Feed and industrial uses for cereals

Kurt A. Rosentrater , A.D. Evers , in Kent's Technology of Cereals (Fifth Edition), 2018

13.2.1.1 Raw ingredient receipt

Feed mills receive incoming ingredients by both rail and truck (including hopper-bottom, bulk-solids and liquids trailers). Rail receiving hoppers should be designed to provide maximum capacity, but are usually relatively shallow, which constrains carrying volume. Rail and truck hoppers between 1000 and 1200  bu in capacity are common. Because feed-mill receiving pits are generally shallow, inbound material (from either rail or truck) will pass through choke-fed flow into the receiving hopper, which is actually an effective means of controlling dust and keeping it in the hopper car. Feed mills also commonly utilize truck and rail scales (for ingredient inventories) with flow-through floors, with the hopper pit and at least one screw conveyor underneath; these systems are housed within the same receiving structure, which can be of either steel or concrete construction (Fig. 13.6). Major constituents (such as cereal grains and soybean meal) and minor ingredients (such as lime, brewers' grains, wheat middlings, etc.) are received via these systems.

Figure 13.6. Plan and section views of a typical enclosed rail and truck scale hopper receiving system.

 Based upon Rosentrater, K.A., Williams, G.D., 2004. Design considerations for the construction and operation of feed milling facilities. Part II: process engineering considerations. In: 2004 ASAE/CSAE Annual International Meeting, Ottawa, ON, Canada, pp. 1–4.

Micro ingredients such as minerals, vitamins and other additives, on the other hand, are commonly delivered via bulk truck and then pneumatically conveyed to the appropriate storage bins. Pneumatic systems require blowers, delivery lines, receivers, filters and airlocks – typically one system for each ingredient to be received. It is essential to consider the terminal velocity of each ingredient to size the components of the system adequately. Generally, pneumatic transfer of ingredients requires air velocities between 4000 and 5000   ft/min. Additionally, some minor ingredients may sometimes be delivered via bulk tote bags, which will require a freight elevator (i.e., pallet hoist) in the mill structure to transport them to the batching floor.

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How does Sweden control Salmonella before it enters the food chain?

P. Häggblom , in Case Studies in Food Safety and Authenticity, 2012

23.3.2 Technical equipment in the feed mill

The feed mill was built as early as 1962, and certain areas had not been modified since then. Between 1999 and 2000 the feed mill was reconstructed and new equipment was installed, e.g. coolers for pelleted layer feed. The processing line for expanded pig feed was also reconstructed using old equipment (e.g. a modified cooler). The two production lines for pelleted feed and one expander line were separated after heat treatment, except for the storage bins for finished feed.

On the contaminated production line, pig feed concentrates and soybean meal were processed in an expander at 76   °C. After start-up, the mash was recirculated four to five times for up to 10 minutes before the correct temperature was reached and production could continue. This process was used intermittently where the temperature gradually approached ambient temperature. Evidence of previous technical problems in this production line was revealed during the investigation.

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Quality control of feed ingredients for aquaculture

B. Tangendjaja , in Feed and Feeding Practices in Aquaculture, 2015

6.10 Conclusions

Every feed mill should develop quality control system and the quality of feed would be very much influenced by quality ingredients received, therefore it is critical to select and monitor the incoming feed ingredients. Quality of ingredients, however, may vary depending upon the original materials, processing technique, storage, and contamination/adulteration. A quality control system should start from defining quality based on physical, chemical, and biological and developing standard specifications for each ingredient received. Quality control should use proper sampling systems and equipment and be supported by a laboratory. Adulteration or contamination can be problems in many developing countries, and the use of a quick method to detect possible adulteration can be performed using spot tests and feed microscopy techniques. Any ingredients that deviate from standard quality should be rejected or corrected. Monitoring of quality can be useful to evaluate consistency on feed production and evaluate suppliers. Depending upon the size of the feed mill, laboratory facilities should be developed and a service laboratory can be used for specific analyses. NIRS has become an important tool for quality measurement and is now widely adopted for a wide range of analyses and in-line quality control. However, bear in mind that the ultimate goal of feed quality control in a feed mill is to produce feed products of best quality in a consistent manner to serve customers for maximum profit. Each feedmill should develop quality control system suitable in their situation.

