The primary sources of energy in swine diets are cereal grains. Thus they are important constituents of pig diets. In addition to the whole grains, the processing of cereals for the human market yields by-products that are important as feed ingredients. Most of the cereals suitable for use in organic pig production belong to the grass family (Poaceae). Their seeds (grains) are high in carbohydrate and they are generally palatable and well-digested.
Nutrient composition can be quite variable, depending on differences in crop variety, fertilizer practices and growing, harvesting and storage conditions. Variability may be higher in organic grains than in conventional grains because of the fertilizer practices in organic grain production, but the data are inadequate at present. Cereal by-products tend to be more variable than the grains and therefore their use in swine diets may have to be limited to achieve consistency of the formulations.
The fibre in grains is contained mainly in the hull (husk) and can be variable, depending on the growing and harvesting conditions. This can affect the starch content of the seed and, as a consequence, the energy value.
The hull is quite resistant to digestion and also has a lowering effect on the digestibility of nutrients.
On a dry basis, the CP content ranges from about 100 to 160 g/kg and is often variable. The protein is low in important AA (lysine, methionine, threonine and tryptophan) in relation to the pig’s requirement. Grains also tend to be low in vitamins and minerals. Therefore, cereal grain-based diets must be supplemented with other ingredients to meet AA and micronutrient requirements. Yellow maize is the only cereal grain to contain vitamin A, owing to the presence of provitamins (mainly β-carotene). All grains are deficient in vitamins D and K, but supplementation with vitamin
K is not normally required unless normal intestinal synthesis is impaired in the animal. The ether extract (oil) in cereal grains is contained in the germ and varies from less than 20 g/kg (dry basis) in wheat to over 50 g/kg in oats. It is high in oleic and linoleic acids, which are unstable after the seed is ground. As a result, rancidity can develop quickly and result in reduced palatability of the feed or feed refusal.
The cereals in general are good sources of vitamin E and may supply the entire requirement for this vitamin, provided the grain is used quickly after processing to prevent the development of rancidity and off-flavour.
The oil of wheat germ is one of the best known natural sources of vitamin E, but is unstable. Of the principal B vitamins, the cereals are good sources of thiamin but they are low in riboflavin. Maize, oats and rye are much lower in niacin than are barley and wheat. Maize is also low in pantothenic acid and all grains are deficient in vitamin B12. All cereal grains, especially maize, are deficient in calcium. They contain much higher levels of phosphorus but much of the phosphorus is bound as phytate, which is largely unavailable to pigs. Also, phytate affects the availability of calcium and other minerals.
Plant breeders are aware of the phytate issue and are developing new cultivars of cereals with reduced phytate content. A barley cultivar with 75% reduction in phytate phosphorus was introduced in Canada in 2006.
Cereals generally supply enough magnesium, but insufficient levels of sodium and possibly potassium. None of the cereals contains high levels of trace minerals.
Thus feed grains meet part of the requirement for dietary nutrients.
Other feed components are needed to balance the diet completely.
Combining the grains and other ingredients into a final dietary mixture to meet the pig’s nutritional needs requires information about the nutrient content of each feedstuff and its suitability as a feed ingredient.
Maize, wheat, oats, barley and sorghum are the principal cereals, the whole grains of which are used for feed. Generally, maize and wheat are highest in energy value for pigs. Sorghum, barley, oats and rye are lower in energy. Some rye is used in pig feeding. Although it is similar to wheat in composition, it is less palatable than other grains and may contain ergot, a toxic fungus. Triticale, a hybrid of rye and wheat, is also being used for pig feeding in some countries. There do not appear to be any GM varieties of wheat, sorghum, barley or oats being grown, unlike the situation with maize: in the USA, for instance, substantial quantities of GM maize varieties developed with insect and herbicide resistance are being grown. Such bioengineered varieties are obviously unsuitable for organic pig production.
Average composition values of commonly used feeds are presented in the tables at the end of this chapter and can to be used as a guide in formulating diets for swine. However it is recommended that, where possible, chemical analysis of the grain or feed product is conducted prior to feeding, to determine more exactly its nutrient composition and quality.
Analyses for moisture, protein (and possibly lysine) and kernel weight are generally adequate for grains.
