«Ruminal Fermentation and Utilization of Unconventional Feeds in Western Canada A. F. Mustafa Department of Animal Science Macdonald Campus of McGill ...»
Ruminal Fermentation and Utilization of Unconventional Feeds in Western
A. F. Mustafa
Department of Animal Science
Macdonald Campus of McGill University
Presented at Western Nutrition Conference in Edmonton 2002
Changes to agricultural policies and the introduction of new cash crops to western Canada has
made available many unconventional ingredients that can be used as ruminant feeds. Most
unconventional feeds are either crop residues or agro-industrial byproducts. Crop residues are high in fiber, low in nitrogen and of low digestibility. They include cereal and legume straws and stalks. Agro-industrial byproducts result from processing of crops such cereals (e.g. milling, alcohol fermentation), oilseeds, sugar beet, and citrus fruits. Developing feeding programs for ruminants based on unconventional feeds should take into accounts several problems that might be associated with these feeds. Several unconventional feeds are made of heterogeneous materials, which makes it difficult to obtain a uniform product. A second challenge is the fact that processing (e.g. grinding, pelleting, ammoniation) might be necessary for many unconventional feeds to improve animal performance. Proper utilization of unconventional feeds by ruminants will not only benefit the animal industry but will also increase the economic return of many cash crops in western Canada. The objective of this paper is to review the nutritional value of unconventional ruminant feeds, which are available in western Canada. Discussion will be limited to research data available in scientific publications.
Classification of Agro-industrial byproducts
Based on their nutrient content agro-industrial byproducts can be divided into:
1- Feeds high in fiber and low in nitrogen. These include milling byproducts such as oat hulls and pea hulls.
2- Feeds high in fiber and high in protein content. These include distillers’ and brewers’ grains and several oilseed meals.
3- Feeds low in fiber and high in protein. These include mainly oilseed meals 4- Feed low in fiber and low in protein. These are usually byproducts of food processing for human consumption and include products such as molasses and citrus pulps and potato peels.
Some agro-industrial byproducts such as screenings and feed grade cereal and legume seeds do not fit within any of the above groups. Byproducts, which result from cleaning of cereal grains and oilseed usually, contain high proportions of dust, chaff and weed seeds. Consequently they are high in ash and fiber contents. They also contain moderate levels of starch or fat depending of the source of the parent material. Feed grade peas and beans arehigh in starch and protein but low in fiber. Due to the great differences in chemical composition, the energy content of unconventional feed varies considerably among unconventional feeds (Table 1). Some of the chemical entities which affect energy content include ash, fat, neutral detergent fiber, lignin, and the amount of protein associated with neutral and acid detergent fiber Weiss et al. 1992).
Ensiled mint byproduct 54 2.4 Fenugreek hay 61 2.7 Fenugreek straw 49 2.2 Grain Screenings Screenings are byproducts result from cleaning of cereal grains, oilseeds or legume seeds. The potential of screenings as animals feeds has increased significantly in the last few years due to the elimination of transportation subsidy. Two main types of screenings are available in western Canada: grain screenings and canola screenings. The main energy source in grain screenings is non-structural carbohydrates while fat is the main energy source in canola screenings. Both types of screenings are high in neutral detergent fiber, however, due to their small particle size and the extensive processing prior to feeding they are low in effective fiber content.
Grain companies and seed cleaning plants are making grain screening a viable feed source for ruminants in western Canada. In Saskatchewan alone the grain industry produces 60,000 tonnes of grain screening per year. Grain screenings are usually defined as that portion of crop which remains after the grain has been cleaned and consists of whole and damaged grains, weed seeds, chaff, dirt and dust and other foreign materials. Grain screenings are usually divided into number one (contain more than 35% of parent materials), number two (contain over 15% of parent material) and refuse screenings (contain less than 15% of parent material).
Grain screens are highly variable and may contain various proportions of small whole grain kernels, cracked grain, grain dust, forage residue, small rocks, dirt and metal. Particle size of the screened grain may be a problem and should be closely monitored. In many instances, the grain screenings are 95% grain and very economical. The smaller the particle size, the greater the risk of acidosis. Grain screens should be limited to a maximum of 50% in growing diets and 25% to 30% in finishing diets.