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Optimizing nutritional quality of aquafeeds

Karthik Masagounder , ... Girish Channarayapatna , in Aquafeed Formulation, 2016

6.2.3 Wet chemistry

Most feed mills have an analytical laboratory as a part of their quality control or assurance program and have the capacity to analyze proximate nutrients. Laboratories typically follow standard procedures, such as those described by Association of the Official Analytical Chemists, International (AOAC, International), American Oil Chemist Society (AOCS), and American Association of Cereal Chemists (AACC) for different nutrients and antinutritional factors. While this can be a golden standard for a feed mill, the quality of those data depends on the method adopted in analysis and the quality assurance program adopted by the laboratory. Quality assurance procedures to be practiced by the feed analysis laboratory can be referred from FAO manual ( FAO, 2011) which is based on ISO 17025:2005.

As a part of a quality control program, a feed mill should strictly follow procedures for validating the data for their accuracy and precision. Accuracy refers to the closeness of a measured value to a true or standard value, whereas precision indicates how close a group of analyzed values are to each other. Precision therefore refers to repeatability or reproducibility of a set of analyzed values and is determined by calculating the standard deviation or coefficient of variation. For testing accuracy, labs typically analyze pure standards for which the value is already known, and the accuracy is calculated based on % recovery from the actual value. Additionally, ring test (interlaboratory test) is also performed in order to cross-check the own values with those produced in a standard laboratory for the same sample. For example, external laboratories such as AAFCO (the Association of American Feed Control Officials, USA), BIPEA (Bureau Interprofessionnel d'Etudes Analytiques, France), and VDLUFA (Association of German Agricultural Analytic and Research Institutes, Germany) can be used for performing ring tests.

The downside of wet chemistry is that it is the most time-consuming and expensive method to obtain information about the nutrient profile of raw material and feed. Additionally, it requires highly trained laboratory technicians. Although feed mills have the capacity to analyze proximate nutrients based on wet chemistry, only very few are able to analyze amino acids. The other limiting factor is analytical laboratories can handle only a limited number of samples per day, which is a serious setback for a big feed mill that requires hundreds of samples to be processed every day.

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The ecology and control of bacterial pathogens in animal feed

W.Q. Alali , S.C. Ricke , in Animal Feed Contamination, 2012

3.2.2 Postharvest feed contamination

At the feed mill, animal feed can also become contaminated during feed manufacture or processing as a result of cross-contamination. The most critical point for microbial contamination at the mill is the post-processing heat treatment process. The heating process is required to pellet the feed and usually kills most of the pathogens in the produced feed, but inadequate operating temperatures for the pelleting equipment and feed conditioner are risk factors. Contamination of feed before and after the heating point is common and can be attributed to many factors within feed mill facilities. These include unclean receiving and unloading areas, unclean intake pits, dust generated by the feed ingredients, dirty conveyers with leftover feed from previous loads, inadequate feed storage conditions, and presence of non-employees or visitors in unsanitary clothes (Jones and Ricke, 1994; Jones and Richardson, 2004 ). Feed ingredients should be inspected prior to unloading for signs of rodent contamination, bird droppings or insect infestation. Inspection is particularly important given the difficulty of testing large amounts of incoming ingredients or of testing the feed during and after production due to the associated cost, time and labor. Therefore, feed mills should consider investigating which suppliers have consistently and reliably delivered ingredients without macro- or micro-levels of contamination. Furthermore, sampling plans designed to determine the minimum number of sampling units required to represent the microbiological quality of feed should be considered when needed.

