Semester

Spring

Date of Graduation

2026

Document Type

Dissertation

Degree Type

PhD

College

Davis College of Agriculture, Natural Resources and Design

Department

Animal and Nutritional Sciences

Committee Chair

Joseph Moritz

Committee Member

Janet Tou

Committee Member

Jacek Jaczynski

Committee Member

Daniel Panaccione

Committee Member

Mark Lemons

Committee Member

Jon Ferrel

Abstract

In Chapter 2, an experiment was conducted to determine if the inclusion of 1.50% mixer-added water (MAW) and/or 0.25% Azomite® (AZM) would be suitable in alleviating concerns regarding pellet production rate and pellet quality when manufacturing feed with low-moisture corn. Furthermore, the authors aimed to determine if these additives had varying effects when utilizing different pellet die thicknesses. A 2 (Azomite; 0.00% or 0.25%) x 2 (mixer-added water; 0.00% or 1.50%) x 3 (pellet die thickness; 32 mm, 38 mm, or 45 mm) factorial arrangement was utilized to create the twelve experimental treatments, each manufactured in three randomized complete blocks. Responses included pellet production rate, pellet durability index tested for 30 and 60 seconds of pressure, hot pellet temperature, and feed moisture of the mixed mash, conditioned mash, cooled pellets, finished feed on the day of manufacture, and finished feed three days after manufacture. The interaction of Azomite and mixer-added water affected pellet production rate where the independent inclusion or either 0.25% Azomite or 1.50% mixer-added water increased pellet production rate by 8.4% relative to the control; however, the combination inclusion did not provide any added increase (P = 0.018). Azomite had no effect on pellet durability or hot pellet temperature, whereas increasing mixer-added water increased pellet durability and did not affect hot pellet temperature. Increasing pellet die thickness decreased production rate, increased pellet durability and increased hot pellet temperature. All main effects were concurrent with available literature. Including 1.50% mixer-added water also resulted in increased feed moisture throughout the manufacturing process and through three days of bagged storage. Overall, these data indicate that Azomite and mixer-added water may both be affecting feed additives in combating the negative effects low-moisture corn has on pellet production rate, and mixer-added water may increase pellet durability, both regardless of pellet die thickness. However, concerns remain regarding nutrient dilution, slips/plugs at the pellet die, and pathogenic microbial proliferation regarding the inclusion of mixer-added water.

In Chapter 3, a follow-up experiment to the one presented in Chapter 2 was conducted to evaluate the effect of Azomite, mixer-added water, and pellet die thickness on Ross 308 male broiler performance and bone mineralization from 7 to 21 days of age. Again, a 2 (Azomite; 0.00% or 0.25%) x 2 (mixer-added water; 0.00% or 1.50%) x 3 (pellet die thickness; 32 mm, 38 mm, 45 mm) factorial arrangement was utilized to create the twelve experimental treatments, and each was represented in the eight randomized complete blocks. All feed was sourced from the precious feed manufacturing experiment. Responses included feed intake per bird, live weight gain per bird, bird weight, mortality-corrected feed conversion ratio, tibia ash in mg of ash per chick, and mortality percentage. The three-way interaction of Azomite, mixer-added water, and pellet die thickness was observed the affect mortality-corrected feed conversion ratio where in including 1.50% mixer-added water to feed manufactured with no Azomite and the 45 mm pellet die thickness resulted in a 5-point increase; however, this relationship was not observed in the 32 or 38 mm pellet die thickness treatments (P = 0.049). Furthermore, the interaction of Azomite and mixer-added water also revealed that including 1.50% mixer-added water to feed manufactured with no Azomite increased feed intake by approximately 30 g, whereas the inclusion of Azomite, regardless of mixer-added water inclusion, returned intermediate results (P = 0.010). In conclusion, the addition of 0.25% Azomite may have decrease digesta passage rate, thus increasing nutrient absorption potential, the addition of 1.50% mixer-added water likely caused a simple nutrient dilution, resulting in increased feed intake and mortality corrected feed conversion ratio, and increasing pellet die thickness likely liberated otherwise inaccessible nutrients locked within the aleurone layer of the corn kernels. Therefore, previously explored concerns of mixer-added water diluting essential nutrients and affecting bird performance was confirmed in this experiment, and thus, mixer-added water may not be a suitable feed additive to improve feed manufacturing efficiency and efficacy if not properly removed in the cooling and drying process.

