Elsevier

Meat Science

Volume 81, Issue 4, April 2009, Pages 678-685
Meat Science

Effects of selenium source and level of supplementation on the performance and meat quality of lambs

https://doi.org/10.1016/j.meatsci.2008.11.009Get rights and content

Abstract

Objective of this study was to evaluate the performance, the quality and oxidative stability of meat, the total Se and specific selenoamino-acids content of muscle of lambs that were fed diets supplemented from different Se sources and at different levels. Forty-eight Apennine lambs 30 day old (12.78 ± 0.94 kg) received, during a 63 day period, a total mixed ration (TMR) which was either Se unsupplemented (Control group - background only- 0.13 mg/kg Se) or supplemented with Na selenite (0.30 mg/kg Se as sodium selenite) or selenium enriched yeast (0.30 mg/kg and 0.45 mg/kg Se as Se-yeast).

Growth performance, feed to gain ratio, carcass and meat quality (pH, drip and cooking losses, colour, GSH-Px activity and chemical analysis) did not show any difference between the treatments. Meat colour and oxidative stability during 9 days of refrigerated storage were unaffected by dietary supplementation, suggesting that, at the levels of Se used in this experiment, dietary Se, even from an organic source, had limited potential for reducing lipid oxidation. Selenium supplementation raised the Se content in muscle (P < 0.001) with the greatest increase when Se-yeast was fed. Although selenite increased total Se, it did not influence total or specific selenoamino-acids in this tissue. On the contrary, Se-yeast supplementation led to an increase in muscle Se-methionine content. We conclude that Se supplementation can increase significantly muscle Se levels and produce, particularly when Se-yeast is fed, a source of Se enriched meat as Se-methionine.

Introduction

Selenium (Se), in the form of selenocysteine, is the central structural component of a number of specific enzymes, making it an essential trace element for both humans and animals. A number of selenoproteins with known functions have been identified to date and include five glutathione peroxidases (GSH-Px), two deiodinases (Köhrle, 1999), several thioredoxin reductases and selenophosphate synthetase (Behne & Kyriakopoulos, 2001).

The importance of Se is principally associated with its role as an essential part of the glutathione peroxidases (GSH-Px) which provide a defence against oxidative stress by catalyzing the reduction of organic hydroperoxides that react with the selenol group of selenocysteine (Hardy & Hardy, 2004). Consequently an adequate intake of Se is needed to decrease the risk of myopathy, immunodeficiency, cardiovascular disease, cancer and other selenium deficiency syndromes (Hartikainen, 2005). In animals, and particularly in lambs, selenium deficiency has been linked to a number of diseases, which include white muscle disease and suppression of immunity (Rock, Kincaid, & Carstens, 2001). In the Abruzzo region, as in others in Italy, the Se content of plants used in farm animal nutrition is generally low. Consequently health and performance of animals reared on mainly home-grown roughage and grains, which contain low concentrations of Se, may be affected as a consequence of nutritional deficiency.

To date, nutritional Se requirements for lambs have been given as 0.20 mg/kg for lambs growing at 150 g/d (NRC, 2007). Organic Se, in the form of selenomethionine is the predominant Se species in cereals and forage crops. Currently, sodium selenite is the commercial Se source used as a supplement in animal feeds. However, an organic source of Se derived from yeast (Saccharomyces cerevisiae), which contains a high concentration of Se-methionine, has now become commercially accessible following its approval as a feed additive in the USA (Federal Register, 2002) and more recently in the EEC (2006). This alternative source of Se has prompted new research to determine which form of Se supplement would be most efficacious for dietary purposes in farm animal nutrition.

Weiss (2005) indicated that true digestibility of Se from diets containing selenite averages about 50% in sheep, whilst that from Se-yeast would be about 66%. Furthermore, the uptake and assimilation of inorganic Se and Se-methionine are different; inorganic Se is exclusively used for the synthesis of seleno-enzymes and that which is not incorporated into functional enzymes is methylated and subsequently excreted from the body (Deagen, Butler, Beilstein, & Whanger, 1987). On the contrary, Se-methionine is readily incorporated non-specifically into body proteins in place of methionine (Behne, Kyriakopoulos, Scheid, & Gessner, 1991), hence serving as an endogenous Se pool (Rock et al., 2001). Several authors have reported on the correlation between Se content of tissues and muscle GSH-Px activity in a number of different species (cattle - Gatellier, Mercier, & Renerre, 2004; pigs - Daun, Johansson, Önning, & Åkesson, 2001; poultry - Daun & Åkesson, 2004). Thus, Se supplementation may improve the oxidative stability of meat products. However, the effects of organic Se source on the activity of GSH-Px and on the oxidative stability of meat are not well documented. In addition, results on the use of organic Se in the diets of ovine species, and in particular lambs, are limited and need to be developed.

Finally, recommended Se intakes for humans (55 μg/day for adults) are not currently achieved in the majority of European countries (Rayman, 2004, Thomson, 2004). Previous studies have shown that supplementing feed with inorganic Se increased Se concentration in edible tissues of calves (Pavlata et al., 2001, Walsh et al., 1993), lambs (Molnár, Macpherson, & Molnár, 1998), pigs (Goehring, Palmer, Olson, Libal, & Wahlstrom, 1984) and poultry (Leng et al., 2003). The use of organic Se as a possible means of enhancing meat Se content, particularly with selenoamino-acids, has not been largely studied. Concerning this specific subject, a new methodology including capillary HPLC and inductively coupled plasma collision cell mass spectrometry to assess Se-Met and Se-Cyst in serum (Encinar, Schaumlöffel, Ogra, & Lobinski, 2004) and edible tissues (Bierla et al., 2008) has recently been validated.

Therefore, the purpose of this investigation, which was undertaken on Italian light lambs, was to compare the effects of Se-yeast supplementation at different levels to those of an inorganic Se source on animal physical performance, muscle tissue Se concentration, meat quality and shelf-life. Furthermore, a particular purpose was to assess the Se-Met and Se-Cyst content in muscle of treated lambs.

Section snippets

Animals, housing and trial duration

The study was conducted on 48 Italian Apennine lambs. Animals were initially blocked by gender (equal numbers of males and females) and were enrolled at 30 ± 3 days of age with a mean live weight of 12.78 ± 0.94 kg. Animals were randomly allocated to one of four dietary treatments and housed in groups of four animals/pen with 3 pens/treatments. Each pen was bedded with straw and provided a lying area of 1 m2/head. Every pen was provided with fresh potable water in buckets that were cleaned and

Growth rate, feed intake and feed to gain ratio

Average live weight of the animals at completion of the trial was 23.3 ± 2.4 kg, which is consistent with the weight usually achieved by the Apennine breed at the end of its growing period (Lambertini, Morittu, Vignola, Zaghini, & Formigoni, 2005). Growing performance was not influenced by treatment nor were there differences between Se levels or sources. Mean growth rate (Table 3) was 166 ± 33 g/d, as was expected using the diet and calculated allowances used. As expected, a significant effect of

Discussion

Growth performance, feed intake and feed to gain ratio were not influenced either by Se source or level of supplementation. Control group lambs received 0.13 mg/kg DM of naturally occurring Se which was present in the feeds used. In all likelihood results indicate that the Se content of the control diet may have satisfied the requirements for Se of control group lambs. Johansson, Jacobbson, Luthman, and Lindh (1990) previously reported that Se supplementation is not likely to influence growth

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