In early studies, Hacking et al. (1978) detected Salmonella in 3% (n = 111) of pelleted feed sampled from one commercial poultry feed mill in Canada, whereas Cox et al. (1983) did not find Salmonella in pelleted poultry feed from 10 commercial feed mills in three southeastern US states. The latter authors detected Salmonella in mash feed (58%; n = 26) as well as in meat and bone meal samples (92%; n = 13). These data clearly indicate the level of reduction that can be achieved by feed processing, including the heating step. In the United Kingdom, nine feed mills that produced a variety of animal and poultry feeds were sampled over time for the presence of Salmonella (Davies and Wray, 1997). The authors found Salmonella not only in the finished products but also in feed mill equipment, including intake pits (24.1%) and the cooling systems (20.2%). Furthermore, Salmonella was isolated from fresh wild bird droppings collected from the intake pit areas, warehouses, and unloading areas. Jones and Richardson (2004) visited three feed mills and collected samples from raw ingredients, the mixer and pellet mill, pellet coolers and the finished product. The authors concluded that feed raw ingredients and dust were the main sources of feed mill contamination with Salmonella. They reported a Salmonella prevalence of 8.8% (n = 178) and 4.2% (n = 451) in mash and pelleted feed samples, respectively. A higher prevalence of Salmonella was observed in dust samples compared to the actual feed samples within each sampling area (Jones and Richardson, 2004).

In general, most of the studies reported earlier in this section have lacked a strong temporal component to assess both patterns of pathogen contamination over time (i.e., seasonality) and changes in microbial populations over time. Furthermore, epidemiological studies are needed to determine the relationship between potential risk factors at the feed mills that contribute to the prevalence and level of pathogen contaminants in the feed production process.

During transportation to the farms, feed is susceptible to the introduction of pathogens and subsequent survival and growth of the organisms. Unclean transportation containers, traces of previous contaminated feed in transportation trucks, and changes in temperature and humidity during transportation and/or storage are all risk factors for the introduction and survival or growth of pathogens in animal feed. Fedorka-Cray et al. (1997) isolated Salmonella from trucks transporting swine feed (0.7%, n = 549) and from feed samples taken from those trucks (23.5%, n = 17). The European Union (EU) Department for Environment Food and Rural Affairs (DEFRA), Code of Practice for the Control of Salmonella (2009) recommended that feed should be transported in vehicles and containers used to carry dry products to avoid any pre-existing moisture. Moreover, it was recommended that vehicles used to transport feed should be subjected to cleaning and sanitation to ensure no waste build-up and cross-contamination from previous feed loads occur.

At the farm, feed is usually stored in large bins outside livestock pens, feedlots, and poultry houses. Feed storage at the farm in unclean environments and in defective storage bins may introduce pathogens and/or propagate resident pathogens in the stored feed. Feed should be stored in closed bins that do not share common airspace with the livestock or poultry operations. All storage areas should be emptied and cleaned regularly according to type and condition of feed stored. It is important to keep the feed dry to prevent growth of contaminants such as Salmonella and E. coli O157:H7 that require moisture to multiply. Pathogens survive differently under various temperatures and water activities. In order to survive in feed, Salmonella, for instance, must combat the same environmental conditions as the nonpathogenic microflora. In 1978, Williams and Benson observed that low water activity (0.43) was not completely effective in destroying Salmonella populations in feed. In another study, Juven et al. (1984) demonstrated that the survival of Salmonella was greater at a water activity of 0.43 than at one of 0.75. Several investigators observed the survival and heat resistance of Salmonella in meat and bone meal, and in poultry feed, to be inversely proportional to moisture content and relative humidity but not to the type of protein in the feed or to organic versus conventional poultry feed (Liu et al., 1969; Carlson and Snoeyenbos, 1970; Juven et al., 1984; Ha et al., 1998; Petkar et al., 2011). Plant-based protein meals also do not appear to reduce colonization and shedding of Salmonella Heidelberg in broiler birds (Alali et al., 2011).

