Biofuel co-products as livestock feed - Opportunities and challenges

512Biofuel co-products as livestock feed – Opportunities and challengesand Kamra, 22). The bitter taste and variable compositionof neem seed cake and neem seed kernel cake, due to depulping,de-corticating and oil extracting, affect its value asa feed. In addition, crude fibre and CP are both affected bythe methods employed and degree of processing (Dutta,Panda and Kamra, 22).Abbeddou and Makkar (19) summarized the potentialfor detoxification of seed cakes from non-conventionalsources that could contribute protein for livestock.Azadirachta indica, the source of neem cake, after washingcan be used at up to 45 percent of the concentrate incalf diets, while other treatments for this product includemethanol, urea and alkali extraction. Ricinus communismeal cooked at 100 °C for 50 minutes could be addedas 15 percent of chick diets, and, with the addition of4 percent lime, included at 10 to 15 percent of the diet forsheep and beef cattle. HCN levels in Hevea brasiliensis mealcould be reduced by soaking in water to allow fermentation,but livestock trials have not as yet been conducted.Crambe abyssinica meal de-hulled and subjected to a heatcarbonatetreatment is acceptable to beef cattle, and canreplace up to two-thirds of the soybean meal in the diet.Pongamia pinnata meal after washing with water or alkalitreatment can be included at up to 13.5 percent of the concentratesin lamb diets. Brassica juncea has been selected asa break crop for cereal lands, particularly in hot areas andan extracted oilseed cake is available (Braid, 25).The benefits of lipid co-products are summarized byWiesman, Segman and Yarmolinsky (18), although many arealso available from the production of ethanol. The advantagesinclude acting as a source of vitamin E, required for manyessential functions in both humans and livestock includinggrowth and reproduction; as a source of carotenes,normally available to the grazing animal but lost whenforage is conserved as hay or silage; and providing phytosterols,important in reducing the absorption of cholesterol,thereby helping to reduce cardiovascular disease (squalenehas similar properties in this respect). They also have antiinflammatory,anti-bacterial, anti-ulcerative and anti-tumourproperties, and are beneficial to the immune system ofpiglets. Polyethenols are able to improve the efficiency ofprotein use in ruminants, reduce urea content of manure,inhibit bloat, and help combat sub-clinical helminth infections.Lecithins act as dust suppressors (dustiness has beenidentified as a constraint to intake by ruminants), emulsifiersand as a source of essential fatty acids (Wiesman, Segmanand Yarmolinsky, 18). The authors stress the need for thoroughtesting of these products obtained from biodieselproduction to avoid toxic compounds reaching humans andlivestock. Shurson et al. (10) stress the problems likely to beencountered from an excess of methanol in the diet andin particular the need to control intake of glycerine in pigsbecause of the slow rate of excretion of methanol.Nutritive value of biodiesel co-productsRuminantsThe two major co-products from the biodiesel process areprotein-rich cakes or meals, and glycerol. The cakes andmeals have long been major sources of CP in commerciallivestock and poultry production, the market being dominatedby soybean meal (Makkar, Kumar and Becker, 21).Glycerol, a glucose precursor, has traditionally been usedas a drench for dairy cows to combat ketosis, often shortlyafter calving, because it is rapidly fermentable within therumen and favours a decrease in the acetate-to-propionateratio (Kalscheur et al., 7). Increasing propionate benefitsthe supply of gluconeogenic substrate reaching the liver,and increasing butyrate encourages ruminal epithelial tissuegrowth, possibly leading to improved absorption ofnutrients (Kalscheur et al., 7). However, it can also be usedas a supplement for transition cows, or as a replacementfor maize at 10–12 percent of the diet, but its effect incausing a reduction in fibre digestibility is similar to that ofstarch (Kalscheur et al., 7). The authors recommend analysisof individual batches of feed rather than depending onbook values when formulating diets, and warn that someagricultural crops may not be ideal co-components in dietsbased on DG. For example, a combination of DDGS plusalfalfa hay results in a feed containing too much CP. Addingglycerine to the diet will favour a propionate-butyrate,rather than acetic, rumen fermentation, although this maybe affected by the level of glycerine and the composition ofthe rumen flora (Drouillard, 8). Young cattle fed glycerineearly in life and then fed a diet containing maize glutenfeed, which had a glycerol content of 4.9 percent in thefinishing period, have performed better than cattle fed thesame finishing diet but without the addition of glycerineat the earlier stage, suggesting that rumen adaptationto glycerine may have a relatively long carry-over period(Drouillard, 8).In Europe, rapeseed co-products are widely used incattle, pig and poultry diets (Hippenstiel et al., 11).Recommendations from Germany are available for dailyamounts of both rapeseed meal (solvent extracted) andrapeseed cake (mechanically extracted), which range from4 kg of rapeseed meal for a dairy cow (2 kg of rapeseedcake) to 0–100 g of the meal and 50–100 g of the cakefor laying hens (Hippenstiel et al., 11, especially Table 16).A safety quality assessment of rapeseed cake for cattle isrequired because variations in processing can affect thechemical composition, particularly that of crude fat andCP, making ration formulation using this product difficult.Rapeseed meal can completely replace soybean meal indairy cow rations, although there may be differences inintake of energy, rumen degradability and amino acidprofiles between the two sources (Hippenstiel et al., 11).Hippenstiel et al. (11) also comments on the use of glycer-