Biofuel co-products as livestock feed - Opportunities and challenges

Utilization of lipid co-products of the biofuel industry in livestock feed 315OHOHOHFIGURE 2Chemical structure of various carotenoidsSource: Arab, Steck-Scott and Bowen, 2001.TABLE 9Various types and composition of carotenes in palm oilCarotene type Part in general carotenes (g/100 g)Phytoene 1.27Cis-β-carotene 0.68Phytofluene 0.06β-carotene 56.02-carotene 35.16Cis--carotene 2.49-carotene 0.69γ-carotene 0.33-carotene 0.83Neurosporene 0.29β-zeacarotene 0.74-zeacarotene 0.23Lycopene 1.30Source: Puah et al., 2005.β−Caroteneα−CaroteneCryptoxantinare characterized by a linear poly-isoprene structure withconjugated double bonds either per se (as in lycopene,C 40 H 56 ) (Figure 2) or as derived by cyclization of the twoextremities, with oxidation (as in xanthophylls such as luteinand zeaxanthin, C 40 H 56 O 2 ) or without oxidation (carotenes,C 40 H 56 ) (Calderon et al., 2006; Noziere et al., 2006).Concentration of carotenes in crude palm oil is approximately640–700 ppm (Choo, 1994) and 0.25–3.6 ppm invirgin olive oil (Tanouti et al., 2011).Non-oxidized carotenes are known as general componentsof the carotenes fraction (Table 9).The β-carotene content of forages is reduced by suncuring,ensiling and storage, and is quite variable. Hence,green pasture is the most abundant natural source ofcarotenes for ruminants (Miller, 1968; Kalac and Mcdonald,1981).OHOHZeaxanthinLuteinLycopeneRuminants depend entirely on feed as their source ofcarotenoids, not being able to synthesize them de novo,but metabolize or convert them into other carotenoids.In sheep and goats, absorbed β-carotene is assumedto be almost entirely transformed into retinol (vitamin A)in the enterocytes. In contrast, in cattle, not all absorbedβ-carotene is transformed into retinol and thus β-caroteneis the main carotenoid present in their plasma, stored in tissuesand secreted in milk fat (Mora et al., 1999; Cardinaultet al., 2006; Lucas et al., 2008).A deficiency in retinol may cause xeropthalmia (anight blindness disease) and reduce reproductive efficiencyin dairy cows, through impaired ovarian functionand increased incidence of abortion (Wang et al., 1987;Haliloglu et al., 2002). Apart from having pro-vitamin Aproperties, β-carotene per se also plays an important role asantioxidant. Some positive effects of β-carotene on mammarygland health, rumen function, milk yield and immunityhave been reported (Hino, Andoha and Ohgi, 1993; DeOndarza and Engstorm, 2009a, b).Certain changes in the organoleptic characteristicsof meat and milk from ruminants fed on diets rich inβ-carotene were reported (Ellis et al., 2007). Some of themare most desired from the point of view of public health,consumer acceptability or preference on the one hand, andanimal producers and food manufacturers on the other.The augmented levels of β-carotene and vitamin A in milkas a consequence of supplying them in the ruminant diet,could be beneficial for the production of functional foods(i.e. butter, margarine) (Ellis et al., 2007). Additionally, theirabundancy in meat and milk can supply the nutritionalrequirements recommended for humans (Simmone, Greenand Bransby, 1996; De Ondarza, Wilson and Engstrom,2009.). It should be noted, though, that high levels ofβ-carotene and vitamin A were found to adversely affectthe fatty acid profile in intermuscular fat tissue and marblingdeposition (Siebert et al., 2000, 2006; Pyatt andBerger, 2005; Dikeman, 2007).PhytosterolsPlant sterols and stanols (their reduced form), also calledphytosterols and phytostanols, are natural constituentsof plants and are part of the triterpene family (Moreau,Whitaker and Hicks, 2002). They are non-nutritive compoundswhose chemical structure resembles that of cholesterol,a predominant sterol in animals (Figure 3). Phytosterolcontent ranges from 0.14 percent in olive oil to 1.6 percentin maize oil (Gul and Amar, 2006). In plants they areresponsible for the regulation of the fluidity and permeabilityof cell membranes, serve as substrates for the synthesisof numerous secondary plant metabolites, and act as biogenicprecursors of plant growth hormones and hormonalprecursors.