NCSU Extension Swine Husbandry 2003
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November, 2003 . Volume 26, Number 10

The Science of Odor



Animal agriculture contributes more than 55 percent of the total annual agricultural income in North Carolina. The basis for all of animal agriculture is a dynamic feed milling industry, which provides the nutrients essential for animal growth and reproduction. Sustainability of animal agriculture depends on efficient feed utilization and minimization of environmental impact. The College of Agriculture and Life Sciences (CALS) at North Carolina State University has embarked upon a Feed Milling Education Initiative to support this key agricultural sector. This initiative is designed to develop well-educated men and women for leadership roles in the feed milling industry and to provide the underlying educational and research programs required to support a sustainable industry.

General Perspective

The CALS Feed Milling Education Initiative has four components: academic program, feed mill educational unit, feed milling center and capital campaign. It is being planned as an integral part of the environmentally sound "mini-integration" involving present animal and crop production units at the Lake Wheeler Road Field Laboratory in Raleigh and other facilities and programs within the College of Agriculture and Life Sciences. It will serve as a teaching model of good natural resource stewardship practices combined with efficient, integrated, and sustainable animal agriculture. It also will use NC State's relationship with the adjacent Wake County Ecological Park to better educate the general public about the compatibility of agriculture and the environment.

Development of an Academic Program in Feed Milling

Establishment of a new degree program within the University of North Carolina system is a difficult and lengthy process. A logical way to proceed is to first develop a minor that could be used by students to receive academic training and certification in the specific topical area of feed milling. Development of the minor required the identification of courses that were presently being taught that could be applied to the topical area. In the case of feed milling there were a number of courses available that had direct applicability. In addition, there has recently been developed a general survey course in feed milling that can serve as the initial core course. Collectively these courses will serve as the basic preparation for an actual feed milling work experience that can be structured within an External Learning Experience summer internship.

It is anticipated that a number of commercial feed mills will cooperate with CALS to provide these summer work experiences for our students. In the longer term, it is envisioned that interested feed milling enterprises may create full-time positions that can be filled on a rotating basis by co-op students. The minor was approved effective Fall Semester 2001. This action demonstrates the academic commitment to the CALS Feed Milling Education Initiative. The program will be jointly operated by the Departments of Animal Science, Biological and Agricultural Engineering, and Poultry Science.

The academic objectives of the inter-departmental minor in feed milling are:

  1. To acquire an understanding of the functions of a modern feed mill.
  2. To learn the procedures to assist in operating a modern feed mill.
  3. To learn to apply academic skills to the challenges of running a manufacturing facility.

One weakness of the minor approach is the relatively low number of credit hours required. However, a record of successful placement of graduates from the feed milling minor in jobs with feed milling enterprises at competitive salaries will provide the justification for an evolution in the direction of a feed milling "concentration" that will require a greater number of credit hours. This will be equivalent to a major in terms of credit hours and will ensure that students are exposed to a more complete program. Further, at least two more courses in feed milling will be needed along with a revision of present courses to adequately cover required materials. This will require the addition of a new faculty member specifically educated in the feed milling area to provide leadership to the CALS Feed Milling Education Initiative. The scope of the responsibilities of the faculty position will depend on the feed mill facilities that can be developed. Industry support for this initiative would facilitate the timely development of this program and the hiring of this new faculty member.

Benefits and Educational Impacts

The CALS Feed Mill Educational Unit and overall Initiative will yield several benefits. It will provide animal researchers, teachers, and extension specialists with a state-of-the-art facility within which to manufacture modern feeds for animals, thus immediately positioning the College of Agriculture and Life Sciences as a leader in animal feed milling and nutrition research and education. This will help attract the best undergraduate and graduate students, faculty, and industry collaborators to CALS educational programs. The facility will provide the backbone of an educational program designed to produce college graduates who are competent in feed mill management. Moreover, this facility will allow CALS to utilize fully and efficiently its current animal research space and facilities and will help maintain the diverse agricultural industry that has tremendous economic impact in all areas of our state.

During harvest of the more than 60 agricultural commodities grown in North Carolina, significant byproducts can be produced that have presently undeveloped economic use in animal feeds. The facility also will encourage the current industry trend toward precision nutrition that meets the nutritional requirements of animals while minimizing environmental impact. It will be operated in a manner that will allow educational programs for industry clientele to be held within the milling facility. This will provide the basis for continuing education programs as well as certificate and degree programs for industry clientele. NC State University and CALS educational programs will derive a special advantgage because all of the normal monogastric feeds manufactured in North Carolina will be made in the facility on a weekly basis. A cover story in a recent issue of Feed Management magazine shows that there is a recognized need for this educational program.