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Animal Feed Mill Biosecurity

Anne Huss , ... Cassie Jones , in Food and Feed Safety Systems and Analysis, 2018

Manufacture of Animal Feeds

In general, feed mills are responsible for the production of animal feeds, including those consumed by livestock and poultry animals and companion animals. For animal-based agriculture, manufactured feeds provide livestock and poultry animals with optimally formulated feeds to meet all nutrient requirements for optimal growth and performance. These manufactured feeds are specifically formulated to ensure that the animal receives optimal nutrients for each life stage. Optimal nutrition is important for preventing deficiencies, malnutrition, and disease. In addition to providing livestock animals with nutrient dense feeds, feed mills can also be responsible for the manufacture of pet foods for companion animals, including cats and dogs. Although the finished animal feeds can vary greatly between livestock and companion animals, most are generally produced from similar ingredients. These ingredients are derived from plant-based grains and animal-based cuts and by-products. To help ensure the safety of animal food from biological hazards, implementation of a feed mill biosecurity plan is essential.

The process of manufacturing feeds for food-producing animals can vary depending on the intended species, animal age, and animal management practice. Animal food can be fed to animals in the form of mash, crumbles, and pellets of various sizes. Most animal foods intended for livestock and poultry animals in a crumble or pellet form are processed via conditioning (with or without steam) and pelletization. Conditioning temperatures and times can vary. Pelleting can also result in the introduction of high temperatures, pressure, and shear forces.

Pet foods produced for companion animals are also produced in various forms, from kibbles to canned pates to jerky-type treats. Like the process of livestock feed manufacture, pet food kibbles are also conditioned with steam at high temperatures. Unlike livestock feeds, pet food kibbles and some treats are formed through extrusion. Extrusion can also exert a high temperature, high shear, and high pressure.

As for pet foods in canned or hermetically sealed packaging, manufacturers are required to follow the same guidelines as set forth for thermally processed low-acid foods packaged in hermetically sealed containers (21 CFR 113), used for regulation of food canned for human consumption. 21 CFR 113 sets-forth guidelines for production and process controls, including product preparation; establishment of scheduled processes; operations in the thermal processing room; and deviations in processing, venting, or control of critical factors.

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Temperature Modification for Insect Control

Ole Dosland , ... Rizana Mahroof , in Insect Management for Food Storage and Processing (Second Edition), 2006

Experiment II

The pilot feed mill was heated during August 6–8, 2001. The purpose of this experiment was to determine variations in temperature and relative humidity in different locations of the feed mill. Windows and doors of the mill were not sealed to prevent heat loss. In the feed mill, 10 locations among the basement and the four feed mill floors were selected to measure temperature and relative humidity changes. Locations 1 and 2 were in the basement; locations 3–5 were in the first floor; locations 6 and 7 were in the second floor; location 8 was in the third floor; and locations 9 and 10 were in the fourth floor.

Two HOBO data-logging units were placed in each feed mill location to measure temperature and relative humidity during the heat treatment. HOBO units were launched by a computer to record temperature and relative humidity at 15-min intervals. Temperature and relative humidity outdoors were measured by two HOBO units placed at ground level on the south side of the feed mill. Except for location 3, which was at the top of a hopper bin, all locations were at the floor level.

Five natural-gas heaters from Temp-Air (Burnsville, MN) were used to heat the feed mill. Each of the four heaters (THP-550) produced 550,000 BTU/hr (138,050 kcal/hr) and one heater (THP-1400) produced 1,400,000 BTU/hr (352,794 kcal/hr). The airflow rate of a THP-550 heater was 20.3 m3·min–1 (3,000 ft3·min–1) and that of a THP-1400 heater was 54.2 m3·min–1 (8,000 ft3·min–1). All heaters were placed outside the mill. These heaters bring in air through the burners and heat it to 60–82°C. Heat generated by the units was discharged into the mill floors by 50.8-cm-diameter nylon ductwork with 10-cm diameter openings at regular intervals. Ducts from the THP-550 units (one duct per heater) were placed in the basement and first floor, while ducts from the THP-1400 unit (two ducts per heater) were placed in the third floor. Theoretical engineering calculations, based on the airflow rate of the heaters and the volume of the facility, estimated that the air inside the feed mill was exchanged two to five times per hour, replacing ambient air with hot air during the heat treatment. Heaters were turned on at 8:00 p.m. (local time) on August 6 and turned off at 7:00 a.m. on August 8. Ten fans distributed heat in the first, second, and third floors. Of these, three were Bayley fans with a 50-cm blade diameter, producing an airflow rate of 48.1 m3·min–1 (7,100 ft3·min–1), and seven were Schaefer fans with a 90-cm blade diameter and an airflow rate of 311.3 m3·min–1 (11,000 ft3·min–1).