Several by-products of grain milling and processing are valuable ingredients for pig diets. The grain seed consists of an outer hull or bran fraction covering the endosperm fraction, which consists mainly of starch and some protein. At the base of the seed is the germ which contains most of the fat (oil), fat-soluble vitamins and minerals. Processing of grains for the human market usually involves removal of the starch, leaving the other fractions as animal feed. The composition of these by-products varies according to the process used. Grain screenings (cleanings) are used in conventional animal feeding. These contain broken and damaged grains, weed seeds, dust, etc. and probably do not meet the quality standards for organic pig diets.
Barley and by-products
Barley (Hordeumspp.) is grown more widely throughout the world than any other cereal. It is grown in regions of North America, Europe and Australia that are less well adapted to maize, typically where the growing season is relatively short and climatic conditions cool and dry. It is the major feed grain grown in Canada, mainly in the prairies. Barley is also a good rotation crop with wheat, tends to be higher-yielding, matures earlier, and is more resistant to drought and salinity problems. Barley is classified as six-row or two-row, depending on the physical arrangement of kernels on the plant.
Two-row varieties are adapted to drier climates and six-rowed cultivars to the wetter areas.
Traditionally the higher grades of barley have been used for malting and the lower grades for livestock feed. High-quality barley can be an excellent grain source for pig diets. It has been used for some time as the principal grain for pig feeding in the western areas of North America, the UK and many countries of Europe because of its better adaptation to climate and the firmer, leaner carcasses produced than with maize-based diets.
NUTRITIONAL FEATURES Barley is considered a medium-energy grain, lower in DE than maize. It contains more fibre than maize and less than oats, but the proportion of hull to kernel is variable, resulting in variable DE value. The protein content is higher than in maize and can range from about 90 to 160 g/kg. The AA profile is better than in maize and is closer to that of oats or wheat, and the bioavailability of EAA is high. Barley contains more phosphorus than other common cereal grains.
PIG DIETS Barley is more suitable in diets for sows and growing-finishing pigs than in diets for young pigs, because of its higher fibre content and lower DE value relative to maize. The lower DE value tends to result in poorer feed efficiency with barley-based diets. However this effect is minimized by fine grinding (600 to 700 µm) and pelleting of the diet, several studies having shown improvements in growth rate of 8–12% by pelleting (Newman and McGuire, 1985; Grahamet al., 1989). Barley with a kernel weight of 56.3 kg/hl
or less has been shown to respond better to pelleting than higher-quality barleys (Harroldet al., 1989).
The preferred particle size for use in pig diets is approximately 700 µm with a relatively small range of particle size to promote uniform mixing (Goodbandet al., 1997).
Lower-quality barley should be used in dry-sow diets. The increased fibre is beneficial in helping to produce gut-fill in these animals on a restricted feeding regimen and helps to develop gut capacity so that the animals are better able to consume the maximum amount of feed during lactation. In addition the diet can be fed in meal form during gestation, avoiding the expense of pelleting. Barley can be used in lactation diets, particularly during early lactation when fibre intake may be beneficial in avoiding constipation. If used later in lactation the diets should be supplemented with high-energy ingredients and the diet should preferably be pelleted. Barley-based diets are less popular than maize-based diets for growing-finishing pigs in hotter regions because of the higher fibre and resultant higher heat increment resulting from fermentation in the large intestine, which can lead to a decrease in feed intake and a reduction in growth rate.
Hull-less barley
NUTRITIONAL FEATURES Hull-less barley varieties have been developed in which the hull separates during threshing. These varieties contain more protein and less fibre than conventional barley, and theoretically should be superior in nutritive value to conventional barley.
PIG DIETS Several studies have failed to show improved growth performance over conventional barley in growing-finishing pigs, and attempts have been made to provide an explanation. Thacker (1999a) reported that the CP digestibility was 9.2% lower with hull-less barley diets than with conventional (hulled) barley diets. Thackeret al. (1988) compared hulled (Harrington) and hull-less (Scout) barley as a grain source for growing pigs and found no significant difference in daily gain (0.75 versus 0.74 kg) between the diets. However, feed efficiency with diets based on hull-less barley was significantly better than with hulled barley (3.13 versus 3.30). Carcass traits were not affected by diet. There was no significant difference in the digestibility of CP or energy between diets, although DM digestibility was slightly higher with the hull-less barley diet than with the hulled barley diet (80.6 versus 78.7%).
