro function of blood neutrophils were monitored. Supplementation of the feed either with 0.2 ppm organic selenium or sodium selenite for 8 weeks, increased the blood selenium level (geometric mean) within this period from the background level (about 5.6 μg/l) to 167 (Se‐yeast) and to 91 μg/l (selenite). The respective change in whole blood glutathione peroxidase (GSH‐PX) was from 0.22 to 3.0 (Se‐yeast) and to 2.3 (selenite) μKat/g Hb. Blood GSH‐PX continued to increase up to 10 weeks after the supplementation was stopped. The bioavailability of yeast selenium was superior to selenite: the relative bioavailability (selenite = 1) of yeast selenium was 1.4 if blood GSH‐PX, 1.9 if blood selenium, and 2.7 if milk selenium was used as the response criterion. Selenium‐supplementation showed a positive effect on udder health. The percentage of quarters harbouring mastitis pathogens dropped from 22.9 to 13.0 in the Se‐yeast group and from 18.4 to 7.4 in the selenite group during the supplementation period. The effect of selenium on mastitis was also reflected as a decrease in the output of milk somatic cells and N‐acetyl‐β‐D‐glucosaminidase (NAGase). The time‐luminescence profile of zymosan‐induced activity of blood neutrophils became skewed to the left in Se‐supplemented cows.

Fontes orgânicas e inorgânicas de selênio na nutrição de vacas leiteiras: digestão, absorção, metabolismo e exigências

“…Situações de deficiência de Se têm sido identificadas a campo pela medida de concentração do elemento no solo, nos alimentos, no sangue e no leite dos animais (LUCCI et al, 1984a;LUCCI et al, 1984b;WEISS et al, 1990;MALBE et al, 1995). Apesar de ser indicativa, a medida do Se total não permite que se faça diferença entre selenoproteínas funcionais e não-funcionais presentes em uma amostra de alimento, sangue ou leite.…”

“…De qualquer maneira, esses estudos têm demonstrado uma maior eficiência de formas orgânicas do Se em aumentar a concentração de Se no sangue e leite de vacas, se comparado às inorgânicas (Tabela 1). Contudo, maior concentração destas formas nas dietas de vacas em lactação de alta produção também implica maiores perdas através da excreção de Se pela glândula mamária, através da caseína e de outras proteínas do leite, que incorporam aleatoriamente SeMet da dieta (MALBE et al, 1995;ORTMAN & PEHRSON, 1997;KNOWLES et al, 1999;MUÑIZ-NAVEIRO et al, 2005). Nesta situação, a proporção que sobra para o animal suprir suas exigências por Se, ou seja, para manter ativas e em normal funcionamento as selenoproteínas funcionais, não é conhecida.…”

“…Em algumas situações, pode ser vantajoso aumentar a quantidade total de Se através da suplementação de Se na forma orgânica (MALBE et al, 1995). No entanto, a incorporação indiscriminada de SeMet em selenoproteínas não-funcionais pode influenciar a função de proteínas que dependem da existência, por exemplo, de pontes de dissulfeto em sua estrutura.…”

Selenium levels of Estonians

“…Malbe et al (1995) showed that the Se levels of the cows were extremely low by studying the dairy cows of Estonian Agricultural University. The levels of Se were 5.6 mg/l in whole blood and 3.2 mg/l in milk.…”

The effect of selenium sources and supplementation on neutrophil functions in dairy cows

“…Several reports associated increased concentration of blood Se with decreased infection rates such as subclinical and clinical mastitis in cows (Jukola et al, 1996;Ranjan et al, 2005). Furthermore, several studies have revealed positive associations of Se supplementation with health conditions of the cow (Weiss et al, 1990;Malbe et al, 1995;Kommisrud et al, 2005). In addition, Se status of the mammary gland is a vital regulator of selenoprotein expression and activities in the gland (Bruzelius et al, 2007).…”