Grain screenings are usually processed (grinding and pelleting) to enhance digestibility and to destroy weed seeds. Variations in chemical composition of grain screening pellets (GSP) were investigated by Marx et al (2000). The authors determined chemical composition of 18 loads of grain screening pellets collected over a two-year period (Table 2). Carbohydrate was the main component of GSP with starch constituting about 40% of the total carbohydrates. Grain screening pellets contained more soluble protein and non-protein nitrogen than barley. Neutral and acid detergent insoluble protein were also higher in GSP than barley. The authors found greater variations in fat and starch contents for GSP than for barley. However, CP of GSP was less variable than that of barley. One possible explanation is the fact that GSP are sold based on their protein content and therefore other ingredients may be added to keep protein level constant.
Grain screenings pellets are characterized by high ruminal protein (more than 80%) and starch (more than 90%, Table 2) degradability. Ruminal degradability of protein and starch of GSP are expected to be similar to those of barley. However, ruminal degradability of NDF should be higher in barley than GSP, mainly because of the higher acid detergent lignin content of GSP. A major difference in ruminal degradability between GSP and barley is the higher rate of protein and starch degradation of GSP. This is mainly due to their high soluble dry matter and starch content.
Pylot et al. (2000b) conducted an experiment to determine the feeding value of canola screenings for beef steers. Processed canola screenings were included to replace 25, 50, 75 and 100% of barley in the diets. The authors found that, despite a high fiber level, processed canola screenings is a poor source of effective fiber in finishing diets. Performance and cost of gain for steers fed processed canola screening up to 50% of the diet were comparable with those fed a conventional finishing diet consisting of 80% barley grain and 20% barley silage.
Feed Grade Legume Seeds The rapid increase in the production of legume seeds in western Canada is largely fueled by the food market. However, as production increases, more of legume seeds will be feed grade and made available as animal feeds. Legume seeds are excellent source of fermentable carbohydrates for ruminants. However, the expected high protein solubility may reduce the protein quality of feed grade legume seeds. Feed grade legume may include chickpeas, faba beans, beans, and lupins.
Chickpea is one of the most rapidly growing pulse crops in western Canada. The area under chickpea production in Saskatchewan has increased from 2400 hectares in 1996 to 460,000 hectares in 2001. Canada now is the fourth largest exporter of chickpea in the world market. As production increase, more chickpea that is not suitable for human consumption (i.e. feed grade), will be made available as animal feed. There are two commercial types of chickpeas, which differ in origin, seed color and size. The Desi type has a smaller seed size and a thicker seed coat than the Kabuli type. The two types of chickpeas also differ in their chemical composition with the Kabuli type having lower fiber, higher starch and higher fat content than the Desi type (Table 5). Protein content is similar in the two types of chickpea (average 22% DM basis) with more than 60% of total protein is buffer soluble. Neutral and acid detergent insoluble protein levels are low in both types of chickpeas.
Ruminal nutrient degradability of feed grade chickpeas was determined by Mustafa et al. (2000).
Results showed that both types of chickpeas are highly degraded in the rumen mainly due to their high in situ rapidly soluble fractions. Heat treatment (e.g. moist heating) can be used to reduce ruminal degradability of feed grade chickpea and therefore increase the amount of ruminal undegraded protein available for intestinal digestion (Mustafa et al. 2000). Data on the feeding value of feed grade chickpeas to dairy and beef cattle are limited. A study in the United States by Hadsell and Sommerfeldt (1988) showed that chickpeas can replace 100% of the concentrate dry matter of dairy cow rations in early lactation. However, based on feed efficiency and milk protein percentage, the optimum rate of dietary inclusion was closer to 50% than 100% of the concentrate. Feeding Desi or Kabuli chickpeas to pigs up to 30% of the diet had no detrimental effects on performance or carcass characteristics. However, the inclusion of feed grade chickpeas at that level during the growing stage appeared to depress performance relative to a soybean control diet (Mustafa et al. 2000).