Feed Mill Educational Unit Facility Design and Features

  • The facility will include all of the normal components of a commercial feed mill plus special facilities for special projects that require identity preservation of ingredients and/or feed.
  • Quality assurance and quality control testing of ingredients and feeds produced will be an integral part of the overall mill arrangement. Quality control procedures (i.e., ingredient and finished feed sampling, sample storage, sample testing) and regulatory compliance programs will need to be utilized in the day-to-day feed production processes and demonstrated in the teaching programs.
  • The milling processes involved will be subject to either semi-automation or manual operation, so that the teaching and/or research programs can utilize or demonstrate the unique aspects of each part of the system or of the system as a whole.
  • Ruminants can utilize a number of coproduct feedstuffs developed from animal and other agricultural byproducts. The basic feed mill, however, will not be designed to handle very bulky types of feed, such as fodder, hay, silages, etc., but will be able to produce premixes and concentrates designed to be mixed with bulky or wet feeds in adjacent CALS facilities.
  • The design will allow groups of students or clientele to participate in each educational exercise.
  • The mill design will incorporate both a small-batch pilot facility and a main production facility with two pellet lines to accommodate the wide batch size range required.
  • The physical plant for the mill will provide enough flexibility and room to allow upgrading of the equipment and the testing of new and experimental equipment and processes.
  • Utility connections for the major equipment items will have usage monitoring incorporated into the design so that economic evaluations can be made for various processing techniques.
  • Safety and health will be a major consideration in design, operation, and instruction.
  • The facility will be capable of dispensing feeds into bags, bulk boxes, bulk bags, and bulk trucks.
  • A unique split-level design with an upper Ingredient Level and lower Process Pit will position access to most operations at or below a floor level to facilitate operations and instructional activities.

Present Status of Construction of the Feed Mill Educational Unit

Initial funding came from a 1997 Legislative appropriation as well as the 2001 bond referendum. Contractors were hired for construction of the buildings and site work. The basic structures were completed in mid 2003. Local millwrights will be hired to install university-purchased and/or industry-donated equipment when all of the required materials have been assembled. This overall strategy will require a longer period of construction than a turn-key job but will ensure that qualified contractors are responsible for the specialized as well as general requirements of this unique facility at the lowest possible cost.

Equipment Required for the Feed Mill Educational Unit

Equipment like hammermills, mixers, and bagging systems must be either purchased or donated and installed in order to meet the projected educational mission of the Feed Mill Educational Unit. This is within the scope of the Capital Campaign.

Feed Milling Center

A Feed Milling Center concept is currently under development within the University of North Carolina system and will have dues-paying members who comprise the Board of Directors. There are full members and associate members of the center, based on the level of dues that are contributed. Full members make the decisions as to where member fees are spent to support educational and research initiatives. Full members share in semi-exclusive licenses to any new intellectual property as well. In the case of the Feed Milling Center, it is envisioned that there will be academic, extension education, and research initiatives that will involve issues such as new coursework, extension educational programs and workshops, and investigations of optimum feed milling practices. Members of the center will have timely access to information about students in the program and will also serve on the Advisory Board for the overall Feed Milling Educational Initiative.

Feed Milling Education Initiative Capital Campaign

To support the successful development of the Feed Milling Education Initiative a Capital Campaign with a goal of raising $2 million in cash and equipment will be conducted over the three-year period from 2003-2006. Companies and individuals may make three-year pledges of cash donations or equipment through the North Carolina Agricultural Foundation, which has pledged to match the first $750,000 of contributions from industry with $250,000. Companies that make contributions qualifying for the Platinum recognition level will be invited to have representation on the Advisory Board for the overall CALS Feed Mill Educational Initiative and to participate in the Feed Milling Center without charge for a limited time (to be determined). This Charter Membership will become effective when the Center is approved by the UNC General Administration.

For further information contact:

CALS Feed Milling Education Initiative
c/o Dr. John T. Brake
NC State University
Campus Box 7608
Raleigh, NC 27695-7608
Voice: 919-515-5060
Fax: 919-515-2625


Omega-3 fatty acids have received considerable attention in recent years in both human and pet nutrition. Infant formulas are now supplemented with such fatty acids for stimulating brain development. Pet foods also contain various ratios of omega-3 and omega-6 fatty acids to aid, among other things, in maintaining a healthy immune system.

In sow nutrition, though, little attention has been paid to these fatty acids. NRC (1998) has recommended levels for omega-3 fatty acids, but concludes that typical diets contain adequate levels of these fatty acids.

At the 64th Minnesota Nutrition Conference of 2003, John Rooke of the Scottish Agricultural College provided an overview of data on the use of omega-3 fatty acids in sow diets. The following is a summary of his proceedings:

Omega-3 fatty acids include linolenic (18:3 n-3), eicosapentanoic (20:5 n-3), and docosahexaenoic acid (22:6 n-3). Omega-6 fatty acids include linoleic (18:2 n-6) and arachidonic acid (20:4 n-6). The numbers in parentheses, e.g., 18:3 n-3, refer to the number of carbons in the fatty acids (18), the number of double bonds (3), and the starting position of the double bonds (n-3 refers ot the third carbon from the tail of the fatty acid, also referred to as omega-3 [omega is the last atom, minus 3]).