In Chapter 4, a second follow-up experiment to the one presented in Chapter 2 was conducted to evaluate the effect of mixer-added water and Azomite on mycotoxin production of inoculated feed stored under simulated summer and fall feed bin conditions for six days. A 2 (season; summer or fall) x 3 (dietary treatment; control, 1.50% mixer-added water, or 0.25% Azomite + 1.50% mixer-added water) factorial arrangement was utilized to create the six experimental treatments. All treatments were inoculated with aflatoxin producing A. flavus, replicated in six randomized complete blocks, and each response was measured on day 0 before inoculation, day 0 after inoculation, day 3 post-inoculation, and day 6 post-inoculation. Responses included total aflatoxin content, water activity, and A. flavus content in Log10 colony forming units per gram of feed. Preliminary examination of the data integrating the time points into the factorial arrangement revealed a two-way interaction season and time point that affected water activity (P =0.005). In this relationship water activity was similar across season and time point through day 3 post-inoculation, but on day 6 post-inoculation, the summer-stored feed had a decreased water activity compared to the fall-stored feed (0.557 vs. 0.617), likely due to the increase storage temperature causing increased free water evaporation. Next, the season x dietary treatment factorial arrangement was evaluated within each time point. On day 0 before inoculation the 1.50% mixer-added water dietary treatment had an increased water activity relative to the control feed (0.693 vs. 0.674; P = 0.029), whereas the 0.25% Azomite + 1.50% mixer-added water treatment had an intermediate level. This is likely due to the nature of the dietary treatments and water solubility of Azomite. No differences were observed in the responses on day 0 after inoculation, indicating an even starting point. On day 3 post-inoculation, while statistical differences were observed between the dietary treatments and were observed for total aflatoxin content, all values were well below the FDAs recommended action levels. Lastly, on day 6 post-inoculation, statistical differences were lost between dietary treatments for total aflatoxin content and again all values were well below the FDAs recommended action level. As previously described, simulated storage of feed in summer conditions resulted in decreased water activity relative to simulated fall conditions on day 6 post-inoculation. Overall, the addition of 1.50% mixer-added water to feed manufactured with low-moisture corn did not result in an increase in total aflatoxin content within 6 days of simulated feed storage. However, these findings should not be universally applied to larger applications of mixer-added water, higher-moisture ingredients, and feed stored for longer periods of time.

In Chapter 5, an experiment was conducted to model the effect of factors known to influence pellet die lubrication and pellet die scouring on feed manufacturing efficiency and efficacy. A blocked central composite design was selected for this experiment to allow for efficient and economical modeling of response curvature and higher-order interactions relative to traditional 3k factorial designs. The factors evaluated in this experiment included Azomite (0.00% to 0.50%), mixer-added fat (0.25% to 1.75%), dicalcium phosphate (0.00% to 1.90%), and conditioning temperature (68.33⁰C to 85.00⁰C), each with five, evenly spaced levels of examination. Responses measured included productive capacity (moisture corrected pellet production rate; 13.00% moisture), New Holmen pellet durability index, Pfost tumbling pellet durability index, modified Pfost tumbling pellet durability index, the percentage of pellets, hot pellet temperature, the change in feed temperature from pelleting, and moisture corrected bulk density (13.00% moisture). All responses were affected by one or more interactions of the tested factors, and because of this, each could not be briefly explored in a reasonably sized abstract. Therefore, brief conclusions will be drawn about each factor. Azomite was the second most effective pellet production aid per 0.25% increase in concentration: likely a function of its proposed die lubrication and scouring abilities; however, efficacy depends on the circumstances of the other diet components and processing parameters. Mixer-added fat was the third most effecting pellet production aid per 0.25% unit increase in concentration due to its well-appreciated lubrication properties. However, this comes to the detriment of pellet quality which may ultimately negate its overall positive influence. Dicalcium phosphate should not be considered a pellet production aid given its influence in the confines of this experiment. In many cases, increased DCP decreased or did not affect productive capacity. However, this conclusion should not be drawn for all inorganic phosphate sources without proper experimentation. Conditioning temperature was the most effective pellet production aid per 3.5⁰C increase (equates to 0.25% water addition), presumably due to lubrication. With that said and regardless of particle agglomeration potential, increasing CT did not always translate to improved pellet quality. Most likely this is a function of decreased die retention time and feed malleability between extrusion and cooling and drying. The resulting prediction equations from this experiment may help feed manufacturers and nutritionist best match feed processing parameters and techniques to individual diet formulation. Yet more research and modeling efforts are needed to most accurately prescribe processing parameters to maximize productive capacity and pellet quality.

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