Temperature and relative humidity profiles

Starting temperatures at all feed mill locations ranged from 32 to 36°C. Typical temperature and relative humidity profiles observed during heat treatment at the 10 locations are shown in Figure 1. The temperature outdoors during the heat treatment was 23–28°C. The temperature in the southwest corner of the feed mill basement (location 2) never reached 50°C, and the maximum temperature attained there was 46°C (Table 5). Puddles of standing water near the southwest corner could have contributed to the slow heating of this area. In the same basement, temperatures in the northwest corner (location 1) reached 50°C in the shortest time (6 hr). This occurred because location 1 was close to a heating duct. The longest time (19 hr) taken to reach 50°C occurred in the southwest corner of the second floor (location 7). Heating ducts were not placed in the second floor, and heat distribution was primarily due to a chimney effect and air movement facilitated by fans. Temperatures above 50°C among mill locations were maintained for 18–31 hr, and the maximum temperatures attained ranged from 46 to 63°C. Temperatures exceeded 60°C in three of the 10 locations (1, 5, and 8). Heating rates among the feed mill floors ranged from 0.8 to 2.5 degrees C/hr.

Fig. 1. Observed temperature and relative humidity data at 10 locations during the August 6–8, 2001, gas heat treatment of the Kansas State University pilot feed mill. Two separate nonlinear regression models satisfactorily described these data. Top curves = temperature, bottom curves = relative humidity.

 (Reprinted, with permission, from Mahroof et al, 2003a)

TABLE 5. Temperature Changes at Pilot Feed Mill Locations During Gas Heat Treatment, August 6–8, 2001 a

Location Starting Temperature (°C) Time to 50°C (hr) Rate of Increase (degrees C/hr) b Time Above 50°C (hr) Maximum Temperature (°C)
1 34.9 6 2.5 31.3 62.7
2 31.5 … c … c … c 45.9
3 33.6 14.3 1.1 22.5 53.5
4 35.3 15 1 21.8 56
5 34.6 10.3 1.5 26.8 61.7
6 35.1 11.3 1.3 26.3 59.2
7 35.3 19.3 0.8 18.3 56
8 35.3 10.3 1.4 27.3 60.6
9 36.1 11 1.3 24 59.2
10 36.1 14.2 1 20.8 55.7
a
Source: Mahroof et al (2003a); used with permission from Elsevier.
b
(50°C – Starting temperature, °C)/Time to 50°C (hr).
c
Time to 50°C and time above 50°C could not be computed because temperature did not reach 50°C.

Outdoor relative humidity during the heat treatment ranged from 37 to 78%. Relative humidity at the beginning of the heat treatment among the feed mill locations was 34–58% (Table 6). The humidity levels observed during heat treatment were inversely related to temperature (Fig. 1). In the feed mill, the rate of decrease in humidity as the temperature climbed to 50°C was faster (3.9%/hr) in location 1 and slower (0.9%/hr) in locations 4, 7, and 10. Once the temperature reached 50°C, humidity in the feed mill stabilized around 19–21%, and the rate of change in humidity above 50°C was generally very small (0.02–0.2%/hr, Table 6).

TABLE 6. Relative Humidity Changes at Pilot Feed Mill Locations During Gas Heat Treatment, August 6–8, 2001 a