One possible explanation for the poorer feed efficiency with hull-less barley is a higher content ofβ-glucans in this grain. However, responses to additions ofβ-glucanases to diets based on regular barleys fed intact or after mechanical dehulling have not been consistent (Graham et al., 1989). The gut microflora of pigs appears able to hydrolyseβ-glucans. Heat processing of conventional or hull-less barley by micronization does not appear to improve utilization of the carbohydrate or protein fractions (Thacker,
1999a), although it increased the percentage of gelatinized starch in both hulled and hull-less barley diets. Diet viscosity also increased with micronization. The micronization process increased the digestibility of CP by 8.0% and GE by 4.4%. Digestibility of DM and energy was similar with both types of barley. Although micronization led to some improvements, it resulted in a significant reduction in feed intake. This led to a 14.3%
reduction in the growth rate of pigs fed the micronized barley-based diets.
Over the entire growth period (19–80 kg), pigs fed micronized diets gained weight 10.3% slower than pigs fed untreated barley. The slower growth appeared to be due, at least partially, to a 14.3% reduction in feed intake, which was attributed to an increase in diet viscosity.
These results suggest that hull-less barley can be used in organic pig diets as a substitute for conventional barley on the assumption that they are similar in nutritive value.
Brewer’s dried grains
Brewer’s dried grains (often referred to as spent grains) is the extracted dried residue of barley malt alone or in mixture with other cereal grain or grain products resulting from the manufacture of wort or beer. This by-product consists largely of structural carbohydrates (cellulose, hemicellulose) and the protein remaining after barley is malted and mashed to release sugars for brewing (Westendorf and Wohlt, 2002). Other grains may be added with the barley.
NUTRITIONAL FEATURES Because of the removal of sugars and starches, the spent grains are higher in CP and lower in energy than the original grain. The CP, oil and CF contents of brewer’s grains are approximately twice as high as in the original grain. According to recent data from Westendorf and Wohlt (2002), CP ranges from 210 to 290 g/kg on a DM basis (US data). Some recent data cited by these authors indicate a higher average CP content, 290 to 330 g/kg (DM basis). They speculated that the increase might be due to improved varieties of barley, maize and rice being used for brewing, different brewing methods, or changes in the recovery or pooling of wastes generated during the brewing process.
Other by-products of the brewing process are malt sprouts, brewer’s condensed solubles (produced from the mechanical dewatering of brewer’s grains) and brewer’s yeast. Most of the brewer’s grains is marketed in the wet form as a dairy cattle feed (Westendorf and Wohlt, 2002). However, some dried product may be available economically as a feed ingredient for pig diets.
North American definitions of the main by-products of brewing that are suitable for pig feeding are as follows:
• Brewer’s dried grainsare the dried extracted residue of barley malt alone or in mixture with other cereal grains or grain products resulting from the manufacture of wort or beer and may contain pulverized dried
spent hops in an amount not to exceed 3% evenly distributed: IFN 5-00-516 Barley brewer’s grains dehydrated.
• Malt sprouts are obtained from malted barley by the removal of the rootlets and sprouts which may include some of the malt hulls, other parts of malt, and foreign material unavoidably present. The traded product must contain not less than 24% CP. The term malt sprouts, when applied to a corresponding portion of other malted cereals, must be in a qualified form: i.e. ‘rye malt sprouts’, ‘wheat malt sprouts’, etc.
Malt sprouts are also known as malt culms in some countries: IFN 5-00-545 Barley malt sprouts dehydrated; IFN 5-04-048 Rye malt sprouts dehydrated; IFN 5-29-796 Wheat malt sprouts dehydrated.
• Malt cleaningsare obtained from the cleaning of malted barley or from the re-cleaning of malt that does not meet the minimum CP standard of malt sprouts. They must be designated and sold according to the CP content: IFN 5-00-544 Barley malt cleanings dehydrated.