Figure. Docosohexaenoic acid or 22:6 n-3.

Typically, the 18 carbon varieties are found in the diet, and from these longer-chain acids and other products are produced that have profound biological effects. Although linolenic and linoleic acids require the same enzymes for conversion into longer-chain essential fatty acids, omega-3 and omega-6 fatty acids cannot be inter-converted. The first limiting enzyme in this pathway is delta-6 desaturase. Implications of the use of the same sets of enzymes are (1) the original rate of omega-3/omega-6 fatty acids largely determines the ratio of end products produced, and (2) competition exists between very long (24 carbon) and long-chain (18 carbon) fatty acids for these enzymes, which may compromise the production of very long-chain omega fatty acids. These pathways are not present in the fetus, implying that the unborn piglet is dependent on maternal supplies.

These fatty acids play an important role in cell membranes. Deficiencies can lead to changes in brain function, impaired vision, and the fertility of sperm. These fatty acids also are the precursors for prostaglandins and eicosanoid mediators, which play an important role in reproduction and immunity. New research also suggest that these compounds play a role in gene expression, through which route liver function is affected.

Cereal-based swine diets are typically low in omega-3 fatty acids and relatively high in omega-6, leading to ratios of 1:10 or higher (Table 1). In human nutrition, such ratios are considered imbalanced. To correct these ratios, products like flaxseed oil, fish-oil (especially tuna oil), or products derived from these sources can be used.

Table 1. Omega-6 and omega-3 fatty acid content of common feed ingredients (percent of total fatty acids).

18:2 n-6 18:3 n-3 n-6/n-3 ration
Corn 50.5 0.9 50
Wheat 56.3 3.7 15
Soybean meal 51.5 7.3 7.1
Flaxseed 15.0 53.1 0.3

Few studies have (properly) evaluated the effects of omega-3 and omega-6 fatty acids on embryonic and fetal survival in swine. Rooke quoted a study by Rigau et al. (1995), which showed an improvement in live fetuses, relative to corpora lutea, of 68 vs. 63% due to feeding menhaden oil. Webel et al. (2003) supplemented diets with n-3 fatty acids throughout lactation to 7 days postweaning, and they observed a significant increase in pigs born alive in the subsequent litter (10.8 vs. 10.3).

Rooke focused his research on improving piglet survival through impacting brain development in utero. His research showed that by supplementing omega-3 fatty acids starting at day 60 of gestation, the fatty acid content in the brain and the retina could be altered. This effect was much stronger with orbital (tuna) oil containing mainly 22:6 n-3 than with flaxseed oil containing mainly 18:3 n-3. The optimum dose of flaxseed oil was found to be around 6 g/sow/day of 20:5 n-3 and 22:6 n03 together; too high a dose had negative effects on brain development.

From a production standpoint, brain development does not seem a very important parameter. However, Rooke observed in his studies that piglets from sows supplemented with marine oils were more active after birth, exhibited more udder-seeking behavior, and, most importantly, were heavier at weaning. He thus pursued the issue by evaluating effects on reproductive performance in a large-scale trial. Sows were either fed a diet containing vegetable oil or salmon oil (16.5 g/kg feed, with approximately 100 sows per treatment). This trial showed that the supplementation resulted in longer gestation lengths, slightly smaller pigs at birth, but also lower pre-weaning mortality (Table 2). The reduction in mortality was due to a reduction in crushing and starvation, in line with the observations of Rooke that treated piglets were more eager to nurse. Weaning weight was not affected by treatment.

Table 2. Reproductive performance as affected by fatty acids.

Vegetable Oil Salmon Oil P value
Gestation length, d 115.4 115.9 < 0.001
Total born/litter 11.8 11.6 NS
Birth weight/pig, kg 1.54 1.47 < 0.05
Litter birth weight, kg 18.0 17.7 < 0.10
Preweaning mortality, % 11.7 10.2 < 0.05

In a more recent study, feeding 22:6 n-3 from an algal source during gestation tended to reduce pre-weaning mortality and improve pre-weaning weight gains. Feeding 22:6 n-3 during lactation also increased weaning weights. Baidoo et al. (2003) also showed that supplementing sows during gestation and lactation with flaxseed oil (at 5 percent) resulted in larger litters, heavier piglets at birth and at weaning, and lower pre-weaning mortality.

The data obtained are an indication that reproductive performance may be improved by altering the ratio of omega-3 to omega-6 fatty acids. The data, though, are not yet clear on the inclusion level, on the type of fat that should be used, or on the economics.

—Theo Van Kempen

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Last modified October 23, 2003.