Location Starting Humidity (%) Rate of Decrease in Humidity Until 50°C (%/hr) b Mean ± SE Humidity (no. observations) c Rate of Decrease in Humidity After 50°C (%/hr) d
1 45.7 3.9 19.3 ± 0.1 (116) 0.1
2 57.7 … e 34.8 ± 1.4 f (141) … e
3 49.6 1.5 30.2 ± 0.5 (84) 0.6
4 38.1 0.9 20.2 ± 0.2 (80) 0.2
5 41 1.7 19.6 ± 0.2 (99) 0.2
6 39.6 1.4 19.7 ± 0.3 (96) 0.2
7 38.5 0.9 19.2 ± 0.04 (63) 0.1
8 40.3 1.6 19.6 ± 0.2 (99) 0.2
9 34.4 1.1 19.9 ± 0.2 (96) 0.1
10 37 0.9 20.1 ± 0.2 (83) 0.2
a
Source: Mahroof et al (2003a); used with permission from Elsevier.
b
(Starting humidity – humidity at 50°C)/Time to 50°C.
c
Mean ± standard error (SE) humidity values were calculated from observations starting at 50°C until the end of heat treatment.
d
(Humidity at 50°C – humidity at the end of heat treatment)/Time from 50°C until end of heat treatment.
e
Values could not be calculated because temperature did not reach 50°C.
f
The mean ± SE humidity value was calculated from observations collected throughout the heat treatment.

Norstein (1996) and Dowdy and Fields (2002) reported a similar decrease in relative humidity in flour mills during heat treatment. In the feed mill locations, a slight increase in humidity occurred soon after the heaters were turned on. Dowdy and Fields (2002) also observed a slight increase in humidity at the beginning of heat treatment. Moisture evaporating from flour in the boxes, grain dust, or hygroscopic surfaces in the mill may explain this small rise in humidity during the initial phase of the heat treatment.

Relative humidity may not play a significant role in insect mortality, although Denlinger and Yocum (1999) have suggested that rapid desiccation at high temperatures could contribute to heat-related mortality. High humidity (>60%) helps insect survival only if the temperature where insects are present is below 50°C (122°F). However, if temperatures at or above 50°C are maintained for several hours, insects can be killed even at high humidity levels (B. Subramanyam, unpublished data).

Practical conclusions from the experiment

This experiment showed that the stratification of temperatures during heat treatment resulted in different rates of heating among the feed mill floors. Horizontal and vertical stratification of temperatures, poor air movement, less than optimum placement of heaters or ducts carrying hot air, and loss of heat from various surfaces (windows, doors, floor, and roof vents) may have contributed to nonuniform heating observed in sample locations in the feed mill. Therefore, it is important to monitor temperatures regularly at several locations during heat treatment and take corrective action to redistribute heat from hotter to cooler areas of the mill by using additional heaters and/or fans.

Nonuniform distribution of heat within and among floors was also reported during heat treatment of a pet-food- processing facility (Dowdy, 1999), flour mills (Dean, 1911; Heaps and Black, 1994; Dowdy and Fields, 2002), and a feed mill (Roesli et al, 2003). Dean (1911) observed significant differences in the rate of heating of several flour mill floors and locations within the mill, such as elevator boots and roll stands. The temperature rise was faster at ≥1.5 m above the mill floor when compared with temperatures close to the floor. Dowdy and Fields (2002) reported differences within north and south corners of the second and third floors of the Kansas State University pilot flour mill subjected to a steam heat treatment during March 1998. In their study, the maximum temperatures attained ranged from 48 to 57°C, and the time to reach 47°C took 30–51 hr.

Although temperatures were above 60°C (140°F) in three feed mill locations, no adverse effects on structural integrity of the mill or functioning of mill equipment were observed after the heat treatment.

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Mycotoxin contamination of animal feed

H. Pettersson , in Animal Feed Contamination, 2012

11.7.2 Hazard analysis and critical control point (HACCP)and good manufacturing practice (GMP) at feed mills

For feed production in feed mills HACCP and GMP should be used to reduce the risks of mycotoxin contamination. The use of GMP and HACCP in feed quality assurance is described in more detail in Part VI of this volume.

General quality control and choice of feed ingredients are the first steps. Control analysis for certain mycotoxins in the ingredients may sometimes be a control point, especially for materials with a high risk of mycotoxin contamination. Purchase certificates on the absence of mycotoxins in bulk feed materials are more often required, thus forcing control analyses to be undertaken in the first stage of production. This control is especially important in the EU for AFB1 in dairy feed components. Analysis can be done of some selected mycotoxins in the finished compound feed, but this is more commonly done as random sampling.

