Biofuel co-products as livestock feed - Opportunities and challenges

316Biofuel co-products as livestock feed – Opportunities and challengesHOHOCholesterolβ − SitosterolSource: Awad and Fink, 2000.FIGURE 3Chemical structure of sterolsHOThe best dietary sources of phytosterols are unrefinedplant oils, seeds, nuts and legumes; in certain plants, suchas Amaranthus spp. or Butyrospermum parkii (shea buttertree), it can reach more than 10 percent. The predominantforms being β-sitosterol, campesterol and stigmasterol,followed by brassicasterol, avenasterols and ergosterol(the latter is a known precursor of vitamin D 3 , that isalso formed in fungi) (Tapiero, Townsend and Tew, 2003;Milovanovic, Banjac and Vucelic Radovic, 2009).Studies with animals and humans show that phytosterolsreduce the absorption of cholesterol, thus lowering its serumlevel and leading to a reduction in the risk of cardiovasculardiseases (Kamal-Eldin and Moazzami, 2009; Weingartner,Bohm and Laufs, 2009). In addition, they are considered tohave anti-inflammatory, anti-bacterial, anti-ulcerative andanti-tumor properties (Awad and Fink, 2000).Phytosterols supplied as immuno-modulators (commercializedas Inmunicin Maymoin, a product consistingprimarily of β-sitosterol) in the diet of pigs during the nurseryand finishing periods have been shown to fortify theimmune system (decrease mortality and percentage of culls)and improve average daily gain and feed efficiency (Fraileet al., 2009). Hence, it will be interesting to conduct trialsaiming to prove the same utility in ruminants.PolyphenolsPolyphenols are secondary metabolites of plants, known tobe involved in defence mechanisms and the survival of theplant in its environment (Manach et al., 2004). These compoundspossess characteristic aromatic rings (single, as insimple phenols, to several, as in flavonoides and condensedtannins) (Figure 4) attached to a hydroxyl group, which conferson the molecule part of its diverse biological activities(Singh, Bhat and Singh, 2003).HOCampesterolStigmasterolPolyphenols are present in a variety of plants utilized asimportant components of both human and animal diets.Polyphenols in vegetable oils are a complex mixture ofcompounds that include derivatives of hydroxybenzoic andhydroxycinnamic acids, as well as oleuropeins, coumarins,flavonoids and lignins (Kozlowska et al., 1990; Valavanidiset al., 2004).Polyphenols are usually soluble in basic media andalcohols, but they can present in plant oils at lowconcentrations. Concentration of polyphenols in virgin oliveoil may be from 63 mg/kg to 406.5 mg/kg (Tanouti et al.,2011). As a rule, they are dissolved in the dispersed waterphase. This phase is stable due to presence in oils of suchsubstances like lecithin and other phospholipids.The presence of polyphenols in the diet of ruminantsimproves the efficiency of protein degradability anddigestibility (except when the level of tannins is not monitoredcorrectly and reaches high levels), thus ameliorating feedconversion. It also reduces the concentration of ureaexcreted in cattle manure (Reed, 1995; Frutos et al., 2004).Additionally, polyphenols augment ruminant performanceby inhibiting bloat and reducing the incidence of subclinicalhelminth infections (O’Connell and Fox, 2001).As they possess potent antioxidant activity, theirdeposition in animal tissues and secretion in milk is mostlydesired, because it protects the lipid components in meatand milk products as well as providing dietary antioxidantsfor human consumption. In this manner, functional-healthyproducts are achieved (Weisburger et al., 2002; Priolo andVasta, 2007; Moñino et al., 2008; Cuchillo Hilario et al.,2010; Jordan et al., 2010).The prohibition on use of growth-promoting antibioticsin animal feeds (EU, 2003) and the constantly increasingdemand for organically produced milk and meat, haveprompted livestock producers to look for more acceptablealternatives (Wallace, 2004). In addition, some phenolicextracts have been demonstrated to inhibit hyperammonia-producingbacteria in the rumen and exertbeneficial effects on rumen fermentation (Flythe andKagan, 2010). They have also been shown to inhibitcertain pathogens, hence their potential role as naturaland less hazardous replacements for antibiotics (Wells,Berry and Varel, 2005).LecithinLecithin is primarily a natural mixture of phospholipids suchas phosphatidylcholine (PC), phosphatidylethanolamine(PE), phosphatidylserine (PS), phosphatidylinositol (PI) andphosphatidic acid (PA) (Figure 5), and which contains minorquantities of other water-soluble or hydratable components(glycolipids and oligosaccharides) (Pickard, 2005).Soybean is the predominant vegetable source of lecithindue to its availability, and the lecithin has outstanding func-