• Brewer’s wet grains are the extracted residue resulting from the manufacture of wort from barley malt alone or in mixture with other cereal grains or grain products. The guaranteed analysis should include the maximum moisture content: IFN 5-00-517 Barley brewer’s grains wet.
• Brewer’s condensed solublesare obtained by condensing liquids resulting as by-products from manufacturing beer or wort. The traded product must contain not less than 20% total solids and 70% carbohydrates on a DM basis, and the guaranteed analysis must include maximum moisture content: IFN 5-12-239 Barley brewer’s solubles condensed.
• Brewer’s dried yeastis the dried, non-fermentative, non-extracted yeast of the botanical classificationSaccharomycesresulting as a by-product from the brewing of beer and ale. The traded product must contain not less than 35% CP. It must be labelled according to its CP content: IFN 7-05-527 Yeast brewer’s dehydrated.
PIG DIETS Brewer’s grains are commonly fed to farm livestock. Most of the brewer’s grains used in pig diets is in the dry form. According to Holden and Zimmerman (1991) dried brewer’s grains can make up a substantial portion of gestation diets, but should not be used as a component of starter diets and should be used only as a minor ingredient in lactation or growing-finishing diets. Walhstrom and Libal (1976) successfully used brewer’s dried grains up to 400 g/kg in the diet of gestating sows when the lysine level was maintained at 5 g/kg. There were no treatment differences in reproductive performance. Litter size and weight of individual piglets, litter weight at birth and weaning were not affected by treatment. Growing-finishing pigs have been fed diets containing dried brewer’s grains up to 230 g/kg without affecting growth rate, but feed conversion efficiency suffered incrementally with increasing level of dried brewer’s grains (Holden and Zimmerman, 1991).
Buckwheat (Fagopyrumspp.)
Buckwheat is a member of thePolygonaceaefamily and is most commonly grown for human consumption. The protein quality of buckwheat is considered to be the highest of the grains, being high in lysine. However, buckwheat is low in DE relative to other grains due to its high fibre and low oil contents. Another significant factor limiting the use of buckwheat in pig diets is the presence of an anti-nutritional factor, fagopyrin, which causes skin lesions and intense itching when pigs consuming buckwheat-based diets are exposed to sunlight. As a result, buckwheat is not recommended for inclusion in organic pig diets.
Maize (Zea mays)
This cereal is also known as corn or Indian corn in the Americas. It can be grown in more countries than any other grain crop because of its versatility.
It is the most important feed grain in the USA because of its palatability, high energy value and high yields of digestible nutrients per unit of land.
Consequently it is used as a yardstick in comparing other feed grains for pig feeding. The plains of the USA provide some of the best growing conditions for maize, making it the world’s top maize producer. Other major maize producers are China, Brazil, the EU, Mexico and Argentina.
NUTRITIONAL FEATURES Maize is high in carbohydrate, most of which is highly digestible starch, and low in fibre. It has relatively high oil content;
thus maize has a high DE value. Other grains, except wheat, have a lower DE value than maize. Maize oil has a high proportion of unsaturated fatty acids and is an excellent source of linoleic acid. The use of yellow maize grain should be restricted in pig diets if it results in carcass fat that is too soft or too yellow for the market in question. White maize can be used to avoid the fat coloration. Yellow and white maize are comparable in energy, protein and minerals, but yellow maize has more carotene than white maize. Yellow maize also contains the pigment cryptoxanthin, which can be converted into vitamin A in the animal’s body.
The protein concentration in maize is normally about 85 g/kg but the protein is not well balanced in AA content, with lysine, threonine, isoleucine and tryptophan being limiting. Varieties such as Opaque-2 and Floury-2 have improved AA profiles but do not appear to yield as well as conventional varieties. As a result they are not grown extensively. Producers wishing to use such varieties should check their acceptability with the organic certifying agency.
Maize is very low in calcium (about 0.2 g/kg). It contains a higher level of phosphorus (2.5–3.0 g/kg) but much of the phosphorus is bound in phytate form that it is poorly available to pigs. As a result a high proportion of the phosphorus passes through the gut and is excreted in the manure.
The diet may be supplemented with phytase enzyme to improve