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Management of Safety in the Feed Chain

Arnaud Bouxin , in Food Safety Management, 2014

Background

On 21 December 2010 a feed mill located in Niedersachsen detected contamination of compound feed for laying hens with dioxins above the maximum permitted levels as part of its own checks.

The German authorities having been informed by the company started investigations and discovered that a fat processor located in Schleswig-Holstein had purchased several consignments of fatty acids for the purpose of producing fat. This fat processor produced both feed fat and fat for industrial uses in separate lines. However, the processor subcontracted the production of feed fat containing the fatty acids to another fat processor located in Niedersachsen.

The fatty acids had been purchased from a biodiesel plant, from which the material was delivered directly to the fat processor in Niedersachsen, via a Dutch trader that handled both fat for the production of feed and fat for industrial uses. The fat processor in Niedersachsen subsequently used these fatty acids for the production of feed fat that was directly dispatched to several manufacturers of compound feed as feed fats.

The mixed fatty acids were confirmed to be contaminated by dioxins above the EU maximum permitted levels. The likely source of the contamination was the use of contaminated raw materials or technical processing aids for the production of biodiesel, which through the process were concentrated in the fatty acids.

Investigations from the authorities at the level of the two fat producers in Schleswig-Holstein and Niedersachsen led to the identification of eight deliveries of potentially contaminated fatty acids representing a volume of 206   t. These 206   t where mixed up with other fat products and sold as feed fats (2256   t) to 25 compound feed manufacturers. The compound feed was then delivered to almost 4500 farms that were subsequently blocked. Most compound feed was already used at the time of the blocking of the farms. Random testing of the samples of compound feed kept by the manufacturers showed levels of contamination below the maximum permitted for compound, which is logical given the low inclusion rates of feed fats in compound feed and the contamination load of the feed fats. Farms were unblocked based on a risk assessment including estimation of the theoretical highest contamination level of compound feed; further analysis was then performed. Only a few farms have shown results on eggs and pig lard above the maximum permitted levels for animal products.

The fat processor in Schleswig-Holstein benefited from a good reputation and was GMP+and QS certified; feed companies believed that this certificate also covered the activities of the Nierdersachsen plant.

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Practical Antimicrobial Therapeutics

In Veterinary Medicine (Eleventh Edition), 2017

Contamination of Feedstuffs

Antibiotic contamination of rations is a potential problem in feed mills that process medicated and nonmedicated feeds consecutively. The inadvertent feeding of antibiotics to cattle and horses can result in clinical disease, and the cause may not be immediately apparent to the investigating clinician. This can occur when cattle and horses are fed medicated pig feed, but may also occur when regular rations become contaminated with antibiotics. Residual carryover of medicated material into other feedstuffs can occur with feed mixers of various types and also via residues in conveyors, hoppers, and trucks. The risk for feedstuffs being contaminated can be quite high, and the most common contaminating drugs are chlortetracycline, sulfonamides, penicillin, and ionophores.

Within 24 hours of being fed medicated feed, dairy cattle show anorexia, rumen stasis, and subsequently pass custard-consistency feces containing undigested fiber. There is a precipitous fall in milk production. Dullness, muscle fasciculation, ketosis, hypocalcemia, and recumbency have also been observed. Affected cattle usually recover when placed on nonmedicated feed, but milk production may be adversely affected for the remainder of the lactation. Feeds contaminated with dimetridazole, lincomycin, and tylosin have been incriminated, although there is debate as to the role of tylosin in this syndrome. The carryover of medicated material into other feeds can also create violative tissue residues at slaughter. Sulfonamide contamination of swine rations is a particular problem.

The use of orally administered antimicrobial agents in horses over 3 months of age should be approached with great care. Their use can be followed by diarrhea, which is often intractable and results in chronic debilitation or death. Clindamycin and lincomycin carry a high risk and are probably totally contraindicated, and macrolides, tetracyclines, tylosin, and metronidazole are associated with risk in stressed horses.

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