Protein meals from unconventional oilseeds There is an increasing interest in growing and processing oilseeds that contain high levels of essential oils or fatty acids, which have health benefits for humans. Among these specialty crops, borage (Borago officinalis) and hemp (Cannabis sativa) are the most commonly grown in western Canada. Borage seed contains 32% oil, 24% gamma linolenic acid (GLA) and 3% erucic acid. Hemp seed contains 30-35% oil, 80% of which is polyunsaturated fatty acids. The predominant essential fatty acids in hemp seed are linoleic and linolenic acids; however, many others are also present including GLA. As with other oilseeds, mechanical or solvent extraction of hemp and borage seeds produces meals that are high in protein and low in fat content.
Ruminal degradability of borage and hemp meal is shown in Table 6. Results showed that hemp meal is a better source of ruminal undegraded protein than borage and canola meal, mainly because of its lower in situ soluble CP fraction and a slower rate of ruminal degradation. About 78% of hemp meal protein can escape ruminal degradation. This is compared with 40 and 47% of CP for borage and canola meal, respectively. Using an in vitro pepsin-pancreatin assay, Mustafa et al. (1999) showed that ruminal undegraded protein of hemp meal and borage meal is highly digestible in the small intestine. The authors found no difference in total tract digestibility between borage meal, hemp meal and canola meal (average 86% of CP).
Feeding trials with lambs and pigs showed that borage meal can be included in rations of growing lambs up to 18% of the diet dry matter with no adverse effects on intake or nutrient digestibilities. In pig diets, the inclusion of borage meal resulted in reduced intake and poor nutrient utilization especially for growing pigs.
Oat Milling Byproducts Oat milling to produce various products for human consumption has become an important economic activity in western Canada. Oat hulls are major byproduct of the oat milling industry, which constitute up to 25% of the oat grain weight. Oat hulls are very high in fiber content and their nutritive value for ruminants is greatly affected by fiber components particularly lignin (Table 7). Thompson et al. (2000) showed that in vitro dry matter disappearance of oat hulls obtained from ten different oat varieties is positively correlated with acid detergent lignin content. The vitro dry matter disappearance ranged between 68% (1.3% lignin) and 33% (7.7% lignin). Ruminal fiber degradability of high and low lignin oat hull varieties was determined relative to oat straw (Thompson et al. 2000). Ruminal degradability of fiber components was higher for the low lignin than for the high lignin oat hulls. Ruminal degradability of the low lignin oat hulls was similar to that of oat straw (Table 7)
Ammoniation is a chemical treatment, which is commonly used to improve the feeding value of poor quality crop residues. The response to ammoniation has two folds: an increase in digestibility due to partial breakdown of lignin-cellulose-hemicellulose linkages, and a greater feed intake due to the greater supply of ammonia to the rumen micro-organisms. Thompson et al. (2002) studied the effects of ammoniation (3 or 5% of dry weight) on the feeding value of oat hulls for steers. The authors found that ammoniation improve ruminal degradability of neutral and acid detergent fiber by 41 and 35%, respectively (Table 8). Steers fed ammomniated oat hulls consumed more dry matter and showed improved whole tract digestibility of neutral detergent fiber relative to steers fed untreated oat hulls. The authors found only marginal improvement in the nutritive value of oat hulls when level of ammoniation increased from 3 to 5%.
The positive responses to ammoniation in the study of Thompson et al. (2002) should not be expected for all crop residues and agro-industrial byproducts. In an earlier study, McKinnon et al. (1995) found no improvement in the feeding value of canola hull as a result of ammoniation.
There are evidences that the response of agricultural byproducts to ammoniation is highly dependent of their hemicellulose content. Agricultural byproducts originated from cereals and grasses (monocotyledons) with high levels of hemicellulose are more responsive to ammoniation than agricultural byproducts originated from legumes (dicotyledons) with low levels of hemicellulose.